1 /* $OpenBSD: auth2.c,v 1.123 2011/03/10 02:52:57 djm Exp $ */ 2 /* 3 * Copyright (c) 2000 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include "includes.h" 27 28 #include <sys/types.h> 29 #include <sys/stat.h> 30 #include <sys/uio.h> 31 32 #include <fcntl.h> 33 #include <pwd.h> 34 #include <stdarg.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "atomicio.h" 39 #include "xmalloc.h" 40 #include "ssh2.h" 41 #include "packet.h" 42 #include "log.h" 43 #include "buffer.h" 44 #include "servconf.h" 45 #include "compat.h" 46 #include "key.h" 47 #include "hostfile.h" 48 #include "auth.h" 49 #include "dispatch.h" 50 #include "pathnames.h" 51 #include "buffer.h" 52 53 #ifdef GSSAPI 54 #include "ssh-gss.h" 55 #endif 56 #include "monitor_wrap.h" 57 58 /* import */ 59 extern ServerOptions options; 60 extern u_char *session_id2; 61 extern u_int session_id2_len; 62 extern Buffer loginmsg; 63 64 /* methods */ 65 66 extern Authmethod method_none; 67 extern Authmethod method_pubkey; 68 extern Authmethod method_passwd; 69 extern Authmethod method_kbdint; 70 extern Authmethod method_hostbased; 71 #ifdef GSSAPI 72 extern Authmethod method_gssapi; 73 #endif 74 #ifdef JPAKE 75 extern Authmethod method_jpake; 76 #endif 77 78 Authmethod *authmethods[] = { 79 &method_none, 80 &method_pubkey, 81 #ifdef GSSAPI 82 &method_gssapi, 83 #endif 84 #ifdef JPAKE 85 &method_jpake, 86 #endif 87 &method_passwd, 88 &method_kbdint, 89 &method_hostbased, 90 NULL 91 }; 92 93 /* protocol */ 94 95 static void input_service_request(int, u_int32_t, void *); 96 static void input_userauth_request(int, u_int32_t, void *); 97 98 /* helper */ 99 static Authmethod *authmethod_lookup(const char *); 100 static char *authmethods_get(void); 101 102 char * 103 auth2_read_banner(void) 104 { 105 struct stat st; 106 char *banner = NULL; 107 size_t len, n; 108 int fd; 109 110 if ((fd = open(options.banner, O_RDONLY)) == -1) 111 return (NULL); 112 if (fstat(fd, &st) == -1) { 113 close(fd); 114 return (NULL); 115 } 116 if (st.st_size > 1*1024*1024) { 117 close(fd); 118 return (NULL); 119 } 120 121 len = (size_t)st.st_size; /* truncate */ 122 banner = xmalloc(len + 1); 123 n = atomicio(read, fd, banner, len); 124 close(fd); 125 126 if (n != len) { 127 xfree(banner); 128 return (NULL); 129 } 130 banner[n] = '\0'; 131 132 return (banner); 133 } 134 135 void 136 userauth_send_banner(const char *msg) 137 { 138 if (datafellows & SSH_BUG_BANNER) 139 return; 140 141 packet_start(SSH2_MSG_USERAUTH_BANNER); 142 packet_put_cstring(msg); 143 packet_put_cstring(""); /* language, unused */ 144 packet_send(); 145 debug("%s: sent", __func__); 146 } 147 148 static void 149 userauth_banner(void) 150 { 151 char *banner = NULL; 152 153 if (options.banner == NULL || 154 strcasecmp(options.banner, "none") == 0 || 155 (datafellows & SSH_BUG_BANNER) != 0) 156 return; 157 158 if ((banner = PRIVSEP(auth2_read_banner())) == NULL) 159 goto done; 160 userauth_send_banner(banner); 161 162 done: 163 if (banner) 164 xfree(banner); 165 } 166 167 /* 168 * loop until authctxt->success == TRUE 169 */ 170 void 171 do_authentication2(Authctxt *authctxt) 172 { 173 dispatch_init(&dispatch_protocol_error); 174 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 175 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 176 } 177 178 /*ARGSUSED*/ 179 static void 180 input_service_request(int type, u_int32_t seq, void *ctxt) 181 { 182 Authctxt *authctxt = ctxt; 183 u_int len; 184 int acceptit = 0; 185 char *service = packet_get_cstring(&len); 186 packet_check_eom(); 187 188 if (authctxt == NULL) 189 fatal("input_service_request: no authctxt"); 190 191 if (strcmp(service, "ssh-userauth") == 0) { 192 if (!authctxt->success) { 193 acceptit = 1; 194 /* now we can handle user-auth requests */ 195 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 196 } 197 } 198 /* XXX all other service requests are denied */ 199 200 if (acceptit) { 201 packet_start(SSH2_MSG_SERVICE_ACCEPT); 202 packet_put_cstring(service); 203 packet_send(); 204 packet_write_wait(); 205 } else { 206 debug("bad service request %s", service); 207 packet_disconnect("bad service request %s", service); 208 } 209 xfree(service); 210 } 211 212 /*ARGSUSED*/ 213 static void 214 input_userauth_request(int type, u_int32_t seq, void *ctxt) 215 { 216 Authctxt *authctxt = ctxt; 217 Authmethod *m = NULL; 218 char *user, *service, *method, *style = NULL; 219 int authenticated = 0; 220 221 if (authctxt == NULL) 222 fatal("input_userauth_request: no authctxt"); 223 224 user = packet_get_cstring(NULL); 225 service = packet_get_cstring(NULL); 226 method = packet_get_cstring(NULL); 227 debug("userauth-request for user %s service %s method %s", user, service, method); 228 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 229 230 if ((style = strchr(user, ':')) != NULL) 231 *style++ = 0; 232 233 if (authctxt->attempt++ == 0) { 234 /* setup auth context */ 235 authctxt->pw = PRIVSEP(getpwnamallow(user)); 236 authctxt->user = xstrdup(user); 237 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 238 authctxt->valid = 1; 239 debug2("input_userauth_request: setting up authctxt for %s", user); 240 } else { 241 logit("input_userauth_request: invalid user %s", user); 242 authctxt->pw = fakepw(); 243 #ifdef SSH_AUDIT_EVENTS 244 PRIVSEP(audit_event(SSH_INVALID_USER)); 245 #endif 246 } 247 #ifdef USE_PAM 248 if (options.use_pam) 249 PRIVSEP(start_pam(authctxt)); 250 #endif 251 setproctitle("%s%s", authctxt->valid ? user : "unknown", 252 use_privsep ? " [net]" : ""); 253 authctxt->service = xstrdup(service); 254 authctxt->style = style ? xstrdup(style) : NULL; 255 if (use_privsep) 256 mm_inform_authserv(service, style); 257 userauth_banner(); 258 } else if (strcmp(user, authctxt->user) != 0 || 259 strcmp(service, authctxt->service) != 0) { 260 packet_disconnect("Change of username or service not allowed: " 261 "(%s,%s) -> (%s,%s)", 262 authctxt->user, authctxt->service, user, service); 263 } 264 /* reset state */ 265 auth2_challenge_stop(authctxt); 266 #ifdef JPAKE 267 auth2_jpake_stop(authctxt); 268 #endif 269 270 #ifdef GSSAPI 271 /* XXX move to auth2_gssapi_stop() */ 272 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 273 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 274 #endif 275 276 authctxt->postponed = 0; 277 authctxt->server_caused_failure = 0; 278 279 /* try to authenticate user */ 280 m = authmethod_lookup(method); 281 if (m != NULL && authctxt->failures < options.max_authtries) { 282 debug2("input_userauth_request: try method %s", method); 283 authenticated = m->userauth(authctxt); 284 } 285 userauth_finish(authctxt, authenticated, method); 286 287 xfree(service); 288 xfree(user); 289 xfree(method); 290 } 291 292 void 293 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 294 { 295 char *methods; 296 297 if (!authctxt->valid && authenticated) 298 fatal("INTERNAL ERROR: authenticated invalid user %s", 299 authctxt->user); 300 301 /* Special handling for root */ 302 if (authenticated && authctxt->pw->pw_uid == 0 && 303 !auth_root_allowed(method)) { 304 authenticated = 0; 305 #ifdef SSH_AUDIT_EVENTS 306 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 307 #endif 308 } 309 310 #ifdef USE_PAM 311 if (options.use_pam && authenticated) { 312 if (!PRIVSEP(do_pam_account())) { 313 /* if PAM returned a message, send it to the user */ 314 if (buffer_len(&loginmsg) > 0) { 315 buffer_append(&loginmsg, "\0", 1); 316 userauth_send_banner(buffer_ptr(&loginmsg)); 317 packet_write_wait(); 318 } 319 fatal("Access denied for user %s by PAM account " 320 "configuration", authctxt->user); 321 } 322 } 323 #endif 324 325 #ifdef _UNICOS 326 if (authenticated && cray_access_denied(authctxt->user)) { 327 authenticated = 0; 328 fatal("Access denied for user %s.",authctxt->user); 329 } 330 #endif /* _UNICOS */ 331 332 /* Log before sending the reply */ 333 auth_log(authctxt, authenticated, method, " ssh2"); 334 335 if (authctxt->postponed) 336 return; 337 338 /* XXX todo: check if multiple auth methods are needed */ 339 if (authenticated == 1) { 340 /* turn off userauth */ 341 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 342 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 343 packet_send(); 344 packet_write_wait(); 345 /* now we can break out */ 346 authctxt->success = 1; 347 } else { 348 349 /* Allow initial try of "none" auth without failure penalty */ 350 if (!authctxt->server_caused_failure && 351 (authctxt->attempt > 1 || strcmp(method, "none") != 0)) 352 authctxt->failures++; 353 if (authctxt->failures >= options.max_authtries) { 354 #ifdef SSH_AUDIT_EVENTS 355 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); 356 #endif 357 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 358 } 359 methods = authmethods_get(); 360 packet_start(SSH2_MSG_USERAUTH_FAILURE); 361 packet_put_cstring(methods); 362 packet_put_char(0); /* XXX partial success, unused */ 363 packet_send(); 364 packet_write_wait(); 365 xfree(methods); 366 } 367 } 368 369 static char * 370 authmethods_get(void) 371 { 372 Buffer b; 373 char *list; 374 int i; 375 376 buffer_init(&b); 377 for (i = 0; authmethods[i] != NULL; i++) { 378 if (strcmp(authmethods[i]->name, "none") == 0) 379 continue; 380 if (authmethods[i]->enabled != NULL && 381 *(authmethods[i]->enabled) != 0) { 382 if (buffer_len(&b) > 0) 383 buffer_append(&b, ",", 1); 384 buffer_append(&b, authmethods[i]->name, 385 strlen(authmethods[i]->name)); 386 } 387 } 388 buffer_append(&b, "\0", 1); 389 list = xstrdup(buffer_ptr(&b)); 390 buffer_free(&b); 391 return list; 392 } 393 394 static Authmethod * 395 authmethod_lookup(const char *name) 396 { 397 int i; 398 399 if (name != NULL) 400 for (i = 0; authmethods[i] != NULL; i++) 401 if (authmethods[i]->enabled != NULL && 402 *(authmethods[i]->enabled) != 0 && 403 strcmp(name, authmethods[i]->name) == 0) 404 return authmethods[i]; 405 debug2("Unrecognized authentication method name: %s", 406 name ? name : "NULL"); 407 return NULL; 408 } 409 410
