auth2-gss.c revision 248619
1/* $OpenBSD: auth2-gss.c,v 1.18 2012/12/02 20:34:09 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 <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 48extern ServerOptions options; 49 50static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); 51static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); 52static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); 53static 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 */ 59static int 60userauth_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 authctxt->server_caused_failure = 1; 106 return (0); 107 } 108 109 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 110 if (ctxt != NULL) 111 ssh_gssapi_delete_ctx(&ctxt); 112 xfree(doid); 113 authctxt->server_caused_failure = 1; 114 return (0); 115 } 116 117 authctxt->methoddata = (void *)ctxt; 118 119 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); 120 121 /* Return the OID that we received */ 122 packet_put_string(doid, len); 123 124 packet_send(); 125 xfree(doid); 126 127 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 128 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 129 authctxt->postponed = 1; 130 131 return (0); 132} 133 134static void 135input_gssapi_token(int type, u_int32_t plen, void *ctxt) 136{ 137 Authctxt *authctxt = ctxt; 138 Gssctxt *gssctxt; 139 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 140 gss_buffer_desc recv_tok; 141 OM_uint32 maj_status, min_status, flags; 142 u_int len; 143 144 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 145 fatal("No authentication or GSSAPI context"); 146 147 gssctxt = authctxt->methoddata; 148 recv_tok.value = packet_get_string(&len); 149 recv_tok.length = len; /* u_int vs. size_t */ 150 151 packet_check_eom(); 152 153 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 154 &send_tok, &flags)); 155 156 xfree(recv_tok.value); 157 158 if (GSS_ERROR(maj_status)) { 159 if (send_tok.length != 0) { 160 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); 161 packet_put_string(send_tok.value, send_tok.length); 162 packet_send(); 163 } 164 authctxt->postponed = 0; 165 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 166 userauth_finish(authctxt, 0, "gssapi-with-mic", NULL); 167 } else { 168 if (send_tok.length != 0) { 169 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); 170 packet_put_string(send_tok.value, send_tok.length); 171 packet_send(); 172 } 173 if (maj_status == GSS_S_COMPLETE) { 174 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 175 if (flags & GSS_C_INTEG_FLAG) 176 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, 177 &input_gssapi_mic); 178 else 179 dispatch_set( 180 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 181 &input_gssapi_exchange_complete); 182 } 183 } 184 185 gss_release_buffer(&min_status, &send_tok); 186} 187 188static void 189input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) 190{ 191 Authctxt *authctxt = ctxt; 192 Gssctxt *gssctxt; 193 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 194 gss_buffer_desc recv_tok; 195 OM_uint32 maj_status; 196 u_int len; 197 198 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 199 fatal("No authentication or GSSAPI context"); 200 201 gssctxt = authctxt->methoddata; 202 recv_tok.value = packet_get_string(&len); 203 recv_tok.length = len; 204 205 packet_check_eom(); 206 207 /* Push the error token into GSSAPI to see what it says */ 208 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 209 &send_tok, NULL)); 210 211 xfree(recv_tok.value); 212 213 /* We can't return anything to the client, even if we wanted to */ 214 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 215 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 216 217 /* The client will have already moved on to the next auth */ 218 219 gss_release_buffer(&maj_status, &send_tok); 220} 221 222/* 223 * This is called when the client thinks we've completed authentication. 224 * It should only be enabled in the dispatch handler by the function above, 225 * which only enables it once the GSSAPI exchange is complete. 226 */ 227 228static void 229input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 230{ 231 Authctxt *authctxt = ctxt; 232 Gssctxt *gssctxt; 233 int authenticated; 234 235 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 236 fatal("No authentication or GSSAPI context"); 237 238 gssctxt = authctxt->methoddata; 239 240 /* 241 * We don't need to check the status, because we're only enabled in 242 * the dispatcher once the exchange is complete 243 */ 244 245 packet_check_eom(); 246 247 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 248 249 authctxt->postponed = 0; 250 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 251 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 252 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 253 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 254 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 255} 256 257static void 258input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 259{ 260 Authctxt *authctxt = ctxt; 261 Gssctxt *gssctxt; 262 int authenticated = 0; 263 Buffer b; 264 gss_buffer_desc mic, gssbuf; 265 u_int len; 266 267 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 268 fatal("No authentication or GSSAPI context"); 269 270 gssctxt = authctxt->methoddata; 271 272 mic.value = packet_get_string(&len); 273 mic.length = len; 274 275 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 276 "gssapi-with-mic"); 277 278 gssbuf.value = buffer_ptr(&b); 279 gssbuf.length = buffer_len(&b); 280 281 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 282 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 283 else 284 logit("GSSAPI MIC check failed"); 285 286 buffer_free(&b); 287 xfree(mic.value); 288 289 authctxt->postponed = 0; 290 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 291 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 292 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 293 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 294 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 295} 296 297Authmethod method_gssapi = { 298 "gssapi-with-mic", 299 userauth_gssapi, 300 &options.gss_authentication 301}; 302 303#endif /* GSSAPI */ 304