@@ -74,7 +74,8 @@ int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
/* v1 API expect signature without xattr type */
return digsig_verify(keyring, sig + 1, siglen - 1, digest,
digestlen);
- case 2:
+ case 2: /* regular file data hash based sginature */
+ case 3: /* struct ima_file_id data base signature */
return asymmetric_verify(keyring, sig, siglen, digest,
digestlen);
}
@@ -225,6 +225,34 @@ int ima_read_xattr(struct dentry *dentry,
return ret;
}
+/*
+ * calc_file_id_hash - calculate the hash of the ima_file_id struct data
+ * @type: xattr type [enum evm_ima_xattr_type]
+ * @algo: hash algorithm [enum hash_algo]
+ * @digest: pointer to the digest to be hashed
+ * @hash: (out) pointer to the hash
+ *
+ * IMA signature version 3 disambiguates the data that is signed by
+ * indirectly signing the hash of the ima_file_id structure data.
+ *
+ * Return 0 on success, error code otherwise.
+ */
+static int calc_file_id_hash(enum evm_ima_xattr_type type,
+ enum hash_algo algo, const u8 *digest,
+ struct ima_max_digest_data *hash)
+{
+ struct ima_file_id file_id = {.hash_algorithm = algo};
+ uint unused = HASH_MAX_DIGESTSIZE - hash_digest_size[algo];
+
+ memcpy(file_id.hash, digest, hash_digest_size[algo]);
+
+ hash->algo = algo;
+ hash->length = hash_digest_size[algo];
+
+ return ima_calc_buffer_hash(&file_id, sizeof(file_id) - unused,
+ (struct ima_digest_data *)hash);
+}
+
/*
* xattr_verify - verify xattr digest or signature
*
@@ -236,6 +264,7 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
struct evm_ima_xattr_data *xattr_value, int xattr_len,
enum integrity_status *status, const char **cause)
{
+ struct signature_v2_hdr *sig;
int rc = -EINVAL, hash_start = 0;
switch (xattr_value->type) {
@@ -274,6 +303,13 @@ static int xattr_verify(enum ima_hooks func, struct integrity_iint_cache *iint,
break;
case EVM_IMA_XATTR_DIGSIG:
set_bit(IMA_DIGSIG, &iint->atomic_flags);
+
+ sig = (typeof(sig))xattr_value;
+ if (sig->version != 2) {
+ *cause = "invalid-signature-version";
+ *status = INTEGRITY_FAIL;
+ break;
+ }
rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA,
(const char *)xattr_value,
xattr_len,
@@ -94,7 +94,7 @@ struct evm_xattr {
u8 digest[SHA1_DIGEST_SIZE];
} __packed;
-#define IMA_MAX_DIGEST_SIZE 64
+#define IMA_MAX_DIGEST_SIZE HASH_MAX_DIGESTSIZE
struct ima_digest_data {
u8 algo;
@@ -137,7 +137,11 @@ struct ima_max_digest_data {
} __packed;
/*
- * signature format v2 - for using with asymmetric keys
+ * signature header format v2 - for using with asymmetric keys
+ *
+ * signature format:
+ * version 2: regular file data hash based signature
+ * version 3: struct ima_file_id data based signature
*/
struct signature_v2_hdr {
uint8_t type; /* xattr type */
@@ -148,6 +152,18 @@ struct signature_v2_hdr {
uint8_t sig[]; /* signature payload */
} __packed;
+/*
+ * IMA signature version 3 disambiguates the data that is signed, by
+ * indirectly signing the hash of the ima_file_id structure data.
+ *
+ * (The hash of the ima_file_id structure is only of the portion used.)
+ */
+struct ima_file_id {
+ __u8 hash_type; /* xattr type [enum evm_ima_xattr_type] */
+ __u8 hash_algorithm; /* Digest algorithm [enum hash_algo] */
+ __u8 hash[HASH_MAX_DIGESTSIZE];
+} __packed;
+
/* integrity data associated with an inode */
struct integrity_iint_cache {
struct rb_node rb_node; /* rooted in integrity_iint_tree */
To disambiguate the signed data stored in the 'security.ima' xattr, define signature version 3 as the hash of the ima_file_id structure. Signed-off-by: Mimi Zohar <zohar@linux.ibm.com> --- security/integrity/digsig.c | 3 ++- security/integrity/ima/ima_appraise.c | 36 +++++++++++++++++++++++++++ security/integrity/integrity.h | 20 +++++++++++++-- 3 files changed, 56 insertions(+), 3 deletions(-)