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
  24
  25 /*
  26   sign an outgoing packet
  27 */
  28 void smbsrv_sign_packet(struct smbsrv_request *req)
  29 {
  30 #if 0
  31         /* enable this when packet signing is preventing you working out why valgrind
  32            says that data is uninitialised */
  33         file_save("pkt.dat", req->out.buffer, req->out.size);
  34 #endif
  35
  36         switch (req->smb_conn->signing.signing_state) {
  37         case SMB_SIGNING_ENGINE_OFF:
  38                 break;
  39
  40         case SMB_SIGNING_ENGINE_BSRSPYL:
  41                 /* mark the packet as signed - BEFORE we sign it...*/
  42                 mark_packet_signed(&req->out);
  43
  44                 /* I wonder what BSRSPYL stands for - but this is what MS
  45                    actually sends! */
  46                 memcpy((req->out.hdr + HDR_SS_FIELD), "BSRSPYL ", 8);
  47                 break;
  48
  49         case SMB_SIGNING_ENGINE_ON:
  50
  51                 sign_outgoing_message(&req->out,
  52                                       &req->smb_conn->signing.mac_key,
  53                                       req->seq_num+1);
  54                 break;
  55         }
  56         return;
  57 }
  58
  59
  60
  61 /*
  62   setup the signing key for a connection. Called after authentication succeeds
  63   in a session setup
  64 */
  65 BOOL smbsrv_setup_signing(struct smbsrv_connection *smb_conn,
  66                           DATA_BLOB *session_key,
  67                           DATA_BLOB *response)
  68 {
  69         if (!set_smb_signing_common(&smb_conn->signing)) {
  70                 return False;
  71         }
  72         return smbcli_simple_set_signing(smb_conn,
  73                                          &smb_conn->signing, session_key, response);
  74 }
  75
  76 void smbsrv_signing_restart(struct smbsrv_connection *smb_conn,
  77                             DATA_BLOB *session_key,
  78                             DATA_BLOB *response)
  79 {
  80         if (!smb_conn->signing.seen_valid) {
  81                 DEBUG(5, ("Client did not send a valid signature on "
  82                           "SPNEGO session setup - ignored, expect good next time\n"));
  83                 /* force things back on (most clients do not sign this packet)... */
  84                 smbsrv_setup_signing(smb_conn, session_key, response);
  85                 smb_conn->signing.next_seq_num = 2;
  86                 if (smb_conn->signing.mandatory_signing) {
  87                         DEBUG(5, ("Configured for mandatory signing, 'good packet seen' forced on\n"));
  88                         /* if this is mandatory, then
  89                          * pretend we have seen a
  90                          * valid packet, so we don't
  91                          * turn it off */
  92                         smb_conn->signing.seen_valid = True;
  93                 }
  94         }
  95 }
  96
  97 BOOL smbsrv_init_signing(struct smbsrv_connection *smb_conn)
  98 {
  99         smb_conn->signing.mac_key = data_blob(NULL, 0);
 100         if (!smbcli_set_signing_off(&smb_conn->signing)) {
 101                 return False;
 102         }
 103
 104         switch (lp_server_signing()) {
 105         case SMB_SIGNING_OFF:
 106                 smb_conn->signing.allow_smb_signing = False;
 107                 break;
 108         case SMB_SIGNING_SUPPORTED:
 109                 smb_conn->signing.allow_smb_signing = True;
 110                 break;
 111         case SMB_SIGNING_REQUIRED:
 112                 smb_conn->signing.allow_smb_signing = True;
 113                 smb_conn->signing.mandatory_signing = True;
 114                 break;
 115         case SMB_SIGNING_AUTO:
 116                 if (lp_domain_logons()) {
 117                         smb_conn->signing.allow_smb_signing = True;
 118                 } else {
 119                         smb_conn->signing.allow_smb_signing = False;
 120                 }
 121                 break;
 122         }
 123         return True;
 124 }
 125
 126 /*
 127   allocate a sequence number to a request
 128 */
 129 static void req_signing_alloc_seq_num(struct smbsrv_request *req)
 130 {
 131         req->seq_num = req->smb_conn->signing.next_seq_num;
 132
 133         if (req->smb_conn->signing.signing_state != SMB_SIGNING_ENGINE_OFF) {
 134                 req->smb_conn->signing.next_seq_num += 2;
 135         }
 136 }
 137
 138 /*
 139   called for requests that do not produce a reply of their own
 140 */
 141 void smbsrv_signing_no_reply(struct smbsrv_request *req)
 142 {
 143         if (req->smb_conn->signing.signing_state != SMB_SIGNING_ENGINE_OFF) {
 144                 req->smb_conn->signing.next_seq_num--;
 145         }
 146 }
 147
 148 /***********************************************************
 149  SMB signing - Simple implementation - check a MAC sent by client
 150 ************************************************************/
 151 /**
 152  * Check a packet supplied by the server.
 153  * @return False if we had an established signing connection
 154  *         which had a back checksum, True otherwise
 155  */
 156 BOOL smbsrv_signing_check_incoming(struct smbsrv_request *req)
 157 {
 158         BOOL good;
 159
 160         req_signing_alloc_seq_num(req);
 161
 162         switch (req->smb_conn->signing.signing_state)
 163         {
 164         case SMB_SIGNING_ENGINE_OFF:
 165                 return True;
 166         case SMB_SIGNING_ENGINE_BSRSPYL:
 167         case SMB_SIGNING_ENGINE_ON:
 168         {
 169                 if (req->in.size < (HDR_SS_FIELD + 8)) {
 170                         return False;
 171                 } else {
 172                         good = check_signed_incoming_message(&req->in,
 173                                                              &req->smb_conn->signing.mac_key,
 174                                                              req->seq_num);
 175
 176                         return signing_good(&req->smb_conn->signing,
 177                                             req->seq_num+1, good);
 178                 }
 179         }
 180         }
 181         return False;
 182 }