gss-serv.c

   1 /* $OpenBSD: gss-serv.c,v 1.17 2006/03/30 09:58:15 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 "bufaux.h"
  32 #include "auth.h"
  33 #include "log.h"
  34 #include "channels.h"
  35 #include "session.h"
  36 #include "servconf.h"
  37 #include "xmalloc.h"
  38 #include "misc.h"
  39
  40 #include "ssh-gss.h"
  41
  42 static ssh_gssapi_client gssapi_client =
  43     { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
  44     GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
  45
  46 ssh_gssapi_mech gssapi_null_mech =
  47     { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
  48
  49 #ifdef KRB5
  50 extern ssh_gssapi_mech gssapi_kerberos_mech;
  51 #endif
  52
  53 ssh_gssapi_mech* supported_mechs[]= {
  54 #ifdef KRB5
  55         &gssapi_kerberos_mech,
  56 #endif
  57         &gssapi_null_mech,
  58 };
  59
  60 /* Unprivileged */
  61 void
  62 ssh_gssapi_supported_oids(gss_OID_set *oidset)
  63 {
  64         int i = 0;
  65         OM_uint32 min_status;
  66         int present;
  67         gss_OID_set supported;
  68
  69         gss_create_empty_oid_set(&min_status, oidset);
  70         gss_indicate_mechs(&min_status, &supported);
  71
  72         while (supported_mechs[i]->name != NULL) {
  73                 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
  74                     &supported_mechs[i]->oid, supported, &present)))
  75                         present = 0;
  76                 if (present)
  77                         gss_add_oid_set_member(&min_status,
  78                             &supported_mechs[i]->oid, oidset);
  79                 i++;
  80         }
  81
  82         gss_release_oid_set(&min_status, &supported);
  83 }
  84
  85
  86 /* Wrapper around accept_sec_context
  87  * Requires that the context contains:
  88  *    oid
  89  *    credentials       (from ssh_gssapi_acquire_cred)
  90  */
  91 /* Privileged */
  92 OM_uint32
  93 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
  94     gss_buffer_desc *send_tok, OM_uint32 *flags)
  95 {
  96         OM_uint32 status;
  97         gss_OID mech;
  98
  99         ctx->major = gss_accept_sec_context(&ctx->minor,
 100             &ctx->context, ctx->creds, recv_tok,
 101             GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
 102             send_tok, flags, NULL, &ctx->client_creds);
 103
 104         if (GSS_ERROR(ctx->major))
 105                 ssh_gssapi_error(ctx);
 106
 107         if (ctx->client_creds)
 108                 debug("Received some client credentials");
 109         else
 110                 debug("Got no client credentials");
 111
 112         status = ctx->major;
 113
 114         /* Now, if we're complete and we have the right flags, then
 115          * we flag the user as also having been authenticated
 116          */
 117
 118         if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 119             (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
 120                 if (ssh_gssapi_getclient(ctx, &gssapi_client))
 121                         fatal("Couldn't convert client name");
 122         }
 123
 124         return (status);
 125 }
 126
 127 /*
 128  * This parses an exported name, extracting the mechanism specific portion
 129  * to use for ACL checking. It verifies that the name belongs the mechanism
 130  * originally selected.
 131  */
 132 static OM_uint32
 133 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
 134 {
 135         u_char *tok;
 136         OM_uint32 offset;
 137         OM_uint32 oidl;
 138
 139         tok = ename->value;
 140
 141         /*
 142          * Check that ename is long enough for all of the fixed length
 143          * header, and that the initial ID bytes are correct
 144          */
 145
 146         if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
 147                 return GSS_S_FAILURE;
 148
 149         /*
 150          * Extract the OID, and check it. Here GSSAPI breaks with tradition
 151          * and does use the OID type and length bytes. To confuse things
 152          * there are two lengths - the first including these, and the
 153          * second without.
 154          */
 155
 156         oidl = get_u16(tok+2); /* length including next two bytes */
 157         oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
 158
 159         /*
 160          * Check the BER encoding for correct type and length, that the
 161          * string is long enough and that the OID matches that in our context
 162          */
 163         if (tok[4] != 0x06 || tok[5] != oidl ||
 164             ename->length < oidl+6 ||
 165             !ssh_gssapi_check_oid(ctx, tok+6, oidl))
 166                 return GSS_S_FAILURE;
 167
 168         offset = oidl+6;
 169
 170         if (ename->length < offset+4)
 171                 return GSS_S_FAILURE;
 172
 173         name->length = get_u32(tok+offset);
 174         offset += 4;
 175
 176         if (ename->length < offset+name->length)
 177                 return GSS_S_FAILURE;
 178
 179         name->value = xmalloc(name->length+1);
 180         memcpy(name->value, tok+offset, name->length);
 181         ((char *)name->value)[name->length] = 0;
 182
 183         return GSS_S_COMPLETE;
 184 }
 185
 186 /* Extract the client details from a given context. This can only reliably
 187  * be called once for a context */
 188
 189 /* Privileged (called from accept_secure_ctx) */
 190 OM_uint32
 191 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 192 {
 193         int i = 0;
 194
 195         gss_buffer_desc ename;
 196
 197         client->mech = NULL;
 198
 199         while (supported_mechs[i]->name != NULL) {
 200                 if (supported_mechs[i]->oid.length == ctx->oid->length &&
 201                     (memcmp(supported_mechs[i]->oid.elements,
 202                     ctx->oid->elements, ctx->oid->length) == 0))
 203                         client->mech = supported_mechs[i];
 204                 i++;
 205         }
 206
 207         if (client->mech == NULL)
 208                 return GSS_S_FAILURE;
 209
 210         if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
 211             &client->displayname, NULL))) {
 212                 ssh_gssapi_error(ctx);
 213                 return (ctx->major);
 214         }
 215
 216         if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
 217             &ename))) {
 218                 ssh_gssapi_error(ctx);
 219                 return (ctx->major);
 220         }
 221
 222         if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
 223             &client->exportedname))) {
 224                 return (ctx->major);
 225         }
 226
 227         /* We can't copy this structure, so we just move the pointer to it */
 228         client->creds = ctx->client_creds;
 229         ctx->client_creds = GSS_C_NO_CREDENTIAL;
 230         return (ctx->major);
 231 }
 232
 233 /* As user - called on fatal/exit */
 234 void
 235 ssh_gssapi_cleanup_creds(void)
 236 {
 237         if (gssapi_client.store.filename != NULL) {
 238                 /* Unlink probably isn't sufficient */
 239                 debug("removing gssapi cred file\"%s\"",
 240                     gssapi_client.store.filename);
 241                 unlink(gssapi_client.store.filename);
 242         }
 243 }
 244
 245 /* As user */
 246 void
 247 ssh_gssapi_storecreds(void)
 248 {
 249         if (gssapi_client.mech && gssapi_client.mech->storecreds) {
 250                 (*gssapi_client.mech->storecreds)(&gssapi_client);
 251         } else
 252                 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
 253 }
 254
 255 /* This allows GSSAPI methods to do things to the childs environment based
 256  * on the passed authentication process and credentials.
 257  */
 258 /* As user */
 259 void
 260 ssh_gssapi_do_child(char ***envp, u_int *envsizep)
 261 {
 262
 263         if (gssapi_client.store.envvar != NULL &&
 264             gssapi_client.store.envval != NULL) {
 265                 debug("Setting %s to %s", gssapi_client.store.envvar,
 266                     gssapi_client.store.envval);
 267                 child_set_env(envp, envsizep, gssapi_client.store.envvar,
 268                     gssapi_client.store.envval);
 269         }
 270 }
 271
 272 /* Privileged */
 273 int
 274 ssh_gssapi_userok(char *user)
 275 {
 276         OM_uint32 lmin;
 277
 278         if (gssapi_client.exportedname.length == 0 ||
 279             gssapi_client.exportedname.value == NULL) {
 280                 debug("No suitable client data");
 281                 return 0;
 282         }
 283         if (gssapi_client.mech && gssapi_client.mech->userok)
 284                 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
 285                         return 1;
 286                 else {
 287                         /* Destroy delegated credentials if userok fails */
 288                         gss_release_buffer(&lmin, &gssapi_client.displayname);
 289                         gss_release_buffer(&lmin, &gssapi_client.exportedname);
 290                         gss_release_cred(&lmin, &gssapi_client.creds);
 291                         memset(&gssapi_client, 0, sizeof(ssh_gssapi_client));
 292                         return 0;
 293                 }
 294         else
 295                 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
 296         return (0);
 297 }
 298
 299 /* Privileged */
 300 OM_uint32
 301 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
 302 {
 303         ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
 304             gssbuf, gssmic, NULL);
 305
 306         return (ctx->major);
 307 }
 308
 309 #endif