auth2-gss.c revision 1.20
1/* $OpenBSD: auth2-gss.c,v 1.20 2013/05/17 00:13:13 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 free(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 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 void 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} 182 183static void 184input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) 185{ 186 Authctxt *authctxt = ctxt; 187 Gssctxt *gssctxt; 188 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 189 gss_buffer_desc recv_tok; 190 OM_uint32 maj_status; 191 u_int len; 192 193 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 194 fatal("No authentication or GSSAPI context"); 195 196 gssctxt = authctxt->methoddata; 197 recv_tok.value = packet_get_string(&len); 198 recv_tok.length = len; 199 200 packet_check_eom(); 201 202 /* Push the error token into GSSAPI to see what it says */ 203 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 204 &send_tok, NULL)); 205 206 free(recv_tok.value); 207 208 /* We can't return anything to the client, even if we wanted to */ 209 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 210 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 211 212 /* The client will have already moved on to the next auth */ 213 214 gss_release_buffer(&maj_status, &send_tok); 215} 216 217/* 218 * This is called when the client thinks we've completed authentication. 219 * It should only be enabled in the dispatch handler by the function above, 220 * which only enables it once the GSSAPI exchange is complete. 221 */ 222 223static void 224input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 225{ 226 Authctxt *authctxt = ctxt; 227 int authenticated; 228 229 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 230 fatal("No authentication or GSSAPI context"); 231 232 /* 233 * We don't need to check the status, because we're only enabled in 234 * the dispatcher once the exchange is complete 235 */ 236 237 packet_check_eom(); 238 239 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 240 241 authctxt->postponed = 0; 242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 244 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 245 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 246 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 247} 248 249static void 250input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 251{ 252 Authctxt *authctxt = ctxt; 253 Gssctxt *gssctxt; 254 int authenticated = 0; 255 Buffer b; 256 gss_buffer_desc mic, gssbuf; 257 u_int len; 258 259 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 260 fatal("No authentication or GSSAPI context"); 261 262 gssctxt = authctxt->methoddata; 263 264 mic.value = packet_get_string(&len); 265 mic.length = len; 266 267 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 268 "gssapi-with-mic"); 269 270 gssbuf.value = buffer_ptr(&b); 271 gssbuf.length = buffer_len(&b); 272 273 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 274 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 275 else 276 logit("GSSAPI MIC check failed"); 277 278 buffer_free(&b); 279 free(mic.value); 280 281 authctxt->postponed = 0; 282 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 283 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 284 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 285 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 286 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 287} 288 289Authmethod method_gssapi = { 290 "gssapi-with-mic", 291 userauth_gssapi, 292 &options.gss_authentication 293}; 294#endif 295