auth2-gss.c

   1 /* $OpenBSD: auth2-gss.c,v 1.15 2006/08/03 03:34:41 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 "xmalloc.h"
  34 #include "key.h"
  35 #include "hostfile.h"
  36 #include "auth.h"
  37 #include "ssh2.h"
  38 #include "log.h"
  39 #include "dispatch.h"
  40 #include "buffer.h"
  41 #include "servconf.h"
  42 #include "packet.h"
  43 #include "ssh-gss.h"
  44 #include "monitor_wrap.h"
  45
  46 extern ServerOptions options;
  47
  48 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  49 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
  50 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  51 static void input_gssapi_errtok(int, u_int32_t, void *);
  52
  53 /*
  54  * We only support those mechanisms that we know about (ie ones that we know
  55  * how to check local user kuserok and the like)
  56  */
  57 static int
  58 userauth_gssapi(Authctxt *authctxt)
  59 {
  60         gss_OID_desc goid = {0, NULL};
  61         Gssctxt *ctxt = NULL;
  62         int mechs;
  63         gss_OID_set supported;
  64         int present;
  65         OM_uint32 ms;
  66         u_int len;
  67         u_char *doid = NULL;
  68
  69         if (!authctxt->valid || authctxt->user == NULL)
  70                 return (0);
  71
  72         mechs = packet_get_int();
  73         if (mechs == 0) {
  74                 debug("Mechanism negotiation is not supported");
  75                 return (0);
  76         }
  77
  78         ssh_gssapi_supported_oids(&supported);
  79         do {
  80                 mechs--;
  81
  82                 if (doid)
  83                         xfree(doid);
  84
  85                 present = 0;
  86                 doid = packet_get_string(&len);
  87
  88                 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
  89                     doid[1] == len - 2) {
  90                         goid.elements = doid + 2;
  91                         goid.length   = len - 2;
  92                         gss_test_oid_set_member(&ms, &goid, supported,
  93                             &present);
  94                 } else {
  95                         logit("Badly formed OID received");
  96                 }
  97         } while (mechs > 0 && !present);
  98
  99         gss_release_oid_set(&ms, &supported);
 100
 101         if (!present) {
 102                 xfree(doid);
 103                 return (0);
 104         }
 105
 106         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 107                 if (ctxt != NULL)
 108                         ssh_gssapi_delete_ctx(&ctxt);
 109                 xfree(doid);
 110                 return (0);
 111         }
 112
 113         authctxt->methoddata = (void *)ctxt;
 114
 115         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 116
 117         /* Return the OID that we received */
 118         packet_put_string(doid, len);
 119
 120         packet_send();
 121         xfree(doid);
 122
 123         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 124         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 125         authctxt->postponed = 1;
 126
 127         return (0);
 128 }
 129
 130 static void
 131 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 132 {
 133         Authctxt *authctxt = ctxt;
 134         Gssctxt *gssctxt;
 135         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 136         gss_buffer_desc recv_tok;
 137         OM_uint32 maj_status, min_status, flags;
 138         u_int len;
 139
 140         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 141                 fatal("No authentication or GSSAPI context");
 142
 143         gssctxt = authctxt->methoddata;
 144         recv_tok.value = packet_get_string(&len);
 145         recv_tok.length = len; /* u_int vs. size_t */
 146
 147         packet_check_eom();
 148
 149         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 150             &send_tok, &flags));
 151
 152         xfree(recv_tok.value);
 153
 154         if (GSS_ERROR(maj_status)) {
 155                 if (send_tok.length != 0) {
 156                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 157                         packet_put_string(send_tok.value, send_tok.length);
 158                         packet_send();
 159                 }
 160                 authctxt->postponed = 0;
 161                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 162                 userauth_finish(authctxt, 0, "gssapi-with-mic");
 163         } else {
 164                 if (send_tok.length != 0) {
 165                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 166                         packet_put_string(send_tok.value, send_tok.length);
 167                         packet_send();
 168                 }
 169                 if (maj_status == GSS_S_COMPLETE) {
 170                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 171                         if (flags & GSS_C_INTEG_FLAG)
 172                                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
 173                                     &input_gssapi_mic);
 174                         else
 175                                 dispatch_set(
 176                                     SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 177                                     &input_gssapi_exchange_complete);
 178                 }
 179         }
 180
 181         gss_release_buffer(&min_status, &send_tok);
 182 }
 183
 184 static void
 185 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 186 {
 187         Authctxt *authctxt = ctxt;
 188         Gssctxt *gssctxt;
 189         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 190         gss_buffer_desc recv_tok;
 191         OM_uint32 maj_status;
 192         u_int len;
 193
 194         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 195                 fatal("No authentication or GSSAPI context");
 196
 197         gssctxt = authctxt->methoddata;
 198         recv_tok.value = packet_get_string(&len);
 199         recv_tok.length = len;
 200
 201         packet_check_eom();
 202
 203         /* Push the error token into GSSAPI to see what it says */
 204         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 205             &send_tok, NULL));
 206
 207         xfree(recv_tok.value);
 208
 209         /* We can't return anything to the client, even if we wanted to */
 210         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 211         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 212
 213         /* The client will have already moved on to the next auth */
 214
 215         gss_release_buffer(&maj_status, &send_tok);
 216 }
 217
 218 /*
 219  * This is called when the client thinks we've completed authentication.
 220  * It should only be enabled in the dispatch handler by the function above,
 221  * which only enables it once the GSSAPI exchange is complete.
 222  */
 223
 224 static void
 225 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
 226 {
 227         Authctxt *authctxt = ctxt;
 228         Gssctxt *gssctxt;
 229         int authenticated;
 230
 231         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 232                 fatal("No authentication or GSSAPI context");
 233
 234         gssctxt = authctxt->methoddata;
 235
 236         /*
 237          * We don't need to check the status, because we're only enabled in
 238          * the dispatcher once the exchange is complete
 239          */
 240
 241         packet_check_eom();
 242
 243         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 244
 245         authctxt->postponed = 0;
 246         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 247         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 248         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 249         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 250         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 251 }
 252
 253 static void
 254 input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
 255 {
 256         Authctxt *authctxt = ctxt;
 257         Gssctxt *gssctxt;
 258         int authenticated = 0;
 259         Buffer b;
 260         gss_buffer_desc mic, gssbuf;
 261         u_int len;
 262
 263         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 264                 fatal("No authentication or GSSAPI context");
 265
 266         gssctxt = authctxt->methoddata;
 267
 268         mic.value = packet_get_string(&len);
 269         mic.length = len;
 270
 271         ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
 272             "gssapi-with-mic");
 273
 274         gssbuf.value = buffer_ptr(&b);
 275         gssbuf.length = buffer_len(&b);
 276
 277         if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 278                 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 279         else
 280                 logit("GSSAPI MIC check failed");
 281
 282         buffer_free(&b);
 283         xfree(mic.value);
 284
 285         authctxt->postponed = 0;
 286         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 287         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 288         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 289         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 290         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 291 }
 292
 293 Authmethod method_gssapi = {
 294         "gssapi-with-mic",
 295         userauth_gssapi,
 296         &options.gss_authentication
 297 };
 298
 299 #endif /* GSSAPI */