crypto/openssh-5/auth2.c

   1 /* $OpenBSD: auth2.c,v 1.116 2007/09/29 00:25:51 dtucker 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
  30 #include <pwd.h>
  31 #include <stdarg.h>
  32 #include <string.h>
  33
  34 #include "xmalloc.h"
  35 #include "canohost.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
  49 #ifdef GSSAPI
  50 #include "ssh-gss.h"
  51 #endif
  52 #include "monitor_wrap.h"
  53
  54 /* import */
  55 extern ServerOptions options;
  56 extern u_char *session_id2;
  57 extern u_int session_id2_len;
  58 extern Buffer loginmsg;
  59
  60 /* methods */
  61
  62 extern Authmethod method_none;
  63 extern Authmethod method_pubkey;
  64 extern Authmethod method_passwd;
  65 extern Authmethod method_kbdint;
  66 extern Authmethod method_hostbased;
  67 #ifdef GSSAPI
  68 extern Authmethod method_gssapi;
  69 #endif
  70
  71 Authmethod *authmethods[] = {
  72         &method_none,
  73         &method_pubkey,
  74 #ifdef GSSAPI
  75         &method_gssapi,
  76 #endif
  77         &method_passwd,
  78         &method_kbdint,
  79         &method_hostbased,
  80         NULL
  81 };
  82
  83 /* protocol */
  84
  85 static void input_service_request(int, u_int32_t, void *);
  86 static void input_userauth_request(int, u_int32_t, void *);
  87
  88 /* helper */
  89 static Authmethod *authmethod_lookup(const char *);
  90 static char *authmethods_get(void);
  91
  92 /*
  93  * loop until authctxt->success == TRUE
  94  */
  95
  96 void
  97 do_authentication2(Authctxt *authctxt)
  98 {
  99         dispatch_init(&dispatch_protocol_error);
 100         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 101         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 102 }
 103
 104 /*ARGSUSED*/
 105 static void
 106 input_service_request(int type, u_int32_t seq, void *ctxt)
 107 {
 108         Authctxt *authctxt = ctxt;
 109         u_int len;
 110         int acceptit = 0;
 111         char *service = packet_get_string(&len);
 112         packet_check_eom();
 113
 114         if (authctxt == NULL)
 115                 fatal("input_service_request: no authctxt");
 116
 117         if (strcmp(service, "ssh-userauth") == 0) {
 118                 if (!authctxt->success) {
 119                         acceptit = 1;
 120                         /* now we can handle user-auth requests */
 121                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 122                 }
 123         }
 124         /* XXX all other service requests are denied */
 125
 126         if (acceptit) {
 127                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 128                 packet_put_cstring(service);
 129                 packet_send();
 130                 packet_write_wait();
 131         } else {
 132                 debug("bad service request %s", service);
 133                 packet_disconnect("bad service request %s", service);
 134         }
 135         xfree(service);
 136 }
 137
 138 /*ARGSUSED*/
 139 static void
 140 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 141 {
 142         Authctxt *authctxt = ctxt;
 143         Authmethod *m = NULL;
 144         char *user, *service, *method, *style = NULL;
 145         int authenticated = 0;
 146 #ifdef HAVE_LOGIN_CAP
 147         login_cap_t *lc;
 148         const char *from_host, *from_ip;
 149
 150         from_host = get_canonical_hostname(options.use_dns);
 151         from_ip = get_remote_ipaddr();
 152 #endif
 153
 154         if (authctxt == NULL)
 155                 fatal("input_userauth_request: no authctxt");
 156
 157         user = packet_get_string(NULL);
 158         service = packet_get_string(NULL);
 159         method = packet_get_string(NULL);
 160         debug("userauth-request for user %s service %s method %s", user, service, method);
 161         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 162
 163         if ((style = strchr(user, ':')) != NULL)
 164                 *style++ = 0;
 165
 166         if (authctxt->attempt++ == 0) {
 167                 /* setup auth context */
 168                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 169                 authctxt->user = xstrdup(user);
 170                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 171                         authctxt->valid = 1;
 172                         debug2("input_userauth_request: setting up authctxt for %s", user);
 173                 } else {
 174                         logit("input_userauth_request: invalid user %s", user);
 175                         authctxt->pw = fakepw();
 176 #ifdef SSH_AUDIT_EVENTS
 177                         PRIVSEP(audit_event(SSH_INVALID_USER));
 178 #endif
 179                 }
 180 #ifdef USE_PAM
 181                 if (options.use_pam)
 182                         PRIVSEP(start_pam(authctxt));
 183 #endif
 184                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 185                     use_privsep ? " [net]" : "");
 186                 authctxt->service = xstrdup(service);
 187                 authctxt->style = style ? xstrdup(style) : NULL;
 188                 if (use_privsep)
 189                         mm_inform_authserv(service, style);
 190         } else if (strcmp(user, authctxt->user) != 0 ||
 191             strcmp(service, authctxt->service) != 0) {
 192                 packet_disconnect("Change of username or service not allowed: "
 193                     "(%s,%s) -> (%s,%s)",
 194                     authctxt->user, authctxt->service, user, service);
 195         }
 196
 197 #ifdef HAVE_LOGIN_CAP
 198         if (authctxt->pw != NULL) {
 199                 lc = login_getpwclass(authctxt->pw);
 200                 if (lc == NULL)
 201                         lc = login_getclassbyname(NULL, authctxt->pw);
 202                 if (!auth_hostok(lc, from_host, from_ip)) {
 203                         logit("Denied connection for %.200s from %.200s [%.200s].",
 204                             authctxt->pw->pw_name, from_host, from_ip);
 205                         packet_disconnect("Sorry, you are not allowed to connect.");
 206                 }
 207                 if (!auth_timeok(lc, time(NULL))) {
 208                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 209                             authctxt->pw->pw_name, from_host);
 210                         packet_disconnect("Logins not available right now.");
 211                 }
 212                 login_close(lc);
 213                 lc = NULL;
 214         }
 215 #endif  /* HAVE_LOGIN_CAP */
 216
 217         /* reset state */
 218         auth2_challenge_stop(authctxt);
 219
 220 #ifdef GSSAPI
 221         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 222         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 223 #endif
 224
 225         authctxt->postponed = 0;
 226
 227         /* try to authenticate user */
 228         m = authmethod_lookup(method);
 229         if (m != NULL) {
 230                 debug2("input_userauth_request: try method %s", method);
 231                 authenticated = m->userauth(authctxt);
 232         }
 233         userauth_finish(authctxt, authenticated, method);
 234
 235         xfree(service);
 236         xfree(user);
 237         xfree(method);
 238 }
 239
 240 void
 241 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 242 {
 243         char *methods;
 244
 245         if (!authctxt->valid && authenticated)
 246                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 247                     authctxt->user);
 248
 249         /* Special handling for root */
 250         if (authenticated && authctxt->pw->pw_uid == 0 &&
 251             !auth_root_allowed(method)) {
 252                 authenticated = 0;
 253 #ifdef SSH_AUDIT_EVENTS
 254                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 255 #endif
 256         }
 257
 258 #ifdef USE_PAM
 259         if (options.use_pam && authenticated) {
 260                 if (!PRIVSEP(do_pam_account())) {
 261                         /* if PAM returned a message, send it to the user */
 262                         if (buffer_len(&loginmsg) > 0) {
 263                                 buffer_append(&loginmsg, "\0", 1);
 264                                 userauth_send_banner(buffer_ptr(&loginmsg));
 265                                 packet_write_wait();
 266                         }
 267                         fatal("Access denied for user %s by PAM account "
 268                             "configuration", authctxt->user);
 269                 }
 270         }
 271 #endif
 272
 273 #ifdef _UNICOS
 274         if (authenticated && cray_access_denied(authctxt->user)) {
 275                 authenticated = 0;
 276                 fatal("Access denied for user %s.",authctxt->user);
 277         }
 278 #endif /* _UNICOS */
 279
 280         /* Log before sending the reply */
 281         auth_log(authctxt, authenticated, method, " ssh2");
 282
 283         if (authctxt->postponed)
 284                 return;
 285
 286         /* XXX todo: check if multiple auth methods are needed */
 287         if (authenticated == 1) {
 288                 /* turn off userauth */
 289                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 290                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 291                 packet_send();
 292                 packet_write_wait();
 293                 /* now we can break out */
 294                 authctxt->success = 1;
 295         } else {
 296                 if (authctxt->failures++ > options.max_authtries) {
 297 #ifdef SSH_AUDIT_EVENTS
 298                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 299 #endif
 300                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 301                 }
 302                 methods = authmethods_get();
 303                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 304                 packet_put_cstring(methods);
 305                 packet_put_char(0);     /* XXX partial success, unused */
 306                 packet_send();
 307                 packet_write_wait();
 308                 xfree(methods);
 309         }
 310 }
 311
 312 static char *
 313 authmethods_get(void)
 314 {
 315         Buffer b;
 316         char *list;
 317         int i;
 318
 319         buffer_init(&b);
 320         for (i = 0; authmethods[i] != NULL; i++) {
 321                 if (strcmp(authmethods[i]->name, "none") == 0)
 322                         continue;
 323                 if (authmethods[i]->enabled != NULL &&
 324                     *(authmethods[i]->enabled) != 0) {
 325                         if (buffer_len(&b) > 0)
 326                                 buffer_append(&b, ",", 1);
 327                         buffer_append(&b, authmethods[i]->name,
 328                             strlen(authmethods[i]->name));
 329                 }
 330         }
 331         buffer_append(&b, "\0", 1);
 332         list = xstrdup(buffer_ptr(&b));
 333         buffer_free(&b);
 334         return list;
 335 }
 336
 337 static Authmethod *
 338 authmethod_lookup(const char *name)
 339 {
 340         int i;
 341
 342         if (name != NULL)
 343                 for (i = 0; authmethods[i] != NULL; i++)
 344                         if (authmethods[i]->enabled != NULL &&
 345                             *(authmethods[i]->enabled) != 0 &&
 346                             strcmp(name, authmethods[i]->name) == 0)
 347                                 return authmethods[i];
 348         debug2("Unrecognized authentication method name: %s",
 349             name ? name : "NULL");
 350         return NULL;
 351 }