Re: [ima-evm-utils PATCH v2 03/13] Update library function definitions to include a "public_keys" parameter

Stefan Berger <stefanb@xxxxxxxxxxxxx> · Tue, 2 Jan 2024 08:11:16 -0500

On 12/6/23 14:27, Mimi Zohar wrote:
Instead of relying on a global static "public_keys" variable, which is
not concurrency-safe, update static library function definitions to
include it as a parameter, define new library functions with it as
a parameter, and deprecate existing functions.

Define imaevm_init_public_keys(), imaevm_verify_hash(), and
ima_verify_signature2() functions. Update static function definitions
to include "public_keys".

To avoid library incompatibility, make the existing functions -
init_public_keys(), verify_hash(), ima_verify_signature() - wrappers
for the new function versions.

Deprecate init_public_keys(), verify_hash(), ima_verify_signature()
functions.

Signed-off-by: Mimi Zohar <zohar@xxxxxxxxxxxxx>
---
  src/imaevm.h    |  4 +++
  src/libimaevm.c | 85 ++++++++++++++++++++++++++++++++++++-------------
  2 files changed, 67 insertions(+), 22 deletions(-)

diff --git a/src/imaevm.h b/src/imaevm.h
index 470e8376f2fb..b29a4745fc77 100644
--- a/src/imaevm.h
+++ b/src/imaevm.h
@@ -249,8 +249,12 @@ uint32_t imaevm_read_keyid(const char *certfile);
  int sign_hash(const char *algo, const unsigned char *hash, int size, const char *keyfile, const char *keypass, unsigned char *sig);
  int verify_hash(const char *file, const unsigned char *hash, int size, unsigned char *sig, int siglen);
  int ima_verify_signature(const char *file, unsigned char *sig, int siglen, unsigned char *digest, int digestlen);

Forward-declare struct public_key_entry here:
struct public_key_entry;

+int ima_verify_signature2(void *public_keys, const char *file,

And use it instead of void * here. For the user it's going to be an 
opaque type but better then a void*.

+			  unsigned char *sig, int siglen,
+			  unsigned char *digest, int digestlen);
  void imaevm_free_public_keys(void *public_keys);
  void init_public_keys(const char *keyfiles);
+int imaevm_init_public_keys(const char *keyfiles, void **public_keys);
  int imaevm_hash_algo_from_sig(unsigned char *sig);
  const char *imaevm_hash_algo_by_id(int algo);
  int calc_hash_sigv3(enum evm_ima_xattr_type type, const char *algo, const unsigned char *in_hash, unsigned char *out_hash);
diff --git a/src/libimaevm.c b/src/libimaevm.c
index 534468fe99ca..6fecb2ffd139 100644
--- a/src/libimaevm.c
+++ b/src/libimaevm.c
@@ -372,12 +372,13 @@ struct public_key_entry {
  };
  static struct public_key_entry *g_public_keys = NULL;
  
-static EVP_PKEY *find_keyid(uint32_t keyid)
+static EVP_PKEY *find_keyid(struct public_key_entry *public_keys,
+			    uint32_t keyid)
  {
-	struct public_key_entry *entry, *tail = g_public_keys;
+	struct public_key_entry *entry, *tail = public_keys;
  	int i = 1;
  
-	for (entry = g_public_keys; entry; entry = entry->next) {
+	for (entry = public_keys; entry; entry = entry->next) {
  		if (entry->keyid == keyid)
  			return entry->key;
  		i++;
@@ -394,7 +395,7 @@ static EVP_PKEY *find_keyid(uint32_t keyid)
  	if (tail)
  		tail->next = entry;
  	else
-		g_public_keys = entry;
+		public_keys = (void *)entry;
  	log_err("key %d: %x (unknown keyid)\n", i, __be32_to_cpup(&keyid));
  	return 0;
  }
@@ -412,7 +413,7 @@ void imaevm_free_public_keys(void *public_keys)
  	}
  }
  
-void init_public_keys(const char *keyfiles)
+int imaevm_init_public_keys(const char *keyfiles, void **public_keys)
  {
  	struct public_key_entry *entry;
  	char *tmp_keyfiles, *keyfiles_free;
@@ -420,6 +421,11 @@ void init_public_keys(const char *keyfiles)
  	int err = 0;
  	int i = 1;
  
+	if (!public_keys)
+		return -EINVAL;
+
+	*public_keys = NULL;
+
  	tmp_keyfiles = strdup(keyfiles);
  	keyfiles_free = tmp_keyfiles;
  
@@ -444,12 +450,19 @@ void init_public_keys(const char *keyfiles)
  		calc_keyid_v2(&entry->keyid, entry->name, entry->key);
  		sprintf(entry->name, "%x", __be32_to_cpup(&entry->keyid));
  		log_info("key %d: %s %s\n", i++, entry->name, keyfile);
-		entry->next = g_public_keys;
-		g_public_keys = entry;
+		entry->next = (struct public_key_entry *)*public_keys;
+		*public_keys = (void *)entry;
  	}
+
  	free(keyfiles_free);
  	if (err < 0)
-		imaevm_free_public_keys(g_public_keys);
+		imaevm_free_public_keys(public_keys);
+	return err;
+}
+
+__attribute__((deprecated)) void init_public_keys(const char *keyfiles)

The attribute should go into the header file.



+{
+	imaevm_init_public_keys(keyfiles, (void **)&g_public_keys);
  }
  
  /*
@@ -466,7 +479,8 @@ void init_public_keys(const char *keyfiles)
   *
   * (Note: signature_v2_hdr struct does not contain the 'type'.)
   */
-static int verify_hash_common(const char *file, const unsigned char *hash,
+static int verify_hash_common(struct public_key_entry *public_keys,
+			      const char *file, const unsigned char *hash,
  			      int size, unsigned char *sig, int siglen)
  {
  	int ret = -1;
@@ -481,7 +495,7 @@ static int verify_hash_common(const char *file, const unsigned char *hash,
  		log_dump(hash, size);
  	}
  
-	pkey = find_keyid(hdr->keyid);
+	pkey = find_keyid(public_keys, hdr->keyid);
  	if (!pkey) {
  		uint32_t keyid = hdr->keyid;
  
@@ -543,11 +557,13 @@ err:
   *
   * Return: 0 verification good, 1 verification bad, -1 error.
   */
-static int verify_hash_v2(const char *file, const unsigned char *hash,
+static int verify_hash_v2(struct public_key_entry *public_keys,
+			  const char *file, 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(file, hash, size, sig + 1, siglen - 1);
+	return verify_hash_common(public_keys, file, hash, size,
+				  sig + 1, siglen - 1);
  }
  
  /*
@@ -556,7 +572,8 @@ static int verify_hash_v2(const char *file, const unsigned char *hash,
   *
   * Return: 0 verification good, 1 verification bad, -1 error.
   */
-static int verify_hash_v3(const char *file, const unsigned char *hash,
+static int verify_hash_v3(struct public_key_entry *public_keys,
+			  const char *file, const unsigned char *hash,
  			  int size, unsigned char *sig, int siglen)
  {
  	unsigned char sigv3_hash[MAX_DIGEST_SIZE];
@@ -567,7 +584,8 @@ static int verify_hash_v3(const char *file, const unsigned char *hash,
  		return ret;
  
  	/* note: signature_v2_hdr does not contain 'type', use sig + 1 */
-	return verify_hash_common(file, sigv3_hash, size, sig + 1, siglen - 1);
+	return verify_hash_common(public_keys, file, sigv3_hash, size,
+				  sig + 1, siglen - 1);
  }
  
  #define HASH_MAX_DIGESTSIZE 64	/* kernel HASH_MAX_DIGESTSIZE is 64 bytes */
@@ -710,8 +728,9 @@ int imaevm_hash_algo_from_sig(unsigned char *sig)
  		return -1;
  }
  
-int verify_hash(const char *file, const unsigned char *hash, int size,
-		unsigned char *sig, int siglen)
+int imaevm_verify_hash(void *public_keys, const char *file,
+		       const unsigned char *hash, int size,
+		       unsigned char *sig, int siglen)
  {
  	/* Get signature type from sig header */
  	if (sig[1] == DIGSIG_VERSION_1) {
@@ -730,15 +749,25 @@ int verify_hash(const char *file, const unsigned char *hash, int size,
  		return -1;
  #endif
  	} else if (sig[1] == DIGSIG_VERSION_2) {
-		return verify_hash_v2(file, hash, size, sig, siglen);
+		return verify_hash_v2(public_keys, file, hash, size,
+				      sig, siglen);
  	} else if (sig[1] == DIGSIG_VERSION_3) {
-		return verify_hash_v3(file, hash, size, sig, siglen);
+		return verify_hash_v3(public_keys, file, hash, size,
+				      sig, siglen);
  	} else
  		return -1;
  }
  
-int ima_verify_signature(const char *file, unsigned char *sig, int siglen,
-			 unsigned char *digest, int digestlen)
+__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, hash, size, sig, siglen);
+}
+
+int ima_verify_signature2(void *public_keys, const char *file,
+			  unsigned char *sig, int siglen,
+			  unsigned char *digest, int digestlen)
  {
  	unsigned char hash[MAX_DIGEST_SIZE];
  	int hashlen, sig_hash_algo;
@@ -766,14 +795,26 @@ int ima_verify_signature(const char *file, unsigned char *sig, int siglen,
  	 * measurement list, not by calculating the local file digest.
  	 */
  	if (digest && digestlen > 0)
-		return verify_hash(file, digest, digestlen, sig, siglen);
+		return imaevm_verify_hash(public_keys, file, digest, digestlen,
+					  sig, siglen);
  
  	hashlen = ima_calc_hash(file, hash);
  	if (hashlen <= 1)
  		return hashlen;
  	assert(hashlen <= sizeof(hash));
  
-	return verify_hash(file, hash, hashlen, sig, siglen);
+	return imaevm_verify_hash(public_keys, file, hash, hashlen,
+				  sig, siglen);
+}
+
+__attribute__((deprecated)) int ima_verify_signature(const char *file,
+						     unsigned char *sig,
+						     int siglen,
+						     unsigned char *digest,
+						     int digestlen)
+{
+	return ima_verify_signature2(g_public_keys, file, sig, siglen,
+				     digest, digestlen);
  }
  
  #if CONFIG_SIGV1







