1 /* 2 * Copyright (c) 2000 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 25 #include "includes.h" 26 RCSID("$OpenBSD: auth2.c,v 1.107 2004/07/28 09:40:29 markus Exp $"); 27 RCSID("$FreeBSD$"); 28 29 #include "canohost.h" 30 #include "ssh2.h" 31 #include "xmalloc.h" 32 #include "packet.h" 33 #include "log.h" 34 #include "servconf.h" 35 #include "compat.h" 36 #include "auth.h" 37 #include "dispatch.h" 38 #include "pathnames.h" 39 #include "monitor_wrap.h" 40 #include "buffer.h" 41 42 #ifdef GSSAPI 43 #include "ssh-gss.h" 44 #endif 45 46 /* import */ 47 extern ServerOptions options; 48 extern u_char *session_id2; 49 extern u_int session_id2_len; 50 extern Buffer loginmsg; 51 52 /* methods */ 53 54 extern Authmethod method_none; 55 extern Authmethod method_pubkey; 56 extern Authmethod method_passwd; 57 extern Authmethod method_kbdint; 58 extern Authmethod method_hostbased; 59 #ifdef GSSAPI 60 extern Authmethod method_gssapi; 61 #endif 62 63 Authmethod *authmethods[] = { 64 &method_none, 65 &method_pubkey, 66 #ifdef GSSAPI 67 &method_gssapi, 68 #endif 69 &method_passwd, 70 &method_kbdint, 71 &method_hostbased, 72 NULL 73 }; 74 75 /* protocol */ 76 77 static void input_service_request(int, u_int32_t, void *); 78 static void input_userauth_request(int, u_int32_t, void *); 79 80 /* helper */ 81 static Authmethod *authmethod_lookup(const char *); 82 static char *authmethods_get(void); 83 int user_key_allowed(struct passwd *, Key *); 84 85 /* 86 * loop until authctxt->success == TRUE 87 */ 88 89 void 90 do_authentication2(Authctxt *authctxt) 91 { 92 /* challenge-response is implemented via keyboard interactive */ 93 if (options.challenge_response_authentication) 94 options.kbd_interactive_authentication = 1; 95 96 dispatch_init(&dispatch_protocol_error); 97 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 98 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 99 } 100 101 static void 102 input_service_request(int type, u_int32_t seq, void *ctxt) 103 { 104 Authctxt *authctxt = ctxt; 105 u_int len; 106 int acceptit = 0; 107 char *service = packet_get_string(&len); 108 packet_check_eom(); 109 110 if (authctxt == NULL) 111 fatal("input_service_request: no authctxt"); 112 113 if (strcmp(service, "ssh-userauth") == 0) { 114 if (!authctxt->success) { 115 acceptit = 1; 116 /* now we can handle user-auth requests */ 117 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 118 } 119 } 120 /* XXX all other service requests are denied */ 121 122 if (acceptit) { 123 packet_start(SSH2_MSG_SERVICE_ACCEPT); 124 packet_put_cstring(service); 125 packet_send(); 126 packet_write_wait(); 127 } else { 128 debug("bad service request %s", service); 129 packet_disconnect("bad service request %s", service); 130 } 131 xfree(service); 132 } 133 134 static void 135 input_userauth_request(int type, u_int32_t seq, void *ctxt) 136 { 137 Authctxt *authctxt = ctxt; 138 Authmethod *m = NULL; 139 char *user, *service, *method, *style = NULL; 140 int authenticated = 0; 141 #ifdef HAVE_LOGIN_CAP 142 login_cap_t *lc; 143 const char *from_host, *from_ip; 144 145 from_host = get_canonical_hostname(options.use_dns); 146 from_ip = get_remote_ipaddr(); 147 #endif 148 149 if (authctxt == NULL) 150 fatal("input_userauth_request: no authctxt"); 151 152 user = packet_get_string(NULL); 153 service = packet_get_string(NULL); 154 method = packet_get_string(NULL); 155 debug("userauth-request for user %s service %s method %s", user, service, method); 156 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 157 158 if ((style = strchr(user, ':')) != NULL) 159 *style++ = 0; 160 161 if (authctxt->attempt++ == 0) { 162 /* setup auth context */ 163 authctxt->pw = PRIVSEP(getpwnamallow(user)); 164 authctxt->user = xstrdup(user); 165 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 166 authctxt->valid = 1; 167 debug2("input_userauth_request: setting up authctxt for %s", user); 168 #ifdef USE_PAM 169 if (options.use_pam) 170 PRIVSEP(start_pam(authctxt)); 171 #endif 172 } else { 173 logit("input_userauth_request: invalid user %s", user); 174 authctxt->pw = fakepw(); 175 #ifdef USE_PAM 176 if (options.use_pam) 177 PRIVSEP(start_pam(authctxt)); 178 #endif 179 #ifdef SSH_AUDIT_EVENTS 180 PRIVSEP(audit_event(SSH_INVALID_USER)); 181 #endif 182 } 183 setproctitle("%s%s", authctxt->valid ? user : "unknown", 184 use_privsep ? " [net]" : ""); 185 authctxt->service = xstrdup(service); 186 authctxt->style = style ? xstrdup(style) : NULL; 187 if (use_privsep) 188 mm_inform_authserv(service, style); 189 } else if (strcmp(user, authctxt->user) != 0 || 190 strcmp(service, authctxt->service) != 0) { 191 packet_disconnect("Change of username or service not allowed: " 192 "(%s,%s) -> (%s,%s)", 193 authctxt->user, authctxt->service, user, service); 194 } 195 196 #ifdef HAVE_LOGIN_CAP 197 if (authctxt->pw != NULL) { 198 lc = login_getpwclass(authctxt->pw); 199 if (lc == NULL) 200 lc = login_getclassbyname(NULL, authctxt->pw); 201 if (!auth_hostok(lc, from_host, from_ip)) { 202 logit("Denied connection for %.200s from %.200s [%.200s].", 203 authctxt->pw->pw_name, from_host, from_ip); 204 packet_disconnect("Sorry, you are not allowed to connect."); 205 } 206 if (!auth_timeok(lc, time(NULL))) { 207 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 208 authctxt->pw->pw_name, from_host); 209 packet_disconnect("Logins not available right now."); 210 } 211 login_close(lc); 212 lc = NULL; 213 } 214 #endif /* HAVE_LOGIN_CAP */ 215 216 /* reset state */ 217 auth2_challenge_stop(authctxt); 218 219 #ifdef GSSAPI 220 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 221 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 222 #endif 223 224 authctxt->postponed = 0; 225 226 /* try to authenticate user */ 227 m = authmethod_lookup(method); 228 if (m != NULL) { 229 debug2("input_userauth_request: try method %s", method); 230 authenticated = m->userauth(authctxt); 231 } 232 userauth_finish(authctxt, authenticated, method); 233 234 xfree(service); 235 xfree(user); 236 xfree(method); 237 } 238 239 void 240 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 241 { 242 char *methods; 243 244 if (!authctxt->valid && authenticated) 245 fatal("INTERNAL ERROR: authenticated invalid user %s", 246 authctxt->user); 247 248 /* Special handling for root */ 249 if (authenticated && authctxt->pw->pw_uid == 0 && 250 !auth_root_allowed(method)) { 251 authenticated = 0; 252 #ifdef SSH_AUDIT_EVENTS 253 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED)); 254 #endif 255 } 256 257 #ifdef USE_PAM 258 if (options.use_pam && authenticated) { 259 if (!PRIVSEP(do_pam_account())) { 260 /* if PAM returned a message, send it to the user */ 261 if (buffer_len(&loginmsg) > 0) { 262 buffer_append(&loginmsg, "\0", 1); 263 userauth_send_banner(buffer_ptr(&loginmsg)); 264 packet_write_wait(); 265 } 266 fatal("Access denied for user %s by PAM account " 267 "configuration", authctxt->user); 268 } 269 } 270 #endif 271 272 #ifdef _UNICOS 273 if (authenticated && cray_access_denied(authctxt->user)) { 274 authenticated = 0; 275 fatal("Access denied for user %s.",authctxt->user); 276 } 277 #endif /* _UNICOS */ 278 279 /* Log before sending the reply */ 280 auth_log(authctxt, authenticated, method, " ssh2"); 281 282 if (authctxt->postponed) 283 return; 284 285 /* XXX todo: check if multiple auth methods are needed */ 286 if (authenticated == 1) { 287 /* turn off userauth */ 288 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 289 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 290 packet_send(); 291 packet_write_wait(); 292 /* now we can break out */ 293 authctxt->success = 1; 294 } else { 295 if (authctxt->failures++ > options.max_authtries) { 296 #ifdef SSH_AUDIT_EVENTS 297 PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES)); 298 #endif 299 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 300 } 301 methods = authmethods_get(); 302 packet_start(SSH2_MSG_USERAUTH_FAILURE); 303 packet_put_cstring(methods); 304 packet_put_char(0); /* XXX partial success, unused */ 305 packet_send(); 306 packet_write_wait(); 307 xfree(methods); 308 } 309 } 310 311 #define DELIM "," 312 313 static char * 314 authmethods_get(void) 315 { 316 Buffer b; 317 char *list; 318 int i; 319 320 buffer_init(&b); 321 for (i = 0; authmethods[i] != NULL; i++) { 322 if (strcmp(authmethods[i]->name, "none") == 0) 323 continue; 324 if (authmethods[i]->enabled != NULL && 325 *(authmethods[i]->enabled) != 0) { 326 if (buffer_len(&b) > 0) 327 buffer_append(&b, ",", 1); 328 buffer_append(&b, authmethods[i]->name, 329 strlen(authmethods[i]->name)); 330 } 331 } 332 buffer_append(&b, "\0", 1); 333 list = xstrdup(buffer_ptr(&b)); 334 buffer_free(&b); 335 return list; 336 } 337 338 static Authmethod * 339 authmethod_lookup(const char *name) 340 { 341 int i; 342 343 if (name != NULL) 344 for (i = 0; authmethods[i] != NULL; i++) 345 if (authmethods[i]->enabled != NULL && 346 *(authmethods[i]->enabled) != 0 && 347 strcmp(name, authmethods[i]->name) == 0) 348 return authmethods[i]; 349 debug2("Unrecognized authentication method name: %s", 350 name ? name : "NULL"); 351 return NULL; 352 } 353