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