1 /* $OpenBSD: auth2-gss.c,v 1.26 2017/06/24 06:34:38 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 "misc.h" 44 #include "servconf.h" 45 #include "packet.h" 46 #include "ssh-gss.h" 47 #include "monitor_wrap.h" 48 49 extern ServerOptions options; 50 51 static int input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh); 52 static int input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh); 53 static int input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh); 54 static int input_gssapi_errtok(int, u_int32_t, struct ssh *); 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 */ 60 static int 61 userauth_gssapi(struct ssh *ssh) 62 { 63 Authctxt *authctxt = ssh->authctxt; 64 gss_OID_desc goid = {0, NULL}; 65 Gssctxt *ctxt = NULL; 66 int mechs; 67 int present; 68 OM_uint32 ms; 69 u_int len; 70 u_char *doid = NULL; 71 72 if (!authctxt->valid || authctxt->user == NULL) 73 return (0); 74 75 mechs = packet_get_int(); 76 if (mechs == 0) { 77 debug("Mechanism negotiation is not supported"); 78 return (0); 79 } 80 81 do { 82 mechs--; 83 84 free(doid); 85 86 present = 0; 87 doid = packet_get_string(&len); 88 89 if (len > 2 && doid[0] == SSH_GSS_OIDTYPE && 90 doid[1] == len - 2) { 91 goid.elements = doid + 2; 92 goid.length = len - 2; 93 ssh_gssapi_test_oid_supported(&ms, &goid, &present); 94 } else { 95 logit("Badly formed OID received"); 96 } 97 } while (mechs > 0 && !present); 98 99 if (!present) { 100 free(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 free(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 free(doid); 122 123 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, &input_gssapi_token); 124 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, &input_gssapi_errtok); 125 authctxt->postponed = 1; 126 127 return (0); 128 } 129 130 static int 131 input_gssapi_token(int type, u_int32_t plen, struct ssh *ssh) 132 { 133 Authctxt *authctxt = ssh->authctxt; 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 free(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 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 162 userauth_finish(ssh, 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 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 171 if (flags & GSS_C_INTEG_FLAG) 172 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, 173 &input_gssapi_mic); 174 else 175 ssh_dispatch_set(ssh, 176 SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, 177 &input_gssapi_exchange_complete); 178 } 179 } 180 181 gss_release_buffer(&min_status, &send_tok); 182 return 0; 183 } 184 185 static int 186 input_gssapi_errtok(int type, u_int32_t plen, struct ssh *ssh) 187 { 188 Authctxt *authctxt = ssh->authctxt; 189 Gssctxt *gssctxt; 190 gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; 191 gss_buffer_desc recv_tok; 192 OM_uint32 maj_status; 193 u_int len; 194 195 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 196 fatal("No authentication or GSSAPI context"); 197 198 gssctxt = authctxt->methoddata; 199 recv_tok.value = packet_get_string(&len); 200 recv_tok.length = len; 201 202 packet_check_eom(); 203 204 /* Push the error token into GSSAPI to see what it says */ 205 maj_status = PRIVSEP(ssh_gssapi_accept_ctx(gssctxt, &recv_tok, 206 &send_tok, NULL)); 207 208 free(recv_tok.value); 209 210 /* We can't return anything to the client, even if we wanted to */ 211 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 212 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 213 214 /* The client will have already moved on to the next auth */ 215 216 gss_release_buffer(&maj_status, &send_tok); 217 return 0; 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 int 227 input_gssapi_exchange_complete(int type, u_int32_t plen, struct ssh *ssh) 228 { 229 Authctxt *authctxt = ssh->authctxt; 230 int authenticated; 231 const char *displayname; 232 233 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 234 fatal("No authentication or GSSAPI context"); 235 236 /* 237 * We don't need to check the status, because we're only enabled in 238 * the dispatcher once the exchange is complete 239 */ 240 241 packet_check_eom(); 242 243 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 244 245 if ((!use_privsep || mm_is_monitor()) && 246 (displayname = ssh_gssapi_displayname()) != NULL) 247 auth2_record_info(authctxt, "%s", displayname); 248 249 authctxt->postponed = 0; 250 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 251 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 252 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 253 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 254 userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL); 255 return 0; 256 } 257 258 static int 259 input_gssapi_mic(int type, u_int32_t plen, struct ssh *ssh) 260 { 261 Authctxt *authctxt = ssh->authctxt; 262 Gssctxt *gssctxt; 263 int authenticated = 0; 264 Buffer b; 265 gss_buffer_desc mic, gssbuf; 266 u_int len; 267 const char *displayname; 268 269 if (authctxt == NULL || (authctxt->methoddata == NULL && !use_privsep)) 270 fatal("No authentication or GSSAPI context"); 271 272 gssctxt = authctxt->methoddata; 273 274 mic.value = packet_get_string(&len); 275 mic.length = len; 276 277 ssh_gssapi_buildmic(&b, authctxt->user, authctxt->service, 278 "gssapi-with-mic"); 279 280 gssbuf.value = buffer_ptr(&b); 281 gssbuf.length = buffer_len(&b); 282 283 if (!GSS_ERROR(PRIVSEP(ssh_gssapi_checkmic(gssctxt, &gssbuf, &mic)))) 284 authenticated = PRIVSEP(ssh_gssapi_userok(authctxt->user)); 285 else 286 logit("GSSAPI MIC check failed"); 287 288 buffer_free(&b); 289 free(mic.value); 290 291 if ((!use_privsep || mm_is_monitor()) && 292 (displayname = ssh_gssapi_displayname()) != NULL) 293 auth2_record_info(authctxt, "%s", displayname); 294 295 authctxt->postponed = 0; 296 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 297 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_ERRTOK, NULL); 298 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_MIC, NULL); 299 ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 300 userauth_finish(ssh, authenticated, "gssapi-with-mic", NULL); 301 return 0; 302 } 303 304 Authmethod method_gssapi = { 305 "gssapi-with-mic", 306 userauth_gssapi, 307 &options.gss_authentication 308 }; 309 310 #endif /* GSSAPI */ 311