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 <stdarg.h>
  34
  35 #include "xmalloc.h"
  36 #include "key.h"
  37 #include "hostfile.h"
  38 #include "auth.h"
  39 #include "ssh2.h"
  40 #include "log.h"
  41 #include "dispatch.h"
  42 #include "buffer.h"
  43 #include "servconf.h"
  44 #include "packet.h"
  45 #include "ssh-gss.h"
  46 #include "monitor_wrap.h"
  47
  48 extern ServerOptions options;
  49
  50 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  51 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
  52 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  53 static void input_gssapi_errtok(int, u_int32_t, void *);
  54
  55 /*
  56  * We only support those mechanisms that we know about (ie ones that we know
  57  * how to check local user kuserok and the like)
  58  */
  59 static int
  60 userauth_gssapi(Authctxt *authctxt)
  61 {
  62         gss_OID_desc goid = {0, NULL};
  63         Gssctxt *ctxt = NULL;
  64         int mechs;
  65         gss_OID_set supported;
  66         int present;
  67         OM_uint32 ms;
  68         u_int len;
  69         u_char *doid = NULL;
  70
  71         if (!authctxt->valid || authctxt->user == NULL)
  72                 return (0);
  73
  74         mechs = packet_get_int();
  75         if (mechs == 0) {
  76                 debug("Mechanism negotiation is not supported");
  77                 return (0);
  78         }
  79
  80         ssh_gssapi_supported_oids(&supported);
  81         do {
  82                 mechs--;
  83
  84                 if (doid)
  85                         xfree(doid);
  86
  87                 present = 0;
  88                 doid = packet_get_string(&len);
  89
  90                 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
  91                     doid[1] == len - 2) {
  92                         goid.elements = doid + 2;
  93                         goid.length   = len - 2;
  94                         gss_test_oid_set_member(&ms, &goid, supported,
  95                             &present);
  96                 } else {
  97                         logit("Badly formed OID received");
  98                 }
  99         } while (mechs > 0 && !present);
 100
 101         gss_release_oid_set(&ms, &supported);
 102
 103         if (!present) {
 104                 xfree(doid);
 105                 return (0);
 106         }
 107
 108         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 109                 if (ctxt != NULL)
 110                         ssh_gssapi_delete_ctx(&ctxt);
 111                 xfree(doid);
 112                 return (0);
 113         }
 114
 115         authctxt->methoddata = (void *)ctxt;
 116
 117         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 118
 119         /* Return the OID that we received */
 120         packet_put_string(doid, len);
 121
 122         packet_send();
 123         xfree(doid);
 124
 125         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 126         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 127         authctxt->postponed = 1;
 128
 129         return (0);
 130 }
 131
 132 static void
 133 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 134 {
 135         Authctxt *authctxt = ctxt;
 136         Gssctxt *gssctxt;
 137         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 138         gss_buffer_desc recv_tok;
 139         OM_uint32 maj_status, min_status, flags;
 140         u_int len;
 141
 142         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 143                 fatal("No authentication or GSSAPI context");
 144
 145         gssctxt = authctxt->methoddata;
 146         recv_tok.value = packet_get_string(&len);
 147         recv_tok.length = len; /* u_int vs. size_t */
 148
 149         packet_check_eom();
 150
 151         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 152             &send_tok, &flags));
 153
 154         xfree(recv_tok.value);
 155
 156         if (GSS_ERROR(maj_status)) {
 157                 if (send_tok.length != 0) {
 158                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 159                         packet_put_string(send_tok.value, send_tok.length);
 160                         packet_send();
 161                 }
 162                 authctxt->postponed = 0;
 163                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 164                 userauth_finish(authctxt, 0, "gssapi-with-mic");
 165         } else {
 166                 if (send_tok.length != 0) {
 167                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 168                         packet_put_string(send_tok.value, send_tok.length);
 169                         packet_send();
 170                 }
 171                 if (maj_status == GSS_S_COMPLETE) {
 172                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 173                         if (flags & GSS_C_INTEG_FLAG)
 174                                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
 175                                     &input_gssapi_mic);
 176                         else
 177                                 dispatch_set(
 178                                     SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 179                                     &input_gssapi_exchange_complete);
 180                 }
 181         }
 182
 183         gss_release_buffer(&min_status, &send_tok);
 184 }
 185
 186 static void
 187 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 188 {
 189         Authctxt *authctxt = ctxt;
 190         Gssctxt *gssctxt;
 191         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 192         gss_buffer_desc recv_tok;
 193         OM_uint32 maj_status;
 194         u_int len;
 195
 196         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 197                 fatal("No authentication or GSSAPI context");
 198
 199         gssctxt = authctxt->methoddata;
 200         recv_tok.value = packet_get_string(&len);
 201         recv_tok.length = len;
 202
 203         packet_check_eom();
 204
 205         /* Push the error token into GSSAPI to see what it says */
 206         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 207             &send_tok, NULL));
 208
 209         xfree(recv_tok.value);
 210
 211         /* We can't return anything to the client, even if we wanted to */
 212         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 213         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 214
 215         /* The client will have already moved on to the next auth */
 216
 217         gss_release_buffer(&maj_status, &send_tok);
 218 }
 219
 220 /*
 221  * This is called when the client thinks we've completed authentication.
 222  * It should only be enabled in the dispatch handler by the function above,
 223  * which only enables it once the GSSAPI exchange is complete.
 224  */
 225
 226 static void
 227 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
 228 {
 229         Authctxt *authctxt = ctxt;
 230         Gssctxt *gssctxt;
 231         int authenticated;
 232
 233         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 234                 fatal("No authentication or GSSAPI context");
 235
 236         gssctxt = authctxt->methoddata;
 237
 238         /*
 239          * We don't need to check the status, because we're only enabled in
 240          * the dispatcher once the exchange is complete
 241          */
 242
 243         packet_check_eom();
 244
 245         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 246
 247         authctxt->postponed = 0;
 248         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 249         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 250         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 251         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 252         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 253 }
 254
 255 static void
 256 input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
 257 {
 258         Authctxt *authctxt = ctxt;
 259         Gssctxt *gssctxt;
 260         int authenticated = 0;
 261         Buffer b;
 262         gss_buffer_desc mic, gssbuf;
 263         u_int len;
 264
 265         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 266                 fatal("No authentication or GSSAPI context");
 267
 268         gssctxt = authctxt->methoddata;
 269
 270         mic.value = packet_get_string(&len);
 271         mic.length = len;
 272
 273         ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
 274             "gssapi-with-mic");
 275
 276         gssbuf.value = buffer_ptr(&b);
 277         gssbuf.length = buffer_len(&b);
 278
 279         if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 280                 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 281         else
 282                 logit("GSSAPI MIC check failed");
 283
 284         buffer_free(&b);
 285         xfree(mic.value);
 286
 287         authctxt->postponed = 0;
 288         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 289         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 290         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 291         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 292         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 293 }
 294
 295 Authmethod method_gssapi = {
 296         "gssapi-with-mic",
 297         userauth_gssapi,
 298         &options.gss_authentication
 299 };
 300
 301 #endif /* GSSAPI */