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ipe: allow secondary and platform keyrings to install/update policies

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The current policy management makes it impossible to use IPE
in a general purpose distribution. In such cases the users are not
building the kernel, the distribution is, and access to the private
key included in the trusted keyring is, for obvious reason, not
available.
This means that users have no way to enable IPE, since there will
be no built-in generic policy, and no access to the key to sign
updates validated by the trusted keyring.

Just as we do for dm-verity, kernel modules and more, allow the
secondary and platform keyrings to also validate policies. This
allows users enrolling their own keys in UEFI db or MOK to also
sign policies, and enroll them. This makes it sensible to enable
IPE in general purpose distributions, as it becomes usable by
any user wishing to do so. Keys in these keyrings can already
load kernels and kernel modules, so there is no security
downgrade.

Add a kconfig each, like dm-verity does, but default to enabled if
the dependencies are available.

Signed-off-by: Luca Boccassi <bluca@debian.org>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
[FW: fixed some style issues]
Signed-off-by: Fan Wu <wufan@kernel.org>
This commit is contained in:
Luca Boccassi 2024-09-15 11:11:19 +02:00 committed by Fan Wu
parent 5ceecb301e
commit 02e2f9aa33
3 changed files with 36 additions and 2 deletions
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5
Documentation/admin-guide/LSM/ipe.rst
View File

@ -223,7 +223,10 @@ are signed through the PKCS#7 message format to enforce some level of
authorization of the policies (prohibiting an attacker from gaining
unconstrained root, and deploying an "allow all" policy). These
policies must be signed by a certificate that chains to the
``SYSTEM_TRUSTED_KEYRING``. With openssl, the policy can be signed by::
``SYSTEM_TRUSTED_KEYRING``, or to the secondary and/or platform keyrings if
``CONFIG_IPE_POLICY_SIG_SECONDARY_KEYRING`` and/or
``CONFIG_IPE_POLICY_SIG_PLATFORM_KEYRING`` are enabled, respectively.
With openssl, the policy can be signed by::
openssl smime -sign \
-in "$MY_POLICY" \

19
security/ipe/Kconfig
View File

@ -31,6 +31,25 @@ config IPE_BOOT_POLICY
If unsure, leave blank.
config IPE_POLICY_SIG_SECONDARY_KEYRING
bool "IPE policy update verification with secondary keyring"
default y
depends on SECONDARY_TRUSTED_KEYRING
help
Also allow the secondary trusted keyring to verify IPE policy
updates.
If unsure, answer Y.
config IPE_POLICY_SIG_PLATFORM_KEYRING
bool "IPE policy update verification with platform keyring"
default y
depends on INTEGRITY_PLATFORM_KEYRING
help
Also allow the platform keyring to verify IPE policy updates.
If unsure, answer Y.
menu "IPE Trust Providers"
config IPE_PROP_DM_VERITY

14
security/ipe/policy.c
View File

@ -169,9 +169,21 @@ struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
goto err;
}
rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len, NULL,
rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len,
#ifdef CONFIG_IPE_POLICY_SIG_SECONDARY_KEYRING
VERIFY_USE_SECONDARY_KEYRING,
#else
NULL,
#endif
VERIFYING_UNSPECIFIED_SIGNATURE,
set_pkcs7_data, new);
#ifdef CONFIG_IPE_POLICY_SIG_PLATFORM_KEYRING
if (rc == -ENOKEY)
rc = verify_pkcs7_signature(NULL, 0, new->pkcs7, pkcs7len,
VERIFY_USE_PLATFORM_KEYRING,
VERIFYING_UNSPECIFIED_SIGNATURE,
set_pkcs7_data, new);
#endif
if (rc)
goto err;
} else {