1 /* $OpenBSD: auth2-gss.c,v 1.16 2007/10/29 00:52:45 dtucker 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 48 extern ServerOptions options; 49 50 static void input_gssapi_token(int type, u_int32_t plen, void *ctxt); 51 static void input_gssapi_mic(int type, u_int32_t plen, void *ctxt); 52 static void input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt); 53 static 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 */ 59 static int 60 userauth_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 return (0); 106 } 107 108 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 109 if (ctxt != NULL) 110 ssh_gssapi_delete_ctx(&ctxt); 111 xfree(doid); 112 return (0); 113 } 114 115 authctxt->methoddata = (void *)ctxt; 116 117 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); 118 119 /* Return the OID that we received */ 120 packet_put_string(doid, len); 121 122 packet_send(); 123 xfree(doid); 124 125 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 126 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 127 authctxt->postponed = 1; 128 129 return (0); 130 } 131 132 static void 133 input_gssapi_token(int type, u_int32_t plen, void *ctxt) 134 { 135 Authctxt *authctxt = ctxt; 136 Gssctxt *gssctxt; 137 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 138 gss_buffer_desc recv_tok; 139 OM_uint32 maj_status, min_status, flags; 140 u_int len; 141 142 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 143 fatal("No authentication or GSSAPI context"); 144 145 gssctxt = authctxt->methoddata; 146 recv_tok.value = packet_get_string(&len); 147 recv_tok.length = len; /* u_int vs. size_t */ 148 149 packet_check_eom(); 150 151 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 152 &send_tok, &flags)); 153 154 xfree(recv_tok.value); 155 156 if (GSS_ERROR(maj_status)) { 157 if (send_tok.length != 0) { 158 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); 159 packet_put_string(send_tok.value, send_tok.length); 160 packet_send(); 161 } 162 authctxt->postponed = 0; 163 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 164 userauth_finish(authctxt, 0, "gssapi-with-mic"); 165 } else { 166 if (send_tok.length != 0) { 167 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); 168 packet_put_string(send_tok.value, send_tok.length); 169 packet_send(); 170 } 171 if (maj_status == GSS_S_COMPLETE) { 172 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 173 if (flags & GSS_C_INTEG_FLAG) 174 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, 175 &input_gssapi_mic); 176 else 177 dispatch_set( 178 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 179 &input_gssapi_exchange_complete); 180 } 181 } 182 183 gss_release_buffer(&min_status, &send_tok); 184 } 185 186 static void 187 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) 188 { 189 Authctxt *authctxt = ctxt; 190 Gssctxt *gssctxt; 191 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 192 gss_buffer_desc recv_tok; 193 OM_uint32 maj_status; 194 u_int len; 195 196 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 197 fatal("No authentication or GSSAPI context"); 198 199 gssctxt = authctxt->methoddata; 200 recv_tok.value = packet_get_string(&len); 201 recv_tok.length = len; 202 203 packet_check_eom(); 204 205 /* Push the error token into GSSAPI to see what it says */ 206 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 207 &send_tok, NULL)); 208 209 xfree(recv_tok.value); 210 211 /* We can't return anything to the client, even if we wanted to */ 212 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 213 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 214 215 /* The client will have already moved on to the next auth */ 216 217 gss_release_buffer(&maj_status, &send_tok); 218 } 219 220 /* 221 * This is called when the client thinks we've completed authentication. 222 * It should only be enabled in the dispatch handler by the function above, 223 * which only enables it once the GSSAPI exchange is complete. 224 */ 225 226 static void 227 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 228 { 229 Authctxt *authctxt = ctxt; 230 Gssctxt *gssctxt; 231 int authenticated; 232 233 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 234 fatal("No authentication or GSSAPI context"); 235 236 gssctxt = authctxt->methoddata; 237 238 /* 239 * We don't need to check the status, because we're only enabled in 240 * the dispatcher once the exchange is complete 241 */ 242 243 packet_check_eom(); 244 245 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 246 247 authctxt->postponed = 0; 248 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 249 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 250 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 251 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 252 userauth_finish(authctxt, authenticated, "gssapi-with-mic"); 253 } 254 255 static void 256 input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 257 { 258 Authctxt *authctxt = ctxt; 259 Gssctxt *gssctxt; 260 int authenticated = 0; 261 Buffer b; 262 gss_buffer_desc mic, gssbuf; 263 u_int len; 264 265 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 266 fatal("No authentication or GSSAPI context"); 267 268 gssctxt = authctxt->methoddata; 269 270 mic.value = packet_get_string(&len); 271 mic.length = len; 272 273 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 274 "gssapi-with-mic"); 275 276 gssbuf.value = buffer_ptr(&b); 277 gssbuf.length = buffer_len(&b); 278 279 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 280 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 281 else 282 logit("GSSAPI MIC check failed"); 283 284 buffer_free(&b); 285 xfree(mic.value); 286 287 authctxt->postponed = 0; 288 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 289 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 290 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 291 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 292 userauth_finish(authctxt, authenticated, "gssapi-with-mic"); 293 } 294 295 Authmethod method_gssapi = { 296 "gssapi-with-mic", 297 userauth_gssapi, 298 &options.gss_authentication 299 }; 300 301 #endif /* GSSAPI */ 302