[ima-evm-utils PATCH 10/12] Update EVM signature verification to use a local hash algorithm variable

Mimi Zohar
2023-11-19T16:51:10Z

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

Update calc_evm_hash(), verify_hash2().

Signed-off-by: Mimi Zohar <zohar@linux.ibm.com>
---
src/evmctl.c | 19 ++++++++++---------
1 file changed, 10 insertions(+), 9 deletions(-)

diff --git a/src/evmctl.c b/src/evmctl.c
index ad4565b3ee52..7ae897d8b8b3 100644
--- a/src/evmctl.c
+++ b/src/evmctl.c
@@ -340,7 +340,8 @@ err:
* Returns 0 for EVP_ function failures. Return -1 for other failures.
* Return hash algorithm size on success.
*/
-static int calc_evm_hash(const char *file, unsigned char *hash)
+static int calc_evm_hash(const char *file, const char *hash_algo,
+ unsigned char *hash)
{
const EVP_MD *md;
struct stat st;
@@ -408,10 +409,9 @@ static int calc_evm_hash(const char *file, unsigned char *hash)
}
#endif

- md = EVP_get_digestbyname(imaevm_params.hash_algo);
+ md = EVP_get_digestbyname(hash_algo);
if (!md) {
- log_err("EVP_get_digestbyname(%s) failed\n",
- imaevm_params.hash_algo);
+ log_err("EVP_get_digestbyname(%s) failed\n", hash_algo);
err = 0;
goto out;
}
@@ -570,7 +570,7 @@ static int sign_evm(const char *file, const char *key)
unsigned char sig[MAX_SIGNATURE_SIZE];
int len, err;

- len = calc_evm_hash(file, hash);
+ len = calc_evm_hash(file, imaevm_params.hash_algo, hash);
if (len <= 1)
return len;
assert(len <= sizeof(hash));
@@ -909,6 +909,7 @@ static int verify_evm(void *public_keys, const char *file)
{
unsigned char hash[MAX_DIGEST_SIZE];
unsigned char sig[MAX_SIGNATURE_SIZE];
+ const char *hash_algo = NULL;
int sig_hash_algo;
int mdlen;
int len;
@@ -938,15 +939,15 @@ static int verify_evm(void *public_keys, const char *file)
log_err("unknown hash algo: %s\n", file);
return -1;
}
- imaevm_params.hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);
+ hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);

- mdlen = calc_evm_hash(file, hash);
+ mdlen = calc_evm_hash(file, hash_algo, hash);
if (mdlen <= 1)
return mdlen;
assert(mdlen <= sizeof(hash));

- return verify_hash2(public_keys, file, imaevm_params.hash_algo,
- hash, mdlen, sig, len);
+ return verify_hash2(public_keys, file, hash_algo, hash,
+ mdlen, sig, len);
}

static int cmd_verify_evm(struct command *cmd)
--
2.39.3