crypto/openssh/auth2.c

   1 /* $OpenBSD: auth2.c,v 1.124 2011/12/07 05:44:38 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 "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 <= 0 || 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_cstring(&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_cstring(NULL);
 236         service = packet_get_cstring(NULL);
 237         method = packet_get_cstring(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         authctxt->server_caused_failure = 0;
 315
 316         /* try to authenticate user */
 317         m = authmethod_lookup(method);
 318         if (m != NULL && authctxt->failures < options.max_authtries) {
 319                 debug2("input_userauth_request: try method %s", method);
 320                 authenticated = m->userauth(authctxt);
 321         }
 322         userauth_finish(authctxt, authenticated, method);
 323
 324         xfree(service);
 325         xfree(user);
 326         xfree(method);
 327 }
 328
 329 void
 330 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 331 {
 332         char *methods;
 333
 334         if (!authctxt->valid && authenticated)
 335                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 336                     authctxt->user);
 337
 338         /* Special handling for root */
 339         if (authenticated && authctxt->pw->pw_uid == 0 &&
 340             !auth_root_allowed(method)) {
 341                 authenticated = 0;
 342 #ifdef SSH_AUDIT_EVENTS
 343                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 344 #endif
 345         }
 346
 347 #ifdef USE_PAM
 348         if (options.use_pam && authenticated) {
 349                 if (!PRIVSEP(do_pam_account())) {
 350                         /* if PAM returned a message, send it to the user */
 351                         if (buffer_len(&loginmsg) > 0) {
 352                                 buffer_append(&loginmsg, "\0", 1);
 353                                 userauth_send_banner(buffer_ptr(&loginmsg));
 354                                 packet_write_wait();
 355                         }
 356                         fatal("Access denied for user %s by PAM account "
 357                             "configuration", authctxt->user);
 358                 }
 359         }
 360 #endif
 361
 362 #ifdef _UNICOS
 363         if (authenticated && cray_access_denied(authctxt->user)) {
 364                 authenticated = 0;
 365                 fatal("Access denied for user %s.",authctxt->user);
 366         }
 367 #endif /* _UNICOS */
 368
 369         /* Log before sending the reply */
 370         auth_log(authctxt, authenticated, method, " ssh2");
 371
 372         if (authctxt->postponed)
 373                 return;
 374
 375         /* XXX todo: check if multiple auth methods are needed */
 376         if (authenticated == 1) {
 377                 /* turn off userauth */
 378                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 379                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 380                 packet_send();
 381                 packet_write_wait();
 382                 /* now we can break out */
 383                 authctxt->success = 1;
 384         } else {
 385
 386                 /* Allow initial try of "none" auth without failure penalty */
 387                 if (!authctxt->server_caused_failure &&
 388                     (authctxt->attempt > 1 || strcmp(method, "none") != 0))
 389                         authctxt->failures++;
 390                 if (authctxt->failures >= options.max_authtries) {
 391 #ifdef SSH_AUDIT_EVENTS
 392                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 393 #endif
 394                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 395                 }
 396                 methods = authmethods_get();
 397                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 398                 packet_put_cstring(methods);
 399                 packet_put_char(0);     /* XXX partial success, unused */
 400                 packet_send();
 401                 packet_write_wait();
 402                 xfree(methods);
 403         }
 404 }
 405
 406 static char *
 407 authmethods_get(void)
 408 {
 409         Buffer b;
 410         char *list;
 411         int i;
 412
 413         buffer_init(&b);
 414         for (i = 0; authmethods[i] != NULL; i++) {
 415                 if (strcmp(authmethods[i]->name, "none") == 0)
 416                         continue;
 417                 if (authmethods[i]->enabled != NULL &&
 418                     *(authmethods[i]->enabled) != 0) {
 419                         if (buffer_len(&b) > 0)
 420                                 buffer_append(&b, ",", 1);
 421                         buffer_append(&b, authmethods[i]->name,
 422                             strlen(authmethods[i]->name));
 423                 }
 424         }
 425         buffer_append(&b, "\0", 1);
 426         list = xstrdup(buffer_ptr(&b));
 427         buffer_free(&b);
 428         return list;
 429 }
 430
 431 static Authmethod *
 432 authmethod_lookup(const char *name)
 433 {
 434         int i;
 435
 436         if (name != NULL)
 437                 for (i = 0; authmethods[i] != NULL; i++)
 438                         if (authmethods[i]->enabled != NULL &&
 439                             *(authmethods[i]->enabled) != 0 &&
 440                             strcmp(name, authmethods[i]->name) == 0)
 441                                 return authmethods[i];
 442         debug2("Unrecognized authentication method name: %s",
 443             name ? name : "NULL");
 444         return NULL;
 445 }
 446