niceSOFT/inetutils

CHECKLIST
126 строк5 KB
Mats Erik Andersson
Documentation
17 июн 2013, 17:54
17 июн 2013, 17:540a482ca
This text intends to be helpful in the verification of the
utilities found within GNU Inetutils.  The source archive
does contain a small set of test, but they are never able
to test all desirable abilities, so this text is collected
in the hope that an administrator or packager find hints on
important steps to verify claimed abilities.  One upstream
author found himself overlooking a serious fault, until
rethinking procedures similar to the following.  This is
all the more relevant since GNU Inetutils aims at portability
to different operating systems, intending identical abilities
for simplification in heterogeneous environments.

Most executables delivered by GNU Inetutils depend on only
a few, and immediately recognizable, settings or mechanisms.
Others, like `ftpd', `telnetd', and `rlogind', depend on
multiple configuration files, or depend on external programs
that may differ slightly from system to system.  Executables
in the latter class include all those with Kerberos abilities.

Of particular importance, and difficulty to verify, is the
server executable `ftpd'.  This will be discussed at length
below, but let us start with some simpler cases.

1. rlogind and telnetd

The server executables `telnetd' and `rlogind' are the only
ones depending on the system executable `/bin/login`, or
sometimes `/usr/bin/login'.  This system program is heavily
system dependent, and at present we are aware that login(1)
of Solaris and of `util-linux', as found in Arch Linux, is
not completely functional in all intended use cases.

2. rcp and rsh

The client programs `rcp' and `rsh', certainly when built
with Kerberos support, need care since they delegate work
via PATH_RSH and PATH_RLOGIN, respectively.  All testing
efforts must be aware of this.  Both locations are settable
at configuration time using `--with-path-rsh=...' and
`--with-path-rlogin=...'.  Bear in mind that BSD systems
assign values to those two macros by inspecting <paths.h>,
and that these values are used unless overridden.

3. syslogd

The included test script for `syslogd' is in fact using
command line switches to override the defaults for configu-
ration file and ditto directory.  The mechanisms should
work, but their default settings must be checked for use
in prebuilt packages.  Again, `--with-path-logconf' and
`--with-path-logconfd' are the way to go.

The auto-build system Hydra, of NixOS' origin, is known
to fail occasionally at reusing a logging file after
receiving SIGHUP, but this has never happened during
manual checks.  Ideas on resolving this matter are most
welcome.  There could be some dead-lock involved here.

4. ftpd

As already stated, the server `ftpd' is particularly picky
to verify reliably.  The main obstacle lies in its use of
four different files for configuration, or in user inter-
action.  The standard macros PATH_FTPUSERS, PATH_FTPCHROOT,
and PATH_FTPWELCOME, PATH_FTPLOGINMESG are relevant here,
where the first two are of critical concern for reasons of
security.  In addition, also `/etc/shells' is referenced.

Every packager and administrator _must_ check that the files
`ftpusers' and `ftpchroot' are assigned the right locations:

   $ strings ftpd/ftpd | grep '/etc'

Let us sketch a limited set-up intended to uncover faults
in `ftpd' while handling `ftpusers' and `ftpchroot'.  The
file locations below are chosen for brevity, rather than
best practice.

   ### /etc/passwd
   root:x:0:0::/root:/bin/sh
   # Invalid interpreter
   aaa:x:11111:101::/home/aaa:/bin/false
   # To be denied access.
   bbb:x:11112:101::/home/bbb:/bin/sh
   ccc:x:11113:102::/home/ccc:/bin/sh
   # To be chrooted.
   ddd:x:11114:101::/home/ddd:/bin/sh
   eee:x:11115:103::/home/eee:/bin/sh

   ### /etc/group
   passes:x:101:
   banned:x:102:
   chroot:x:103:

   ### /etc/ftpusers
   root
   bbb
   @banned

   ### /etc/ftpchroot
   ddd
   @chroot

With this set-up, the users `aaa' should be denied access
due to an invalid shell, while `bbb' and `ccc' should be
reject for being mentioned in `ftpusers', the latter though
his group membership.  Furthermore, `ddd' and `eee' should
be admitted access, but be confined within a chrooted subtree,
recognizable by issuing `pwd' in an FTP-session.  Here, `eee'
is to be chrooted based on its group membership.

A final remark regarding the chrooted mode.  On GNU systems
and Solaris systems, the above templates `/etc/passwd' and
`/etc/group', positioned below the chroot directory,  would
suffice to allow the list command `ls' to resolve numbers as
group and user names in directory listings, but they do not
suffice on BSD systems.  For those unices, `/etc/passwd' is
completely irrelevant, and is to be replaced by `/etc/pwd.db'.
Starting from a template for `master.passwd', BSD systems need
to call pwd_mkdb(8) to generate a minimally usable `/etc/pwd.db'.
A responsible BSD administrator is expected to master this!

Ideally, the administrator should also check that expired
accounts and expired passwords also lead to denied access.
The tools vary widely, but usermod(8) and its variants
are useful.