crypto/openssh/auth2.c

   1 /* $OpenBSD: auth2.c,v 1.121 2009/06/22 05:39:28 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 __RCSID("$FreeBSD$");
  28
  29 #include <sys/types.h>
  30 #include <sys/stat.h>
  31 #include <sys/uio.h>
  32
  33 #include <fcntl.h>
  34 #include <pwd.h>
  35 #include <stdarg.h>
  36 #include <string.h>
  37 #include <unistd.h>
  38
  39 #include "atomicio.h"
  40 #include "xmalloc.h"
  41 #include "ssh2.h"
  42 #include "packet.h"
  43 #include "log.h"
  44 #include "buffer.h"
  45 #include "servconf.h"
  46 #include "compat.h"
  47 #include "key.h"
  48 #include "hostfile.h"
  49 #include "auth.h"
  50 #include "dispatch.h"
  51 #include "pathnames.h"
  52 #include "buffer.h"
  53 #include "canohost.h"
  54
  55 #ifdef GSSAPI
  56 #include "ssh-gss.h"
  57 #endif
  58 #include "monitor_wrap.h"
  59
  60 /* import */
  61 extern ServerOptions options;
  62 extern u_char *session_id2;
  63 extern u_int session_id2_len;
  64 extern Buffer loginmsg;
  65
  66 /* methods */
  67
  68 extern Authmethod method_none;
  69 extern Authmethod method_pubkey;
  70 extern Authmethod method_passwd;
  71 extern Authmethod method_kbdint;
  72 extern Authmethod method_hostbased;
  73 #ifdef GSSAPI
  74 extern Authmethod method_gssapi;
  75 #endif
  76 #ifdef JPAKE
  77 extern Authmethod method_jpake;
  78 #endif
  79
  80 Authmethod *authmethods[] = {
  81         &method_none,
  82         &method_pubkey,
  83 #ifdef GSSAPI
  84         &method_gssapi,
  85 #endif
  86 #ifdef JPAKE
  87         &method_jpake,
  88 #endif
  89         &method_passwd,
  90         &method_kbdint,
  91         &method_hostbased,
  92         NULL
  93 };
  94
  95 /* protocol */
  96
  97 static void input_service_request(int, u_int32_t, void *);
  98 static void input_userauth_request(int, u_int32_t, void *);
  99
 100 /* helper */
 101 static Authmethod *authmethod_lookup(const char *);
 102 static char *authmethods_get(void);
 103
 104 char *
 105 auth2_read_banner(void)
 106 {
 107         struct stat st;
 108         char *banner = NULL;
 109         size_t len, n;
 110         int fd;
 111
 112         if ((fd = open(options.banner, O_RDONLY)) == -1)
 113                 return (NULL);
 114         if (fstat(fd, &st) == -1) {
 115                 close(fd);
 116                 return (NULL);
 117         }
 118         if (st.st_size > 1*1024*1024) {
 119                 close(fd);
 120                 return (NULL);
 121         }
 122
 123         len = (size_t)st.st_size;               /* truncate */
 124         banner = xmalloc(len + 1);
 125         n = atomicio(read, fd, banner, len);
 126         close(fd);
 127
 128         if (n != len) {
 129                 xfree(banner);
 130                 return (NULL);
 131         }
 132         banner[n] = '\0';
 133
 134         return (banner);
 135 }
 136
 137 void
 138 userauth_send_banner(const char *msg)
 139 {
 140         if (datafellows & SSH_BUG_BANNER)
 141                 return;
 142
 143         packet_start(SSH2_MSG_USERAUTH_BANNER);
 144         packet_put_cstring(msg);
 145         packet_put_cstring("");         /* language, unused */
 146         packet_send();
 147         debug("%s: sent", __func__);
 148 }
 149
 150 static void
 151 userauth_banner(void)
 152 {
 153         char *banner = NULL;
 154
 155         if (options.banner == NULL ||
 156             strcasecmp(options.banner, "none") == 0 ||
 157             (datafellows & SSH_BUG_BANNER) != 0)
 158                 return;
 159
 160         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 161                 goto done;
 162         userauth_send_banner(banner);
 163
 164 done:
 165         if (banner)
 166                 xfree(banner);
 167 }
 168
 169 /*
 170  * loop until authctxt->success == TRUE
 171  */
 172 void
 173 do_authentication2(Authctxt *authctxt)
 174 {
 175         dispatch_init(&dispatch_protocol_error);
 176         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 177         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 178 }
 179
 180 /*ARGSUSED*/
 181 static void
 182 input_service_request(int type, u_int32_t seq, void *ctxt)
 183 {
 184         Authctxt *authctxt = ctxt;
 185         u_int len;
 186         int acceptit = 0;
 187         char *service = packet_get_string(&len);
 188         packet_check_eom();
 189
 190         if (authctxt == NULL)
 191                 fatal("input_service_request: no authctxt");
 192
 193         if (strcmp(service, "ssh-userauth") == 0) {
 194                 if (!authctxt->success) {
 195                         acceptit = 1;
 196                         /* now we can handle user-auth requests */
 197                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 198                 }
 199         }
 200         /* XXX all other service requests are denied */
 201
 202         if (acceptit) {
 203                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 204                 packet_put_cstring(service);
 205                 packet_send();
 206                 packet_write_wait();
 207         } else {
 208                 debug("bad service request %s", service);
 209                 packet_disconnect("bad service request %s", service);
 210         }
 211         xfree(service);
 212 }
 213
 214 /*ARGSUSED*/
 215 static void
 216 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 217 {
 218         Authctxt *authctxt = ctxt;
 219         Authmethod *m = NULL;
 220         char *user, *service, *method, *style = NULL;
 221         int authenticated = 0;
 222 #ifdef HAVE_LOGIN_CAP
 223         login_cap_t *lc;
 224         const char *from_host, *from_ip;
 225
 226         from_host = get_canonical_hostname(options.use_dns);
 227         from_ip = get_remote_ipaddr();
 228 #endif
 229
 230         if (authctxt == NULL)
 231                 fatal("input_userauth_request: no authctxt");
 232
 233         user = packet_get_string(NULL);
 234         service = packet_get_string(NULL);
 235         method = packet_get_string(NULL);
 236         debug("userauth-request for user %s service %s method %s", user, service, method);
 237         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 238
 239         if ((style = strchr(user, ':')) != NULL)
 240                 *style++ = 0;
 241
 242         if (authctxt->attempt++ == 0) {
 243                 /* setup auth context */
 244                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 245                 authctxt->user = xstrdup(user);
 246                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 247                         authctxt->valid = 1;
 248                         debug2("input_userauth_request: setting up authctxt for %s", user);
 249                 } else {
 250                         logit("input_userauth_request: invalid user %s", user);
 251                         authctxt->pw = fakepw();
 252 #ifdef SSH_AUDIT_EVENTS
 253                         PRIVSEP(audit_event(SSH_INVALID_USER));
 254 #endif
 255                 }
 256 #ifdef USE_PAM
 257                 if (options.use_pam)
 258                         PRIVSEP(start_pam(authctxt));
 259 #endif
 260                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 261                     use_privsep ? " [net]" : "");
 262                 authctxt->service = xstrdup(service);
 263                 authctxt->style = style ? xstrdup(style) : NULL;
 264                 if (use_privsep)
 265                         mm_inform_authserv(service, style);
 266                 userauth_banner();
 267         } else if (strcmp(user, authctxt->user) != 0 ||
 268             strcmp(service, authctxt->service) != 0) {
 269                 packet_disconnect("Change of username or service not allowed: "
 270                     "(%s,%s) -> (%s,%s)",
 271                     authctxt->user, authctxt->service, user, service);
 272         }
 273
 274 #ifdef HAVE_LOGIN_CAP
 275         if (authctxt->pw != NULL) {
 276                 lc = login_getpwclass(authctxt->pw);
 277                 if (lc == NULL)
 278                         lc = login_getclassbyname(NULL, authctxt->pw);
 279                 if (!auth_hostok(lc, from_host, from_ip)) {
 280                         logit("Denied connection for %.200s from %.200s [%.200s].",
 281                             authctxt->pw->pw_name, from_host, from_ip);
 282                         packet_disconnect("Sorry, you are not allowed to connect.");
 283                 }
 284                 if (!auth_timeok(lc, time(NULL))) {
 285                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 286                             authctxt->pw->pw_name, from_host);
 287                         packet_disconnect("Logins not available right now.");
 288                 }
 289                 login_close(lc);
 290                 lc = NULL;
 291         }
 292 #endif  /* HAVE_LOGIN_CAP */
 293
 294         /* reset state */
 295         auth2_challenge_stop(authctxt);
 296 #ifdef JPAKE
 297         auth2_jpake_stop(authctxt);
 298 #endif
 299
 300 #ifdef GSSAPI
 301         /* XXX move to auth2_gssapi_stop() */
 302         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 303         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 304 #endif
 305
 306         authctxt->postponed = 0;
 307
 308         /* try to authenticate user */
 309         m = authmethod_lookup(method);
 310         if (m != NULL && authctxt->failures < options.max_authtries) {
 311                 debug2("input_userauth_request: try method %s", method);
 312                 authenticated = m->userauth(authctxt);
 313         }
 314         userauth_finish(authctxt, authenticated, method);
 315
 316         xfree(service);
 317         xfree(user);
 318         xfree(method);
 319 }
 320
 321 void
 322 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 323 {
 324         char *methods;
 325
 326         if (!authctxt->valid && authenticated)
 327                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 328                     authctxt->user);
 329
 330         /* Special handling for root */
 331         if (authenticated && authctxt->pw->pw_uid == 0 &&
 332             !auth_root_allowed(method)) {
 333                 authenticated = 0;
 334 #ifdef SSH_AUDIT_EVENTS
 335                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 336 #endif
 337         }
 338
 339 #ifdef USE_PAM
 340         if (options.use_pam && authenticated) {
 341                 if (!PRIVSEP(do_pam_account())) {
 342                         /* if PAM returned a message, send it to the user */
 343                         if (buffer_len(&loginmsg) > 0) {
 344                                 buffer_append(&loginmsg, "\0", 1);
 345                                 userauth_send_banner(buffer_ptr(&loginmsg));
 346                                 packet_write_wait();
 347                         }
 348                         fatal("Access denied for user %s by PAM account "
 349                             "configuration", authctxt->user);
 350                 }
 351         }
 352 #endif
 353
 354 #ifdef _UNICOS
 355         if (authenticated && cray_access_denied(authctxt->user)) {
 356                 authenticated = 0;
 357                 fatal("Access denied for user %s.",authctxt->user);
 358         }
 359 #endif /* _UNICOS */
 360
 361         /* Log before sending the reply */
 362         auth_log(authctxt, authenticated, method, " ssh2");
 363
 364         if (authctxt->postponed)
 365                 return;
 366
 367         /* XXX todo: check if multiple auth methods are needed */
 368         if (authenticated == 1) {
 369                 /* turn off userauth */
 370                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 371                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 372                 packet_send();
 373                 packet_write_wait();
 374                 /* now we can break out */
 375                 authctxt->success = 1;
 376         } else {
 377
 378                 /* Allow initial try of "none" auth without failure penalty */
 379                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 380                         authctxt->failures++;
 381                 if (authctxt->failures >= options.max_authtries) {
 382 #ifdef SSH_AUDIT_EVENTS
 383                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 384 #endif
 385                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 386                 }
 387                 methods = authmethods_get();
 388                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 389                 packet_put_cstring(methods);
 390                 packet_put_char(0);     /* XXX partial success, unused */
 391                 packet_send();
 392                 packet_write_wait();
 393                 xfree(methods);
 394         }
 395 }
 396
 397 static char *
 398 authmethods_get(void)
 399 {
 400         Buffer b;
 401         char *list;
 402         int i;
 403
 404         buffer_init(&b);
 405         for (i = 0; authmethods[i] != NULL; i++) {
 406                 if (strcmp(authmethods[i]->name, "none") == 0)
 407                         continue;
 408                 if (authmethods[i]->enabled != NULL &&
 409                     *(authmethods[i]->enabled) != 0) {
 410                         if (buffer_len(&b) > 0)
 411                                 buffer_append(&b, ",", 1);
 412                         buffer_append(&b, authmethods[i]->name,
 413                             strlen(authmethods[i]->name));
 414                 }
 415         }
 416         buffer_append(&b, "\0", 1);
 417         list = xstrdup(buffer_ptr(&b));
 418         buffer_free(&b);
 419         return list;
 420 }
 421
 422 static Authmethod *
 423 authmethod_lookup(const char *name)
 424 {
 425         int i;
 426
 427         if (name != NULL)
 428                 for (i = 0; authmethods[i] != NULL; i++)
 429                         if (authmethods[i]->enabled != NULL &&
 430                             *(authmethods[i]->enabled) != 0 &&
 431                             strcmp(name, authmethods[i]->name) == 0)
 432                                 return authmethods[i];
 433         debug2("Unrecognized authentication method name: %s",
 434             name ? name : "NULL");
 435         return NULL;
 436 }
 437