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 1.104 2003/11/04 08:54:09 djm 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 41 #ifdef GSSAPI 42 #include "ssh-gss.h" 43 #endif 44 45 /* import */ 46 extern ServerOptions options; 47 extern u_char *session_id2; 48 extern u_int session_id2_len; 49 50 /* methods */ 51 52 extern Authmethod method_none; 53 extern Authmethod method_pubkey; 54 extern Authmethod method_passwd; 55 extern Authmethod method_kbdint; 56 extern Authmethod method_hostbased; 57 #ifdef GSSAPI 58 extern Authmethod method_gssapi; 59 #endif 60 61 Authmethod *authmethods[] = { 62 &method_none, 63 &method_pubkey, 64 #ifdef GSSAPI 65 &method_gssapi, 66 #endif 67 &method_passwd, 68 &method_kbdint, 69 &method_hostbased, 70 NULL 71 }; 72 73 /* protocol */ 74 75 static void input_service_request(int, u_int32_t, void *); 76 static void input_userauth_request(int, u_int32_t, void *); 77 78 /* helper */ 79 static Authmethod *authmethod_lookup(const char *); 80 static char *authmethods_get(void); 81 int user_key_allowed(struct passwd *, Key *); 82 83 /* 84 * loop until authctxt->success == TRUE 85 */ 86 87 void 88 do_authentication2(Authctxt *authctxt) 89 { 90 /* challenge-response is implemented via keyboard interactive */ 91 if (options.challenge_response_authentication) 92 options.kbd_interactive_authentication = 1; 93 94 dispatch_init(&dispatch_protocol_error); 95 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 96 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 97 } 98 99 static void 100 input_service_request(int type, u_int32_t seq, void *ctxt) 101 { 102 Authctxt *authctxt = ctxt; 103 u_int len; 104 int acceptit = 0; 105 char *service = packet_get_string(&len); 106 packet_check_eom(); 107 108 if (authctxt == NULL) 109 fatal("input_service_request: no authctxt"); 110 111 if (strcmp(service, "ssh-userauth") == 0) { 112 if (!authctxt->success) { 113 acceptit = 1; 114 /* now we can handle user-auth requests */ 115 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 116 } 117 } 118 /* XXX all other service requests are denied */ 119 120 if (acceptit) { 121 packet_start(SSH2_MSG_SERVICE_ACCEPT); 122 packet_put_cstring(service); 123 packet_send(); 124 packet_write_wait(); 125 } else { 126 debug("bad service request %s", service); 127 packet_disconnect("bad service request %s", service); 128 } 129 xfree(service); 130 } 131 132 static void 133 input_userauth_request(int type, u_int32_t seq, void *ctxt) 134 { 135 Authctxt *authctxt = ctxt; 136 Authmethod *m = NULL; 137 char *user, *service, *method, *style = NULL; 138 int authenticated = 0; 139 #ifdef HAVE_LOGIN_CAP 140 login_cap_t *lc; 141 const char *from_host, *from_ip; 142 143 from_host = get_canonical_hostname(options.use_dns); 144 from_ip = get_remote_ipaddr(); 145 #endif 146 147 if (authctxt == NULL) 148 fatal("input_userauth_request: no authctxt"); 149 150 user = packet_get_string(NULL); 151 service = packet_get_string(NULL); 152 method = packet_get_string(NULL); 153 debug("userauth-request for user %s service %s method %s", user, service, method); 154 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 155 156 if ((style = strchr(user, ':')) != NULL) 157 *style++ = 0; 158 159 if (authctxt->attempt++ == 0) { 160 /* setup auth context */ 161 authctxt->pw = PRIVSEP(getpwnamallow(user)); 162 authctxt->user = xstrdup(user); 163 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 164 authctxt->valid = 1; 165 debug2("input_userauth_request: setting up authctxt for %s", user); 166 #ifdef USE_PAM 167 if (options.use_pam) 168 PRIVSEP(start_pam(authctxt)); 169 #endif 170 } else { 171 logit("input_userauth_request: illegal user %s", user); 172 authctxt->pw = fakepw(); 173 #ifdef USE_PAM 174 if (options.use_pam) 175 PRIVSEP(start_pam(authctxt)); 176 #endif 177 } 178 setproctitle("%s%s", authctxt->pw ? user : "unknown", 179 use_privsep ? " [net]" : ""); 180 authctxt->service = xstrdup(service); 181 authctxt->style = style ? xstrdup(style) : NULL; 182 if (use_privsep) 183 mm_inform_authserv(service, style); 184 } else if (strcmp(user, authctxt->user) != 0 || 185 strcmp(service, authctxt->service) != 0) { 186 packet_disconnect("Change of username or service not allowed: " 187 "(%s,%s) -> (%s,%s)", 188 authctxt->user, authctxt->service, user, service); 189 } 190 191 #ifdef HAVE_LOGIN_CAP 192 if (authctxt->pw != NULL) { 193 lc = login_getpwclass(authctxt->pw); 194 if (lc == NULL) 195 lc = login_getclassbyname(NULL, authctxt->pw); 196 if (!auth_hostok(lc, from_host, from_ip)) { 197 logit("Denied connection for %.200s from %.200s [%.200s].", 198 authctxt->pw->pw_name, from_host, from_ip); 199 packet_disconnect("Sorry, you are not allowed to connect."); 200 } 201 if (!auth_timeok(lc, time(NULL))) { 202 logit("LOGIN %.200s REFUSED (TIME) FROM %.200s", 203 authctxt->pw->pw_name, from_host); 204 packet_disconnect("Logins not available right now."); 205 } 206 login_close(lc); 207 lc = NULL; 208 } 209 #endif /* HAVE_LOGIN_CAP */ 210 211 /* reset state */ 212 auth2_challenge_stop(authctxt); 213 214 #ifdef GSSAPI 215 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL); 216 dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL); 217 #endif 218 219 authctxt->postponed = 0; 220 221 /* try to authenticate user */ 222 m = authmethod_lookup(method); 223 if (m != NULL) { 224 debug2("input_userauth_request: try method %s", method); 225 authenticated = m->userauth(authctxt); 226 } 227 userauth_finish(authctxt, authenticated, method); 228 229 xfree(service); 230 xfree(user); 231 xfree(method); 232 } 233 234 void 235 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 236 { 237 char *methods; 238 239 if (!authctxt->valid && authenticated) 240 fatal("INTERNAL ERROR: authenticated invalid user %s", 241 authctxt->user); 242 243 /* Special handling for root */ 244 if (authenticated && authctxt->pw->pw_uid == 0 && 245 !auth_root_allowed(method)) 246 authenticated = 0; 247 248 #ifdef USE_PAM 249 if (options.use_pam && authenticated && !PRIVSEP(do_pam_account())) 250 authenticated = 0; 251 #endif 252 253 #ifdef _UNICOS 254 if (authenticated && cray_access_denied(authctxt->user)) { 255 authenticated = 0; 256 fatal("Access denied for user %s.",authctxt->user); 257 } 258 #endif /* _UNICOS */ 259 260 /* Log before sending the reply */ 261 auth_log(authctxt, authenticated, method, " ssh2"); 262 263 if (authctxt->postponed) 264 return; 265 266 /* XXX todo: check if multiple auth methods are needed */ 267 if (authenticated == 1) { 268 /* turn off userauth */ 269 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 270 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 271 packet_send(); 272 packet_write_wait(); 273 /* now we can break out */ 274 authctxt->success = 1; 275 } else { 276 if (authctxt->failures++ > AUTH_FAIL_MAX) 277 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 278 methods = authmethods_get(); 279 packet_start(SSH2_MSG_USERAUTH_FAILURE); 280 packet_put_cstring(methods); 281 packet_put_char(0); /* XXX partial success, unused */ 282 packet_send(); 283 packet_write_wait(); 284 xfree(methods); 285 } 286 } 287 288 #define DELIM "," 289 290 static char * 291 authmethods_get(void) 292 { 293 Buffer b; 294 char *list; 295 int i; 296 297 buffer_init(&b); 298 for (i = 0; authmethods[i] != NULL; i++) { 299 if (strcmp(authmethods[i]->name, "none") == 0) 300 continue; 301 if (authmethods[i]->enabled != NULL && 302 *(authmethods[i]->enabled) != 0) { 303 if (buffer_len(&b) > 0) 304 buffer_append(&b, ",", 1); 305 buffer_append(&b, authmethods[i]->name, 306 strlen(authmethods[i]->name)); 307 } 308 } 309 buffer_append(&b, "\0", 1); 310 list = xstrdup(buffer_ptr(&b)); 311 buffer_free(&b); 312 return list; 313 } 314 315 static Authmethod * 316 authmethod_lookup(const char *name) 317 { 318 int i; 319 320 if (name != NULL) 321 for (i = 0; authmethods[i] != NULL; i++) 322 if (authmethods[i]->enabled != NULL && 323 *(authmethods[i]->enabled) != 0 && 324 strcmp(name, authmethods[i]->name) == 0) 325 return authmethods[i]; 326 debug2("Unrecognized authentication method name: %s", 327 name ? name : "NULL"); 328 return NULL; 329 } 330