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author | THOBY Simon <Simon.THOBY@viveris.fr> | 2021-08-16 08:11:01 +0000 |
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committer | Mimi Zohar <zohar@linux.ibm.com> | 2021-08-16 17:35:35 -0400 |
commit | 8ecd39cb61d9e302716d73be329c4d4822c24931 (patch) | |
tree | aa22f9b920ee39cf366404b4f7468c5b8860a176 /security | |
parent | 4f2946aa0c45c78b4f4ef101bab9694e38c68db0 (diff) | |
download | linux-8ecd39cb61d9e302716d73be329c4d4822c24931.tar.gz |
IMA: prevent SETXATTR_CHECK policy rules with unavailable algorithms
SETXATTR_CHECK policy rules assume that any algorithm listed in the 'appraise_algos' flag must be accepted when performing setxattr() on the security.ima xattr. However nothing checks that they are available in the current kernel. A userland application could hash a file with a digest that the kernel wouldn't be able to verify. However, if SETXATTR_CHECK is not in use, the kernel already forbids that xattr write. Verify that algorithms listed in appraise_algos are available to the current kernel and reject the policy update otherwise. This will fix the inconsistency between SETXATTR_CHECK and non-SETXATTR_CHECK behaviors. That filtering is only performed in ima_parse_appraise_algos() when updating policies so that we do not have to pay the price of allocating a hash object every time validate_hash_algo() is called in ima_inode_setxattr(). Signed-off-by: THOBY Simon <Simon.THOBY@viveris.fr> Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
Diffstat (limited to 'security')
-rw-r--r-- | security/integrity/ima/ima_policy.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/security/integrity/ima/ima_policy.c b/security/integrity/ima/ima_policy.c index 9eaa509f487a..87b9b71cb820 100644 --- a/security/integrity/ima/ima_policy.c +++ b/security/integrity/ima/ima_policy.c @@ -1258,6 +1258,12 @@ static unsigned int ima_parse_appraise_algos(char *arg) return 0; } + if (!crypto_has_alg(hash_algo_name[idx], 0, 0)) { + pr_err("unavailable hash algorithm \"%s\", check your kernel configuration", + token); + return 0; + } + /* Add the hash algorithm to the 'allowed' bitfield */ res |= (1U << idx); } |