/*

   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 <gnutls/gnutls.h>

#include <gnutls/crypto.h>

#include "lib/crypto/gnutls_helpers.h"

/*

  sign an outgoing message

 */

NTSTATUS smb2_sign_message(struct smb2_request_buffer *buf, DATA_BLOB session_key)

{

  uint8_t digest[gnutls_hmac_get_len(GNUTLS_MAC_SHA256)];

  uint64_t session_id;

  size_t hdr_offset;

  int rc;

  if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {

    /* can't sign non-SMB2 messages */

    return NT_STATUS_OK;

  }

  hdr_offset = buf->hdr - buf->buffer;

  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 (session_key.length == 0) {

    DEBUG(2,("Wrong session key length %u for SMB2 signing\n",

       (unsigned)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);

  rc = gnutls_hmac_fast(GNUTLS_MAC_SHA256,

            session_key.data,

            MIN(session_key.length, 16),

            buf->hdr,

            buf->size - hdr_offset,

            digest);

  if (rc < 0) {

    return gnutls_error_to_ntstatus(rc, NT_STATUS_HMAC_NOT_SUPPORTED);

  }

  DEBUG(5,("signed SMB2 message of size %u\n", (unsigned)buf->size - NBT_HDR_SIZE));

  memcpy(buf->hdr + SMB2_HDR_SIGNATURE, digest, 16);

  return NT_STATUS_OK;

}

/*

  check an incoming signature

 */

NTSTATUS smb2_check_signature(struct smb2_request_buffer *buf, DATA_BLOB session_key)

{

  uint64_t session_id;

  uint8_t digest[gnutls_hmac_get_len(GNUTLS_MAC_SHA256)];

  uint8_t sig[16];

  size_t hdr_offset;

  int rc;

  if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {

    /* can't check non-SMB2 messages */

    return NT_STATUS_OK;

  }

  hdr_offset = buf->hdr - buf->buffer;

  session_id = BVAL(buf->hdr, 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 (session_key.length == 0) {

    /* we don't have the session key yet */

    return NT_STATUS_OK;

  }

  memcpy(sig, buf->hdr+SMB2_HDR_SIGNATURE, 16);

  memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16);

  rc = gnutls_hmac_fast(GNUTLS_MAC_SHA256,

            session_key.data,

            MIN(session_key.length, 16),

            buf->hdr,

            buf->size - hdr_offset,

            digest);

  if (rc < 0) {

    return gnutls_error_to_ntstatus(rc, NT_STATUS_HMAC_NOT_SUPPORTED);

  }

  memcpy(buf->hdr + SMB2_HDR_SIGNATURE, digest, 16);

  if (!mem_equal_const_time(digest, sig, 16)) {

    DEBUG(0,("Bad SMB2 signature for message of size %u\n",

       (unsigned)buf->size-NBT_HDR_SIZE));

    dump_data(0, sig, 16);

    dump_data(0, digest, 16);

    ZERO_ARRAY(digest);

    return NT_STATUS_ACCESS_DENIED;

  }

  ZERO_ARRAY(digest);

  return NT_STATUS_OK;

}