source4/kdc/kpasswd-service.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3
   4    Samba kpasswd implementation
   5
   6    Copyright (c) 2005      Andrew Bartlett <abartlet@samba.org>
   7    Copyright (c) 2016      Andreas Schneider <asn@samba.org>
   8
   9    This program is free software; you can redistribute it and/or modify
  10    it under the terms of the GNU General Public License as published by
  11    the Free Software Foundation; either version 3 of the License, or
  12    (at your option) any later version.
  13
  14    This program is distributed in the hope that it will be useful,
  15    but WITHOUT ANY WARRANTY; without even the implied warranty of
  16    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17    GNU General Public License for more details.
  18
  19    You should have received a copy of the GNU General Public License
  20    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  21 */
  22
  23 #include "includes.h"
  24 #include "samba/service_task.h"
  25 #include "tsocket/tsocket.h"
  26 #include "auth/credentials/credentials.h"
  27 #include "auth/auth.h"
  28 #include "auth/gensec/gensec.h"
  29 #include "kdc/kdc-server.h"
  30 #include "kdc/kpasswd-service.h"
  31 #include "kdc/kpasswd-helper.h"
  32 #include "param/param.h"
  33
  34 #undef DBGC_CLASS
  35 #define DBGC_CLASS DBGC_KERBEROS
  36
  37 #define HEADER_LEN 6
  38 #ifndef RFC3244_VERSION
  39 #define RFC3244_VERSION 0xff80
  40 #endif
  41
  42 kdc_code kpasswd_process(struct kdc_server *kdc,
  43                          TALLOC_CTX *mem_ctx,
  44                          DATA_BLOB *request,
  45                          DATA_BLOB *reply,
  46                          struct tsocket_address *remote_addr,
  47                          struct tsocket_address *local_addr,
  48                          int datagram)
  49 {
  50         uint16_t len;
  51         uint16_t verno;
  52         uint16_t ap_req_len;
  53         uint16_t enc_data_len;
  54         DATA_BLOB ap_req_blob = data_blob_null;
  55         DATA_BLOB ap_rep_blob = data_blob_null;
  56         DATA_BLOB enc_data_blob = data_blob_null;
  57         DATA_BLOB dec_data_blob = data_blob_null;
  58         DATA_BLOB kpasswd_dec_reply = data_blob_null;
  59         const char *error_string = NULL;
  60         krb5_error_code error_code = 0;
  61         struct cli_credentials *server_credentials;
  62         struct gensec_security *gensec_security;
  63 #ifndef SAMBA4_USES_HEIMDAL
  64         struct sockaddr_storage remote_ss;
  65 #endif
  66         struct sockaddr_storage local_ss;
  67         ssize_t socklen;
  68         TALLOC_CTX *tmp_ctx;
  69         kdc_code rc = KDC_ERROR;
  70         krb5_error_code code = 0;
  71         NTSTATUS status;
  72         int rv;
  73         bool is_inet;
  74         bool ok;
  75
  76         if (kdc->am_rodc) {
  77                 return KDC_PROXY_REQUEST;
  78         }
  79
  80         tmp_ctx = talloc_new(mem_ctx);
  81         if (tmp_ctx == NULL) {
  82                 return KDC_ERROR;
  83         }
  84
  85         is_inet = tsocket_address_is_inet(remote_addr, "ip");
  86         if (!is_inet) {
  87                 DBG_WARNING("Invalid remote IP address\n");
  88                 goto done;
  89         }
  90
  91 #ifndef SAMBA4_USES_HEIMDAL
  92         /*
  93          * FIXME: Heimdal fails to to do a krb5_rd_req() in gensec_krb5 if we
  94          * set the remote address.
  95          */
  96
  97         /* remote_addr */
  98         socklen = tsocket_address_bsd_sockaddr(remote_addr,
  99                                                (struct sockaddr *)&remote_ss,
 100                                                sizeof(struct sockaddr_storage));
 101         if (socklen < 0) {
 102                 DBG_WARNING("Invalid remote IP address\n");
 103                 goto done;
 104         }
 105 #endif
 106
 107         /* local_addr */
 108         socklen = tsocket_address_bsd_sockaddr(local_addr,
 109                                                (struct sockaddr *)&local_ss,
 110                                                sizeof(struct sockaddr_storage));
 111         if (socklen < 0) {
 112                 DBG_WARNING("Invalid local IP address\n");
 113                 goto done;
 114         }
 115
 116         if (request->length <= HEADER_LEN) {
 117                 DBG_WARNING("Request truncated\n");
 118                 goto done;
 119         }
 120
 121         len = RSVAL(request->data, 0);
 122         if (request->length != len) {
 123                 DBG_WARNING("Request length does not match\n");
 124                 goto done;
 125         }
 126
 127         verno = RSVAL(request->data, 2);
 128         if (verno != 1 && verno != RFC3244_VERSION) {
 129                 DBG_WARNING("Unsupported version: 0x%04x\n", verno);
 130         }
 131
 132         ap_req_len = RSVAL(request->data, 4);
 133         if ((ap_req_len >= len) || ((ap_req_len + HEADER_LEN) >= len)) {
 134                 DBG_WARNING("AP_REQ truncated\n");
 135                 goto done;
 136         }
 137
 138         ap_req_blob = data_blob_const(&request->data[HEADER_LEN], ap_req_len);
 139
 140         enc_data_len = len - ap_req_len;
 141         enc_data_blob = data_blob_const(&request->data[HEADER_LEN + ap_req_len],
 142                                         enc_data_len);
 143
 144         server_credentials = cli_credentials_init(tmp_ctx);
 145         if (server_credentials == NULL) {
 146                 DBG_ERR("Failed to initialize server credentials!\n");
 147                 goto done;
 148         }
 149
 150         /*
 151          * We want the credentials subsystem to use the krb5 context we already
 152          * have, rather than a new context.
 153          *
 154          * On this context the KDB plugin has been loaded, so we can access
 155          * dsdb.
 156          */
 157         status = cli_credentials_set_krb5_context(server_credentials,
 158                                                   kdc->smb_krb5_context);
 159         if (!NT_STATUS_IS_OK(status)) {
 160                 goto done;
 161         }
 162
 163         ok = cli_credentials_set_conf(server_credentials, kdc->task->lp_ctx);
 164         if (!ok) {
 165                 goto done;
 166         }
 167
 168         /*
 169          * After calling cli_credentials_set_conf(), explicitly set the realm
 170          * with CRED_SPECIFIED. We need to do this so the result of
 171          * principal_from_credentials() called from the gensec layer is
 172          * CRED_SPECIFIED rather than CRED_SMB_CONF, avoiding a fallback to
 173          * match-by-key (very undesirable in this case).
 174          */
 175         ok = cli_credentials_set_realm(server_credentials,
 176                                        lpcfg_realm(kdc->task->lp_ctx),
 177                                        CRED_SPECIFIED);
 178         if (!ok) {
 179                 goto done;
 180         }
 181
 182         ok = cli_credentials_set_username(server_credentials,
 183                                           "kadmin/changepw",
 184                                           CRED_SPECIFIED);
 185         if (!ok) {
 186                 goto done;
 187         }
 188
 189         /* Check that the server principal is indeed CRED_SPECIFIED. */
 190         {
 191                 char *principal = NULL;
 192                 enum credentials_obtained obtained;
 193
 194                 principal = cli_credentials_get_principal_and_obtained(server_credentials,
 195                                                                        tmp_ctx,
 196                                                                        &obtained);
 197                 if (obtained < CRED_SPECIFIED) {
 198                         goto done;
 199                 }
 200
 201                 TALLOC_FREE(principal);
 202         }
 203
 204         rv = cli_credentials_set_keytab_name(server_credentials,
 205                                              kdc->task->lp_ctx,
 206                                              kdc->kpasswd_keytab_name,
 207                                              CRED_SPECIFIED);
 208         if (rv != 0) {
 209                 DBG_ERR("Failed to set credentials keytab name\n");
 210                 goto done;
 211         }
 212
 213         status = samba_server_gensec_start(tmp_ctx,
 214                                            kdc->task->event_ctx,
 215                                            kdc->task->msg_ctx,
 216                                            kdc->task->lp_ctx,
 217                                            server_credentials,
 218                                            "kpasswd",
 219                                            &gensec_security);
 220         if (!NT_STATUS_IS_OK(status)) {
 221                 goto done;
 222         }
 223
 224         status = gensec_set_local_address(gensec_security, local_addr);
 225         if (!NT_STATUS_IS_OK(status)) {
 226                 goto done;
 227         }
 228
 229 #ifndef SAMBA4_USES_HEIMDAL
 230         status = gensec_set_remote_address(gensec_security, remote_addr);
 231         if (!NT_STATUS_IS_OK(status)) {
 232                 goto done;
 233         }
 234 #endif
 235
 236         /* We want the GENSEC wrap calls to generate PRIV tokens */
 237         gensec_want_feature(gensec_security, GENSEC_FEATURE_SEAL);
 238
 239         /* Use the krb5 gesec mechanism so we can load DB modules */
 240         status = gensec_start_mech_by_name(gensec_security, "krb5");
 241         if (!NT_STATUS_IS_OK(status)) {
 242                 goto done;
 243         }
 244
 245         /*
 246          * Accept the AP-REQ and generate the AP-REP we need for the reply
 247          *
 248          * We only allow KRB5 and make sure the backend to is RPC/IPC free.
 249          *
 250          * See gensec_krb5_update_internal() as GENSEC_SERVER.
 251          *
 252          * It allows gensec_update() not to block.
 253          *
 254          * If that changes in future we need to use
 255          * gensec_update_send/recv here!
 256          */
 257         status = gensec_update(gensec_security, tmp_ctx,
 258                                ap_req_blob, &ap_rep_blob);
 259         if (!NT_STATUS_IS_OK(status) &&
 260             !NT_STATUS_EQUAL(status, NT_STATUS_MORE_PROCESSING_REQUIRED)) {
 261                 ap_rep_blob = data_blob_null;
 262                 error_code = KRB5_KPASSWD_HARDERROR;
 263                 error_string = talloc_asprintf(tmp_ctx,
 264                                                "gensec_update failed - %s\n",
 265                                                nt_errstr(status));
 266                 DBG_ERR("%s", error_string);
 267                 goto reply;
 268         }
 269
 270         status = gensec_unwrap(gensec_security,
 271                                tmp_ctx,
 272                                &enc_data_blob,
 273                                &dec_data_blob);
 274         if (!NT_STATUS_IS_OK(status)) {
 275                 ap_rep_blob = data_blob_null;
 276                 error_code = KRB5_KPASSWD_HARDERROR;
 277                 error_string = talloc_asprintf(tmp_ctx,
 278                                                "gensec_unwrap failed - %s\n",
 279                                                nt_errstr(status));
 280                 DBG_ERR("%s", error_string);
 281                 goto reply;
 282         }
 283
 284         code = kpasswd_handle_request(kdc,
 285                                       tmp_ctx,
 286                                       gensec_security,
 287                                       verno,
 288                                       &dec_data_blob,
 289                                       &kpasswd_dec_reply,
 290                                       &error_string);
 291         if (code != 0) {
 292                 ap_rep_blob = data_blob_null;
 293                 error_code = code;
 294                 goto reply;
 295         }
 296
 297         status = gensec_wrap(gensec_security,
 298                              tmp_ctx,
 299                              &kpasswd_dec_reply,
 300                              &enc_data_blob);
 301         if (!NT_STATUS_IS_OK(status)) {
 302                 ap_rep_blob = data_blob_null;
 303                 error_code = KRB5_KPASSWD_HARDERROR;
 304                 error_string = talloc_asprintf(tmp_ctx,
 305                                                "gensec_wrap failed - %s\n",
 306                                                nt_errstr(status));
 307                 DBG_ERR("%s", error_string);
 308                 goto reply;
 309         }
 310
 311 reply:
 312         if (error_code != 0) {
 313                 krb5_data k_enc_data;
 314                 krb5_data k_dec_data;
 315                 const char *principal_string;
 316                 krb5_principal server_principal;
 317
 318                 if (error_string == NULL) {
 319                         DBG_ERR("Invalid error string! This should not happen\n");
 320                         goto done;
 321                 }
 322
 323                 ok = kpasswd_make_error_reply(tmp_ctx,
 324                                               error_code,
 325                                               error_string,
 326                                               &dec_data_blob);
 327                 if (!ok) {
 328                         DBG_ERR("Failed to create error reply\n");
 329                         goto done;
 330                 }
 331
 332                 k_dec_data = smb_krb5_data_from_blob(dec_data_blob);
 333
 334                 principal_string = cli_credentials_get_principal(server_credentials,
 335                                                                  tmp_ctx);
 336                 if (principal_string == NULL) {
 337                         goto done;
 338                 }
 339
 340                 code = smb_krb5_parse_name(kdc->smb_krb5_context->krb5_context,
 341                                            principal_string,
 342                                            &server_principal);
 343                 if (code != 0) {
 344                         DBG_ERR("Failed to create principal: %s\n",
 345                                 error_message(code));
 346                         goto done;
 347                 }
 348
 349                 code = smb_krb5_mk_error(kdc->smb_krb5_context->krb5_context,
 350                                          KRB5KDC_ERR_NONE + error_code,
 351                                          NULL, /* e_text */
 352                                          &k_dec_data,
 353                                          NULL, /* client */
 354                                          server_principal,
 355                                          &k_enc_data);
 356                 krb5_free_principal(kdc->smb_krb5_context->krb5_context,
 357                                     server_principal);
 358                 if (code != 0) {
 359                         DBG_ERR("Failed to create krb5 error reply: %s\n",
 360                                 error_message(code));
 361                         goto done;
 362                 }
 363
 364                 enc_data_blob = data_blob_talloc(tmp_ctx,
 365                                                  k_enc_data.data,
 366                                                  k_enc_data.length);
 367                 if (enc_data_blob.data == NULL) {
 368                         DBG_ERR("Failed to allocate memory for error reply\n");
 369                         goto done;
 370                 }
 371         }
 372
 373         *reply = data_blob_talloc(mem_ctx,
 374                                   NULL,
 375                                   HEADER_LEN + ap_rep_blob.length + enc_data_blob.length);
 376         if (reply->data == NULL) {
 377                 goto done;
 378         }
 379         RSSVAL(reply->data, 0, reply->length);
 380         RSSVAL(reply->data, 2, 1);
 381         RSSVAL(reply->data, 4, ap_rep_blob.length);
 382         if (ap_rep_blob.data != NULL) {
 383                 memcpy(reply->data + HEADER_LEN,
 384                        ap_rep_blob.data,
 385                        ap_rep_blob.length);
 386         }
 387         memcpy(reply->data + HEADER_LEN + ap_rep_blob.length,
 388                enc_data_blob.data,
 389                enc_data_blob.length);
 390
 391         rc = KDC_OK;
 392 done:
 393         talloc_free(tmp_ctx);
 394         return rc;
 395 }