auth2-gss.c revision 295367
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 49extern ServerOptions options; 50 51static int input_gssapi_token(int type, u_int32_t plen, void *ctxt); 52static int input_gssapi_mic(int type, u_int32_t plen, void *ctxt); 53static int input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); 54static 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 */ 60static int 61userauth_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 129static int 130input_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 184static int 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 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 225static int 226input_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 252static int 253input_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 293Authmethod method_gssapi = { 294 "gssapi-with-mic", 295 userauth_gssapi, 296 &options.gss_authentication 297}; 298 299#endif /* GSSAPI */ 300