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(OM_uint32 major_status,OM_uint32 minor_status,
 254                     int send_packet) {
 255         OM_uint32 lmaj, lmin;
 256         gss_buffer_desc msg = {0,NULL};
 257         OM_uint32 ctx;
 258
 259         ctx = 0;
 260         /* The GSSAPI error */
 261         do {
 262                 lmaj = gss_display_status(&lmin, major_status,
 263                                           GSS_C_GSS_CODE,
 264                                           GSS_C_NULL_OID,
 265                                           &ctx, &msg);
 266                 if (lmaj == GSS_S_COMPLETE) {
 267                         debug((char *)msg.value);
 268                         if (send_packet) packet_send_debug((char *)msg.value);
 269                         (void) gss_release_buffer(&lmin, &msg);
 270                 }
 271         } while (ctx!=0);
 272
 273         /* The mechanism specific error */
 274         do {
 275                 lmaj = gss_display_status(&lmin, minor_status,
 276                                           GSS_C_MECH_CODE,
 277                                           GSS_C_NULL_OID,
 278                                           &ctx, &msg);
 279                 if (lmaj == GSS_S_COMPLETE) {
 280                         debug((char *)msg.value);
 281                         if (send_packet) packet_send_debug((char *)msg.value);
 282                         (void) gss_release_buffer(&lmin, &msg);
 283                 }
 284         } while (ctx!=0);
 285 }
 286
 287 void
 288 ssh_gssapi_error(OM_uint32 major_status,OM_uint32 minor_status) {
 289     ssh_gssapi_error_ex(major_status, minor_status, 0);
 290 }
 291
 292 void
 293 ssh_gssapi_send_error(OM_uint32 major_status,OM_uint32 minor_status) {
 294     ssh_gssapi_error_ex(major_status, minor_status, 1);
 295 }
 296
 297
 298
 299
 300 /* Initialise our GSSAPI context. We use this opaque structure to contain all
 301  * of the data which both the client and server need to persist across
 302  * {accept,init}_sec_context calls, so that when we do it from the userauth
 303  * stuff life is a little easier
 304  */
 305 void
 306 ssh_gssapi_build_ctx(Gssctxt **ctx)
 307 {
 308         *ctx=xmalloc(sizeof (Gssctxt));
 309         (*ctx)->context=GSS_C_NO_CONTEXT;
 310         (*ctx)->name=GSS_C_NO_NAME;
 311         (*ctx)->oid=GSS_C_NO_OID;
 312         (*ctx)->creds=GSS_C_NO_CREDENTIAL;
 313         (*ctx)->client=GSS_C_NO_NAME;
 314         (*ctx)->client_creds=GSS_C_NO_CREDENTIAL;
 315 }
 316
 317 /* Delete our context, providing it has been built correctly */
 318 void
 319 ssh_gssapi_delete_ctx(Gssctxt **ctx)
 320 {
 321         OM_uint32 ms;
 322
 323         /* Return if there's no context */
 324         if ((*ctx)==NULL)
 325                 return;
 326
 327 #if !defined(MECHGLUE) /* mechglue has some memory management issues */
 328         if ((*ctx)->context != GSS_C_NO_CONTEXT)
 329                 gss_delete_sec_context(&ms,&(*ctx)->context,GSS_C_NO_BUFFER);
 330         if ((*ctx)->name != GSS_C_NO_NAME)
 331                 gss_release_name(&ms,&(*ctx)->name);
 332         if ((*ctx)->oid != GSS_C_NO_OID) {
 333                 xfree((*ctx)->oid->elements);
 334                 xfree((*ctx)->oid);
 335                 (*ctx)->oid = GSS_C_NO_OID;
 336         }
 337         if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
 338                 gss_release_cred(&ms,&(*ctx)->creds);
 339         if ((*ctx)->client != GSS_C_NO_NAME)
 340                 gss_release_name(&ms,&(*ctx)->client);
 341         if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
 342                 gss_release_cred(&ms,&(*ctx)->client_creds);
 343 #endif
 344
 345         xfree(*ctx);
 346         *ctx=NULL;
 347 }
 348
 349 /* Wrapper to init_sec_context
 350  * Requires that the context contains:
 351  *      oid
 352  *      server name (from ssh_gssapi_import_name)
 353  */
 354 OM_uint32
 355 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
 356                     gss_buffer_desc* send_tok, OM_uint32 *flags)
 357 {
 358         OM_uint32 maj_status, min_status;
 359         int deleg_flag = 0;
 360
 361         if (deleg_creds) {
 362                 deleg_flag=GSS_C_DELEG_FLAG;
 363                 debug("Delegating credentials");
 364         }
 365
 366         maj_status=gss_init_sec_context(&min_status,
 367                                         GSS_C_NO_CREDENTIAL, /* def. cred */
 368                                         &ctx->context,
 369                                         ctx->name,
 370                                         ctx->oid,
 371                                         GSS_C_MUTUAL_FLAG |
 372                                         GSS_C_INTEG_FLAG |
 373                                         deleg_flag,
 374                                         0, /* default lifetime */
 375                                         NULL, /* no channel bindings */
 376                                         recv_tok,
 377                                         NULL,
 378                                         send_tok,
 379                                         flags,
 380                                         NULL);
 381         ctx->status=maj_status;
 382         if (GSS_ERROR(maj_status)) {
 383                 ssh_gssapi_error(maj_status,min_status);
 384         }
 385         return(maj_status);
 386 }
 387
 388 /* Wrapper arround accept_sec_context
 389  * Requires that the context contains:
 390  *    oid
 391  *    credentials       (from ssh_gssapi_acquire_cred)
 392  */
 393 OM_uint32 ssh_gssapi_accept_ctx(Gssctxt *ctx,gss_buffer_desc *recv_tok,
 394                                 gss_buffer_desc *send_tok, OM_uint32 *flags)
 395 {
 396         OM_uint32 maj_status, min_status;
 397         gss_OID mech;
 398
 399         maj_status=gss_accept_sec_context(&min_status,
 400                                           &ctx->context,
 401                                           ctx->creds,
 402                                           recv_tok,
 403                                           GSS_C_NO_CHANNEL_BINDINGS,
 404                                           &ctx->client,
 405                                           &mech,
 406                                           send_tok,
 407                                           flags,
 408                                           NULL,
 409                                           &ctx->client_creds);
 410         if (GSS_ERROR(maj_status)) {
 411                 ssh_gssapi_send_error(maj_status,min_status);
 412         }
 413
 414         if (ctx->client_creds) {
 415                 debug("Received some client credentials");
 416         } else {
 417                 debug("Got no client credentials");
 418         }
 419
 420         /* FIXME: We should check that the me
 421          * the one that we asked for (in ctx->oid) */
 422
 423         ctx->status=maj_status;
 424
 425         /* Now, if we're complete and we have the right flags, then
 426          * we flag the user as also having been authenticated
 427          */
 428
 429         if (((flags==NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 430                                (*flags & GSS_C_INTEG_FLAG))) &&
 431             (maj_status == GSS_S_COMPLETE)) {
 432                 if (ssh_gssapi_getclient(ctx,&gssapi_client_type,
 433                                          &gssapi_client_name,
 434                                          &gssapi_client_creds))
 435                         fatal("Couldn't convert client name");
 436         }
 437
 438         return(maj_status);
 439 }
 440
 441 /* Create a service name for the given host */
 442 OM_uint32
 443 ssh_gssapi_import_name(Gssctxt *ctx, const char *host) {
 444         gss_buffer_desc gssbuf = {0,NULL};
 445         OM_uint32 maj_status, min_status;
 446         char *xhost;
 447
 448         /* Make a copy of the host name, in case it was returned by a
 449          * previous call to gethostbyname(). */
 450         xhost = xstrdup(host);
 451
 452         /* If xhost is the loopback interface, switch it to our
 453            true local hostname. */
 454         resolve_localhost(&xhost);
 455
 456         /* Make sure we have the FQHN. Some GSSAPI implementations don't do
 457          * this for us themselves */
 458         make_fqhn(&xhost);
 459
 460         gssbuf.length = sizeof("host@")+strlen(xhost);
 461
 462         gssbuf.value = xmalloc(gssbuf.length);
 463         if (gssbuf.value == NULL) {
 464                 xfree(xhost);
 465                 return(-1);
 466         }
 467         snprintf(gssbuf.value,gssbuf.length,"host@%s",xhost);
 468         if ((maj_status=gss_import_name(&min_status,
 469                                         &gssbuf,
 470                                         GSS_C_NT_HOSTBASED_SERVICE,
 471                                         &ctx->name))) {
 472                 ssh_gssapi_error(maj_status,min_status);
 473         }
 474
 475         xfree(xhost);
 476         xfree(gssbuf.value);
 477         return(maj_status);
 478 }
 479
 480 /* Acquire credentials for a server running on the current host.
 481  * Requires that the context structure contains a valid OID
 482  */
 483
 484 /* Returns a GSSAPI error code */
 485 OM_uint32
 486 ssh_gssapi_acquire_cred(Gssctxt *ctx) {
 487         OM_uint32 maj_status, min_status;
 488         char lname[MAXHOSTNAMELEN];
 489         gss_OID_set oidset;
 490
 491         gss_create_empty_oid_set(&min_status,&oidset);
 492         gss_add_oid_set_member(&min_status,ctx->oid,&oidset);
 493
 494         if (gethostname(lname, MAXHOSTNAMELEN)) {
 495                 return(-1);
 496         }
 497
 498         if ((maj_status=ssh_gssapi_import_name(ctx,lname))) {
 499                 return(maj_status);
 500         }
 501         if ((maj_status=gss_acquire_cred(&min_status,
 502                                     ctx->name,
 503                                     0,
 504                                     oidset,
 505                                     GSS_C_ACCEPT,
 506                                     &ctx->creds,
 507                                     NULL,
 508                                     NULL))) {
 509                 ssh_gssapi_error(maj_status,min_status);
 510         }
 511
 512         gss_release_oid_set(&min_status, &oidset);
 513         return(maj_status);
 514 }
 515
 516 /* Extract the client details from a given context. This can only reliably
 517  * be called once for a context */
 518
 519 OM_uint32
 520 ssh_gssapi_getclient(Gssctxt *ctx, enum ssh_gss_id *type,
 521                      gss_buffer_desc *name, gss_cred_id_t *creds) {
 522
 523         OM_uint32 maj_status,min_status;
 524
 525         *type=ssh_gssapi_get_ctype(ctx);
 526         if ((maj_status=gss_display_name(&min_status,ctx->client,name,NULL))) {
 527                 ssh_gssapi_error(maj_status,min_status);
 528         }
 529
 530         /* This is icky. There appears to be no way to copy this structure,
 531          * rather than the pointer to it, so we simply copy the pointer and
 532          * mark the originator as empty so we don't destroy it.
 533          */
 534         *creds=ctx->client_creds;
 535         ctx->client_creds=GSS_C_NO_CREDENTIAL;
 536         return(maj_status);
 537 }
 538
 539 OM_uint32
 540 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_desc *buffer, gss_buffer_desc *hash) {
 541         OM_uint32 maj_status,min_status;
 542
 543         /* ssh1 needs to exchange the hash of the keys */
 544         /* will us this hash to return it */
 545         if (!compat20) {
 546                 if ((maj_status=gss_wrap(&min_status,ctx->context,
 547                                         0,
 548                                         GSS_C_QOP_DEFAULT,
 549                                         buffer,
 550                                         NULL,
 551                                         hash)))
 552                         ssh_gssapi_error(maj_status,min_status);
 553         }
 554         else
 555
 556         if ((maj_status=gss_get_mic(&min_status,ctx->context,
 557                                     GSS_C_QOP_DEFAULT, buffer, hash))) {
 558                 ssh_gssapi_error(maj_status,min_status);
 559         }
 560
 561         return(maj_status);
 562 }
 563
 564 OM_uint32
 565 ssh_gssapi_server_ctx(Gssctxt **ctx,gss_OID oid) {
 566         if (*ctx) ssh_gssapi_delete_ctx(ctx);
 567         ssh_gssapi_build_ctx(ctx);
 568         ssh_gssapi_set_oid(*ctx,oid);
 569         return(ssh_gssapi_acquire_cred(*ctx));
 570 }
 571
 572 OM_uint32
 573 ssh_gssapi_client_ctx(Gssctxt **ctx,gss_OID oid, char *host) {
 574         gss_buffer_desc token = {0,NULL};
 575         OM_uint32 major,minor;
 576
 577         if (*ctx) ssh_gssapi_delete_ctx(ctx);
 578         ssh_gssapi_build_ctx(ctx);
 579         ssh_gssapi_set_oid(*ctx,oid);
 580         ssh_gssapi_import_name(*ctx,host);
 581         major=ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token, NULL);
 582         gss_release_buffer(&minor,&token);
 583         return(major);
 584 }
 585
 586 #endif /* GSSAPI */