gss-genr.c

   1 /* $OpenBSD: gss-genr.c,v 1.14 2006/08/18 13:54:54 djm Exp $ */
   2
   3 /*
   4  * Copyright (c) 2001-2006 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 "xmalloc.h"
  39 #include "buffer.h"
  40 #include "log.h"
  41 #include "ssh2.h"
  42
  43 #include "ssh-gss.h"
  44
  45 extern u_char *session_id2;
  46 extern u_int session_id2_len;
  47
  48 /* Check that the OID in a data stream matches that in the context */
  49 int
  50 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
  51 {
  52         return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
  53             ctx->oid->length == len &&
  54             memcmp(ctx->oid->elements, data, len) == 0);
  55 }
  56
  57 /* Set the contexts OID from a data stream */
  58 void
  59 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
  60 {
  61         if (ctx->oid != GSS_C_NO_OID) {
  62                 xfree(ctx->oid->elements);
  63                 xfree(ctx->oid);
  64         }
  65         ctx->oid = xmalloc(sizeof(gss_OID_desc));
  66         ctx->oid->length = len;
  67         ctx->oid->elements = xmalloc(len);
  68         memcpy(ctx->oid->elements, data, len);
  69 }
  70
  71 /* Set the contexts OID */
  72 void
  73 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
  74 {
  75         ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
  76 }
  77
  78 /* All this effort to report an error ... */
  79 void
  80 ssh_gssapi_error(Gssctxt *ctxt)
  81 {
  82         char *s;
  83
  84         s = ssh_gssapi_last_error(ctxt, NULL, NULL);
  85         debug("%s", s);
  86         xfree(s);
  87 }
  88
  89 char *
  90 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
  91     OM_uint32 *minor_status)
  92 {
  93         OM_uint32 lmin;
  94         gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
  95         OM_uint32 ctx;
  96         Buffer b;
  97         char *ret;
  98
  99         buffer_init(&b);
 100
 101         if (major_status != NULL)
 102                 *major_status = ctxt->major;
 103         if (minor_status != NULL)
 104                 *minor_status = ctxt->minor;
 105
 106         ctx = 0;
 107         /* The GSSAPI error */
 108         do {
 109                 gss_display_status(&lmin, ctxt->major,
 110                     GSS_C_GSS_CODE, GSS_C_NULL_OID, &ctx, &msg);
 111
 112                 buffer_append(&b, msg.value, msg.length);
 113                 buffer_put_char(&b, '\n');
 114
 115                 gss_release_buffer(&lmin, &msg);
 116         } while (ctx != 0);
 117
 118         /* The mechanism specific error */
 119         do {
 120                 gss_display_status(&lmin, ctxt->minor,
 121                     GSS_C_MECH_CODE, GSS_C_NULL_OID, &ctx, &msg);
 122
 123                 buffer_append(&b, msg.value, msg.length);
 124                 buffer_put_char(&b, '\n');
 125
 126                 gss_release_buffer(&lmin, &msg);
 127         } while (ctx != 0);
 128
 129         buffer_put_char(&b, '\0');
 130         ret = xmalloc(buffer_len(&b));
 131         buffer_get(&b, ret, buffer_len(&b));
 132         buffer_free(&b);
 133         return (ret);
 134 }
 135
 136 /*
 137  * Initialise our GSSAPI context. We use this opaque structure to contain all
 138  * of the data which both the client and server need to persist across
 139  * {accept,init}_sec_context calls, so that when we do it from the userauth
 140  * stuff life is a little easier
 141  */
 142 void
 143 ssh_gssapi_build_ctx(Gssctxt **ctx)
 144 {
 145         *ctx = xcalloc(1, sizeof (Gssctxt));
 146         (*ctx)->context = GSS_C_NO_CONTEXT;
 147         (*ctx)->name = GSS_C_NO_NAME;
 148         (*ctx)->oid = GSS_C_NO_OID;
 149         (*ctx)->creds = GSS_C_NO_CREDENTIAL;
 150         (*ctx)->client = GSS_C_NO_NAME;
 151         (*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
 152 }
 153
 154 /* Delete our context, providing it has been built correctly */
 155 void
 156 ssh_gssapi_delete_ctx(Gssctxt **ctx)
 157 {
 158         OM_uint32 ms;
 159
 160         if ((*ctx) == NULL)
 161                 return;
 162         if ((*ctx)->context != GSS_C_NO_CONTEXT)
 163                 gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
 164         if ((*ctx)->name != GSS_C_NO_NAME)
 165                 gss_release_name(&ms, &(*ctx)->name);
 166         if ((*ctx)->oid != GSS_C_NO_OID) {
 167                 xfree((*ctx)->oid->elements);
 168                 xfree((*ctx)->oid);
 169                 (*ctx)->oid = GSS_C_NO_OID;
 170         }
 171         if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
 172                 gss_release_cred(&ms, &(*ctx)->creds);
 173         if ((*ctx)->client != GSS_C_NO_NAME)
 174                 gss_release_name(&ms, &(*ctx)->client);
 175         if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
 176                 gss_release_cred(&ms, &(*ctx)->client_creds);
 177
 178         xfree(*ctx);
 179         *ctx = NULL;
 180 }
 181
 182 /*
 183  * Wrapper to init_sec_context
 184  * Requires that the context contains:
 185  *      oid
 186  *      server name (from ssh_gssapi_import_name)
 187  */
 188 OM_uint32
 189 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
 190     gss_buffer_desc* send_tok, OM_uint32 *flags)
 191 {
 192         int deleg_flag = 0;
 193
 194         if (deleg_creds) {
 195                 deleg_flag = GSS_C_DELEG_FLAG;
 196                 debug("Delegating credentials");
 197         }
 198
 199         ctx->major = gss_init_sec_context(&ctx->minor,
 200             GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
 201             GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
 202             0, NULL, recv_tok, NULL, send_tok, flags, NULL);
 203
 204         if (GSS_ERROR(ctx->major))
 205                 ssh_gssapi_error(ctx);
 206
 207         return (ctx->major);
 208 }
 209
 210 /* Create a service name for the given host */
 211 OM_uint32
 212 ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
 213 {
 214         gss_buffer_desc gssbuf;
 215         char *val;
 216
 217         xasprintf(&val, "host@%s", host);
 218         gssbuf.value = val;
 219         gssbuf.length = strlen(gssbuf.value);
 220
 221         if ((ctx->major = gss_import_name(&ctx->minor,
 222             &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
 223                 ssh_gssapi_error(ctx);
 224
 225         xfree(gssbuf.value);
 226         return (ctx->major);
 227 }
 228
 229 /* Acquire credentials for a server running on the current host.
 230  * Requires that the context structure contains a valid OID
 231  */
 232
 233 /* Returns a GSSAPI error code */
 234 OM_uint32
 235 ssh_gssapi_acquire_cred(Gssctxt *ctx)
 236 {
 237         OM_uint32 status;
 238         char lname[MAXHOSTNAMELEN];
 239         gss_OID_set oidset;
 240
 241         gss_create_empty_oid_set(&status, &oidset);
 242         gss_add_oid_set_member(&status, ctx->oid, &oidset);
 243
 244         if (gethostname(lname, MAXHOSTNAMELEN)) {
 245                 gss_release_oid_set(&status, &oidset);
 246                 return (-1);
 247         }
 248
 249         if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
 250                 gss_release_oid_set(&status, &oidset);
 251                 return (ctx->major);
 252         }
 253
 254         if ((ctx->major = gss_acquire_cred(&ctx->minor,
 255             ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL)))
 256                 ssh_gssapi_error(ctx);
 257
 258         gss_release_oid_set(&status, &oidset);
 259         return (ctx->major);
 260 }
 261
 262 OM_uint32
 263 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
 264 {
 265         if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
 266             GSS_C_QOP_DEFAULT, buffer, hash)))
 267                 ssh_gssapi_error(ctx);
 268
 269         return (ctx->major);
 270 }
 271
 272 void
 273 ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
 274     const char *context)
 275 {
 276         buffer_init(b);
 277         buffer_put_string(b, session_id2, session_id2_len);
 278         buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
 279         buffer_put_cstring(b, user);
 280         buffer_put_cstring(b, service);
 281         buffer_put_cstring(b, context);
 282 }
 283
 284 OM_uint32
 285 ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
 286 {
 287         if (*ctx)
 288                 ssh_gssapi_delete_ctx(ctx);
 289         ssh_gssapi_build_ctx(ctx);
 290         ssh_gssapi_set_oid(*ctx, oid);
 291         return (ssh_gssapi_acquire_cred(*ctx));
 292 }
 293
 294 int
 295 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, char *host)
 296 {
 297         gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
 298         OM_uint32 major, minor;
 299         gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
 300
 301         /* RFC 4462 says we MUST NOT do SPNEGO */
 302         if (oid->length == spnego_oid.length &&
 303             (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
 304                 return -1;
 305
 306         ssh_gssapi_build_ctx(ctx);
 307         ssh_gssapi_set_oid(*ctx, oid);
 308         major = ssh_gssapi_import_name(*ctx, host);
 309         if (!GSS_ERROR(major)) {
 310                 major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
 311                     NULL);
 312                 gss_release_buffer(&minor, &token);
 313                 gss_delete_sec_context(&minor, &(*ctx)->context,
 314                     GSS_C_NO_BUFFER);
 315         }
 316
 317         if (GSS_ERROR(major))
 318                 ssh_gssapi_delete_ctx(ctx);
 319
 320         return (!GSS_ERROR(major));
 321 }
 322
 323 #endif /* GSSAPI */