source/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 #include "heimdal/lib/hcrypto/sha.h"
  27
  28 /*
  29   NOTE: this code does not yet interoperate with the windows SMB2
  30   implementation. We are waiting on feedback on the docs to find out
  31   why
  32  */
  33
  34
  35 /*
  36   setup signing on a transport
  37  */
  38 NTSTATUS smb2_start_signing(struct smb2_transport *transport)
  39 {
  40         if (transport->signing.session_key.length != 16) {
  41                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
  42                          (unsigned)transport->signing.session_key.length));
  43                 return NT_STATUS_ACCESS_DENIED;
  44         }
  45
  46         transport->signing.signing_started = true;
  47         return NT_STATUS_OK;
  48 }
  49
  50 /*
  51   sign an outgoing message
  52  */
  53 NTSTATUS smb2_sign_message(struct smb2_request *req)
  54 {
  55         struct smb2_request_buffer *buf = &req->out;
  56         uint64_t session_id;
  57         SHA256_CTX m;
  58         uint8_t res[32];
  59
  60         if (!req->transport->signing.doing_signing ||
  61             !req->transport->signing.signing_started) {
  62                 return NT_STATUS_OK;
  63         }
  64
  65         if (buf->size < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {
  66                 /* can't sign non-SMB2 messages */
  67                 return NT_STATUS_OK;
  68         }
  69
  70         session_id = BVAL(buf->hdr, SMB2_HDR_SESSION_ID);
  71         if (session_id == 0) {
  72                 /* we don't sign messages with a zero session_id. See
  73                    MS-SMB2 3.2.4.1.1 */
  74                 return NT_STATUS_OK;
  75         }
  76
  77         if (req->transport->signing.session_key.length != 16) {
  78                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
  79                          (unsigned)req->transport->signing.session_key.length));
  80                 return NT_STATUS_ACCESS_DENIED;
  81         }
  82
  83         memset(buf->hdr + SMB2_HDR_SIGNATURE, 0, 16);
  84
  85         SIVAL(buf->hdr, SMB2_HDR_FLAGS, IVAL(buf->hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
  86
  87         ZERO_STRUCT(m);
  88         SHA256_Init(&m);
  89         SHA256_Update(&m, req->transport->signing.session_key.data,
  90                       req->transport->signing.session_key.length);
  91         SHA256_Update(&m, buf->buffer+NBT_HDR_SIZE, buf->size-NBT_HDR_SIZE);
  92         SHA256_Final(res, &m);
  93
  94         DEBUG(5,("signed SMB2 message of size %u\n", (unsigned)buf->size - NBT_HDR_SIZE));
  95
  96         memcpy(buf->hdr + SMB2_HDR_SIGNATURE, res, 16);
  97
  98         if (DEBUGLVL(5)) {
  99                 /* check our own signature */
 100                 smb2_check_signature(req->transport, buf->buffer, buf->size);
 101         }
 102
 103         return NT_STATUS_OK;
 104 }
 105
 106 /*
 107   check an incoming signature
 108  */
 109 NTSTATUS smb2_check_signature(struct smb2_transport *transport,
 110                               uint8_t *buffer, uint_t length)
 111 {
 112         uint64_t session_id;
 113         SHA256_CTX m;
 114         uint8_t res[SHA256_DIGEST_LENGTH];
 115         uint8_t sig[16];
 116
 117         if (!transport->signing.signing_started ||
 118             !transport->signing.doing_signing) {
 119                 return NT_STATUS_OK;
 120         }
 121
 122         if (length < NBT_HDR_SIZE + SMB2_HDR_SIGNATURE + 16) {
 123                 /* can't check non-SMB2 messages */
 124                 return NT_STATUS_OK;
 125         }
 126
 127         session_id = BVAL(buffer+NBT_HDR_SIZE, SMB2_HDR_SESSION_ID);
 128         if (session_id == 0) {
 129                 /* don't sign messages with a zero session_id. See
 130                    MS-SMB2 3.2.4.1.1 */
 131                 return NT_STATUS_OK;
 132         }
 133
 134         if (transport->signing.session_key.length == 0) {
 135                 /* we don't have the session key yet */
 136                 return NT_STATUS_OK;
 137         }
 138
 139         if (transport->signing.session_key.length != 16) {
 140                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
 141                          (unsigned)transport->signing.session_key.length));
 142                 return NT_STATUS_ACCESS_DENIED;
 143         }
 144
 145         memcpy(sig, buffer+NBT_HDR_SIZE+SMB2_HDR_SIGNATURE, 16);
 146
 147         memset(buffer + NBT_HDR_SIZE + SMB2_HDR_SIGNATURE, 0, 16);
 148
 149         ZERO_STRUCT(m);
 150         SHA256_Init(&m);
 151         SHA256_Update(&m, transport->signing.session_key.data,    16);
 152         SHA256_Update(&m, buffer+NBT_HDR_SIZE, length-NBT_HDR_SIZE);
 153         SHA256_Final(res, &m);
 154
 155         memcpy(buffer+NBT_HDR_SIZE+SMB2_HDR_SIGNATURE, sig, 16);
 156
 157         if (memcmp(res, sig, 16) != 0) {
 158                 DEBUG(0,("Bad SMB2 signature for message of size %u\n", length));
 159                 dump_data(0, sig, 16);
 160                 dump_data(0, res, 16);
 161                 return NT_STATUS_ACCESS_DENIED;
 162         }
 163
 164         return NT_STATUS_OK;
 165 }