auth2-gss.c revision 1.19
1/* $OpenBSD: auth2-gss.c,v 1.19 2013/04/05 00:14:00 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#ifdef GSSAPI 28 29#include <sys/types.h> 30 31#include "xmalloc.h" 32#include "key.h" 33#include "hostfile.h" 34#include "auth.h" 35#include "ssh2.h" 36#include "log.h" 37#include "dispatch.h" 38#include "buffer.h" 39#include "servconf.h" 40#include "packet.h" 41#include "ssh-gss.h" 42#include "monitor_wrap.h" 43 44extern ServerOptions options; 45 46static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); 47static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); 48static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); 49static void input_gssapi_errtok(int, u_int32_t, void *); 50 51/* 52 * We only support those mechanisms that we know about (ie ones that we know 53 * how to check local user kuserok and the like) 54 */ 55static int 56userauth_gssapi(Authctxt *authctxt) 57{ 58 gss_OID_desc goid = {0, NULL}; 59 Gssctxt *ctxt = NULL; 60 int mechs; 61 gss_OID_set supported; 62 int present; 63 OM_uint32 ms; 64 u_int len; 65 u_char *doid = NULL; 66 67 if (!authctxt->valid || authctxt->user == NULL) 68 return (0); 69 70 mechs = packet_get_int(); 71 if (mechs == 0) { 72 debug("Mechanism negotiation is not supported"); 73 return (0); 74 } 75 76 ssh_gssapi_supported_oids(&supported); 77 do { 78 mechs--; 79 80 if (doid) 81 xfree(doid); 82 83 present = 0; 84 doid = packet_get_string(&len); 85 86 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && 87 doid[1] == len - 2) { 88 goid.elements = doid + 2; 89 goid.length = len - 2; 90 gss_test_oid_set_member(&ms, &goid, supported, 91 &present); 92 } else { 93 logit("Badly formed OID received"); 94 } 95 } while (mechs > 0 && !present); 96 97 gss_release_oid_set(&ms, &supported); 98 99 if (!present) { 100 xfree(doid); 101 authctxt->server_caused_failure = 1; 102 return (0); 103 } 104 105 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 106 if (ctxt != NULL) 107 ssh_gssapi_delete_ctx(&ctxt); 108 xfree(doid); 109 authctxt->server_caused_failure = 1; 110 return (0); 111 } 112 113 authctxt->methoddata = (void *)ctxt; 114 115 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); 116 117 /* Return the OID that we received */ 118 packet_put_string(doid, len); 119 120 packet_send(); 121 xfree(doid); 122 123 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 124 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 125 authctxt->postponed = 1; 126 127 return (0); 128} 129 130static void 131input_gssapi_token(int type, u_int32_t plen, void *ctxt) 132{ 133 Authctxt *authctxt = ctxt; 134 Gssctxt *gssctxt; 135 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 136 gss_buffer_desc recv_tok; 137 OM_uint32 maj_status, min_status, flags; 138 u_int len; 139 140 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 141 fatal("No authentication or GSSAPI context"); 142 143 gssctxt = authctxt->methoddata; 144 recv_tok.value = packet_get_string(&len); 145 recv_tok.length = len; /* u_int vs. size_t */ 146 147 packet_check_eom(); 148 149 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 150 &send_tok, &flags)); 151 152 xfree(recv_tok.value); 153 154 if (GSS_ERROR(maj_status)) { 155 if (send_tok.length != 0) { 156 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); 157 packet_put_string(send_tok.value, send_tok.length); 158 packet_send(); 159 } 160 authctxt->postponed = 0; 161 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 162 userauth_finish(authctxt, 0, "gssapi-with-mic", NULL); 163 } else { 164 if (send_tok.length != 0) { 165 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); 166 packet_put_string(send_tok.value, send_tok.length); 167 packet_send(); 168 } 169 if (maj_status == GSS_S_COMPLETE) { 170 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 171 if (flags & GSS_C_INTEG_FLAG) 172 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, 173 &input_gssapi_mic); 174 else 175 dispatch_set( 176 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 177 &input_gssapi_exchange_complete); 178 } 179 } 180 181 gss_release_buffer(&min_status, &send_tok); 182} 183 184static void 185input_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 xfree(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} 217 218/* 219 * This is called when the client thinks we've completed authentication. 220 * It should only be enabled in the dispatch handler by the function above, 221 * which only enables it once the GSSAPI exchange is complete. 222 */ 223 224static void 225input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 226{ 227 Authctxt *authctxt = ctxt; 228 int authenticated; 229 230 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 231 fatal("No authentication or GSSAPI context"); 232 233 /* 234 * We don't need to check the status, because we're only enabled in 235 * the dispatcher once the exchange is complete 236 */ 237 238 packet_check_eom(); 239 240 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 241 242 authctxt->postponed = 0; 243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 244 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 245 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 246 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 247 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 248} 249 250static void 251input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 252{ 253 Authctxt *authctxt = ctxt; 254 Gssctxt *gssctxt; 255 int authenticated = 0; 256 Buffer b; 257 gss_buffer_desc mic, gssbuf; 258 u_int len; 259 260 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 261 fatal("No authentication or GSSAPI context"); 262 263 gssctxt = authctxt->methoddata; 264 265 mic.value = packet_get_string(&len); 266 mic.length = len; 267 268 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 269 "gssapi-with-mic"); 270 271 gssbuf.value = buffer_ptr(&b); 272 gssbuf.length = buffer_len(&b); 273 274 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 275 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 276 else 277 logit("GSSAPI MIC check failed"); 278 279 buffer_free(&b); 280 xfree(mic.value); 281 282 authctxt->postponed = 0; 283 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 284 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 285 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 286 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 287 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 288} 289 290Authmethod method_gssapi = { 291 "gssapi-with-mic", 292 userauth_gssapi, 293 &options.gss_authentication 294}; 295#endif 296