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
  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 "atomicio.h"
  39 #include "xmalloc.h"
  40 #include "ssh2.h"
  41 #include "packet.h"
  42 #include "log.h"
  43 #include "buffer.h"
  44 #include "servconf.h"
  45 #include "compat.h"
  46 #include "key.h"
  47 #include "hostfile.h"
  48 #include "auth.h"
  49 #include "dispatch.h"
  50 #include "pathnames.h"
  51 #include "buffer.h"
  52 #include "canohost.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 #ifdef JPAKE
  76 extern Authmethod method_jpake;
  77 #endif
  78
  79 static int log_flag = 0;
  80
  81
  82 Authmethod *authmethods[] = {
  83         &method_none,
  84         &method_pubkey,
  85 #ifdef GSSAPI
  86         &method_gssapi,
  87 #endif
  88 #ifdef JPAKE
  89         &method_jpake,
  90 #endif
  91         &method_passwd,
  92         &method_kbdint,
  93         &method_hostbased,
  94         NULL
  95 };
  96
  97 /* protocol */
  98
  99 static void input_service_request(int, u_int32_t, void *);
 100 static void input_userauth_request(int, u_int32_t, void *);
 101
 102 /* helper */
 103 static Authmethod *authmethod_lookup(const char *);
 104 static char *authmethods_get(void);
 105
 106 char *
 107 auth2_read_banner(void)
 108 {
 109         struct stat st;
 110         char *banner = NULL;
 111         size_t len, n;
 112         int fd;
 113
 114         if ((fd = open(options.banner, O_RDONLY)) == -1)
 115                 return (NULL);
 116         if (fstat(fd, &st) == -1) {
 117                 close(fd);
 118                 return (NULL);
 119         }
 120         if (st.st_size > 1*1024*1024) {
 121                 close(fd);
 122                 return (NULL);
 123         }
 124
 125         len = (size_t)st.st_size;               /* truncate */
 126         banner = xmalloc(len + 1);
 127         n = atomicio(read, fd, banner, len);
 128         close(fd);
 129
 130         if (n != len) {
 131                 xfree(banner);
 132                 return (NULL);
 133         }
 134         banner[n] = '\0';
 135
 136         return (banner);
 137 }
 138
 139 void
 140 userauth_send_banner(const char *msg)
 141 {
 142         if (datafellows & SSH_BUG_BANNER)
 143                 return;
 144
 145         packet_start(SSH2_MSG_USERAUTH_BANNER);
 146         packet_put_cstring(msg);
 147         packet_put_cstring("");         /* language, unused */
 148         packet_send();
 149         debug("%s: sent", __func__);
 150 }
 151
 152 static void
 153 userauth_banner(void)
 154 {
 155         char *banner = NULL;
 156
 157         if (options.banner == NULL ||
 158             strcasecmp(options.banner, "none") == 0 ||
 159             (datafellows & SSH_BUG_BANNER) != 0)
 160                 return;
 161
 162         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 163                 goto done;
 164         userauth_send_banner(banner);
 165
 166 done:
 167         if (banner)
 168                 xfree(banner);
 169 }
 170
 171 /*
 172  * loop until authctxt->success == TRUE
 173  */
 174 void
 175 do_authentication2(Authctxt *authctxt)
 176 {
 177         dispatch_init(&dispatch_protocol_error);
 178         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 179         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 180 }
 181
 182 /*ARGSUSED*/
 183 static void
 184 input_service_request(int type, u_int32_t seq, void *ctxt)
 185 {
 186         Authctxt *authctxt = ctxt;
 187         u_int len;
 188         int acceptit = 0;
 189         char *service = packet_get_string(&len);
 190         packet_check_eom();
 191
 192         if (authctxt == NULL)
 193                 fatal("input_service_request: no authctxt");
 194
 195         if (strcmp(service, "ssh-userauth") == 0) {
 196                 if (!authctxt->success) {
 197                         acceptit = 1;
 198                         /* now we can handle user-auth requests */
 199                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 200                 }
 201         }
 202         /* XXX all other service requests are denied */
 203
 204         if (acceptit) {
 205                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 206                 packet_put_cstring(service);
 207                 packet_send();
 208                 packet_write_wait();
 209         } else {
 210                 debug("bad service request %s", service);
 211                 packet_disconnect("bad service request %s", service);
 212         }
 213         xfree(service);
 214 }
 215
 216 /*ARGSUSED*/
 217 static void
 218 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 219 {
 220         Authctxt *authctxt = ctxt;
 221         Authmethod *m = NULL;
 222         char *user, *service, *method, *style = NULL;
 223         int authenticated = 0;
 224 #ifdef HAVE_LOGIN_CAP
 225         login_cap_t *lc;
 226         const char *from_host, *from_ip;
 227
 228         from_host = get_canonical_hostname(options.use_dns);
 229         from_ip = get_remote_ipaddr();
 230 #endif
 231
 232         if (authctxt == NULL)
 233                 fatal("input_userauth_request: no authctxt");
 234
 235         user = packet_get_string(NULL);
 236         service = packet_get_string(NULL);
 237         method = packet_get_string(NULL);
 238         debug("userauth-request for user %s service %s method %s", user, service, method);
 239         if (!log_flag) {
 240                 logit("SSH: Server;Ltype: Authname;Remote: %s-%d;Name: %s",
 241                       get_remote_ipaddr(), get_remote_port(), user);
 242                 log_flag = 1;
 243         }
 244         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 245
 246         if ((style = strchr(user, ':')) != NULL)
 247                 *style++ = 0;
 248
 249         if (authctxt->attempt++ == 0) {
 250                 /* setup auth context */
 251                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 252                 authctxt->user = xstrdup(user);
 253                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 254                         authctxt->valid = 1;
 255                         debug2("input_userauth_request: setting up authctxt for %s", user);
 256                 } else {
 257                         logit("input_userauth_request: invalid user %s", user);
 258                         authctxt->pw = fakepw();
 259 #ifdef SSH_AUDIT_EVENTS
 260                         PRIVSEP(audit_event(SSH_INVALID_USER));
 261 #endif
 262                 }
 263 #ifdef USE_PAM
 264                 if (options.use_pam)
 265                         PRIVSEP(start_pam(authctxt));
 266 #endif
 267                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 268                     use_privsep ? " [net]" : "");
 269                 authctxt->service = xstrdup(service);
 270                 authctxt->style = style ? xstrdup(style) : NULL;
 271                 if (use_privsep)
 272                         mm_inform_authserv(service, style);
 273                 userauth_banner();
 274         } else if (strcmp(user, authctxt->user) != 0 ||
 275             strcmp(service, authctxt->service) != 0) {
 276                 packet_disconnect("Change of username or service not allowed: "
 277                     "(%s,%s) -> (%s,%s)",
 278                     authctxt->user, authctxt->service, user, service);
 279         }
 280
 281 #ifdef HAVE_LOGIN_CAP
 282         if (authctxt->pw != NULL) {
 283                 lc = login_getpwclass(authctxt->pw);
 284                 if (lc == NULL)
 285                         lc = login_getclassbyname(NULL, authctxt->pw);
 286                 if (!auth_hostok(lc, from_host, from_ip)) {
 287                         logit("Denied connection for %.200s from %.200s [%.200s].",
 288                             authctxt->pw->pw_name, from_host, from_ip);
 289                         packet_disconnect("Sorry, you are not allowed to connect.");
 290                 }
 291                 if (!auth_timeok(lc, time(NULL))) {
 292                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 293                             authctxt->pw->pw_name, from_host);
 294                         packet_disconnect("Logins not available right now.");
 295                 }
 296                 login_close(lc);
 297                 lc = NULL;
 298         }
 299 #endif  /* HAVE_LOGIN_CAP */
 300
 301         /* reset state */
 302         auth2_challenge_stop(authctxt);
 303 #ifdef JPAKE
 304         auth2_jpake_stop(authctxt);
 305 #endif
 306
 307 #ifdef GSSAPI
 308         /* XXX move to auth2_gssapi_stop() */
 309         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 310         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 311 #endif
 312
 313         authctxt->postponed = 0;
 314
 315         /* try to authenticate user */
 316         m = authmethod_lookup(method);
 317         if (m != NULL && authctxt->failures < options.max_authtries) {
 318                 debug2("input_userauth_request: try method %s", method);
 319                 authenticated = m->userauth(authctxt);
 320         }
 321         userauth_finish(authctxt, authenticated, method);
 322
 323         xfree(service);
 324         xfree(user);
 325         xfree(method);
 326 }
 327
 328 void
 329 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 330 {
 331         char *methods;
 332
 333         if (!authctxt->valid && authenticated)
 334                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 335                     authctxt->user);
 336
 337         /* Special handling for root */
 338         if (authenticated && authctxt->pw->pw_uid == 0 &&
 339             !auth_root_allowed(method)) {
 340                 authenticated = 0;
 341 #ifdef SSH_AUDIT_EVENTS
 342                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 343 #endif
 344         }
 345
 346 #ifdef USE_PAM
 347         if (options.use_pam && authenticated) {
 348                 if (!PRIVSEP(do_pam_account())) {
 349                         /* if PAM returned a message, send it to the user */
 350                         if (buffer_len(&loginmsg) > 0) {
 351                                 buffer_append(&loginmsg, "\0", 1);
 352                                 userauth_send_banner(buffer_ptr(&loginmsg));
 353                                 packet_write_wait();
 354                         }
 355                         fatal("Access denied for user %s by PAM account "
 356                             "configuration", authctxt->user);
 357                 }
 358         }
 359 #endif
 360
 361 #ifdef _UNICOS
 362         if (authenticated && cray_access_denied(authctxt->user)) {
 363                 authenticated = 0;
 364                 fatal("Access denied for user %s.",authctxt->user);
 365         }
 366 #endif /* _UNICOS */
 367
 368         /* Log before sending the reply */
 369         auth_log(authctxt, authenticated, method, " ssh2");
 370
 371         if (authctxt->postponed)
 372                 return;
 373
 374         /* XXX todo: check if multiple auth methods are needed */
 375         if (authenticated == 1) {
 376                 /* turn off userauth */
 377                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 378                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 379                 packet_send();
 380                 packet_write_wait();
 381                 /* now we can break out */
 382                 authctxt->success = 1;
 383         } else {
 384
 385                 /* Allow initial try of "none" auth without failure penalty */
 386                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 387                         authctxt->failures++;
 388                 if (authctxt->failures >= options.max_authtries) {
 389 #ifdef SSH_AUDIT_EVENTS
 390                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 391 #endif
 392                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 393                 }
 394                 methods = authmethods_get();
 395                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 396                 packet_put_cstring(methods);
 397                 packet_put_char(0);     /* XXX partial success, unused */
 398                 packet_send();
 399                 packet_write_wait();
 400                 xfree(methods);
 401         }
 402 }
 403
 404 static char *
 405 authmethods_get(void)
 406 {
 407         Buffer b;
 408         char *list;
 409         int i;
 410
 411         buffer_init(&b);
 412         for (i = 0; authmethods[i] != NULL; i++) {
 413                 if (strcmp(authmethods[i]->name, "none") == 0)
 414                         continue;
 415                 if (authmethods[i]->enabled != NULL &&
 416                     *(authmethods[i]->enabled) != 0) {
 417                         if (buffer_len(&b) > 0)
 418                                 buffer_append(&b, ",", 1);
 419                         buffer_append(&b, authmethods[i]->name,
 420                             strlen(authmethods[i]->name));
 421                 }
 422         }
 423         buffer_append(&b, "\0", 1);
 424         list = xstrdup(buffer_ptr(&b));
 425         buffer_free(&b);
 426         return list;
 427 }
 428
 429 static Authmethod *
 430 authmethod_lookup(const char *name)
 431 {
 432         int i;
 433
 434         if (name != NULL)
 435                 for (i = 0; authmethods[i] != NULL; i++)
 436                         if (authmethods[i]->enabled != NULL &&
 437                             *(authmethods[i]->enabled) != 0 &&
 438                             strcmp(name, authmethods[i]->name) == 0)
 439                                 return authmethods[i];
 440         debug2("Unrecognized authentication method name: %s",
 441             name ? name : "NULL");
 442         return NULL;
 443 }
 444