crypto/openssh-5/gss-serv.c

   1 /* $OpenBSD: gss-serv.c,v 1.21 2007/06/12 08:20:00 djm Exp $ */
   2
   3 /*
   4  * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28
  29 #ifdef GSSAPI
  30
  31 #include <sys/types.h>
  32 #include <sys/param.h>
  33
  34 #include <stdarg.h>
  35 #include <string.h>
  36 #include <unistd.h>
  37
  38 #include "xmalloc.h"
  39 #include "buffer.h"
  40 #include "key.h"
  41 #include "hostfile.h"
  42 #include "auth.h"
  43 #include "log.h"
  44 #include "channels.h"
  45 #include "session.h"
  46 #include "misc.h"
  47
  48 #include "ssh-gss.h"
  49
  50 static ssh_gssapi_client gssapi_client =
  51     { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
  52     GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
  53
  54 ssh_gssapi_mech gssapi_null_mech =
  55     { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
  56
  57 #ifdef KRB5
  58 extern ssh_gssapi_mech gssapi_kerberos_mech;
  59 #endif
  60
  61 ssh_gssapi_mech* supported_mechs[]= {
  62 #ifdef KRB5
  63         &gssapi_kerberos_mech,
  64 #endif
  65         &gssapi_null_mech,
  66 };
  67
  68
  69 /*
  70  * Acquire credentials for a server running on the current host.
  71  * Requires that the context structure contains a valid OID
  72  */
  73
  74 /* Returns a GSSAPI error code */
  75 /* Privileged (called from ssh_gssapi_server_ctx) */
  76 static OM_uint32
  77 ssh_gssapi_acquire_cred(Gssctxt *ctx)
  78 {
  79         OM_uint32 status;
  80         char lname[MAXHOSTNAMELEN];
  81         gss_OID_set oidset;
  82
  83         gss_create_empty_oid_set(&status, &oidset);
  84         gss_add_oid_set_member(&status, ctx->oid, &oidset);
  85
  86         if (gethostname(lname, MAXHOSTNAMELEN)) {
  87                 gss_release_oid_set(&status, &oidset);
  88                 return (-1);
  89         }
  90
  91         if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
  92                 gss_release_oid_set(&status, &oidset);
  93                 return (ctx->major);
  94         }
  95
  96         if ((ctx->major = gss_acquire_cred(&ctx->minor,
  97             ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL)))
  98                 ssh_gssapi_error(ctx);
  99
 100         gss_release_oid_set(&status, &oidset);
 101         return (ctx->major);
 102 }
 103
 104 /* Privileged */
 105 OM_uint32
 106 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
 107 {
 108         if (*ctx)
 109                 ssh_gssapi_delete_ctx(ctx);
 110         ssh_gssapi_build_ctx(ctx);
 111         ssh_gssapi_set_oid(*ctx, oid);
 112         return (ssh_gssapi_acquire_cred(*ctx));
 113 }
 114
 115 /* Unprivileged */
 116 void
 117 ssh_gssapi_supported_oids(gss_OID_set *oidset)
 118 {
 119         int i = 0;
 120         OM_uint32 min_status;
 121         int present;
 122         gss_OID_set supported;
 123
 124         gss_create_empty_oid_set(&min_status, oidset);
 125         gss_indicate_mechs(&min_status, &supported);
 126
 127         while (supported_mechs[i]->name != NULL) {
 128                 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
 129                     &supported_mechs[i]->oid, supported, &present)))
 130                         present = 0;
 131                 if (present)
 132                         gss_add_oid_set_member(&min_status,
 133                             &supported_mechs[i]->oid, oidset);
 134                 i++;
 135         }
 136
 137         gss_release_oid_set(&min_status, &supported);
 138 }
 139
 140
 141 /* Wrapper around accept_sec_context
 142  * Requires that the context contains:
 143  *    oid
 144  *    credentials       (from ssh_gssapi_acquire_cred)
 145  */
 146 /* Privileged */
 147 OM_uint32
 148 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
 149     gss_buffer_desc *send_tok, OM_uint32 *flags)
 150 {
 151         OM_uint32 status;
 152         gss_OID mech;
 153
 154         ctx->major = gss_accept_sec_context(&ctx->minor,
 155             &ctx->context, ctx->creds, recv_tok,
 156             GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
 157             send_tok, flags, NULL, &ctx->client_creds);
 158
 159         if (GSS_ERROR(ctx->major))
 160                 ssh_gssapi_error(ctx);
 161
 162         if (ctx->client_creds)
 163                 debug("Received some client credentials");
 164         else
 165                 debug("Got no client credentials");
 166
 167         status = ctx->major;
 168
 169         /* Now, if we're complete and we have the right flags, then
 170          * we flag the user as also having been authenticated
 171          */
 172
 173         if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 174             (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
 175                 if (ssh_gssapi_getclient(ctx, &gssapi_client))
 176                         fatal("Couldn't convert client name");
 177         }
 178
 179         return (status);
 180 }
 181
 182 /*
 183  * This parses an exported name, extracting the mechanism specific portion
 184  * to use for ACL checking. It verifies that the name belongs the mechanism
 185  * originally selected.
 186  */
 187 static OM_uint32
 188 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
 189 {
 190         u_char *tok;
 191         OM_uint32 offset;
 192         OM_uint32 oidl;
 193
 194         tok = ename->value;
 195
 196         /*
 197          * Check that ename is long enough for all of the fixed length
 198          * header, and that the initial ID bytes are correct
 199          */
 200
 201         if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
 202                 return GSS_S_FAILURE;
 203
 204         /*
 205          * Extract the OID, and check it. Here GSSAPI breaks with tradition
 206          * and does use the OID type and length bytes. To confuse things
 207          * there are two lengths - the first including these, and the
 208          * second without.
 209          */
 210
 211         oidl = get_u16(tok+2); /* length including next two bytes */
 212         oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
 213
 214         /*
 215          * Check the BER encoding for correct type and length, that the
 216          * string is long enough and that the OID matches that in our context
 217          */
 218         if (tok[4] != 0x06 || tok[5] != oidl ||
 219             ename->length < oidl+6 ||
 220             !ssh_gssapi_check_oid(ctx, tok+6, oidl))
 221                 return GSS_S_FAILURE;
 222
 223         offset = oidl+6;
 224
 225         if (ename->length < offset+4)
 226                 return GSS_S_FAILURE;
 227
 228         name->length = get_u32(tok+offset);
 229         offset += 4;
 230
 231         if (ename->length < offset+name->length)
 232                 return GSS_S_FAILURE;
 233
 234         name->value = xmalloc(name->length+1);
 235         memcpy(name->value, tok+offset, name->length);
 236         ((char *)name->value)[name->length] = 0;
 237
 238         return GSS_S_COMPLETE;
 239 }
 240
 241 /* Extract the client details from a given context. This can only reliably
 242  * be called once for a context */
 243
 244 /* Privileged (called from accept_secure_ctx) */
 245 OM_uint32
 246 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 247 {
 248         int i = 0;
 249
 250         gss_buffer_desc ename;
 251
 252         client->mech = NULL;
 253
 254         while (supported_mechs[i]->name != NULL) {
 255                 if (supported_mechs[i]->oid.length == ctx->oid->length &&
 256                     (memcmp(supported_mechs[i]->oid.elements,
 257                     ctx->oid->elements, ctx->oid->length) == 0))
 258                         client->mech = supported_mechs[i];
 259                 i++;
 260         }
 261
 262         if (client->mech == NULL)
 263                 return GSS_S_FAILURE;
 264
 265         if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
 266             &client->displayname, NULL))) {
 267                 ssh_gssapi_error(ctx);
 268                 return (ctx->major);
 269         }
 270
 271         if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
 272             &ename))) {
 273                 ssh_gssapi_error(ctx);
 274                 return (ctx->major);
 275         }
 276
 277         if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
 278             &client->exportedname))) {
 279                 return (ctx->major);
 280         }
 281
 282         /* We can't copy this structure, so we just move the pointer to it */
 283         client->creds = ctx->client_creds;
 284         ctx->client_creds = GSS_C_NO_CREDENTIAL;
 285         return (ctx->major);
 286 }
 287
 288 /* As user - called on fatal/exit */
 289 void
 290 ssh_gssapi_cleanup_creds(void)
 291 {
 292         if (gssapi_client.store.filename != NULL) {
 293                 /* Unlink probably isn't sufficient */
 294                 debug("removing gssapi cred file\"%s\"",
 295                     gssapi_client.store.filename);
 296                 unlink(gssapi_client.store.filename);
 297         }
 298 }
 299
 300 /* As user */
 301 void
 302 ssh_gssapi_storecreds(void)
 303 {
 304         if (gssapi_client.mech && gssapi_client.mech->storecreds) {
 305                 (*gssapi_client.mech->storecreds)(&gssapi_client);
 306         } else
 307                 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
 308 }
 309
 310 /* This allows GSSAPI methods to do things to the childs environment based
 311  * on the passed authentication process and credentials.
 312  */
 313 /* As user */
 314 void
 315 ssh_gssapi_do_child(char ***envp, u_int *envsizep)
 316 {
 317
 318         if (gssapi_client.store.envvar != NULL &&
 319             gssapi_client.store.envval != NULL) {
 320                 debug("Setting %s to %s", gssapi_client.store.envvar,
 321                     gssapi_client.store.envval);
 322                 child_set_env(envp, envsizep, gssapi_client.store.envvar,
 323                     gssapi_client.store.envval);
 324         }
 325 }
 326
 327 /* Privileged */
 328 int
 329 ssh_gssapi_userok(char *user)
 330 {
 331         OM_uint32 lmin;
 332
 333         if (gssapi_client.exportedname.length == 0 ||
 334             gssapi_client.exportedname.value == NULL) {
 335                 debug("No suitable client data");
 336                 return 0;
 337         }
 338         if (gssapi_client.mech && gssapi_client.mech->userok)
 339                 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
 340                         return 1;
 341                 else {
 342                         /* Destroy delegated credentials if userok fails */
 343                         gss_release_buffer(&lmin, &gssapi_client.displayname);
 344                         gss_release_buffer(&lmin, &gssapi_client.exportedname);
 345                         gss_release_cred(&lmin, &gssapi_client.creds);
 346                         memset(&gssapi_client, 0, sizeof(ssh_gssapi_client));
 347                         return 0;
 348                 }
 349         else
 350                 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
 351         return (0);
 352 }
 353
 354 /* Privileged */
 355 OM_uint32
 356 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
 357 {
 358         ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
 359             gssbuf, gssmic, NULL);
 360
 361         return (ctx->major);
 362 }
 363
 364 #endif