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 __RCSID("$FreeBSD$");
  28
  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 "xmalloc.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 #include "canohost.h"
  54
  55 #ifdef GSSAPI
  56 #include "ssh-gss.h"
  57 #endif
  58 #include "monitor_wrap.h"
  59
  60 /* import */
  61 extern ServerOptions options;
  62 extern u_char *session_id2;
  63 extern u_int session_id2_len;
  64 extern Buffer loginmsg;
  65
  66 /* methods */
  67
  68 extern Authmethod method_none;
  69 extern Authmethod method_pubkey;
  70 extern Authmethod method_passwd;
  71 extern Authmethod method_kbdint;
  72 extern Authmethod method_hostbased;
  73 #ifdef GSSAPI
  74 extern Authmethod method_gssapi;
  75 #endif
  76
  77 Authmethod *authmethods[] = {
  78         &method_none,
  79         &method_pubkey,
  80 #ifdef GSSAPI
  81         &method_gssapi,
  82 #endif
  83         &method_passwd,
  84         &method_kbdint,
  85         &method_hostbased,
  86         NULL
  87 };
  88
  89 /* protocol */
  90
  91 static void input_service_request(int, u_int32_t, void *);
  92 static void input_userauth_request(int, u_int32_t, void *);
  93
  94 /* helper */
  95 static Authmethod *authmethod_lookup(const char *);
  96 static char *authmethods_get(void);
  97
  98 char *
  99 auth2_read_banner(void)
 100 {
 101         struct stat st;
 102         char *banner = NULL;
 103         size_t len, n;
 104         int fd;
 105
 106         if ((fd = open(options.banner, O_RDONLY)) == -1)
 107                 return (NULL);
 108         if (fstat(fd, &st) == -1) {
 109                 close(fd);
 110                 return (NULL);
 111         }
 112         if (st.st_size > 1*1024*1024) {
 113                 close(fd);
 114                 return (NULL);
 115         }
 116
 117         len = (size_t)st.st_size;               /* truncate */
 118         banner = xmalloc(len + 1);
 119         n = atomicio(read, fd, banner, len);
 120         close(fd);
 121
 122         if (n != len) {
 123                 xfree(banner);
 124                 return (NULL);
 125         }
 126         banner[n] = '\0';
 127
 128         return (banner);
 129 }
 130
 131 void
 132 userauth_send_banner(const char *msg)
 133 {
 134         if (datafellows & SSH_BUG_BANNER)
 135                 return;
 136
 137         packet_start(SSH2_MSG_USERAUTH_BANNER);
 138         packet_put_cstring(msg);
 139         packet_put_cstring("");         /* language, unused */
 140         packet_send();
 141         debug("%s: sent", __func__);
 142 }
 143
 144 static void
 145 userauth_banner(void)
 146 {
 147         char *banner = NULL;
 148
 149         if (options.banner == NULL ||
 150             strcasecmp(options.banner, "none") == 0 ||
 151             (datafellows & SSH_BUG_BANNER) != 0)
 152                 return;
 153
 154         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 155                 goto done;
 156         userauth_send_banner(banner);
 157
 158 done:
 159         if (banner)
 160                 xfree(banner);
 161 }
 162
 163 /*
 164  * loop until authctxt->success == TRUE
 165  */
 166 void
 167 do_authentication2(Authctxt *authctxt)
 168 {
 169         dispatch_init(&dispatch_protocol_error);
 170         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 171         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 172 }
 173
 174 /*ARGSUSED*/
 175 static void
 176 input_service_request(int type, u_int32_t seq, void *ctxt)
 177 {
 178         Authctxt *authctxt = ctxt;
 179         u_int len;
 180         int acceptit = 0;
 181         char *service = packet_get_string(&len);
 182         packet_check_eom();
 183
 184         if (authctxt == NULL)
 185                 fatal("input_service_request: no authctxt");
 186
 187         if (strcmp(service, "ssh-userauth") == 0) {
 188                 if (!authctxt->success) {
 189                         acceptit = 1;
 190                         /* now we can handle user-auth requests */
 191                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 192                 }
 193         }
 194         /* XXX all other service requests are denied */
 195
 196         if (acceptit) {
 197                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 198                 packet_put_cstring(service);
 199                 packet_send();
 200                 packet_write_wait();
 201         } else {
 202                 debug("bad service request %s", service);
 203                 packet_disconnect("bad service request %s", service);
 204         }
 205         xfree(service);
 206 }
 207
 208 /*ARGSUSED*/
 209 static void
 210 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 211 {
 212         Authctxt *authctxt = ctxt;
 213         Authmethod *m = NULL;
 214         char *user, *service, *method, *style = NULL;
 215         int authenticated = 0;
 216 #ifdef HAVE_LOGIN_CAP
 217         login_cap_t *lc;
 218         const char *from_host, *from_ip;
 219
 220         from_host = get_canonical_hostname(options.use_dns);
 221         from_ip = get_remote_ipaddr();
 222 #endif
 223
 224         if (authctxt == NULL)
 225                 fatal("input_userauth_request: no authctxt");
 226
 227         user = packet_get_string(NULL);
 228         service = packet_get_string(NULL);
 229         method = packet_get_string(NULL);
 230         debug("userauth-request for user %s service %s method %s", user, service, method);
 231         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 232
 233         if ((style = strchr(user, ':')) != NULL)
 234                 *style++ = 0;
 235
 236         if (authctxt->attempt++ == 0) {
 237                 /* setup auth context */
 238                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 239                 authctxt->user = xstrdup(user);
 240                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 241                         authctxt->valid = 1;
 242                         debug2("input_userauth_request: setting up authctxt for %s", user);
 243                 } else {
 244                         logit("input_userauth_request: invalid user %s", user);
 245                         authctxt->pw = fakepw();
 246 #ifdef SSH_AUDIT_EVENTS
 247                         PRIVSEP(audit_event(SSH_INVALID_USER));
 248 #endif
 249                 }
 250 #ifdef USE_PAM
 251                 if (options.use_pam)
 252                         PRIVSEP(start_pam(authctxt));
 253 #endif
 254                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 255                     use_privsep ? " [net]" : "");
 256                 authctxt->service = xstrdup(service);
 257                 authctxt->style = style ? xstrdup(style) : NULL;
 258                 if (use_privsep)
 259                         mm_inform_authserv(service, style);
 260                 userauth_banner();
 261         } else if (strcmp(user, authctxt->user) != 0 ||
 262             strcmp(service, authctxt->service) != 0) {
 263                 packet_disconnect("Change of username or service not allowed: "
 264                     "(%s,%s) -> (%s,%s)",
 265                     authctxt->user, authctxt->service, user, service);
 266         }
 267
 268 #ifdef HAVE_LOGIN_CAP
 269         if (authctxt->pw != NULL) {
 270                 lc = login_getpwclass(authctxt->pw);
 271                 if (lc == NULL)
 272                         lc = login_getclassbyname(NULL, authctxt->pw);
 273                 if (!auth_hostok(lc, from_host, from_ip)) {
 274                         logit("Denied connection for %.200s from %.200s [%.200s].",
 275                             authctxt->pw->pw_name, from_host, from_ip);
 276                         packet_disconnect("Sorry, you are not allowed to connect.");
 277                 }
 278                 if (!auth_timeok(lc, time(NULL))) {
 279                         logit("LOGIN %.200s REFUSED (TIME) FROM %.200s",
 280                             authctxt->pw->pw_name, from_host);
 281                         packet_disconnect("Logins not available right now.");
 282                 }
 283                 login_close(lc);
 284                 lc = NULL;
 285         }
 286 #endif  /* HAVE_LOGIN_CAP */
 287
 288         /* reset state */
 289         auth2_challenge_stop(authctxt);
 290
 291 #ifdef GSSAPI
 292         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 293         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 294 #endif
 295
 296         authctxt->postponed = 0;
 297
 298         /* try to authenticate user */
 299         m = authmethod_lookup(method);
 300         if (m != NULL && authctxt->failures < options.max_authtries) {
 301                 debug2("input_userauth_request: try method %s", method);
 302                 authenticated = m->userauth(authctxt);
 303         }
 304         userauth_finish(authctxt, authenticated, method);
 305
 306         xfree(service);
 307         xfree(user);
 308         xfree(method);
 309 }
 310
 311 void
 312 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 313 {
 314         char *methods;
 315
 316         if (!authctxt->valid && authenticated)
 317                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 318                     authctxt->user);
 319
 320         /* Special handling for root */
 321         if (authenticated && authctxt->pw->pw_uid == 0 &&
 322             !auth_root_allowed(method)) {
 323                 authenticated = 0;
 324 #ifdef SSH_AUDIT_EVENTS
 325                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 326 #endif
 327         }
 328
 329 #ifdef USE_PAM
 330         if (options.use_pam && authenticated) {
 331                 if (!PRIVSEP(do_pam_account())) {
 332                         /* if PAM returned a message, send it to the user */
 333                         if (buffer_len(&loginmsg) > 0) {
 334                                 buffer_append(&loginmsg, "\0", 1);
 335                                 userauth_send_banner(buffer_ptr(&loginmsg));
 336                                 packet_write_wait();
 337                         }
 338                         fatal("Access denied for user %s by PAM account "
 339                             "configuration", authctxt->user);
 340                 }
 341         }
 342 #endif
 343
 344 #ifdef _UNICOS
 345         if (authenticated && cray_access_denied(authctxt->user)) {
 346                 authenticated = 0;
 347                 fatal("Access denied for user %s.",authctxt->user);
 348         }
 349 #endif /* _UNICOS */
 350
 351         /* Log before sending the reply */
 352         auth_log(authctxt, authenticated, method, " ssh2");
 353
 354         if (authctxt->postponed)
 355                 return;
 356
 357         /* XXX todo: check if multiple auth methods are needed */
 358         if (authenticated == 1) {
 359                 /* turn off userauth */
 360                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 361                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 362                 packet_send();
 363                 packet_write_wait();
 364                 /* now we can break out */
 365                 authctxt->success = 1;
 366         } else {
 367
 368                 /* Allow initial try of "none" auth without failure penalty */
 369                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 370                         authctxt->failures++;
 371                 if (authctxt->failures >= options.max_authtries) {
 372 #ifdef SSH_AUDIT_EVENTS
 373                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 374 #endif
 375                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 376                 }
 377                 methods = authmethods_get();
 378                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 379                 packet_put_cstring(methods);
 380                 packet_put_char(0);     /* XXX partial success, unused */
 381                 packet_send();
 382                 packet_write_wait();
 383                 xfree(methods);
 384         }
 385 }
 386
 387 static char *
 388 authmethods_get(void)
 389 {
 390         Buffer b;
 391         char *list;
 392         int i;
 393
 394         buffer_init(&b);
 395         for (i = 0; authmethods[i] != NULL; i++) {
 396                 if (strcmp(authmethods[i]->name, "none") == 0)
 397                         continue;
 398                 if (authmethods[i]->enabled != NULL &&
 399                     *(authmethods[i]->enabled) != 0) {
 400                         if (buffer_len(&b) > 0)
 401                                 buffer_append(&b, ",", 1);
 402                         buffer_append(&b, authmethods[i]->name,
 403                             strlen(authmethods[i]->name));
 404                 }
 405         }
 406         buffer_append(&b, "\0", 1);
 407         list = xstrdup(buffer_ptr(&b));
 408         buffer_free(&b);
 409         return list;
 410 }
 411
 412 static Authmethod *
 413 authmethod_lookup(const char *name)
 414 {
 415         int i;
 416
 417         if (name != NULL)
 418                 for (i = 0; authmethods[i] != NULL; i++)
 419                         if (authmethods[i]->enabled != NULL &&
 420                             *(authmethods[i]->enabled) != 0 &&
 421                             strcmp(name, authmethods[i]->name) == 0)
 422                                 return authmethods[i];
 423         debug2("Unrecognized authentication method name: %s",
 424             name ? name : "NULL");
 425         return NULL;
 426 }
 427