githubmirror/sudo

docs/sudo_plugin.mdoc.in
4 920 строк122 KB
peppapig450
Fix typo: 'Please not report' → 'Please do not report' in documentation
28 апр 2025, 21:12
28 апр 2025, 21:12aa5d4b2
.\"
.\" SPDX-License-Identifier: ISC
.\"
.\" Copyright (c) 2009-2024 Todd C. Miller <Todd.Miller@sudo.ws>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.\"
.Dd August 14, 2024
.Dt SUDO_PLUGIN @mansectform@
.Os Sudo @PACKAGE_VERSION@
.Sh NAME
.Nm sudo_plugin
.Nd Sudo Plugin API
.Sh DESCRIPTION
Starting with version 1.8,
.Nm sudo
supports a plugin API
for policy and session logging.
Plugins may be compiled as dynamic shared objects (the default on
systems that support them) or compiled statically into the
.Nm sudo
binary itself.
By default, the
.Nm sudoers
plugin provides audit, security policy and I/O logging capabilities.
Via the plugin API,
.Nm sudo
can be configured to use alternate plugins provided by third parties.
The plugins to be used are specified in the
.Xr sudo.conf @mansectform@
file.
.Pp
The API is versioned with a major and minor number.
The minor version number is incremented when additions are made.
The major number is incremented when incompatible changes are made.
A plugin should be check the version passed to it and make sure that the
major version matches.
.Pp
The plugin API is defined by the
.In sudo_plugin.h
header file.
.Ss Policy plugin API
A policy plugin must declare and populate a
.Vt struct policy_plugin
in the global scope.
This structure contains pointers to the functions that implement the
.Nm sudo
policy checks.
The name of the symbol should be specified in
.Xr sudo.conf @mansectform@
along with a path to the plugin so that
.Nm sudo
can load it.
.Bd -literal
struct policy_plugin {
#define SUDO_POLICY_PLUGIN     1
    unsigned int type; /* always SUDO_POLICY_PLUGIN */
    unsigned int version; /* always SUDO_API_VERSION */
    int (*open)(unsigned int version, sudo_conv_t conversation,
        sudo_printf_t sudo_plugin_printf, char * const settings[],
        char * const user_info[], char * const user_env[],
        char * const plugin_options[], const char **errstr);
    void (*close)(int exit_status, int error);
    int (*show_version)(int verbose);
    int (*check_policy)(int argc, char * const argv[],
        char *env_add[], char **command_info[],
        char **argv_out[], char **user_env_out[], const char **errstr);
    int (*list)(int argc, char * const argv[], int verbose,
        const char *user, const char **errstr);
    int (*validate)(const char **errstr);
    void (*invalidate)(int rmcred);
    int (*init_session)(struct passwd *pwd, char **user_env[],
        const char **errstr);
    void (*register_hooks)(int version,
       int (*register_hook)(struct sudo_hook *hook));
    void (*deregister_hooks)(int version,
       int (*deregister_hook)(struct sudo_hook *hook));
    struct sudo_plugin_event * (*event_alloc)(void);
};
.Ed
.Pp
A
.Vt struct policy_plugin
has the following fields:
.Bl -tag -width 4n
.It Fa type
The
.Fa type
field should always be set to SUDO_POLICY_PLUGIN.
.It Fa version
The
.Fa version
field should be set to
.Dv SUDO_API_VERSION .
.Pp
This allows
.Nm sudo
to determine the API version the plugin was
built against.
.It Fa open
.Bd -literal -compact
int (*open)(unsigned int version, sudo_conv_t conversation,
    sudo_printf_t sudo_plugin_printf, char * const settings[],
    char * const user_info[], char * const user_env[],
    char * const plugin_options[], const char **errstr);
.Ed
.Pp
Returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error.
In the latter case,
.Nm sudo
will print a usage message before it exits.
If an error occurs, the plugin may optionally call the
.Fn conversation
or
.Fn sudo_plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa version
The version passed in by
.Nm sudo
allows the plugin to determine the
major and minor version number of the plugin API supported by
.Nm sudo .
.It Fa conversation
A pointer to the
.Fn conversation
function that can be used by the plugin to interact with the user (see
.Sx Conversation API
for details).
Returns 0 on success and \-1 on failure.
.It Fa sudo_plugin_printf
A pointer to a
.Fn printf Ns -style
function that may be used to display informational or error messages (see
.Sx Conversation API
for details).
Returns the number of characters printed on success and \-1 on failure.
.It Fa settings
A vector of user-supplied
.Nm sudo
settings in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
These settings correspond to options the user specified when running
.Nm sudo .
As such, they will only be present when the corresponding option has
been specified on the command line.
.Pp
When parsing
.Fa settings ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one itself but the
.Em value
might.
.Pp
The following values may be set by
.Nm sudo :
.Bl -tag -width 4n
.It bsdauth_type=string
Authentication type, if specified by the
.Fl a
option, to use on
systems where
.Bx
authentication is supported.
.It closefrom=number
If specified, the user has requested via the
.Fl C
option that
.Nm sudo
close all files descriptors with a value of
.Em number
or higher.
The plugin may optionally pass this, or another value, back in the
.Fa command_info
list.
.It cmnd_chroot=string
The root directory (see
.Xr chroot 2 )
to run the command in, as specified by the user via the
.Fl R
option.
The plugin may ignore or restrict the user's ability to specify a new
root directory.
Only available starting with API version 1.16.
.It cmnd_cwd=string
The working directory to run the command in, as specified by the user via the
.Fl D
option.
The plugin may ignore or restrict the user's ability to specify a new
working directory.
Only available starting with API version 1.16.
.It debug_flags=string
A debug file path name followed by a space and a comma-separated
list of debug flags that correspond to the plugin's
.Em Debug
entry in
.Xr sudo.conf @mansectform@ ,
if there is one.
The flags are passed to the plugin exactly as they appear in
.Xr sudo.conf @mansectform@ .
The syntax used by
.Nm sudo
and the
.Nm sudoers
plugin is
.Em subsystem Ns @ Ns Em priority
but a plugin is free to use a different
format so long as it does not include a comma
.Pq Ql ,\& .
Prior to
.Nm sudo
1.8.12, there was no way to specify plugin-specific
.Em debug_flags
so the value was always the same as that used by the
.Nm sudo
front-end and did not include a path name, only the flags themselves.
As of version 1.7 of the plugin interface,
.Nm sudo
will only pass
.Em debug_flags
if
.Xr sudo.conf @mansectform@
contains a plugin-specific
.Em Debug
entry.
.It ignore_ticket=bool
Set to true if the user specified the
.Fl k
option along with a
command, indicating that the user wishes to ignore any cached
authentication credentials.
.Em implied_shell
to true.
This allows
.Nm sudo
with no arguments
to be used similarly to
.Xr su 1 .
If the plugin does not to support this usage, it may return a value of \-2
from the
.Fn check_policy
function, which will cause
.Nm sudo
to print a usage message and exit.
.It implied_shell=bool
If the user does not specify a program on the command line,
.Nm sudo
will pass the plugin the path to the user's shell and set
.Em implied_shell .
.It intercept_ptrace=bool
Indicates whether or not the system supports intercept
mode using
.Xr ptrace 2 .
This is currently only true for Linux systems that support
.Xr seccomp 2
filtering and the
.Dq trap
action.
Other systems will use a dynamic shared object to implement
intercept.
Only available starting with API version 1.19.
.It intercept_setid=bool
Indicates whether or not the system supports running set-user-ID
and set-group-ID binaries in intercept mode.
This is currently only true for Linux systems that support
.Xr seccomp 2
filtering and the
.Dq trap
action.
On systems that use a dynamic shared object to implement
intercept, the dynamic linker (ld.so or the equivalent)
will disable preloading of shared objects when executing a
set-user-ID or set-group-ID binary.
This will disable intercept mode for that program and any other
programs that it executes.
The policy plugin may refuse to execute a set-user-ID or set-group-ID
binary in intercept mode to avoid this.
Only available starting with API version 1.19.
.It login_class=string
.Bx
login class to use when setting resource limits and nice value,
if specified by the
.Fl c
option.
.It login_shell=bool
Set to true if the user specified the
.Fl i
option, indicating that
the user wishes to run a login shell.
.It max_groups=int
The maximum number of groups a user may belong to.
This will only be present if there is a corresponding setting in
.Xr sudo.conf @mansectform@ .
.It network_addrs=list
A space-separated list of IP network addresses and netmasks in the
form
.Dq addr/netmask ,
e.g.,
.Dq 192.168.1.2/255.255.255.0 .
The address and netmask pairs may be either IPv4 or IPv6, depending on
what the operating system supports.
If the address contains a colon
.Pq Ql :\& ,
it is an IPv6 address, else it is IPv4.
.It noninteractive=bool
Set to true if the user specified the
.Fl n
option, indicating that
.Nm sudo
should operate in non-interactive mode.
The plugin may reject a command run in non-interactive mode if user
interaction is required.
.It plugin_dir=string
The default plugin directory used by the
.Nm sudo
front-end.
This is the default directory set at compile time and may not
correspond to the directory the running plugin was loaded from.
It may be used by a plugin to locate support files.
.It plugin_path=string
The path name of plugin loaded by the
.Nm sudo
front-end.
The path name will be a fully-qualified unless the plugin was
statically compiled into
.Nm sudo .
.It preserve_environment=bool
Set to true if the user specified the
.Fl E
option, indicating that
the user wishes to preserve the environment.
.It preserve_groups=bool
Set to true if the user specified the
.Fl P
option, indicating that
the user wishes to preserve the group vector instead of setting it
based on the runas user.
.It progname=string
The command name that sudo was run as, typically
.Dq sudo
or
.Dq sudoedit .
.It prompt=string
The prompt to use when requesting a password, if specified via
the
.Fl p
option.
.It remote_host=string
The name of the remote host to run the command on, if specified via
the
.Fl h
option.
Support for running the command on a remote host is meant to be implemented
via a helper program that is executed in place of the user-specified command.
The
.Nm sudo
front-end is only capable of executing commands on the local host.
Only available starting with API version 1.4.
.It run_shell=bool
Set to true if the user specified the
.Fl s
option, indicating that the user wishes to run a shell.
.It runas_group=string
The group name or group-ID to run the command as, if specified via
the
.Fl g
option.
.It runas_user=string
The user name or user-ID to run the command as, if specified via the
.Fl u
option.
.It selinux_role=string
SELinux role to use when executing the command, if specified by
the
.Fl r
option.
.It selinux_type=string
SELinux type to use when executing the command, if specified by
the
.Fl t
option.
.It set_home=bool
Set to true if the user specified the
.Fl H
option.
If true, set the
.Ev HOME
environment variable to the target user's home directory.
.It sudoedit=bool
Set to true when the
.Fl e
option is specified or if invoked as
.Nm sudoedit .
The plugin shall substitute an editor into
.Fa argv
in the
.Fn check_policy
function or return \-2 with a usage error
if the plugin does not support
.Em sudoedit .
For more information, see the
.Fn check_policy
section.
.It timeout=string
Command timeout specified by the user via the
.Fl T
option.
Not all plugins support command timeouts and the ability of the
user to set a timeout may be restricted by policy.
The format of the timeout string is plugin-specific.
.It update_ticket=bool
Set to false if the user specified the
.Fl N
option, indicating that the user wishes to avoid updating any cached
authentication credentials.
Only available starting with API version 1.20.
.El
.Pp
Additional settings may be added in the future so the plugin should
silently ignore settings that it does not recognize.
.It Fa user_info
A vector of information about the user running the command in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa user_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
The following values may be set by
.Nm sudo :
.Bl -tag -width 4n
.It cols=int
The number of columns the user's terminal supports.
If there is no terminal device available, a default value of 80 is used.
.It cwd=string
The user's current working directory.
.It egid=gid_t
The effective group-ID of the user invoking
.Nm sudo .
.It euid=uid_t
The effective user-ID of the user invoking
.Nm sudo .
.It gid=gid_t
The real group-ID of the user invoking
.Nm sudo .
.It groups=list
The user's supplementary group list formatted as a string of
comma-separated group-IDs.
.It host=string
The local machine's hostname as returned by the
.Xr gethostname 2
system call.
.It lines=int
The number of lines the user's terminal supports.
If there is
no terminal device available, a default value of 24 is used.
.It pgid=int
The ID of the process group that the running
.Nm sudo
process is a member of.
Only available starting with API version 1.2.
.It pid=int
The process ID of the running
.Nm sudo
process.
Only available starting with API version 1.2.
.It ppid=int
The parent process ID of the running
.Nm sudo
process.
Only available starting with API version 1.2.
.It rlimit_as=soft,hard
The maximum size to which the process's address space may grow (in bytes),
if supported by the operating system.
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_core=soft,hard
The largest size core dump file that may be created (in bytes).
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_cpu=soft,hard
The maximum amount of CPU time that the process may use (in seconds).
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_data=soft,hard
The maximum size of the data segment for the process (in bytes).
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_fsize=soft,hard
The largest size file that the process may create (in bytes).
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_locks=soft,hard
The maximum number of locks that the process may establish,
if supported by the operating system.
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_memlock=soft,hard
The maximum size that the process may lock in memory (in bytes),
if supported by the operating system.
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_nofile=soft,hard
The maximum number of files that the process may have open.
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_nproc=soft,hard
The maximum number of processes that the user may run simultaneously.
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_rss=soft,hard
The maximum size to which the process's resident set size may grow (in bytes).
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It rlimit_stack=soft,hard
The maximum size to which the process's stack may grow (in bytes).
The soft and hard limits are separated by a comma.
A value of
.Dq infinity
indicates that there is no limit.
Only available starting with API version 1.16.
.It sid=int
The session ID of the running
.Nm sudo
process or 0 if
.Nm sudo
is not part of a POSIX job control session.
Only available starting with API version 1.2.
.It tcpgid=int
The ID of the foreground process group associated with the terminal
device associated with the
.Nm sudo
process or 0 if there is no terminal present.
Only available starting with API version 1.2.
.It tty=string
The path to the user's terminal device, if one exists.
This entry is only present if the user has a terminal device
associated with the session.
.It ttydev=dev_t
The number of the user's terminal device, if one exists,
formatted as a
.Vt long long
value.
This entry is only present if the user has a terminal device
associated with the session.
Only available starting with API version 1.22.
.It uid=uid_t
The real user-ID of the user invoking
.Nm sudo .
.It umask=octal
The invoking user's file creation mask.
Only available starting with API version 1.10.
.It user=string
The name of the user invoking
.Nm sudo .
.El
.It Fa user_env
The user's environment in the form of a
.Dv NULL Ns -terminated vector of
.Dq name=value
strings.
.Pp
When parsing
.Fa user_env ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.It Fa plugin_options
Any (non-comment) strings immediately after the plugin path are
passed as arguments to the plugin.
These arguments are split on a white space boundary and are passed to
the plugin in the form of a
.Dv NULL Ns -terminated
array of strings.
If no arguments were
specified,
.Fa plugin_options
will be the
.Dv NULL
pointer.
.Pp
The
.Fa plugin_options
parameter is only available starting with
API version 1.2.
A plugin
.Sy must
check the API version specified
by the
.Nm sudo
front-end before using
.Fa plugin_options .
Failure to do so may result in a crash.
.It Fa errstr
If the
.Fn open
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa close
.Bd -literal -compact
void (*close)(int exit_status, int error);
.Ed
.Pp
The
.Fn close
function is called when
.Nm sudo
is finished, shortly before it exits.
Starting with API version 1.15,
.Fn close
is called regardless of whether or not a command was actually executed.
This makes it possible for plugins to perform cleanup even when a
command was not run.
It is not possible to tell whether a command was run based solely
on the arguments passed to the
.Fn close
function.
To determine if a command was actually run,
the plugin must keep track of whether or not the
.Fn check_policy
function returned successfully.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa exit_status
The command's exit status, as returned by the
.Xr wait 2
system call, or zero if no command was run.
The value of
.Fa exit_status
is undefined if
.Fa error
is non-zero.
.It Fa error
If the command could not be executed, this is set to the value of
.Va errno
set by the
.Xr execve 2
system call.
The plugin is responsible for displaying error information via the
.Fn conversation
or
.Fn sudo_plugin_printf
function.
If the command was successfully executed, the value of
.Fa error
is zero.
.El
.Pp
If no
.Fn close
function is defined, no I/O logging plugins are loaded,
and neither the
.Em timeout
nor
.Em use_pty
options are set in the
.Fa command_info
list, the
.Nm sudo
front-end may execute the command directly instead of running
it as a child process.
.It Fa show_version
.Bd -literal -compact
int (*show_version)(int verbose);
.Ed
.Pp
The
.Fn show_version
function is called by
.Nm sudo
when the user specifies the
.Fl V
option.
The plugin may display its version information to the user via the
.Fn conversation
or
.Fn sudo_plugin_printf
function using
.Dv SUDO_CONV_INFO_MSG .
If the user requests detailed version information, the
.Fa verbose
flag will be non-zero.
.Pp
Returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error, although the return value is currently
ignored.
.It Fa check_policy
.Bd -literal -compact
int (*check_policy)(int argc, char * const argv[], char *env_add[],
    char **command_info[], char **argv_out[], char **user_env_out[],
    const char **errstr);
.Ed
.Pp
The
.Fn check_policy
function is called by
.Nm sudo
to determine
whether the user is allowed to run the specified commands.
.Pp
If the
.Em sudoedit
option was enabled in the
.Fa settings
array passed to the
.Fn open
function, the user has requested
.Em sudoedit
mode.
.Em sudoedit
is a mechanism for editing one or more files
where an editor is run with the user's credentials instead of with
elevated privileges.
.Nm sudo
achieves this by creating user-writable
temporary copies of the files to be edited and then overwriting the
originals with the temporary copies after editing is complete.
If the plugin supports
.Em sudoedit ,
it must set
.Em sudoedit=true
in the
.Fa command_info
list.
The plugin is responsible for choosing the editor to be used,
potentially from a variable in the user's environment, such as
.Ev EDITOR ,
and should be stored in
.Fa argv_out
(environment variables may include command line options).
The files to be edited should be copied from
.Fa argv
to
.Fa argv_out ,
separated from the
editor and its arguments by a
.Ql --
element.
The
.Ql --
will be removed by
.Nm sudo
before the editor is executed.
The plugin may also set
.Em sudoedit_nfiles
to the number of files to be edited in the
.Fa command_info
list; this will only be used by the
.Nm sudo
front-end starting with API version 1.21.
.Pp
The
.Fn check_policy
function returns 1 if the command is allowed,
0 if not allowed, \-1 for a general error, or \-2 for a usage error
or if
.Em sudoedit
was specified but is unsupported by the plugin.
In the latter case,
.Nm sudo
will print a usage message before it
exits.
If an error occurs, the plugin may optionally call the
.Fn conversation
or
.Fn sudo_plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa argc
The number of elements in
.Fa argv ,
not counting the final
.Dv NULL
pointer.
.It Fa argv
The argument vector describing the command the user wishes to run,
in the same form as what would be passed to the
.Xr execve 2
system call.
The vector is terminated by a
.Dv NULL
pointer.
.It Fa env_add
Additional environment variables specified by the user on the command
line in the form of a
.Dv NULL Ns -terminated
vector of
.Dq name=value
strings.
The plugin may reject the command if one or more variables
are not allowed to be set, or it may silently ignore such variables.
.Pp
When parsing
.Fa env_add ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one itself but the
.Em value
might.
.It Fa command_info
Information about the command being run in the form of
.Dq name=value
strings.
These values are used by
.Nm sudo
to set the execution environment when running a command.
The plugin is responsible for creating and populating the vector,
which must be terminated with a
.Dv NULL
pointer.
The following values are recognized by
.Nm sudo :
.Bl -tag -width 4n
.It apparmor_profile=string
AppArmor profile to transition to when executing the command.
Only available starting with API version 1.19.
.It chroot=string
The root directory to use when running the command.
.It closefrom=number
If specified,
.Nm sudo
will close all files descriptors with a value
of
.Em number
or higher.
.It command=string
Fully qualified path to the command to be executed.
.It cwd=string
The current working directory to change to when executing the command.
If
.Nm sudo
is unable to change to the new working directory, the command will
not be run unless
.Em cwd_optional
is also set (see below).
.It cwd_optional=bool
If set,
.Nm sudo
will treat an inability to change to the new working directory as a
non-fatal error.
This setting has no effect unless
.Em cwd
is also set.
.It exec_background=bool
By default,
.Nm sudo
runs a command as the foreground process as long as
.Nm sudo
itself is running in the foreground.
When
.Em exec_background
is enabled and the command is being run in a pseudo-terminal
(due to I/O logging or the
.Em use_pty
setting), the command will be run as a background process.
Attempts to read from the controlling terminal (or to change terminal
settings) will result in the command being suspended with the
.Dv SIGTTIN
signal (or
.Dv SIGTTOU
in the case of terminal settings).
If this happens when
.Nm sudo
is a foreground process, the command will be granted the controlling terminal
and resumed in the foreground with no user intervention required.
The advantage of initially running the command in the background is that
.Nm sudo
need not read from the terminal unless the command explicitly requests it.
Otherwise, any terminal input must be passed to the command, whether it
has required it or not (the kernel buffers terminals so it is not possible
to tell whether the command really wants the input).
This is different from historic
.Nm sudo
behavior or when the command is not being run in a pseudo-terminal.
.Pp
For this to work seamlessly, the operating system must support the
automatic restarting of system calls.
Unfortunately, not all operating systems do this by default,
and even those that do may have bugs.
For example, macOS fails to restart the
.Fn tcgetattr
and
.Fn tcsetattr
system calls (this is a bug in macOS).
Furthermore, because this behavior depends on the command stopping with the
.Dv SIGTTIN
or
.Dv SIGTTOU
signals, programs that catch these signals and suspend themselves
with a different signal (usually
.Dv SIGTOP )
will not be automatically foregrounded.
Some versions of the linux
.Xr su 1
command behave this way.
Because of this, a plugin should not set
.Em exec_background
unless it is explicitly enabled by the administrator and there should
be a way to enabled or disable it on a per-command basis.
.Pp
This setting has no effect unless I/O logging is enabled or
.Em use_pty
is enabled.
.It execfd=number
If specified,
.Nm sudo
will use the
.Xr fexecve 2
system call to execute the command instead of
.Xr execve 2 .
The specified
.Em number
must refer to an open file descriptor.
.It intercept=bool
If set,
.Nm sudo
will intercept attempts to execute a subsequent command and perform
a policy check via the policy plugin's
.Fn check_policy
function to determine whether or not the command is permitted.
This can be used to prevent shell escapes on supported platforms
but it has a number of limitations.
See
.Sy Preventing shell escapes
in
.Xr sudoers @mansectform@
for details.
Only available starting with API version 1.18.
.It intercept_verify=bool
If set,
.Nm sudo
will attempt to verify that a command run in intercept mode has the
expected path name, command line arguments and environment.
This setting has no effect unless
.Em use_ptrace
is also enabled.
Only available starting with API version 1.20.
.It iolog_compress=bool
Set to true if the I/O logging plugins, if any, should compress the
log data.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_group=string
The group that will own newly created I/O log files and directories.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_mode=octal
The file permission mode to use when creating I/O log files and directories.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_user=string
The user that will own newly created I/O log files and directories.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_path=string
Fully qualified path to the file or directory in which I/O log is
to be stored.
This is a hint to the I/O logging plugin which may choose to ignore it.
If no I/O logging plugin is loaded, this setting has no effect.
.It iolog_stdin=bool
Set to true if the I/O logging plugins, if any, should log the
standard input if it is not connected to a terminal device.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_stdout=bool
Set to true if the I/O logging plugins, if any, should log the
standard output if it is not connected to a terminal device.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_stderr=bool
Set to true if the I/O logging plugins, if any, should log the
standard error if it is not connected to a terminal device.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_ttyin=bool
Set to true if the I/O logging plugins, if any, should log all
terminal input.
This only includes input typed by the user and not from a pipe or
redirected from a file.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It iolog_ttyout=bool
Set to true if the I/O logging plugins, if any, should log all
terminal output.
This only includes output to the screen, not output to a pipe or file.
This is a hint to the I/O logging plugin which may choose to ignore it.
.It login_class=string
.Bx
login class to use when setting resource limits and nice value (optional).
This option is only set on systems that support login classes.
.It nice=int
Nice value (priority) to use when executing the command.
The nice value, if specified, overrides the priority associated with the
.Em login_class
on
.Bx
systems.
.It log_subcmds=bool
If set,
.Nm sudo
will call the audit plugin's
.Fn accept
function to log when the command runs a subsequent command, if supported
by the system.
If
.Em intercept
is also specified,
.Em log_subcmds
will be ignored.
See
.Sy Preventing shell escapes
in
.Xr sudoers @mansectform@
for more information.
Only available starting with API version 1.18.
.It noexec=bool
If set, prevent the command from executing other programs.
.It preserve_fds=list
A comma-separated list of file descriptors that should be
preserved, regardless of the value of the
.Em closefrom
setting.
Only available starting with API version 1.5.
.It preserve_groups=bool
If set,
.Nm sudo
will preserve the user's group vector instead of
initializing the group vector based on
.Em runas_user .
.It rlimit_as=soft,hard
The maximum size to which the process's address space may grow (in bytes),
if supported by the operating system.
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_core=soft,hard
The largest size core dump file that may be created (in bytes).
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_cpu=soft,hard
The maximum amount of CPU time that the process may use (in seconds).
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_data=soft,hard
The maximum size of the data segment for the process (in bytes).
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_fsize=soft,hard
The largest size file that the process may create (in bytes).
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_locks=soft,hard
The maximum number of locks that the process may establish,
if supported by the operating system.
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_memlock=soft,hard
The maximum size that the process may lock in memory (in bytes),
if supported by the operating system.
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_nofile=soft,hard
The maximum number of files that the process may have open.
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_nproc=soft,hard
The maximum number of processes that the user may run simultaneously.
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_rss=soft,hard
The maximum size to which the process's resident set size may grow (in bytes).
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It rlimit_stack=soft,hard
The maximum size to which the process's stack may grow (in bytes).
The soft and hard limits are separated by a comma.
If only a single value is specified, both the hard and soft limits are set.
A value of
.Dq infinity
indicates that there is no limit.
A value of
.Dq user
will cause the invoking user's resource limit to be preserved.
A value of
.Dq default
will cause the target user's default resource limit to be used
on systems that allow per-user resource limits to be configured.
Only available starting with API version 1.18.
.It runas_egid=gid
Effective group-ID to run the command as.
If not specified, the value of
.Em runas_gid
is used.
.It runas_euid=uid
Effective user-ID to run the command as.
If not specified, the value of
.Em runas_uid
is used.
.It runas_gid=gid
Group-ID to run the command as.
.It runas_group=string
The name of the group the command will run as, if it is different
from the
.Em runas_user Ns 's
default group.
This value is provided for auditing purposes only, the
.Nm sudo
front-end uses
.Em runas_egid
and
.Em runas_gid
when executing the command.
.It runas_groups=list
The supplementary group vector to use for the command in the form
of a comma-separated list of group-IDs.
If
.Em preserve_groups
is set, this option is ignored.
.It runas_uid=uid
User-ID to run the command as.
.It runas_user=string
The name of the user the command will run as, which should correspond to
.Em runas_euid
(or
.Em runas_uid
if
.Em runas_euid
is not set).
This value is provided for auditing purposes only, the
.Nm sudo
front-end uses
.Em runas_euid
and
.Em runas_uid
when executing the command.
.It selinux_role=string
SELinux role to use when executing the command.
.It selinux_type=string
SELinux type to use when executing the command.
.It set_utmp=bool
Create a utmp (or utmpx) entry when a pseudo-terminal is allocated.
By default, the new entry will be a copy of the user's existing utmp
entry (if any), with the tty, time, type, and pid fields updated.
.It sudoedit=bool
Set to true when in
.Em sudoedit
mode.
The plugin may enable
.Em sudoedit
mode even if
.Nm sudo
was not invoked as
.Nm sudoedit .
This allows the plugin to perform command substitution and transparently
enable
.Em sudoedit
when the user attempts to run an editor.
.It sudoedit_checkdir=bool
Set to false to disable directory writability checks in
.Nm sudoedit .
By default,
.Nm sudoedit
1.8.16 and higher will check all directory components of the path to be
edited for writability by the invoking user.
Symbolic links will not be followed in writable directories and
.Nm sudoedit
will refuse to edit a file located in a writable directory.
These restrictions are not enforced when
.Nm sudoedit
is run by root.
The
.Em sudoedit_checkdir
option can be set to false to disable this check.
Only available starting with API version 1.8.
.It sudoedit_follow=bool
Set to true to allow
.Nm sudoedit
to edit files that are symbolic links.
By default,
.Nm sudoedit
1.8.15 and higher will refuse to open a symbolic link.
The
.Em sudoedit_follow
option can be used to restore the older behavior and allow
.Nm sudoedit
to open symbolic links.
Only available starting with API version 1.8.
.It sudoedit_nfiles=number
The number of files to be edited by the user.
If present, this is will be used by the
.Nm sudo
front-end to determine which elements of the
.Fa argv_out
vector are files to be edited.
The
.Ql --
element must immediately precede the first file to be edited.
If
.Em sudoedit_nfiles
is not specified, the
.Nm sudo
front-end will use the position of the
.Ql --
element to determine where the file list begins.
Only available starting with API version 1.21.
.It timeout=int
Command timeout.
If non-zero then when the timeout expires the command will be killed.
.It umask=octal
The file creation mask to use when executing the command.
This value may be overridden by PAM or login.conf on some systems
unless the
.Em umask_override
option is also set.
.It umask_override=bool
Force the value specified by the
.Em umask
option to override any umask set by PAM or login.conf.
.It use_ptrace=bool
If set,
.Nm sudo
will use
.Xr ptrace 2
to implement intercept mode if supported by the system.
This setting has no effect unless
.Em intercept
is also set.
Only available starting with API version 1.19.
.It use_pty=bool
Allocate a pseudo-terminal to run the command in, regardless of whether
or not I/O logging is in use.
By default,
.Nm sudo
will only run
the command in a pseudo-terminal when an I/O log plugin is loaded.
.It utmp_user=string
User name to use when constructing a new utmp (or utmpx) entry when
.Em set_utmp
is enabled.
This option can be used to set the user field in the utmp entry to
the user the command runs as rather than the invoking user.
If not set,
.Nm sudo
will base the new entry on
the invoking user's existing entry.
.El
.Pp
Unsupported values will be ignored.
.It Fa argv_out
The
.Dv NULL Ns -terminated
argument vector to pass to the
.Xr execve 2
system call when executing the command.
The plugin is responsible for allocating and populating the vector.
.It Fa user_env_out
The
.Dv NULL Ns -terminated
environment vector to use when executing the command.
The plugin is responsible for allocating and populating the vector.
.It Fa errstr
If the
.Fn check_policy
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa list
.Bd -literal -compact
int (*list)(int argc, char * const argv[], int verbose,
    const char *user, const char **errstr);
.Ed
.Pp
List available privileges for the invoking user.
Returns 1 on success, 0 on failure, and \-1 on error.
On error, the plugin may optionally call the
.Fn conversation
or
.Fn sudo_plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to
the user.
.Pp
Privileges should be output via the
.Fn conversation
or
.Fn sudo_plugin_printf
function using
.Dv SUDO_CONV_INFO_MSG .
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa argc
The number of elements in
.Fa argv ,
not counting the final
.Dv NULL
pointer.
.It Fa argv
If
.No non- Ns Dv NULL ,
an argument vector describing a command the user
wishes to check against the policy in the same form as what would
be passed to the
.Xr execve 2
system call.
If the command is permitted by the policy, the fully-qualified path
to the command should be displayed along with any command line arguments.
.It Fa verbose
Flag indicating whether to list in verbose mode or not.
.It Fa user
The name of a different user to list privileges for if the policy
allows it.
If
.Dv NULL ,
the plugin should list the privileges of the invoking user.
.It Fa errstr
If the
.Fn list
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa validate
.Bd -literal -compact
int (*validate)(const char **errstr);
.Ed
.Pp
The
.Fn validate
function is called when
.Nm sudo
is run with the
.Fl v
option.
For policy plugins such as
.Nm sudoers
that cache
authentication credentials, this function will validate and cache
the credentials.
.Pp
The
.Fn validate
function should be
.Dv NULL
if the plugin does not support credential caching.
.Pp
Returns 1 on success, 0 on failure, and \-1 on error.
On error, the plugin may optionally call the
.Fn conversation
or
.Fn sudo_plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional
error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Va errstr
If the
.Fn validate
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa invalidate
.Bd -literal -compact
void (*invalidate)(int rmcred);
.Ed
.Pp
The
.Fn invalidate
function is called when
.Nm sudo
is run with the
.Fl k
or
.Fl K
option.
For policy plugins such as
.Nm sudoers
that
cache authentication credentials, this function will invalidate the
credentials.
If the
.Fa rmcred
flag is non-zero, the plugin may remove
the credentials instead of simply invalidating them.
.Pp
The
.Fn invalidate
function should be
.Dv NULL
if the plugin does not support credential caching.
.It Fa init_session
.Bd -literal -compact
int (*init_session)(struct passwd *pwd, char **user_env[],
    const char **errstr);
.Ed
.Pp
The
.Fn init_session
function is called before
.Nm sudo
sets up the
execution environment for the command.
It is run in the parent
.Nm sudo
process before any user-ID or group-ID changes.
This can be used to perform session setup that is not supported by
.Fa command_info ,
such as opening the PAM session.
The
.Fn close
function can be
used to tear down the session that was opened by
.Fn init_session .
.Pp
Returns 1 on success, 0 on failure, and \-1 on error.
On error, the plugin may optionally call the
.Fn conversation
or
.Fn sudo_plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional
error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa pwd
If the user-ID the command will run as was found in the password database,
.Fa pwd
will describe that user, otherwise it will be
.Dv NULL .
.It Fa user_env_out
The
.Dv NULL Ns -terminated
environment vector to use when executing the command.
This is the same string passed back to the front-end via the Policy Plugin's
.Fa user_env_out
parameter.
If the
.Fn init_session
function needs to modify the user environment, it should update the
pointer stored in
.Fa user_env_out .
The expected use case is to merge the contents of the PAM environment
(if any) with the contents of
.Fa user_env_out .
The
.Fa user_env_out
parameter is only available
starting with API version 1.2.
A plugin
.Sy must
check the API
version specified by the
.Nm sudo
front-end before using
.Fa user_env_out .
Failure to do so may result in a crash.
.It Fa errstr
If the
.Fn init_session
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa register_hooks
.Bd -literal -compact
void (*register_hooks)(int version,
   int (*register_hook)(struct sudo_hook *hook));
.Ed
.Pp
The
.Fn register_hooks
function is called by the sudo front-end to
register any hooks the plugin needs.
If the plugin does not support hooks,
.Fa register_hooks
should be set to the
.Dv NULL
pointer.
.Pp
The
.Fa version
argument describes the version of the hooks API
supported by the
.Nm sudo
front-end.
.Pp
The
.Fn register_hook
function should be used to register any supported
hooks the plugin needs.
It returns 0 on success, 1 if the hook type is not supported, and \-1
if the major version in
.Vt struct sudo_hook
does not match the front-end's major hook API version.
.Pp
See the
.Sx Hook function API
section below for more information about hooks.
.Pp
The
.Fn register_hooks
function is only available starting
with API version 1.2.
If the
.Nm sudo
front-end doesn't support API
version 1.2 or higher,
.Fn register_hooks
will not be called.
.It Fa deregister_hooks
.Bd -literal -compact
void (*deregister_hooks)(int version,
   int (*deregister_hook)(struct sudo_hook *hook));
.Ed
.Pp
The
.Fn deregister_hooks
function is called by the sudo front-end
to deregister any hooks the plugin has registered.
If the plugin does not support hooks,
.Fa deregister_hooks
should be set to the
.Dv NULL
pointer.
.Pp
The
.Fa version
argument describes the version of the hooks API
supported by the
.Nm sudo
front-end.
.Pp
The
.Fn deregister_hook
function should be used to deregister any
hooks that were put in place by the
.Fn register_hook
function.
If the plugin tries to deregister a hook that the front-end does not support,
.Fn deregister_hook
will return an error.
.Pp
See the
.Sx Hook function API
section below for more information about hooks.
.Pp
The
.Fn deregister_hooks
function is only available starting
with API version 1.2.
If the
.Nm sudo
front-end doesn't support API
version 1.2 or higher,
.Fn deregister_hooks
will not be called.
.It Fa event_alloc
.Bd -literal -compact
struct sudo_plugin_event * (*event_alloc)(void);
.Ed
.Pp
The
.Fn event_alloc
function is used to allocate a
.Vt struct sudo_plugin_event
which provides access to the main
.Nm sudo
event loop.
Unlike the other fields, the
.Fa event_alloc
pointer is filled in by the
.Nm sudo
front-end, not by the plugin.
.Pp
See the
.Sx Event API
section below for more information
about events.
.Pp
The
.Fn event_alloc
function is only available starting
with API version 1.15.
If the
.Nm sudo
front-end doesn't support API
version 1.15 or higher,
.Fa event_alloc
will not be set.
.El
.Pp
.Em Policy Plugin Version Macros
.Bd -literal
/* Plugin API version major/minor. */
#define SUDO_API_VERSION_MAJOR 1
#define SUDO_API_VERSION_MINOR 13
#define SUDO_API_MKVERSION(x, y) ((x << 16) | y)
#define SUDO_API_VERSION SUDO_API_MKVERSION(SUDO_API_VERSION_MAJOR,\e
                                            SUDO_API_VERSION_MINOR)

/* Getters and setters for API version */
#define SUDO_API_VERSION_GET_MAJOR(v) ((v) >> 16)
#define SUDO_API_VERSION_GET_MINOR(v) ((v) & 0xffff)
#define SUDO_API_VERSION_SET_MAJOR(vp, n) do { \e
    *(vp) = (*(vp) & 0x0000ffff) | ((n) << 16); \e
} while(0)
#define SUDO_API_VERSION_SET_MINOR(vp, n) do { \e
    *(vp) = (*(vp) & 0xffff0000) | (n); \e
} while(0)
.Ed
.Ss I/O plugin API
.Bd -literal
struct io_plugin {
#define SUDO_IO_PLUGIN 2
    unsigned int type; /* always SUDO_IO_PLUGIN */
    unsigned int version; /* always SUDO_API_VERSION */
    int (*open)(unsigned int version, sudo_conv_t conversation,
        sudo_printf_t sudo_plugin_printf, char * const settings[],
        char * const user_info[], char * const command_info[],
        int argc, char * const argv[], char * const user_env[],
        char * const plugin_options[], const char **errstr);
    void (*close)(int exit_status, int error); /* wait status or error */
    int (*show_version)(int verbose);
    int (*log_ttyin)(const char *buf, unsigned int len,
        const char **errstr);
    int (*log_ttyout)(const char *buf, unsigned int len,
        const char **errstr);
    int (*log_stdin)(const char *buf, unsigned int len,
        const char **errstr);
    int (*log_stdout)(const char *buf, unsigned int len,
        const char **errstr);
    int (*log_stderr)(const char *buf, unsigned int len,
        const char **errstr);
    void (*register_hooks)(int version,
       int (*register_hook)(struct sudo_hook *hook));
    void (*deregister_hooks)(int version,
       int (*deregister_hook)(struct sudo_hook *hook));
    int (*change_winsize)(unsigned int lines, unsigned int cols,
        const char **errstr);
    int (*log_suspend)(int signo, const char **errstr);
    struct sudo_plugin_event * (*event_alloc)(void);
};
.Ed
.Pp
When an I/O plugin is loaded,
.Nm sudo
runs the command in a pseudo-terminal.
This makes it possible to log the input and output from the user's
session.
If any of the standard input, standard output, or standard error do not
correspond to a tty,
.Nm sudo
will open a pipe to capture the I/O for logging before passing it on.
.Pp
The
.Fn log_ttyin
function receives the raw user input from the terminal
device (this will include input even when echo is disabled,
such as when a password is read).
The
.Fn log_ttyout
function receives output from the pseudo-terminal that is
suitable for replaying the user's session at a later time.
The
.Fn log_stdin ,
.Fn log_stdout ,
and
.Fn log_stderr
functions are only called if the standard input, standard output,
or standard error respectively correspond to something other than
a tty.
.Pp
Any of the logging functions may be set to the
.Dv NULL
pointer if no logging is to be performed.
If the open function returns 0, no I/O will be sent to the plugin.
.Pp
If a logging function returns an error
.Pq \-1 ,
the running command will be terminated and all of the plugin's logging
functions will be disabled.
Other I/O logging plugins will still receive any remaining
input or output that has not yet been processed.
.Pp
If an input logging function rejects the data by returning 0, the
command will be terminated and the data will not be passed to the
command, though it will still be sent to any other I/O logging plugins.
If an output logging function rejects the data by returning 0, the
command will be terminated and the data will not be written to the
terminal, though it will still be sent to any other I/O logging plugins.
.Pp
A
.Vt struct audit_plugin
has the following fields:
.Bl -tag -width 4n
.It Fa type
The
.Fa type
field should always be set to
.Dv SUDO_IO_PLUGIN .
.It Fa version
The
.Fa version
field should be set to
.Dv SUDO_API_VERSION .
.Pp
This allows
.Nm sudo
to determine the API version the plugin was
built against.
.It Fa open
.Bd -literal -compact
int (*open)(unsigned int version, sudo_conv_t conversation,
    sudo_printf_t sudo_plugin_printf, char * const settings[],
    char * const user_info[], char * const command_info[],
    int argc, char * const argv[], char * const user_env[],
    char * const plugin_options[]);
.Ed
.Pp
The
.Fn open
function is run before the
.Fn log_ttyin ,
.Fn log_ttyout ,
.Fn log_stdin ,
.Fn log_stdout ,
.Fn log_stderr ,
.Fn log_suspend ,
.Fn change_winsize ,
or
.Fn show_version
functions are called.
It is only called if the version is being requested or if the
policy plugin's
.Fn check_policy
function has returned successfully.
It returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error.
In the latter case,
.Nm sudo
will print a usage message before it exits.
If an error occurs, the plugin may optionally call the
.Fn conversation
or
.Fn sudo_plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa version
The version passed in by
.Nm sudo
allows the plugin to determine the
major and minor version number of the plugin API supported by
.Nm sudo .
.It Fa conversation
A pointer to the
.Fn conversation
function that may be used by the
.Fn Fa show_version
function to display version information (see
.Fn show_version
below).
The
.Fn conversation
function may also be used to display additional error message to the user.
The
.Fn conversation
function returns 0 on success and \-1 on failure.
.It Fa sudo_plugin_printf
A pointer to a
.Fn printf Ns -style
function that may be used by the
.Fn show_version
function to display version information (see
show_version below).
The
.Fn sudo_plugin_printf
function may also be used to display additional error message to the user.
The
.Fn sudo_plugin_printf
function returns number of characters printed on success and \-1 on failure.
.It Fa settings
A vector of user-supplied
.Nm sudo
settings in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
These settings correspond to options the user specified when running
.Nm sudo .
As such, they will only be present when the corresponding option has
been specified on the command line.
.Pp
When parsing
.Fa settings ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible settings.
.It Fa user_info
A vector of information about the user running the command in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa user_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa command_info
A vector of information describing the command being run in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa command_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa argc
The number of elements in
.Fa argv ,
not counting the final
.Dv NULL
pointer.
It can be zero, such as when
.Nm sudo
is called with the
.Fl V
option.
.It Fa argv
If
.No non- Ns Dv NULL ,
an argument vector describing a command the user
wishes to run in the same form as what would be passed to the
.Xr execve 2
system call.
.It Fa user_env
The user's environment in the form of a
.Dv NULL Ns -terminated
vector of
.Dq name=value
strings.
.Pp
When parsing
.Fa user_env ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.It Fa plugin_options
Any (non-comment) strings immediately after the plugin path are
treated as arguments to the plugin.
These arguments are split on a white space boundary and are passed to
the plugin in the form of a
.Dv NULL Ns -terminated
array of strings.
If no arguments were specified,
.Fa plugin_options
will be the
.Dv NULL
pointer.
.Pp
The
.Fa plugin_options
parameter is only available starting with
API version 1.2.
A plugin
.Sy must
check the API version specified
by the
.Nm sudo
front-end before using
.Fa plugin_options .
Failure to do so may result in a crash.
.It Fa errstr
If the
.Fn open
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa close
.Bd -literal -compact
void (*close)(int exit_status, int error);
.Ed
.Pp
The
.Fn close
function is called when
.Nm sudo
is finished, shortly before it exits.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa exit_status
The command's exit status, as returned by the
.Xr wait 2
system call, or zero if no command was run.
The value of
.Fa exit_status
is undefined if
.Fa error
is non-zero.
.It Fa error
If the command could not be executed, this is set to the value of
.Va errno
set by the
.Xr execve 2
system call.
If the command was successfully executed, the value of
.Fa error
is zero.
.El
.It Fa show_version
.Bd -literal -compact
int (*show_version)(int verbose);
.Ed
.Pp
The
.Fn show_version
function is called by
.Nm sudo
when the user specifies the
.Fl V
option.
The plugin may display its version information to the user via the
.Fn conversation
or
.Fn sudo_plugin_printf
function using
.Dv SUDO_CONV_INFO_MSG .
If the user requests detailed version information, the
.Fa verbose
flag will be non-zero.
.Pp
Returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error, although the return value is currently
ignored.
.It Fa log_ttyin
.Bd -literal -compact
int (*log_ttyin)(const char *buf, unsigned int len,
    const char **errstr);
.Ed
.Pp
The
.Fn log_ttyin
function is called whenever data can be read from
the user but before it is passed to the running command.
This allows the plugin to reject data if it chooses to (for instance
if the input contains banned content).
Returns 1 if the data should be passed to the command, 0 if the data
is rejected (which will terminate the running command), or \-1 if an
error occurred.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa buf
The buffer containing user input.
.It Fa len
The length of
.Fa buf
in bytes.
.It Fa errstr
If the
.Fn log_ttyin
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa log_ttyout
.Bd -literal -compact
int (*log_ttyout)(const char *buf, unsigned int len,
    const char **errstr);
.Ed
.Pp
The
.Fn log_ttyout
function is called whenever data can be read from
the command but before it is written to the user's terminal.
This allows the plugin to reject data if it chooses to (for instance
if the output contains banned content).
Returns 1 if the data should be passed to the user, 0 if the data is rejected
(which will terminate the running command), or \-1 if an error occurred.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa buf
The buffer containing command output.
.It Fa len
The length of
.Fa buf
in bytes.
.It Fa errstr
If the
.Fn log_ttyout
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa log_stdin
.Bd -literal -compact
int (*log_stdin)(const char *buf, unsigned int len,
    const char **errstr);
.Ed
.Pp
The
.Fn log_stdin
function is only used if the standard input does
not correspond to a tty device.
It is called whenever data can be read from the standard input but
before it is passed to the running command.
This allows the plugin to reject data if it chooses to
(for instance if the input contains banned content).
Returns 1 if the data should be passed to the command, 0 if the
data is rejected (which will terminate the running command), or \-1
if an error occurred.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa buf
The buffer containing user input.
.It Fa len
The length of
.Fa buf
in bytes.
.It Fa errstr
If the
.Fn log_stdin
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa log_stdout
.Bd -literal -compact
int (*log_stdout)(const char *buf, unsigned int len,
    const char **errstr);
.Ed
.Pp
The
.Fn log_stdout
function is only used if the standard output does not correspond
to a tty device.
It is called whenever data can be read from the command but before
it is written to the standard output.
This allows the plugin to reject data if it chooses to
(for instance if the output contains banned content).
Returns 1 if the data should be passed to the user, 0 if the data
is rejected (which will terminate the running command), or \-1 if
an error occurred.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa buf
The buffer containing command output.
.It Fa len
The length of
.Fa buf
in bytes.
.It Fa errstr
If the
.Fn log_stdout
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa log_stderr
.Bd -literal -compact
int (*log_stderr)(const char *buf, unsigned int len,
    const char **errstr);
.Ed
.Pp
The
.Fn log_stderr
function is only used if the standard error does
not correspond to a tty device.
It is called whenever data can be read from the command but before it
is written to the standard error.
This allows the plugin to reject data if it chooses to
(for instance if the output contains banned content).
Returns 1 if the data should be passed to the user, 0 if the data
is rejected (which will terminate the running command), or \-1 if
an error occurred.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa buf
The buffer containing command output.
.It Fa len
The length of
.Fa buf
in bytes.
.It Fa errstr
If the
.Fn log_stderr
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa register_hooks
See the
.Sx Policy plugin API
section for a description of
.Fn register_hooks .
.It Fa deregister_hooks
See the
.Sx Policy plugin API
section for a description of
.Fn deregister_hooks .
.It Fa change_winsize
.Bd -literal -compact
int (*change_winsize)(unsigned int lines, unsigned int cols,
    const char **errstr);
.Ed
.Pp
The
.Fn change_winsize
function is called whenever the window size of the terminal changes from
the initial values specified in the
.Fa user_info
list.
Returns \-1 if an error occurred, in which case no further calls to
.Fn change_winsize
will be made,
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa lines
The number of lines (rows) in the re-sized terminal.
.It Fa cols
The number of columns in the re-sized terminal.
.It Fa errstr
If the
.Fn change_winsize
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.El
.It Fa log_suspend
.Bd -literal -compact
int (*log_suspend)(int signo, const char **errstr);
.Ed
.Pp
The
.Fn log_suspend
function is called whenever a command is suspended or resumed.
Logging this information makes it possible to skip the period of time when
the command was suspended during playback of a session.
Returns \-1 if an error occurred, in which case no further calls to
.Fn log_suspend
will be made,
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa signo
The signal that caused the command to be suspended, or
.Dv SIGCONT
if the command was resumed.
.It Fa errstr
If the
.Fn log_suspend
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.Pp
The
.Fa errstr
parameter is only available starting with
API version 1.15.
A plugin
.Sy must
check the API version specified by the
.Nm sudo
front-end before using
.Fa errstr .
Failure to do so may result in a crash.
.It Fa event_alloc
.Bd -literal -compact
struct sudo_plugin_event * (*event_alloc)(void);
.Ed
.Pp
The
.Fn event_alloc
function is used to allocate a
.Vt struct sudo_plugin_event
which provides access to the main
.Nm sudo
event loop.
Unlike the other fields, the
.Fn event_alloc
pointer is filled in by the
.Nm sudo
front-end, not by the plugin.
.Pp
See the
.Sx Event API
section below for more information
about events.
.Pp
The
.Fn event_alloc
function is only available starting
with API version 1.15.
If the
.Nm sudo
front-end doesn't support API
version 1.15 or higher,
.Fn event_alloc
will not be set.
.El
.Pp
.Em I/O Plugin Version Macros
.Pp
Same as for the
.Sx Policy plugin API .
.El
.Ss Audit plugin API
.Bd -literal
/* Audit plugin close function status types. */
#define SUDO_PLUGIN_NO_STATUS           0
#define SUDO_PLUGIN_WAIT_STATUS         1
#define SUDO_PLUGIN_EXEC_ERROR          2
#define SUDO_PLUGIN_SUDO_ERROR          3

#define SUDO_AUDIT_PLUGIN 3
struct audit_plugin {
    unsigned int type; /* always SUDO_AUDIT_PLUGIN */
    unsigned int version; /* always SUDO_API_VERSION */
    int (*open)(unsigned int version, sudo_conv_t conversation,
        sudo_printf_t sudo_plugin_printf, char * const settings[],
        char * const user_info[], int submit_optind,
        char * const submit_argv[], char * const submit_envp[],
        char * const plugin_options[], const char **errstr);
    void (*close)(int status_type, int status);
    int (*accept)(const char *plugin_name,
        unsigned int plugin_type, char * const command_info[],
        char * const run_argv[], char * const run_envp[],
        const char **errstr);
    int (*reject)(const char *plugin_name, unsigned int plugin_type,
        const char *audit_msg, char * const command_info[],
        const char **errstr);
    int (*error)(const char *plugin_name, unsigned int plugin_type,
        const char *audit_msg, char * const command_info[],
        const char **errstr);
    int (*show_version)(int verbose);
    void (*register_hooks)(int version,
        int (*register_hook)(struct sudo_hook *hook));
    void (*deregister_hooks)(int version,
        int (*deregister_hook)(struct sudo_hook *hook));
    struct sudo_plugin_event * (*event_alloc)(void);
}
.Ed
.Pp
An audit plugin can be used to log successful and unsuccessful attempts
to run
.Nm sudo
independent of the policy or any I/O plugins.
Multiple audit plugins may be specified in
.Xr sudo.conf @mansectform@ .
.Pp
A
.Vt struct audit_plugin
has the following fields:
.Bl -tag -width 4n
.It Fa type
The
.Fa type
field should always be set to
.Dv SUDO_AUDIT_PLUGIN .
.It Fa version
The
.Fa version
field should be set to
.Dv SUDO_API_VERSION .
.Pp
This allows
.Nm sudo
to determine the API version the plugin was
built against.
.It Fa open
.Bd -literal -compact
int (*open)(unsigned int version, sudo_conv_t conversation,
    sudo_printf_t sudo_plugin_printf, char * const settings[],
    char * const user_info[], int submit_optind,
    char * const submit_argv[], char * const submit_envp[],
    char * const plugin_options[], const char **errstr);
.Ed
.Pp
The audit
.Fn open
function is run before any other
.Nm sudo
plugin API functions.
This makes it possible to audit failures in the other plugins.
It returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error.
In the latter case,
.Nm sudo
will print a usage message before it exits.
If an error occurs, the plugin may optionally call the
.Fn conversation
or
.Fn plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa version
The version passed in by
.Nm sudo
allows the plugin to determine the
major and minor version number of the plugin API supported by
.Nm sudo .
.It Fa conversation
A pointer to the
.Fn conversation
function that may be used by the
.Fn show_version
function to display version information (see
.Fn show_version
below).
The
.Fn conversation
function may also be used to display additional error message to the user.
The
.Fn conversation
function returns 0 on success, and \-1 on failure.
.It Fa plugin_printf
A pointer to a
.Fn printf Ns -style
function that may be used by the
.Fn show_version
function to display version information (see
show_version below).
The
.Fn plugin_printf
function may also be used to display additional error message to the user.
The
.Fn plugin_printf
function returns number of characters printed on success and \-1 on failure.
.It Fa settings
A vector of user-supplied
.Nm sudo
settings in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
These settings correspond to options the user specified when running
.Nm sudo .
As such, they will only be present when the corresponding option has
been specified on the command line.
.Pp
When parsing
.Fa settings ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible settings.
.It Fa user_info
A vector of information about the user running the command in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa user_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa submit_optind
The index into
.Fa submit_argv
that corresponds to the first entry that is not a command line option.
If
.Fa submit_argv
only consists of options, which may be the case with the
.Fl l
or
.Fl v
options,
.Fa submit_argv Ns [ Fa submit_optind ]
will evaluate to the NULL pointer.
.It Fa submit_argv
The argument vector
.Nm sudo
was invoked with, including all command line options.
The
.Fa submit_optind
argument can be used to determine the end of the command line options.
.It Fa submit_envp
The invoking user's environment in the form of a
.Dv NULL Ns -terminated
vector of
.Dq name=value
strings.
.Pp
When parsing
.Fa submit_envp ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.It Fa plugin_options
Any (non-comment) strings immediately after the plugin path are
treated as arguments to the plugin.
These arguments are split on a white space boundary and are passed to
the plugin in the form of a
.Dv NULL Ns -terminated
array of strings.
If no arguments were specified,
.Fa plugin_options
will be the
.Dv NULL
pointer.
.It Fa errstr
If the
.Fn open
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.El
.It Fa close
.Bd -literal -compact
void (*close)(int status_type, int status);
.Ed
.Pp
The
.Fn close
function is called when
.Nm sudo
is finished, shortly before it exits.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa status_type
The type of status being passed.
One of
.Dv SUDO_PLUGIN_NO_STATUS ,
.Dv SUDO_PLUGIN_WAIT_STATUS ,
.Dv SUDO_PLUGIN_EXEC_ERROR
or
.Dv SUDO_PLUGIN_SUDO_ERROR .
.It Fa status
Depending on the value of
.Fa status_type ,
this value is either
ignored, the command's exit status as returned by the
.Xr wait 2
system call, the value of
.Va errno
set by the
.Xr execve 2
system call, or the value of
.Va errno
resulting from an error in the
.Nm sudo
front-end.
.El
.It Fa accept
.Bd -literal -compact
int (*accept)(const char *plugin_name, unsigned int plugin_type,
    char * const command_info[], char * const run_argv[],
    char * const run_envp[], const char **errstr);
.Ed
.Pp
The
.Fn accept
function is called when a command or action is accepted by a policy
or approval plugin.
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa plugin_name
The name of the plugin that accepted the command or
.Dq sudo
for the
.Nm sudo
front-end.
.It Fa plugin_type
The type of plugin that accepted the command, currently either
.Dv SUDO_POLICY_PLUGIN ,
.Dv SUDO_POLICY_APPROVAL ,
or
.Dv SUDO_FRONT_END .
The
.Fn accept
function is called multiple times--once for each policy or approval
plugin that succeeds and once for the sudo front-end.
When called on behalf of the sudo front-end,
.Fa command_info
may include information from an I/O logging plugin as well.
.Pp
Typically, an audit plugin is interested in either the accept status from
the
.Nm sudo
front-end or from the various policy and approval plugins, but not both.
It is possible for the policy plugin to accept a command that is
later rejected by an approval plugin, in which case the audit
plugin's
.Fn accept
and
.Fn reject
functions will
.Em both
be called.
.It Fa command_info
An optional
vector of information describing the command being run in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa command_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa run_argv
A
.Dv NULL Ns -terminated
argument vector describing a command that will be run in the
same form as what would be passed to the
.Xr execve 2
system call.
.It Fa run_envp
The environment the command will be run with in the form of a
.Dv NULL Ns -terminated
vector of
.Dq name=value
strings.
.Pp
When parsing
.Fa run_envp ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.It Fa errstr
If the
.Fn accept
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.El
.It Fa reject
.Bd -literal -compact
int (*reject)(const char *plugin_name, unsigned int plugin_type,
    const char *audit_msg, char * const command_info[],
    const char **errstr);
.Ed
.Pp
The
.Fn reject
function is called when a command or action is rejected by a plugin.
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa plugin_name
The name of the plugin that rejected the command.
.It Fa plugin_type
The type of plugin that rejected the command, currently either
.Dv SUDO_POLICY_PLUGIN ,
.Dv SUDO_APPROVAL_PLUGIN ,
or
.Dv SUDO_IO_PLUGIN .
.Pp
Unlike the
.Fn accept
function, the
.Fn reject
function is not called on behalf of the
.Nm sudo
front-end.
.It Fa audit_msg
An optional string describing the reason the command was rejected
by the plugin.
If the plugin did not provide a reason,
.Fa audit_msg
will be the
.Dv NULL
pointer.
.It Fa command_info
An optional
vector of information describing the command being run in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa command_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa errstr
If the
.Fn reject
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.El
.It Fa error
.Bd -literal -compact
int (*error)(const char *plugin_name, unsigned int plugin_type,
    const char *audit_msg, char * const command_info[],
    const char **errstr);
.Ed
.Pp
The
.Fn error
function is called when a plugin or the
.Nm sudo
front-end returns an error.
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa plugin_name
The name of the plugin that generated the error or
.Dq sudo
for the
.Nm sudo
front-end.
.It Fa plugin_type
The type of plugin that generated the error, or
.Dv SUDO_FRONT_END
for the
.Nm sudo
front-end.
.It Fa audit_msg
An optional string describing the plugin error.
If the plugin did not provide a description,
.Fa audit_msg
will be the
.Dv NULL
pointer.
.It Fa command_info
An optional
vector of information describing the command being run in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa command_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa errstr
If the
.Fn error
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.El
.It Fa show_version
.Bd -literal -compact
int (*show_version)(int verbose);
.Ed
.Pp
The
.Fn show_version
function is called by
.Nm sudo
when the user specifies the
.Fl V
option.
The plugin may display its version information to the user via the
.Fn conversation
or
.Fn plugin_printf
function using
.Dv SUDO_CONV_INFO_MSG .
If the user requests detailed version information, the verbose flag will be set.
.Pp
Returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error, although the return value is currently
ignored.
.It Fa register_hooks
See the
.Sx Policy plugin API
section for a description of
.Fn register_hooks .
.It Fa deregister_hooks
See the
.Sx Policy plugin API
section for a description of
.Fn deregister_hooks .
.It Fa event_alloc
.Bd -literal -compact
struct sudo_plugin_event * (*event_alloc)(void);
.Ed
.Pp
The
.Fn event_alloc
function is used to allocate a
.Vt struct sudo_plugin_event
which provides access to the main
.Nm sudo
event loop.
Unlike the other fields, the
.Fa event_alloc
pointer is filled in by the
.Nm sudo
front-end, not by the plugin.
.Pp
See the
.Sx Event API
section below for more information
about events.
.Pp
The
.Fn event_alloc
function is only available starting
with API version 1.17.
If the
.Nm sudo
front-end doesn't support API
version 1.17 or higher,
.Fn event_alloc
will not be set.
.El
.Ss Approval plugin API
.Bd -literal
struct approval_plugin {
#define SUDO_APPROVAL_PLUGIN 4
    unsigned int type; /* always SUDO_APPROVAL_PLUGIN */
    unsigned int version; /* always SUDO_API_VERSION */
    int (*open)(unsigned int version, sudo_conv_t conversation,
        sudo_printf_t sudo_plugin_printf, char * const settings[],
        char * const user_info[], int submit_optind,
        char * const submit_argv[], char * const submit_envp[],
        char * const plugin_options[], const char **errstr);
    void (*close)(void);
    int (*check)(char * const command_info[], char * const run_argv[],
        char * const run_envp[], const char **errstr);
    int (*show_version)(int verbose);
};
.Ed
.Pp
An approval plugin can be used to apply extra constraints after a
command has been accepted by the policy plugin.
Unlike the other plugin types, it does not remain open until the command
completes.
The plugin is opened before a call to
.Fn check
or
.Fn show_version
and closed shortly thereafter (audit plugin functions must be called
before the plugin is closed).
Multiple approval plugins may be specified in
.Xr sudo.conf @mansectform@ .
.Pp
A
.Vt struct approval_plugin
has the following fields:
.Bl -tag -width 4n
.It Fa type
The
.Fa type
field should always be set to
.Dv SUDO_APPROVAL_PLUGIN .
.It Fa version
The
.Fa version
field should be set to
.Dv SUDO_API_VERSION .
.Pp
This allows
.Nm sudo
to determine the API version the plugin was
built against.
.It Fa open
.Bd -literal -compact
int (*open)(unsigned int version, sudo_conv_t conversation,
    sudo_printf_t sudo_plugin_printf, char * const settings[],
    char * const user_info[], int submit_optind,
    char * const submit_argv[], char * const submit_envp[],
    char * const plugin_options[], const char **errstr);
.Ed
.Pp
The approval
.Fn open
function is run immediately before a call to the plugin's
.Fn check
or
.Fn show_version
functions.
It is only called if the version is being requested or if the
policy plugin's
.Fn check_policy
function has returned successfully.
It returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error.
In the latter case,
.Nm sudo
will print a usage message before it exits.
If an error occurs, the plugin may optionally call the
.Fn conversation
or
.Fn plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa version
The version passed in by
.Nm sudo
allows the plugin to determine the
major and minor version number of the plugin API supported by
.Nm sudo .
.It Fa conversation
A pointer to the
.Fn conversation
function that can be used by the plugin to interact with the user (see
.Sx Conversation API
for details).
Returns 0 on success and \-1 on failure.
.It Fa plugin_printf
A pointer to a
.Fn printf Ns -style
function that may be used to display informational or error messages (see
.Sx Conversation API
for details).
Returns the number of characters printed on success and \-1 on failure.
.It Fa settings
A vector of user-supplied
.Nm sudo
settings in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
These settings correspond to options the user specified when running
.Nm sudo .
As such, they will only be present when the corresponding option has
been specified on the command line.
.Pp
When parsing
.Fa settings ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible settings.
.It Fa user_info
A vector of information about the user running the command in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa user_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa submit_optind
The index into
.Fa submit_argv
that corresponds to the first entry that is not a command line option.
If
.Fa submit_argv
only consists of options, which may be the case with the
.Fl l
or
.Fl v
options,
.Fa submit_argv Ns [ Fa submit_optind ]
will evaluate to the NULL pointer.
.It Fa submit_argv
The argument vector
.Nm sudo
was invoked with, including all command line options.
The
.Fa submit_optind
argument can be used to determine the end of the command line options.
.It Fa submit_envp
The invoking user's environment in the form of a
.Dv NULL Ns -terminated
vector of
.Dq name=value
strings.
.Pp
When parsing
.Fa submit_envp ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.It Fa plugin_options
Any (non-comment) strings immediately after the plugin path are
treated as arguments to the plugin.
These arguments are split on a white space boundary and are passed to
the plugin in the form of a
.Dv NULL Ns -terminated
array of strings.
If no arguments were specified,
.Fa plugin_options
will be the
.Dv NULL
pointer.
.It Fa errstr
If the
.Fn open
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.El
.It Fa close
.Bd -literal -compact
void (*close)(void);
.Ed
.Pp
The
.Fn close
function is called after the approval plugin's
.Fn check
or
.Fn show_version
functions have been called.
It takes no arguments.
The
.Fn close
function is typically used to perform plugin-specific cleanup,
such as the freeing of memory objects allocated by the plugin.
If the plugin does not need to perform any cleanup,
.Fn close
may be set to the
.Dv NULL
pointer.
.It Fa check
.Bd -literal -compact
int (*check)(char * const command_info[], char * const run_argv[],
    char * const run_envp[], const char **errstr);
.Ed
.Pp
The approval
.Fn check
function is run after the policy plugin
.Fn check_policy
function and before any I/O logging plugins.
If multiple approval plugins are loaded, they must all succeed for
the command to be allowed.
It returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error.
In the latter case,
.Nm sudo
will print a usage message before it exits.
If an error occurs, the plugin may optionally call the
.Fn conversation
or
.Fn plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa command_info
A vector of information describing the command being run in the form of
.Dq name=value
strings.
The vector is terminated by a
.Dv NULL
pointer.
.Pp
When parsing
.Fa command_info ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.Pp
See the
.Sx Policy plugin API
section for a list of all possible strings.
.It Fa run_argv
A
.Dv NULL Ns -terminated
argument vector describing a command that will be run in the
same form as what would be passed to the
.Xr execve 2
system call.
.It Fa run_envp
The environment the command will be run with in the form of a
.Dv NULL Ns -terminated
vector of
.Dq name=value
strings.
.Pp
When parsing
.Fa run_envp ,
the plugin should split on the
.Sy first
equal sign
.Pq Ql =
since the
.Em name
field will never include one
itself but the
.Em value
might.
.It Fa errstr
If the
.Fn open
function returns a value other than 1, the plugin may
store a message describing the failure or error in
.Fa errstr .
The
.Nm sudo
front-end will then pass this value to any registered audit plugins.
The string stored in
.Fa errstr
must remain valid until the plugin's
.Fn close
function is called.
.El
.It Fa show_version
.Bd -literal -compact
int (*show_version)(int verbose);
.Ed
.Pp
The
.Fn show_version
function is called by
.Nm sudo
when the user specifies the
.Fl V
option.
The plugin may display its version information to the user via the
.Fn conversation
or
.Fn plugin_printf
function using
.Dv SUDO_CONV_INFO_MSG .
If the user requests detailed version information, the verbose flag will be set.
.Pp
Returns 1 on success, 0 on failure, \-1 if a general error occurred,
or \-2 if there was a usage error, although the return value is currently
ignored.
.El
.Ss Signal handlers
The
.Nm sudo
front-end installs default signal handlers to trap common signals
while the plugin functions are run.
The following signals are trapped by default before the command is
executed:
.Pp
.Bl -bullet -compact -width 1n
.It
.Dv SIGALRM
.It
.Dv SIGHUP
.It
.Dv SIGINT
.It
.Dv SIGPIPE
.It
.Dv SIGQUIT
.It
.Dv SIGTERM
.It
.Dv SIGTSTP
.It
.Dv SIGUSR1
.It
.Dv SIGUSR2
.El
.Pp
If a fatal signal is received before the command is executed,
.Nm sudo
will call the plugin's
.Fn close
function with an exit status of 128 plus the value of the signal
that was received.
This allows for consistent logging of commands killed by a signal
for plugins that log such information in their
.Fn close
function.
An exception to this is
.Dv SIGPIPE ,
which is ignored until the command is executed.
.Pp
A plugin may temporarily install its own signal handlers but must
restore the original handler before the plugin function returns.
.Ss Hook function API
Beginning with plugin API version 1.2, it is possible to install
hooks for certain functions called by the
.Nm sudo
front-end.
.Pp
Currently, the only supported hooks relate to the handling of
environment variables.
Hooks can be used to intercept attempts to get, set, or remove
environment variables so that these changes can be reflected in
the version of the environment that is used to execute a command.
A future version of the API will support hooking internal
.Nm sudo
front-end functions as well.
.Pp
.Em Hook structure
.Pp
Hooks in
.Nm sudo
are described by the following structure:
.Bd -literal
typedef int (*sudo_hook_fn_t)();

struct sudo_hook {
    unsigned int hook_version;
    unsigned int hook_type;
    sudo_hook_fn_t hook_fn;
    void *closure;
};
.Ed
.Pp
A
.Vt struct sudo_hook
has the following fields:
.Bl -tag -width 4n
.It Fa hook_version
The
.Fa hook_version
field should be set to
.Dv SUDO_HOOK_VERSION .
.It Fa hook_type
The
.Fa hook_type
field may be one of the following supported hook types:
.Bl -tag -width 4n
.It Dv SUDO_HOOK_SETENV
The C library
.Xr setenv 3
function.
Any registered hooks will run before the C library implementation.
The
.Fa hook_fn
field should
be a function that matches the following typedef:
.Bd -literal
typedef int (*sudo_hook_fn_setenv_t)(const char *name,
   const char *value, int overwrite, void *closure);
.Ed
.Pp
If the registered hook does not match the typedef the results are
unspecified.
.It Dv SUDO_HOOK_UNSETENV
The C library
.Xr unsetenv 3
function.
Any registered hooks will run before the C library implementation.
The
.Fa hook_fn
field should
be a function that matches the following typedef:
.Bd -literal
typedef int (*sudo_hook_fn_unsetenv_t)(const char *name,
   void *closure);
.Ed
.It Dv SUDO_HOOK_GETENV
The C library
.Xr getenv 3
function.
Any registered hooks will run before the C library implementation.
The
.Fa hook_fn
field should
be a function that matches the following typedef:
.Bd -literal
typedef int (*sudo_hook_fn_getenv_t)(const char *name,
   char **value, void *closure);
.Ed
.Pp
If the registered hook does not match the typedef the results are
unspecified.
.It Dv SUDO_HOOK_PUTENV
The C library
.Xr putenv 3
function.
Any registered hooks will run before the C library implementation.
The
.Fa hook_fn
field should
be a function that matches the following typedef:
.Bd -literal
typedef int (*sudo_hook_fn_putenv_t)(char *string,
   void *closure);
.Ed
.Pp
If the registered hook does not match the typedef the results are
unspecified.
.El
.It Fa hook_fn
.Bd -literal -compact
sudo_hook_fn_t hook_fn;
.Ed
.Pp
The
.Fa hook_fn
field should be set to the plugin's hook implementation.
The actual function arguments will vary depending on the
.Fa hook_type
(see
.Fa hook_type
above).
In all cases, the
.Fa closure
field of
.Vt struct sudo_hook
is passed as the last function parameter.
This can be used to pass arbitrary data to the plugin's hook implementation.
.Pp
The function return value may be one of the following:
.Bl -tag -width 4n
.It Dv SUDO_HOOK_RET_ERROR
The hook function encountered an error.
.It Dv SUDO_HOOK_RET_NEXT
The hook completed without error, go on to the next hook (including
the system implementation if applicable).
For example, a
.Xr getenv 3
hook might return
.Dv SUDO_HOOK_RET_NEXT
if the specified variable was not found in the private copy of the environment.
.It Dv SUDO_HOOK_RET_STOP
The hook completed without error, stop processing hooks for this invocation.
This can be used to replace the system implementation.
For example, a
.Fa setenv
hook that operates on a private copy of
the environment but leaves
.Va environ
unchanged.
.El
.El
.Pp
Care must be taken when hooking C library functions,
it is very easy to create an infinite loop.
For example, a
.Xr getenv 3
hook that calls the
.Xr snprintf 3
function may create a loop if the
.Xr snprintf 3
implementation calls
.Xr getenv 3
to check the locale.
To prevent this, you may wish to use a static variable in the hook
function to guard against nested calls.
For example:
.Bd -literal -offset indent
static int in_progress = 0; /* avoid recursion */
if (in_progress)
    return SUDO_HOOK_RET_NEXT;
in_progress = 1;
\&...
in_progress = 0;
return SUDO_HOOK_RET_STOP;
.Ed
.Pp
.Em Hook API Version Macros
.Bd -literal
/* Hook API version major/minor */
#define SUDO_HOOK_VERSION_MAJOR 1
#define SUDO_HOOK_VERSION_MINOR 0
#define SUDO_HOOK_VERSION SUDO_API_MKVERSION(SUDO_HOOK_VERSION_MAJOR,\e
                                              SUDO_HOOK_VERSION_MINOR)
.Ed
.Pp
For getters and setters see the
.Sx Policy plugin API .
.Ss Event API
When
.Nm sudo
runs a command, it uses an event loop to service signals and I/O.
Events may be triggered based on time, a file or socket descriptor
becoming ready, or due to receipt of a signal.
Starting with API version 1.15, it is possible for a plugin to
participate in this event loop by calling the
.Fn event_alloc
function.
.Pp
.Em Event structure
.Pp
Events are described by the following structure:
.Pp
.Bd -literal -compact
typedef void (*sudo_plugin_ev_callback_t)(int fd, int what, void *closure);

struct sudo_plugin_event {
    int (*set)(struct sudo_plugin_event *pev, int fd, int events,
        sudo_plugin_ev_callback_t callback, void *closure);
    int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
    int (*del)(struct sudo_plugin_event *pev);
    int (*pending)(struct sudo_plugin_event *pev, int events,
        struct timespec *ts);
    int (*fd)(struct sudo_plugin_event *pev);
    void (*setbase)(struct sudo_plugin_event *pev, void *base);
    void (*loopbreak)(struct sudo_plugin_event *pev);
    void (*free)(struct sudo_plugin_event *pev);
};
.Ed
.Pp
A
.Vt struct sudo_plugin_event
contains the following function pointers:
.Bl -tag -width 4n
.It Fa set
.Bd -literal -compact
int (*set)(struct sudo_plugin_event *pev, int fd, int events,
    sudo_plugin_ev_callback_t callback, void *closure);
.Ed
.Pp
The
.Fn set
function takes the following arguments:
.Bl -tag -width 4n
.It Vt struct sudo_plugin_event * Ns Fa pev
A pointer to the
.Vt struct sudo_plugin_event
itself.
.It Fa fd
The file or socket descriptor for I/O-based events or the signal
number for signal events.
For time-based events,
.Fa fd
must be \-1.
.It Fa events
The following values determine what will trigger the event callback:
.Bl -tag -width 4n
.It Dv SUDO_PLUGIN_EV_TIMEOUT
callback is run after the specified timeout expires
.It Dv SUDO_PLUGIN_EV_READ
callback is run when the file descriptor is readable
.It Dv SUDO_PLUGIN_EV_WRITE
callback is run when the file descriptor is writable
.It Dv SUDO_PLUGIN_EV_PERSIST
event is persistent and remains enabled until explicitly deleted
.It Dv SUDO_PLUGIN_EV_SIGNAL
callback is run when the specified signal is received
.El
.Pp
The
.Dv SUDO_PLUGIN_EV_PERSIST
flag may be ORed with any of the event types.
It is also possible to OR
.Dv SUDO_PLUGIN_EV_READ
and
.Dv SUDO_PLUGIN_EV_WRITE
together to run the callback when a descriptor is ready to be
either read from or written to.
All other event values are mutually exclusive.
.It Vt sudo_plugin_ev_callback_t Fa callback
.Bd -literal -compact
typedef void (*sudo_plugin_ev_callback_t)(int fd, int what,
    void *closure);
.Ed
.Pp
The function to call when an event is triggered.
The
.Fn callback
function is run with the following arguments:
.Bl -tag -width 4n
.It Fa fd
The file or socket descriptor for I/O-based events or the signal
number for signal events.
.It Fa what
The event type that triggered that callback.
For events that have multiple event types (for example
.Dv SUDO_PLUGIN_EV_READ
and
.Dv SUDO_PLUGIN_EV_WRITE )
or have an associated timeout,
.Fa what
can be used to determine why the callback was run.
.It Fa closure
The generic pointer that was specified in the
.Fn set
function.
.El
.It Fa closure
A generic pointer that will be passed to the callback function.
.El
.Pp
The
.Fn set
function returns 1 on success, and \-1 if a error occurred.
.It Fa add
.Bd -literal -compact
int (*add)(struct sudo_plugin_event *pev, struct timespec *timeout);
.Ed
.Pp
The
.Fn add
function adds the event
.Fa pev
to
.Nm sudo Ns No 's
event loop.
The event must have previously been initialized via the
.Fn set
function.
If the
.Fa timeout
argument is not NULL, it should specify a (relative) timeout after
which the event will be triggered if the main event criteria has
not been met.
This is often used to implement an I/O timeout where the event
will fire if a descriptor is not ready within a certain time
period.
If the event is already present in the event loop, its
.Fa timeout
will be adjusted to match the new value, if any.
.Pp
The
.Fn add
function returns 1 on success, and \-1 if a error occurred.
.It Fa del
.Bd -literal -compact
int (*del)(struct sudo_plugin_event *pev);
.Ed
.Pp
The
.Fn del
function deletes the event
.Fa pev
from
.Nm sudo Ns No 's
event loop.
Deleted events can be added back via the
.Fn add
function.
.Pp
The
.Fn del
function returns 1 on success, and \-1 if a error occurred.
.It Fa pending
.Bd -literal -compact
int (*pending)(struct sudo_plugin_event *pev, int events,
    struct timespec *ts);
.Ed
.Pp
The
.Fn pending
function can be used to determine whether one or more events is pending.
The
.Fa events
argument specifies which events to check for.
See the
.Fn set
function for a list of valid event types.
If
.Dv SUDO_PLUGIN_EV_TIMEOUT
is specified in
.Fa events ,
the event has an associated timeout and the
.Fa ts
pointer is non-NULL, it will be filled in with the remaining time.
.It Fa fd
.Bd -literal -compact
int (*fd)(struct sudo_plugin_event *pev);
.Ed
.Pp
The
.Fn fd
function returns the descriptor or signal number associated with
the event
.Fa pev .
.It Fa setbase
.Bd -literal -compact
void (*setbase)(struct sudo_plugin_event *pev, void *base);
.Ed
.Pp
The
.Fn setbase
function sets the underlying event
.Fa base
for
.Fa pev
to the specified value.
This can be used to move an event created via
.Fn event_alloc
to a new event loop allocated by sudo's event subsystem.
If
.Fa base
is
.Dv NULL ,
.Fa pev Ns 's
event base is reset to the default value, which corresponds to
.Nm sudo Ns 's
main event loop.
Using this function requires linking the plugin with the sudo_util
library.
It is unlikely to be used outside of the
.Nm sudoers
plugin.
.It Fa loopbreak
.Bd -literal -compact
void (*loopbreak)(struct sudo_plugin_event *pev);
.Ed
.Pp
The
.Fn loopbreak
function causes
.Nm sudo Ns No 's
event loop to exit immediately and the running command to be terminated.
.It Fa free
.Bd -literal -compact
void (*free)(struct sudo_plugin_event *pev);
.Ed
.Pp
The
.Fn free
function deletes the event
.Fa pev
from the event loop and frees the memory associated with it.
.El
.Ss Remote command execution
The
.Nm sudo
front-end does not support running remote commands.
However, starting with
.Nm sudo
1.8.8, the
.Fl h
option may be used to specify a remote host that is passed
to the policy plugin.
A plugin may also accept a
.Em runas_user
in the form of
.Dq user@hostname
which will work with older versions of
.Nm sudo .
It is anticipated that remote commands will be supported by executing a
.Dq helper
program.
The policy plugin should setup the execution environment such that the
.Nm sudo
front-end will run the helper which, in turn, will connect to the
remote host and run the command.
.Pp
For example, the policy plugin could utilize
.Nm ssh
to perform remote command execution.
The helper program would be responsible for running
.Nm ssh
with the proper options to use a private key or certificate
that the remote host will accept and run a program
on the remote host that would setup the execution environment
accordingly.
.Pp
Remote
.Nm sudoedit
functionality must be handled by the policy plugin, not
.Nm sudo
itself as the front-end has no knowledge that a remote command is
being executed.
This may be addressed in a future revision of the plugin API.
.Ss Conversation API
If the plugin needs to interact with the user, it may do so via the
.Fn conversation
function.
A plugin should not attempt to read directly from the standard input
or the user's terminal (neither of which are guaranteed to exist).
The caller must include a trailing newline in
.Fa msg
if one is to be printed.
.Pp
A
.Fn printf Ns -style
function is also available that can be used to display informational
or error messages to the user, which is usually more convenient for
simple messages where no use input is required.
.Pp
.Em Conversation function structures
.Pp
The conversation function takes as arguments pointers to the following
structures:
.Bd -literal
struct sudo_conv_message {
#define SUDO_CONV_PROMPT_ECHO_OFF  0x0001 /* do not echo user input */
#define SUDO_CONV_PROMPT_ECHO_ON   0x0002 /* echo user input */
#define SUDO_CONV_ERROR_MSG        0x0003 /* error message */
#define SUDO_CONV_INFO_MSG         0x0004 /* informational message */
#define SUDO_CONV_PROMPT_MASK      0x0005 /* mask user input */
#define SUDO_CONV_PROMPT_ECHO_OK   0x1000 /* flag: allow echo if no tty */
#define SUDO_CONV_PREFER_TTY       0x2000 /* flag: use tty if possible */
    int msg_type;
    int timeout;
    const char *msg;
};

#define SUDO_CONV_REPL_MAX      1023

struct sudo_conv_reply {
    char *reply;
};

typedef int (*sudo_conv_callback_fn_t)(int signo, void *closure);
struct sudo_conv_callback {
    unsigned int version;
    void *closure;
    sudo_conv_callback_fn_t on_suspend;
    sudo_conv_callback_fn_t on_resume;
};
.Ed
.Pp
Pointers to the
.Fn conversation
and
.Fn printf Ns -style
functions are passed
in to the plugin's
.Fn open
function when the plugin is initialized.
The following type definitions can be used in the declaration of the
.Fn open
function:
.Bd -literal
typedef int (*sudo_conv_t)(int num_msgs,
    const struct sudo_conv_message msgs[],
    struct sudo_conv_reply replies[], struct sudo_conv_callback *callback);

typedef int (*sudo_printf_t)(int msg_type, const char * restrict fmt, ...);
.Ed
.Pp
To use the
.Fn conversation
function, the plugin must pass an array of
.Vt struct sudo_conv_message
and
.Vt struct sudo_conv_reply .
There must be a
.Vt struct sudo_conv_message
and
.Vt struct sudo_conv_reply
for each message in the conversation, that is, both arrays must
have the same number of elements.
Each
.Vt struct sudo_conv_reply
must have its
.Fa reply
member initialized to
.Dv NULL .
The
.Vt struct sudo_conv_callback
pointer, if not
.Dv NULL ,
should contain function pointers to be called when the
.Nm sudo
process is suspended and/or resumed during conversation input.
The
.Fa on_suspend
and
.Fa on_resume
functions are called with the signal that caused
.Nm sudo
to be suspended and the
.Fa closure
pointer from the
.Vt struct sudo_conv_callback .
These functions should return 0 on success and \-1 on error.
On error, the conversation will end and the conversation function
will return a value of \-1.
The intended use is to allow the plugin to release resources, such as locks,
that should not be held indefinitely while suspended and then reacquire them
when the process is resumed.
The functions are not actually invoked from within a signal handler.
.Pp
The
.Fa msg_type
must be set to one of the following values:
.Bl -tag -width 4n
.It Dv SUDO_CONV_PROMPT_ECHO_OFF
Prompt the user for input with echo disabled;
this is generally used for passwords.
The reply will be stored in the
.Fa replies
array, and it will never be
.Dv NULL .
.It Dv SUDO_CONV_PROMPT_ECHO_ON
Prompt the user for input with echo enabled.
The reply will be stored in the
.Fa replies
array, and it will never be
.Dv NULL .
.It Dv SUDO_CONV_ERROR_MSG
Display an error message.
The message is written to the standard error unless the
.Dv SUDO_CONV_PREFER_TTY
flag is set, in which case it is written to the user's terminal if possible.
.It Dv SUDO_CONV_INFO_MSG
Display a message.
The message is written to the standard output unless the
.Dv SUDO_CONV_PREFER_TTY
flag is set, in which case it is written to the user's terminal if possible.
.It Dv SUDO_CONV_PROMPT_MASK
Prompt the user for input but echo an asterisk character for each
character read.
The reply will be stored in the
.Fa replies
array, and it will never be
.Dv NULL .
This can be used to provide visual feedback to the user while reading
sensitive information that should not be displayed.
.El
.Pp
In addition to the above values, the following flag bits may also be set:
.Bl -tag -width 4n
.It Dv SUDO_CONV_PROMPT_ECHO_OK
Allow input to be read when echo cannot be disabled
when the message type is
.Dv SUDO_CONV_PROMPT_ECHO_OFF
or
.Dv SUDO_CONV_PROMPT_MASK .
By default,
.Nm sudo
will refuse to read input if the echo cannot be disabled for those
message types.
.It Dv SUDO_CONV_PREFER_TTY
When displaying a message via
.Dv SUDO_CONV_ERROR_MSG
or
.Dv SUDO_CONV_INFO_MSG ,
try to write the message to the user's terminal.
If the terminal is unavailable, the standard error or standard output
will be used, depending upon whether
.Dv SUDO_CONV_ERROR_MSG
or
.Dv SUDO_CONV_INFO_MSG
was used.
The user's terminal is always used when possible for input,
this flag is only used for output.
.El
.Pp
The
.Fa timeout
in seconds until the prompt will wait for no more input.
A zero value implies an infinite timeout.
.Pp
The plugin is responsible for freeing the reply buffer located in each
.Vt struct sudo_conv_reply ,
if it is not
.Dv NULL .
.Dv SUDO_CONV_REPL_MAX
represents the maximum length of the reply buffer (not including
the trailing NUL character).
In practical terms, this is the longest password
.Nm sudo
will support.
.Pp
The
.Fn printf Ns -style
function uses the same underlying mechanism as the
.Fn conversation
function but only supports
.Dv SUDO_CONV_INFO_MSG
and
.Dv SUDO_CONV_ERROR_MSG
for the
.Fa msg_type
parameter.
It can be more convenient than using the
.Fn conversation
function if no user reply is needed and supports standard
.Fn printf
escape sequences.
.Pp
See the sample plugin for an example of the
.Fn conversation
function usage.
.Ss Plugin invocation order
As of
.Nm sudo
1.9.0, the plugin
.Fn open
and
.Fn close
functions are called in the
following order:
.Bl -enum
.It
audit open
.It
policy open
.It
approval open
.It
approval close
.It
I/O log open
.It
command runs
.It
command exits
.It
I/O log close
.It
policy close
.It
audit close
.It
sudo exits
.El
.Pp
Prior to
.Nm sudo
1.9.0, the I/O log
.Fn close
function was called
.Em after
the policy
.Fn close
function.
.Ss Sudoers group plugin API
The
.Nm sudoers
plugin supports its own plugin interface to allow non-Unix
group lookups.
This can be used to query a group source other than the standard Unix
group database.
Two sample group plugins are bundled with
.Nm sudo ,
.Em group_file ,
and
.Em system_group ,
are detailed in
.Xr sudoers @mansectform@ .
Third party group plugins include a QAS AD plugin available from Quest Software.
.Pp
A group plugin must declare and populate a
.Vt struct sudoers_group_plugin
in the global scope.
This structure contains pointers to the functions that implement plugin
initialization, cleanup, and group lookup.
.Bd -literal
struct sudoers_group_plugin {
    unsigned int version;
    int (*init)(int version, sudo_printf_t sudo_plugin_printf,
        char *const argv[]);
    void (*cleanup)(void);
    int (*query)(const char *user, const char *group,
        const struct passwd *pwd);
};
.Ed
.Pp
A
.Vt struct sudoers_group_plugin
has the following fields:
.Bl -tag -width 4n
.It Fa version
The
.Fa version
field should be set to GROUP_API_VERSION.
.Pp
This allows
.Nm sudoers
to determine the API version the group plugin
was built against.
.It Fa init
.Bd -literal -compact
int (*init)(int version, sudo_printf_t sudo_plugin_printf,
    char *const argv[]);
.Ed
.Pp
The
.Fn init
function is called after
.Em sudoers
has been parsed but
before any policy checks.
It returns 1 on success, 0 on failure (or if the plugin is not configured),
and \-1 if a error occurred.
If an error occurs, the plugin may call the
.Fn plugin_printf
function with
.Dv SUDO_CONF_ERROR_MSG
to present additional error information to the user.
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa version
The version passed in by
.Nm sudoers
allows the plugin to determine the
major and minor version number of the group plugin API supported by
.Nm sudoers .
.It Fa plugin_printf
A pointer to a
.Fn printf Ns -style
function that may be used to display informational or error message to the user.
Returns the number of characters printed on success and \-1 on failure.
.It Fa argv
A
.Dv NULL Ns -terminated
array of arguments generated from the
.Em group_plugin
option in
.Em sudoers .
If no arguments were given,
.Fa argv
will be
.Dv NULL .
.El
.It Fa cleanup
.Bd -literal -compact
void (*cleanup)();
.Ed
.Pp
The
.Fn cleanup
function is called when
.Nm sudoers
has finished its
group checks.
The plugin should free any memory it has allocated and close open file handles.
.It Fa query
.Bd -literal -compact
int (*query)(const char *user, const char *group,
    const struct passwd *pwd);
.Ed
.Pp
The
.Fn query
function is used to ask the group plugin whether
.Fa user
is a member of
.Fa group .
.Pp
The function arguments are as follows:
.Bl -tag -width 4n
.It Fa user
The name of the user being looked up in the external group database.
.It Fa group
The name of the group being queried.
.It Fa pwd
The password database entry for
.Fa user ,
if any.
If
.Fa user
is not
present in the password database,
.Fa pwd
will be
.Dv NULL .
.El
.El
.Pp
.Em Group API Version Macros
.Bd -literal
/* Sudoers group plugin version major/minor */
#define GROUP_API_VERSION_MAJOR 1
#define GROUP_API_VERSION_MINOR 0
#define GROUP_API_VERSION ((GROUP_API_VERSION_MAJOR << 16) | \e
                           GROUP_API_VERSION_MINOR)
.Ed
For getters and setters see the
.Sx Policy plugin API .
.Sh PLUGIN API CHANGELOG
The following revisions have been made to the Sudo Plugin API.
.Bl -tag -width 4n
.It Version 1.0
Initial API version.
.It Version 1.1 (sudo 1.8.0)
The I/O logging plugin's
.Fn open
function was modified to take the
.Fa command_info
list as an argument.
.It Version 1.2 (sudo 1.8.5)
The Policy and I/O logging plugins'
.Fn open
functions are now passed
a list of plugin parameters if any are specified in
.Xr sudo.conf @mansectform@ .
.Pp
A simple hooks API has been introduced to allow plugins to hook in to the
system's environment handling functions.
.Pp
The
.Fn init_session
Policy plugin function is now passed a pointer
to the user environment which can be updated as needed.
This can be used to merge in environment variables stored in the PAM
handle before a command is run.
.It Version 1.3 (sudo 1.8.7)
Support for the
.Em exec_background
entry has been added to the
.Fa command_info
list.
.Pp
The
.Em max_groups
and
.Em plugin_dir
entries were added to the
.Fa settings
list.
.Pp
The
.Fn version
and
.Fn close
functions are now optional.
Previously, a missing
.Fn version
or
.Fn close
function would result in a crash.
If no policy plugin
.Fn close
function is defined, a default
.Fn close
function will be provided by the
.Nm sudo
front-end that displays a warning if the command could not be
executed.
.Pp
The
.Nm sudo
front-end now installs default signal handlers to trap common signals
while the plugin functions are run.
.It Version 1.4 (sudo 1.8.8)
The
.Em remote_host
entry was added to the
.Fa settings
list.
.It Version 1.5 (sudo 1.8.9)
The
.Em preserve_fds
entry was added to the
.Fa command_info
list.
.It Version 1.6 (sudo 1.8.11)
The behavior when an I/O logging plugin returns an error
.Pq \-1
has changed.
Previously, the
.Nm sudo
front-end took no action when the
.Fn log_ttyin ,
.Fn log_ttyout ,
.Fn log_stdin ,
.Fn log_stdout ,
or
.Fn log_stderr
function returned an error.
.Pp
The behavior when an I/O logging plugin returns 0 has changed.
Previously, output from the command would be displayed to the
terminal even if an output logging function returned 0.
.It Version 1.7 (sudo 1.8.12)
The
.Em plugin_path
entry was added to the
.Fa settings
list.
.Pp
The
.Em debug_flags
entry now starts with a debug file path name and may occur multiple
times if there are multiple plugin-specific Debug lines in the
.Xr sudo.conf @mansectform@ file.
.It Version 1.8 (sudo 1.8.15)
The
.Em sudoedit_checkdir
and
.Em sudoedit_follow
entries were added to the
.Fa command_info
list.
The default value of
.Em sudoedit_checkdir
was changed to true in sudo 1.8.16.
.Pp
The sudo
.Fn conversation
function now takes a pointer to a
.Vt struct sudo_conv_callback
as its fourth argument.
The
.Vt sudo_conv_t
definition has been updated to match.
The plugin must specify that it supports plugin API version 1.8 or higher
to receive a conversation function pointer that supports this argument.
.It Version 1.9 (sudo 1.8.16)
The
.Em execfd
entry was added to the
.Fa command_info
list.
.It Version 1.10 (sudo 1.8.19)
The
.Em umask
entry was added to the
.Fa user_info
list.
The
.Em iolog_group ,
.Em iolog_mode ,
and
.Em iolog_user
entries were added to the
.Fa command_info
list.
.It Version 1.11 (sudo 1.8.20)
The
.Em timeout
entry was added to the
.Fa settings
list.
.It Version 1.12 (sudo 1.8.21)
The
.Fn change_winsize
function was added to
.Vt struct io_plugin .
.It Version 1.13 (sudo 1.8.26)
The
.Fn log_suspend
function was added to
.Vt struct io_plugin .
.It Version 1.14 (sudo 1.8.29)
The
.Em umask_override
entry was added to the
.Fa command_info
list.
.It Version 1.15 (sudo 1.9.0)
The
.Em cwd_optional
entry was added to the
.Fa command_info
list.
.Pp
The
.Fn event_alloc
function was added to
.Vt struct policy_plugin
and
.Vt struct io_plugin .
.Pp
The
.Fa errstr
argument was added to the policy and I/O plugin functions
which the plugin function can use to return an error string.
This string may be used by the audit plugin to report failure or
error conditions set by the other plugins.
.Pp
The
.Fn close
function is now is called regardless of whether or not a command
was actually executed.
This makes it possible for plugins to perform cleanup even when a
command was not run.
.Pp
.Dv SUDO_CONV_REPL_MAX
has increased from 255 to 1023 bytes.
.Pp
Support for audit and approval plugins was added.
.It Version 1.16 (sudo 1.9.3)
Initial resource limit values were added to the
.Fa user_info
list.
.Pp
The
.Em cmnd_chroot
and
.Em cmnd_cwd
entries were added to the
.Fa settings
list.
.It Version 1.17 (sudo 1.9.4)
The
.Fn event_alloc
function was added to
.Vt struct audit_plugin
and
.Vt struct approval_plugin .
.It Version 1.18 (sudo 1.9.9)
The policy may now set resource limit values in the
.Fa command_info
list.
The
.Em intercept
and
.Em log_subcmds
entries were added to the
.Fa command_info
list.
.It Version 1.19 (sudo 1.9.11)
The
.Em intercept_ptrace
and
.Em intercept_setid
entries were added to the
.Fa settings
list.
The
.Em apparmor_profile
and
.Em use_ptrace
entries were added to the
.Fa command_info
list.
.It Version 1.20 (sudo 1.9.12)
The
.Em update_ticket
entry was added to the
.Fa settings
list.
The
.Em intercept_verify
entry was added to the
.Fa command_info
list.
.It Version 1.21 (sudo 1.9.13)
The
.Em sudoedit_nfiles
entry was added to the
.Fa command_info
list.
.It Version 1.22 (sudo 1.9.16)
The
.Em ttydev
entry was added to the
.Fa user_info
list.
.El
.Sh SEE ALSO
.Xr sudo.conf @mansectform@ ,
.Xr sudoers @mansectform@ ,
.Xr sudo @mansectsu@
.Sh AUTHORS
Many people have worked on
.Nm sudo
over the years; this version consists of code written primarily by:
.Bd -ragged -offset indent
.An Todd C. Miller
.Ed
.Pp
See the CONTRIBUTORS.md file in the
.Nm sudo
distribution (https://www.sudo.ws/about/contributors/) for an
exhaustive list of people who have contributed to
.Nm sudo .
.Sh BUGS
If you believe you have found a bug in
.Nm ,
you can either file a bug report in the sudo bug database,
https://bugzilla.sudo.ws/, or open an issue at
https://github.com/sudo-project/sudo/issues.
If you would prefer to use email, messages may be sent to the
sudo-workers mailing list,
https://www.sudo.ws/mailman/listinfo/sudo-workers (public)
or <sudo@sudo.ws> (private).
.Pp
Please do not report security vulnerabilities through public GitHub
issues, Bugzilla or mailing lists.
Instead, report them via email to <Todd.Miller@sudo.ws>.
You may encrypt your message with PGP if you would like, using
the key found at https://www.sudo.ws/dist/PGPKEYS.
.Sh SUPPORT
Limited free support is available via the sudo-users mailing list,
see https://www.sudo.ws/mailman/listinfo/sudo-users to subscribe or
search the archives.
.Sh DISCLAIMER
.Nm sudo
is provided
.Dq AS IS
and any express or implied warranties, including, but not limited
to, the implied warranties of merchantability and fitness for a
particular purpose are disclaimed.
See the LICENSE.md file distributed with
.Nm sudo
or https://www.sudo.ws/about/license/ for complete details.