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/*
Unix SMB/CIFS implementation.
SMB2 Signing Code
Copyright (C) Andrew Tridgell <tridge@samba.org> 2008
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include "includes.h"
#include "libcli/raw/libcliraw.h"
#include "libcli/smb2/smb2.h"
#include "libcli/smb2/smb2_calls.h"
#include "heimdal/lib/hcrypto/sha.h"
/*
NOTE: this code does not yet interoperate with the windows SMB2
implementation. We are waiting on feedback on the docs to find out
why
*/
/*
setup signing on a transport
*/
NTSTATUS smb2_start_signing(struct smb2_transport *transport)
{
if (transport->signing.session_key.length != 16) {
DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
(unsigned)transport->signing.session_key.length));
return NT_STATUS_ACCESS_DENIED;
}
transport->signing.signing_started = true;
return NT_STATUS_OK;
}
/*
sign an outgoing message
*/
NTSTATUS smb2_sign_message(struct smb2_request *req)
{
struct smb2_request_buffer *buf = &req->out;
uint64_t session_id;
SHA256_CTX m;
uint8_t res[32];
if (!req->transport->signing.doing_signing ||
!req->transport->signing.signing_started) {
return NT_STATUS_OK;
}
if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {
/* can't sign non-SMB2 messages */
return NT_STATUS_OK;
}
session_id = BVAL(buf->hdr, SMB2_HDR_SESSION_ID);
if (session_id == 0) {
/* we don't sign messages with a zero session_id. See
MS-SMB2 3.2.4.1.1 */
return NT_STATUS_OK;
}
if (req->transport->signing.session_key.length != 16) {
DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
(unsigned)req->transport->signing.session_key.length));
return NT_STATUS_ACCESS_DENIED;
}
memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16);
SIVAL(buf->hdr, SMB2_HDR_FLAGS, IVAL(buf->hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
ZERO_STRUCT(m);
SHA256_Init(&m);
SHA256_Update(&m, req->transport->signing.session_key.data,
req->transport->signing.session_key.length);
SHA256_Update(&m, buf->buffer+NBT_HDR_SIZE, buf->size-NBT_HDR_SIZE);
SHA256_Final(res, &m);
DEBUG(5,("signed SMB2 message of size %u\n", (unsigned)buf->size - NBT_HDR_SIZE));
memcpy(buf->hdr + SMB2_HDR_SIGNATURE, res, 16);
if (DEBUGLVL(5)) {
/* check our own signature */
smb2_check_signature(req->transport, buf->buffer, buf->size);
}
return NT_STATUS_OK;
}
/*
check an incoming signature
*/
NTSTATUS smb2_check_signature(struct smb2_transport *transport,
uint8_t *buffer, uint_t length)
{
uint64_t session_id;
SHA256_CTX m;
uint8_t res[SHA256_DIGEST_LENGTH];
uint8_t sig[16];
if (!transport->signing.signing_started ||
!transport->signing.doing_signing) {
return NT_STATUS_OK;
}
if (length < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {
/* can't check non-SMB2 messages */
return NT_STATUS_OK;
}
session_id = BVAL(buffer+NBT_HDR_SIZE, SMB2_HDR_SESSION_ID);
if (session_id == 0) {
/* don't sign messages with a zero session_id. See
MS-SMB2 3.2.4.1.1 */
return NT_STATUS_OK;
}
if (transport->signing.session_key.length == 0) {
/* we don't have the session key yet */
return NT_STATUS_OK;
}
if (transport->signing.session_key.length != 16) {
DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
(unsigned)transport->signing.session_key.length));
return NT_STATUS_ACCESS_DENIED;
}
memcpy(sig, buffer+NBT_HDR_SIZE+SMB2_HDR_SIGNATURE, 16);
memset(buffer + NBT_HDR_SIZE + SMB2_HDR_SIGNATURE, 0, 16);
ZERO_STRUCT(m);
SHA256_Init(&m);
SHA256_Update(&m, transport->signing.session_key.data, 16);
SHA256_Update(&m, buffer+NBT_HDR_SIZE, length-NBT_HDR_SIZE);
SHA256_Final(res, &m);
memcpy(buffer+NBT_HDR_SIZE+SMB2_HDR_SIGNATURE, sig, 16);
if (memcmp(res, sig, 16) != 0) {
DEBUG(0,("Bad SMB2 signature for message of size %u\n", length));
dump_data(0, sig, 16);
dump_data(0, res, 16);
return NT_STATUS_ACCESS_DENIED;
}
return NT_STATUS_OK;
}
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