scsi: target: iscsi: tie the challenge length to the hash digest size

Link: https://lore.kernel.org/r/20191017131037.9903-3-mlombard@redhat.comSigned-off-by: Maurizio Lombardi <mlombard@redhat.com>
Tested-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/target/iscsi/iscsi_target_auth.c

@@ -41,16 +41,21 @@ static int chap_gen_challenge(
 	unsigned int *c_len)
 {
 	int ret;
-	unsigned char challenge_asciihex[CHAP_CHALLENGE_LENGTH * 2 + 1];
+	unsigned char *challenge_asciihex;
 	struct iscsi_chap *chap = conn->auth_protocol;
 
-	memset(challenge_asciihex, 0, CHAP_CHALLENGE_LENGTH * 2 + 1);
+	challenge_asciihex = kzalloc(chap->challenge_len * 2 + 1, GFP_KERNEL);
+	if (!challenge_asciihex)
+		return -ENOMEM;
 
-	ret = get_random_bytes_wait(chap->challenge, CHAP_CHALLENGE_LENGTH);
+	memset(chap->challenge, 0, MAX_CHAP_CHALLENGE_LEN);
+
+	ret = get_random_bytes_wait(chap->challenge, chap->challenge_len);
 	if (unlikely(ret))
-		return ret;
+		goto out;
+
 	bin2hex(challenge_asciihex, chap->challenge,
-				CHAP_CHALLENGE_LENGTH);
+				chap->challenge_len);
 	/*
 	 * Set CHAP_C, and copy the generated challenge into c_str.
 	 */
@@ -59,7 +64,10 @@ static int chap_gen_challenge(
 
 	pr_debug("[%s] Sending CHAP_C=0x%s\n\n", (caller) ? "server" : "client",
 			challenge_asciihex);
-	return 0;
+
+out:
+	kfree(challenge_asciihex);
+	return ret;
 }
 
 static int chap_test_algorithm(const char *name)
@@ -171,6 +179,9 @@ static struct iscsi_chap *chap_server_open(
 
 	chap->digest_name = chap_get_digest_name(digest_type);
 
+	/* Tie the challenge length to the digest size */
+	chap->challenge_len = chap->digest_size;
+
 	pr_debug("[server] Got CHAP_A=%d\n", digest_type);
 	*aic_len = sprintf(aic_str, "CHAP_A=%d", digest_type);
 	*aic_len += 1;
@@ -334,21 +345,23 @@ static int chap_server_compute_hash(
 	}
 
 	ret = crypto_shash_finup(desc, chap->challenge,
-				 CHAP_CHALLENGE_LENGTH, server_digest);
+				 chap->challenge_len, server_digest);
 	if (ret < 0) {
 		pr_err("crypto_shash_finup() failed for challenge\n");
 		goto out;
 	}
 
 	bin2hex(response, server_digest, chap->digest_size);
-	pr_debug("[server] %s Server Digest: %s\n", hash_name, response);
+	pr_debug("[server] %s Server Digest: %s\n",
+		chap->digest_name, response);
 
 	if (memcmp(server_digest, client_digest, chap->digest_size) != 0) {
-		pr_debug("[server] %s Digests do not match!\n\n", hash_name);
+		pr_debug("[server] %s Digests do not match!\n\n",
+			chap->digest_name);
 		goto out;
 	} else
 		pr_debug("[server] %s Digests match, CHAP connection"
-				" successful.\n\n", hash_name);
+				" successful.\n\n", chap->digest_name);
 	/*
 	 * One way authentication has succeeded, return now if mutual
 	 * authentication is not enabled.
@@ -414,7 +427,9 @@ static int chap_server_compute_hash(
 	 * initiator must not match the original CHAP_C generated by
 	 * the target.
 	 */
-	if (!memcmp(challenge_binhex, chap->challenge, CHAP_CHALLENGE_LENGTH)) {
+	if (challenge_len == chap->challenge_len &&
+				!memcmp(challenge_binhex, chap->challenge,
+				challenge_len)) {
 		pr_err("initiator CHAP_C matches target CHAP_C, failing"
 		       " login attempt\n");
 		goto out;

drivers/target/iscsi/iscsi_target_auth.h

@@ -10,7 +10,7 @@
 #define CHAP_DIGEST_SHA256	7
 #define CHAP_DIGEST_SHA3_256	8
 
-#define CHAP_CHALLENGE_LENGTH	16
+#define MAX_CHAP_CHALLENGE_LEN	32
 #define CHAP_CHALLENGE_STR_LEN	4096
 #define MAX_RESPONSE_LENGTH	128	/* sufficient for SHA3 256 */
 #define	MAX_CHAP_N_SIZE		512
@@ -34,7 +34,7 @@ extern u32 chap_main_loop(struct iscsi_conn *, struct iscsi_node_auth *, char *,
 
 struct iscsi_chap {
 	unsigned char	id;
-	unsigned char	challenge[CHAP_CHALLENGE_LENGTH];
+	unsigned char	challenge[MAX_CHAP_CHALLENGE_LEN];
 	unsigned int	challenge_len;
 	unsigned char	*digest_name;
 	unsigned int	digest_size;