Re: [ima-evm-utils PATCH 09/12] Use a local hash algorithm variable when verifying file signatures

[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 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 | 40 ++++++++++++++++++++++++----------------
>   1 file changed, 24 insertions(+), 16 deletions(-)
> 
> diff --git a/src/libimaevm.c b/src/libimaevm.c
> index 4c9da7a2f06b..18b6a6f27237 100644
> --- a/src/libimaevm.c
> +++ b/src/libimaevm.c
> @@ -488,6 +488,7 @@ void init_public_keys(const char *keyfiles)
>    * (Note: signature_v2_hdr struct does not contain the 'type'.)
>    */
>   static int verify_hash_common(void *public_keys, const char *file,
> +			      const char *hash_algo,
>   			      const unsigned char *hash,
>   			      int size, unsigned char *sig, int siglen)
>   {
> @@ -499,7 +500,7 @@ static int verify_hash_common(void *public_keys, const char *file,
>   	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);
>   	}
>   
> @@ -530,7 +531,7 @@ static int verify_hash_common(void *public_keys, const char *file,
>   	if (!EVP_PKEY_verify_init(ctx))
>   		goto err;
>   	st = "EVP_get_digestbyname";
> -	if (!(md = EVP_get_digestbyname(imaevm_params.hash_algo)))
> +	if (!(md = EVP_get_digestbyname(hash_algo)))
>   		goto err;
>   	st = "EVP_PKEY_CTX_set_signature_md";
>   	if (!EVP_PKEY_CTX_set_signature_md(ctx, md))
> @@ -566,11 +567,12 @@ err:
>    * Return: 0 verification good, 1 verification bad, -1 error.
>    */
>   static int verify_hash_v2(void *public_keys, 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);
>   }
>   
> @@ -581,19 +583,20 @@ static int verify_hash_v2(void *public_keys, const char *file,
>    * Return: 0 verification good, 1 verification bad, -1 error.
>    */
>   static int verify_hash_v3(void *public_keys, 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 */
> @@ -636,8 +639,10 @@ 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);
> @@ -757,10 +762,10 @@ int verify_hash2(void *public_keys, const char *file, const char *hash_algo,
>   		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;
> @@ -774,7 +779,8 @@ int verify_hash2(void *public_keys, const char *file, const char *hash_algo,
>   int verify_hash(const char *file, const unsigned char *hash, int size,
>   		unsigned char *sig, int siglen)
>   {
> -	return verify_hash2(g_public_keys, file, NULL, hash, size, sig, siglen);
> +	return verify_hash2(g_public_keys, file, imaevm_params.hash_algo,
> +			    hash, size, sig, siglen);

Now you are passing valid parameters into verify_hash2(). Would it not 
be possible to drop 4/12?