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 1.99 2003/06/24 08:23:46 markus Exp $"); 27 28 #include "ssh2.h" 29 #include "xmalloc.h" 30 #include "packet.h" 31 #include "log.h" 32 #include "servconf.h" 33 #include "compat.h" 34 #include "auth.h" 35 #include "dispatch.h" 36 #include "pathnames.h" 37 #include "monitor_wrap.h" 38 39 /* import */ 40 extern ServerOptions options; 41 extern u_char *session_id2; 42 extern u_int session_id2_len; 43 44 Authctxt *x_authctxt = NULL; 45 46 /* methods */ 47 48 extern Authmethod method_none; 49 extern Authmethod method_pubkey; 50 extern Authmethod method_passwd; 51 extern Authmethod method_kbdint; 52 extern Authmethod method_hostbased; 53 #ifdef KRB5 54 extern Authmethod method_kerberos; 55 #endif 56 57 Authmethod *authmethods[] = { 58 &method_none, 59 &method_pubkey, 60 &method_passwd, 61 &method_kbdint, 62 &method_hostbased, 63 #ifdef KRB5 64 &method_kerberos, 65 #endif 66 NULL 67 }; 68 69 /* protocol */ 70 71 static void input_service_request(int, u_int32_t, void *); 72 static void input_userauth_request(int, u_int32_t, void *); 73 74 /* helper */ 75 static Authmethod *authmethod_lookup(const char *); 76 static char *authmethods_get(void); 77 int user_key_allowed(struct passwd *, Key *); 78 int hostbased_key_allowed(struct passwd *, const char *, char *, Key *); 79 80 /* 81 * loop until authctxt->success == TRUE 82 */ 83 84 Authctxt * 85 do_authentication2(void) 86 { 87 Authctxt *authctxt = authctxt_new(); 88 89 x_authctxt = authctxt; /*XXX*/ 90 91 /* challenge-response is implemented via keyboard interactive */ 92 if (options.challenge_response_authentication) 93 options.kbd_interactive_authentication = 1; 94 95 dispatch_init(&dispatch_protocol_error); 96 dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request); 97 dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt); 98 99 return (authctxt); 100 } 101 102 static void 103 input_service_request(int type, u_int32_t seq, void *ctxt) 104 { 105 Authctxt *authctxt = ctxt; 106 u_int len; 107 int acceptit = 0; 108 char *service = packet_get_string(&len); 109 packet_check_eom(); 110 111 if (authctxt == NULL) 112 fatal("input_service_request: no authctxt"); 113 114 if (strcmp(service, "ssh-userauth") == 0) { 115 if (!authctxt->success) { 116 acceptit = 1; 117 /* now we can handle user-auth requests */ 118 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request); 119 } 120 } 121 /* XXX all other service requests are denied */ 122 123 if (acceptit) { 124 packet_start(SSH2_MSG_SERVICE_ACCEPT); 125 packet_put_cstring(service); 126 packet_send(); 127 packet_write_wait(); 128 } else { 129 debug("bad service request %s", service); 130 packet_disconnect("bad service request %s", service); 131 } 132 xfree(service); 133 } 134 135 static void 136 input_userauth_request(int type, u_int32_t seq, void *ctxt) 137 { 138 Authctxt *authctxt = ctxt; 139 Authmethod *m = NULL; 140 char *user, *service, *method, *style = NULL; 141 int authenticated = 0; 142 143 if (authctxt == NULL) 144 fatal("input_userauth_request: no authctxt"); 145 146 user = packet_get_string(NULL); 147 service = packet_get_string(NULL); 148 method = packet_get_string(NULL); 149 debug("userauth-request for user %s service %s method %s", user, service, method); 150 debug("attempt %d failures %d", authctxt->attempt, authctxt->failures); 151 152 if ((style = strchr(user, ':')) != NULL) 153 *style++ = 0; 154 155 if (authctxt->attempt++ == 0) { 156 /* setup auth context */ 157 authctxt->pw = PRIVSEP(getpwnamallow(user)); 158 if (authctxt->pw && strcmp(service, "ssh-connection")==0) { 159 authctxt->valid = 1; 160 debug2("input_userauth_request: setting up authctxt for %s", user); 161 } else { 162 logit("input_userauth_request: illegal user %s", user); 163 } 164 setproctitle("%s%s", authctxt->pw ? user : "unknown", 165 use_privsep ? " [net]" : ""); 166 authctxt->user = xstrdup(user); 167 authctxt->service = xstrdup(service); 168 authctxt->style = style ? xstrdup(style) : NULL; 169 if (use_privsep) 170 mm_inform_authserv(service, style); 171 } else if (strcmp(user, authctxt->user) != 0 || 172 strcmp(service, authctxt->service) != 0) { 173 packet_disconnect("Change of username or service not allowed: " 174 "(%s,%s) -> (%s,%s)", 175 authctxt->user, authctxt->service, user, service); 176 } 177 /* reset state */ 178 auth2_challenge_stop(authctxt); 179 authctxt->postponed = 0; 180 181 /* try to authenticate user */ 182 m = authmethod_lookup(method); 183 if (m != NULL) { 184 debug2("input_userauth_request: try method %s", method); 185 authenticated = m->userauth(authctxt); 186 } 187 userauth_finish(authctxt, authenticated, method); 188 189 xfree(service); 190 xfree(user); 191 xfree(method); 192 } 193 194 void 195 userauth_finish(Authctxt *authctxt, int authenticated, char *method) 196 { 197 char *methods; 198 199 if (!authctxt->valid && authenticated) 200 fatal("INTERNAL ERROR: authenticated invalid user %s", 201 authctxt->user); 202 203 /* Special handling for root */ 204 if (authenticated && authctxt->pw->pw_uid == 0 && 205 !auth_root_allowed(method)) 206 authenticated = 0; 207 208 /* Log before sending the reply */ 209 auth_log(authctxt, authenticated, method, " ssh2"); 210 211 if (authctxt->postponed) 212 return; 213 214 /* XXX todo: check if multiple auth methods are needed */ 215 if (authenticated == 1) { 216 /* turn off userauth */ 217 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore); 218 packet_start(SSH2_MSG_USERAUTH_SUCCESS); 219 packet_send(); 220 packet_write_wait(); 221 /* now we can break out */ 222 authctxt->success = 1; 223 } else { 224 if (authctxt->failures++ > AUTH_FAIL_MAX) 225 packet_disconnect(AUTH_FAIL_MSG, authctxt->user); 226 methods = authmethods_get(); 227 packet_start(SSH2_MSG_USERAUTH_FAILURE); 228 packet_put_cstring(methods); 229 packet_put_char(0); /* XXX partial success, unused */ 230 packet_send(); 231 packet_write_wait(); 232 xfree(methods); 233 } 234 } 235 236 /* get current user */ 237 238 struct passwd* 239 auth_get_user(void) 240 { 241 return (x_authctxt != NULL && x_authctxt->valid) ? x_authctxt->pw : NULL; 242 } 243 244 #define DELIM "," 245 246 static char * 247 authmethods_get(void) 248 { 249 Buffer b; 250 char *list; 251 int i; 252 253 buffer_init(&b); 254 for (i = 0; authmethods[i] != NULL; i++) { 255 if (strcmp(authmethods[i]->name, "none") == 0) 256 continue; 257 if (authmethods[i]->enabled != NULL && 258 *(authmethods[i]->enabled) != 0) { 259 if (buffer_len(&b) > 0) 260 buffer_append(&b, ",", 1); 261 buffer_append(&b, authmethods[i]->name, 262 strlen(authmethods[i]->name)); 263 } 264 } 265 buffer_append(&b, "\0", 1); 266 list = xstrdup(buffer_ptr(&b)); 267 buffer_free(&b); 268 return list; 269 } 270 271 static Authmethod * 272 authmethod_lookup(const char *name) 273 { 274 int i; 275 276 if (name != NULL) 277 for (i = 0; authmethods[i] != NULL; i++) 278 if (authmethods[i]->enabled != NULL && 279 *(authmethods[i]->enabled) != 0 && 280 strcmp(name, authmethods[i]->name) == 0) 281 return authmethods[i]; 282 debug2("Unrecognized authentication method name: %s", 283 name ? name : "NULL"); 284 return NULL; 285 } 286