[ima-evm-utils PATCH v2 09/13] Use a local hash algorithm variable when verifying file signatures

Mimi Zohar
2023-12-06T19:28:20Z

Instead of relying on the "imaevm_params.algo" global variable, which
is not concurrency-safe, define and use a local variable.

Update static verify_hash_v2(), verify_hash_v3(), and verify_hash_common()
function definitions to include a hash algorithm argument.

Similarly update ima_verify_signature2() and ima_calc_hash2() to define
and use a local hash algorithm variable.

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
src/libimaevm.c | 48 ++++++++++++++++++++++++++++--------------------
1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/src/libimaevm.c b/src/libimaevm.c
index c14ba7632b61..10e1ed3eab4d 100644
--- a/src/libimaevm.c
+++ b/src/libimaevm.c
@@ -484,7 +484,8 @@ __attribute__((deprecated)) void init_public_keys(const char *keyfiles)
* (Note: signature_v2_hdr struct does not contain the 'type'.)
*/
static int verify_hash_common(struct public_key_entry *public_keys,
- const char *file, const unsigned char *hash,
+ const char *file, const char *hash_algo,
+ const unsigned char *hash,
int size, unsigned char *sig, int siglen)
{
int ret = -1;
@@ -495,7 +496,7 @@ static int verify_hash_common(struct public_key_entry *public_keys,
const char *st;

if (imaevm_params.verbose > LOG_INFO) {
- log_info("hash(%s): ", imaevm_params.hash_algo);
+ log_info("hash(%s): ", hash_algo);
log_dump(hash, size);
}

@@ -526,7 +527,8 @@ static int verify_hash_common(struct public_key_entry *public_keys,
if (!EVP_PKEY_verify_init(ctx))
goto err;
st = "EVP_get_digestbyname";
- if (!(md = EVP_get_digestbyname(imaevm_params.hash_algo)))
+ md = EVP_get_digestbyname(hash_algo);
+ if (!md)
goto err;
st = "EVP_PKEY_CTX_set_signature_md";
if (!EVP_PKEY_CTX_set_signature_md(ctx, md))
@@ -562,11 +564,12 @@ err:
* Return: 0 verification good, 1 verification bad, -1 error.
*/
static int verify_hash_v2(struct public_key_entry *public_keys,
- const char *file, const unsigned char *hash,
+ const char *file, const char *hash_algo,
+ const unsigned char *hash,
int size, unsigned char *sig, int siglen)
{
/* note: signature_v2_hdr does not contain 'type', use sig + 1 */
- return verify_hash_common(public_keys, file, hash, size,
+ return verify_hash_common(public_keys, file, hash_algo, hash, size,
sig + 1, siglen - 1);
}

@@ -577,19 +580,20 @@ static int verify_hash_v2(struct public_key_entry *public_keys,
* Return: 0 verification good, 1 verification bad, -1 error.
*/
static int verify_hash_v3(struct public_key_entry *public_keys,
- const char *file, const unsigned char *hash,
+ const char *file, const char *hash_algo,
+ const unsigned char *hash,
int size, unsigned char *sig, int siglen)
{
unsigned char sigv3_hash[MAX_DIGEST_SIZE];
int ret;

- ret = calc_hash_sigv3(sig[0], NULL, hash, sigv3_hash);
+ ret = calc_hash_sigv3(sig[0], hash_algo, hash, sigv3_hash);
if (ret < 0)
return ret;

/* note: signature_v2_hdr does not contain 'type', use sig + 1 */
- return verify_hash_common(public_keys, file, sigv3_hash, size,
- sig + 1, siglen - 1);
+ return verify_hash_common(public_keys, file, hash_algo, sigv3_hash,
+ size, sig + 1, siglen - 1);
}

#define HASH_MAX_DIGESTSIZE 64 /* kernel HASH_MAX_DIGESTSIZE is 64 bytes */
@@ -632,8 +636,10 @@ int calc_hash_sigv3(enum evm_ima_xattr_type type, const char *algo,
return -EINVAL;
}

- if (!algo)
- algo = imaevm_params.hash_algo;
+ if (!algo) {
+ log_err("Hash algorithm unspecified\n");
+ return -EINVAL;
+ }

if ((hash_algo = imaevm_get_hash_algo(algo)) < 0) {
log_err("Hash algorithm %s not supported\n", algo);
@@ -753,10 +759,10 @@ int imaevm_verify_hash(void *public_keys, const char *file,
return -1;
#endif
} else if (sig[1] == DIGSIG_VERSION_2) {
- return verify_hash_v2(public_keys, file, hash, size,
+ return verify_hash_v2(public_keys, file, hash_algo, hash, size,
sig, siglen);
} else if (sig[1] == DIGSIG_VERSION_3) {
- return verify_hash_v3(public_keys, file, hash, size,
+ return verify_hash_v3(public_keys, file, hash_algo, hash, size,
sig, siglen);
} else
return -1;
@@ -766,8 +772,8 @@ __attribute__((deprecated)) int verify_hash(const char *file,
const unsigned char *hash, int size,
unsigned char *sig, int siglen)
{
- return imaevm_verify_hash(g_public_keys, file, NULL, hash, size,
- sig, siglen);
+ return imaevm_verify_hash(g_public_keys, file, imaevm_params.hash_algo,
+ hash, size, sig, siglen);
}

int ima_verify_signature2(void *public_keys, const char *file,
@@ -776,6 +782,7 @@ int ima_verify_signature2(void *public_keys, const char *file,
{
unsigned char hash[MAX_DIGEST_SIZE];
int hashlen, sig_hash_algo;
+ const char *hash_algo;

if (sig[0] != EVM_IMA_XATTR_DIGSIG && sig[0] != IMA_VERITY_DIGSIG) {
log_err("%s: xattr ima has no signature\n", file);
@@ -793,22 +800,23 @@ int ima_verify_signature2(void *public_keys, const char *file,
return -1;
}
/* Use hash algorithm as retrieved from signature */
- imaevm_params.hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);
+ hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);

/*
* Validate the signature based on the digest included in the
* measurement list, not by calculating the local file digest.
*/
if (digest && digestlen > 0)
- return imaevm_verify_hash(public_keys, file, NULL, digest,
- digestlen, sig, siglen);
+ return imaevm_verify_hash(public_keys, file,
+ hash_algo, digest, digestlen,
+ sig, siglen);

- hashlen = ima_calc_hash(file, hash);
+ hashlen = ima_calc_hash2(file, hash_algo, hash);
if (hashlen <= 1)
return hashlen;
assert(hashlen <= sizeof(hash));

- return imaevm_verify_hash(public_keys, file, NULL, hash, hashlen,
+ return imaevm_verify_hash(public_keys, file, hash_algo, hash, hashlen,
sig, siglen);
}

--
2.39.3