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26bc83b88b
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>
140 lines
3.9 KiB
C
140 lines
3.9 KiB
C
// SPDX-License-Identifier: LGPL-2.1
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/*
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*
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* Encryption and hashing operations relating to NTLM, NTLMv2. See MS-NLMP
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* for more detailed information
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*
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* Copyright (C) International Business Machines Corp., 2005,2013
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* Author(s): Steve French (sfrench@us.ibm.com)
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*
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*/
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#include <linux/fips.h>
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#include <crypto/md5.h>
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#include <crypto/utils.h>
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#include "cifsproto.h"
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#include "smb1proto.h"
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#include "cifs_debug.h"
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/*
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* Calculate and return the CIFS signature based on the mac key and SMB PDU.
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* The 16 byte signature must be allocated by the caller. Note we only use the
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* 1st eight bytes and that the smb header signature field on input contains
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* the sequence number before this function is called. Also, this function
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* should be called with the server->srv_mutex held.
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*/
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static int cifs_calc_signature(struct smb_rqst *rqst,
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struct TCP_Server_Info *server, char *signature)
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{
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struct md5_ctx ctx;
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if (!rqst->rq_iov || !signature || !server)
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return -EINVAL;
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if (fips_enabled) {
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cifs_dbg(VFS,
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"MD5 signature support is disabled due to FIPS\n");
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return -EOPNOTSUPP;
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}
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md5_init(&ctx);
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md5_update(&ctx, server->session_key.response, server->session_key.len);
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return __cifs_calc_signature(
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rqst, server, signature,
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&(struct cifs_calc_sig_ctx){ .md5 = &ctx });
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}
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/* must be called with server->srv_mutex held */
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int cifs_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server,
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__u32 *pexpected_response_sequence_number)
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{
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int rc = 0;
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char smb_signature[20];
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struct smb_hdr *cifs_pdu = (struct smb_hdr *)rqst->rq_iov[0].iov_base;
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if ((cifs_pdu == NULL) || (server == NULL))
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return -EINVAL;
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spin_lock(&server->srv_lock);
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if (!(cifs_pdu->Flags2 & SMBFLG2_SECURITY_SIGNATURE) ||
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server->tcpStatus == CifsNeedNegotiate) {
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spin_unlock(&server->srv_lock);
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return rc;
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}
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spin_unlock(&server->srv_lock);
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if (!server->session_estab) {
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memcpy(cifs_pdu->Signature.SecuritySignature, "BSRSPYL", 8);
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return rc;
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}
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cifs_pdu->Signature.Sequence.SequenceNumber =
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cpu_to_le32(server->sequence_number);
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cifs_pdu->Signature.Sequence.Reserved = 0;
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*pexpected_response_sequence_number = ++server->sequence_number;
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++server->sequence_number;
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rc = cifs_calc_signature(rqst, server, smb_signature);
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if (rc)
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memset(cifs_pdu->Signature.SecuritySignature, 0, 8);
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else
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memcpy(cifs_pdu->Signature.SecuritySignature, smb_signature, 8);
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return rc;
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}
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int cifs_verify_signature(struct smb_rqst *rqst,
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struct TCP_Server_Info *server,
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__u32 expected_sequence_number)
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{
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unsigned int rc;
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char server_response_sig[8];
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char what_we_think_sig_should_be[20];
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struct smb_hdr *cifs_pdu = (struct smb_hdr *)rqst->rq_iov[0].iov_base;
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if (cifs_pdu == NULL || server == NULL)
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return -EINVAL;
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if (!server->session_estab)
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return 0;
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if (cifs_pdu->Command == SMB_COM_LOCKING_ANDX) {
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struct smb_com_lock_req *pSMB =
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(struct smb_com_lock_req *)cifs_pdu;
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if (pSMB->LockType & LOCKING_ANDX_OPLOCK_RELEASE)
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return 0;
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}
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/* BB what if signatures are supposed to be on for session but
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server does not send one? BB */
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/* Do not need to verify session setups with signature "BSRSPYL " */
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if (memcmp(cifs_pdu->Signature.SecuritySignature, "BSRSPYL ", 8) == 0)
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cifs_dbg(FYI, "dummy signature received for smb command 0x%x\n",
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cifs_pdu->Command);
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/* save off the original signature so we can modify the smb and check
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its signature against what the server sent */
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memcpy(server_response_sig, cifs_pdu->Signature.SecuritySignature, 8);
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cifs_pdu->Signature.Sequence.SequenceNumber =
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cpu_to_le32(expected_sequence_number);
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cifs_pdu->Signature.Sequence.Reserved = 0;
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cifs_server_lock(server);
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rc = cifs_calc_signature(rqst, server, what_we_think_sig_should_be);
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cifs_server_unlock(server);
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if (rc)
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return rc;
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/* cifs_dump_mem("what we think it should be: ",
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what_we_think_sig_should_be, 16); */
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if (crypto_memneq(server_response_sig, what_we_think_sig_should_be, 8))
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return -EACCES;
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else
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return 0;
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}
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