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

Stefan Berger
2023-11-22T13:55:21Z

On 11/19/23 11:50, Mimi Zohar wrote:
> 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)

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>