Commit c5794709 authored by Eric Biggers's avatar Eric Biggers Committed by Steve French
Browse files

ksmbd: Compare MACs in constant time 



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

Fixes: e2f34481 ("cifsd: add server-side procedures for SMB3")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarEric Biggers <ebiggers@kernel.org>
Acked-by: default avatarNamjae Jeon <linkinjeon@kernel.org>
Signed-off-by: default avatarSteve French <stfrench@microsoft.com>
parent 6de23f81

fs/smb/server/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ config SMB_SERVER 
	select CRYPTO_LIB_MD5

	select CRYPTO_LIB_SHA256

	select CRYPTO_LIB_SHA512

	select CRYPTO_LIB_UTILS

	select CRYPTO_CMAC

	select CRYPTO_AEAD2

	select CRYPTO_CCM

fs/smb/server/auth.c

+3 −1
Original line number Diff line number Diff line
@@ -15,6 +15,7 @@ 
#include <crypto/aead.h>

#include <crypto/md5.h>

#include <crypto/sha2.h>

#include <crypto/utils.h>

#include <linux/random.h>

#include <linux/scatterlist.h>
@@ -165,7 +166,8 @@ int ksmbd_auth_ntlmv2(struct ksmbd_conn *conn, struct ksmbd_session *sess, 
			     ntlmv2_rsp, CIFS_HMAC_MD5_HASH_SIZE,

			     sess->sess_key);



	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))

		return -EINVAL;

	return 0;

}

fs/smb/server/smb2pdu.c

+3 −2
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 
 *   Copyright (C) 2018 Samsung Electronics Co., Ltd.

 */



#include <crypto/utils.h>

#include <linux/inetdevice.h>

#include <net/addrconf.h>

#include <linux/syscalls.h>
@@ -8880,7 +8881,7 @@ int smb2_check_sign_req(struct ksmbd_work *work) 
	ksmbd_sign_smb2_pdu(work->conn, work->sess->sess_key, iov, 1,

			    signature);



	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;

	}
@@ -8968,7 +8969,7 @@ int smb3_check_sign_req(struct ksmbd_work *work) 
	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;

	}