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