IMA reads the hash algorithm from security.ima, if exists, so that a signature can be verified even if the algorithm used for the signature differs from IMA algorithm.
This patch moves ima_read_xattr() and ima_get_hash_algo() to ima_main.c, to retrieve the algorithm even if appraisal is not enabled. Knowing the algorithm in advance would be useful also for measurement. The new Digest Lists extension does not add a new entry to the measurement list if the actual file digest is found in a loaded list. It might be possible that the algorithm used for the digest lists differs from IMA algorithm. This patch also changes the requirement that security.ima must contain a signature, if the type is EVM_IMA_XATTR_DIGSIG. A signature with length zero is accepted. Signed-off-by: Roberto Sassu <[email protected]> --- security/integrity/ima/ima.h | 16 -------- security/integrity/ima/ima_appraise.c | 55 ++------------------------- security/integrity/ima/ima_main.c | 51 +++++++++++++++++++++++++ 3 files changed, 55 insertions(+), 67 deletions(-) diff --git a/security/integrity/ima/ima.h b/security/integrity/ima/ima.h index ee509c68fe14..b4a0d2a02ff2 100644 --- a/security/integrity/ima/ima.h +++ b/security/integrity/ima/ima.h @@ -248,10 +248,6 @@ int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func); void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file); enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, enum ima_hooks func); -enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, - int xattr_len); -int ima_read_xattr(struct dentry *dentry, - struct evm_ima_xattr_data **xattr_value); #else static inline int ima_appraise_measurement(enum ima_hooks func, @@ -282,18 +278,6 @@ static inline enum integrity_status ima_get_cache_status(struct integrity_iint_c return INTEGRITY_UNKNOWN; } -static inline enum hash_algo -ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len) -{ - return ima_hash_algo; -} - -static inline int ima_read_xattr(struct dentry *dentry, - struct evm_ima_xattr_data **xattr_value) -{ - return 0; -} - #endif /* CONFIG_IMA_APPRAISE */ /* LSM based policy rules require audit */ diff --git a/security/integrity/ima/ima_appraise.c b/security/integrity/ima/ima_appraise.c index 9b3b172f9748..2566dbfd2464 100644 --- a/security/integrity/ima/ima_appraise.c +++ b/security/integrity/ima/ima_appraise.c @@ -151,57 +151,6 @@ static void ima_cache_flags(struct integrity_iint_cache *iint, } } -enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, - int xattr_len) -{ - struct signature_v2_hdr *sig; - enum hash_algo ret; - - if (!xattr_value || xattr_len < 2) - /* return default hash algo */ - return ima_hash_algo; - - switch (xattr_value->type) { - case EVM_IMA_XATTR_DIGSIG: - sig = (typeof(sig))xattr_value; - if (sig->version != 2 || xattr_len <= sizeof(*sig)) - return ima_hash_algo; - return sig->hash_algo; - break; - case IMA_XATTR_DIGEST_NG: - ret = xattr_value->digest[0]; - if (ret < HASH_ALGO__LAST) - return ret; - break; - case IMA_XATTR_DIGEST: - /* this is for backward compatibility */ - if (xattr_len == 21) { - unsigned int zero = 0; - if (!memcmp(&xattr_value->digest[16], &zero, 4)) - return HASH_ALGO_MD5; - else - return HASH_ALGO_SHA1; - } else if (xattr_len == 17) - return HASH_ALGO_MD5; - break; - } - - /* return default hash algo */ - return ima_hash_algo; -} - -int ima_read_xattr(struct dentry *dentry, - struct evm_ima_xattr_data **xattr_value) -{ - ssize_t ret; - - ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, - 0, GFP_NOFS); - if (ret == -EOPNOTSUPP) - ret = 0; - return ret; -} - /* * ima_appraise_measurement - appraise file measurement * @@ -226,6 +175,10 @@ int ima_appraise_measurement(enum ima_hooks func, if (!(inode->i_opflags & IOP_XATTR)) return INTEGRITY_UNKNOWN; + if (xattr_len == sizeof(struct signature_v2_hdr) && + xattr_value->type == EVM_IMA_XATTR_DIGSIG) + rc = -ENODATA; + if (rc <= 0) { if (rc && rc != -ENODATA) goto out; diff --git a/security/integrity/ima/ima_main.c b/security/integrity/ima/ima_main.c index 0c49cf6470a4..dc53ed8b0dd0 100644 --- a/security/integrity/ima/ima_main.c +++ b/security/integrity/ima/ima_main.c @@ -143,6 +143,57 @@ static void ima_rdwr_violation_check(struct file *file, "invalid_pcr", "open_writers"); } +static enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, + int xattr_len) +{ + struct signature_v2_hdr *sig; + enum hash_algo ret; + + if (!xattr_value || xattr_len < 2) + /* return default hash algo */ + return ima_hash_algo; + + switch (xattr_value->type) { + case EVM_IMA_XATTR_DIGSIG: + sig = (typeof(sig))xattr_value; + if (sig->version != 2 || xattr_len < sizeof(*sig)) + return ima_hash_algo; + return sig->hash_algo; + case IMA_XATTR_DIGEST_NG: + ret = xattr_value->digest[0]; + if (ret < HASH_ALGO__LAST) + return ret; + break; + case IMA_XATTR_DIGEST: + /* this is for backward compatibility */ + if (xattr_len == 21) { + unsigned int zero = 0; + + if (!memcmp(&xattr_value->digest[16], &zero, 4)) + return HASH_ALGO_MD5; + else + return HASH_ALGO_SHA1; + } else if (xattr_len == 17) + return HASH_ALGO_MD5; + break; + } + + /* return default hash algo */ + return ima_hash_algo; +} + +static int ima_read_xattr(struct dentry *dentry, + struct evm_ima_xattr_data **xattr_value) +{ + ssize_t ret; + + ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, + 0, GFP_NOFS); + if (ret == -EOPNOTSUPP) + ret = 0; + return ret; +} + static void ima_check_last_writer(struct integrity_iint_cache *iint, struct inode *inode, struct file *file) { -- 2.17.1
