source3/smbd/seal.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB Transport encryption (sealing) code - server code.
   4    Copyright (C) Jeremy Allison 2007.
   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 "smbd/smbd.h"
  22 #include "smbd/globals.h"
  23 #include "../libcli/auth/spnego.h"
  24 #include "../libcli/smb/smb_seal.h"
  25 #include "../lib/util/asn1.h"
  26 #include "auth.h"
  27 #include "libsmb/libsmb.h"
  28 #include "../lib/tsocket/tsocket.h"
  29 #include "auth/gensec/gensec.h"
  30
  31 /******************************************************************************
  32  Server side encryption.
  33 ******************************************************************************/
  34
  35 /******************************************************************************
  36  Return global enc context - this must change if we ever do multiple contexts.
  37 ******************************************************************************/
  38
  39 static uint16_t srv_enc_ctx(const struct smb_trans_enc_state *es)
  40 {
  41         return es->enc_ctx_num;
  42 }
  43
  44 /******************************************************************************
  45  Is this an incoming encrypted packet ?
  46 ******************************************************************************/
  47
  48 bool is_encrypted_packet(struct smbd_server_connection *sconn,
  49                          const uint8_t *inbuf)
  50 {
  51         NTSTATUS status;
  52         uint16_t enc_num;
  53
  54         /* Ignore non-session messages or non 0xFF'E' messages. */
  55         if(CVAL(inbuf,0)
  56            || (smb_len(inbuf) < 8)
  57            || !(inbuf[4] == 0xFF && inbuf[5] == 'E')) {
  58                 return false;
  59         }
  60
  61         status = get_enc_ctx_num(inbuf, &enc_num);
  62         if (!NT_STATUS_IS_OK(status)) {
  63                 return false;
  64         }
  65
  66         /* Encrypted messages are 0xFF'E'<ctx> */
  67         if (srv_trans_enc_ctx && enc_num == srv_enc_ctx(srv_trans_enc_ctx)) {
  68                 return true;
  69         }
  70         return false;
  71 }
  72
  73 /******************************************************************************
  74  Create an gensec_security and ensure pointer copy is correct.
  75 ******************************************************************************/
  76
  77 static NTSTATUS make_auth_gensec(const struct tsocket_address *remote_address,
  78                                  struct smb_trans_enc_state *es)
  79 {
  80         NTSTATUS status;
  81
  82         status = auth_generic_prepare(es, remote_address,
  83                                       &es->gensec_security);
  84         if (!NT_STATUS_IS_OK(status)) {
  85                 return nt_status_squash(status);
  86         }
  87
  88         gensec_want_feature(es->gensec_security, GENSEC_FEATURE_SEAL);
  89
  90         /*
  91          * We could be accessing the secrets.tdb or krb5.keytab file here.
  92          * ensure we have permissions to do so.
  93          */
  94         become_root();
  95
  96         status = gensec_start_mech_by_oid(es->gensec_security, GENSEC_OID_SPNEGO);
  97
  98         unbecome_root();
  99
 100         if (!NT_STATUS_IS_OK(status)) {
 101                 return nt_status_squash(status);
 102         }
 103
 104         return status;
 105 }
 106
 107 /******************************************************************************
 108  Create a server encryption context.
 109 ******************************************************************************/
 110
 111 static NTSTATUS make_srv_encryption_context(const struct tsocket_address *remote_address,
 112                                             struct smb_trans_enc_state **pp_es)
 113 {
 114         NTSTATUS status;
 115         struct smb_trans_enc_state *es;
 116
 117         *pp_es = NULL;
 118
 119         ZERO_STRUCTP(partial_srv_trans_enc_ctx);
 120         es = talloc_zero(NULL, struct smb_trans_enc_state);
 121         if (!es) {
 122                 return NT_STATUS_NO_MEMORY;
 123         }
 124         status = make_auth_gensec(remote_address,
 125                                   es);
 126         if (!NT_STATUS_IS_OK(status)) {
 127                 TALLOC_FREE(es);
 128                 return status;
 129         }
 130         *pp_es = es;
 131         return NT_STATUS_OK;
 132 }
 133
 134 /******************************************************************************
 135  Free an encryption-allocated buffer.
 136 ******************************************************************************/
 137
 138 void srv_free_enc_buffer(struct smbd_server_connection *sconn, char *buf)
 139 {
 140         /* We know this is an smb buffer, and we
 141          * didn't malloc, only copy, for a keepalive,
 142          * so ignore non-session messages. */
 143
 144         if(CVAL(buf,0)) {
 145                 return;
 146         }
 147
 148         if (srv_trans_enc_ctx) {
 149                 common_free_enc_buffer(srv_trans_enc_ctx, buf);
 150         }
 151 }
 152
 153 /******************************************************************************
 154  Decrypt an incoming buffer.
 155 ******************************************************************************/
 156
 157 NTSTATUS srv_decrypt_buffer(struct smbd_server_connection *sconn, char *buf)
 158 {
 159         /* Ignore non-session messages. */
 160         if(CVAL(buf,0)) {
 161                 return NT_STATUS_OK;
 162         }
 163
 164         if (srv_trans_enc_ctx) {
 165                 return common_decrypt_buffer(srv_trans_enc_ctx, buf);
 166         }
 167
 168         return NT_STATUS_OK;
 169 }
 170
 171 /******************************************************************************
 172  Encrypt an outgoing buffer. Return the encrypted pointer in buf_out.
 173 ******************************************************************************/
 174
 175 NTSTATUS srv_encrypt_buffer(struct smbd_server_connection *sconn, char *buf,
 176                             char **buf_out)
 177 {
 178         *buf_out = buf;
 179
 180         /* Ignore non-session messages. */
 181         if(CVAL(buf,0)) {
 182                 return NT_STATUS_OK;
 183         }
 184
 185         if (srv_trans_enc_ctx) {
 186                 return common_encrypt_buffer(srv_trans_enc_ctx, buf, buf_out);
 187         }
 188         /* Not encrypting. */
 189         return NT_STATUS_OK;
 190 }
 191
 192 /******************************************************************************
 193  Do the SPNEGO encryption negotiation. Parameters are in/out.
 194 ******************************************************************************/
 195
 196 NTSTATUS srv_request_encryption_setup(connection_struct *conn,
 197                                         unsigned char **ppdata,
 198                                         size_t *p_data_size,
 199                                         unsigned char **pparam,
 200                                         size_t *p_param_size)
 201 {
 202         NTSTATUS status;
 203         DATA_BLOB blob = data_blob_const(*ppdata, *p_data_size);
 204         DATA_BLOB response = data_blob_null;
 205         struct smb_trans_enc_state *es;
 206
 207         SAFE_FREE(*pparam);
 208         *p_param_size = 0;
 209
 210         if (!partial_srv_trans_enc_ctx) {
 211                 /* This is the initial step. */
 212                 status = make_srv_encryption_context(conn->sconn->remote_address,
 213                                         &partial_srv_trans_enc_ctx);
 214                 if (!NT_STATUS_IS_OK(status)) {
 215                         return status;
 216                 }
 217         }
 218
 219         es = partial_srv_trans_enc_ctx;
 220         if (!es || es->gensec_security == NULL) {
 221                 TALLOC_FREE(partial_srv_trans_enc_ctx);
 222                 return NT_STATUS_INVALID_PARAMETER;
 223         }
 224
 225         /* Second step. */
 226         become_root();
 227         status = gensec_update(es->gensec_security,
 228                                talloc_tos(), NULL,
 229                                blob, &response);
 230         unbecome_root();
 231         if (!NT_STATUS_EQUAL(status, NT_STATUS_MORE_PROCESSING_REQUIRED) &&
 232             !NT_STATUS_IS_OK(status)) {
 233                 TALLOC_FREE(partial_srv_trans_enc_ctx);
 234                 return nt_status_squash(status);
 235         }
 236
 237         if (NT_STATUS_IS_OK(status)) {
 238                 /* Return the context we're using for this encryption state. */
 239                 if (!(*pparam = SMB_MALLOC_ARRAY(unsigned char, 2))) {
 240                         return NT_STATUS_NO_MEMORY;
 241                 }
 242                 SSVAL(*pparam, 0, es->enc_ctx_num);
 243                 *p_param_size = 2;
 244         }
 245
 246         /* Return the raw blob. */
 247         SAFE_FREE(*ppdata);
 248         *ppdata = (unsigned char *)smb_memdup(response.data, response.length);
 249         if ((*ppdata) == NULL && response.length > 0)
 250                 return NT_STATUS_NO_MEMORY;
 251         *p_data_size = response.length;
 252         data_blob_free(&response);
 253         return status;
 254 }
 255
 256 /******************************************************************************
 257  Negotiation was successful - turn on server-side encryption.
 258 ******************************************************************************/
 259
 260 static NTSTATUS check_enc_good(struct smb_trans_enc_state *es)
 261 {
 262         if (!es) {
 263                 return NT_STATUS_LOGON_FAILURE;
 264         }
 265
 266         if (!gensec_have_feature(es->gensec_security, GENSEC_FEATURE_SIGN)) {
 267                 return NT_STATUS_INVALID_PARAMETER;
 268         }
 269
 270         if (!gensec_have_feature(es->gensec_security, GENSEC_FEATURE_SEAL)) {
 271                 return NT_STATUS_INVALID_PARAMETER;
 272         }
 273         return NT_STATUS_OK;
 274 }
 275
 276 /******************************************************************************
 277  Negotiation was successful - turn on server-side encryption.
 278 ******************************************************************************/
 279
 280 NTSTATUS srv_encryption_start(connection_struct *conn)
 281 {
 282         NTSTATUS status;
 283
 284         /* Check that we are really doing sign+seal. */
 285         status = check_enc_good(partial_srv_trans_enc_ctx);
 286         if (!NT_STATUS_IS_OK(status)) {
 287                 return status;
 288         }
 289         /* Throw away the context we're using currently (if any). */
 290         TALLOC_FREE(srv_trans_enc_ctx);
 291
 292         /* Steal the partial pointer. Deliberate shallow copy. */
 293         srv_trans_enc_ctx = partial_srv_trans_enc_ctx;
 294         srv_trans_enc_ctx->enc_on = true;
 295
 296         partial_srv_trans_enc_ctx = NULL;
 297
 298         DEBUG(1,("srv_encryption_start: context negotiated\n"));
 299         return NT_STATUS_OK;
 300 }
 301
 302 /******************************************************************************
 303  Shutdown all server contexts.
 304 ******************************************************************************/
 305
 306 void server_encryption_shutdown(struct smbd_server_connection *sconn)
 307 {
 308         TALLOC_FREE(partial_srv_trans_enc_ctx);
 309         TALLOC_FREE(srv_trans_enc_ctx);
 310 }