gss-serv.c

   1 /* $OpenBSD: gss-serv.c,v 1.20 2006/08/03 03:34:42 deraadt 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
  33 #include <string.h>
  34 #include <unistd.h>
  35
  36 #include "xmalloc.h"
  37 #include "buffer.h"
  38 #include "key.h"
  39 #include "hostfile.h"
  40 #include "auth.h"
  41 #include "log.h"
  42 #include "channels.h"
  43 #include "session.h"
  44 #include "misc.h"
  45
  46 #include "ssh-gss.h"
  47
  48 static ssh_gssapi_client gssapi_client =
  49     { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
  50     GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
  51
  52 ssh_gssapi_mech gssapi_null_mech =
  53     { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
  54
  55 #ifdef KRB5
  56 extern ssh_gssapi_mech gssapi_kerberos_mech;
  57 #endif
  58
  59 ssh_gssapi_mech* supported_mechs[]= {
  60 #ifdef KRB5
  61         &gssapi_kerberos_mech,
  62 #endif
  63         &gssapi_null_mech,
  64 };
  65
  66 /* Unprivileged */
  67 void
  68 ssh_gssapi_supported_oids(gss_OID_set *oidset)
  69 {
  70         int i = 0;
  71         OM_uint32 min_status;
  72         int present;
  73         gss_OID_set supported;
  74
  75         gss_create_empty_oid_set(&min_status, oidset);
  76         gss_indicate_mechs(&min_status, &supported);
  77
  78         while (supported_mechs[i]->name != NULL) {
  79                 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
  80                     &supported_mechs[i]->oid, supported, &present)))
  81                         present = 0;
  82                 if (present)
  83                         gss_add_oid_set_member(&min_status,
  84                             &supported_mechs[i]->oid, oidset);
  85                 i++;
  86         }
  87
  88         gss_release_oid_set(&min_status, &supported);
  89 }
  90
  91
  92 /* Wrapper around accept_sec_context
  93  * Requires that the context contains:
  94  *    oid
  95  *    credentials       (from ssh_gssapi_acquire_cred)
  96  */
  97 /* Privileged */
  98 OM_uint32
  99 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
 100     gss_buffer_desc *send_tok, OM_uint32 *flags)
 101 {
 102         OM_uint32 status;
 103         gss_OID mech;
 104
 105         ctx->major = gss_accept_sec_context(&ctx->minor,
 106             &ctx->context, ctx->creds, recv_tok,
 107             GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
 108             send_tok, flags, NULL, &ctx->client_creds);
 109
 110         if (GSS_ERROR(ctx->major))
 111                 ssh_gssapi_error(ctx);
 112
 113         if (ctx->client_creds)
 114                 debug("Received some client credentials");
 115         else
 116                 debug("Got no client credentials");
 117
 118         status = ctx->major;
 119
 120         /* Now, if we're complete and we have the right flags, then
 121          * we flag the user as also having been authenticated
 122          */
 123
 124         if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 125             (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
 126                 if (ssh_gssapi_getclient(ctx, &gssapi_client))
 127                         fatal("Couldn't convert client name");
 128         }
 129
 130         return (status);
 131 }
 132
 133 /*
 134  * This parses an exported name, extracting the mechanism specific portion
 135  * to use for ACL checking. It verifies that the name belongs the mechanism
 136  * originally selected.
 137  */
 138 static OM_uint32
 139 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
 140 {
 141         u_char *tok;
 142         OM_uint32 offset;
 143         OM_uint32 oidl;
 144
 145         tok = ename->value;
 146
 147         /*
 148          * Check that ename is long enough for all of the fixed length
 149          * header, and that the initial ID bytes are correct
 150          */
 151
 152         if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
 153                 return GSS_S_FAILURE;
 154
 155         /*
 156          * Extract the OID, and check it. Here GSSAPI breaks with tradition
 157          * and does use the OID type and length bytes. To confuse things
 158          * there are two lengths - the first including these, and the
 159          * second without.
 160          */
 161
 162         oidl = get_u16(tok+2); /* length including next two bytes */
 163         oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
 164
 165         /*
 166          * Check the BER encoding for correct type and length, that the
 167          * string is long enough and that the OID matches that in our context
 168          */
 169         if (tok[4] != 0x06 || tok[5] != oidl ||
 170             ename->length < oidl+6 ||
 171             !ssh_gssapi_check_oid(ctx, tok+6, oidl))
 172                 return GSS_S_FAILURE;
 173
 174         offset = oidl+6;
 175
 176         if (ename->length < offset+4)
 177                 return GSS_S_FAILURE;
 178
 179         name->length = get_u32(tok+offset);
 180         offset += 4;
 181
 182         if (ename->length < offset+name->length)
 183                 return GSS_S_FAILURE;
 184
 185         name->value = xmalloc(name->length+1);
 186         memcpy(name->value, tok+offset, name->length);
 187         ((char *)name->value)[name->length] = 0;
 188
 189         return GSS_S_COMPLETE;
 190 }
 191
 192 /* Extract the client details from a given context. This can only reliably
 193  * be called once for a context */
 194
 195 /* Privileged (called from accept_secure_ctx) */
 196 OM_uint32
 197 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 198 {
 199         int i = 0;
 200
 201         gss_buffer_desc ename;
 202
 203         client->mech = NULL;
 204
 205         while (supported_mechs[i]->name != NULL) {
 206                 if (supported_mechs[i]->oid.length == ctx->oid->length &&
 207                     (memcmp(supported_mechs[i]->oid.elements,
 208                     ctx->oid->elements, ctx->oid->length) == 0))
 209                         client->mech = supported_mechs[i];
 210                 i++;
 211         }
 212
 213         if (client->mech == NULL)
 214                 return GSS_S_FAILURE;
 215
 216         if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
 217             &client->displayname, NULL))) {
 218                 ssh_gssapi_error(ctx);
 219                 return (ctx->major);
 220         }
 221
 222         if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
 223             &ename))) {
 224                 ssh_gssapi_error(ctx);
 225                 return (ctx->major);
 226         }
 227
 228         if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
 229             &client->exportedname))) {
 230                 return (ctx->major);
 231         }
 232
 233         /* We can't copy this structure, so we just move the pointer to it */
 234         client->creds = ctx->client_creds;
 235         ctx->client_creds = GSS_C_NO_CREDENTIAL;
 236         return (ctx->major);
 237 }
 238
 239 /* As user - called on fatal/exit */
 240 void
 241 ssh_gssapi_cleanup_creds(void)
 242 {
 243         if (gssapi_client.store.filename != NULL) {
 244                 /* Unlink probably isn't sufficient */
 245                 debug("removing gssapi cred file\"%s\"",
 246                     gssapi_client.store.filename);
 247                 unlink(gssapi_client.store.filename);
 248         }
 249 }
 250
 251 /* As user */
 252 void
 253 ssh_gssapi_storecreds(void)
 254 {
 255         if (gssapi_client.mech && gssapi_client.mech->storecreds) {
 256                 (*gssapi_client.mech->storecreds)(&gssapi_client);
 257         } else
 258                 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
 259 }
 260
 261 /* This allows GSSAPI methods to do things to the childs environment based
 262  * on the passed authentication process and credentials.
 263  */
 264 /* As user */
 265 void
 266 ssh_gssapi_do_child(char ***envp, u_int *envsizep)
 267 {
 268
 269         if (gssapi_client.store.envvar != NULL &&
 270             gssapi_client.store.envval != NULL) {
 271                 debug("Setting %s to %s", gssapi_client.store.envvar,
 272                     gssapi_client.store.envval);
 273                 child_set_env(envp, envsizep, gssapi_client.store.envvar,
 274                     gssapi_client.store.envval);
 275         }
 276 }
 277
 278 /* Privileged */
 279 int
 280 ssh_gssapi_userok(char *user)
 281 {
 282         OM_uint32 lmin;
 283
 284         if (gssapi_client.exportedname.length == 0 ||
 285             gssapi_client.exportedname.value == NULL) {
 286                 debug("No suitable client data");
 287                 return 0;
 288         }
 289         if (gssapi_client.mech && gssapi_client.mech->userok)
 290                 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
 291                         return 1;
 292                 else {
 293                         /* Destroy delegated credentials if userok fails */
 294                         gss_release_buffer(&lmin, &gssapi_client.displayname);
 295                         gss_release_buffer(&lmin, &gssapi_client.exportedname);
 296                         gss_release_cred(&lmin, &gssapi_client.creds);
 297                         memset(&gssapi_client, 0, sizeof(ssh_gssapi_client));
 298                         return 0;
 299                 }
 300         else
 301                 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
 302         return (0);
 303 }
 304
 305 /* Privileged */
 306 OM_uint32
 307 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
 308 {
 309         ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
 310             gssbuf, gssmic, NULL);
 311
 312         return (ctx->major);
 313 }
 314
 315 #endif