crypto/openssh/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 */
  49
  50 #include "includes.h"
  51
  52 #include <sys/types.h>
  53 #include <sys/stat.h>
  54 #include <sys/wait.h>
  55
  56 #include <errno.h>
  57 #include <signal.h>
  58 #include <stdarg.h>
  59 #include <stdlib.h>
  60 #include <string.h>
  61 #include <unistd.h>
  62
  63 #ifdef USE_PAM
  64 #if defined(HAVE_SECURITY_PAM_APPL_H)
  65 #include <security/pam_appl.h>
  66 #elif defined (HAVE_PAM_PAM_APPL_H)
  67 #include <pam/pam_appl.h>
  68 #endif
  69
  70 #if !defined(SSHD_PAM_SERVICE)
  71 extern char *__progname;
  72 # define SSHD_PAM_SERVICE               __progname
  73 #endif
  74
  75 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
  76 #ifdef PAM_SUN_CODEBASE
  77 # define sshpam_const           /* Solaris, HP-UX, SunOS */
  78 #else
  79 # define sshpam_const   const   /* LinuxPAM, OpenPAM, AIX */
  80 #endif
  81
  82 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
  83 #ifdef PAM_SUN_CODEBASE
  84 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
  85 #else
  86 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
  87 #endif
  88
  89 #include "xmalloc.h"
  90 #include "sshbuf.h"
  91 #include "ssherr.h"
  92 #include "hostfile.h"
  93 #include "auth.h"
  94 #include "auth-pam.h"
  95 #include "canohost.h"
  96 #include "log.h"
  97 #include "msg.h"
  98 #include "packet.h"
  99 #include "misc.h"
 100 #include "servconf.h"
 101 #include "ssh2.h"
 102 #include "auth-options.h"
 103 #include "misc.h"
 104 #ifdef GSSAPI
 105 #include "ssh-gss.h"
 106 #endif
 107 #include "monitor_wrap.h"
 108 #include "blacklist_client.h"
 109
 110 extern ServerOptions options;
 111 extern struct sshbuf *loginmsg;
 112 extern u_int utmp_len;
 113
 114 /* so we don't silently change behaviour */
 115 #ifdef USE_POSIX_THREADS
 116 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
 117 #endif
 118
 119 /*
 120  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
 121  * and generally a bad idea.  Use at own risk and do not expect support if
 122  * this breaks.
 123  */
 124 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
 125 #include <pthread.h>
 126 /*
 127  * Avoid namespace clash when *not* using pthreads for systems *with*
 128  * pthreads, which unconditionally define pthread_t via sys/types.h
 129  * (e.g. Linux)
 130  */
 131 typedef pthread_t sp_pthread_t;
 132 #else
 133 typedef pid_t sp_pthread_t;
 134 #define pthread_exit    fake_pthread_exit
 135 #define pthread_create  fake_pthread_create
 136 #define pthread_cancel  fake_pthread_cancel
 137 #define pthread_join    fake_pthread_join
 138 #endif
 139
 140 struct pam_ctxt {
 141         sp_pthread_t     pam_thread;
 142         int              pam_psock;
 143         int              pam_csock;
 144         int              pam_done;
 145 };
 146
 147 static void sshpam_free_ctx(void *);
 148 static struct pam_ctxt *cleanup_ctxt;
 149
 150 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 151 /*
 152  * Simulate threads with processes.
 153  */
 154
 155 static int sshpam_thread_status = -1;
 156 static sshsig_t sshpam_oldsig;
 157
 158 static void
 159 sshpam_sigchld_handler(int sig)
 160 {
 161         ssh_signal(SIGCHLD, SIG_DFL);
 162         if (cleanup_ctxt == NULL)
 163                 return; /* handler called after PAM cleanup, shouldn't happen */
 164         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 165             <= 0) {
 166                 /* PAM thread has not exitted, privsep slave must have */
 167                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 168                 while (waitpid(cleanup_ctxt->pam_thread,
 169                     &sshpam_thread_status, 0) == -1) {
 170                         if (errno == EINTR)
 171                                 continue;
 172                         return;
 173                 }
 174         }
 175         if (WIFSIGNALED(sshpam_thread_status) &&
 176             WTERMSIG(sshpam_thread_status) == SIGTERM)
 177                 return; /* terminated by pthread_cancel */
 178         if (!WIFEXITED(sshpam_thread_status))
 179                 sigdie("PAM: authentication thread exited unexpectedly");
 180         if (WEXITSTATUS(sshpam_thread_status) != 0)
 181                 sigdie("PAM: authentication thread exited uncleanly");
 182 }
 183
 184 /* ARGSUSED */
 185 static void
 186 pthread_exit(void *value)
 187 {
 188         _exit(0);
 189 }
 190
 191 /* ARGSUSED */
 192 static int
 193 pthread_create(sp_pthread_t *thread, const void *attr,
 194     void *(*thread_start)(void *), void *arg)
 195 {
 196         pid_t pid;
 197         struct pam_ctxt *ctx = arg;
 198
 199         sshpam_thread_status = -1;
 200         switch ((pid = fork())) {
 201         case -1:
 202                 error("fork(): %s", strerror(errno));
 203                 return errno;
 204         case 0:
 205                 close(ctx->pam_psock);
 206                 ctx->pam_psock = -1;
 207                 thread_start(arg);
 208                 _exit(1);
 209         default:
 210                 *thread = pid;
 211                 close(ctx->pam_csock);
 212                 ctx->pam_csock = -1;
 213                 sshpam_oldsig = ssh_signal(SIGCHLD, sshpam_sigchld_handler);
 214                 return (0);
 215         }
 216 }
 217
 218 static int
 219 pthread_cancel(sp_pthread_t thread)
 220 {
 221         ssh_signal(SIGCHLD, sshpam_oldsig);
 222         return (kill(thread, SIGTERM));
 223 }
 224
 225 /* ARGSUSED */
 226 static int
 227 pthread_join(sp_pthread_t thread, void **value)
 228 {
 229         int status;
 230
 231         if (sshpam_thread_status != -1)
 232                 return (sshpam_thread_status);
 233         ssh_signal(SIGCHLD, sshpam_oldsig);
 234         while (waitpid(thread, &status, 0) == -1) {
 235                 if (errno == EINTR)
 236                         continue;
 237                 fatal("%s: waitpid: %s", __func__, strerror(errno));
 238         }
 239         return (status);
 240 }
 241 #endif
 242
 243
 244 static pam_handle_t *sshpam_handle = NULL;
 245 static int sshpam_err = 0;
 246 static int sshpam_authenticated = 0;
 247 static int sshpam_session_open = 0;
 248 static int sshpam_cred_established = 0;
 249 static int sshpam_account_status = -1;
 250 static int sshpam_maxtries_reached = 0;
 251 static char **sshpam_env = NULL;
 252 static Authctxt *sshpam_authctxt = NULL;
 253 static const char *sshpam_password = NULL;
 254 static char *sshpam_rhost = NULL;
 255 static char *sshpam_laddr = NULL;
 256 static char *sshpam_conninfo = NULL;
 257
 258 /* Some PAM implementations don't implement this */
 259 #ifndef HAVE_PAM_GETENVLIST
 260 static char **
 261 pam_getenvlist(pam_handle_t *pamh)
 262 {
 263         /*
 264          * XXX - If necessary, we can still support environment passing
 265          * for platforms without pam_getenvlist by searching for known
 266          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 267          */
 268          return NULL;
 269 }
 270 #endif
 271
 272 #ifndef HAVE_PAM_PUTENV
 273 static int
 274 pam_putenv(pam_handle_t *pamh, const char *name_value)
 275 {
 276         return PAM_SUCCESS;
 277 }
 278 #endif /* HAVE_PAM_PUTENV */
 279
 280 /*
 281  * Some platforms, notably Solaris, do not enforce password complexity
 282  * rules during pam_chauthtok() if the real uid of the calling process
 283  * is 0, on the assumption that it's being called by "passwd" run by root.
 284  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 285  * the right thing.
 286  */
 287 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 288 static int
 289 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 290 {
 291         int result;
 292
 293         if (sshpam_authctxt == NULL)
 294                 fatal("PAM: sshpam_authctxt not initialized");
 295         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 296                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 297         result = pam_chauthtok(pamh, flags);
 298         if (setreuid(0, -1) == -1)
 299                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 300         return result;
 301 }
 302 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 303 #endif
 304
 305 static void
 306 sshpam_password_change_required(int reqd)
 307 {
 308         extern struct sshauthopt *auth_opts;
 309         static int saved_port, saved_agent, saved_x11;
 310
 311         debug3("%s %d", __func__, reqd);
 312         if (sshpam_authctxt == NULL)
 313                 fatal("%s: PAM authctxt not initialized", __func__);
 314         sshpam_authctxt->force_pwchange = reqd;
 315         if (reqd) {
 316                 saved_port = auth_opts->permit_port_forwarding_flag;
 317                 saved_agent = auth_opts->permit_agent_forwarding_flag;
 318                 saved_x11 = auth_opts->permit_x11_forwarding_flag;
 319                 auth_opts->permit_port_forwarding_flag = 0;
 320                 auth_opts->permit_agent_forwarding_flag = 0;
 321                 auth_opts->permit_x11_forwarding_flag = 0;
 322         } else {
 323                 if (saved_port)
 324                         auth_opts->permit_port_forwarding_flag = saved_port;
 325                 if (saved_agent)
 326                         auth_opts->permit_agent_forwarding_flag = saved_agent;
 327                 if (saved_x11)
 328                         auth_opts->permit_x11_forwarding_flag = saved_x11;
 329         }
 330 }
 331
 332 /* Import regular and PAM environment from subprocess */
 333 static void
 334 import_environments(struct sshbuf *b)
 335 {
 336         char *env;
 337         u_int n, i, num_env;
 338         int r;
 339
 340         debug3("PAM: %s entering", __func__);
 341
 342 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 343         /* Import variables set by do_pam_account */
 344         if ((r = sshbuf_get_u32(b, &n)) != 0)
 345                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 346         if (n > INT_MAX)
 347                 fatal("%s: invalid PAM account status %u", __func__, n);
 348         sshpam_account_status = (int)n;
 349         if ((r = sshbuf_get_u32(b, &n)) != 0)
 350                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 351         sshpam_password_change_required(n != 0);
 352
 353         /* Import environment from subprocess */
 354         if ((r = sshbuf_get_u32(b, &num_env)) != 0)
 355                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 356         if (num_env > 1024)
 357                 fatal("%s: received %u environment variables, expected <= 1024",
 358                     __func__, num_env);
 359         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 360         debug3("PAM: num env strings %d", num_env);
 361         for(i = 0; i < num_env; i++) {
 362                 if ((r = sshbuf_get_cstring(b, &(sshpam_env[i]), NULL)) != 0)
 363                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 364         }
 365         sshpam_env[num_env] = NULL;
 366
 367         /* Import PAM environment from subprocess */
 368         if ((r = sshbuf_get_u32(b, &num_env)) != 0)
 369                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 370         debug("PAM: num PAM env strings %d", num_env);
 371         for (i = 0; i < num_env; i++) {
 372                 if ((r = sshbuf_get_cstring(b, &env, NULL)) != 0)
 373                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 374                 /* Errors are not fatal here */
 375                 if ((r = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 376                         error("PAM: pam_putenv: %s",
 377                             pam_strerror(sshpam_handle, r));
 378                 }
 379                 /*
 380                  * XXX this possibly leaks env because it is not documented
 381                  * what pam_putenv() does with it. Does it copy it? Does it
 382                  * take ownweship? We don't know, so it's safest just to leak.
 383                  */
 384         }
 385 #endif
 386 }
 387
 388 /*
 389  * Conversation function for authentication thread.
 390  */
 391 static int
 392 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 393     struct pam_response **resp, void *data)
 394 {
 395         struct sshbuf *buffer;
 396         struct pam_ctxt *ctxt;
 397         struct pam_response *reply;
 398         int r, i;
 399         u_char status;
 400
 401         debug3("PAM: %s entering, %d messages", __func__, n);
 402         *resp = NULL;
 403
 404         if (data == NULL) {
 405                 error("PAM: conversation function passed a null context");
 406                 return (PAM_CONV_ERR);
 407         }
 408         ctxt = data;
 409         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 410                 return (PAM_CONV_ERR);
 411
 412         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 413                 return PAM_CONV_ERR;
 414         if ((buffer = sshbuf_new()) == NULL) {
 415                 free(reply);
 416                 return PAM_CONV_ERR;
 417         }
 418
 419         for (i = 0; i < n; ++i) {
 420                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 421                 case PAM_PROMPT_ECHO_OFF:
 422                 case PAM_PROMPT_ECHO_ON:
 423                         if ((r = sshbuf_put_cstring(buffer,
 424                             PAM_MSG_MEMBER(msg, i, msg))) != 0)
 425                                 fatal("%s: buffer error: %s",
 426                                     __func__, ssh_err(r));
 427                         if (ssh_msg_send(ctxt->pam_csock,
 428                             PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
 429                                 goto fail;
 430
 431                         if (ssh_msg_recv(ctxt->pam_csock, buffer) == -1)
 432                                 goto fail;
 433                         if ((r = sshbuf_get_u8(buffer, &status)) != 0)
 434                                 fatal("%s: buffer error: %s",
 435                                     __func__, ssh_err(r));
 436                         if (status != PAM_AUTHTOK)
 437                                 goto fail;
 438                         if ((r = sshbuf_get_cstring(buffer,
 439                             &reply[i].resp, NULL)) != 0)
 440                                 fatal("%s: buffer error: %s",
 441                                     __func__, ssh_err(r));
 442                         break;
 443                 case PAM_ERROR_MSG:
 444                 case PAM_TEXT_INFO:
 445                         if ((r = sshbuf_put_cstring(buffer,
 446                             PAM_MSG_MEMBER(msg, i, msg))) != 0)
 447                                 fatal("%s: buffer error: %s",
 448                                     __func__, ssh_err(r));
 449                         if (ssh_msg_send(ctxt->pam_csock,
 450                             PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
 451                                 goto fail;
 452                         break;
 453                 default:
 454                         goto fail;
 455                 }
 456                 sshbuf_reset(buffer);
 457         }
 458         sshbuf_free(buffer);
 459         *resp = reply;
 460         return (PAM_SUCCESS);
 461
 462  fail:
 463         for(i = 0; i < n; i++) {
 464                 free(reply[i].resp);
 465         }
 466         free(reply);
 467         sshbuf_free(buffer);
 468         return (PAM_CONV_ERR);
 469 }
 470
 471 /*
 472  * Authentication thread.
 473  */
 474 static void *
 475 sshpam_thread(void *ctxtp)
 476 {
 477         struct pam_ctxt *ctxt = ctxtp;
 478         struct sshbuf *buffer = NULL;
 479         struct pam_conv sshpam_conv;
 480         int r, flags = (options.permit_empty_passwd == 0 ?
 481             PAM_DISALLOW_NULL_AUTHTOK : 0);
 482 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 483         extern char **environ;
 484         char **env_from_pam;
 485         u_int i;
 486         const char *pam_user;
 487         const char **ptr_pam_user = &pam_user;
 488         char *tz = getenv("TZ");
 489
 490         sshpam_err = pam_get_item(sshpam_handle, PAM_USER,
 491             (sshpam_const void **)ptr_pam_user);
 492         if (sshpam_err != PAM_SUCCESS)
 493                 goto auth_fail;
 494
 495         environ[0] = NULL;
 496         if (tz != NULL)
 497                 if (setenv("TZ", tz, 1) == -1)
 498                         error("PAM: could not set TZ environment: %s",
 499                             strerror(errno));
 500
 501         if (sshpam_authctxt != NULL) {
 502                 setproctitle("%s [pam]",
 503                     sshpam_authctxt->valid ? pam_user : "unknown");
 504         }
 505 #endif
 506
 507         sshpam_conv.conv = sshpam_thread_conv;
 508         sshpam_conv.appdata_ptr = ctxt;
 509
 510         if (sshpam_authctxt == NULL)
 511                 fatal("%s: PAM authctxt not initialized", __func__);
 512
 513         if ((buffer = sshbuf_new()) == NULL)
 514                 fatal("%s: sshbuf_new failed", __func__);
 515
 516         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 517             (const void *)&sshpam_conv);
 518         if (sshpam_err != PAM_SUCCESS)
 519                 goto auth_fail;
 520         sshpam_err = pam_authenticate(sshpam_handle, flags);
 521         if (sshpam_err == PAM_MAXTRIES)
 522                 sshpam_set_maxtries_reached(1);
 523         if (sshpam_err != PAM_SUCCESS)
 524                 goto auth_fail;
 525
 526         if (!do_pam_account()) {
 527                 sshpam_err = PAM_ACCT_EXPIRED;
 528                 goto auth_fail;
 529         }
 530         if (sshpam_authctxt->force_pwchange) {
 531                 sshpam_err = pam_chauthtok(sshpam_handle,
 532                     PAM_CHANGE_EXPIRED_AUTHTOK);
 533                 if (sshpam_err != PAM_SUCCESS)
 534                         goto auth_fail;
 535                 sshpam_password_change_required(0);
 536         }
 537
 538         if ((r = sshbuf_put_cstring(buffer, "OK")) != 0)
 539                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 540
 541 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 542         /* Export variables set by do_pam_account */
 543         if ((r = sshbuf_put_u32(buffer, sshpam_account_status)) != 0 ||
 544             (r = sshbuf_put_u32(buffer, sshpam_authctxt->force_pwchange)) != 0)
 545                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 546
 547         /* Export any environment strings set in child */
 548         for (i = 0; environ[i] != NULL; i++) {
 549                 /* Count */
 550                 if (i > INT_MAX)
 551                         fatal("%s: too many environment strings", __func__);
 552         }
 553         if ((r = sshbuf_put_u32(buffer, i)) != 0)
 554                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 555         for (i = 0; environ[i] != NULL; i++) {
 556                 if ((r = sshbuf_put_cstring(buffer, environ[i])) != 0)
 557                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 558         }
 559         /* Export any environment strings set by PAM in child */
 560         env_from_pam = pam_getenvlist(sshpam_handle);
 561         for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
 562                 /* Count */
 563                 if (i > INT_MAX)
 564                         fatal("%s: too many PAM environment strings", __func__);
 565         }
 566         if ((r = sshbuf_put_u32(buffer, i)) != 0)
 567                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 568         for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
 569                 if ((r = sshbuf_put_cstring(buffer, env_from_pam[i])) != 0)
 570                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 571         }
 572 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 573
 574         /* XXX - can't do much about an error here */
 575         ssh_msg_send(ctxt->pam_csock, sshpam_err, buffer);
 576         sshbuf_free(buffer);
 577         pthread_exit(NULL);
 578
 579  auth_fail:
 580         if ((r = sshbuf_put_cstring(buffer,
 581             pam_strerror(sshpam_handle, sshpam_err))) != 0)
 582                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 583         /* XXX - can't do much about an error here */
 584         if (sshpam_err == PAM_ACCT_EXPIRED)
 585                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, buffer);
 586         else if (sshpam_maxtries_reached)
 587                 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, buffer);
 588         else
 589                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, buffer);
 590         sshbuf_free(buffer);
 591         pthread_exit(NULL);
 592
 593         return (NULL); /* Avoid warning for non-pthread case */
 594 }
 595
 596 void
 597 sshpam_thread_cleanup(void)
 598 {
 599         struct pam_ctxt *ctxt = cleanup_ctxt;
 600
 601         debug3("PAM: %s entering", __func__);
 602         if (ctxt != NULL && ctxt->pam_thread != 0) {
 603                 pthread_cancel(ctxt->pam_thread);
 604                 pthread_join(ctxt->pam_thread, NULL);
 605                 close(ctxt->pam_psock);
 606                 close(ctxt->pam_csock);
 607                 memset(ctxt, 0, sizeof(*ctxt));
 608                 cleanup_ctxt = NULL;
 609         }
 610 }
 611
 612 static int
 613 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 614     struct pam_response **resp, void *data)
 615 {
 616         debug3("PAM: %s entering, %d messages", __func__, n);
 617         return (PAM_CONV_ERR);
 618 }
 619
 620 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 621
 622 static int
 623 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 624     struct pam_response **resp, void *data)
 625 {
 626         struct pam_response *reply;
 627         int r, i;
 628
 629         debug3("PAM: %s called with %d messages", __func__, n);
 630         *resp = NULL;
 631
 632         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 633                 return (PAM_CONV_ERR);
 634
 635         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 636                 return (PAM_CONV_ERR);
 637
 638         for (i = 0; i < n; ++i) {
 639                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 640                 case PAM_ERROR_MSG:
 641                 case PAM_TEXT_INFO:
 642                         if ((r = sshbuf_putf(loginmsg, "%s\n",
 643                             PAM_MSG_MEMBER(msg, i, msg))) != 0)
 644                                 fatal("%s: buffer error: %s",
 645                                     __func__, ssh_err(r));
 646                         reply[i].resp_retcode = PAM_SUCCESS;
 647                         break;
 648                 default:
 649                         goto fail;
 650                 }
 651         }
 652         *resp = reply;
 653         return (PAM_SUCCESS);
 654
 655  fail:
 656         for(i = 0; i < n; i++) {
 657                 free(reply[i].resp);
 658         }
 659         free(reply);
 660         return (PAM_CONV_ERR);
 661 }
 662
 663 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 664
 665 void
 666 sshpam_cleanup(void)
 667 {
 668         if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor()))
 669                 return;
 670         debug("PAM: cleanup");
 671         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 672         if (sshpam_session_open) {
 673                 debug("PAM: closing session");
 674                 pam_close_session(sshpam_handle, PAM_SILENT);
 675                 sshpam_session_open = 0;
 676         }
 677         if (sshpam_cred_established) {
 678                 debug("PAM: deleting credentials");
 679                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 680                 sshpam_cred_established = 0;
 681         }
 682         sshpam_authenticated = 0;
 683         pam_end(sshpam_handle, sshpam_err);
 684         sshpam_handle = NULL;
 685 }
 686
 687 static int
 688 sshpam_init(struct ssh *ssh, Authctxt *authctxt)
 689 {
 690         const char *pam_user, *user = authctxt->user;
 691         const char **ptr_pam_user = &pam_user;
 692
 693 #if defined(PAM_SUN_CODEBASE) && defined(PAM_MAX_RESP_SIZE)
 694         /* Protect buggy PAM implementations from excessively long usernames */
 695         if (strlen(user) >= PAM_MAX_RESP_SIZE)
 696                 fatal("Username too long from %s port %d",
 697                     ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 698 #endif
 699         if (sshpam_handle == NULL) {
 700                 if (ssh == NULL) {
 701                         fatal("%s: called initially with no "
 702                             "packet context", __func__);
 703                 }
 704         } if (sshpam_handle != NULL) {
 705                 /* We already have a PAM context; check if the user matches */
 706                 sshpam_err = pam_get_item(sshpam_handle,
 707                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 708                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 709                         return (0);
 710                 pam_end(sshpam_handle, sshpam_err);
 711                 sshpam_handle = NULL;
 712         }
 713         debug("PAM: initializing for \"%s\"", user);
 714         sshpam_err =
 715             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 716         sshpam_authctxt = authctxt;
 717
 718         if (sshpam_err != PAM_SUCCESS) {
 719                 pam_end(sshpam_handle, sshpam_err);
 720                 sshpam_handle = NULL;
 721                 return (-1);
 722         }
 723
 724         if (ssh != NULL && sshpam_rhost == NULL) {
 725                 /*
 726                  * We need to cache these as we don't have packet context
 727                  * during the kbdint flow.
 728                  */
 729                 sshpam_rhost = xstrdup(auth_get_canonical_hostname(ssh,
 730                     options.use_dns));
 731                 sshpam_laddr = get_local_ipaddr(
 732                     ssh_packet_get_connection_in(ssh));
 733                 xasprintf(&sshpam_conninfo, "SSH_CONNECTION=%.50s %d %.50s %d",
 734                     ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
 735                     sshpam_laddr, ssh_local_port(ssh));
 736         }
 737         if (sshpam_rhost != NULL) {
 738                 debug("PAM: setting PAM_RHOST to \"%s\"", sshpam_rhost);
 739                 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST,
 740                     sshpam_rhost);
 741                 if (sshpam_err != PAM_SUCCESS) {
 742                         pam_end(sshpam_handle, sshpam_err);
 743                         sshpam_handle = NULL;
 744                         return (-1);
 745                 }
 746                 /* Put SSH_CONNECTION in the PAM environment too */
 747                 pam_putenv(sshpam_handle, sshpam_conninfo);
 748         }
 749
 750 #ifdef PAM_TTY_KLUDGE
 751         /*
 752          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 753          * sshd doesn't set the tty until too late in the auth process and
 754          * may not even set one (for tty-less connections)
 755          */
 756         debug("PAM: setting PAM_TTY to \"ssh\"");
 757         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 758         if (sshpam_err != PAM_SUCCESS) {
 759                 pam_end(sshpam_handle, sshpam_err);
 760                 sshpam_handle = NULL;
 761                 return (-1);
 762         }
 763 #endif
 764         return (0);
 765 }
 766
 767 static void
 768 expose_authinfo(const char *caller)
 769 {
 770         char *auth_info;
 771
 772         /*
 773          * Expose authentication information to PAM.
 774          * The environment variable is versioned. Please increment the
 775          * version suffix if the format of session_info changes.
 776          */
 777         if (sshpam_authctxt->session_info == NULL)
 778                 auth_info = xstrdup("");
 779         else if ((auth_info = sshbuf_dup_string(
 780             sshpam_authctxt->session_info)) == NULL)
 781                 fatal("%s: sshbuf_dup_string failed", __func__);
 782
 783         debug2("%s: auth information in SSH_AUTH_INFO_0", caller);
 784         do_pam_putenv("SSH_AUTH_INFO_0", auth_info);
 785         free(auth_info);
 786 }
 787
 788 static void *
 789 sshpam_init_ctx(Authctxt *authctxt)
 790 {
 791         struct pam_ctxt *ctxt;
 792         int result, socks[2];
 793
 794         debug3("PAM: %s entering", __func__);
 795         /*
 796          * Refuse to start if we don't have PAM enabled or do_pam_account
 797          * has previously failed.
 798          */
 799         if (!options.use_pam || sshpam_account_status == 0)
 800                 return NULL;
 801
 802         /* Initialize PAM */
 803         if (sshpam_init(NULL, authctxt) == -1) {
 804                 error("PAM: initialization failed");
 805                 return (NULL);
 806         }
 807
 808         expose_authinfo(__func__);
 809         ctxt = xcalloc(1, sizeof *ctxt);
 810
 811         /* Start the authentication thread */
 812         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 813                 error("PAM: failed create sockets: %s", strerror(errno));
 814                 free(ctxt);
 815                 return (NULL);
 816         }
 817         ctxt->pam_psock = socks[0];
 818         ctxt->pam_csock = socks[1];
 819         result = pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt);
 820         if (result != 0) {
 821                 error("PAM: failed to start authentication thread: %s",
 822                     strerror(result));
 823                 close(socks[0]);
 824                 close(socks[1]);
 825                 free(ctxt);
 826                 return (NULL);
 827         }
 828         cleanup_ctxt = ctxt;
 829         return (ctxt);
 830 }
 831
 832 static int
 833 sshpam_query(void *ctx, char **name, char **info,
 834     u_int *num, char ***prompts, u_int **echo_on)
 835 {
 836         struct sshbuf *buffer;
 837         struct pam_ctxt *ctxt = ctx;
 838         size_t plen;
 839         u_char type;
 840         char *msg;
 841         size_t len, mlen;
 842         int r;
 843
 844         debug3("PAM: %s entering", __func__);
 845         if ((buffer = sshbuf_new()) == NULL)
 846                 fatal("%s: sshbuf_new failed", __func__);
 847         *name = xstrdup("");
 848         *info = xstrdup("");
 849         *prompts = xmalloc(sizeof(char *));
 850         **prompts = NULL;
 851         plen = 0;
 852         *echo_on = xmalloc(sizeof(u_int));
 853         while (ssh_msg_recv(ctxt->pam_psock, buffer) == 0) {
 854                 if ((r = sshbuf_get_u8(buffer, &type)) != 0 ||
 855                     (r = sshbuf_get_cstring(buffer, &msg, &mlen)) != 0)
 856                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 857                 switch (type) {
 858                 case PAM_PROMPT_ECHO_ON:
 859                 case PAM_PROMPT_ECHO_OFF:
 860                         *num = 1;
 861                         len = plen + mlen + 1;
 862                         **prompts = xreallocarray(**prompts, 1, len);
 863                         strlcpy(**prompts + plen, msg, len - plen);
 864                         plen += mlen;
 865                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 866                         free(msg);
 867                         sshbuf_free(buffer);
 868                         return (0);
 869                 case PAM_ERROR_MSG:
 870                 case PAM_TEXT_INFO:
 871                         /* accumulate messages */
 872                         len = plen + mlen + 2;
 873                         **prompts = xreallocarray(**prompts, 1, len);
 874                         strlcpy(**prompts + plen, msg, len - plen);
 875                         plen += mlen;
 876                         strlcat(**prompts + plen, "\n", len - plen);
 877                         plen++;
 878                         free(msg);
 879                         break;
 880                 case PAM_ACCT_EXPIRED:
 881                 case PAM_MAXTRIES:
 882                         if (type == PAM_ACCT_EXPIRED)
 883                                 sshpam_account_status = 0;
 884                         if (type == PAM_MAXTRIES)
 885                                 sshpam_set_maxtries_reached(1);
 886                         /* FALLTHROUGH */
 887                 case PAM_AUTH_ERR:
 888                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 889                         if (**prompts != NULL && strlen(**prompts) != 0) {
 890                                 *info = **prompts;
 891                                 **prompts = NULL;
 892                                 *num = 0;
 893                                 **echo_on = 0;
 894                                 ctxt->pam_done = -1;
 895                                 free(msg);
 896                                 sshbuf_free(buffer);
 897                                 return 0;
 898                         }
 899                         /* FALLTHROUGH */
 900                 case PAM_SUCCESS:
 901                         if (**prompts != NULL) {
 902                                 /* drain any accumulated messages */
 903                                 debug("PAM: %s", **prompts);
 904                                 if ((r = sshbuf_put(loginmsg, **prompts,
 905                                     strlen(**prompts))) != 0)
 906                                         fatal("%s: buffer error: %s",
 907                                             __func__, ssh_err(r));
 908                                 free(**prompts);
 909                                 **prompts = NULL;
 910                         }
 911                         if (type == PAM_SUCCESS) {
 912                                 if (!sshpam_authctxt->valid ||
 913                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 914                                     options.permit_root_login != PERMIT_YES))
 915                                         fatal("Internal error: PAM auth "
 916                                             "succeeded when it should have "
 917                                             "failed");
 918                                 import_environments(buffer);
 919                                 *num = 0;
 920                                 **echo_on = 0;
 921                                 ctxt->pam_done = 1;
 922                                 free(msg);
 923                                 sshbuf_free(buffer);
 924                                 return (0);
 925                         }
 926                         BLACKLIST_NOTIFY(NULL, BLACKLIST_BAD_USER,
 927                             sshpam_authctxt->user);
 928                         error("PAM: %s for %s%.100s from %.100s", msg,
 929                             sshpam_authctxt->valid ? "" : "illegal user ",
 930                             sshpam_authctxt->user, sshpam_rhost);
 931                         /* FALLTHROUGH */
 932                 default:
 933                         *num = 0;
 934                         **echo_on = 0;
 935                         free(msg);
 936                         ctxt->pam_done = -1;
 937                         sshbuf_free(buffer);
 938                         return (-1);
 939                 }
 940         }
 941         sshbuf_free(buffer);
 942         return (-1);
 943 }
 944
 945 /*
 946  * Returns a junk password of identical length to that the user supplied.
 947  * Used to mitigate timing attacks against crypt(3)/PAM stacks that
 948  * vary processing time in proportion to password length.
 949  */
 950 static char *
 951 fake_password(const char *wire_password)
 952 {
 953         const char junk[] = "\b\n\r\177INCORRECT";
 954         char *ret = NULL;
 955         size_t i, l = wire_password != NULL ? strlen(wire_password) : 0;
 956
 957         if (l >= INT_MAX)
 958                 fatal("%s: password length too long: %zu", __func__, l);
 959
 960         ret = malloc(l + 1);
 961         if (ret == NULL)
 962                 return NULL;
 963         for (i = 0; i < l; i++)
 964                 ret[i] = junk[i % (sizeof(junk) - 1)];
 965         ret[i] = '\0';
 966         return ret;
 967 }
 968
 969 /* XXX - see also comment in auth-chall.c:verify_response */
 970 static int
 971 sshpam_respond(void *ctx, u_int num, char **resp)
 972 {
 973         struct sshbuf *buffer;
 974         struct pam_ctxt *ctxt = ctx;
 975         char *fake;
 976         int r;
 977
 978         debug2("PAM: %s entering, %u responses", __func__, num);
 979         switch (ctxt->pam_done) {
 980         case 1:
 981                 sshpam_authenticated = 1;
 982                 return (0);
 983         case 0:
 984                 break;
 985         default:
 986                 return (-1);
 987         }
 988         if (num != 1) {
 989                 error("PAM: expected one response, got %u", num);
 990                 return (-1);
 991         }
 992         if ((buffer = sshbuf_new()) == NULL)
 993                 fatal("%s: sshbuf_new failed", __func__);
 994         if (sshpam_authctxt->valid &&
 995             (sshpam_authctxt->pw->pw_uid != 0 ||
 996             options.permit_root_login == PERMIT_YES)) {
 997                 if ((r = sshbuf_put_cstring(buffer, *resp)) != 0)
 998                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 999         } else {
1000                 fake = fake_password(*resp);
1001                 if ((r = sshbuf_put_cstring(buffer, fake)) != 0)
1002                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
1003                 free(fake);
1004         }
1005         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, buffer) == -1) {
1006                 sshbuf_free(buffer);
1007                 return (-1);
1008         }
1009         sshbuf_free(buffer);
1010         return (1);
1011 }
1012
1013 static void
1014 sshpam_free_ctx(void *ctxtp)
1015 {
1016         struct pam_ctxt *ctxt = ctxtp;
1017
1018         debug3("PAM: %s entering", __func__);
1019         sshpam_thread_cleanup();
1020         free(ctxt);
1021         /*
1022          * We don't call sshpam_cleanup() here because we may need the PAM
1023          * handle at a later stage, e.g. when setting up a session.  It's
1024          * still on the cleanup list, so pam_end() *will* be called before
1025          * the server process terminates.
1026          */
1027 }
1028
1029 KbdintDevice sshpam_device = {
1030         "pam",
1031         sshpam_init_ctx,
1032         sshpam_query,
1033         sshpam_respond,
1034         sshpam_free_ctx
1035 };
1036
1037 KbdintDevice mm_sshpam_device = {
1038         "pam",
1039         mm_sshpam_init_ctx,
1040         mm_sshpam_query,
1041         mm_sshpam_respond,
1042         mm_sshpam_free_ctx
1043 };
1044
1045 /*
1046  * This replaces auth-pam.c
1047  */
1048 void
1049 start_pam(struct ssh *ssh)
1050 {
1051         Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1052
1053         if (!options.use_pam)
1054                 fatal("PAM: initialisation requested when UsePAM=no");
1055
1056         if (sshpam_init(ssh, authctxt) == -1)
1057                 fatal("PAM: initialisation failed");
1058 }
1059
1060 void
1061 finish_pam(void)
1062 {
1063         sshpam_cleanup();
1064 }
1065
1066
1067 u_int
1068 do_pam_account(void)
1069 {
1070         debug("%s: called", __func__);
1071         if (sshpam_account_status != -1)
1072                 return (sshpam_account_status);
1073
1074         expose_authinfo(__func__);
1075
1076         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
1077         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
1078             pam_strerror(sshpam_handle, sshpam_err));
1079
1080         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
1081                 sshpam_account_status = 0;
1082                 return (sshpam_account_status);
1083         }
1084
1085         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
1086                 sshpam_password_change_required(1);
1087
1088         sshpam_account_status = 1;
1089         return (sshpam_account_status);
1090 }
1091
1092 void
1093 do_pam_setcred(int init)
1094 {
1095         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1096             (const void *)&store_conv);
1097         if (sshpam_err != PAM_SUCCESS)
1098                 fatal("PAM: failed to set PAM_CONV: %s",
1099                     pam_strerror(sshpam_handle, sshpam_err));
1100         if (init) {
1101                 debug("PAM: establishing credentials");
1102                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
1103         } else {
1104                 debug("PAM: reinitializing credentials");
1105                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
1106         }
1107         if (sshpam_err == PAM_SUCCESS) {
1108                 sshpam_cred_established = 1;
1109                 return;
1110         }
1111         if (sshpam_authenticated)
1112                 fatal("PAM: pam_setcred(): %s",
1113                     pam_strerror(sshpam_handle, sshpam_err));
1114         else
1115                 debug("PAM: pam_setcred(): %s",
1116                     pam_strerror(sshpam_handle, sshpam_err));
1117 }
1118
1119 static int
1120 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
1121     struct pam_response **resp, void *data)
1122 {
1123         char input[PAM_MAX_MSG_SIZE];
1124         struct pam_response *reply;
1125         int i;
1126
1127         debug3("PAM: %s called with %d messages", __func__, n);
1128
1129         *resp = NULL;
1130
1131         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
1132                 return (PAM_CONV_ERR);
1133
1134         if ((reply = calloc(n, sizeof(*reply))) == NULL)
1135                 return (PAM_CONV_ERR);
1136
1137         for (i = 0; i < n; ++i) {
1138                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1139                 case PAM_PROMPT_ECHO_OFF:
1140                         reply[i].resp =
1141                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
1142                             RP_ALLOW_STDIN);
1143                         reply[i].resp_retcode = PAM_SUCCESS;
1144                         break;
1145                 case PAM_PROMPT_ECHO_ON:
1146                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
1147                         if (fgets(input, sizeof input, stdin) == NULL)
1148                                 input[0] = '\0';
1149                         if ((reply[i].resp = strdup(input)) == NULL)
1150                                 goto fail;
1151                         reply[i].resp_retcode = PAM_SUCCESS;
1152                         break;
1153                 case PAM_ERROR_MSG:
1154                 case PAM_TEXT_INFO:
1155                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
1156                         reply[i].resp_retcode = PAM_SUCCESS;
1157                         break;
1158                 default:
1159                         goto fail;
1160                 }
1161         }
1162         *resp = reply;
1163         return (PAM_SUCCESS);
1164
1165  fail:
1166         for(i = 0; i < n; i++) {
1167                 free(reply[i].resp);
1168         }
1169         free(reply);
1170         return (PAM_CONV_ERR);
1171 }
1172
1173 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1174
1175 /*
1176  * XXX this should be done in the authentication phase, but ssh1 doesn't
1177  * support that
1178  */
1179 void
1180 do_pam_chauthtok(void)
1181 {
1182         if (use_privsep)
1183                 fatal("Password expired (unable to change with privsep)");
1184         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1185             (const void *)&tty_conv);
1186         if (sshpam_err != PAM_SUCCESS)
1187                 fatal("PAM: failed to set PAM_CONV: %s",
1188                     pam_strerror(sshpam_handle, sshpam_err));
1189         debug("PAM: changing password");
1190         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1191         if (sshpam_err != PAM_SUCCESS)
1192                 fatal("PAM: pam_chauthtok(): %s",
1193                     pam_strerror(sshpam_handle, sshpam_err));
1194 }
1195
1196 void
1197 do_pam_session(struct ssh *ssh)
1198 {
1199         debug3("PAM: opening session");
1200
1201         expose_authinfo(__func__);
1202
1203         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1204             (const void *)&store_conv);
1205         if (sshpam_err != PAM_SUCCESS)
1206                 fatal("PAM: failed to set PAM_CONV: %s",
1207                     pam_strerror(sshpam_handle, sshpam_err));
1208         sshpam_err = pam_open_session(sshpam_handle, 0);
1209         if (sshpam_err == PAM_SUCCESS)
1210                 sshpam_session_open = 1;
1211         else {
1212                 sshpam_session_open = 0;
1213                 auth_restrict_session(ssh);
1214                 error("PAM: pam_open_session(): %s",
1215                     pam_strerror(sshpam_handle, sshpam_err));
1216         }
1217
1218 }
1219
1220 int
1221 is_pam_session_open(void)
1222 {
1223         return sshpam_session_open;
1224 }
1225
1226 /*
1227  * Set a PAM environment string. We need to do this so that the session
1228  * modules can handle things like Kerberos/GSI credentials that appear
1229  * during the ssh authentication process.
1230  */
1231 int
1232 do_pam_putenv(char *name, char *value)
1233 {
1234         int ret = 1;
1235         char *compound;
1236         size_t len;
1237
1238         len = strlen(name) + strlen(value) + 2;
1239         compound = xmalloc(len);
1240
1241         snprintf(compound, len, "%s=%s", name, value);
1242         ret = pam_putenv(sshpam_handle, compound);
1243         free(compound);
1244
1245         return (ret);
1246 }
1247
1248 char **
1249 fetch_pam_child_environment(void)
1250 {
1251         return sshpam_env;
1252 }
1253
1254 char **
1255 fetch_pam_environment(void)
1256 {
1257         return (pam_getenvlist(sshpam_handle));
1258 }
1259
1260 void
1261 free_pam_environment(char **env)
1262 {
1263         char **envp;
1264
1265         if (env == NULL)
1266                 return;
1267
1268         for (envp = env; *envp; envp++)
1269                 free(*envp);
1270         free(env);
1271 }
1272
1273 /*
1274  * "Blind" conversation function for password authentication.  Assumes that
1275  * echo-off prompts are for the password and stores messages for later
1276  * display.
1277  */
1278 static int
1279 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1280     struct pam_response **resp, void *data)
1281 {
1282         struct pam_response *reply;
1283         int r, i;
1284         size_t len;
1285
1286         debug3("PAM: %s called with %d messages", __func__, n);
1287
1288         *resp = NULL;
1289
1290         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1291                 return (PAM_CONV_ERR);
1292
1293         if ((reply = calloc(n, sizeof(*reply))) == NULL)
1294                 return (PAM_CONV_ERR);
1295
1296         for (i = 0; i < n; ++i) {
1297                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1298                 case PAM_PROMPT_ECHO_OFF:
1299                         if (sshpam_password == NULL)
1300                                 goto fail;
1301                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1302                                 goto fail;
1303                         reply[i].resp_retcode = PAM_SUCCESS;
1304                         break;
1305                 case PAM_ERROR_MSG:
1306                 case PAM_TEXT_INFO:
1307                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1308                         if (len > 0) {
1309                                 if ((r = sshbuf_putf(loginmsg, "%s\n",
1310                                     PAM_MSG_MEMBER(msg, i, msg))) != 0)
1311                                         fatal("%s: buffer error: %s",
1312                                             __func__, ssh_err(r));
1313                         }
1314                         if ((reply[i].resp = strdup("")) == NULL)
1315                                 goto fail;
1316                         reply[i].resp_retcode = PAM_SUCCESS;
1317                         break;
1318                 default:
1319                         goto fail;
1320                 }
1321         }
1322         *resp = reply;
1323         return (PAM_SUCCESS);
1324
1325  fail:
1326         for(i = 0; i < n; i++) {
1327                 free(reply[i].resp);
1328         }
1329         free(reply);
1330         return (PAM_CONV_ERR);
1331 }
1332
1333 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1334
1335 /*
1336  * Attempt password authentication via PAM
1337  */
1338 int
1339 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1340 {
1341         int flags = (options.permit_empty_passwd == 0 ?
1342             PAM_DISALLOW_NULL_AUTHTOK : 0);
1343         char *fake = NULL;
1344
1345         if (!options.use_pam || sshpam_handle == NULL)
1346                 fatal("PAM: %s called when PAM disabled or failed to "
1347                     "initialise.", __func__);
1348
1349         sshpam_password = password;
1350         sshpam_authctxt = authctxt;
1351
1352         /*
1353          * If the user logging in is invalid, or is root but is not permitted
1354          * by PermitRootLogin, use an invalid password to prevent leaking
1355          * information via timing (eg if the PAM config has a delay on fail).
1356          */
1357         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1358             options.permit_root_login != PERMIT_YES))
1359                 sshpam_password = fake = fake_password(password);
1360
1361         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1362             (const void *)&passwd_conv);
1363         if (sshpam_err != PAM_SUCCESS)
1364                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1365                     pam_strerror(sshpam_handle, sshpam_err));
1366
1367         sshpam_err = pam_authenticate(sshpam_handle, flags);
1368         sshpam_password = NULL;
1369         free(fake);
1370         if (sshpam_err == PAM_MAXTRIES)
1371                 sshpam_set_maxtries_reached(1);
1372         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1373                 debug("PAM: password authentication accepted for %.100s",
1374                     authctxt->user);
1375                 return 1;
1376         } else {
1377                 debug("PAM: password authentication failed for %.100s: %s",
1378                     authctxt->valid ? authctxt->user : "an illegal user",
1379                     pam_strerror(sshpam_handle, sshpam_err));
1380                 return 0;
1381         }
1382 }
1383
1384 int
1385 sshpam_get_maxtries_reached(void)
1386 {
1387         return sshpam_maxtries_reached;
1388 }
1389
1390 void
1391 sshpam_set_maxtries_reached(int reached)
1392 {
1393         if (reached == 0 || sshpam_maxtries_reached)
1394                 return;
1395         sshpam_maxtries_reached = 1;
1396         options.password_authentication = 0;
1397         options.kbd_interactive_authentication = 0;
1398 }
1399 #endif /* USE_PAM */