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

[Stefan Berger <stefanb@linux.ibm.com>]

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>