crypto/openssh-5/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
  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 "atomicio.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
  53 #ifdef GSSAPI
  54 #include "ssh-gss.h"
  55 #endif
  56 #include "monitor_wrap.h"
  57
  58 /* import */
  59 extern ServerOptions options;
  60 extern u_char *session_id2;
  61 extern u_int session_id2_len;
  62 extern Buffer loginmsg;
  63
  64 /* methods */
  65
  66 extern Authmethod method_none;
  67 extern Authmethod method_pubkey;
  68 extern Authmethod method_passwd;
  69 extern Authmethod method_kbdint;
  70 extern Authmethod method_hostbased;
  71 #ifdef GSSAPI
  72 extern Authmethod method_gssapi;
  73 #endif
  74
  75 Authmethod *authmethods[] = {
  76         &method_none,
  77         &method_pubkey,
  78 #ifdef GSSAPI
  79         &method_gssapi,
  80 #endif
  81         &method_passwd,
  82         &method_kbdint,
  83         &method_hostbased,
  84         NULL
  85 };
  86
  87 /* protocol */
  88
  89 static void input_service_request(int, u_int32_t, void *);
  90 static void input_userauth_request(int, u_int32_t, void *);
  91
  92 /* helper */
  93 static Authmethod *authmethod_lookup(const char *);
  94 static char *authmethods_get(void);
  95
  96 char *
  97 auth2_read_banner(void)
  98 {
  99         struct stat st;
 100         char *banner = NULL;
 101         size_t len, n;
 102         int fd;
 103
 104         if ((fd = open(options.banner, O_RDONLY)) == -1)
 105                 return (NULL);
 106         if (fstat(fd, &st) == -1) {
 107                 close(fd);
 108                 return (NULL);
 109         }
 110         if (st.st_size > 1*1024*1024) {
 111                 close(fd);
 112                 return (NULL);
 113         }
 114
 115         len = (size_t)st.st_size;               /* truncate */
 116         banner = xmalloc(len + 1);
 117         n = atomicio(read, fd, banner, len);
 118         close(fd);
 119
 120         if (n != len) {
 121                 xfree(banner);
 122                 return (NULL);
 123         }
 124         banner[n] = '\0';
 125
 126         return (banner);
 127 }
 128
 129 void
 130 userauth_send_banner(const char *msg)
 131 {
 132         if (datafellows & SSH_BUG_BANNER)
 133                 return;
 134
 135         packet_start(SSH2_MSG_USERAUTH_BANNER);
 136         packet_put_cstring(msg);
 137         packet_put_cstring("");         /* language, unused */
 138         packet_send();
 139         debug("%s: sent", __func__);
 140 }
 141
 142 static void
 143 userauth_banner(void)
 144 {
 145         char *banner = NULL;
 146
 147         if (options.banner == NULL ||
 148             strcasecmp(options.banner, "none") == 0 ||
 149             (datafellows & SSH_BUG_BANNER) != 0)
 150                 return;
 151
 152         if ((banner = PRIVSEP(auth2_read_banner())) == NULL)
 153                 goto done;
 154         userauth_send_banner(banner);
 155
 156 done:
 157         if (banner)
 158                 xfree(banner);
 159 }
 160
 161 /*
 162  * loop until authctxt->success == TRUE
 163  */
 164 void
 165 do_authentication2(Authctxt *authctxt)
 166 {
 167         dispatch_init(&dispatch_protocol_error);
 168         dispatch_set(SSH2_MSG_SERVICE_REQUEST, &input_service_request);
 169         dispatch_run(DISPATCH_BLOCK, &authctxt->success, authctxt);
 170 }
 171
 172 /*ARGSUSED*/
 173 static void
 174 input_service_request(int type, u_int32_t seq, void *ctxt)
 175 {
 176         Authctxt *authctxt = ctxt;
 177         u_int len;
 178         int acceptit = 0;
 179         char *service = packet_get_string(&len);
 180         packet_check_eom();
 181
 182         if (authctxt == NULL)
 183                 fatal("input_service_request: no authctxt");
 184
 185         if (strcmp(service, "ssh-userauth") == 0) {
 186                 if (!authctxt->success) {
 187                         acceptit = 1;
 188                         /* now we can handle user-auth requests */
 189                         dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &input_userauth_request);
 190                 }
 191         }
 192         /* XXX all other service requests are denied */
 193
 194         if (acceptit) {
 195                 packet_start(SSH2_MSG_SERVICE_ACCEPT);
 196                 packet_put_cstring(service);
 197                 packet_send();
 198                 packet_write_wait();
 199         } else {
 200                 debug("bad service request %s", service);
 201                 packet_disconnect("bad service request %s", service);
 202         }
 203         xfree(service);
 204 }
 205
 206 /*ARGSUSED*/
 207 static void
 208 input_userauth_request(int type, u_int32_t seq, void *ctxt)
 209 {
 210         Authctxt *authctxt = ctxt;
 211         Authmethod *m = NULL;
 212         char *user, *service, *method, *style = NULL;
 213         int authenticated = 0;
 214
 215         if (authctxt == NULL)
 216                 fatal("input_userauth_request: no authctxt");
 217
 218         user = packet_get_string(NULL);
 219         service = packet_get_string(NULL);
 220         method = packet_get_string(NULL);
 221         debug("userauth-request for user %s service %s method %s", user, service, method);
 222         debug("attempt %d failures %d", authctxt->attempt, authctxt->failures);
 223
 224         if ((style = strchr(user, ':')) != NULL)
 225                 *style++ = 0;
 226
 227         if (authctxt->attempt++ == 0) {
 228                 /* setup auth context */
 229                 authctxt->pw = PRIVSEP(getpwnamallow(user));
 230                 authctxt->user = xstrdup(user);
 231                 if (authctxt->pw && strcmp(service, "ssh-connection")==0) {
 232                         authctxt->valid = 1;
 233                         debug2("input_userauth_request: setting up authctxt for %s", user);
 234                 } else {
 235                         logit("input_userauth_request: invalid user %s", user);
 236                         authctxt->pw = fakepw();
 237 #ifdef SSH_AUDIT_EVENTS
 238                         PRIVSEP(audit_event(SSH_INVALID_USER));
 239 #endif
 240                 }
 241 #ifdef USE_PAM
 242                 if (options.use_pam)
 243                         PRIVSEP(start_pam(authctxt));
 244 #endif
 245                 setproctitle("%s%s", authctxt->valid ? user : "unknown",
 246                     use_privsep ? " [net]" : "");
 247                 authctxt->service = xstrdup(service);
 248                 authctxt->style = style ? xstrdup(style) : NULL;
 249                 if (use_privsep)
 250                         mm_inform_authserv(service, style);
 251                 userauth_banner();
 252         } else if (strcmp(user, authctxt->user) != 0 ||
 253             strcmp(service, authctxt->service) != 0) {
 254                 packet_disconnect("Change of username or service not allowed: "
 255                     "(%s,%s) -> (%s,%s)",
 256                     authctxt->user, authctxt->service, user, service);
 257         }
 258         /* reset state */
 259         auth2_challenge_stop(authctxt);
 260
 261 #ifdef GSSAPI
 262         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_TOKEN, NULL);
 263         dispatch_set(SSH2_MSG_USERAUTH_GSSAPI_EXCHANGE_COMPLETE, NULL);
 264 #endif
 265
 266         authctxt->postponed = 0;
 267
 268         /* try to authenticate user */
 269         m = authmethod_lookup(method);
 270         if (m != NULL && authctxt->failures < options.max_authtries) {
 271                 debug2("input_userauth_request: try method %s", method);
 272                 authenticated = m->userauth(authctxt);
 273         }
 274         userauth_finish(authctxt, authenticated, method);
 275
 276         xfree(service);
 277         xfree(user);
 278         xfree(method);
 279 }
 280
 281 void
 282 userauth_finish(Authctxt *authctxt, int authenticated, char *method)
 283 {
 284         char *methods;
 285
 286         if (!authctxt->valid && authenticated)
 287                 fatal("INTERNAL ERROR: authenticated invalid user %s",
 288                     authctxt->user);
 289
 290         /* Special handling for root */
 291         if (authenticated && authctxt->pw->pw_uid == 0 &&
 292             !auth_root_allowed(method)) {
 293                 authenticated = 0;
 294 #ifdef SSH_AUDIT_EVENTS
 295                 PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
 296 #endif
 297         }
 298
 299 #ifdef USE_PAM
 300         if (options.use_pam && authenticated) {
 301                 if (!PRIVSEP(do_pam_account())) {
 302                         /* if PAM returned a message, send it to the user */
 303                         if (buffer_len(&loginmsg) > 0) {
 304                                 buffer_append(&loginmsg, "\0", 1);
 305                                 userauth_send_banner(buffer_ptr(&loginmsg));
 306                                 packet_write_wait();
 307                         }
 308                         fatal("Access denied for user %s by PAM account "
 309                             "configuration", authctxt->user);
 310                 }
 311         }
 312 #endif
 313
 314 #ifdef _UNICOS
 315         if (authenticated && cray_access_denied(authctxt->user)) {
 316                 authenticated = 0;
 317                 fatal("Access denied for user %s.",authctxt->user);
 318         }
 319 #endif /* _UNICOS */
 320
 321         /* Log before sending the reply */
 322         auth_log(authctxt, authenticated, method, " ssh2");
 323
 324         if (authctxt->postponed)
 325                 return;
 326
 327         /* XXX todo: check if multiple auth methods are needed */
 328         if (authenticated == 1) {
 329                 /* turn off userauth */
 330                 dispatch_set(SSH2_MSG_USERAUTH_REQUEST, &dispatch_protocol_ignore);
 331                 packet_start(SSH2_MSG_USERAUTH_SUCCESS);
 332                 packet_send();
 333                 packet_write_wait();
 334                 /* now we can break out */
 335                 authctxt->success = 1;
 336         } else {
 337
 338                 /* Allow initial try of "none" auth without failure penalty */
 339                 if (authctxt->attempt > 1 || strcmp(method, "none") != 0)
 340                         authctxt->failures++;
 341                 if (authctxt->failures >= options.max_authtries) {
 342 #ifdef SSH_AUDIT_EVENTS
 343                         PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
 344 #endif
 345                         packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
 346                 }
 347                 methods = authmethods_get();
 348                 packet_start(SSH2_MSG_USERAUTH_FAILURE);
 349                 packet_put_cstring(methods);
 350                 packet_put_char(0);     /* XXX partial success, unused */
 351                 packet_send();
 352                 packet_write_wait();
 353                 xfree(methods);
 354         }
 355 }
 356
 357 static char *
 358 authmethods_get(void)
 359 {
 360         Buffer b;
 361         char *list;
 362         int i;
 363
 364         buffer_init(&b);
 365         for (i = 0; authmethods[i] != NULL; i++) {
 366                 if (strcmp(authmethods[i]->name, "none") == 0)
 367                         continue;
 368                 if (authmethods[i]->enabled != NULL &&
 369                     *(authmethods[i]->enabled) != 0) {
 370                         if (buffer_len(&b) > 0)
 371                                 buffer_append(&b, ",", 1);
 372                         buffer_append(&b, authmethods[i]->name,
 373                             strlen(authmethods[i]->name));
 374                 }
 375         }
 376         buffer_append(&b, "\0", 1);
 377         list = xstrdup(buffer_ptr(&b));
 378         buffer_free(&b);
 379         return list;
 380 }
 381
 382 static Authmethod *
 383 authmethod_lookup(const char *name)
 384 {
 385         int i;
 386
 387         if (name != NULL)
 388                 for (i = 0; authmethods[i] != NULL; i++)
 389                         if (authmethods[i]->enabled != NULL &&
 390                             *(authmethods[i]->enabled) != 0 &&
 391                             strcmp(name, authmethods[i]->name) == 0)
 392                                 return authmethods[i];
 393         debug2("Unrecognized authentication method name: %s",
 394             name ? name : "NULL");
 395         return NULL;
 396 }
 397