gss-serv.c

   1 /* $OpenBSD: gss-serv.c,v 1.18 2006/07/02 18:36:47 stevesk 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 "xmalloc.h"
  37 #include "misc.h"
  38
  39 #include "ssh-gss.h"
  40
  41 static ssh_gssapi_client gssapi_client =
  42     { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
  43     GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL}};
  44
  45 ssh_gssapi_mech gssapi_null_mech =
  46     { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
  47
  48 #ifdef KRB5
  49 extern ssh_gssapi_mech gssapi_kerberos_mech;
  50 #endif
  51
  52 ssh_gssapi_mech* supported_mechs[]= {
  53 #ifdef KRB5
  54         &gssapi_kerberos_mech,
  55 #endif
  56         &gssapi_null_mech,
  57 };
  58
  59 /* Unprivileged */
  60 void
  61 ssh_gssapi_supported_oids(gss_OID_set *oidset)
  62 {
  63         int i = 0;
  64         OM_uint32 min_status;
  65         int present;
  66         gss_OID_set supported;
  67
  68         gss_create_empty_oid_set(&min_status, oidset);
  69         gss_indicate_mechs(&min_status, &supported);
  70
  71         while (supported_mechs[i]->name != NULL) {
  72                 if (GSS_ERROR(gss_test_oid_set_member(&min_status,
  73                     &supported_mechs[i]->oid, supported, &present)))
  74                         present = 0;
  75                 if (present)
  76                         gss_add_oid_set_member(&min_status,
  77                             &supported_mechs[i]->oid, oidset);
  78                 i++;
  79         }
  80
  81         gss_release_oid_set(&min_status, &supported);
  82 }
  83
  84
  85 /* Wrapper around accept_sec_context
  86  * Requires that the context contains:
  87  *    oid
  88  *    credentials       (from ssh_gssapi_acquire_cred)
  89  */
  90 /* Privileged */
  91 OM_uint32
  92 ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
  93     gss_buffer_desc *send_tok, OM_uint32 *flags)
  94 {
  95         OM_uint32 status;
  96         gss_OID mech;
  97
  98         ctx->major = gss_accept_sec_context(&ctx->minor,
  99             &ctx->context, ctx->creds, recv_tok,
 100             GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
 101             send_tok, flags, NULL, &ctx->client_creds);
 102
 103         if (GSS_ERROR(ctx->major))
 104                 ssh_gssapi_error(ctx);
 105
 106         if (ctx->client_creds)
 107                 debug("Received some client credentials");
 108         else
 109                 debug("Got no client credentials");
 110
 111         status = ctx->major;
 112
 113         /* Now, if we're complete and we have the right flags, then
 114          * we flag the user as also having been authenticated
 115          */
 116
 117         if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
 118             (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
 119                 if (ssh_gssapi_getclient(ctx, &gssapi_client))
 120                         fatal("Couldn't convert client name");
 121         }
 122
 123         return (status);
 124 }
 125
 126 /*
 127  * This parses an exported name, extracting the mechanism specific portion
 128  * to use for ACL checking. It verifies that the name belongs the mechanism
 129  * originally selected.
 130  */
 131 static OM_uint32
 132 ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
 133 {
 134         u_char *tok;
 135         OM_uint32 offset;
 136         OM_uint32 oidl;
 137
 138         tok = ename->value;
 139
 140         /*
 141          * Check that ename is long enough for all of the fixed length
 142          * header, and that the initial ID bytes are correct
 143          */
 144
 145         if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
 146                 return GSS_S_FAILURE;
 147
 148         /*
 149          * Extract the OID, and check it. Here GSSAPI breaks with tradition
 150          * and does use the OID type and length bytes. To confuse things
 151          * there are two lengths - the first including these, and the
 152          * second without.
 153          */
 154
 155         oidl = get_u16(tok+2); /* length including next two bytes */
 156         oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
 157
 158         /*
 159          * Check the BER encoding for correct type and length, that the
 160          * string is long enough and that the OID matches that in our context
 161          */
 162         if (tok[4] != 0x06 || tok[5] != oidl ||
 163             ename->length < oidl+6 ||
 164             !ssh_gssapi_check_oid(ctx, tok+6, oidl))
 165                 return GSS_S_FAILURE;
 166
 167         offset = oidl+6;
 168
 169         if (ename->length < offset+4)
 170                 return GSS_S_FAILURE;
 171
 172         name->length = get_u32(tok+offset);
 173         offset += 4;
 174
 175         if (ename->length < offset+name->length)
 176                 return GSS_S_FAILURE;
 177
 178         name->value = xmalloc(name->length+1);
 179         memcpy(name->value, tok+offset, name->length);
 180         ((char *)name->value)[name->length] = 0;
 181
 182         return GSS_S_COMPLETE;
 183 }
 184
 185 /* Extract the client details from a given context. This can only reliably
 186  * be called once for a context */
 187
 188 /* Privileged (called from accept_secure_ctx) */
 189 OM_uint32
 190 ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
 191 {
 192         int i = 0;
 193
 194         gss_buffer_desc ename;
 195
 196         client->mech = NULL;
 197
 198         while (supported_mechs[i]->name != NULL) {
 199                 if (supported_mechs[i]->oid.length == ctx->oid->length &&
 200                     (memcmp(supported_mechs[i]->oid.elements,
 201                     ctx->oid->elements, ctx->oid->length) == 0))
 202                         client->mech = supported_mechs[i];
 203                 i++;
 204         }
 205
 206         if (client->mech == NULL)
 207                 return GSS_S_FAILURE;
 208
 209         if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
 210             &client->displayname, NULL))) {
 211                 ssh_gssapi_error(ctx);
 212                 return (ctx->major);
 213         }
 214
 215         if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
 216             &ename))) {
 217                 ssh_gssapi_error(ctx);
 218                 return (ctx->major);
 219         }
 220
 221         if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
 222             &client->exportedname))) {
 223                 return (ctx->major);
 224         }
 225
 226         /* We can't copy this structure, so we just move the pointer to it */
 227         client->creds = ctx->client_creds;
 228         ctx->client_creds = GSS_C_NO_CREDENTIAL;
 229         return (ctx->major);
 230 }
 231
 232 /* As user - called on fatal/exit */
 233 void
 234 ssh_gssapi_cleanup_creds(void)
 235 {
 236         if (gssapi_client.store.filename != NULL) {
 237                 /* Unlink probably isn't sufficient */
 238                 debug("removing gssapi cred file\"%s\"",
 239                     gssapi_client.store.filename);
 240                 unlink(gssapi_client.store.filename);
 241         }
 242 }
 243
 244 /* As user */
 245 void
 246 ssh_gssapi_storecreds(void)
 247 {
 248         if (gssapi_client.mech && gssapi_client.mech->storecreds) {
 249                 (*gssapi_client.mech->storecreds)(&gssapi_client);
 250         } else
 251                 debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
 252 }
 253
 254 /* This allows GSSAPI methods to do things to the childs environment based
 255  * on the passed authentication process and credentials.
 256  */
 257 /* As user */
 258 void
 259 ssh_gssapi_do_child(char ***envp, u_int *envsizep)
 260 {
 261
 262         if (gssapi_client.store.envvar != NULL &&
 263             gssapi_client.store.envval != NULL) {
 264                 debug("Setting %s to %s", gssapi_client.store.envvar,
 265                     gssapi_client.store.envval);
 266                 child_set_env(envp, envsizep, gssapi_client.store.envvar,
 267                     gssapi_client.store.envval);
 268         }
 269 }
 270
 271 /* Privileged */
 272 int
 273 ssh_gssapi_userok(char *user)
 274 {
 275         OM_uint32 lmin;
 276
 277         if (gssapi_client.exportedname.length == 0 ||
 278             gssapi_client.exportedname.value == NULL) {
 279                 debug("No suitable client data");
 280                 return 0;
 281         }
 282         if (gssapi_client.mech && gssapi_client.mech->userok)
 283                 if ((*gssapi_client.mech->userok)(&gssapi_client, user))
 284                         return 1;
 285                 else {
 286                         /* Destroy delegated credentials if userok fails */
 287                         gss_release_buffer(&lmin, &gssapi_client.displayname);
 288                         gss_release_buffer(&lmin, &gssapi_client.exportedname);
 289                         gss_release_cred(&lmin, &gssapi_client.creds);
 290                         memset(&gssapi_client, 0, sizeof(ssh_gssapi_client));
 291                         return 0;
 292                 }
 293         else
 294                 debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
 295         return (0);
 296 }
 297
 298 /* Privileged */
 299 OM_uint32
 300 ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
 301 {
 302         ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
 303             gssbuf, gssmic, NULL);
 304
 305         return (ctx->major);
 306 }
 307
 308 #endif