Skip to contentSkip to conversation

ksmbd: Compare MACs in constant time

PATCH New Eric Biggers 1 participant 1 message Mar 10

Subsystems (4)
Stable branch Crypto API SMB client (CIFS) Kernel SMB3 server (ksmbd)
lore
Share & tools
lore

Eric Biggers

author
#0 lore raw

PATCH 1/1 ksmbd: Compare MACs in constant time

commit c5794709bc9105935dbedef8b9cf9c06f2b559fa upstream.

To prevent timing attacks, MAC comparisons need to be constant-time. Replace the memcmp() with the correct function, crypto_memneq().

Fixes e2f34481b24d ("cifsd: add server-side procedures for SMB3")
Cc [email protected]
Signed-off-by Eric Biggers <[email protected]>
Acked-by Namjae Jeon <[email protected]>
Signed-off-by Steve French <[email protected]>
---
 fs/smb/server/auth.c    | 4 +++-
 fs/smb/server/smb2pdu.c | 5 +++--
 2 files changed, 6 insertions(+), 3 deletions(-)
fs/smb/server/auth.c +3 -1
index f8a192cc82f24..4c3384bbbb492 100644
@@ -11,10 +11,11 @@
 #include <linux/writeback.h>
 #include <linux/uio.h>
 #include <linux/xattr.h>
 #include <crypto/hash.h>
 #include <crypto/aead.h>
+#include <crypto/algapi.h>
 #include <linux/random.h>
 #include <linux/scatterlist.h>
 
 #include "auth.h"
 #include "glob.h"

@@ -279,11 +280,12 @@ int ksmbd_auth_ntlmv2(struct ksmbd_conn *conn, struct ksmbd_session *sess,
 	if (rc) {
 		ksmbd_debug(AUTH, "Could not generate sess key\n");
 		goto out;
 	}
 
-	if (memcmp(ntlmv2->ntlmv2_hash, ntlmv2_rsp, CIFS_HMAC_MD5_HASH_SIZE) != 0)
+	if (crypto_memneq(ntlmv2->ntlmv2_hash, ntlmv2_rsp,
+			  CIFS_HMAC_MD5_HASH_SIZE))
 		rc = -EINVAL;
 out:
 	if (ctx)
 		ksmbd_release_crypto_ctx(ctx);
 	kfree(construct);
fs/smb/server/smb2pdu.c +3 -2
index 2b16bd4882499..641618a9e6e8b 100644
@@ -2,10 +2,11 @@
 /*
  *   Copyright (C) 2016 Namjae Jeon <[email protected]>
  *   Copyright (C) 2018 Samsung Electronics Co., Ltd.
  */
 
+#include <crypto/algapi.h>
 #include <linux/inetdevice.h>
 #include <net/addrconf.h>
 #include <linux/syscalls.h>
 #include <linux/namei.h>
 #include <linux/statfs.h>

@@ -8428,11 +8429,11 @@ int smb2_check_sign_req(struct ksmbd_work *work)
 
 	if (ksmbd_sign_smb2_pdu(work->conn, work->sess->sess_key, iov, 1,
 				signature))
 		return 0;
 
-	if (memcmp(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
+	if (crypto_memneq(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
 		pr_err("bad smb2 signature\n");
 		return 0;
 	}
 
 	return 1;

@@ -8516,11 +8517,11 @@ int smb3_check_sign_req(struct ksmbd_work *work)
 	iov[0].iov_len = len;
 
 	if (ksmbd_sign_smb3_pdu(conn, signing_key, iov, 1, signature))
 		return 0;
 
-	if (memcmp(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
+	if (crypto_memneq(signature, signature_req, SMB2_SIGNATURE_SIZE)) {
 		pr_err("bad smb2 signature\n");
 		return 0;
 	}
 
 	return 1;

base-commit: f2ddafa93a259310ca47507153b7811ec54ab7fd

Signature · 1 line
2.53.0