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

[Stefan Berger]

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 <zo...@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?