auth2-gss.c

   1 /*      $OpenBSD: auth2-gss.c,v 1.10 2005/07/17 07:17:54 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 "compat.h"
  38 #include "packet.h"
  39 #include "monitor_wrap.h"
  40
  41 #include "ssh-gss.h"
  42
  43 extern ServerOptions options;
  44
  45 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt);
  46 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt);
  47 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt);
  48 static void input_gssapi_errtok(int, u_int32_t, void *);
  49
  50 /*
  51  * We only support those mechanisms that we know about (ie ones that we know
  52  * how to check local user kuserok and the like
  53  */
  54 static int
  55 userauth_gssapi(Authctxt *authctxt)
  56 {
  57         gss_OID_desc goid = {0, NULL};
  58         Gssctxt *ctxt = NULL;
  59         int mechs;
  60         gss_OID_set supported;
  61         int present;
  62         OM_uint32 ms;
  63         u_int len;
  64         u_char *doid = NULL;
  65
  66         if (!authctxt->valid || authctxt->user == NULL)
  67                 return (0);
  68
  69         mechs = packet_get_int();
  70         if (mechs == 0) {
  71                 debug("Mechanism negotiation is not supported");
  72                 return (0);
  73         }
  74
  75         ssh_gssapi_supported_oids(&supported);
  76         do {
  77                 mechs--;
  78
  79                 if (doid)
  80                         xfree(doid);
  81
  82                 present = 0;
  83                 doid = packet_get_string(&len);
  84
  85                 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE &&
  86                     doid[1] == len - 2) {
  87                         goid.elements = doid + 2;
  88                         goid.length   = len - 2;
  89                         gss_test_oid_set_member(&ms, &goid, supported,
  90                             &present);
  91                 } else {
  92                         logit("Badly formed OID received");
  93                 }
  94         } while (mechs > 0 && !present);
  95
  96         gss_release_oid_set(&ms, &supported);
  97
  98         if (!present) {
  99                 xfree(doid);
 100                 return (0);
 101         }
 102
 103         if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) {
 104                 xfree(doid);
 105                 return (0);
 106         }
 107
 108         authctxt->methoddata=(void *)ctxt;
 109
 110         packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE);
 111
 112         /* Return the OID that we received */
 113         packet_put_string(doid, len);
 114
 115         packet_send();
 116         xfree(doid);
 117
 118         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token);
 119         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok);
 120         authctxt->postponed = 1;
 121
 122         return (0);
 123 }
 124
 125 static void
 126 input_gssapi_token(int type, u_int32_t plen, void *ctxt)
 127 {
 128         Authctxt *authctxt = ctxt;
 129         Gssctxt *gssctxt;
 130         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 131         gss_buffer_desc recv_tok;
 132         OM_uint32 maj_status, min_status, flags;
 133         u_int len;
 134
 135         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 136                 fatal("No authentication or GSSAPI context");
 137
 138         gssctxt = authctxt->methoddata;
 139         recv_tok.value = packet_get_string(&len);
 140         recv_tok.length = len; /* u_int vs. size_t */
 141
 142         packet_check_eom();
 143
 144         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 145             &send_tok, &flags));
 146
 147         xfree(recv_tok.value);
 148
 149         if (GSS_ERROR(maj_status)) {
 150                 if (send_tok.length != 0) {
 151                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK);
 152                         packet_put_string(send_tok.value, send_tok.length);
 153                         packet_send();
 154                 }
 155                 authctxt->postponed = 0;
 156                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 157                 userauth_finish(authctxt, 0, "gssapi-with-mic");
 158         } else {
 159                 if (send_tok.length != 0) {
 160                         packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN);
 161                         packet_put_string(send_tok.value, send_tok.length);
 162                         packet_send();
 163                 }
 164                 if (maj_status == GSS_S_COMPLETE) {
 165                         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 166                         if (flags & GSS_C_INTEG_FLAG)
 167                                 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC,
 168                                     &input_gssapi_mic);
 169                         else
 170                                 dispatch_set(
 171                                     SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE,
 172                                     &input_gssapi_exchange_complete);
 173                 }
 174         }
 175
 176         gss_release_buffer(&min_status, &send_tok);
 177 }
 178
 179 static void
 180 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt)
 181 {
 182         Authctxt *authctxt = ctxt;
 183         Gssctxt *gssctxt;
 184         gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER;
 185         gss_buffer_desc recv_tok;
 186         OM_uint32 maj_status;
 187         u_int len;
 188
 189         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 190                 fatal("No authentication or GSSAPI context");
 191
 192         gssctxt = authctxt->methoddata;
 193         recv_tok.value = packet_get_string(&len);
 194         recv_tok.length = len;
 195
 196         packet_check_eom();
 197
 198         /* Push the error token into GSSAPI to see what it says */
 199         maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok,
 200             &send_tok, NULL));
 201
 202         xfree(recv_tok.value);
 203
 204         /* We can't return anything to the client, even if we wanted to */
 205         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 206         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 207
 208         /* The client will have already moved on to the next auth */
 209
 210         gss_release_buffer(&maj_status, &send_tok);
 211 }
 212
 213 /*
 214  * This is called when the client thinks we've completed authentication.
 215  * It should only be enabled in the dispatch handler by the function above,
 216  * which only enables it once the GSSAPI exchange is complete.
 217  */
 218
 219 static void
 220 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt)
 221 {
 222         Authctxt *authctxt = ctxt;
 223         Gssctxt *gssctxt;
 224         int authenticated;
 225
 226         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 227                 fatal("No authentication or GSSAPI context");
 228
 229         gssctxt = authctxt->methoddata;
 230
 231         /*
 232          * We don't need to check the status, because we're only enabled in
 233          * the dispatcher once the exchange is complete
 234          */
 235
 236         packet_check_eom();
 237
 238         authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 239
 240         authctxt->postponed = 0;
 241         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 242         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 243         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 244         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 245         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 246 }
 247
 248 static void
 249 input_gssapi_mic(int type, u_int32_t plen, void *ctxt)
 250 {
 251         Authctxt *authctxt = ctxt;
 252         Gssctxt *gssctxt;
 253         int authenticated = 0;
 254         Buffer b;
 255         gss_buffer_desc mic, gssbuf;
 256         u_int len;
 257
 258         if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep))
 259                 fatal("No authentication or GSSAPI context");
 260
 261         gssctxt = authctxt->methoddata;
 262
 263         mic.value = packet_get_string(&len);
 264         mic.length = len;
 265
 266         ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service,
 267             "gssapi-with-mic");
 268
 269         gssbuf.value = buffer_ptr(&b);
 270         gssbuf.length = buffer_len(&b);
 271
 272         if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic))))
 273                 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user));
 274         else
 275                 logit("GSSAPI MIC check failed");
 276
 277         buffer_free(&b);
 278         xfree(mic.value);
 279
 280         authctxt->postponed = 0;
 281         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 282         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL);
 283         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL);
 284         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 285         userauth_finish(authctxt, authenticated, "gssapi-with-mic");
 286 }
 287
 288 Authmethod method_gssapi = {
 289         "gssapi-with-mic",
 290         userauth_gssapi,
 291         &options.gss_authentication
 292 };
 293
 294 #endif /* GSSAPI */