From: Eric Biggers <ebiggers@kernel.org>
Date: Mon, 18 Aug 2025 20:54:23 +0000 (-0700)
Subject: sctp: Fix MAC comparison to be constant-time
X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=dd91c79e4f58fbe2898dac84858033700e0e99fb;p=users%2Fwilly%2Flinux.git

sctp: Fix MAC comparison to be constant-time

To prevent timing attacks, MACs need to be compared in constant time.
Use the appropriate helper function for this.

Fixes: bbd0d59809f9 ("[SCTP]: Implement the receive and verification of AUTH chunk")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Link: https://patch.msgid.link/20250818205426.30222-3-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index 3ead591c72fd..d099b605e44a 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -31,6 +31,7 @@
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
 #include <crypto/hash.h>
+#include <crypto/utils.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/ip.h>
@@ -1788,7 +1789,7 @@ struct sctp_association *sctp_unpack_cookie(
 		}
 	}
 
-	if (memcmp(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
+	if (crypto_memneq(digest, cookie->signature, SCTP_SIGNATURE_SIZE)) {
 		*error = -SCTP_IERROR_BAD_SIG;
 		goto fail;
 	}
diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
index a0524ba8d787..d4d5b14b49b3 100644
--- a/net/sctp/sm_statefuns.c
+++ b/net/sctp/sm_statefuns.c
@@ -30,6 +30,7 @@
 
 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
 
+#include <crypto/utils.h>
 #include <linux/types.h>
 #include <linux/kernel.h>
 #include <linux/ip.h>
@@ -4416,7 +4417,7 @@ static enum sctp_ierror sctp_sf_authenticate(
 				 sh_key, GFP_ATOMIC);
 
 	/* Discard the packet if the digests do not match */
-	if (memcmp(save_digest, digest, sig_len)) {
+	if (crypto_memneq(save_digest, digest, sig_len)) {
 		kfree(save_digest);
 		return SCTP_IERROR_BAD_SIG;
 	}