man/man3/TPMLIB_SetProfile.pod - master - githubmirror/libtpms

man/man3/TPMLIB_SetProfile.pod
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Luca Boccassi
man: fix various typos found by Lintian
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22 сен 2025, 20:292c1deb5
=head1 NAME

TPMLIB_SetProfile  - Set a profile for a TPM 2

=head1 LIBRARY

TPM library (libtpms, -ltpms)

=head1 SYNOPSIS

B<#include <libtpms/tpm_types.h>>

B<#include <libtpms/tpm_library.h>>

B<#include <libtpms/tpm_error.h>>

B<TPM_RESULT TPMLIB_SetProfile(const char *profile);>

=head1 DESCRIPTION

B<TPMLIB_SetProfile()> is used to apply one of libtpms's provided profiles
to a TPM 2 when it is started the first time. B<TPMLIB_SetProfile()> must be
called after B<TPMLIB_ChooseTPMVersion()> and before B<TPMLIB_MainInit()>.
A profile may only be applied to a TPM 2 and will always fail for a TPM 1.2.

Once a profile has been set it will be used by the TPM 2 from then on and
the profile will be carried along with the state of the TPM 2 if the state
of the TPM 2 was written using the callback registered with
B<TPMLIB_RegisterCallbacks()>. Later attempts to set a different profile
for the same TPM 2 instance using this API call will have no effect.

Libtpms v0.10 and later support several built-in profiles. The 'null' profile
provides backwards compatibility for libtpms v0.9 and only enables those
algorithm and commands that were available at that version of libtpms.
The default profile enables all currently available commands and algorithms.
Neither one of these profiles allows any modifications by the user. The
'custom' profile is the only one that a user may modify and where the user
may disable any commands and/or algorithms that can be disabled.

If a NULL pointer is given as a profile then the 'null' profile will be
used and only commands and algorithms of libtpms v0.9 will be enabled.
The state of such a TPM 2 instance will be readable by the current version of
libtpms as well as later versions of libtpms and allow for downgrading
libtpms to version 0.9 from a later version.

Profiles with the prefix 'default' enable as many algorithms and commands
as possible. The 'default-v1' profile, introduced with libtpms v0.10, allows
to run with libtpms v0.10 and later but will not allow downgrading to
earlier versions of libtpms, such as v0.9.

A profile is a JSON map in string format. It must contain the 'Name'
field with the name of a known profile. It may contain a field
'Algorithms' that holds a comma-separated list of algorithms (verbs) to
enable or the field 'Commands' that holds a comma-separated list of ranges
of command codes to enable.

The following are examples of TPM 2 profiles:

     {"Name":"default-v1"}

     {
      "Name":"custom",
      "Algorithms":"rsa,rsa-min-size=1024,tdes-min-size=128,hmac,aes,\
                    aes-min-size=128,mgf1,keyedhash,xor,sha256,sha384,\
                    sha512,null,rsassa,rsaes,rsapss,oaep,ecdsa,ecdh,ecdaa,\
                    sm2,ecschnorr,ecmqv,kdf1-sp800-56a,kdf2,kdf1-sp800-108,\
                    ecc,ecc-min-size=192,ecc-nist,ecc-nb,symcipher,camellia,\
                    camellia-min-size=128,cmac,ctr,ofb,cbc,cfb,ecb",
      "StateFormatLevel":2
     }

The first profile selects the current default profile along with all
commands and algorithms that are available.
The second profile selects the I<custom> profile but restricts the
set of algorithms that the TPM 2 provides to those ones that are listed.
Since 'sha1' and 'tdes' are missing in the list, it disables those algorithms.
Note that the I<custom> profile is the only profile that allows customizations
of enabled Algorithms, Commands, and Attributes (not shown here).

Only a subset of the implemented algorithms can be disabled. To determine
the list of algorithms that can be disabled, use the list of algorithms
return by I<TPMLIB_GetInfo(TPMLIB_INFO_RUNTIME_ALGORITHMS)> in the
'CanBeDisabled' field. Similarly, only a subset of the implemented commands
can be disabled and I<TPMLIB_GetInfo(TPMLIB_INFO_RUNTIME_COMMANDS)> can
be used to determine the list of 'CanBeDisabled' commands. No
attributes are enabled by default, so all of them can be disabled.
To see which attributes are implemented and can be enabled, use
I<TPMLIB_GetInfo(TPMLIB_INFO_RUNTIME_ATTRIBUTES)>.

Since it is possible to disable algorithms that are mandatory for the
PC Client TPM 2, one can create a TPM 2 instance that will cause
applications to fail. Therefore, it is necessary to carefully select which
algorithms to disable following the requirements of applications that will
be used. At the same time the choice of enabled commands is important
so that algorithms that are enabled can actually be used with the set
of enabled commands and applications do not fail unexpectedly because of
disabled commands. Therefore, determining the list of algorithms and
commands to enable and disable is left to the user.

=head1 StateFormatLevel

The I<StateFormatLevel> field exists in each profile carried by the
state of a TPM 2. The I<StateFormatLevel> is an integer that is increased
whenever new TPM 2 commands or algorithms are enabled for profiles. The effect
of this parameter is that a profile with I<StateFormatLevel> 'n' will not be
accepted by a libtpms version that does not at least implement
I<StateFormatLevel> 'n'. This prevents applications that may have used any newly
enabled algorithms or commands from failing because they try to use them
again with a TPM 2 from a libtpms version that does not support them.

When the above is applied to a virtual machine environment then this means that
migrating the state of a TPM 2 is only possible to a libtpms version that
implements at least the same StateFormatLevel. Therefore, care must be taken
which profile is chosen so that the profile's StateFormatLevel does not
become the obstacle for migrating the TPM state between different versions
of libtpms. This in turn means that in an environment where older libtpms
versions exist, which may be a target for migration, then the oldest
libtpms version's supported profile should be chosen. If libtpms v0.9
exists then this should be the 'null' profile, for libtpms v0.10 this can
be the the 'default-v1' profile.

The following lists the meaning of I<StateFormatLevel>s:

=over 4

=item 1: (since v0.10)

This I<StateFormatLevel> is reserved for the null profile. Only algorithms
and commands supported by libtpms v0.9 are enabled. To remain compatible
with libtpms v0.9 state format, the null profile will not be written as part
of the state.

=item 2: (since v0.10)

This I<StateFormatLevel> enabled the writing of the profile as part of the
state.

=item 3: (since v0.10)

This I<StateFormatLevel> enabled the TPM 2 commands ECC_Encrypt (0x199) and
ECC_Decrypt (0x19a).

=item 4: (since v0.10)

This I<StateFormatLevel>:

=over 2

=item * enabled Camellia-192 and AES-192.

=item * enabled setting of TPM 2-internal session attribute flag
isNameHashDefined that was added; it I<may> slightly change behavior
of sessions when for example used by default-v1 profile compared to
the null profile (libtpms v0.9).

=back

=item 5: (since v0.10)

This I<StateFormatLevel> enabled the TPM 2 commands PolicyCapability (0x19b)
and PolicyParameters (0x19c).

=item 6: (since v0.10)

This I<StateFormatLevel> made some internal changes to the marshalling and
unmarshalling code of an OBJECT. Only RSA key OBJECTS have the private
exponent field marshalled and the hierarchy field is also always marshalled
now. RSA key OBJECTs may be 4 bytes bigger while others are smaller now.

=item 7: (since v0.10)

This I<StateFormatLevel> enabled the following profile attributes:

=over 2

=item * no-unpadded-encryption

=item * no-sha1-signing

=item * no-sha1-verification

=item * no-sha1-hmac-creation

=item * no-sha1-hmac-verification

=item * no-sha1-hmac

=item * fips-host

=item * drbg-continous-test

=item * pct

=item * no-ecc-key-derivation

=back

=item 8: (since v0.11)

This I<StateFormatLevel> enabled 4096-bit RSA.

=back

A user may specify the I<StateFormatLevel> when using the I<custom> profile.
In this case the given I<StateFormatLevel> serves as the maximum
I<StateFormatLevel> that the given algorithms and commands may require
(e.g., '2' would not allow enabling the command ECC_Encrypt, which
requires '3') or allows enabling key sizes, such as AES-192, when for
example I<StateFormatLevel> '4' is given. If I<StateFormatLevel> '3'
is given then AES-192 will not be enabled.

=head1 Attributes

A profile may have the I<Attributes> key which is similar to I<Algorithms> or
I<Commands>. The following is a list of supported verbs:

=over 4

=item B<no-unpadded-encryption>: (since v0.10)

=over 2

=item * Prevents unpadded (raw) RSA encryption and decryption

=back

=item B<no-sha1-signing>: (since v0.10)

=over 2

=item * Prevents signature generation with a SHA1 with RSA and ECC
algorithms

=back

=item B<no-sha1-verification>: (since v0.10)

=over 2

=item * Prevents signature verification with a SHA1 digest with RSA and ECC
algorithms

=back

=item B<no-sha1-hmac-creation>: (since v0.10)

=over 2

=item * Prevents creation of an HMAC using SHA1

=back

=item B<no-sha1-hmac-verification>: (since v0.10)

=over 2

=item * Prevents verification of an HMAC using SHA1

=back

=item B<no-sha1-hmac>: (since v0.10)

=over 2

=item * Prevents creation and verification of an HMAC using SHA1

=back

=item B<fips-host>: (since v0.10)

=over 2

=item * Prevents unpadded (raw) RSA encryption and decryption

=item * Prevents signature generation with a SHA1 with RSA and ECC
algorithms

=item * Prevents signature verification with a SHA1 digest with RSA and ECC
algorithms

=back

By adding this verb to the I<Attributes> a TPM 2 can be run on a FIPS-enabled
host where the OpenSSL crypto library may restrict crypto algorithms as shown
above (reference is RHEL 9.4+, but varies by distro). Note that usage of this
verb does not make a TPM 2 instance compliant with FIPS-140. Also see the
section on 'FIPS mode on the host'.

=item B<drbg-continous-test>: (since v0.10)

=over 2

=item * Turns on continuous testing of the DRBG

=back

=item B<pct>: (since v0.10)

=over 2

=item * Turns on pairwise consistency test (pct) for RSA keys and EC signing
keys

=back

=item B<no-ecc-key-derivation>: (since v0.10)

=over 2

=item * Prevent ECC key derivation

=back

=back

=head1 FIPS mode on the host

If FIPS mode is enabled on a host (reference is RHEL 9.4+) then the OpenSSL
crypto library will not be able to use certain algorithms. In this case the
following list of verbs should be omitted from a profile to avoid either
selftest failures or having to disable FIPS mode in the OpenSSL instance.

=over 2

=item * camellia, camellia-min-size

=item * tdes, tdes-min-size

=item * rsaes

=item * ecc-nist-p192

=item * ecc-bn, ecc-bn-p256, ecc-bn-p638

=item * ecc-sm2-p256

=back

A profile should contain the following verbs for minimum key sizes:

=over 2

=item * rsa-min-size=2048

=item * ecc-min-size=224

=back

=head1 ERRORS

=over 4

=item B<TPM_SUCCESS>

The function completed successfully.

=item B<TPM_FAIL>

A failure occurred. This may be due to a badly formatted JSON profile,
a missing field in the JSON profile, an unknown verb in the JSON profile,
or an out of memory error. The log file may show the reason for the
failure.

A TPM 1.2 cannot have a profile applied and will always respond with
this error code.

=back

For a complete list of TPM error codes please consult the include file
B<libtpms/tpm_error.h>

=head1 EXAMPLE

 #include <stdio.h>

 #include <libtpms/tpm_types.h>
 #include <libtpms/tpm_library.h>
 #include <libtpms/tpm_error.h>

 int main(void) {
     TPM_RESULT res;
     unsigned char *respbuffer = NULL;
     uint32_t resp_size = 0;
     uint32_t respbufsize = 0;
     unsigned char *command;
     uint32_t command_size;

     [...]

     if (TPMLIB_ChooseTPMVersion(TPMLIB_TPM_VERSION_2) != TPM_SUCCESS) {
         fprintf(stderr, "Could not choose a TPM 2.\n");
         return 1;
     }

     if (TPMLIB_SetProfile(NULL) != TPM_SUCCESS) {
         fprintf(stderr, "Could not set the profile.\n");
         return 1;
     }

     if (TPMLIB_MainInit() != TPM_SUCCESS) {
         fprintf(stderr, "Could not start the TPM.\n");
         return 1;
     }

     [...]
     /* build TPM command */
     [...]

     res = TPMLIB_Process(&respbuffer, &resp_size,
                          &respbufsize,
                          command, command_size);
     [...]

     TPMLIB_Terminate();

     return 0;
 }

=head1 SEE ALSO

B<TPMLIB_ChooseTPMVersion>, B<TPMLIB_RegisterCallbacks>(3), B<TPMLIB_GetInfo>(3)

=cut