1 /* $OpenBSD: auth2-gss.c,v 1.21 2014/02/26 20:28:44 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 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 int present; 66 OM_uint32 ms; 67 u_int len; 68 u_char *doid = NULL; 69 70 if (!authctxt->valid || authctxt->user == NULL) 71 return (0); 72 73 mechs = packet_get_int(); 74 if (mechs == 0) { 75 debug("Mechanism negotiation is not supported"); 76 return (0); 77 } 78 79 do { 80 mechs--; 81 82 free(doid); 83 84 present = 0; 85 doid = packet_get_string(&len); 86 87 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && 88 doid[1] == len - 2) { 89 goid.elements = doid + 2; 90 goid.length = len - 2; 91 ssh_gssapi_test_oid_supported(&ms, &goid, &present); 92 } else { 93 logit("Badly formed OID received"); 94 } 95 } while (mechs > 0 && !present); 96 97 if (!present) { 98 free(doid); 99 authctxt->server_caused_failure = 1; 100 return (0); 101 } 102 103 if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, &goid)))) { 104 if (ctxt != NULL) 105 ssh_gssapi_delete_ctx(&ctxt); 106 free(doid); 107 authctxt->server_caused_failure = 1; 108 return (0); 109 } 110 111 authctxt->methoddata = (void *)ctxt; 112 113 packet_start(SSH2_MSG_USERAUTH_GSSAPI_RESPONSE); 114 115 /* Return the OID that we received */ 116 packet_put_string(doid, len); 117 118 packet_send(); 119 free(doid); 120 121 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 122 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 123 authctxt->postponed = 1; 124 125 return (0); 126 } 127 128 static void 129 input_gssapi_token(int type, u_int32_t plen, void *ctxt) 130 { 131 Authctxt *authctxt = ctxt; 132 Gssctxt *gssctxt; 133 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 134 gss_buffer_desc recv_tok; 135 OM_uint32 maj_status, min_status, flags; 136 u_int len; 137 138 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 139 fatal("No authentication or GSSAPI context"); 140 141 gssctxt = authctxt->methoddata; 142 recv_tok.value = packet_get_string(&len); 143 recv_tok.length = len; /* u_int vs. size_t */ 144 145 packet_check_eom(); 146 147 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 148 &send_tok, &flags)); 149 150 free(recv_tok.value); 151 152 if (GSS_ERROR(maj_status)) { 153 if (send_tok.length != 0) { 154 packet_start(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK); 155 packet_put_string(send_tok.value, send_tok.length); 156 packet_send(); 157 } 158 authctxt->postponed = 0; 159 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 160 userauth_finish(authctxt, 0, "gssapi-with-mic", NULL); 161 } else { 162 if (send_tok.length != 0) { 163 packet_start(SSH2_MSG_USERAUTH_GSSAPI_TOKEN); 164 packet_put_string(send_tok.value, send_tok.length); 165 packet_send(); 166 } 167 if (maj_status == GSS_S_COMPLETE) { 168 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 169 if (flags & GSS_C_INTEG_FLAG) 170 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, 171 &input_gssapi_mic); 172 else 173 dispatch_set( 174 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 175 &input_gssapi_exchange_complete); 176 } 177 } 178 179 gss_release_buffer(&min_status, &send_tok); 180 } 181 182 static void 183 input_gssapi_errtok(int type, u_int32_t plen, void *ctxt) 184 { 185 Authctxt *authctxt = ctxt; 186 Gssctxt *gssctxt; 187 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 188 gss_buffer_desc recv_tok; 189 OM_uint32 maj_status; 190 u_int len; 191 192 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 193 fatal("No authentication or GSSAPI context"); 194 195 gssctxt = authctxt->methoddata; 196 recv_tok.value = packet_get_string(&len); 197 recv_tok.length = len; 198 199 packet_check_eom(); 200 201 /* Push the error token into GSSAPI to see what it says */ 202 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 203 &send_tok, NULL)); 204 205 free(recv_tok.value); 206 207 /* We can't return anything to the client, even if we wanted to */ 208 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 209 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 210 211 /* The client will have already moved on to the next auth */ 212 213 gss_release_buffer(&maj_status, &send_tok); 214 } 215 216 /* 217 * This is called when the client thinks we've completed authentication. 218 * It should only be enabled in the dispatch handler by the function above, 219 * which only enables it once the GSSAPI exchange is complete. 220 */ 221 222 static void 223 input_gssapi_exchange_complete(int type, u_int32_t plen, void *ctxt) 224 { 225 Authctxt *authctxt = ctxt; 226 int authenticated; 227 228 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 229 fatal("No authentication or GSSAPI context"); 230 231 /* 232 * We don't need to check the status, because we're only enabled in 233 * the dispatcher once the exchange is complete 234 */ 235 236 packet_check_eom(); 237 238 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 239 240 authctxt->postponed = 0; 241 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 242 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 243 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 244 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 245 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 246 } 247 248 static void 249 input_gssapi_mic(int type, u_int32_t plen, void *ctxt) 250 { 251 Authctxt *authctxt = ctxt; 252 Gssctxt *gssctxt; 253 int authenticated = 0; 254 Buffer b; 255 gss_buffer_desc mic, gssbuf; 256 u_int len; 257 258 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 259 fatal("No authentication or GSSAPI context"); 260 261 gssctxt = authctxt->methoddata; 262 263 mic.value = packet_get_string(&len); 264 mic.length = len; 265 266 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 267 "gssapi-with-mic"); 268 269 gssbuf.value = buffer_ptr(&b); 270 gssbuf.length = buffer_len(&b); 271 272 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 273 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 274 else 275 logit("GSSAPI MIC check failed"); 276 277 buffer_free(&b); 278 free(mic.value); 279 280 authctxt->postponed = 0; 281 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 282 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 283 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 284 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 285 userauth_finish(authctxt, authenticated, "gssapi-with-mic", NULL); 286 } 287 288 Authmethod method_gssapi = { 289 "gssapi-with-mic", 290 userauth_gssapi, 291 &options.gss_authentication 292 }; 293 294 #endif /* GSSAPI */ 295