crypto/openssh/auth2.c

   1 /* $OpenBSD: auth2.c,v 1.119 2008/07/04 23:30:16 djm 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 #include <sys/stat.h>
  30 #include <sys/uio.h>
  31
  32 #include <fcntl.h>
  33 #include <pwd.h>
  34 #include <stdarg.h>
  35 #include <string.h>
  36 #include <unistd.h>
  37
  38 #include "xmalloc.h"
  39 #include "canohost.h"
  40 #include "atomicio.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
  54 #ifdef GSSAPI
  55 #include "ssh-gss.h"
  56 #endif
  57 #include "monitor_wrap.h"
  58
  59 /* import */
  60 extern ServerOptions options;
  61 extern u_char *session_id2;
  62 extern u_int session_id2_len;
  63 extern Buffer loginmsg;
  64
  65 /* methods */
  66
  67 extern Authmethod method_none;
  68 extern Authmethod method_pubkey;
  69 extern Authmethod method_passwd;
  70 extern Authmethod method_kbdint;
  71 extern Authmethod method_hostbased;
  72 #ifdef GSSAPI
  73 extern Authmethod method_gssapi;
  74 #endif
  75
  76 Authmethod *authmethods[] = {
  77         &method_none,
  78         &method_pubkey,
  79 #ifdef GSSAPI
  80         &method_gssapi,
  81 #endif
  82         &method_passwd,
  83         &method_kbdint,
  84         &method_hostbased,
  85         NULL
  86 };
  87
  88 /* protocol */
  89
  90 static void input_service_request(int, u_int32_t, void *);
  91 static void input_userauth_request(int, u_int32_t, void *);
  92
  93 /* helper */
  94 static Authmethod *authmethod_lookup(const char *);
  95 static char *authmethods_get(void);
  96
  97 char *
  98 auth2_read_banner(void)
  99 {
 100         struct stat st;
 101         char *banner = NULL;
 102         size_t len, n;
 103         int fd;
 104
 105         if ((fd = open(options.banner, O_RDONLY)) == -1)
 106                 return (NULL);
 107         if (fstat(fd, &st) == -1) {
 108                 close(fd);
 109                 return (NULL);
 110         }
 111         if (st.st_size > 1*1024*1024) {
 112                 close(fd);
 113                 return (NULL);
 114         }
 115
 116         len = (size_t)st.st_size;               /* truncate */
 117         banner = xmalloc(len + 1);
 118         n = atomicio(read, fd, banner, len);
 119         close(fd);
 120
 121         if (n != len) {
 122                 xfree(banner);
 123                 return (NULL);
 124         }
 125         banner[n] = '\0';
 126
 127         return (banner);
 128 }
 129
 130 void
 131 userauth_send_banner(const char *msg)
 132 {
 133         if (datafellows & SSH_BUG_BANNER)
 134                 return;
 135
 136         packet_start(SSH2_MSG_USERAUTH_BANNER);
 137         packet_put_cstring(msg);
 138         packet_put_cstring("");         /* language, unused */
 139         packet_send();
 140         debug("%s: sent", __func__);
 141 }
 142
 143 static void
 144 userauth_banner(void)
 145 {
 146         char *banner = NULL;
 147
 148         if (options.banner == NULL ||
 149             strcasecmp(options.banner, "none") == 0 ||
 150             (datafellows & SSH_BUG_BANNER) != 0)
 151                 return;
 152
 153         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 154                 goto done;
 155         userauth_send_banner(banner);
 156
 157 done:
 158         if (banner)
 159                 xfree(banner);
 160 }
 161
 162 /*
 163  * loop until authctxt->success == TRUE
 164  */
 165 void
 166 do_authentication2(Authctxt *authctxt)
 167 {
 168         dispatch_init(&dispatch_protocol_error);
 169         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 170         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 171 }
 172
 173 /*ARGSUSED*/
 174 static void
 175 input_service_request(int type, u_int32_t seq, void *ctxt)
 176 {
 177         Authctxt *authctxt = ctxt;
 178         u_int len;
 179         int acceptit = 0;
 180         char *service = packet_get_string(&len);
 181         packet_check_eom();
 182
 183         if (authctxt == NULL)
 184                 fatal("input_service_request: no authctxt");
 185
 186         if (strcmp(service, "ssh-userauth") == 0) {
 187                 if (!authctxt->success) {
 188                         acceptit = 1;
 189                         /* now we can handle user-auth requests */
 190                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 191                 }
 192         }
 193         /* XXX all other service requests are denied */
 194
 195         if (acceptit) {
 196                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 197                 packet_put_cstring(service);
 198                 packet_send();
 199                 packet_write_wait();
 200         } else {
 201                 debug("bad service request %s", service);
 202                 packet_disconnect("bad service request %s", service);
 203         }
 204         xfree(service);
 205 }
 206
 207 /*ARGSUSED*/
 208 static void
 209 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 210 {
 211         Authctxt *authctxt = ctxt;
 212         Authmethod *m = NULL;
 213         char *user, *service, *method, *style = NULL;
 214         int authenticated = 0;
 215 #ifdef HAVE_LOGIN_CAP
 216         login_cap_t *lc;
 217         const char *from_host, *from_ip;
 218
 219         from_host = get_canonical_hostname(options.use_dns);
 220         from_ip = get_remote_ipaddr();
 221 #endif
 222
 223         if (authctxt == NULL)
 224                 fatal("input_userauth_request: no authctxt");
 225
 226         user = packet_get_string(NULL);
 227         service = packet_get_string(NULL);
 228         method = packet_get_string(NULL);
 229         debug("userauth-request for user %s service %s method %s", user, service, method);
 230         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 231
 232         if ((style = strchr(user, ':')) != NULL)
 233                 *style++ = 0;
 234
 235         if (authctxt->attempt++ == 0) {
 236                 /* setup auth context */
 237                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 238                 authctxt->user = xstrdup(user);
 239                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 240                         authctxt->valid = 1;
 241                         debug2("input_userauth_request: setting up authctxt for %s", user);
 242                 } else {
 243                         logit("input_userauth_request: invalid user %s", user);
 244                         authctxt->pw = fakepw();
 245 #ifdef SSH_AUDIT_EVENTS
 246                         PRIVSEP(audit_event(SSH_INVALID_USER));
 247 #endif
 248                 }
 249 #ifdef USE_PAM
 250                 if (options.use_pam)
 251                         PRIVSEP(start_pam(authctxt));
 252 #endif
 253                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 254                     use_privsep ? " [net]" : "");
 255                 authctxt->service = xstrdup(service);
 256                 authctxt->style = style ? xstrdup(style) : NULL;
 257                 if (use_privsep)
 258                         mm_inform_authserv(service, style);
 259                 userauth_banner();
 260         } else if (strcmp(user, authctxt->user) != 0 ||
 261             strcmp(service, authctxt->service) != 0) {
 262                 packet_disconnect("Change of username or service not allowed: "
 263                     "(%s,%s) -> (%s,%s)",
 264                     authctxt->user, authctxt->service, user, service);
 265         }
 266
 267 #ifdef HAVE_LOGIN_CAP
 268         if (authctxt->pw != NULL) {
 269                 lc = login_getpwclass(authctxt->pw);
 270                 if (lc == NULL)
 271                         lc = login_getclassbyname(NULL, authctxt->pw);
 272                 if (!auth_hostok(lc, from_host, from_ip)) {
 273                         logit("Denied connection for %.200s from %.200s [%.200s].",
 274                             authctxt->pw->pw_name, from_host, from_ip);
 275                         packet_disconnect("Sorry, you are not allowed to connect.");
 276                 }
 277                 if (!auth_timeok(lc, time(NULL))) {
 278                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 279                             authctxt->pw->pw_name, from_host);
 280                         packet_disconnect("Logins not available right now.");
 281                 }
 282                 login_close(lc);
 283                 lc = NULL;
 284         }
 285 #endif  /* HAVE_LOGIN_CAP */
 286
 287         /* reset state */
 288         auth2_challenge_stop(authctxt);
 289
 290 #ifdef GSSAPI
 291         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 292         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 293 #endif
 294
 295         authctxt->postponed = 0;
 296
 297         /* try to authenticate user */
 298         m = authmethod_lookup(method);
 299         if (m != NULL && authctxt->failures < options.max_authtries) {
 300                 debug2("input_userauth_request: try method %s", method);
 301                 authenticated = m->userauth(authctxt);
 302         }
 303         userauth_finish(authctxt, authenticated, method);
 304
 305         xfree(service);
 306         xfree(user);
 307         xfree(method);
 308 }
 309
 310 void
 311 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 312 {
 313         char *methods;
 314
 315         if (!authctxt->valid && authenticated)
 316                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 317                     authctxt->user);
 318
 319         /* Special handling for root */
 320         if (authenticated && authctxt->pw->pw_uid == 0 &&
 321             !auth_root_allowed(method)) {
 322                 authenticated = 0;
 323 #ifdef SSH_AUDIT_EVENTS
 324                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 325 #endif
 326         }
 327
 328 #ifdef USE_PAM
 329         if (options.use_pam && authenticated) {
 330                 if (!PRIVSEP(do_pam_account())) {
 331                         /* if PAM returned a message, send it to the user */
 332                         if (buffer_len(&loginmsg) > 0) {
 333                                 buffer_append(&loginmsg, "\0", 1);
 334                                 userauth_send_banner(buffer_ptr(&loginmsg));
 335                                 packet_write_wait();
 336                         }
 337                         fatal("Access denied for user %s by PAM account "
 338                             "configuration", authctxt->user);
 339                 }
 340         }
 341 #endif
 342
 343 #ifdef _UNICOS
 344         if (authenticated && cray_access_denied(authctxt->user)) {
 345                 authenticated = 0;
 346                 fatal("Access denied for user %s.",authctxt->user);
 347         }
 348 #endif /* _UNICOS */
 349
 350         /* Log before sending the reply */
 351         auth_log(authctxt, authenticated, method, " ssh2");
 352
 353         if (authctxt->postponed)
 354                 return;
 355
 356         /* XXX todo: check if multiple auth methods are needed */
 357         if (authenticated == 1) {
 358                 /* turn off userauth */
 359                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 360                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 361                 packet_send();
 362                 packet_write_wait();
 363                 /* now we can break out */
 364                 authctxt->success = 1;
 365         } else {
 366
 367                 /* Allow initial try of "none" auth without failure penalty */
 368                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 369                         authctxt->failures++;
 370                 if (authctxt->failures >= options.max_authtries) {
 371 #ifdef SSH_AUDIT_EVENTS
 372                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 373 #endif
 374                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 375                 }
 376                 methods = authmethods_get();
 377                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 378                 packet_put_cstring(methods);
 379                 packet_put_char(0);     /* XXX partial success, unused */
 380                 packet_send();
 381                 packet_write_wait();
 382                 xfree(methods);
 383         }
 384 }
 385
 386 static char *
 387 authmethods_get(void)
 388 {
 389         Buffer b;
 390         char *list;
 391         int i;
 392
 393         buffer_init(&b);
 394         for (i = 0; authmethods[i] != NULL; i++) {
 395                 if (strcmp(authmethods[i]->name, "none") == 0)
 396                         continue;
 397                 if (authmethods[i]->enabled != NULL &&
 398                     *(authmethods[i]->enabled) != 0) {
 399                         if (buffer_len(&b) > 0)
 400                                 buffer_append(&b, ",", 1);
 401                         buffer_append(&b, authmethods[i]->name,
 402                             strlen(authmethods[i]->name));
 403                 }
 404         }
 405         buffer_append(&b, "\0", 1);
 406         list = xstrdup(buffer_ptr(&b));
 407         buffer_free(&b);
 408         return list;
 409 }
 410
 411 static Authmethod *
 412 authmethod_lookup(const char *name)
 413 {
 414         int i;
 415
 416         if (name != NULL)
 417                 for (i = 0; authmethods[i] != NULL; i++)
 418                         if (authmethods[i]->enabled != NULL &&
 419                             *(authmethods[i]->enabled) != 0 &&
 420                             strcmp(name, authmethods[i]->name) == 0)
 421                                 return authmethods[i];
 422         debug2("Unrecognized authentication method name: %s",
 423             name ? name : "NULL");
 424         return NULL;
 425 }
 426