crypto/openssh/auth2-gss.c

   1 /* $OpenBSD: auth2-gss.c,v 1.22 2015/01/19 20:07:45 markus 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 "misc.h"
  44 #include "servconf.h"
  45 #include "packet.h"
  46 #include "ssh-gss.h"
  47 #include "monitor_wrap.h"
  48
  49 extern ServerOptions options;
  50
  51 static int input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  52 static int input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
  53 static int input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  54 static int input_gssapi_errtok(int, u_int32_t, void *);
  55
  56 /*
  57  * We only support those mechanisms that we know about (ie ones that we know
  58  * how to check local user kuserok and the like)
  59  */
  60 static int
  61 userauth_gssapi(Authctxt *authctxt)
  62 {
  63         gss_OID_desc goid = {0, NULL};
  64         Gssctxt *ctxt = NULL;
  65         int mechs;
  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         do {
  81                 mechs--;
  82
  83                 free(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                         ssh_gssapi_test_oid_supported(&ms, &goid, &present);
  93                 } else {
  94                         logit("Badly formed OID received");
  95                 }
  96         } while (mechs > 0 && !present);
  97
  98         if (!present) {
  99                 free(doid);
 100                 authctxt->server_caused_failure = 1;
 101                 return (0);
 102         }
 103
 104         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 105                 if (ctxt != NULL)
 106                         ssh_gssapi_delete_ctx(&ctxt);
 107                 free(doid);
 108                 authctxt->server_caused_failure = 1;
 109                 return (0);
 110         }
 111
 112         authctxt->methoddata = (void *)ctxt;
 113
 114         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 115
 116         /* Return the OID that we received */
 117         packet_put_string(doid, len);
 118
 119         packet_send();
 120         free(doid);
 121
 122         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 123         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 124         authctxt->postponed = 1;
 125
 126         return (0);
 127 }
 128
 129 static int
 130 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 131 {
 132         Authctxt *authctxt = ctxt;
 133         Gssctxt *gssctxt;
 134         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 135         gss_buffer_desc recv_tok;
 136         OM_uint32 maj_status, min_status, flags;
 137         u_int len;
 138
 139         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 140                 fatal("No authentication or GSSAPI context");
 141
 142         gssctxt = authctxt->methoddata;
 143         recv_tok.value = packet_get_string(&len);
 144         recv_tok.length = len; /* u_int vs. size_t */
 145
 146         packet_check_eom();
 147
 148         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 149             &send_tok, &flags));
 150
 151         free(recv_tok.value);
 152
 153         if (GSS_ERROR(maj_status)) {
 154                 if (send_tok.length != 0) {
 155                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 156                         packet_put_string(send_tok.value, send_tok.length);
 157                         packet_send();
 158                 }
 159                 authctxt->postponed = 0;
 160                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 161                 userauth_finish(authctxt, 0, "gssapi-with-mic", NULL);
 162         } else {
 163                 if (send_tok.length != 0) {
 164                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 165                         packet_put_string(send_tok.value, send_tok.length);
 166                         packet_send();
 167                 }
 168                 if (maj_status == GSS_S_COMPLETE) {
 169                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 170                         if (flags & GSS_C_INTEG_FLAG)
 171                                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
 172                                     &input_gssapi_mic);
 173                         else
 174                                 dispatch_set(
 175                                     SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 176                                     &input_gssapi_exchange_complete);
 177                 }
 178         }
 179
 180         gss_release_buffer(&min_status, &send_tok);
 181         return 0;
 182 }
 183
 184 static int
 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         free(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         return 0;
 217 }
 218
 219 /*
 220  * This is called when the client thinks we've completed authentication.
 221  * It should only be enabled in the dispatch handler by the function above,
 222  * which only enables it once the GSSAPI exchange is complete.
 223  */
 224
 225 static int
 226 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
 227 {
 228         Authctxt *authctxt = ctxt;
 229         int authenticated;
 230
 231         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 232                 fatal("No authentication or GSSAPI context");
 233
 234         /*
 235          * We don't need to check the status, because we're only enabled in
 236          * the dispatcher once the exchange is complete
 237          */
 238
 239         packet_check_eom();
 240
 241         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 242
 243         authctxt->postponed = 0;
 244         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 245         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 246         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 247         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 248         userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
 249         return 0;
 250 }
 251
 252 static int
 253 input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
 254 {
 255         Authctxt *authctxt = ctxt;
 256         Gssctxt *gssctxt;
 257         int authenticated = 0;
 258         Buffer b;
 259         gss_buffer_desc mic, gssbuf;
 260         u_int len;
 261
 262         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 263                 fatal("No authentication or GSSAPI context");
 264
 265         gssctxt = authctxt->methoddata;
 266
 267         mic.value = packet_get_string(&len);
 268         mic.length = len;
 269
 270         ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
 271             "gssapi-with-mic");
 272
 273         gssbuf.value = buffer_ptr(&b);
 274         gssbuf.length = buffer_len(&b);
 275
 276         if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 277                 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 278         else
 279                 logit("GSSAPI MIC check failed");
 280
 281         buffer_free(&b);
 282         free(mic.value);
 283
 284         authctxt->postponed = 0;
 285         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 286         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 287         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 288         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 289         userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL);
 290         return 0;
 291 }
 292
 293 Authmethod method_gssapi = {
 294         "gssapi-with-mic",
 295         userauth_gssapi,
 296         &options.gss_authentication
 297 };
 298
 299 #endif /* GSSAPI */