source4/libcli/raw/smb_signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Signing Code
   4    Copyright (C) Jeremy Allison 2002.
   5    Copyright (C) Andrew Bartlett <abartlet@samba.org> 2002-2003
   6    Copyright (C) James J Myers <myersjj@samba.org> 2003
   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/raw/raw_proto.h"
  25 #include "../lib/crypto/crypto.h"
  26
  27 #include <gnutls/gnutls.h>
  28 #include <gnutls/crypto.h>
  29
  30 /***********************************************************
  31  SMB signing - Common code before we set a new signing implementation
  32 ************************************************************/
  33 bool set_smb_signing_common(struct smb_signing_context *sign_info)
  34 {
  35         if (sign_info->doing_signing) {
  36                 DEBUG(5, ("SMB Signing already in progress, so we don't start it again\n"));
  37                 return false;
  38         }
  39
  40         if (!sign_info->allow_smb_signing) {
  41                 DEBUG(5, ("SMB Signing has been locally disabled\n"));
  42                 return false;
  43         }
  44
  45         return true;
  46 }
  47
  48 void mark_packet_signed(struct smb_request_buffer *out)
  49 {
  50         uint16_t flags2;
  51         flags2 = SVAL(out->hdr, HDR_FLG2);
  52         flags2 |= FLAGS2_SMB_SECURITY_SIGNATURES;
  53         SSVAL(out->hdr, HDR_FLG2, flags2);
  54 }
  55
  56 bool signing_good(struct smb_signing_context *sign_info,
  57                          unsigned int seq, bool good)
  58 {
  59         if (good) {
  60                 if (!sign_info->doing_signing) {
  61                         DEBUG(5, ("Seen valid packet, so turning signing on\n"));
  62                         sign_info->doing_signing = true;
  63                 }
  64                 if (!sign_info->seen_valid) {
  65                         DEBUG(5, ("Seen valid packet, so marking signing as 'seen valid'\n"));
  66                         sign_info->seen_valid = true;
  67                 }
  68         } else {
  69                 if (!sign_info->seen_valid) {
  70                         /* If we have never seen a good packet, just turn it off */
  71                         DEBUG(5, ("signing_good: signing negotiated but not required and peer\n"
  72                                   "isn't sending correct signatures. Turning off.\n"));
  73                         smbcli_set_signing_off(sign_info);
  74                         return true;
  75                 } else {
  76                         /* bad packet after signing started - fail and disconnect. */
  77                         DEBUG(0, ("signing_good: BAD SIG: seq %u\n", seq));
  78                         return false;
  79                 }
  80         }
  81         return true;
  82 }
  83
  84 void sign_outgoing_message(struct smb_request_buffer *out, DATA_BLOB *mac_key, unsigned int seq_num)
  85 {
  86         uint8_t calc_md5_mac[16];
  87         gnutls_hash_hd_t hash_hnd = NULL;
  88         int rc;
  89
  90         /*
  91          * Firstly put the sequence number into the first 4 bytes.
  92          * and zero out the next 4 bytes.
  93          */
  94         SIVAL(out->hdr, HDR_SS_FIELD, seq_num);
  95         SIVAL(out->hdr, HDR_SS_FIELD + 4, 0);
  96
  97         /* mark the packet as signed - BEFORE we sign it...*/
  98         mark_packet_signed(out);
  99
 100         /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 101         rc = gnutls_hash_init(&hash_hnd, GNUTLS_DIG_MD5);
 102         if (rc < 0) {
 103                 return;
 104         }
 105
 106         rc = gnutls_hash(hash_hnd, mac_key->data, mac_key->length);
 107         if (rc < 0) {
 108                 gnutls_hash_deinit(hash_hnd, NULL);
 109                 return;
 110         }
 111         rc = gnutls_hash(hash_hnd,
 112                          out->buffer + NBT_HDR_SIZE,
 113                          out->size - NBT_HDR_SIZE);
 114         if (rc < 0) {
 115                 gnutls_hash_deinit(hash_hnd, NULL);
 116                 return;
 117         }
 118         gnutls_hash_deinit(hash_hnd, calc_md5_mac);
 119
 120         memcpy(&out->hdr[HDR_SS_FIELD], calc_md5_mac, 8);
 121
 122         DEBUG(5, ("sign_outgoing_message: SENT SIG (seq: %d): sent SMB signature of\n",
 123                   seq_num));
 124         dump_data(5, calc_md5_mac, 8);
 125         ZERO_ARRAY(calc_md5_mac);
 126 /*      req->out.hdr[HDR_SS_FIELD+2]=0;
 127         Uncomment this to test if the remote server actually verifies signitures...*/
 128 }
 129
 130 bool check_signed_incoming_message(struct smb_request_buffer *in, DATA_BLOB *mac_key, unsigned int seq_num)
 131 {
 132         bool ok = false;
 133         uint8_t calc_md5_mac[16];
 134         uint8_t *server_sent_mac;
 135         uint8_t sequence_buf[8];
 136         gnutls_hash_hd_t hash_hnd;
 137         const size_t offset_end_of_sig = (HDR_SS_FIELD + 8);
 138         int rc;
 139         int i;
 140         const int sign_range = 0;
 141
 142         /* room enough for the signature? */
 143         if (in->size < NBT_HDR_SIZE + HDR_SS_FIELD + 8) {
 144                 return false;
 145         }
 146
 147         if (!mac_key->length) {
 148                 /* NO key yet */
 149                 return false;
 150         }
 151
 152         /* its quite bogus to be guessing sequence numbers, but very useful
 153            when debugging signing implementations */
 154         for (i = 0-sign_range; i <= 0+sign_range; i++) {
 155                 /*
 156                  * Firstly put the sequence number into the first 4 bytes.
 157                  * and zero out the next 4 bytes.
 158                  */
 159                 SIVAL(sequence_buf, 0, seq_num + i);
 160                 SIVAL(sequence_buf, 4, 0);
 161
 162                 /* get a copy of the server-sent mac */
 163                 server_sent_mac = &in->hdr[HDR_SS_FIELD];
 164
 165                 /* Calculate the 16 byte MAC and place first 8 bytes into the field. */
 166                 rc = gnutls_hash_init(&hash_hnd, GNUTLS_DIG_MD5);
 167                 if (rc < 0) {
 168                         ok = false;
 169                         goto out;
 170                 }
 171
 172                 rc = gnutls_hash(hash_hnd, mac_key->data, mac_key->length);
 173                 if (rc < 0) {
 174                         gnutls_hash_deinit(hash_hnd, NULL);
 175                         ok = false;
 176                         goto out;
 177                 }
 178                 rc = gnutls_hash(hash_hnd, in->hdr, HDR_SS_FIELD);
 179                 if (rc < 0) {
 180                         gnutls_hash_deinit(hash_hnd, NULL);
 181                         ok = false;
 182                         goto out;
 183                 }
 184                 rc = gnutls_hash(hash_hnd, sequence_buf, sizeof(sequence_buf));
 185                 if (rc < 0) {
 186                         gnutls_hash_deinit(hash_hnd, NULL);
 187                         ok = false;
 188                         goto out;
 189                 }
 190                 rc = gnutls_hash(hash_hnd,
 191                                  in->hdr + offset_end_of_sig,
 192                                  in->size - NBT_HDR_SIZE - (offset_end_of_sig));
 193                 if (rc < 0) {
 194                         gnutls_hash_deinit(hash_hnd, NULL);
 195                         ok = false;
 196                         goto out;
 197                 }
 198
 199                 gnutls_hash_deinit(hash_hnd, calc_md5_mac);
 200
 201                 ok = mem_equal_const_time(server_sent_mac, calc_md5_mac, 8);
 202
 203                 if (i == 0) {
 204                         if (!ok) {
 205                                 DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): wanted SMB signature of\n", seq_num + i));
 206                                 dump_data(5, calc_md5_mac, 8);
 207
 208                                 DEBUG(5, ("check_signed_incoming_message: BAD SIG (seq: %d): got SMB signature of\n", seq_num + i));
 209                                 dump_data(5, server_sent_mac, 8);
 210                         } else {
 211                                 DEBUG(15, ("check_signed_incoming_message: GOOD SIG (seq: %d): got SMB signature of\n", seq_num + i));
 212                                 dump_data(5, server_sent_mac, 8);
 213                         }
 214                 }
 215                 ZERO_ARRAY(calc_md5_mac);
 216
 217                 if (ok) break;
 218         }
 219
 220         if (ok && i != 0) {
 221                 DEBUG(0,("SIGNING OFFSET %d (should be %d)\n", i, seq_num));
 222         }
 223
 224 out:
 225         return ok;
 226 }
 227
 228 /**
 229  SMB signing - NULL implementation
 230
 231  @note Used as an initialisation only - it will not correctly
 232        shut down a real signing mechanism
 233 */
 234 bool smbcli_set_signing_off(struct smb_signing_context *sign_info)
 235 {
 236         DEBUG(5, ("Shutdown SMB signing\n"));
 237         sign_info->doing_signing = false;
 238         data_blob_free(&sign_info->mac_key);
 239         sign_info->signing_state = SMB_SIGNING_ENGINE_OFF;
 240         return true;
 241 }
 242
 243 /***********************************************************
 244  SMB signing - Simple implementation - setup the MAC key.
 245 ************************************************************/
 246 bool smbcli_simple_set_signing(TALLOC_CTX *mem_ctx,
 247                                struct smb_signing_context *sign_info,
 248                                const DATA_BLOB *user_session_key,
 249                                const DATA_BLOB *response)
 250 {
 251         if (sign_info->mandatory_signing) {
 252                 DEBUG(5, ("Mandatory SMB signing enabled!\n"));
 253         }
 254
 255         DEBUG(5, ("SMB signing enabled!\n"));
 256
 257         if (response && response->length) {
 258                 sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, response->length + user_session_key->length);
 259         } else {
 260                 sign_info->mac_key = data_blob_talloc(mem_ctx, NULL, user_session_key->length);
 261         }
 262
 263         memcpy(&sign_info->mac_key.data[0], user_session_key->data, user_session_key->length);
 264
 265         if (response && response->length) {
 266                 memcpy(&sign_info->mac_key.data[user_session_key->length],response->data, response->length);
 267         }
 268
 269         dump_data_pw("Started Signing with key:\n", sign_info->mac_key.data, sign_info->mac_key.length);
 270
 271         sign_info->signing_state = SMB_SIGNING_ENGINE_ON;
 272         sign_info->next_seq_num = 2;
 273
 274         return true;
 275 }