1 /* $OpenBSD: auth2.c,v 1.113 2006/08/03 03:34:41 deraadt 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 __RCSID("$FreeBSD$"); 28 29 #include <sys/types.h> 30 31 #include <pwd.h> 32 #include <stdarg.h> 33 #include <string.h> 34 35 #include "xmalloc.h" 36 #include "ssh2.h" 37 #include "packet.h" 38 #include "log.h" 39 #include "buffer.h" 40 #include "servconf.h" 41 #include "compat.h" 42 #include "key.h" 43 #include "hostfile.h" 44 #include "auth.h" 45 #include "dispatch.h" 46 #include "pathnames.h" 47 #include "buffer.h" 48 #include "canohost.h" 49 50 #ifdef GSSAPI 51 #include "ssh-gss.h" 52 #endif 53 #include "monitor_wrap.h" 54 55 /* import */ 56 extern ServerOptions options; 57 extern u_char *session_id2; 58 extern u_int session_id2_len; 59 extern Buffer loginmsg; 60 61 /* methods */ 62 63 extern Authmethod method_none; 64 extern Authmethod method_pubkey; 65 extern Authmethod method_passwd; 66 extern Authmethod method_kbdint; 67 extern Authmethod method_hostbased; 68 #ifdef GSSAPI 69 extern Authmethod method_gssapi; 70 #endif 71 72 Authmethod *authmethods[] = { 73 &method_none, 74 &method_pubkey, 75 #ifdef GSSAPI 76 &method_gssapi, 77 #endif 78 &method_passwd, 79 &method_kbdint, 80 &method_hostbased, 81 NULL 82 }; 83 84 /* protocol */ 85 86 static void input_service_request(int, u_int32_t, void *); 87 static void input_userauth_request(int, u_int32_t, void *); 88 89 /* helper */ 90 static Authmethod *authmethod_lookup(const char *); 91 static char *authmethods_get(void); 92 int user_key_allowed(struct passwd *, Key *); 93 94 /* 95 * loop until authctxt->success == TRUE 96 */ 97 98 void 99 do_authentication2(Authctxt *authctxt) 100 { 101 /* challenge-response is implemented via keyboard interactive */ 102 if (options.challenge_response_authentication) 103 options.kbd_interactive_authentication = 1; 104 105 dispatch_init(&dispatch_protocol_error); 106 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 107 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 108 } 109 110 /*ARGSUSED*/ 111 static void 112 input_service_request(int type, u_int32_t seq, void *ctxt) 113 { 114 Authctxt *authctxt = ctxt; 115 u_int len; 116 int acceptit = 0; 117 char *service = packet_get_string(&len); 118 packet_check_eom(); 119 120 if (authctxt == NULL) 121 fatal("input_service_request: no authctxt"); 122 123 if (strcmp(service, "ssh-userauth") == 0) { 124 if (!authctxt->success) { 125 acceptit = 1; 126 /* now we can handle user-auth requests */ 127 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 128 } 129 } 130 /* XXX all other service requests are denied */ 131 132 if (acceptit) { 133 packet_start(SSH2_MSG_SERVICE_ACCEPT); 134 packet_put_cstring(service); 135 packet_send(); 136 packet_write_wait(); 137 } else { 138 debug("bad service request %s", service); 139 packet_disconnect("bad service request %s", service); 140 } 141 xfree(service); 142 } 143 144 /*ARGSUSED*/ 145 static void 146 input_userauth_request(int type, u_int32_t seq, void *ctxt) 147 { 148 Authctxt *authctxt = ctxt; 149 Authmethod *m = NULL; 150 char *user, *service, *method, *style = NULL; 151 int authenticated = 0; 152 #ifdef HAVE_LOGIN_CAP 153 login_cap_t *lc; 154 const char *from_host, *from_ip; 155 156 from_host = get_canonical_hostname(options.use_dns); 157 from_ip = get_remote_ipaddr(); 158 #endif 159 160 if (authctxt == NULL) 161 fatal("input_userauth_request: no authctxt"); 162 163 user = packet_get_string(NULL); 164 service = packet_get_string(NULL); 165 method = packet_get_string(NULL); 166 debug("userauth-request for user %s service %s method %s", user, service, method); 167 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 168 169 if ((style = strchr(user, ':')) != NULL) 170 *style++ = 0; 171 172 if (authctxt->attempt++ == 0) { 173 /* setup auth context */ 174 authctxt->pw = PRIVSEP(getpwnamallow(user)); 175 authctxt->user = xstrdup(user); 176 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 177 authctxt->valid = 1; 178 debug2("input_userauth_request: setting up authctxt for %s", user); 179 } else { 180 logit("input_userauth_request: invalid user %s", user); 181 authctxt->pw = fakepw(); 182 #ifdef SSH_AUDIT_EVENTS 183 PRIVSEP(audit_event(SSH_INVALID_USER)); 184 #endif 185 } 186 #ifdef USE_PAM 187 if (options.use_pam) 188 PRIVSEP(start_pam(authctxt)); 189 #endif 190 setproctitle("%s%s", authctxt->valid ? user : "unknown", 191 use_privsep ? " [net]" : ""); 192 authctxt->service = xstrdup(service); 193 authctxt->style = style ? xstrdup(style) : NULL; 194 if (use_privsep) 195 mm_inform_authserv(service, style); 196 } else if (strcmp(user, authctxt->user) != 0 || 197 strcmp(service, authctxt->service) != 0) { 198 packet_disconnect("Change of username or service not allowed: " 199 "(%s,%s) -> (%s,%s)", 200 authctxt->user, authctxt->service, user, service); 201 } 202 203 #ifdef HAVE_LOGIN_CAP 204 if (authctxt->pw != NULL) { 205 lc = login_getpwclass(authctxt->pw); 206 if (lc == NULL) 207 lc = login_getclassbyname(NULL, authctxt->pw); 208 if (!auth_hostok(lc, from_host, from_ip)) { 209 logit("Denied connection for %.200s from %.200s [%.200s].", 210 authctxt->pw->pw_name, from_host, from_ip); 211 packet_disconnect("Sorry, you are not allowed to connect."); 212 } 213 if (!auth_timeok(lc, time(NULL))) { 214 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 215 authctxt->pw->pw_name, from_host); 216 packet_disconnect("Logins not available right now."); 217 } 218 login_close(lc); 219 lc = NULL; 220 } 221 #endif /* HAVE_LOGIN_CAP */ 222 223 /* reset state */ 224 auth2_challenge_stop(authctxt); 225 226 #ifdef GSSAPI 227 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 228 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 229 #endif 230 231 authctxt->postponed = 0; 232 233 /* try to authenticate user */ 234 m = authmethod_lookup(method); 235 if (m != NULL) { 236 debug2("input_userauth_request: try method %s", method); 237 authenticated = m->userauth(authctxt); 238 } 239 userauth_finish(authctxt, authenticated, method); 240 241 xfree(service); 242 xfree(user); 243 xfree(method); 244 } 245 246 void 247 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 248 { 249 char *methods; 250 251 if (!authctxt->valid && authenticated) 252 fatal("INTERNAL ERROR: authenticated invalid user %s", 253 authctxt->user); 254 255 /* Special handling for root */ 256 if (authenticated && authctxt->pw->pw_uid == 0 && 257 !auth_root_allowed(method)) { 258 authenticated = 0; 259 #ifdef SSH_AUDIT_EVENTS 260 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 261 #endif 262 } 263 264 #ifdef USE_PAM 265 if (options.use_pam && authenticated) { 266 if (!PRIVSEP(do_pam_account())) { 267 /* if PAM returned a message, send it to the user */ 268 if (buffer_len(&loginmsg) > 0) { 269 buffer_append(&loginmsg, "\0", 1); 270 userauth_send_banner(buffer_ptr(&loginmsg)); 271 packet_write_wait(); 272 } 273 fatal("Access denied for user %s by PAM account " 274 "configuration", authctxt->user); 275 } 276 } 277 #endif 278 279 #ifdef _UNICOS 280 if (authenticated && cray_access_denied(authctxt->user)) { 281 authenticated = 0; 282 fatal("Access denied for user %s.",authctxt->user); 283 } 284 #endif /* _UNICOS */ 285 286 /* Log before sending the reply */ 287 auth_log(authctxt, authenticated, method, " ssh2"); 288 289 if (authctxt->postponed) 290 return; 291 292 /* XXX todo: check if multiple auth methods are needed */ 293 if (authenticated == 1) { 294 /* turn off userauth */ 295 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 296 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 297 packet_send(); 298 packet_write_wait(); 299 /* now we can break out */ 300 authctxt->success = 1; 301 } else { 302 if (authctxt->failures++ > options.max_authtries) { 303 #ifdef SSH_AUDIT_EVENTS 304 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); 305 #endif 306 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 307 } 308 methods = authmethods_get(); 309 packet_start(SSH2_MSG_USERAUTH_FAILURE); 310 packet_put_cstring(methods); 311 packet_put_char(0); /* XXX partial success, unused */ 312 packet_send(); 313 packet_write_wait(); 314 xfree(methods); 315 } 316 } 317 318 #define DELIM "," 319 320 static char * 321 authmethods_get(void) 322 { 323 Buffer b; 324 char *list; 325 int i; 326 327 buffer_init(&b); 328 for (i = 0; authmethods[i] != NULL; i++) { 329 if (strcmp(authmethods[i]->name, "none") == 0) 330 continue; 331 if (authmethods[i]->enabled != NULL && 332 *(authmethods[i]->enabled) != 0) { 333 if (buffer_len(&b) > 0) 334 buffer_append(&b, ",", 1); 335 buffer_append(&b, authmethods[i]->name, 336 strlen(authmethods[i]->name)); 337 } 338 } 339 buffer_append(&b, "\0", 1); 340 list = xstrdup(buffer_ptr(&b)); 341 buffer_free(&b); 342 return list; 343 } 344 345 static Authmethod * 346 authmethod_lookup(const char *name) 347 { 348 int i; 349 350 if (name != NULL) 351 for (i = 0; authmethods[i] != NULL; i++) 352 if (authmethods[i]->enabled != NULL && 353 *(authmethods[i]->enabled) != 0 && 354 strcmp(name, authmethods[i]->name) == 0) 355 return authmethods[i]; 356 debug2("Unrecognized authentication method name: %s", 357 name ? name : "NULL"); 358 return NULL; 359 } 360