gss-serv.c

   1 /* $OpenBSD: gss-serv.c,v 1.22 2008/05/08 12:02:23 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 "openbsd-compat/sys-queue.h"
  39 #include "xmalloc.h"
  40 #include "buffer.h"
  41 #include "key.h"
  42 #include "hostfile.h"
  43 #include "auth.h"
  44 #include "log.h"
  45 #include "channels.h"
  46 #include "session.h"
  47 #include "misc.h"
  48
  49 #include "ssh-gss.h"
  50
  51 static ssh_gssapi_client gssapi_client =
  52     { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
  53     GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
  54
  55 ssh_gssapi_mech gssapi_null_mech =
  56     { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
  57
  58 #ifdef KRB5
  59 extern ssh_gssapi_mech gssapi_kerberos_mech;
  60 #endif
  61
  62 ssh_gssapi_mech* supported_mechs[]= {
  63 #ifdef KRB5
  64         &gssapi_kerberos_mech,
  65 #endif
  66         &gssapi_null_mech,
  67 };
  68
  69
  70 /*
  71  * Acquire credentials for a server running on the current host.
  72  * Requires that the context structure contains a valid OID
  73  */
  74
  75 /* Returns a GSSAPI error code */
  76 /* Privileged (called from ssh_gssapi_server_ctx) */
  77 static OM_uint32
  78 ssh_gssapi_acquire_cred(Gssctxt *ctx)
  79 {
  80         OM_uint32 status;
  81         char lname[MAXHOSTNAMELEN];
  82         gss_OID_set oidset;
  83
  84         gss_create_empty_oid_set(&status, &oidset);
  85         gss_add_oid_set_member(&status, ctx->oid, &oidset);
  86
  87         if (gethostname(lname, MAXHOSTNAMELEN)) {
  88                 gss_release_oid_set(&status, &oidset);
  89                 return (-1);
  90         }
  91
  92         if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
  93                 gss_release_oid_set(&status, &oidset);
  94                 return (ctx->major);
  95         }
  96
  97         if ((ctx->major = gss_acquire_cred(&ctx->minor,
  98             ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL)))
  99                 ssh_gssapi_error(ctx);
 100
 101         gss_release_oid_set(&status, &oidset);
 102         return (ctx->major);
 103 }
 104
 105 /* Privileged */
 106 OM_uint32
 107 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
 108 {
 109         if (*ctx)
 110                 ssh_gssapi_delete_ctx(ctx);
 111         ssh_gssapi_build_ctx(ctx);
 112         ssh_gssapi_set_oid(*ctx, oid);
 113         return (ssh_gssapi_acquire_cred(*ctx));
 114 }
 115
 116 /* Unprivileged */
 117 void
 118 ssh_gssapi_supported_oids(gss_OID_set *oidset)
 119 {
 120         int i = 0;
 121         OM_uint32 min_status;
 122         int present;
 123         gss_OID_set supported;
 124
 125         gss_create_empty_oid_set(&min_status, oidset);
 126         gss_indicate_mechs(&min_status, &supported);
 127
 128         while (supported_mechs[i]->name != NULL) {
 129                 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
 130                     &supported_mechs[i]->oid, supported, &present)))
 131                         present = 0;
 132                 if (present)
 133                         gss_add_oid_set_member(&min_status,
 134                             &supported_mechs[i]->oid, oidset);
 135                 i++;
 136         }
 137
 138         gss_release_oid_set(&min_status, &supported);
 139 }
 140
 141
 142 /* Wrapper around accept_sec_context
 143  * Requires that the context contains:
 144  *    oid
 145  *    credentials       (from ssh_gssapi_acquire_cred)
 146  */
 147 /* Privileged */
 148 OM_uint32
 149 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
 150     gss_buffer_desc *send_tok, OM_uint32 *flags)
 151 {
 152         OM_uint32 status;
 153         gss_OID mech;
 154
 155         ctx->major = gss_accept_sec_context(&ctx->minor,
 156             &ctx->context, ctx->creds, recv_tok,
 157             GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
 158             send_tok, flags, NULL, &ctx->client_creds);
 159
 160         if (GSS_ERROR(ctx->major))
 161                 ssh_gssapi_error(ctx);
 162
 163         if (ctx->client_creds)
 164                 debug("Received some client credentials");
 165         else
 166                 debug("Got no client credentials");
 167
 168         status = ctx->major;
 169
 170         /* Now, if we're complete and we have the right flags, then
 171          * we flag the user as also having been authenticated
 172          */
 173
 174         if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 175             (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
 176                 if (ssh_gssapi_getclient(ctx, &gssapi_client))
 177                         fatal("Couldn't convert client name");
 178         }
 179
 180         return (status);
 181 }
 182
 183 /*
 184  * This parses an exported name, extracting the mechanism specific portion
 185  * to use for ACL checking. It verifies that the name belongs the mechanism
 186  * originally selected.
 187  */
 188 static OM_uint32
 189 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
 190 {
 191         u_char *tok;
 192         OM_uint32 offset;
 193         OM_uint32 oidl;
 194
 195         tok = ename->value;
 196
 197         /*
 198          * Check that ename is long enough for all of the fixed length
 199          * header, and that the initial ID bytes are correct
 200          */
 201
 202         if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
 203                 return GSS_S_FAILURE;
 204
 205         /*
 206          * Extract the OID, and check it. Here GSSAPI breaks with tradition
 207          * and does use the OID type and length bytes. To confuse things
 208          * there are two lengths - the first including these, and the
 209          * second without.
 210          */
 211
 212         oidl = get_u16(tok+2); /* length including next two bytes */
 213         oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
 214
 215         /*
 216          * Check the BER encoding for correct type and length, that the
 217          * string is long enough and that the OID matches that in our context
 218          */
 219         if (tok[4] != 0x06 || tok[5] != oidl ||
 220             ename->length < oidl+6 ||
 221             !ssh_gssapi_check_oid(ctx, tok+6, oidl))
 222                 return GSS_S_FAILURE;
 223
 224         offset = oidl+6;
 225
 226         if (ename->length < offset+4)
 227                 return GSS_S_FAILURE;
 228
 229         name->length = get_u32(tok+offset);
 230         offset += 4;
 231
 232         if (ename->length < offset+name->length)
 233                 return GSS_S_FAILURE;
 234
 235         name->value = xmalloc(name->length+1);
 236         memcpy(name->value, tok+offset, name->length);
 237         ((char *)name->value)[name->length] = 0;
 238
 239         return GSS_S_COMPLETE;
 240 }
 241
 242 /* Extract the client details from a given context. This can only reliably
 243  * be called once for a context */
 244
 245 /* Privileged (called from accept_secure_ctx) */
 246 OM_uint32
 247 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 248 {
 249         int i = 0;
 250
 251         gss_buffer_desc ename;
 252
 253         client->mech = NULL;
 254
 255         while (supported_mechs[i]->name != NULL) {
 256                 if (supported_mechs[i]->oid.length == ctx->oid->length &&
 257                     (memcmp(supported_mechs[i]->oid.elements,
 258                     ctx->oid->elements, ctx->oid->length) == 0))
 259                         client->mech = supported_mechs[i];
 260                 i++;
 261         }
 262
 263         if (client->mech == NULL)
 264                 return GSS_S_FAILURE;
 265
 266         if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
 267             &client->displayname, NULL))) {
 268                 ssh_gssapi_error(ctx);
 269                 return (ctx->major);
 270         }
 271
 272         if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
 273             &ename))) {
 274                 ssh_gssapi_error(ctx);
 275                 return (ctx->major);
 276         }
 277
 278         if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
 279             &client->exportedname))) {
 280                 return (ctx->major);
 281         }
 282
 283         /* We can't copy this structure, so we just move the pointer to it */
 284         client->creds = ctx->client_creds;
 285         ctx->client_creds = GSS_C_NO_CREDENTIAL;
 286         return (ctx->major);
 287 }
 288
 289 /* As user - called on fatal/exit */
 290 void
 291 ssh_gssapi_cleanup_creds(void)
 292 {
 293         if (gssapi_client.store.filename != NULL) {
 294                 /* Unlink probably isn't sufficient */
 295                 debug("removing gssapi cred file\"%s\"",
 296                     gssapi_client.store.filename);
 297                 unlink(gssapi_client.store.filename);
 298         }
 299 }
 300
 301 /* As user */
 302 void
 303 ssh_gssapi_storecreds(void)
 304 {
 305         if (gssapi_client.mech && gssapi_client.mech->storecreds) {
 306                 (*gssapi_client.mech->storecreds)(&gssapi_client);
 307         } else
 308                 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
 309 }
 310
 311 /* This allows GSSAPI methods to do things to the childs environment based
 312  * on the passed authentication process and credentials.
 313  */
 314 /* As user */
 315 void
 316 ssh_gssapi_do_child(char ***envp, u_int *envsizep)
 317 {
 318
 319         if (gssapi_client.store.envvar != NULL &&
 320             gssapi_client.store.envval != NULL) {
 321                 debug("Setting %s to %s", gssapi_client.store.envvar,
 322                     gssapi_client.store.envval);
 323                 child_set_env(envp, envsizep, gssapi_client.store.envvar,
 324                     gssapi_client.store.envval);
 325         }
 326 }
 327
 328 /* Privileged */
 329 int
 330 ssh_gssapi_userok(char *user)
 331 {
 332         OM_uint32 lmin;
 333
 334         if (gssapi_client.exportedname.length == 0 ||
 335             gssapi_client.exportedname.value == NULL) {
 336                 debug("No suitable client data");
 337                 return 0;
 338         }
 339         if (gssapi_client.mech && gssapi_client.mech->userok)
 340                 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
 341                         return 1;
 342                 else {
 343                         /* Destroy delegated credentials if userok fails */
 344                         gss_release_buffer(&lmin, &gssapi_client.displayname);
 345                         gss_release_buffer(&lmin, &gssapi_client.exportedname);
 346                         gss_release_cred(&lmin, &gssapi_client.creds);
 347                         memset(&gssapi_client, 0, sizeof(ssh_gssapi_client));
 348                         return 0;
 349                 }
 350         else
 351                 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
 352         return (0);
 353 }
 354
 355 /* Privileged */
 356 OM_uint32
 357 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
 358 {
 359         ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
 360             gssbuf, gssmic, NULL);
 361
 362         return (ctx->major);
 363 }
 364
 365 #endif