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smb: client: Compare MACs in constant time

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

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Cc: stable@vger.kernel.org
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Eric Biggers 2026-02-17 20:27:02 -08:00 • committed by Steve French
parent 8098179dc9
commit 26bc83b88b
2 changed files with 5 additions and 2 deletions
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3
fs/smb/client/smb1encrypt.c
View file

@ -11,6 +11,7 @@
#include <linux/fips.h>
#include <crypto/md5.h>
#include <crypto/utils.h>
#include "cifsproto.h"
#include "smb1proto.h"
#include "cifs_debug.h"
@ -131,7 +132,7 @@ int cifs_verify_signature(struct smb_rqst *rqst,
/* cifs_dump_mem("what we think it should be: ",
what_we_think_sig_should_be, 16); */
if (memcmp(server_response_sig, what_we_think_sig_should_be, 8))
if (crypto_memneq(server_response_sig, what_we_think_sig_should_be, 8))
return -EACCES;
else
return 0;

4
fs/smb/client/smb2transport.c
View file

@ -20,6 +20,7 @@
#include <linux/highmem.h>
#include <crypto/aead.h>
#include <crypto/sha2.h>
#include <crypto/utils.h>
#include "cifsglob.h"
#include "cifsproto.h"
#include "smb2proto.h"
@ -617,7 +618,8 @@ smb2_verify_signature(struct smb_rqst *rqst, struct TCP_Server_Info *server)
if (rc)
return rc;
if (memcmp(server_response_sig, shdr->Signature, SMB2_SIGNATURE_SIZE)) {
if (crypto_memneq(server_response_sig, shdr->Signature,
SMB2_SIGNATURE_SIZE)) {
cifs_dbg(VFS, "sign fail cmd 0x%x message id 0x%llx\n",
shdr->Command, shdr->MessageId);
return -EACCES;