auth-pam.c

   1 /*-
   2  * Copyright (c) 2002 Networks Associates Technology, Inc.
   3  * All rights reserved.
   4  *
   5  * This software was developed for the FreeBSD Project by ThinkSec AS and
   6  * NAI Labs, the Security Research Division of Network Associates, Inc.
   7  * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
   8  * DARPA CHATS research program.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31 /*
  32  * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org>
  33  * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au>
  34  *
  35  * Permission to use, copy, modify, and distribute this software for any
  36  * purpose with or without fee is hereby granted, provided that the above
  37  * copyright notice and this permission notice appear in all copies.
  38  *
  39  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  40  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  41  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  42  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  43  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  44  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  45  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  46  */
  47
  48 /* Based on $FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des Exp $ */
  49 #include "includes.h"
  50
  51 #include <sys/types.h>
  52 #include <sys/stat.h>
  53 #include <sys/wait.h>
  54 #include <signal.h>
  55
  56 #ifdef USE_PAM
  57 #if defined(HAVE_SECURITY_PAM_APPL_H)
  58 #include <security/pam_appl.h>
  59 #elif defined (HAVE_PAM_PAM_APPL_H)
  60 #include <pam/pam_appl.h>
  61 #endif
  62
  63 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
  64 #ifdef PAM_SUN_CODEBASE
  65 # define sshpam_const           /* Solaris, HP-UX, AIX */
  66 #else
  67 # define sshpam_const   const   /* LinuxPAM, OpenPAM */
  68 #endif
  69
  70 #include "auth.h"
  71 #include "auth-pam.h"
  72 #include "buffer.h"
  73 #include "bufaux.h"
  74 #include "canohost.h"
  75 #include "log.h"
  76 #include "monitor_wrap.h"
  77 #include "msg.h"
  78 #include "packet.h"
  79 #include "misc.h"
  80 #include "servconf.h"
  81 #include "ssh2.h"
  82 #include "xmalloc.h"
  83 #include "auth-options.h"
  84
  85 extern ServerOptions options;
  86 extern Buffer loginmsg;
  87 extern int compat20;
  88 extern u_int utmp_len;
  89
  90 /* so we don't silently change behaviour */
  91 #ifdef USE_POSIX_THREADS
  92 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
  93 #endif
  94
  95 /*
  96  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
  97  * and generally a bad idea.  Use at own risk and do not expect support if
  98  * this breaks.
  99  */
 100 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
 101 #include <pthread.h>
 102 /*
 103  * Avoid namespace clash when *not* using pthreads for systems *with*
 104  * pthreads, which unconditionally define pthread_t via sys/types.h
 105  * (e.g. Linux)
 106  */
 107 typedef pthread_t sp_pthread_t;
 108 #else
 109 typedef pid_t sp_pthread_t;
 110 #endif
 111
 112 struct pam_ctxt {
 113         sp_pthread_t     pam_thread;
 114         int              pam_psock;
 115         int              pam_csock;
 116         int              pam_done;
 117 };
 118
 119 static void sshpam_free_ctx(void *);
 120 static struct pam_ctxt *cleanup_ctxt;
 121
 122 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 123 /*
 124  * Simulate threads with processes.
 125  */
 126
 127 static int sshpam_thread_status = -1;
 128 static mysig_t sshpam_oldsig;
 129
 130 static void
 131 sshpam_sigchld_handler(int sig)
 132 {
 133         signal(SIGCHLD, SIG_DFL);
 134         if (cleanup_ctxt == NULL)
 135                 return; /* handler called after PAM cleanup, shouldn't happen */
 136         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 137             <= 0) {
 138                 /* PAM thread has not exitted, privsep slave must have */
 139                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 140                 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
 141                     <= 0)
 142                         return; /* could not wait */
 143         }
 144         if (WIFSIGNALED(sshpam_thread_status) &&
 145             WTERMSIG(sshpam_thread_status) == SIGTERM)
 146                 return; /* terminated by pthread_cancel */
 147         if (!WIFEXITED(sshpam_thread_status))
 148                 fatal("PAM: authentication thread exited unexpectedly");
 149         if (WEXITSTATUS(sshpam_thread_status) != 0)
 150                 fatal("PAM: authentication thread exited uncleanly");
 151 }
 152
 153 static void
 154 pthread_exit(void *value __unused)
 155 {
 156         _exit(0);
 157 }
 158
 159 static int
 160 pthread_create(sp_pthread_t *thread, const void *attr __unused,
 161     void *(*thread_start)(void *), void *arg)
 162 {
 163         pid_t pid;
 164         struct pam_ctxt *ctx = arg;
 165
 166         sshpam_thread_status = -1;
 167         switch ((pid = fork())) {
 168         case -1:
 169                 error("fork(): %s", strerror(errno));
 170                 return (-1);
 171         case 0:
 172                 close(ctx->pam_psock);
 173                 ctx->pam_psock = -1;
 174                 thread_start(arg);
 175                 _exit(1);
 176         default:
 177                 *thread = pid;
 178                 close(ctx->pam_csock);
 179                 ctx->pam_csock = -1;
 180                 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
 181                 return (0);
 182         }
 183 }
 184
 185 static int
 186 pthread_cancel(sp_pthread_t thread)
 187 {
 188         signal(SIGCHLD, sshpam_oldsig);
 189         return (kill(thread, SIGTERM));
 190 }
 191
 192 static int
 193 pthread_join(sp_pthread_t thread, void **value __unused)
 194 {
 195         int status;
 196
 197         if (sshpam_thread_status != -1)
 198                 return (sshpam_thread_status);
 199         signal(SIGCHLD, sshpam_oldsig);
 200         waitpid(thread, &status, 0);
 201         return (status);
 202 }
 203 #endif
 204
 205
 206 static pam_handle_t *sshpam_handle = NULL;
 207 static int sshpam_err = 0;
 208 static int sshpam_authenticated = 0;
 209 static int sshpam_session_open = 0;
 210 static int sshpam_cred_established = 0;
 211 static int sshpam_account_status = -1;
 212 static char **sshpam_env = NULL;
 213 static Authctxt *sshpam_authctxt = NULL;
 214 static const char *sshpam_password = NULL;
 215 static char badpw[] = "\b\n\r\177INCORRECT";
 216
 217 /* Some PAM implementations don't implement this */
 218 #ifndef HAVE_PAM_GETENVLIST
 219 static char **
 220 pam_getenvlist(pam_handle_t *pamh)
 221 {
 222         /*
 223          * XXX - If necessary, we can still support envrionment passing
 224          * for platforms without pam_getenvlist by searching for known
 225          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 226          */
 227          return NULL;
 228 }
 229 #endif
 230
 231 /*
 232  * Some platforms, notably Solaris, do not enforce password complexity
 233  * rules during pam_chauthtok() if the real uid of the calling process
 234  * is 0, on the assumption that it's being called by "passwd" run by root.
 235  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 236  * the right thing.
 237  */
 238 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 239 static int
 240 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 241 {
 242         int result;
 243
 244         if (sshpam_authctxt == NULL)
 245                 fatal("PAM: sshpam_authctxt not initialized");
 246         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 247                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 248         result = pam_chauthtok(pamh, flags);
 249         if (setreuid(0, -1) == -1)
 250                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 251         return result;
 252 }
 253 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 254 #endif
 255
 256 void
 257 sshpam_password_change_required(int reqd)
 258 {
 259         debug3("%s %d", __func__, reqd);
 260         if (sshpam_authctxt == NULL)
 261                 fatal("%s: PAM authctxt not initialized", __func__);
 262         sshpam_authctxt->force_pwchange = reqd;
 263         if (reqd) {
 264                 no_port_forwarding_flag |= 2;
 265                 no_agent_forwarding_flag |= 2;
 266                 no_x11_forwarding_flag |= 2;
 267         } else {
 268                 no_port_forwarding_flag &= ~2;
 269                 no_agent_forwarding_flag &= ~2;
 270                 no_x11_forwarding_flag &= ~2;
 271         }
 272 }
 273
 274 /* Import regular and PAM environment from subprocess */
 275 static void
 276 import_environments(Buffer *b)
 277 {
 278         char *env;
 279         u_int i, num_env;
 280         int err;
 281
 282         debug3("PAM: %s entering", __func__);
 283
 284 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 285         /* Import variables set by do_pam_account */
 286         sshpam_account_status = buffer_get_int(b);
 287         sshpam_password_change_required(buffer_get_int(b));
 288
 289         /* Import environment from subprocess */
 290         num_env = buffer_get_int(b);
 291         if (num_env > 1024)
 292                 fatal("%s: received %u environment variables, expected <= 1024",
 293                     __func__, num_env);
 294         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 295         debug3("PAM: num env strings %d", num_env);
 296         for(i = 0; i < num_env; i++)
 297                 sshpam_env[i] = buffer_get_string(b, NULL);
 298
 299         sshpam_env[num_env] = NULL;
 300
 301         /* Import PAM environment from subprocess */
 302         num_env = buffer_get_int(b);
 303         debug("PAM: num PAM env strings %d", num_env);
 304         for(i = 0; i < num_env; i++) {
 305                 env = buffer_get_string(b, NULL);
 306
 307 #ifdef HAVE_PAM_PUTENV
 308                 /* Errors are not fatal here */
 309                 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 310                         error("PAM: pam_putenv: %s",
 311                             pam_strerror(sshpam_handle, sshpam_err));
 312                 }
 313 #endif
 314         }
 315 #endif
 316 }
 317
 318 /*
 319  * Conversation function for authentication thread.
 320  */
 321 static int
 322 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 323     struct pam_response **resp, void *data)
 324 {
 325         Buffer buffer;
 326         struct pam_ctxt *ctxt;
 327         struct pam_response *reply;
 328         int i;
 329
 330         debug3("PAM: %s entering, %d messages", __func__, n);
 331         *resp = NULL;
 332
 333         if (data == NULL) {
 334                 error("PAM: conversation function passed a null context");
 335                 return (PAM_CONV_ERR);
 336         }
 337         ctxt = data;
 338         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 339                 return (PAM_CONV_ERR);
 340
 341         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 342                 return (PAM_CONV_ERR);
 343
 344         buffer_init(&buffer);
 345         for (i = 0; i < n; ++i) {
 346                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 347                 case PAM_PROMPT_ECHO_OFF:
 348                         buffer_put_cstring(&buffer,
 349                             PAM_MSG_MEMBER(msg, i, msg));
 350                         if (ssh_msg_send(ctxt->pam_csock,
 351                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 352                                 goto fail;
 353                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 354                                 goto fail;
 355                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 356                                 goto fail;
 357                         reply[i].resp = buffer_get_string(&buffer, NULL);
 358                         break;
 359                 case PAM_PROMPT_ECHO_ON:
 360                         buffer_put_cstring(&buffer,
 361                             PAM_MSG_MEMBER(msg, i, msg));
 362                         if (ssh_msg_send(ctxt->pam_csock,
 363                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 364                                 goto fail;
 365                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 366                                 goto fail;
 367                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 368                                 goto fail;
 369                         reply[i].resp = buffer_get_string(&buffer, NULL);
 370                         break;
 371                 case PAM_ERROR_MSG:
 372                         buffer_put_cstring(&buffer,
 373                             PAM_MSG_MEMBER(msg, i, msg));
 374                         if (ssh_msg_send(ctxt->pam_csock,
 375                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 376                                 goto fail;
 377                         break;
 378                 case PAM_TEXT_INFO:
 379                         buffer_put_cstring(&buffer,
 380                             PAM_MSG_MEMBER(msg, i, msg));
 381                         if (ssh_msg_send(ctxt->pam_csock,
 382                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 383                                 goto fail;
 384                         break;
 385                 default:
 386                         goto fail;
 387                 }
 388                 buffer_clear(&buffer);
 389         }
 390         buffer_free(&buffer);
 391         *resp = reply;
 392         return (PAM_SUCCESS);
 393
 394  fail:
 395         for(i = 0; i < n; i++) {
 396                 if (reply[i].resp != NULL)
 397                         xfree(reply[i].resp);
 398         }
 399         xfree(reply);
 400         buffer_free(&buffer);
 401         return (PAM_CONV_ERR);
 402 }
 403
 404 /*
 405  * Authentication thread.
 406  */
 407 static void *
 408 sshpam_thread(void *ctxtp)
 409 {
 410         struct pam_ctxt *ctxt = ctxtp;
 411         Buffer buffer;
 412         struct pam_conv sshpam_conv;
 413         int flags = (options.permit_empty_passwd == 0 ?
 414             PAM_DISALLOW_NULL_AUTHTOK : 0);
 415 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 416         extern char **environ;
 417         char **env_from_pam;
 418         u_int i;
 419         const char *pam_user;
 420         const char **ptr_pam_user = &pam_user;
 421
 422         pam_get_item(sshpam_handle, PAM_USER,
 423             (sshpam_const void **)ptr_pam_user);
 424         environ[0] = NULL;
 425
 426         if (sshpam_authctxt != NULL) {
 427                 setproctitle("%s [pam]",
 428                     sshpam_authctxt->valid ? pam_user : "unknown");
 429         }
 430 #endif
 431
 432         sshpam_conv.conv = sshpam_thread_conv;
 433         sshpam_conv.appdata_ptr = ctxt;
 434
 435         if (sshpam_authctxt == NULL)
 436                 fatal("%s: PAM authctxt not initialized", __func__);
 437
 438         buffer_init(&buffer);
 439         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 440             (const void *)&sshpam_conv);
 441         if (sshpam_err != PAM_SUCCESS)
 442                 goto auth_fail;
 443         sshpam_err = pam_authenticate(sshpam_handle, flags);
 444         if (sshpam_err != PAM_SUCCESS)
 445                 goto auth_fail;
 446
 447         if (compat20) {
 448                 if (!do_pam_account()) {
 449                         sshpam_err = PAM_ACCT_EXPIRED;
 450                         goto auth_fail;
 451                 }
 452                 if (sshpam_authctxt->force_pwchange) {
 453                         sshpam_err = pam_chauthtok(sshpam_handle,
 454                             PAM_CHANGE_EXPIRED_AUTHTOK);
 455                         if (sshpam_err != PAM_SUCCESS)
 456                                 goto auth_fail;
 457                         sshpam_password_change_required(0);
 458                 }
 459         }
 460
 461         buffer_put_cstring(&buffer, "OK");
 462
 463 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 464         /* Export variables set by do_pam_account */
 465         buffer_put_int(&buffer, sshpam_account_status);
 466         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 467
 468         /* Export any environment strings set in child */
 469         for(i = 0; environ[i] != NULL; i++)
 470                 ; /* Count */
 471         buffer_put_int(&buffer, i);
 472         for(i = 0; environ[i] != NULL; i++)
 473                 buffer_put_cstring(&buffer, environ[i]);
 474
 475         /* Export any environment strings set by PAM in child */
 476         env_from_pam = pam_getenvlist(sshpam_handle);
 477         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 478                 ; /* Count */
 479         buffer_put_int(&buffer, i);
 480         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 481                 buffer_put_cstring(&buffer, env_from_pam[i]);
 482 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 483
 484         /* XXX - can't do much about an error here */
 485         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 486         buffer_free(&buffer);
 487         pthread_exit(NULL);
 488
 489  auth_fail:
 490         buffer_put_cstring(&buffer,
 491             pam_strerror(sshpam_handle, sshpam_err));
 492         /* XXX - can't do much about an error here */
 493         if (sshpam_err == PAM_ACCT_EXPIRED)
 494                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);
 495         else
 496                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 497         buffer_free(&buffer);
 498         pthread_exit(NULL);
 499
 500         return (NULL); /* Avoid warning for non-pthread case */
 501 }
 502
 503 void
 504 sshpam_thread_cleanup(void)
 505 {
 506         struct pam_ctxt *ctxt = cleanup_ctxt;
 507
 508         debug3("PAM: %s entering", __func__);
 509         if (ctxt != NULL && ctxt->pam_thread != 0) {
 510                 pthread_cancel(ctxt->pam_thread);
 511                 pthread_join(ctxt->pam_thread, NULL);
 512                 close(ctxt->pam_psock);
 513                 close(ctxt->pam_csock);
 514                 memset(ctxt, 0, sizeof(*ctxt));
 515                 cleanup_ctxt = NULL;
 516         }
 517 }
 518
 519 static int
 520 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 521     struct pam_response **resp, void *data)
 522 {
 523         debug3("PAM: %s entering, %d messages", __func__, n);
 524         return (PAM_CONV_ERR);
 525 }
 526
 527 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 528
 529 static int
 530 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 531     struct pam_response **resp, void *data)
 532 {
 533         struct pam_response *reply;
 534         int i;
 535         size_t len;
 536
 537         debug3("PAM: %s called with %d messages", __func__, n);
 538         *resp = NULL;
 539
 540         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 541                 return (PAM_CONV_ERR);
 542
 543         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 544                 return (PAM_CONV_ERR);
 545
 546         for (i = 0; i < n; ++i) {
 547                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 548                 case PAM_ERROR_MSG:
 549                 case PAM_TEXT_INFO:
 550                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 551                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 552                         buffer_append(&loginmsg, "\n", 1 );
 553                         reply[i].resp_retcode = PAM_SUCCESS;
 554                         break;
 555                 default:
 556                         goto fail;
 557                 }
 558         }
 559         *resp = reply;
 560         return (PAM_SUCCESS);
 561
 562  fail:
 563         for(i = 0; i < n; i++) {
 564                 if (reply[i].resp != NULL)
 565                         xfree(reply[i].resp);
 566         }
 567         xfree(reply);
 568         return (PAM_CONV_ERR);
 569 }
 570
 571 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 572
 573 void
 574 sshpam_cleanup(void)
 575 {
 576         debug("PAM: cleanup");
 577         if (sshpam_handle == NULL)
 578                 return;
 579         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 580         if (sshpam_cred_established) {
 581                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 582                 sshpam_cred_established = 0;
 583         }
 584         if (sshpam_session_open) {
 585                 pam_close_session(sshpam_handle, PAM_SILENT);
 586                 sshpam_session_open = 0;
 587         }
 588         sshpam_authenticated = 0;
 589         pam_end(sshpam_handle, sshpam_err);
 590         sshpam_handle = NULL;
 591 }
 592
 593 static int
 594 sshpam_init(Authctxt *authctxt)
 595 {
 596         extern char *__progname;
 597         const char *pam_rhost, *pam_user, *user = authctxt->user;
 598         const char **ptr_pam_user = &pam_user;
 599
 600         if (sshpam_handle != NULL) {
 601                 /* We already have a PAM context; check if the user matches */
 602                 sshpam_err = pam_get_item(sshpam_handle,
 603                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 604                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 605                         return (0);
 606                 pam_end(sshpam_handle, sshpam_err);
 607                 sshpam_handle = NULL;
 608         }
 609         debug("PAM: initializing for \"%s\"", user);
 610         sshpam_err =
 611             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 612         sshpam_authctxt = authctxt;
 613
 614         if (sshpam_err != PAM_SUCCESS) {
 615                 pam_end(sshpam_handle, sshpam_err);
 616                 sshpam_handle = NULL;
 617                 return (-1);
 618         }
 619         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 620         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 621         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 622         if (sshpam_err != PAM_SUCCESS) {
 623                 pam_end(sshpam_handle, sshpam_err);
 624                 sshpam_handle = NULL;
 625                 return (-1);
 626         }
 627 #ifdef PAM_TTY_KLUDGE
 628         /*
 629          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 630          * sshd doesn't set the tty until too late in the auth process and
 631          * may not even set one (for tty-less connections)
 632          */
 633         debug("PAM: setting PAM_TTY to \"ssh\"");
 634         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 635         if (sshpam_err != PAM_SUCCESS) {
 636                 pam_end(sshpam_handle, sshpam_err);
 637                 sshpam_handle = NULL;
 638                 return (-1);
 639         }
 640 #endif
 641         return (0);
 642 }
 643
 644 static void *
 645 sshpam_init_ctx(Authctxt *authctxt)
 646 {
 647         struct pam_ctxt *ctxt;
 648         int socks[2];
 649
 650         debug3("PAM: %s entering", __func__);
 651         /*
 652          * Refuse to start if we don't have PAM enabled or do_pam_account
 653          * has previously failed.
 654          */
 655         if (!options.use_pam || sshpam_account_status == 0)
 656                 return NULL;
 657
 658         /* Initialize PAM */
 659         if (sshpam_init(authctxt) == -1) {
 660                 error("PAM: initialization failed");
 661                 return (NULL);
 662         }
 663
 664         ctxt = xmalloc(sizeof *ctxt);
 665         memset(ctxt, 0, sizeof(*ctxt));
 666
 667         /* Start the authentication thread */
 668         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 669                 error("PAM: failed create sockets: %s", strerror(errno));
 670                 xfree(ctxt);
 671                 return (NULL);
 672         }
 673         ctxt->pam_psock = socks[0];
 674         ctxt->pam_csock = socks[1];
 675         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 676                 error("PAM: failed to start authentication thread: %s",
 677                     strerror(errno));
 678                 close(socks[0]);
 679                 close(socks[1]);
 680                 xfree(ctxt);
 681                 return (NULL);
 682         }
 683         cleanup_ctxt = ctxt;
 684         return (ctxt);
 685 }
 686
 687 static int
 688 sshpam_query(void *ctx, char **name, char **info,
 689     u_int *num, char ***prompts, u_int **echo_on)
 690 {
 691         Buffer buffer;
 692         struct pam_ctxt *ctxt = ctx;
 693         size_t plen;
 694         u_char type;
 695         char *msg;
 696         size_t len, mlen;
 697
 698         debug3("PAM: %s entering", __func__);
 699         buffer_init(&buffer);
 700         *name = xstrdup("");
 701         *info = xstrdup("");
 702         *prompts = xmalloc(sizeof(char *));
 703         **prompts = NULL;
 704         plen = 0;
 705         *echo_on = xmalloc(sizeof(u_int));
 706         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 707                 type = buffer_get_char(&buffer);
 708                 msg = buffer_get_string(&buffer, NULL);
 709                 mlen = strlen(msg);
 710                 switch (type) {
 711                 case PAM_PROMPT_ECHO_ON:
 712                 case PAM_PROMPT_ECHO_OFF:
 713                         *num = 1;
 714                         len = plen + mlen + 1;
 715                         **prompts = xrealloc(**prompts, 1, len);
 716                         strlcpy(**prompts + plen, msg, len - plen);
 717                         plen += mlen;
 718                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 719                         xfree(msg);
 720                         return (0);
 721                 case PAM_ERROR_MSG:
 722                 case PAM_TEXT_INFO:
 723                         /* accumulate messages */
 724                         len = plen + mlen + 2;
 725                         **prompts = xrealloc(**prompts, 1, len);
 726                         strlcpy(**prompts + plen, msg, len - plen);
 727                         plen += mlen;
 728                         strlcat(**prompts + plen, "\n", len - plen);
 729                         plen++;
 730                         xfree(msg);
 731                         break;
 732                 case PAM_ACCT_EXPIRED:
 733                         sshpam_account_status = 0;
 734                         /* FALLTHROUGH */
 735                 case PAM_AUTH_ERR:
 736                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 737                         if (**prompts != NULL && strlen(**prompts) != 0) {
 738                                 *info = **prompts;
 739                                 **prompts = NULL;
 740                                 *num = 0;
 741                                 **echo_on = 0;
 742                                 ctxt->pam_done = -1;
 743                                 xfree(msg);
 744                                 return 0;
 745                         }
 746                         /* FALLTHROUGH */
 747                 case PAM_SUCCESS:
 748                         if (**prompts != NULL) {
 749                                 /* drain any accumulated messages */
 750                                 debug("PAM: %s", **prompts);
 751                                 buffer_append(&loginmsg, **prompts,
 752                                     strlen(**prompts));
 753                                 xfree(**prompts);
 754                                 **prompts = NULL;
 755                         }
 756                         if (type == PAM_SUCCESS) {
 757                                 if (!sshpam_authctxt->valid ||
 758                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 759                                     options.permit_root_login != PERMIT_YES))
 760                                         fatal("Internal error: PAM auth "
 761                                             "succeeded when it should have "
 762                                             "failed");
 763                                 import_environments(&buffer);
 764                                 *num = 0;
 765                                 **echo_on = 0;
 766                                 ctxt->pam_done = 1;
 767                                 xfree(msg);
 768                                 return (0);
 769                         }
 770                         error("PAM: %s for %s%.100s from %.100s", msg,
 771                             sshpam_authctxt->valid ? "" : "illegal user ",
 772                             sshpam_authctxt->user,
 773                             get_remote_name_or_ip(utmp_len, options.use_dns));
 774                         /* FALLTHROUGH */
 775                 default:
 776                         *num = 0;
 777                         **echo_on = 0;
 778                         xfree(msg);
 779                         ctxt->pam_done = -1;
 780                         return (-1);
 781                 }
 782         }
 783         return (-1);
 784 }
 785
 786 /* XXX - see also comment in auth-chall.c:verify_response */
 787 static int
 788 sshpam_respond(void *ctx, u_int num, char **resp)
 789 {
 790         Buffer buffer;
 791         struct pam_ctxt *ctxt = ctx;
 792
 793         debug2("PAM: %s entering, %u responses", __func__, num);
 794         switch (ctxt->pam_done) {
 795         case 1:
 796                 sshpam_authenticated = 1;
 797                 return (0);
 798         case 0:
 799                 break;
 800         default:
 801                 return (-1);
 802         }
 803         if (num != 1) {
 804                 error("PAM: expected one response, got %u", num);
 805                 return (-1);
 806         }
 807         buffer_init(&buffer);
 808         if (sshpam_authctxt->valid &&
 809             (sshpam_authctxt->pw->pw_uid != 0 ||
 810             options.permit_root_login == PERMIT_YES))
 811                 buffer_put_cstring(&buffer, *resp);
 812         else
 813                 buffer_put_cstring(&buffer, badpw);
 814         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 815                 buffer_free(&buffer);
 816                 return (-1);
 817         }
 818         buffer_free(&buffer);
 819         return (1);
 820 }
 821
 822 static void
 823 sshpam_free_ctx(void *ctxtp)
 824 {
 825         struct pam_ctxt *ctxt = ctxtp;
 826
 827         debug3("PAM: %s entering", __func__);
 828         sshpam_thread_cleanup();
 829         xfree(ctxt);
 830         /*
 831          * We don't call sshpam_cleanup() here because we may need the PAM
 832          * handle at a later stage, e.g. when setting up a session.  It's
 833          * still on the cleanup list, so pam_end() *will* be called before
 834          * the server process terminates.
 835          */
 836 }
 837
 838 KbdintDevice sshpam_device = {
 839         "pam",
 840         sshpam_init_ctx,
 841         sshpam_query,
 842         sshpam_respond,
 843         sshpam_free_ctx
 844 };
 845
 846 KbdintDevice mm_sshpam_device = {
 847         "pam",
 848         mm_sshpam_init_ctx,
 849         mm_sshpam_query,
 850         mm_sshpam_respond,
 851         mm_sshpam_free_ctx
 852 };
 853
 854 /*
 855  * This replaces auth-pam.c
 856  */
 857 void
 858 start_pam(Authctxt *authctxt)
 859 {
 860         if (!options.use_pam)
 861                 fatal("PAM: initialisation requested when UsePAM=no");
 862
 863         if (sshpam_init(authctxt) == -1)
 864                 fatal("PAM: initialisation failed");
 865 }
 866
 867 void
 868 finish_pam(void)
 869 {
 870         sshpam_cleanup();
 871 }
 872
 873 u_int
 874 do_pam_account(void)
 875 {
 876         debug("%s: called", __func__);
 877         if (sshpam_account_status != -1)
 878                 return (sshpam_account_status);
 879
 880         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 881         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 882             pam_strerror(sshpam_handle, sshpam_err));
 883
 884         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 885                 sshpam_account_status = 0;
 886                 return (sshpam_account_status);
 887         }
 888
 889         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 890                 sshpam_password_change_required(1);
 891
 892         sshpam_account_status = 1;
 893         return (sshpam_account_status);
 894 }
 895
 896 void
 897 do_pam_set_tty(const char *tty)
 898 {
 899         if (tty != NULL) {
 900                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 901                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 902                 if (sshpam_err != PAM_SUCCESS)
 903                         fatal("PAM: failed to set PAM_TTY: %s",
 904                             pam_strerror(sshpam_handle, sshpam_err));
 905         }
 906 }
 907
 908 void
 909 do_pam_setcred(int init)
 910 {
 911         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 912             (const void *)&store_conv);
 913         if (sshpam_err != PAM_SUCCESS)
 914                 fatal("PAM: failed to set PAM_CONV: %s",
 915                     pam_strerror(sshpam_handle, sshpam_err));
 916         if (init) {
 917                 debug("PAM: establishing credentials");
 918                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 919         } else {
 920                 debug("PAM: reinitializing credentials");
 921                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 922         }
 923         if (sshpam_err == PAM_SUCCESS) {
 924                 sshpam_cred_established = 1;
 925                 return;
 926         }
 927         if (sshpam_authenticated)
 928                 fatal("PAM: pam_setcred(): %s",
 929                     pam_strerror(sshpam_handle, sshpam_err));
 930         else
 931                 debug("PAM: pam_setcred(): %s",
 932                     pam_strerror(sshpam_handle, sshpam_err));
 933 }
 934
 935 static int
 936 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 937     struct pam_response **resp, void *data)
 938 {
 939         char input[PAM_MAX_MSG_SIZE];
 940         struct pam_response *reply;
 941         int i;
 942
 943         debug3("PAM: %s called with %d messages", __func__, n);
 944
 945         *resp = NULL;
 946
 947         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 948                 return (PAM_CONV_ERR);
 949
 950         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 951                 return (PAM_CONV_ERR);
 952
 953         for (i = 0; i < n; ++i) {
 954                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 955                 case PAM_PROMPT_ECHO_OFF:
 956                         reply[i].resp =
 957                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 958                             RP_ALLOW_STDIN);
 959                         reply[i].resp_retcode = PAM_SUCCESS;
 960                         break;
 961                 case PAM_PROMPT_ECHO_ON:
 962                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 963                         fgets(input, sizeof input, stdin);
 964                         if ((reply[i].resp = strdup(input)) == NULL)
 965                                 goto fail;
 966                         reply[i].resp_retcode = PAM_SUCCESS;
 967                         break;
 968                 case PAM_ERROR_MSG:
 969                 case PAM_TEXT_INFO:
 970                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 971                         reply[i].resp_retcode = PAM_SUCCESS;
 972                         break;
 973                 default:
 974                         goto fail;
 975                 }
 976         }
 977         *resp = reply;
 978         return (PAM_SUCCESS);
 979
 980  fail:
 981         for(i = 0; i < n; i++) {
 982                 if (reply[i].resp != NULL)
 983                         xfree(reply[i].resp);
 984         }
 985         xfree(reply);
 986         return (PAM_CONV_ERR);
 987 }
 988
 989 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
 990
 991 /*
 992  * XXX this should be done in the authentication phase, but ssh1 doesn't
 993  * support that
 994  */
 995 void
 996 do_pam_chauthtok(void)
 997 {
 998         if (use_privsep)
 999                 fatal("Password expired (unable to change with privsep)");
1000         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1001             (const void *)&tty_conv);
1002         if (sshpam_err != PAM_SUCCESS)
1003                 fatal("PAM: failed to set PAM_CONV: %s",
1004                     pam_strerror(sshpam_handle, sshpam_err));
1005         debug("PAM: changing password");
1006         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1007         if (sshpam_err != PAM_SUCCESS)
1008                 fatal("PAM: pam_chauthtok(): %s",
1009                     pam_strerror(sshpam_handle, sshpam_err));
1010 }
1011
1012 void
1013 do_pam_session(void)
1014 {
1015         debug3("PAM: opening session");
1016         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1017             (const void *)&store_conv);
1018         if (sshpam_err != PAM_SUCCESS)
1019                 fatal("PAM: failed to set PAM_CONV: %s",
1020                     pam_strerror(sshpam_handle, sshpam_err));
1021         sshpam_err = pam_open_session(sshpam_handle, 0);
1022         if (sshpam_err == PAM_SUCCESS)
1023                 sshpam_session_open = 1;
1024         else {
1025                 sshpam_session_open = 0;
1026                 disable_forwarding();
1027                 error("PAM: pam_open_session(): %s",
1028                     pam_strerror(sshpam_handle, sshpam_err));
1029         }
1030
1031 }
1032
1033 int
1034 is_pam_session_open(void)
1035 {
1036         return sshpam_session_open;
1037 }
1038
1039 /*
1040  * Set a PAM environment string. We need to do this so that the session
1041  * modules can handle things like Kerberos/GSI credentials that appear
1042  * during the ssh authentication process.
1043  */
1044 int
1045 do_pam_putenv(char *name, char *value)
1046 {
1047         int ret = 1;
1048 #ifdef HAVE_PAM_PUTENV
1049         char *compound;
1050         size_t len;
1051
1052         len = strlen(name) + strlen(value) + 2;
1053         compound = xmalloc(len);
1054
1055         snprintf(compound, len, "%s=%s", name, value);
1056         ret = pam_putenv(sshpam_handle, compound);
1057         xfree(compound);
1058 #endif
1059
1060         return (ret);
1061 }
1062
1063 char **
1064 fetch_pam_child_environment(void)
1065 {
1066         return sshpam_env;
1067 }
1068
1069 char **
1070 fetch_pam_environment(void)
1071 {
1072         return (pam_getenvlist(sshpam_handle));
1073 }
1074
1075 void
1076 free_pam_environment(char **env)
1077 {
1078         char **envp;
1079
1080         if (env == NULL)
1081                 return;
1082
1083         for (envp = env; *envp; envp++)
1084                 xfree(*envp);
1085         xfree(env);
1086 }
1087
1088 /*
1089  * "Blind" conversation function for password authentication.  Assumes that
1090  * echo-off prompts are for the password and stores messages for later
1091  * display.
1092  */
1093 static int
1094 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1095     struct pam_response **resp, void *data)
1096 {
1097         struct pam_response *reply;
1098         int i;
1099         size_t len;
1100
1101         debug3("PAM: %s called with %d messages", __func__, n);
1102
1103         *resp = NULL;
1104
1105         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1106                 return (PAM_CONV_ERR);
1107
1108         if ((reply = malloc(n * sizeof(*reply))) == NULL)
1109                 return (PAM_CONV_ERR);
1110         memset(reply, 0, n * sizeof(*reply));
1111
1112         for (i = 0; i < n; ++i) {
1113                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1114                 case PAM_PROMPT_ECHO_OFF:
1115                         if (sshpam_password == NULL)
1116                                 goto fail;
1117                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1118                                 goto fail;
1119                         reply[i].resp_retcode = PAM_SUCCESS;
1120                         break;
1121                 case PAM_ERROR_MSG:
1122                 case PAM_TEXT_INFO:
1123                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1124                         if (len > 0) {
1125                                 buffer_append(&loginmsg,
1126                                     PAM_MSG_MEMBER(msg, i, msg), len);
1127                                 buffer_append(&loginmsg, "\n", 1);
1128                         }
1129                         if ((reply[i].resp = strdup("")) == NULL)
1130                                 goto fail;
1131                         reply[i].resp_retcode = PAM_SUCCESS;
1132                         break;
1133                 default:
1134                         goto fail;
1135                 }
1136         }
1137         *resp = reply;
1138         return (PAM_SUCCESS);
1139
1140  fail:
1141         for(i = 0; i < n; i++) {
1142                 if (reply[i].resp != NULL)
1143                         xfree(reply[i].resp);
1144         }
1145         xfree(reply);
1146         return (PAM_CONV_ERR);
1147 }
1148
1149 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1150
1151 /*
1152  * Attempt password authentication via PAM
1153  */
1154 int
1155 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1156 {
1157         int flags = (options.permit_empty_passwd == 0 ?
1158             PAM_DISALLOW_NULL_AUTHTOK : 0);
1159
1160         if (!options.use_pam || sshpam_handle == NULL)
1161                 fatal("PAM: %s called when PAM disabled or failed to "
1162                     "initialise.", __func__);
1163
1164         sshpam_password = password;
1165         sshpam_authctxt = authctxt;
1166
1167         /*
1168          * If the user logging in is invalid, or is root but is not permitted
1169          * by PermitRootLogin, use an invalid password to prevent leaking
1170          * information via timing (eg if the PAM config has a delay on fail).
1171          */
1172         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1173             options.permit_root_login != PERMIT_YES))
1174                 sshpam_password = badpw;
1175
1176         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1177             (const void *)&passwd_conv);
1178         if (sshpam_err != PAM_SUCCESS)
1179                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1180                     pam_strerror(sshpam_handle, sshpam_err));
1181
1182         sshpam_err = pam_authenticate(sshpam_handle, flags);
1183         sshpam_password = NULL;
1184         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1185                 debug("PAM: password authentication accepted for %.100s",
1186                     authctxt->user);
1187                 return 1;
1188         } else {
1189                 debug("PAM: password authentication failed for %.100s: %s",
1190                     authctxt->valid ? authctxt->user : "an illegal user",
1191                     pam_strerror(sshpam_handle, sshpam_err));
1192                 return 0;
1193         }
1194 }
1195 #endif /* USE_PAM */