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 bool smbsrv_init_signing(struct smbsrv_connection *smb_conn)
  79 {
  80         enum smb_signing_setting signing_setting;
  81
  82         smb_conn->signing.mac_key = data_blob(NULL, 0);
  83         if (!smbcli_set_signing_off(&smb_conn->signing)) {
  84                 return false;
  85         }
  86
  87         signing_setting = lpcfg_server_signing(smb_conn->lp_ctx);
  88         if (signing_setting == SMB_SIGNING_DEFAULT) {
  89                 /*
  90                  * If we are a domain controller, SMB signing is
  91                  * really important, as it can prevent a number of
  92                  * attacks on communications between us and the
  93                  * clients
  94                  *
  95                  * However, it really sucks (no sendfile, CPU
  96                  * overhead) performance-wise when used on a
  97                  * file server, so disable it by default
  98                  * on non-DCs
  99                  */
 100
 101                 if (lpcfg_server_role(smb_conn->lp_ctx) >= ROLE_DOMAIN_CONTROLLER) {
 102                         signing_setting = SMB_SIGNING_REQUIRED;
 103                 } else {
 104                         signing_setting = SMB_SIGNING_OFF;
 105                 }
 106         }
 107
 108         switch (signing_setting) {
 109         case SMB_SIGNING_DEFAULT:
 110                 smb_panic(__location__);
 111                 break;
 112         case SMB_SIGNING_OFF:
 113                 smb_conn->signing.allow_smb_signing = false;
 114                 break;
 115         case SMB_SIGNING_SUPPORTED:
 116                 smb_conn->signing.allow_smb_signing = true;
 117                 break;
 118         case SMB_SIGNING_REQUIRED:
 119                 smb_conn->signing.allow_smb_signing = true;
 120                 smb_conn->signing.mandatory_signing = true;
 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 }