linux-kernel - [PATCH 3.2 083/185] iscsi-target: chap auth shouldn't match username with trailing garbage

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Message-ID: <lsq.1388282923.810464826@decadent.org.uk>
Date:	Sun, 29 Dec 2013 03:08:43 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Nicholas Bellinger" <nab@...ux-iscsi.org>,
	"Eric Seppanen" <eric@...estorage.com>
Subject: [PATCH 3.2 083/185] iscsi-target: chap auth shouldn't match
 username with trailing garbage

3.2.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Seppanen <eric@...estorage.com>

commit 86784c6bdeeef78eed94d298be7a8879f6a97ee2 upstream.

In iSCSI negotiations with initiator CHAP enabled, usernames with
trailing garbage are permitted, because the string comparison only
checks the strlen of the configured username.

e.g. "usernameXXXXX" will be permitted to match "username".

Just check one more byte so the trailing null char is also matched.

Signed-off-by: Eric Seppanen <eric@...estorage.com>
Signed-off-by: Nicholas Bellinger <nab@...ux-iscsi.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/target/iscsi/iscsi_target_auth.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/target/iscsi/iscsi_target_auth.c
+++ b/drivers/target/iscsi/iscsi_target_auth.c
@@ -172,6 +172,7 @@ static int chap_server_compute_md5(
 	unsigned char client_digest[MD5_SIGNATURE_SIZE];
 	unsigned char server_digest[MD5_SIGNATURE_SIZE];
 	unsigned char chap_n[MAX_CHAP_N_SIZE], chap_r[MAX_RESPONSE_LENGTH];
+	size_t compare_len;
 	struct iscsi_chap *chap = (struct iscsi_chap *) conn->auth_protocol;
 	struct crypto_hash *tfm;
 	struct hash_desc desc;
@@ -210,7 +211,9 @@ static int chap_server_compute_md5(
 		goto out;
 	}
 
-	if (memcmp(chap_n, auth->userid, strlen(auth->userid)) != 0) {
+	/* Include the terminating NULL in the compare */
+	compare_len = strlen(auth->userid) + 1;
+	if (strncmp(chap_n, auth->userid, compare_len) != 0) {
 		pr_err("CHAP_N values do not match!\n");
 		goto out;
 	}

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