openssh/gss-genr.c

   1 /*
   2  * Copyright (c) 2001,2002 Simon Wilkinson. All rights reserved. *
   3  * Redistribution and use in source and binary forms, with or without
   4  * modification, are permitted provided that the following conditions
   5  * are met:
   6  * 1. Redistributions of source code must retain the above copyright
   7  *    notice, this list of conditions and the following disclaimer.
   8  * 2. Redistributions in binary form must reproduce the above copyright
   9  *    notice, this list of conditions and the following disclaimer in the
  10  *    documentation and/or other materials provided with the distribution.
  11  *
  12  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
  13  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  14  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  15  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  16  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  17  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  18  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  19  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  20  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  21  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  22  */
  23
  24 #include "includes.h"
  25
  26 #ifdef GSSAPI
  27
  28 #include "ssh.h"
  29 #include "ssh2.h"
  30 #include "xmalloc.h"
  31 #include "buffer.h"
  32 #include "bufaux.h"
  33 #include "packet.h"
  34 #include "compat.h"
  35 #include <openssl/evp.h>
  36 #include "cipher.h"
  37 #include "kex.h"
  38 #include "log.h"
  39 #include "compat.h"
  40 #include "monitor_wrap.h"
  41 #include "canohost.h"
  42
  43 #include <netdb.h>
  44
  45 #include "ssh-gss.h"
  46
  47 /* Assorted globals for tracking the clients identity once they've
  48  * authenticated */
  49
  50 gss_buffer_desc gssapi_client_name = {0,NULL}; /* Name of our client */
  51 gss_cred_id_t   gssapi_client_creds = GSS_C_NO_CREDENTIAL; /* Their credentials */
  52 enum ssh_gss_id gssapi_client_type = GSS_LAST_ENTRY;
  53
  54 unsigned char ssh1_key_digest[16]; /* used for ssh1 gssapi */
  55
  56 /* The mechanism name used in the list below is defined in the internet
  57  * draft as the Base 64 encoding of the MD5 hash of the ASN.1 DER encoding
  58  * of the underlying GSSAPI mechanism's OID.
  59  *
  60  * Also from the draft, before considering adding SPNEGO, bear in mind that
  61  * "mechanisms ... MUST NOT use SPNEGO as the underlying GSSAPI mechanism"
  62  */
  63
  64 /* These must be in the same order as ssh_gss_id, in ssh-gss.h */
  65
  66 ssh_gssapi_mech supported_mechs[]= {
  67 #ifdef KRB5
  68  /* Official OID - 1.2.850.113554.1.2.2 */
  69  {"Se3H81ismmOC3OE+FwYCiQ==","Kerberos",
  70         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"}},
  71 #endif
  72 #ifdef GSI
  73  /* gssapi_ssleay 1.3.6.1.4.1.3536.1.1 */
  74  {"N3+k7/4wGxHyuP8Yxi4RhA==",
  75   "GSI",
  76   {9, "\x2B\x06\x01\x04\x01\x9B\x50\x01\x01"}
  77  },
  78 #endif /* GSI */
  79  {NULL,NULL,{0,0}}
  80 };
  81
  82 char gssprefix[]=KEX_GSS_SHA1;
  83
  84 /* Return a list of the gss-group1-sha1-x mechanisms supported by this
  85  * program.
  86  *
  87  * We only support the mechanisms that we've indicated in the list above,
  88  * but we check that they're supported by the GSSAPI mechanism on the
  89  * machine. We also check, before including them in the list, that
  90  * we have the necesary information in order to carry out the key exchange
  91  * (that is, that the user has credentials, the server's creds are accessible,
  92  * etc)
  93  *
  94  * The way that this is done is fairly nasty, as we do a lot of work that
  95  * is then thrown away. This should possibly be implemented with a cache
  96  * that stores the results (in an expanded Gssctxt structure), which are
  97  * then used by the first calls if that key exchange mechanism is chosen.
  98  */
  99
 100 char *
 101 ssh_gssapi_mechanisms(int server,char *host) {
 102         gss_OID_set     supported;
 103         OM_uint32       maj_status, min_status;
 104         Buffer          buf;
 105         int             i = 0;
 106         int             present;
 107         int             mech_count=0;
 108         char *          mechs;
 109         Gssctxt *       ctx = NULL;
 110
 111         if (datafellows & SSH_OLD_GSSAPI) return NULL;
 112
 113         gss_indicate_mechs(&min_status, &supported);
 114
 115         buffer_init(&buf);
 116
 117         do {
 118                 if ((maj_status=gss_test_oid_set_member(&min_status,
 119                                                         &supported_mechs[i].oid,
 120                                                         supported,
 121                                                         &present))) {
 122                         present=0;
 123                 }
 124                 if (present) {
 125                         if ((server &&
 126                              !GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctx,
 127                                                             &supported_mechs[i].oid))))
 128                             || (!server &&
 129                                 !GSS_ERROR(ssh_gssapi_client_ctx(&ctx,
 130                                                        &supported_mechs[i].oid,
 131                                                        host)))) {
 132                                 /* Append gss_group1_sha1_x to our list */
 133                                 if (++mech_count > 1) {
 134                                     buffer_append(&buf, ",", 1);
 135                                 }
 136                                 buffer_append(&buf, gssprefix,
 137                                               strlen(gssprefix));
 138                                 buffer_append(&buf,
 139                                               supported_mechs[i].enc_name,
 140                                               strlen(supported_mechs[i].enc_name));
 141                                 debug("GSSAPI mechanism %s (%s%s) supported",
 142                                       supported_mechs[i].name, gssprefix,
 143                                       supported_mechs[i].enc_name);
 144                         } else {
 145                             debug("no credentials for GSSAPI mechanism %s",
 146                                   supported_mechs[i].name);
 147                         }
 148                 } else {
 149                     debug("GSSAPI mechanism %s not supported",
 150                           supported_mechs[i].name);
 151                 }
 152         } while (supported_mechs[++i].name != NULL);
 153
 154         buffer_put_char(&buf,'\0');
 155
 156         mechs=xmalloc(buffer_len(&buf));
 157         buffer_get(&buf,mechs,buffer_len(&buf));
 158         buffer_free(&buf);
 159         if (strlen(mechs)==0)
 160            return(NULL);
 161         else
 162            return(mechs);
 163 }
 164
 165 void ssh_gssapi_supported_oids(gss_OID_set *oidset) {
 166         enum ssh_gss_id i =0;
 167         OM_uint32 maj_status,min_status;
 168         int present;
 169         gss_OID_set supported;
 170
 171         gss_create_empty_oid_set(&min_status,oidset);
 172         gss_indicate_mechs(&min_status, &supported);
 173
 174         while (supported_mechs[i].name!=NULL) {
 175                 if ((maj_status=gss_test_oid_set_member(&min_status,
 176                                                        &supported_mechs[i].oid,
 177                                                        supported,
 178                                                        &present))) {
 179                         present=0;
 180                 }
 181                 if (present) {
 182                         gss_add_oid_set_member(&min_status,
 183                                                &supported_mechs[i].oid,
 184                                                oidset);
 185                 }
 186                 i++;
 187         }
 188 }
 189
 190 /* Set the contexts OID from a data stream */
 191 void ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len) {
 192   if (ctx->oid != GSS_C_NO_OID) {
 193         xfree(ctx->oid->elements);
 194         xfree(ctx->oid);
 195   }
 196   ctx->oid=xmalloc(sizeof(gss_OID_desc));
 197   ctx->oid->length=len;
 198   ctx->oid->elements=xmalloc(len);
 199   memcpy(ctx->oid->elements,data,len);
 200 }
 201
 202 /* Set the contexts OID */
 203 void ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid) {
 204   ssh_gssapi_set_oid_data(ctx,oid->elements,oid->length);
 205 }
 206
 207 /* Find out which GSS type (out of the list we define in ssh-gss.h) a
 208  * particular connection is using
 209  */
 210 enum ssh_gss_id ssh_gssapi_get_ctype(Gssctxt *ctxt) {
 211         enum ssh_gss_id i=0;
 212
 213         while(supported_mechs[i].name!=NULL) {
 214            if (supported_mechs[i].oid.length == ctxt->oid->length &&
 215                (memcmp(supported_mechs[i].oid.elements,
 216                        ctxt->oid->elements,ctxt->oid->length) == 0))
 217                return i;
 218            i++;
 219         }
 220         return(GSS_LAST_ENTRY);
 221 }
 222
 223 /* Set the GSS context's OID to the oid indicated by the given key exchange
 224  * name. */
 225 gss_OID ssh_gssapi_id_kex(Gssctxt *ctx, char *name) {
 226   enum ssh_gss_id i=0;
 227
 228   if (strncmp(name, gssprefix, strlen(gssprefix)-1) !=0) {
 229      return(NULL);
 230   }
 231
 232   name+=strlen(gssprefix); /* Move to the start of the MIME string */
 233
 234   while (supported_mechs[i].name!=NULL &&
 235          strcmp(name,supported_mechs[i].enc_name)!=0) {
 236         i++;
 237   }
 238
 239   if (supported_mechs[i].name==NULL)
 240      return (NULL);
 241
 242   if (ctx) ssh_gssapi_set_oid(ctx,&supported_mechs[i].oid);
 243
 244   debug("using GSSAPI mechanism %s (%s%s)", supported_mechs[i].name,
 245         gssprefix, supported_mechs[i].enc_name);
 246
 247   return &supported_mechs[i].oid;
 248 }
 249
 250
 251 /* All this effort to report an error ... */
 252 static void
 253 ssh_gssapi_error_ex(gss_OID mech, OM_uint32 major_status,
 254                     OM_uint32 minor_status,
 255                     int send_packet) {
 256         OM_uint32 lmaj, lmin;
 257         gss_buffer_desc msg = {0,NULL};
 258         OM_uint32 ctx;
 259
 260         ctx = 0;
 261         /* The GSSAPI error */
 262         do {
 263                 lmaj = gss_display_status(&lmin, major_status,
 264                                           GSS_C_GSS_CODE,
 265                                           mech,
 266                                           &ctx, &msg);
 267                 if (lmaj == GSS_S_COMPLETE) {
 268                         debug((char *)msg.value);
 269                         if (send_packet) packet_send_debug((char *)msg.value);
 270                         (void) gss_release_buffer(&lmin, &msg);
 271                 }
 272         } while (ctx!=0);
 273
 274         /* The mechanism specific error */
 275         do {
 276                 lmaj = gss_display_status(&lmin, minor_status,
 277                                           GSS_C_MECH_CODE,
 278                                           mech,
 279                                           &ctx, &msg);
 280                 if (lmaj == GSS_S_COMPLETE) {
 281                         debug((char *)msg.value);
 282                         if (send_packet) packet_send_debug((char *)msg.value);
 283                         (void) gss_release_buffer(&lmin, &msg);
 284                 }
 285         } while (ctx!=0);
 286 }
 287
 288 void
 289 ssh_gssapi_error(gss_OID mech,OM_uint32 major_status,OM_uint32 minor_status) {
 290     ssh_gssapi_error_ex(mech, major_status, minor_status, 0);
 291 }
 292
 293 void
 294 ssh_gssapi_send_error(gss_OID mech,
 295                       OM_uint32 major_status,OM_uint32 minor_status) {
 296     ssh_gssapi_error_ex(mech, major_status, minor_status, 1);
 297 }
 298
 299
 300
 301
 302 /* Initialise our GSSAPI context. We use this opaque structure to contain all
 303  * of the data which both the client and server need to persist across
 304  * {accept,init}_sec_context calls, so that when we do it from the userauth
 305  * stuff life is a little easier
 306  */
 307 void
 308 ssh_gssapi_build_ctx(Gssctxt **ctx)
 309 {
 310         *ctx=xmalloc(sizeof (Gssctxt));
 311         (*ctx)->context=GSS_C_NO_CONTEXT;
 312         (*ctx)->name=GSS_C_NO_NAME;
 313         (*ctx)->oid=GSS_C_NO_OID;
 314         (*ctx)->creds=GSS_C_NO_CREDENTIAL;
 315         (*ctx)->client=GSS_C_NO_NAME;
 316         (*ctx)->client_creds=GSS_C_NO_CREDENTIAL;
 317 }
 318
 319 /* Delete our context, providing it has been built correctly */
 320 void
 321 ssh_gssapi_delete_ctx(Gssctxt **ctx)
 322 {
 323         OM_uint32 ms;
 324
 325         /* Return if there's no context */
 326         if ((*ctx)==NULL)
 327                 return;
 328
 329 #if !defined(MECHGLUE) /* mechglue has some memory management issues */
 330         if ((*ctx)->context != GSS_C_NO_CONTEXT)
 331                 gss_delete_sec_context(&ms,&(*ctx)->context,GSS_C_NO_BUFFER);
 332         if ((*ctx)->name != GSS_C_NO_NAME)
 333                 gss_release_name(&ms,&(*ctx)->name);
 334         if ((*ctx)->oid != GSS_C_NO_OID) {
 335                 xfree((*ctx)->oid->elements);
 336                 xfree((*ctx)->oid);
 337                 (*ctx)->oid = GSS_C_NO_OID;
 338         }
 339         if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
 340                 gss_release_cred(&ms,&(*ctx)->creds);
 341         if ((*ctx)->client != GSS_C_NO_NAME)
 342                 gss_release_name(&ms,&(*ctx)->client);
 343         if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
 344                 gss_release_cred(&ms,&(*ctx)->client_creds);
 345 #endif
 346
 347         xfree(*ctx);
 348         *ctx=NULL;
 349 }
 350
 351 /* Wrapper to init_sec_context
 352  * Requires that the context contains:
 353  *      oid
 354  *      server name (from ssh_gssapi_import_name)
 355  */
 356 OM_uint32
 357 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
 358                     gss_buffer_desc* send_tok, OM_uint32 *flags)
 359 {
 360         OM_uint32 maj_status, min_status;
 361         int deleg_flag = 0;
 362
 363         if (deleg_creds) {
 364                 deleg_flag=GSS_C_DELEG_FLAG;
 365                 debug("Delegating credentials");
 366         }
 367
 368         maj_status=gss_init_sec_context(&min_status,
 369                                         GSS_C_NO_CREDENTIAL, /* def. cred */
 370                                         &ctx->context,
 371                                         ctx->name,
 372                                         ctx->oid,
 373                                         GSS_C_MUTUAL_FLAG |
 374                                         GSS_C_INTEG_FLAG |
 375                                         deleg_flag,
 376                                         0, /* default lifetime */
 377                                         NULL, /* no channel bindings */
 378                                         recv_tok,
 379                                         NULL,
 380                                         send_tok,
 381                                         flags,
 382                                         NULL);
 383         ctx->status=maj_status;
 384         if (GSS_ERROR(maj_status)) {
 385                 ssh_gssapi_error(ctx->oid,maj_status,min_status);
 386         }
 387         return(maj_status);
 388 }
 389
 390 /* Wrapper arround accept_sec_context
 391  * Requires that the context contains:
 392  *    oid
 393  *    credentials       (from ssh_gssapi_acquire_cred)
 394  */
 395 OM_uint32 ssh_gssapi_accept_ctx(Gssctxt *ctx,gss_buffer_desc *recv_tok,
 396                                 gss_buffer_desc *send_tok, OM_uint32 *flags)
 397 {
 398         OM_uint32 maj_status, min_status;
 399
 400         maj_status=gss_accept_sec_context(&min_status,
 401                                           &ctx->context,
 402                                           ctx->creds,
 403                                           recv_tok,
 404                                           GSS_C_NO_CHANNEL_BINDINGS,
 405                                           &ctx->client,
 406                                           &ctx->oid,
 407                                           send_tok,
 408                                           flags,
 409                                           NULL,
 410                                           &ctx->client_creds);
 411         if (GSS_ERROR(maj_status)) {
 412                 ssh_gssapi_send_error(ctx->oid,maj_status,min_status);
 413         }
 414
 415         if (ctx->client_creds) {
 416                 debug("Received some client credentials");
 417         } else {
 418                 debug("Got no client credentials");
 419         }
 420
 421         /* FIXME: We should check that the me
 422          * the one that we asked for (in ctx->oid) */
 423
 424         ctx->status=maj_status;
 425
 426         /* Now, if we're complete and we have the right flags, then
 427          * we flag the user as also having been authenticated
 428          */
 429
 430         if (((flags==NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 431                                (*flags & GSS_C_INTEG_FLAG))) &&
 432             (maj_status == GSS_S_COMPLETE)) {
 433                 if (ssh_gssapi_getclient(ctx,&gssapi_client_type,
 434                                          &gssapi_client_name,
 435                                          &gssapi_client_creds))
 436                         fatal("Couldn't convert client name");
 437         }
 438
 439         return(maj_status);
 440 }
 441
 442 /* Create a service name for the given host */
 443 OM_uint32
 444 ssh_gssapi_import_name(Gssctxt *ctx, const char *host) {
 445         gss_buffer_desc gssbuf = {0,NULL};
 446         OM_uint32 maj_status, min_status;
 447         char *xhost;
 448
 449         /* Make a copy of the host name, in case it was returned by a
 450          * previous call to gethostbyname(). */
 451         xhost = xstrdup(host);
 452
 453         /* If xhost is the loopback interface, switch it to our
 454            true local hostname. */
 455         resolve_localhost(&xhost);
 456
 457         /* Make sure we have the FQHN. Some GSSAPI implementations don't do
 458          * this for us themselves */
 459         make_fqhn(&xhost);
 460
 461         gssbuf.length = sizeof("host@")+strlen(xhost);
 462
 463         gssbuf.value = xmalloc(gssbuf.length);
 464         if (gssbuf.value == NULL) {
 465                 xfree(xhost);
 466                 return(-1);
 467         }
 468         snprintf(gssbuf.value,gssbuf.length,"host@%s",xhost);
 469         if ((maj_status=gss_import_name(&min_status,
 470                                         &gssbuf,
 471                                         GSS_C_NT_HOSTBASED_SERVICE,
 472                                         &ctx->name))) {
 473                 ssh_gssapi_error(ctx->oid, maj_status,min_status);
 474         }
 475
 476         xfree(xhost);
 477         xfree(gssbuf.value);
 478         return(maj_status);
 479 }
 480
 481 /* Acquire credentials for a server running on the current host.
 482  * Requires that the context structure contains a valid OID
 483  */
 484
 485 /* Returns a GSSAPI error code */
 486 OM_uint32
 487 ssh_gssapi_acquire_cred(Gssctxt *ctx) {
 488         OM_uint32 maj_status, min_status;
 489         char lname[MAXHOSTNAMELEN];
 490         gss_OID_set oidset;
 491
 492         gss_create_empty_oid_set(&min_status,&oidset);
 493         gss_add_oid_set_member(&min_status,ctx->oid,&oidset);
 494
 495         if (gethostname(lname, MAXHOSTNAMELEN)) {
 496                 return(-1);
 497         }
 498
 499         if ((maj_status=ssh_gssapi_import_name(ctx,lname))) {
 500                 return(maj_status);
 501         }
 502         if ((maj_status=gss_acquire_cred(&min_status,
 503                                     ctx->name,
 504                                     0,
 505                                     oidset,
 506                                     GSS_C_ACCEPT,
 507                                     &ctx->creds,
 508                                     NULL,
 509                                     NULL))) {
 510                 ssh_gssapi_error(GSS_C_NO_OID,maj_status,min_status);
 511         }
 512
 513         gss_release_oid_set(&min_status, &oidset);
 514         return(maj_status);
 515 }
 516
 517 /* Extract the client details from a given context. This can only reliably
 518  * be called once for a context */
 519
 520 OM_uint32
 521 ssh_gssapi_getclient(Gssctxt *ctx, enum ssh_gss_id *type,
 522                      gss_buffer_desc *name, gss_cred_id_t *creds) {
 523
 524         OM_uint32 maj_status,min_status;
 525
 526         *type=ssh_gssapi_get_ctype(ctx);
 527         if ((maj_status=gss_display_name(&min_status,ctx->client,name,NULL))) {
 528                 ssh_gssapi_error(GSS_C_NO_OID,maj_status,min_status);
 529         }
 530
 531         /* This is icky. There appears to be no way to copy this structure,
 532          * rather than the pointer to it, so we simply copy the pointer and
 533          * mark the originator as empty so we don't destroy it.
 534          */
 535         *creds=ctx->client_creds;
 536         ctx->client_creds=GSS_C_NO_CREDENTIAL;
 537         return(maj_status);
 538 }
 539
 540 OM_uint32
 541 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_desc *buffer, gss_buffer_desc *hash) {
 542         OM_uint32 maj_status,min_status;
 543
 544         /* ssh1 needs to exchange the hash of the keys */
 545         /* will us this hash to return it */
 546         if (!compat20) {
 547                 if ((maj_status=gss_wrap(&min_status,ctx->context,
 548                                         0,
 549                                         GSS_C_QOP_DEFAULT,
 550                                         buffer,
 551                                         NULL,
 552                                         hash)))
 553                         ssh_gssapi_error(ctx->oid,maj_status,min_status);
 554         }
 555         else
 556
 557         if ((maj_status=gss_get_mic(&min_status,ctx->context,
 558                                     GSS_C_QOP_DEFAULT, buffer, hash))) {
 559                 ssh_gssapi_error(ctx->oid,maj_status,min_status);
 560         }
 561
 562         return(maj_status);
 563 }
 564
 565 OM_uint32
 566 ssh_gssapi_server_ctx(Gssctxt **ctx,gss_OID oid) {
 567         if (*ctx) ssh_gssapi_delete_ctx(ctx);
 568         ssh_gssapi_build_ctx(ctx);
 569         ssh_gssapi_set_oid(*ctx,oid);
 570         return(ssh_gssapi_acquire_cred(*ctx));
 571 }
 572
 573 OM_uint32
 574 ssh_gssapi_client_ctx(Gssctxt **ctx,gss_OID oid, char *host) {
 575         gss_buffer_desc token = {0,NULL};
 576         OM_uint32 major,minor;
 577
 578         if (*ctx) ssh_gssapi_delete_ctx(ctx);
 579         ssh_gssapi_build_ctx(ctx);
 580         ssh_gssapi_set_oid(*ctx,oid);
 581         ssh_gssapi_import_name(*ctx,host);
 582         major=ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, NULL);
 583         gss_release_buffer(&minor,&token);
 584         return(major);
 585 }
 586
 587 #endif /* GSSAPI */