[ima-evm-utils PATCH v2 09/13] Use a local hash algorithm variable when verifying file signatures

From: Mimi Zohar <zohar@linux.ibm.com>
To: linux-integrity@vger.kernel.org
Cc: Stefan Berger <stefanb@linux.ibm.com>, Mimi Zohar <zohar@linux.ibm.com>
Subject: [ima-evm-utils PATCH v2 09/13] Use a local hash algorithm variable when verifying file signatures
Date: Wed,  6 Dec 2023 14:27:30 -0500	[thread overview]
Message-ID: <20231206192734.339999-10-zohar@linux.ibm.com> (raw)
In-Reply-To: <20231206192734.339999-1-zohar@linux.ibm.com>

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 | 48 ++++++++++++++++++++++++++++--------------------
 1 file changed, 28 insertions(+), 20 deletions(-)

diff --git a/src/libimaevm.c b/src/libimaevm.c
index c14ba7632b61..10e1ed3eab4d 100644
--- a/src/libimaevm.c
+++ b/src/libimaevm.c
@@ -484,7 +484,8 @@ __attribute__((deprecated)) void init_public_keys(const char *keyfiles)
  * (Note: signature_v2_hdr struct does not contain the 'type'.)
  */
 static int verify_hash_common(struct public_key_entry *public_keys,
-			      const char *file, const unsigned char *hash,
+			      const char *file, const char *hash_algo,
+			      const unsigned char *hash,
 			      int size, unsigned char *sig, int siglen)
 {
 	int ret = -1;
@@ -495,7 +496,7 @@ static int verify_hash_common(struct public_key_entry *public_keys,
 	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);
 	}
 
@@ -526,7 +527,8 @@ static int verify_hash_common(struct public_key_entry *public_keys,
 	if (!EVP_PKEY_verify_init(ctx))
 		goto err;
 	st = "EVP_get_digestbyname";
-	if (!(md = EVP_get_digestbyname(imaevm_params.hash_algo)))
+	md = EVP_get_digestbyname(hash_algo);
+	if (!md)
 		goto err;
 	st = "EVP_PKEY_CTX_set_signature_md";
 	if (!EVP_PKEY_CTX_set_signature_md(ctx, md))
@@ -562,11 +564,12 @@ err:
  * Return: 0 verification good, 1 verification bad, -1 error.
  */
 static int verify_hash_v2(struct public_key_entry *public_keys,
-			  const char *file, const unsigned char *hash,
+			  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);
 }
 
@@ -577,19 +580,20 @@ static int verify_hash_v2(struct public_key_entry *public_keys,
  * Return: 0 verification good, 1 verification bad, -1 error.
  */
 static int verify_hash_v3(struct public_key_entry *public_keys,
-			  const char *file, const unsigned char *hash,
+			  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 */
@@ -632,8 +636,10 @@ 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);
@@ -753,10 +759,10 @@ int imaevm_verify_hash(void *public_keys, const char *file,
 		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;
@@ -766,8 +772,8 @@ __attribute__((deprecated)) int verify_hash(const char *file,
 					    const unsigned char *hash, int size,
 					    unsigned char *sig, int siglen)
 {
-	return imaevm_verify_hash(g_public_keys, file, NULL, hash, size,
-				  sig, siglen);
+	return imaevm_verify_hash(g_public_keys, file, imaevm_params.hash_algo,
+				  hash, size, sig, siglen);
 }
 
 int ima_verify_signature2(void *public_keys, const char *file,
@@ -776,6 +782,7 @@ int ima_verify_signature2(void *public_keys, const char *file,
 {
 	unsigned char hash[MAX_DIGEST_SIZE];
 	int hashlen, sig_hash_algo;
+	const char *hash_algo;
 
 	if (sig[0] != EVM_IMA_XATTR_DIGSIG && sig[0] != IMA_VERITY_DIGSIG) {
 		log_err("%s: xattr ima has no signature\n", file);
@@ -793,22 +800,23 @@ int ima_verify_signature2(void *public_keys, const char *file,
 		return -1;
 	}
 	/* Use hash algorithm as retrieved from signature */
-	imaevm_params.hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);
+	hash_algo = imaevm_hash_algo_by_id(sig_hash_algo);
 
 	/*
 	 * Validate the signature based on the digest included in the
 	 * measurement list, not by calculating the local file digest.
 	 */
 	if (digest && digestlen > 0)
-		return imaevm_verify_hash(public_keys, file, NULL, digest,
-					  digestlen, sig, siglen);
+		return imaevm_verify_hash(public_keys, file,
+					  hash_algo, digest, digestlen,
+					  sig, siglen);
 
-	hashlen = ima_calc_hash(file, hash);
+	hashlen = ima_calc_hash2(file, hash_algo, hash);
 	if (hashlen <= 1)
 		return hashlen;
 	assert(hashlen <= sizeof(hash));
 
-	return imaevm_verify_hash(public_keys, file, NULL, hash, hashlen,
+	return imaevm_verify_hash(public_keys, file, hash_algo, hash, hashlen,
 				  sig, siglen);
 }
 
-- 
2.39.3

