source4/libcli/smb2/signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    SMB2 Signing Code
   5
   6    Copyright (C) Andrew Tridgell <tridge@samba.org> 2008
   7
   8    This program is free software; you can redistribute it and/or modify
   9    it under the terms of the GNU General Public License as published by
  10    the Free Software Foundation; either version 3 of the License, or
  11    (at your option) any later version.
  12
  13    This program is distributed in the hope that it will be useful,
  14    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16    GNU General Public License for more details.
  17
  18    You should have received a copy of the GNU General Public License
  19    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  20 */
  21
  22 #include "includes.h"
  23 #include "libcli/raw/libcliraw.h"
  24 #include "libcli/smb2/smb2.h"
  25 #include "libcli/smb2/smb2_calls.h"
  26
  27 #include <gnutls/gnutls.h>
  28 #include <gnutls/crypto.h>
  29 #include "lib/crypto/gnutls_helpers.h"
  30
  31 /*
  32   sign an outgoing message
  33  */
  34 NTSTATUS smb2_sign_message(struct smb2_request_buffer *buf, DATA_BLOB session_key)
  35 {
  36         uint8_t digest[gnutls_hash_get_len(GNUTLS_MAC_SHA256)];
  37         uint64_t session_id;
  38         size_t hdr_offset;
  39         int rc;
  40
  41         if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {
  42                 /* can't sign non-SMB2 messages */
  43                 return NT_STATUS_OK;
  44         }
  45
  46         hdr_offset = buf->hdr - buf->buffer;
  47
  48         session_id = BVAL(buf->hdr, SMB2_HDR_SESSION_ID);
  49         if (session_id == 0) {
  50                 /* we don't sign messages with a zero session_id. See
  51                    MS-SMB2 3.2.4.1.1 */
  52                 return NT_STATUS_OK;
  53         }
  54
  55         if (session_key.length == 0) {
  56                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
  57                          (unsigned)session_key.length));
  58                 return NT_STATUS_ACCESS_DENIED;
  59         }
  60
  61         memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16);
  62
  63         SIVAL(buf->hdr, SMB2_HDR_FLAGS, IVAL(buf->hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
  64
  65         rc = gnutls_hmac_fast(GNUTLS_MAC_SHA256,
  66                               session_key.data,
  67                               MIN(session_key.length, 16),
  68                               buf->hdr,
  69                               buf->size - hdr_offset,
  70                               digest);
  71         if (rc < 0) {
  72                 return gnutls_error_to_ntstatus(rc, NT_STATUS_HMAC_NOT_SUPPORTED);
  73         }
  74
  75         DEBUG(5,("signed SMB2 message of size %u\n", (unsigned)buf->size - NBT_HDR_SIZE));
  76
  77         memcpy(buf->hdr + SMB2_HDR_SIGNATURE, digest, 16);
  78
  79         return NT_STATUS_OK;
  80 }
  81
  82 /*
  83   check an incoming signature
  84  */
  85 NTSTATUS smb2_check_signature(struct smb2_request_buffer *buf, DATA_BLOB session_key)
  86 {
  87         uint64_t session_id;
  88         uint8_t digest[gnutls_hash_get_len(GNUTLS_MAC_SHA256)];
  89         uint8_t sig[16];
  90         size_t hdr_offset;
  91         int rc;
  92
  93         if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {
  94                 /* can't check non-SMB2 messages */
  95                 return NT_STATUS_OK;
  96         }
  97
  98         hdr_offset = buf->hdr - buf->buffer;
  99
 100         session_id = BVAL(buf->hdr, SMB2_HDR_SESSION_ID);
 101         if (session_id == 0) {
 102                 /* don't sign messages with a zero session_id. See
 103                    MS-SMB2 3.2.4.1.1 */
 104                 return NT_STATUS_OK;
 105         }
 106
 107         if (session_key.length == 0) {
 108                 /* we don't have the session key yet */
 109                 return NT_STATUS_OK;
 110         }
 111
 112         memcpy(sig, buf->hdr+SMB2_HDR_SIGNATURE, 16);
 113
 114         memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16);
 115
 116         rc = gnutls_hmac_fast(GNUTLS_MAC_SHA256,
 117                               session_key.data,
 118                               MIN(session_key.length, 16),
 119                               buf->hdr,
 120                               buf->size - hdr_offset,
 121                               digest);
 122         if (rc < 0) {
 123                 return gnutls_error_to_ntstatus(rc, NT_STATUS_HMAC_NOT_SUPPORTED);
 124         }
 125
 126         memcpy(buf->hdr + SMB2_HDR_SIGNATURE, digest, 16);
 127
 128         if (memcmp_const_time(digest, sig, 16) != 0) {
 129                 DEBUG(0,("Bad SMB2 signature for message of size %u\n",
 130                          (unsigned)buf->size-NBT_HDR_SIZE));
 131                 dump_data(0, sig, 16);
 132                 dump_data(0, digest, 16);
 133                 ZERO_ARRAY(digest);
 134                 return NT_STATUS_ACCESS_DENIED;
 135         }
 136         ZERO_ARRAY(digest);
 137
 138         return NT_STATUS_OK;
 139 }