source4/smb_server/smb/signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Copyright (C) Andrew Tridgell              2004
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21 #include "smb_server/smb_server.h"
  22 #include "libcli/raw/libcliraw.h"
  23 #include "libcli/raw/raw_proto.h"
  24 #include "param/param.h"
  25
  26
  27 /*
  28   sign an outgoing packet
  29 */
  30 void smbsrv_sign_packet(struct smbsrv_request *req)
  31 {
  32 #if 0
  33         /* enable this when packet signing is preventing you working out why valgrind
  34            says that data is uninitialised */
  35         file_save("pkt.dat", req->out.buffer, req->out.size);
  36 #endif
  37
  38         switch (req->smb_conn->signing.signing_state) {
  39         case SMB_SIGNING_ENGINE_OFF:
  40                 break;
  41
  42         case SMB_SIGNING_ENGINE_BSRSPYL:
  43                 /* mark the packet as signed - BEFORE we sign it...*/
  44                 mark_packet_signed(&req->out);
  45
  46                 /* I wonder what BSRSPYL stands for - but this is what MS
  47                    actually sends! */
  48                 memcpy((req->out.hdr + HDR_SS_FIELD), "BSRSPYL ", 8);
  49                 break;
  50
  51         case SMB_SIGNING_ENGINE_ON:
  52
  53                 sign_outgoing_message(&req->out,
  54                                       &req->smb_conn->signing.mac_key,
  55                                       req->seq_num+1);
  56                 break;
  57         }
  58         return;
  59 }
  60
  61
  62
  63 /*
  64   setup the signing key for a connection. Called after authentication succeeds
  65   in a session setup
  66 */
  67 bool smbsrv_setup_signing(struct smbsrv_connection *smb_conn,
  68                           DATA_BLOB *session_key,
  69                           DATA_BLOB *response)
  70 {
  71         if (!set_smb_signing_common(&smb_conn->signing)) {
  72                 return false;
  73         }
  74         return smbcli_simple_set_signing(smb_conn,
  75                                          &smb_conn->signing, session_key, response);
  76 }
  77
  78 void smbsrv_signing_restart(struct smbsrv_connection *smb_conn,
  79                             DATA_BLOB *session_key,
  80                             DATA_BLOB *response)
  81 {
  82         if (!smb_conn->signing.seen_valid) {
  83                 DEBUG(5, ("Client did not send a valid signature on "
  84                           "SPNEGO session setup - ignored, expect good next time\n"));
  85                 /* force things back on (most clients do not sign this packet)... */
  86                 smbsrv_setup_signing(smb_conn, session_key, response);
  87                 smb_conn->signing.next_seq_num = 2;
  88                 if (smb_conn->signing.mandatory_signing) {
  89                         DEBUG(5, ("Configured for mandatory signing, 'good packet seen' forced on\n"));
  90                         /* if this is mandatory, then
  91                          * pretend we have seen a
  92                          * valid packet, so we don't
  93                          * turn it off */
  94                         smb_conn->signing.seen_valid = true;
  95                 }
  96         }
  97 }
  98
  99 bool smbsrv_init_signing(struct smbsrv_connection *smb_conn)
 100 {
 101         smb_conn->signing.mac_key = data_blob(NULL, 0);
 102         if (!smbcli_set_signing_off(&smb_conn->signing)) {
 103                 return false;
 104         }
 105
 106         switch (lp_server_signing(smb_conn->lp_ctx)) {
 107         case SMB_SIGNING_OFF:
 108                 smb_conn->signing.allow_smb_signing = false;
 109                 break;
 110         case SMB_SIGNING_SUPPORTED:
 111                 smb_conn->signing.allow_smb_signing = true;
 112                 break;
 113         case SMB_SIGNING_REQUIRED:
 114                 smb_conn->signing.allow_smb_signing = true;
 115                 smb_conn->signing.mandatory_signing = true;
 116                 break;
 117         case SMB_SIGNING_AUTO:
 118                 if (lp_server_role(smb_conn->lp_ctx) == ROLE_DOMAIN_CONTROLLER) {
 119                         smb_conn->signing.allow_smb_signing = true;
 120                 } else {
 121                         smb_conn->signing.allow_smb_signing = false;
 122                 }
 123                 break;
 124         }
 125         return true;
 126 }
 127
 128 /*
 129   allocate a sequence number to a request
 130 */
 131 static void req_signing_alloc_seq_num(struct smbsrv_request *req)
 132 {
 133         req->seq_num = req->smb_conn->signing.next_seq_num;
 134
 135         if (req->smb_conn->signing.signing_state != SMB_SIGNING_ENGINE_OFF) {
 136                 req->smb_conn->signing.next_seq_num += 2;
 137         }
 138 }
 139
 140 /*
 141   called for requests that do not produce a reply of their own
 142 */
 143 void smbsrv_signing_no_reply(struct smbsrv_request *req)
 144 {
 145         if (req->smb_conn->signing.signing_state != SMB_SIGNING_ENGINE_OFF) {
 146                 req->smb_conn->signing.next_seq_num--;
 147         }
 148 }
 149
 150 /***********************************************************
 151  SMB signing - Simple implementation - check a MAC sent by client
 152 ************************************************************/
 153 /**
 154  * Check a packet supplied by the server.
 155  * @return false if we had an established signing connection
 156  *         which had a back checksum, true otherwise
 157  */
 158 bool smbsrv_signing_check_incoming(struct smbsrv_request *req)
 159 {
 160         bool good;
 161
 162         req_signing_alloc_seq_num(req);
 163
 164         switch (req->smb_conn->signing.signing_state)
 165         {
 166         case SMB_SIGNING_ENGINE_OFF:
 167                 return true;
 168         case SMB_SIGNING_ENGINE_BSRSPYL:
 169         case SMB_SIGNING_ENGINE_ON:
 170         {
 171                 if (req->in.size < (HDR_SS_FIELD + 8)) {
 172                         return false;
 173                 } else {
 174                         good = check_signed_incoming_message(&req->in,
 175                                                              &req->smb_conn->signing.mac_key,
 176                                                              req->seq_num);
 177
 178                         return signing_good(&req->smb_conn->signing,
 179                                             req->seq_num+1, good);
 180                 }
 181         }
 182         }
 183         return false;
 184 }