openssh/gss-genr.c

   1 /*
   2  * Copyright (c) 2001 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
  41 #include <netdb.h>
  42
  43 #include "ssh-gss.h"
  44
  45 /* Assorted globals for tracking the clients identity once they've
  46  * authenticated */
  47
  48 gss_buffer_desc gssapi_client_name = {0,NULL}; /* Name of our client */
  49 gss_cred_id_t   gssapi_client_creds = GSS_C_NO_CREDENTIAL; /* Their credentials */
  50 enum ssh_gss_id gssapi_client_type = GSS_LAST_ENTRY;
  51
  52 /* The mechanism name used in the list below is defined in the internet
  53  * draft as the Base 64 encoding of the MD5 hash of the ASN.1 DER encoding
  54  * of the underlying GSSAPI mechanism's OID.
  55  *
  56  * Also from the draft, before considering adding SPNEGO, bear in mind that
  57  * "mechanisms ... MUST NOT use SPNEGO as the underlying GSSAPI mechanism"
  58  */
  59
  60 /* These must be in the same order as ssh_gss_id, in ssh-gss.h */
  61
  62 ssh_gssapi_mech supported_mechs[]= {
  63 #ifdef KRB5
  64  /* Official OID - 1.2.850.113554.1.2.2 */
  65  {"Se3H81ismmOC3OE+FwYCiQ==","Kerberos",
  66         {9, "\x2A\x86\x48\x86\xF7\x12\x01\x02\x02"}},
  67 #endif
  68 #ifdef GSI
  69  /* gssapi_ssleay 1.3.6.1.4.1.3536.1.1 */
  70  {"N3+k7/4wGxHyuP8Yxi4RhA==",
  71   "GSI",
  72   {9, "\x2B\x06\x01\x04\x01\x9B\x50\x01\x01"}
  73  },
  74 #endif /* GSI */
  75  {NULL,NULL,{0,0}}
  76 };
  77
  78 char gssprefix[]=KEX_GSS_SHA1;
  79
  80 /* Return a list of the gss-group1-sha1-x mechanisms supported by this
  81  * program.
  82  *
  83  * We only support the mechanisms that we've indicated in the list above,
  84  * but we check that they're supported by the GSSAPI mechanism on the
  85  * machine. We also check, before including them in the list, that
  86  * we have the necesary information in order to carry out the key exchange
  87  * (that is, that the user has credentials, the server's creds are accessible,
  88  * etc)
  89  *
  90  * The way that this is done is fairly nasty, as we do a lot of work that
  91  * is then thrown away. This should possibly be implemented with a cache
  92  * that stores the results (in an expanded Gssctxt structure), which are
  93  * then used by the first calls if that key exchange mechanism is chosen.
  94  */
  95
  96 char *
  97 ssh_gssapi_mechanisms(int server,char *host) {
  98         gss_OID_set     supported;
  99         OM_uint32       maj_status, min_status;
 100         Buffer          buf;
 101         int             i = 0;
 102         int             present;
 103         char *          mechs;
 104         Gssctxt         ctx;
 105         gss_buffer_desc token;
 106
 107         if (datafellows & SSH_OLD_GSSAPI) return NULL;
 108
 109         gss_indicate_mechs(&min_status, &supported);
 110
 111         buffer_init(&buf);
 112
 113         do {
 114                 if ((maj_status=gss_test_oid_set_member(&min_status,
 115                                                         &supported_mechs[i].oid,
 116                                                         supported,
 117                                                         &present))) {
 118                         present=0;
 119                 }
 120                 if (present) {
 121                         ssh_gssapi_build_ctx(&ctx);
 122                         ssh_gssapi_set_oid(&ctx,&supported_mechs[i].oid);
 123                         if (server) {
 124                                 if (ssh_gssapi_acquire_cred(&ctx)) {
 125                                         ssh_gssapi_delete_ctx(&ctx);
 126                                         continue;
 127                                 }
 128                         }
 129                         else { /* client */
 130                                 if (ssh_gssapi_import_name(&ctx,host))
 131                                         continue;
 132                                 maj_status=ssh_gssapi_init_ctx(&ctx, 0,
 133                                                                GSS_C_NO_BUFFER,
 134                                                                &token,
 135                                                                NULL);
 136                                 ssh_gssapi_delete_ctx(&ctx);
 137                                 if (GSS_ERROR(maj_status)) {
 138                                         continue;
 139                                 }
 140                         }
 141
 142                         /* Append gss_group1_sha1_x to our list */
 143                         buffer_append(&buf, gssprefix,
 144                                       strlen(gssprefix));
 145                         buffer_append(&buf, supported_mechs[i].enc_name,
 146                                       strlen(supported_mechs[i].enc_name));
 147                 }
 148         } while (supported_mechs[++i].name != NULL);
 149
 150         buffer_put_char(&buf,'\0');
 151
 152         mechs=xmalloc(buffer_len(&buf));
 153         buffer_get(&buf,mechs,buffer_len(&buf));
 154         buffer_free(&buf);
 155         if (strlen(mechs)==0)
 156            return(NULL);
 157         else
 158            return(mechs);
 159 }
 160
 161 void ssh_gssapi_supported_oids(gss_OID_set *oidset) {
 162         enum ssh_gss_id i =0;
 163         OM_uint32 maj_status,min_status;
 164         int present;
 165         gss_OID_set supported;
 166
 167         gss_create_empty_oid_set(&min_status,oidset);
 168         gss_indicate_mechs(&min_status, &supported);
 169
 170         while (supported_mechs[i].name!=NULL) {
 171                 if ((maj_status=gss_test_oid_set_member(&min_status,
 172                                                        &supported_mechs[i].oid,
 173                                                        supported,
 174                                                        &present))) {
 175                         present=0;
 176                 }
 177                 if (present) {
 178                         gss_add_oid_set_member(&min_status,
 179                                                &supported_mechs[i].oid,
 180                                                oidset);
 181                 }
 182                 i++;
 183         }
 184 }
 185
 186 /* Set the contexts OID from a data stream */
 187 void ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len) {
 188   if (ctx->oid != GSS_C_NO_OID) {
 189         xfree(ctx->oid->elements);
 190         xfree(ctx->oid);
 191   }
 192   ctx->oid=xmalloc(sizeof(gss_OID_desc));
 193   ctx->oid->length=len;
 194   ctx->oid->elements=xmalloc(len);
 195   memcpy(ctx->oid->elements,data,len);
 196 }
 197
 198 /* Set the contexts OID */
 199 void ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid) {
 200   ssh_gssapi_set_oid_data(ctx,oid->elements,oid->length);
 201 }
 202
 203 /* Find out which GSS type (out of the list we define in ssh-gss.h) a
 204  * particular connection is using
 205  */
 206 enum ssh_gss_id ssh_gssapi_get_ctype(Gssctxt *ctxt) {
 207         enum ssh_gss_id i=0;
 208
 209         while(supported_mechs[i].name!=NULL &&
 210                 supported_mechs[i].oid.length != ctxt->oid->length &&
 211                 (memcmp(supported_mechs[i].oid.elements,
 212                        ctxt->oid->elements,ctxt->oid->length) !=0)) {
 213            i++;
 214         }
 215         return(i);
 216 }
 217
 218 /* Set the GSS context's OID to the oid indicated by the given key exchange
 219  * name. */
 220 int ssh_gssapi_id_kex(Gssctxt *ctx, char *name) {
 221   enum ssh_gss_id i=0;
 222
 223   if (strncmp(name, gssprefix, strlen(gssprefix)-1) !=0) {
 224      return(1);
 225   }
 226
 227   name+=strlen(gssprefix); /* Move to the start of the MIME string */
 228
 229   while (supported_mechs[i].name!=NULL &&
 230          strcmp(name,supported_mechs[i].enc_name)!=0) {
 231         i++;
 232   }
 233
 234   if (supported_mechs[i].name==NULL)
 235      return (1);
 236
 237   ssh_gssapi_set_oid(ctx,&supported_mechs[i].oid);
 238
 239   return 0;
 240 }
 241
 242
 243 /* All this effort to report an error ... */
 244 void
 245 ssh_gssapi_error(OM_uint32 major_status,OM_uint32 minor_status) {
 246         OM_uint32 lmaj, lmin;
 247         gss_buffer_desc msg;
 248         OM_uint32 ctx;
 249
 250         ctx = 0;
 251         /* The GSSAPI error */
 252         do {
 253                 lmaj = gss_display_status(&lmin, major_status,
 254                                           GSS_C_GSS_CODE,
 255                                           GSS_C_NULL_OID,
 256                                           &ctx, &msg);
 257                 if (lmaj == GSS_S_COMPLETE) {
 258                         debug((char *)msg.value);
 259                         (void) gss_release_buffer(&lmin, &msg);
 260                 }
 261         } while (ctx!=0);
 262
 263         /* The mechanism specific error */
 264         do {
 265                 lmaj = gss_display_status(&lmin, minor_status,
 266                                           GSS_C_MECH_CODE,
 267                                           GSS_C_NULL_OID,
 268                                           &ctx, &msg);
 269                 if (lmaj == GSS_S_COMPLETE) {
 270                         debug((char *)msg.value);
 271                         (void) gss_release_buffer(&lmin, &msg);
 272                 }
 273         } while (ctx!=0);
 274 }
 275
 276 /* Initialise our GSSAPI context. We use this opaque structure to contain all
 277  * of the data which both the client and server need to persist across
 278  * {accept,init}_sec_context calls, so that when we do it from the userauth
 279  * stuff life is a little easier
 280  */
 281 void
 282 ssh_gssapi_build_ctx(Gssctxt *ctx)
 283 {
 284         ctx->context=GSS_C_NO_CONTEXT;
 285         ctx->name=GSS_C_NO_NAME;
 286         ctx->oid=GSS_C_NO_OID;
 287         ctx->creds=GSS_C_NO_CREDENTIAL;
 288         ctx->client=GSS_C_NO_NAME;
 289         ctx->client_creds=GSS_C_NO_CREDENTIAL;
 290 }
 291
 292 /* Delete our context, providing it has been built correctly */
 293 void
 294 ssh_gssapi_delete_ctx(Gssctxt *ctx)
 295 {
 296         OM_uint32 ms;
 297
 298         if (ctx->context != GSS_C_NO_CONTEXT)
 299                 gss_delete_sec_context(&ms,&ctx->context,GSS_C_NO_BUFFER);
 300         if (ctx->name != GSS_C_NO_NAME)
 301                 gss_release_name(&ms,&ctx->name);
 302         if (ctx->oid != GSS_C_NO_OID) {
 303                 xfree(ctx->oid->elements);
 304                 xfree(ctx->oid);
 305                 ctx->oid = GSS_C_NO_OID;
 306         }
 307         if (ctx->creds != GSS_C_NO_CREDENTIAL)
 308                 gss_release_cred(&ms,&ctx->creds);
 309         if (ctx->client != GSS_C_NO_NAME)
 310                 gss_release_name(&ms,&ctx->client);
 311         if (ctx->client_creds != GSS_C_NO_CREDENTIAL)
 312                 gss_release_cred(&ms,&ctx->client_creds);
 313 }
 314
 315 /* Wrapper to init_sec_context
 316  * Requires that the context contains:
 317  *      oid
 318  *      server name (from ssh_gssapi_import_name)
 319  */
 320 OM_uint32
 321 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
 322                     gss_buffer_desc* send_tok, OM_uint32 *flags)
 323 {
 324         OM_uint32 maj_status, min_status;
 325         int deleg_flag = 0;
 326
 327         if (deleg_creds) {
 328                 deleg_flag=GSS_C_DELEG_FLAG;
 329                 debug("Delegating credentials");
 330         }
 331
 332         maj_status=gss_init_sec_context(&min_status,
 333                                         GSS_C_NO_CREDENTIAL, /* def. cred */
 334                                         &ctx->context,
 335                                         ctx->name,
 336                                         ctx->oid,
 337                                         GSS_C_MUTUAL_FLAG |
 338                                         GSS_C_INTEG_FLAG |
 339                                         deleg_flag,
 340                                         0, /* default lifetime */
 341                                         NULL, /* no channel bindings */
 342                                         recv_tok,
 343                                         NULL,
 344                                         send_tok,
 345                                         flags,
 346                                         NULL);
 347         ctx->status=maj_status;
 348         if (GSS_ERROR(maj_status)) {
 349                 ssh_gssapi_error(maj_status,min_status);
 350         }
 351         return(maj_status);
 352 }
 353
 354 /* Wrapper arround accept_sec_context
 355  * Requires that the context contains:
 356  *    oid
 357  *    credentials       (from ssh_gssapi_acquire_cred)
 358  */
 359 OM_uint32 ssh_gssapi_accept_ctx(Gssctxt *ctx,gss_buffer_desc *recv_tok,
 360                                 gss_buffer_desc *send_tok, OM_uint32 *flags)
 361 {
 362         OM_uint32 maj_status, min_status;
 363         gss_OID mech;
 364
 365         maj_status=gss_accept_sec_context(&min_status,
 366                                           &ctx->context,
 367                                           ctx->creds,
 368                                           recv_tok,
 369                                           GSS_C_NO_CHANNEL_BINDINGS,
 370                                           &ctx->client,
 371                                           &mech,
 372                                           send_tok,
 373                                           flags,
 374                                           NULL,
 375                                           &ctx->client_creds);
 376         if (GSS_ERROR(maj_status)) {
 377                 ssh_gssapi_error(maj_status,min_status);
 378         }
 379
 380         if (ctx->client_creds) {
 381                 debug("Received some client credentials");
 382         } else {
 383                 debug("Got no client credentials");
 384         }
 385
 386         /* FIXME: We should check that the mechanism thats being used is
 387          * the one that we asked for (in ctx->oid) */
 388
 389         ctx->status=maj_status;
 390
 391         return(maj_status);
 392 }
 393
 394 /* Create a service name for the given host */
 395 OM_uint32
 396 ssh_gssapi_import_name(Gssctxt *ctx, const char *host) {
 397         gss_buffer_desc gssbuf;
 398         OM_uint32 maj_status, min_status;
 399         struct hostent *hostinfo = NULL;
 400         char *xhost;
 401
 402         /* Make a copy of the host name, in case it was returned by a
 403          * previous call to gethostbyname(). */
 404         xhost = xstrdup(host);
 405
 406         /* Make sure we have the FQDN. Some GSSAPI implementations don't do
 407          * this for us themselves */
 408
 409         hostinfo = gethostbyname(xhost);
 410
 411         if ((hostinfo == NULL) || (hostinfo->h_name == NULL)) {
 412                 debug("Unable to get FQDN for \"%s\"", xhost);
 413         } else {
 414                 xfree(xhost);
 415                 xhost = xstrdup(hostinfo->h_name);
 416         }
 417
 418         gssbuf.length = sizeof("host@")+strlen(xhost);
 419
 420         gssbuf.value = xmalloc(gssbuf.length);
 421         if (gssbuf.value == NULL) {
 422                 xfree(xhost);
 423                 return(-1);
 424         }
 425         snprintf(gssbuf.value,gssbuf.length,"host@%s",xhost);
 426         if ((maj_status=gss_import_name(&min_status,
 427                                         &gssbuf,
 428                                         GSS_C_NT_HOSTBASED_SERVICE,
 429                                         &ctx->name))) {
 430                 ssh_gssapi_error(maj_status,min_status);
 431         }
 432
 433         xfree(xhost);
 434         xfree(gssbuf.value);
 435         return(maj_status);
 436 }
 437
 438 /* Acquire credentials for a server running on the current host.
 439  * Requires that the context structure contains a valid OID
 440  */
 441 OM_uint32
 442 ssh_gssapi_acquire_cred(Gssctxt *ctx) {
 443         OM_uint32 maj_status, min_status;
 444         char lname[MAXHOSTNAMELEN];
 445         gss_OID_set oidset;
 446
 447         gss_create_empty_oid_set(&min_status,&oidset);
 448         gss_add_oid_set_member(&min_status,ctx->oid,&oidset);
 449
 450         if (gethostname(lname, MAXHOSTNAMELEN)) {
 451                 return(-1);
 452         }
 453
 454         if ((maj_status=ssh_gssapi_import_name(ctx,lname))) {
 455                 return(maj_status);
 456         }
 457         if ((maj_status=gss_acquire_cred(&min_status,
 458                                     ctx->name,
 459                                     0,
 460                                     oidset,
 461                                     GSS_C_ACCEPT,
 462                                     &ctx->creds,
 463                                     NULL,
 464                                     NULL))) {
 465                 ssh_gssapi_error(maj_status,min_status);
 466         }
 467
 468         gss_release_oid_set(&min_status, &oidset);
 469         return(maj_status);
 470 }
 471
 472 /* Extract the client details from a given context. This can only reliably
 473  * be called once for a context */
 474
 475 OM_uint32
 476 ssh_gssapi_getclient(Gssctxt *ctx, enum ssh_gss_id *type,
 477                      gss_buffer_desc *name, gss_cred_id_t *creds) {
 478
 479         OM_uint32 maj_status,min_status;
 480
 481         *type=ssh_gssapi_get_ctype(ctx);
 482         if ((maj_status=gss_display_name(&min_status,ctx->client,name,NULL))) {
 483                 ssh_gssapi_error(maj_status,min_status);
 484         }
 485
 486         /* This is icky. There appears to be no way to copy this structure,
 487          * rather than the pointer to it, so we simply copy the pointer and
 488          * mark the originator as empty so we don't destroy it.
 489          */
 490         *creds=ctx->client_creds;
 491         ctx->client_creds=GSS_C_NO_CREDENTIAL;
 492         return(maj_status);
 493 }
 494
 495 #endif /* GSSAPI */