crypto/openssh/auth2.c

   1 /* $OpenBSD: auth2.c,v 1.120 2008/11/04 08:22:12 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 #ifdef JPAKE
  76 extern Authmethod method_jpake;
  77 #endif
  78
  79 Authmethod *authmethods[] = {
  80         &method_none,
  81         &method_pubkey,
  82 #ifdef GSSAPI
  83         &method_gssapi,
  84 #endif
  85 #ifdef JPAKE
  86         &method_jpake,
  87 #endif
  88         &method_passwd,
  89         &method_kbdint,
  90         &method_hostbased,
  91         NULL
  92 };
  93
  94 /* protocol */
  95
  96 static void input_service_request(int, u_int32_t, void *);
  97 static void input_userauth_request(int, u_int32_t, void *);
  98
  99 /* helper */
 100 static Authmethod *authmethod_lookup(const char *);
 101 static char *authmethods_get(void);
 102
 103 char *
 104 auth2_read_banner(void)
 105 {
 106         struct stat st;
 107         char *banner = NULL;
 108         size_t len, n;
 109         int fd;
 110
 111         if ((fd = open(options.banner, O_RDONLY)) == -1)
 112                 return (NULL);
 113         if (fstat(fd, &st) == -1) {
 114                 close(fd);
 115                 return (NULL);
 116         }
 117         if (st.st_size > 1*1024*1024) {
 118                 close(fd);
 119                 return (NULL);
 120         }
 121
 122         len = (size_t)st.st_size;               /* truncate */
 123         banner = xmalloc(len + 1);
 124         n = atomicio(read, fd, banner, len);
 125         close(fd);
 126
 127         if (n != len) {
 128                 xfree(banner);
 129                 return (NULL);
 130         }
 131         banner[n] = '\0';
 132
 133         return (banner);
 134 }
 135
 136 void
 137 userauth_send_banner(const char *msg)
 138 {
 139         if (datafellows & SSH_BUG_BANNER)
 140                 return;
 141
 142         packet_start(SSH2_MSG_USERAUTH_BANNER);
 143         packet_put_cstring(msg);
 144         packet_put_cstring("");         /* language, unused */
 145         packet_send();
 146         debug("%s: sent", __func__);
 147 }
 148
 149 static void
 150 userauth_banner(void)
 151 {
 152         char *banner = NULL;
 153
 154         if (options.banner == NULL ||
 155             strcasecmp(options.banner, "none") == 0 ||
 156             (datafellows & SSH_BUG_BANNER) != 0)
 157                 return;
 158
 159         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 160                 goto done;
 161         userauth_send_banner(banner);
 162
 163 done:
 164         if (banner)
 165                 xfree(banner);
 166 }
 167
 168 /*
 169  * loop until authctxt->success == TRUE
 170  */
 171 void
 172 do_authentication2(Authctxt *authctxt)
 173 {
 174         dispatch_init(&dispatch_protocol_error);
 175         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 176         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 177 }
 178
 179 /*ARGSUSED*/
 180 static void
 181 input_service_request(int type, u_int32_t seq, void *ctxt)
 182 {
 183         Authctxt *authctxt = ctxt;
 184         u_int len;
 185         int acceptit = 0;
 186         char *service = packet_get_string(&len);
 187         packet_check_eom();
 188
 189         if (authctxt == NULL)
 190                 fatal("input_service_request: no authctxt");
 191
 192         if (strcmp(service, "ssh-userauth") == 0) {
 193                 if (!authctxt->success) {
 194                         acceptit = 1;
 195                         /* now we can handle user-auth requests */
 196                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 197                 }
 198         }
 199         /* XXX all other service requests are denied */
 200
 201         if (acceptit) {
 202                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 203                 packet_put_cstring(service);
 204                 packet_send();
 205                 packet_write_wait();
 206         } else {
 207                 debug("bad service request %s", service);
 208                 packet_disconnect("bad service request %s", service);
 209         }
 210         xfree(service);
 211 }
 212
 213 /*ARGSUSED*/
 214 static void
 215 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 216 {
 217         Authctxt *authctxt = ctxt;
 218         Authmethod *m = NULL;
 219         char *user, *service, *method, *style = NULL;
 220         int authenticated = 0;
 221 #ifdef HAVE_LOGIN_CAP
 222         login_cap_t *lc;
 223         const char *from_host, *from_ip;
 224
 225         from_host = get_canonical_hostname(options.use_dns);
 226         from_ip = get_remote_ipaddr();
 227 #endif
 228
 229         if (authctxt == NULL)
 230                 fatal("input_userauth_request: no authctxt");
 231
 232         user = packet_get_string(NULL);
 233         service = packet_get_string(NULL);
 234         method = packet_get_string(NULL);
 235         debug("userauth-request for user %s service %s method %s", user, service, method);
 236         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 237
 238         if ((style = strchr(user, ':')) != NULL)
 239                 *style++ = 0;
 240
 241         if (authctxt->attempt++ == 0) {
 242                 /* setup auth context */
 243                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 244                 authctxt->user = xstrdup(user);
 245                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 246                         authctxt->valid = 1;
 247                         debug2("input_userauth_request: setting up authctxt for %s", user);
 248                 } else {
 249                         logit("input_userauth_request: invalid user %s", user);
 250                         authctxt->pw = fakepw();
 251 #ifdef SSH_AUDIT_EVENTS
 252                         PRIVSEP(audit_event(SSH_INVALID_USER));
 253 #endif
 254                 }
 255 #ifdef USE_PAM
 256                 if (options.use_pam)
 257                         PRIVSEP(start_pam(authctxt));
 258 #endif
 259                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 260                     use_privsep ? " [net]" : "");
 261                 authctxt->service = xstrdup(service);
 262                 authctxt->style = style ? xstrdup(style) : NULL;
 263                 if (use_privsep)
 264                         mm_inform_authserv(service, style);
 265                 userauth_banner();
 266         } else if (strcmp(user, authctxt->user) != 0 ||
 267             strcmp(service, authctxt->service) != 0) {
 268                 packet_disconnect("Change of username or service not allowed: "
 269                     "(%s,%s) -> (%s,%s)",
 270                     authctxt->user, authctxt->service, user, service);
 271         }
 272
 273 #ifdef HAVE_LOGIN_CAP
 274         if (authctxt->pw != NULL) {
 275                 lc = login_getpwclass(authctxt->pw);
 276                 if (lc == NULL)
 277                         lc = login_getclassbyname(NULL, authctxt->pw);
 278                 if (!auth_hostok(lc, from_host, from_ip)) {
 279                         logit("Denied connection for %.200s from %.200s [%.200s].",
 280                             authctxt->pw->pw_name, from_host, from_ip);
 281                         packet_disconnect("Sorry, you are not allowed to connect.");
 282                 }
 283                 if (!auth_timeok(lc, time(NULL))) {
 284                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 285                             authctxt->pw->pw_name, from_host);
 286                         packet_disconnect("Logins not available right now.");
 287                 }
 288                 login_close(lc);
 289                 lc = NULL;
 290         }
 291 #endif  /* HAVE_LOGIN_CAP */
 292
 293         /* reset state */
 294         auth2_challenge_stop(authctxt);
 295 #ifdef JPAKE
 296         auth2_jpake_stop(authctxt);
 297 #endif
 298
 299 #ifdef GSSAPI
 300         /* XXX move to auth2_gssapi_stop() */
 301         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 302         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 303 #endif
 304
 305         authctxt->postponed = 0;
 306
 307         /* try to authenticate user */
 308         m = authmethod_lookup(method);
 309         if (m != NULL && authctxt->failures < options.max_authtries) {
 310                 debug2("input_userauth_request: try method %s", method);
 311                 authenticated = m->userauth(authctxt);
 312         }
 313         userauth_finish(authctxt, authenticated, method);
 314
 315         xfree(service);
 316         xfree(user);
 317         xfree(method);
 318 }
 319
 320 void
 321 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 322 {
 323         char *methods;
 324
 325         if (!authctxt->valid && authenticated)
 326                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 327                     authctxt->user);
 328
 329         /* Special handling for root */
 330         if (authenticated && authctxt->pw->pw_uid == 0 &&
 331             !auth_root_allowed(method)) {
 332                 authenticated = 0;
 333 #ifdef SSH_AUDIT_EVENTS
 334                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 335 #endif
 336         }
 337
 338 #ifdef USE_PAM
 339         if (options.use_pam && authenticated) {
 340                 if (!PRIVSEP(do_pam_account())) {
 341                         /* if PAM returned a message, send it to the user */
 342                         if (buffer_len(&loginmsg) > 0) {
 343                                 buffer_append(&loginmsg, "\0", 1);
 344                                 userauth_send_banner(buffer_ptr(&loginmsg));
 345                                 packet_write_wait();
 346                         }
 347                         fatal("Access denied for user %s by PAM account "
 348                             "configuration", authctxt->user);
 349                 }
 350         }
 351 #endif
 352
 353 #ifdef _UNICOS
 354         if (authenticated && cray_access_denied(authctxt->user)) {
 355                 authenticated = 0;
 356                 fatal("Access denied for user %s.",authctxt->user);
 357         }
 358 #endif /* _UNICOS */
 359
 360         /* Log before sending the reply */
 361         auth_log(authctxt, authenticated, method, " ssh2");
 362
 363         if (authctxt->postponed)
 364                 return;
 365
 366         /* XXX todo: check if multiple auth methods are needed */
 367         if (authenticated == 1) {
 368                 /* turn off userauth */
 369                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 370                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 371                 packet_send();
 372                 packet_write_wait();
 373                 /* now we can break out */
 374                 authctxt->success = 1;
 375         } else {
 376
 377                 /* Allow initial try of "none" auth without failure penalty */
 378                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 379                         authctxt->failures++;
 380                 if (authctxt->failures >= options.max_authtries) {
 381 #ifdef SSH_AUDIT_EVENTS
 382                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 383 #endif
 384                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 385                 }
 386                 methods = authmethods_get();
 387                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 388                 packet_put_cstring(methods);
 389                 packet_put_char(0);     /* XXX partial success, unused */
 390                 packet_send();
 391                 packet_write_wait();
 392                 xfree(methods);
 393         }
 394 }
 395
 396 static char *
 397 authmethods_get(void)
 398 {
 399         Buffer b;
 400         char *list;
 401         int i;
 402
 403         buffer_init(&b);
 404         for (i = 0; authmethods[i] != NULL; i++) {
 405                 if (strcmp(authmethods[i]->name, "none") == 0)
 406                         continue;
 407                 if (authmethods[i]->enabled != NULL &&
 408                     *(authmethods[i]->enabled) != 0) {
 409                         if (buffer_len(&b) > 0)
 410                                 buffer_append(&b, ",", 1);
 411                         buffer_append(&b, authmethods[i]->name,
 412                             strlen(authmethods[i]->name));
 413                 }
 414         }
 415         buffer_append(&b, "\0", 1);
 416         list = xstrdup(buffer_ptr(&b));
 417         buffer_free(&b);
 418         return list;
 419 }
 420
 421 static Authmethod *
 422 authmethod_lookup(const char *name)
 423 {
 424         int i;
 425
 426         if (name != NULL)
 427                 for (i = 0; authmethods[i] != NULL; i++)
 428                         if (authmethods[i]->enabled != NULL &&
 429                             *(authmethods[i]->enabled) != 0 &&
 430                             strcmp(name, authmethods[i]->name) == 0)
 431                                 return authmethods[i];
 432         debug2("Unrecognized authentication method name: %s",
 433             name ? name : "NULL");
 434         return NULL;
 435 }
 436