crypto/external/bsd/openssh/dist/auth2.c

   1 /*      $NetBSD: auth2.c,v 1.1.1.2 2009/12/27 01:06:47 christos Exp $   */
   2 /* $OpenBSD: auth2.c,v 1.121 2009/06/22 05:39:28 dtucker Exp $ */
   3 /*
   4  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
   5  *
   6  * Redistribution and use in source and binary forms, with or without
   7  * modification, are permitted provided that the following conditions
   8  * are met:
   9  * 1. Redistributions of source code must retain the above copyright
  10  *    notice, this list of conditions and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  16  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  18  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  19  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  20  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  21  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  22  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  23  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  24  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  25  */
  26
  27 #include "includes.h"
  28 __RCSID("$NetBSD: auth2.c,v 1.2 2009/06/07 22:38:46 christos Exp $");
  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
  59 #include "monitor_wrap.h"
  60
  61 /* import */
  62 extern ServerOptions options;
  63 extern u_char *session_id2;
  64 extern u_int session_id2_len;
  65 extern Buffer loginmsg;
  66
  67 /* methods */
  68
  69 extern Authmethod method_none;
  70 extern Authmethod method_pubkey;
  71 extern Authmethod method_passwd;
  72 extern Authmethod method_kbdint;
  73 extern Authmethod method_hostbased;
  74 #ifdef KRB5
  75 extern Authmethod method_kerberos;
  76 #endif
  77 #ifdef GSSAPI
  78 extern Authmethod method_gssapi;
  79 #endif
  80 #ifdef JPAKE
  81 extern Authmethod method_jpake;
  82 #endif
  83
  84 static int log_flag = 0;
  85
  86 Authmethod *authmethods[] = {
  87         &method_none,
  88         &method_pubkey,
  89 #ifdef GSSAPI
  90         &method_gssapi,
  91 #endif
  92 #ifdef JPAKE
  93         &method_jpake,
  94 #endif
  95         &method_passwd,
  96         &method_kbdint,
  97         &method_hostbased,
  98 #ifdef KRB5
  99         &method_kerberos,
 100 #endif
 101         NULL
 102 };
 103
 104 /* protocol */
 105
 106 static void input_service_request(int, u_int32_t, void *);
 107 static void input_userauth_request(int, u_int32_t, void *);
 108
 109 /* helper */
 110 static Authmethod *authmethod_lookup(const char *);
 111 static char *authmethods_get(void);
 112
 113 char *
 114 auth2_read_banner(void)
 115 {
 116         struct stat st;
 117         char *banner = NULL;
 118         size_t len, n;
 119         int fd;
 120
 121         if ((fd = open(options.banner, O_RDONLY)) == -1)
 122                 return (NULL);
 123         if (fstat(fd, &st) == -1) {
 124                 close(fd);
 125                 return (NULL);
 126         }
 127         if (st.st_size > 1*1024*1024) {
 128                 close(fd);
 129                 return (NULL);
 130         }
 131
 132         len = (size_t)st.st_size;               /* truncate */
 133         banner = xmalloc(len + 1);
 134         n = atomicio(read, fd, banner, len);
 135         close(fd);
 136
 137         if (n != len) {
 138                 xfree(banner);
 139                 return (NULL);
 140         }
 141         banner[n] = '\0';
 142
 143         return (banner);
 144 }
 145
 146 void
 147 userauth_send_banner(const char *msg)
 148 {
 149         if (datafellows & SSH_BUG_BANNER)
 150                 return;
 151
 152         packet_start(SSH2_MSG_USERAUTH_BANNER);
 153         packet_put_cstring(msg);
 154         packet_put_cstring("");         /* language, unused */
 155         packet_send();
 156         debug("%s: sent", __func__);
 157 }
 158
 159 static void
 160 userauth_banner(void)
 161 {
 162         char *banner = NULL;
 163
 164         if (options.banner == NULL ||
 165             strcasecmp(options.banner, "none") == 0 ||
 166             (datafellows & SSH_BUG_BANNER) != 0)
 167                 return;
 168
 169         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 170                 goto done;
 171
 172         userauth_send_banner(banner);
 173 done:
 174         if (banner)
 175                 xfree(banner);
 176 }
 177
 178 /*
 179  * loop until authctxt->success == TRUE
 180  */
 181 void
 182 do_authentication2(Authctxt *authctxt)
 183 {
 184         dispatch_init(&dispatch_protocol_error);
 185         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 186         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 187 }
 188
 189 /*ARGSUSED*/
 190 static void
 191 input_service_request(int type, u_int32_t seq, void *ctxt)
 192 {
 193         Authctxt *authctxt = ctxt;
 194         u_int len;
 195         int acceptit = 0;
 196         char *service = packet_get_string(&len);
 197         packet_check_eom();
 198
 199         if (authctxt == NULL)
 200                 fatal("input_service_request: no authctxt");
 201
 202         if (strcmp(service, "ssh-userauth") == 0) {
 203                 if (!authctxt->success) {
 204                         acceptit = 1;
 205                         /* now we can handle user-auth requests */
 206                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 207                 }
 208         }
 209         /* XXX all other service requests are denied */
 210
 211         if (acceptit) {
 212                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 213                 packet_put_cstring(service);
 214                 packet_send();
 215                 packet_write_wait();
 216         } else {
 217                 debug("bad service request %s", service);
 218                 packet_disconnect("bad service request %s", service);
 219         }
 220         xfree(service);
 221 }
 222
 223 /*ARGSUSED*/
 224 static void
 225 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 226 {
 227         Authctxt *authctxt = ctxt;
 228         Authmethod *m = NULL;
 229         char *user, *service, *method, *style = NULL;
 230         int authenticated = 0;
 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                 }
 260 #ifdef USE_PAM
 261                 if (options.use_pam)
 262                         PRIVSEP(start_pam(authctxt));
 263 #endif
 264                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 265                     use_privsep ? " [net]" : "");
 266                 authctxt->service = xstrdup(service);
 267                 authctxt->style = style ? xstrdup(style) : NULL;
 268                 if (use_privsep)
 269                         mm_inform_authserv(service, style);
 270                 userauth_banner();
 271         } else if (strcmp(user, authctxt->user) != 0 ||
 272             strcmp(service, authctxt->service) != 0) {
 273                 packet_disconnect("Change of username or service not allowed: "
 274                     "(%s,%s) -> (%s,%s)",
 275                     authctxt->user, authctxt->service, user, service);
 276         }
 277         /* reset state */
 278         auth2_challenge_stop(authctxt);
 279 #ifdef JPAKE
 280         auth2_jpake_stop(authctxt);
 281 #endif
 282
 283 #ifdef GSSAPI
 284         /* XXX move to auth2_gssapi_stop() */
 285         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 286         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 287 #endif
 288
 289         authctxt->postponed = 0;
 290
 291         /* try to authenticate user */
 292         m = authmethod_lookup(method);
 293         if (m != NULL && authctxt->failures < options.max_authtries) {
 294                 debug2("input_userauth_request: try method %s", method);
 295                 authenticated = m->userauth(authctxt);
 296         }
 297         userauth_finish(authctxt, authenticated, method);
 298
 299         xfree(service);
 300         xfree(user);
 301         xfree(method);
 302 }
 303
 304 void
 305 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 306 {
 307         char *methods;
 308
 309         if (!authctxt->valid && authenticated)
 310                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 311                     authctxt->user);
 312
 313         /* Special handling for root */
 314         if (authenticated && authctxt->pw->pw_uid == 0 &&
 315             !auth_root_allowed(method)) {
 316                 authenticated = 0;
 317 #ifdef SSH_AUDIT_EVENTS
 318                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 319 #endif
 320         }
 321
 322 #ifdef USE_PAM
 323         if (options.use_pam && authenticated) {
 324                 if (!PRIVSEP(do_pam_account())) {
 325                         /* if PAM returned a message, send it to the user */
 326                         if (buffer_len(&loginmsg) > 0) {
 327                                 buffer_append(&loginmsg, "\0", 1);
 328                                 userauth_send_banner(buffer_ptr(&loginmsg));
 329                                 packet_write_wait();
 330                         }
 331                         fatal("Access denied for user %s by PAM account "
 332                            "configuration", authctxt->user);
 333                 }
 334         }
 335 #endif
 336
 337         /* Log before sending the reply */
 338         auth_log(authctxt, authenticated, method, " ssh2");
 339
 340         if (authctxt->postponed)
 341                 return;
 342
 343         /* XXX todo: check if multiple auth methods are needed */
 344         if (authenticated == 1) {
 345                 /* turn off userauth */
 346                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 347                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 348                 packet_send();
 349                 packet_write_wait();
 350                 /* now we can break out */
 351                 authctxt->success = 1;
 352         } else {
 353                 /* Allow initial try of "none" auth without failure penalty */
 354                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 355                         authctxt->failures++;
 356                 if (authctxt->failures >= options.max_authtries) {
 357                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 358 #ifdef SSH_AUDIT_EVENTS
 359                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 360 #endif
 361                 }
 362                 methods = authmethods_get();
 363                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 364                 packet_put_cstring(methods);
 365                 packet_put_char(0);     /* XXX partial success, unused */
 366                 packet_send();
 367                 packet_write_wait();
 368                 xfree(methods);
 369         }
 370 }
 371
 372 static char *
 373 authmethods_get(void)
 374 {
 375         Buffer b;
 376         char *list;
 377         int i;
 378
 379         buffer_init(&b);
 380         for (i = 0; authmethods[i] != NULL; i++) {
 381                 if (strcmp(authmethods[i]->name, "none") == 0)
 382                         continue;
 383                 if (authmethods[i]->enabled != NULL &&
 384                     *(authmethods[i]->enabled) != 0) {
 385                         if (buffer_len(&b) > 0)
 386                                 buffer_append(&b, ",", 1);
 387                         buffer_append(&b, authmethods[i]->name,
 388                             strlen(authmethods[i]->name));
 389                 }
 390         }
 391         buffer_append(&b, "\0", 1);
 392         list = xstrdup(buffer_ptr(&b));
 393         buffer_free(&b);
 394         return list;
 395 }
 396
 397 static Authmethod *
 398 authmethod_lookup(const char *name)
 399 {
 400         int i;
 401
 402         if (name != NULL)
 403                 for (i = 0; authmethods[i] != NULL; i++)
 404                         if (authmethods[i]->enabled != NULL &&
 405                             *(authmethods[i]->enabled) != 0 &&
 406                             strcmp(name, authmethods[i]->name) == 0)
 407                                 return authmethods[i];
 408         debug2("Unrecognized authentication method name: %s",
 409             name ? name : "NULL");
 410         return NULL;
 411 }
 412