auth2-gss.c

   1 /* $OpenBSD: auth2-gss.c,v 1.14 2006/03/25 22:22:42 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 "auth.h"
  32 #include "ssh2.h"
  33 #include "xmalloc.h"
  34 #include "log.h"
  35 #include "dispatch.h"
  36 #include "servconf.h"
  37 #include "packet.h"
  38 #include "monitor_wrap.h"
  39
  40 #include "ssh-gss.h"
  41
  42 extern ServerOptions options;
  43
  44 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  45 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
  46 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  47 static void input_gssapi_errtok(int, u_int32_t, void *);
  48
  49 /*
  50  * We only support those mechanisms that we know about (ie ones that we know
  51  * how to check local user kuserok and the like)
  52  */
  53 static int
  54 userauth_gssapi(Authctxt *authctxt)
  55 {
  56         gss_OID_desc goid = {0, NULL};
  57         Gssctxt *ctxt = NULL;
  58         int mechs;
  59         gss_OID_set supported;
  60         int present;
  61         OM_uint32 ms;
  62         u_int len;
  63         u_char *doid = NULL;
  64
  65         if (!authctxt->valid || authctxt->user == NULL)
  66                 return (0);
  67
  68         mechs = packet_get_int();
  69         if (mechs == 0) {
  70                 debug("Mechanism negotiation is not supported");
  71                 return (0);
  72         }
  73
  74         ssh_gssapi_supported_oids(&supported);
  75         do {
  76                 mechs--;
  77
  78                 if (doid)
  79                         xfree(doid);
  80
  81                 present = 0;
  82                 doid = packet_get_string(&len);
  83
  84                 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
  85                     doid[1] == len - 2) {
  86                         goid.elements = doid + 2;
  87                         goid.length   = len - 2;
  88                         gss_test_oid_set_member(&ms, &goid, supported,
  89                             &present);
  90                 } else {
  91                         logit("Badly formed OID received");
  92                 }
  93         } while (mechs > 0 && !present);
  94
  95         gss_release_oid_set(&ms, &supported);
  96
  97         if (!present) {
  98                 xfree(doid);
  99                 return (0);
 100         }
 101
 102         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 103                 if (ctxt != NULL)
 104                         ssh_gssapi_delete_ctx(&ctxt);
 105                 xfree(doid);
 106                 return (0);
 107         }
 108
 109         authctxt->methoddata = (void *)ctxt;
 110
 111         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 112
 113         /* Return the OID that we received */
 114         packet_put_string(doid, len);
 115
 116         packet_send();
 117         xfree(doid);
 118
 119         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 120         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 121         authctxt->postponed = 1;
 122
 123         return (0);
 124 }
 125
 126 static void
 127 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 128 {
 129         Authctxt *authctxt = ctxt;
 130         Gssctxt *gssctxt;
 131         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 132         gss_buffer_desc recv_tok;
 133         OM_uint32 maj_status, min_status, flags;
 134         u_int len;
 135
 136         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 137                 fatal("No authentication or GSSAPI context");
 138
 139         gssctxt = authctxt->methoddata;
 140         recv_tok.value = packet_get_string(&len);
 141         recv_tok.length = len; /* u_int vs. size_t */
 142
 143         packet_check_eom();
 144
 145         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 146             &send_tok, &flags));
 147
 148         xfree(recv_tok.value);
 149
 150         if (GSS_ERROR(maj_status)) {
 151                 if (send_tok.length != 0) {
 152                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 153                         packet_put_string(send_tok.value, send_tok.length);
 154                         packet_send();
 155                 }
 156                 authctxt->postponed = 0;
 157                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 158                 userauth_finish(authctxt, 0, "gssapi-with-mic");
 159         } else {
 160                 if (send_tok.length != 0) {
 161                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 162                         packet_put_string(send_tok.value, send_tok.length);
 163                         packet_send();
 164                 }
 165                 if (maj_status == GSS_S_COMPLETE) {
 166                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 167                         if (flags & GSS_C_INTEG_FLAG)
 168                                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
 169                                     &input_gssapi_mic);
 170                         else
 171                                 dispatch_set(
 172                                     SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 173                                     &input_gssapi_exchange_complete);
 174                 }
 175         }
 176
 177         gss_release_buffer(&min_status, &send_tok);
 178 }
 179
 180 static void
 181 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 182 {
 183         Authctxt *authctxt = ctxt;
 184         Gssctxt *gssctxt;
 185         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 186         gss_buffer_desc recv_tok;
 187         OM_uint32 maj_status;
 188         u_int len;
 189
 190         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 191                 fatal("No authentication or GSSAPI context");
 192
 193         gssctxt = authctxt->methoddata;
 194         recv_tok.value = packet_get_string(&len);
 195         recv_tok.length = len;
 196
 197         packet_check_eom();
 198
 199         /* Push the error token into GSSAPI to see what it says */
 200         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 201             &send_tok, NULL));
 202
 203         xfree(recv_tok.value);
 204
 205         /* We can't return anything to the client, even if we wanted to */
 206         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 207         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 208
 209         /* The client will have already moved on to the next auth */
 210
 211         gss_release_buffer(&maj_status, &send_tok);
 212 }
 213
 214 /*
 215  * This is called when the client thinks we've completed authentication.
 216  * It should only be enabled in the dispatch handler by the function above,
 217  * which only enables it once the GSSAPI exchange is complete.
 218  */
 219
 220 static void
 221 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
 222 {
 223         Authctxt *authctxt = ctxt;
 224         Gssctxt *gssctxt;
 225         int authenticated;
 226
 227         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 228                 fatal("No authentication or GSSAPI context");
 229
 230         gssctxt = authctxt->methoddata;
 231
 232         /*
 233          * We don't need to check the status, because we're only enabled in
 234          * the dispatcher once the exchange is complete
 235          */
 236
 237         packet_check_eom();
 238
 239         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 240
 241         authctxt->postponed = 0;
 242         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 243         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 244         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 245         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 246         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 247 }
 248
 249 static void
 250 input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
 251 {
 252         Authctxt *authctxt = ctxt;
 253         Gssctxt *gssctxt;
 254         int authenticated = 0;
 255         Buffer b;
 256         gss_buffer_desc mic, gssbuf;
 257         u_int len;
 258
 259         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 260                 fatal("No authentication or GSSAPI context");
 261
 262         gssctxt = authctxt->methoddata;
 263
 264         mic.value = packet_get_string(&len);
 265         mic.length = len;
 266
 267         ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
 268             "gssapi-with-mic");
 269
 270         gssbuf.value = buffer_ptr(&b);
 271         gssbuf.length = buffer_len(&b);
 272
 273         if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 274                 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 275         else
 276                 logit("GSSAPI MIC check failed");
 277
 278         buffer_free(&b);
 279         xfree(mic.value);
 280
 281         authctxt->postponed = 0;
 282         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 283         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 284         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 285         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 286         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 287 }
 288
 289 Authmethod method_gssapi = {
 290         "gssapi-with-mic",
 291         userauth_gssapi,
 292         &options.gss_authentication
 293 };
 294
 295 #endif /* GSSAPI */