fs/smb/client/smb1encrypt.c

// SPDX-License-Identifier: LGPL-2.1
/*
 *
 *   Encryption and hashing operations relating to NTLM, NTLMv2.  See MS-NLMP
 *   for more detailed information
 *
 *   Copyright (C) International Business Machines  Corp., 2005,2013
 *   Author(s): Steve French (sfrench@us.ibm.com)
 *
 */

#include <linux/fips.h>
#include <crypto/md5.h>
#include <crypto/utils.h>
#include "cifsproto.h"
#include "smb1proto.h"
#include "cifs_debug.h"

/*
 * Calculate and return the CIFS signature based on the mac key and SMB PDU.
 * The 16 byte signature must be allocated by the caller. Note we only use the
 * 1st eight bytes and that the smb header signature field on input contains
 * the sequence number before this function is called. Also, this function
 * should be called with the server->srv_mutex held.
 */
static int cifs_calc_signature(struct smb_rqst *rqst,
			struct TCP_Server_Info *server, char *signature)
{
	struct md5_ctx ctx;

	if (!rqst->rq_iov || !signature || !server)
		return -EINVAL;
	if (fips_enabled) {
		cifs_dbg(VFS,
			 "MD5 signature support is disabled due to FIPS\n");
		return -EOPNOTSUPP;
	}

	md5_init(&ctx);
	md5_update(&ctx, server->session_key.response, server->session_key.len);

	return __cifs_calc_signature(
		rqst, server, signature,
		&(struct cifs_calc_sig_ctx){ .md5 = &ctx });
}

/* must be called with server->srv_mutex held */
int cifs_sign_rqst(struct smb_rqst *rqst, struct TCP_Server_Info *server,
		   __u32 *pexpected_response_sequence_number)
{
	int rc = 0;
	char smb_signature[20];
	struct smb_hdr *cifs_pdu = (struct smb_hdr *)rqst->rq_iov[0].iov_base;

	if ((cifs_pdu == NULL) || (server == NULL))
		return -EINVAL;

	spin_lock(&server->srv_lock);
	if (!(cifs_pdu->Flags2 & SMBFLG2_SECURITY_SIGNATURE) ||
	    server->tcpStatus == CifsNeedNegotiate) {
		spin_unlock(&server->srv_lock);
		return rc;
	}
	spin_unlock(&server->srv_lock);

	if (!server->session_estab) {
		memcpy(cifs_pdu->Signature.SecuritySignature, "BSRSPYL", 8);
		return rc;
	}

	cifs_pdu->Signature.Sequence.SequenceNumber =
				cpu_to_le32(server->sequence_number);
	cifs_pdu->Signature.Sequence.Reserved = 0;

	*pexpected_response_sequence_number = ++server->sequence_number;
	++server->sequence_number;

	rc = cifs_calc_signature(rqst, server, smb_signature);
	if (rc)
		memset(cifs_pdu->Signature.SecuritySignature, 0, 8);
	else
		memcpy(cifs_pdu->Signature.SecuritySignature, smb_signature, 8);

	return rc;
}

int cifs_verify_signature(struct smb_rqst *rqst,
			  struct TCP_Server_Info *server,
			  __u32 expected_sequence_number)
{
	unsigned int rc;
	char server_response_sig[8];
	char what_we_think_sig_should_be[20];
	struct smb_hdr *cifs_pdu = (struct smb_hdr *)rqst->rq_iov[0].iov_base;

	if (cifs_pdu == NULL || server == NULL)
		return -EINVAL;

	if (!server->session_estab)
		return 0;

	if (cifs_pdu->Command == SMB_COM_LOCKING_ANDX) {
		struct smb_com_lock_req *pSMB =
			(struct smb_com_lock_req *)cifs_pdu;
		if (pSMB->LockType & LOCKING_ANDX_OPLOCK_RELEASE)
			return 0;
	}

	/* BB what if signatures are supposed to be on for session but
	   server does not send one? BB */

	/* Do not need to verify session setups with signature "BSRSPYL "  */
	if (memcmp(cifs_pdu->Signature.SecuritySignature, "BSRSPYL ", 8) == 0)
		cifs_dbg(FYI, "dummy signature received for smb command 0x%x\n",
			 cifs_pdu->Command);

	/* save off the original signature so we can modify the smb and check
		its signature against what the server sent */
	memcpy(server_response_sig, cifs_pdu->Signature.SecuritySignature, 8);

	cifs_pdu->Signature.Sequence.SequenceNumber =
					cpu_to_le32(expected_sequence_number);
	cifs_pdu->Signature.Sequence.Reserved = 0;

	cifs_server_lock(server);
	rc = cifs_calc_signature(rqst, server, what_we_think_sig_should_be);
	cifs_server_unlock(server);

	if (rc)
		return rc;

/*	cifs_dump_mem("what we think it should be: ",
		      what_we_think_sig_should_be, 16); */

	if (crypto_memneq(server_response_sig, what_we_think_sig_should_be, 8))
		return -EACCES;
	else
		return 0;

}