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
 257 /* Some PAM implementations don't implement this */
 258 #ifndef HAVE_PAM_GETENVLIST
 259 static char **
 260 pam_getenvlist(pam_handle_t *pamh)
 261 {
 262         /*
 263          * XXX - If necessary, we can still support environment passing
 264          * for platforms without pam_getenvlist by searching for known
 265          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 266          */
 267          return NULL;
 268 }
 269 #endif
 270
 271 #ifndef HAVE_PAM_PUTENV
 272 static int
 273 pam_putenv(pam_handle_t *pamh, const char *name_value)
 274 {
 275         return PAM_SUCCESS;
 276 }
 277 #endif /* HAVE_PAM_PUTENV */
 278
 279 /*
 280  * Some platforms, notably Solaris, do not enforce password complexity
 281  * rules during pam_chauthtok() if the real uid of the calling process
 282  * is 0, on the assumption that it's being called by "passwd" run by root.
 283  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 284  * the right thing.
 285  */
 286 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 287 static int
 288 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 289 {
 290         int result;
 291
 292         if (sshpam_authctxt == NULL)
 293                 fatal("PAM: sshpam_authctxt not initialized");
 294         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 295                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 296         result = pam_chauthtok(pamh, flags);
 297         if (setreuid(0, -1) == -1)
 298                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 299         return result;
 300 }
 301 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 302 #endif
 303
 304 static void
 305 sshpam_password_change_required(int reqd)
 306 {
 307         extern struct sshauthopt *auth_opts;
 308         static int saved_port, saved_agent, saved_x11;
 309
 310         debug3("%s %d", __func__, reqd);
 311         if (sshpam_authctxt == NULL)
 312                 fatal("%s: PAM authctxt not initialized", __func__);
 313         sshpam_authctxt->force_pwchange = reqd;
 314         if (reqd) {
 315                 saved_port = auth_opts->permit_port_forwarding_flag;
 316                 saved_agent = auth_opts->permit_agent_forwarding_flag;
 317                 saved_x11 = auth_opts->permit_x11_forwarding_flag;
 318                 auth_opts->permit_port_forwarding_flag = 0;
 319                 auth_opts->permit_agent_forwarding_flag = 0;
 320                 auth_opts->permit_x11_forwarding_flag = 0;
 321         } else {
 322                 if (saved_port)
 323                         auth_opts->permit_port_forwarding_flag = saved_port;
 324                 if (saved_agent)
 325                         auth_opts->permit_agent_forwarding_flag = saved_agent;
 326                 if (saved_x11)
 327                         auth_opts->permit_x11_forwarding_flag = saved_x11;
 328         }
 329 }
 330
 331 /* Import regular and PAM environment from subprocess */
 332 static void
 333 import_environments(struct sshbuf *b)
 334 {
 335         char *env;
 336         u_int n, i, num_env;
 337         int r;
 338
 339         debug3("PAM: %s entering", __func__);
 340
 341 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 342         /* Import variables set by do_pam_account */
 343         if ((r = sshbuf_get_u32(b, &n)) != 0)
 344                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 345         if (n > INT_MAX)
 346                 fatal("%s: invalid PAM account status %u", __func__, n);
 347         sshpam_account_status = (int)n;
 348         if ((r = sshbuf_get_u32(b, &n)) != 0)
 349                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 350         sshpam_password_change_required(n != 0);
 351
 352         /* Import environment from subprocess */
 353         if ((r = sshbuf_get_u32(b, &num_env)) != 0)
 354                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 355         if (num_env > 1024) {
 356                 fatal_f("received %u environment variables, expected <= 1024",
 357                     num_env);
 358         }
 359         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 360         debug3("PAM: num env strings %u", 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         if (num_env > 1024) {
 371                 fatal_f("received %u PAM env variables, expected <= 1024",
 372                     num_env);
 373         }
 374         debug("PAM: num PAM env strings %u", num_env);
 375         for (i = 0; i < num_env; i++) {
 376                 if ((r = sshbuf_get_cstring(b, &env, NULL)) != 0)
 377                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 378                 /* Errors are not fatal here */
 379                 if ((r = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 380                         error("PAM: pam_putenv: %s",
 381                             pam_strerror(sshpam_handle, r));
 382                 }
 383                 /*
 384                  * XXX this possibly leaks env because it is not documented
 385                  * what pam_putenv() does with it. Does it copy it? Does it
 386                  * take ownweship? We don't know, so it's safest just to leak.
 387                  */
 388         }
 389 #endif
 390 }
 391
 392 /*
 393  * Conversation function for authentication thread.
 394  */
 395 static int
 396 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 397     struct pam_response **resp, void *data)
 398 {
 399         struct sshbuf *buffer;
 400         struct pam_ctxt *ctxt;
 401         struct pam_response *reply;
 402         int r, i;
 403         u_char status;
 404
 405         debug3("PAM: %s entering, %d messages", __func__, n);
 406         *resp = NULL;
 407
 408         if (data == NULL) {
 409                 error("PAM: conversation function passed a null context");
 410                 return (PAM_CONV_ERR);
 411         }
 412         ctxt = data;
 413         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 414                 return (PAM_CONV_ERR);
 415
 416         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 417                 return PAM_CONV_ERR;
 418         if ((buffer = sshbuf_new()) == NULL) {
 419                 free(reply);
 420                 return PAM_CONV_ERR;
 421         }
 422
 423         for (i = 0; i < n; ++i) {
 424                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 425                 case PAM_PROMPT_ECHO_OFF:
 426                 case PAM_PROMPT_ECHO_ON:
 427                         if ((r = sshbuf_put_cstring(buffer,
 428                             PAM_MSG_MEMBER(msg, i, msg))) != 0)
 429                                 fatal("%s: buffer error: %s",
 430                                     __func__, ssh_err(r));
 431                         if (ssh_msg_send(ctxt->pam_csock,
 432                             PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
 433                                 goto fail;
 434
 435                         if (ssh_msg_recv(ctxt->pam_csock, buffer) == -1)
 436                                 goto fail;
 437                         if ((r = sshbuf_get_u8(buffer, &status)) != 0)
 438                                 fatal("%s: buffer error: %s",
 439                                     __func__, ssh_err(r));
 440                         if (status != PAM_AUTHTOK)
 441                                 goto fail;
 442                         if ((r = sshbuf_get_cstring(buffer,
 443                             &reply[i].resp, NULL)) != 0)
 444                                 fatal("%s: buffer error: %s",
 445                                     __func__, ssh_err(r));
 446                         break;
 447                 case PAM_ERROR_MSG:
 448                 case PAM_TEXT_INFO:
 449                         if ((r = sshbuf_put_cstring(buffer,
 450                             PAM_MSG_MEMBER(msg, i, msg))) != 0)
 451                                 fatal("%s: buffer error: %s",
 452                                     __func__, ssh_err(r));
 453                         if (ssh_msg_send(ctxt->pam_csock,
 454                             PAM_MSG_MEMBER(msg, i, msg_style), buffer) == -1)
 455                                 goto fail;
 456                         break;
 457                 default:
 458                         goto fail;
 459                 }
 460                 sshbuf_reset(buffer);
 461         }
 462         sshbuf_free(buffer);
 463         *resp = reply;
 464         return (PAM_SUCCESS);
 465
 466  fail:
 467         for(i = 0; i < n; i++) {
 468                 free(reply[i].resp);
 469         }
 470         free(reply);
 471         sshbuf_free(buffer);
 472         return (PAM_CONV_ERR);
 473 }
 474
 475 /*
 476  * Authentication thread.
 477  */
 478 static void *
 479 sshpam_thread(void *ctxtp)
 480 {
 481         struct pam_ctxt *ctxt = ctxtp;
 482         struct sshbuf *buffer = NULL;
 483         struct pam_conv sshpam_conv;
 484         int r, flags = (options.permit_empty_passwd == 0 ?
 485             PAM_DISALLOW_NULL_AUTHTOK : 0);
 486 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 487         extern char **environ;
 488         char **env_from_pam;
 489         u_int i;
 490         const char *pam_user;
 491         const char **ptr_pam_user = &pam_user;
 492         char *tz = getenv("TZ");
 493
 494         sshpam_err = pam_get_item(sshpam_handle, PAM_USER,
 495             (sshpam_const void **)ptr_pam_user);
 496         if (sshpam_err != PAM_SUCCESS)
 497                 goto auth_fail;
 498
 499         environ[0] = NULL;
 500         if (tz != NULL)
 501                 if (setenv("TZ", tz, 1) == -1)
 502                         error("PAM: could not set TZ environment: %s",
 503                             strerror(errno));
 504
 505         if (sshpam_authctxt != NULL) {
 506                 setproctitle("%s [pam]",
 507                     sshpam_authctxt->valid ? pam_user : "unknown");
 508         }
 509 #endif
 510
 511         sshpam_conv.conv = sshpam_thread_conv;
 512         sshpam_conv.appdata_ptr = ctxt;
 513
 514         if (sshpam_authctxt == NULL)
 515                 fatal("%s: PAM authctxt not initialized", __func__);
 516
 517         if ((buffer = sshbuf_new()) == NULL)
 518                 fatal("%s: sshbuf_new failed", __func__);
 519
 520         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 521             (const void *)&sshpam_conv);
 522         if (sshpam_err != PAM_SUCCESS)
 523                 goto auth_fail;
 524         sshpam_err = pam_authenticate(sshpam_handle, flags);
 525         if (sshpam_err == PAM_MAXTRIES)
 526                 sshpam_set_maxtries_reached(1);
 527         if (sshpam_err != PAM_SUCCESS)
 528                 goto auth_fail;
 529
 530         if (!do_pam_account()) {
 531                 sshpam_err = PAM_ACCT_EXPIRED;
 532                 goto auth_fail;
 533         }
 534         if (sshpam_authctxt->force_pwchange) {
 535                 sshpam_err = pam_chauthtok(sshpam_handle,
 536                     PAM_CHANGE_EXPIRED_AUTHTOK);
 537                 if (sshpam_err != PAM_SUCCESS)
 538                         goto auth_fail;
 539                 sshpam_password_change_required(0);
 540         }
 541
 542         if ((r = sshbuf_put_cstring(buffer, "OK")) != 0)
 543                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 544
 545 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 546         /* Export variables set by do_pam_account */
 547         if ((r = sshbuf_put_u32(buffer, sshpam_account_status)) != 0 ||
 548             (r = sshbuf_put_u32(buffer, sshpam_authctxt->force_pwchange)) != 0)
 549                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 550
 551         /* Export any environment strings set in child */
 552         for (i = 0; environ[i] != NULL; i++) {
 553                 /* Count */
 554                 if (i > INT_MAX)
 555                         fatal("%s: too many environment strings", __func__);
 556         }
 557         if ((r = sshbuf_put_u32(buffer, i)) != 0)
 558                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 559         for (i = 0; environ[i] != NULL; i++) {
 560                 if ((r = sshbuf_put_cstring(buffer, environ[i])) != 0)
 561                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 562         }
 563         /* Export any environment strings set by PAM in child */
 564         env_from_pam = pam_getenvlist(sshpam_handle);
 565         for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
 566                 /* Count */
 567                 if (i > INT_MAX)
 568                         fatal("%s: too many PAM environment strings", __func__);
 569         }
 570         if ((r = sshbuf_put_u32(buffer, i)) != 0)
 571                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 572         for (i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++) {
 573                 if ((r = sshbuf_put_cstring(buffer, env_from_pam[i])) != 0)
 574                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 575         }
 576 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 577
 578         /* XXX - can't do much about an error here */
 579         ssh_msg_send(ctxt->pam_csock, sshpam_err, buffer);
 580         sshbuf_free(buffer);
 581         pthread_exit(NULL);
 582
 583  auth_fail:
 584         if ((r = sshbuf_put_cstring(buffer,
 585             pam_strerror(sshpam_handle, sshpam_err))) != 0)
 586                 fatal("%s: buffer error: %s", __func__, ssh_err(r));
 587         /* XXX - can't do much about an error here */
 588         if (sshpam_err == PAM_ACCT_EXPIRED)
 589                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, buffer);
 590         else if (sshpam_maxtries_reached)
 591                 ssh_msg_send(ctxt->pam_csock, PAM_MAXTRIES, buffer);
 592         else
 593                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, buffer);
 594         sshbuf_free(buffer);
 595         pthread_exit(NULL);
 596
 597         return (NULL); /* Avoid warning for non-pthread case */
 598 }
 599
 600 void
 601 sshpam_thread_cleanup(void)
 602 {
 603         struct pam_ctxt *ctxt = cleanup_ctxt;
 604
 605         debug3("PAM: %s entering", __func__);
 606         if (ctxt != NULL && ctxt->pam_thread != 0) {
 607                 pthread_cancel(ctxt->pam_thread);
 608                 pthread_join(ctxt->pam_thread, NULL);
 609                 close(ctxt->pam_psock);
 610                 close(ctxt->pam_csock);
 611                 memset(ctxt, 0, sizeof(*ctxt));
 612                 cleanup_ctxt = NULL;
 613         }
 614 }
 615
 616 static int
 617 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 618     struct pam_response **resp, void *data)
 619 {
 620         debug3("PAM: %s entering, %d messages", __func__, n);
 621         return (PAM_CONV_ERR);
 622 }
 623
 624 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 625
 626 static int
 627 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 628     struct pam_response **resp, void *data)
 629 {
 630         struct pam_response *reply;
 631         int r, i;
 632
 633         debug3("PAM: %s called with %d messages", __func__, n);
 634         *resp = NULL;
 635
 636         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 637                 return (PAM_CONV_ERR);
 638
 639         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 640                 return (PAM_CONV_ERR);
 641
 642         for (i = 0; i < n; ++i) {
 643                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 644                 case PAM_ERROR_MSG:
 645                 case PAM_TEXT_INFO:
 646                         if ((r = sshbuf_putf(loginmsg, "%s\n",
 647                             PAM_MSG_MEMBER(msg, i, msg))) != 0)
 648                                 fatal("%s: buffer error: %s",
 649                                     __func__, ssh_err(r));
 650                         reply[i].resp_retcode = PAM_SUCCESS;
 651                         break;
 652                 default:
 653                         goto fail;
 654                 }
 655         }
 656         *resp = reply;
 657         return (PAM_SUCCESS);
 658
 659  fail:
 660         for(i = 0; i < n; i++) {
 661                 free(reply[i].resp);
 662         }
 663         free(reply);
 664         return (PAM_CONV_ERR);
 665 }
 666
 667 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 668
 669 void
 670 sshpam_cleanup(void)
 671 {
 672         if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor()))
 673                 return;
 674         debug("PAM: cleanup");
 675         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 676         if (sshpam_session_open) {
 677                 debug("PAM: closing session");
 678                 pam_close_session(sshpam_handle, PAM_SILENT);
 679                 sshpam_session_open = 0;
 680         }
 681         if (sshpam_cred_established) {
 682                 debug("PAM: deleting credentials");
 683                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 684                 sshpam_cred_established = 0;
 685         }
 686         sshpam_authenticated = 0;
 687         pam_end(sshpam_handle, sshpam_err);
 688         sshpam_handle = NULL;
 689 }
 690
 691 static int
 692 sshpam_init(struct ssh *ssh, Authctxt *authctxt)
 693 {
 694         const char *pam_user, *user = authctxt->user;
 695         const char **ptr_pam_user = &pam_user;
 696         int r;
 697
 698 #if defined(PAM_SUN_CODEBASE) && defined(PAM_MAX_RESP_SIZE)
 699         /* Protect buggy PAM implementations from excessively long usernames */
 700         if (strlen(user) >= PAM_MAX_RESP_SIZE)
 701                 fatal("Username too long from %s port %d",
 702                     ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 703 #endif
 704         if (sshpam_handle == NULL) {
 705                 if (ssh == NULL) {
 706                         fatal("%s: called initially with no "
 707                             "packet context", __func__);
 708                 }
 709         } if (sshpam_handle != NULL) {
 710                 /* We already have a PAM context; check if the user matches */
 711                 sshpam_err = pam_get_item(sshpam_handle,
 712                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 713                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 714                         return (0);
 715                 pam_end(sshpam_handle, sshpam_err);
 716                 sshpam_handle = NULL;
 717         }
 718         debug("PAM: initializing for \"%s\"", user);
 719         sshpam_err =
 720             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 721         sshpam_authctxt = authctxt;
 722
 723         if (sshpam_err != PAM_SUCCESS) {
 724                 pam_end(sshpam_handle, sshpam_err);
 725                 sshpam_handle = NULL;
 726                 return (-1);
 727         }
 728
 729         if (ssh != NULL && sshpam_rhost == NULL) {
 730                 /*
 731                  * We need to cache these as we don't have packet context
 732                  * during the kbdint flow.
 733                  */
 734                 sshpam_rhost = xstrdup(auth_get_canonical_hostname(ssh,
 735                     options.use_dns));
 736                 sshpam_laddr = get_local_ipaddr(
 737                     ssh_packet_get_connection_in(ssh));
 738         }
 739         if (sshpam_rhost != NULL) {
 740                 debug("PAM: setting PAM_RHOST to \"%s\"", sshpam_rhost);
 741                 sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST,
 742                     sshpam_rhost);
 743                 if (sshpam_err != PAM_SUCCESS) {
 744                         pam_end(sshpam_handle, sshpam_err);
 745                         sshpam_handle = NULL;
 746                         return (-1);
 747                 }
 748         }
 749         if (ssh != NULL && sshpam_laddr != NULL) {
 750                 char *conninfo;
 751
 752                 /* Put SSH_CONNECTION in the PAM environment too */
 753                 xasprintf(&conninfo, "SSH_CONNECTION=%.50s %d %.50s %d",
 754                     ssh_remote_ipaddr(ssh), ssh_remote_port(ssh),
 755                     sshpam_laddr, ssh_local_port(ssh));
 756                 if ((r = pam_putenv(sshpam_handle, conninfo)) != PAM_SUCCESS)
 757                         logit("pam_putenv: %s", pam_strerror(sshpam_handle, r));
 758                 free(conninfo);
 759         }
 760
 761 #ifdef PAM_TTY_KLUDGE
 762         /*
 763          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 764          * sshd doesn't set the tty until too late in the auth process and
 765          * may not even set one (for tty-less connections)
 766          */
 767         debug("PAM: setting PAM_TTY to \"ssh\"");
 768         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 769         if (sshpam_err != PAM_SUCCESS) {
 770                 pam_end(sshpam_handle, sshpam_err);
 771                 sshpam_handle = NULL;
 772                 return (-1);
 773         }
 774 #endif
 775         return (0);
 776 }
 777
 778 static void
 779 expose_authinfo(const char *caller)
 780 {
 781         char *auth_info;
 782
 783         /*
 784          * Expose authentication information to PAM.
 785          * The environment variable is versioned. Please increment the
 786          * version suffix if the format of session_info changes.
 787          */
 788         if (sshpam_authctxt->session_info == NULL)
 789                 auth_info = xstrdup("");
 790         else if ((auth_info = sshbuf_dup_string(
 791             sshpam_authctxt->session_info)) == NULL)
 792                 fatal("%s: sshbuf_dup_string failed", __func__);
 793
 794         debug2("%s: auth information in SSH_AUTH_INFO_0", caller);
 795         do_pam_putenv("SSH_AUTH_INFO_0", auth_info);
 796         free(auth_info);
 797 }
 798
 799 static void *
 800 sshpam_init_ctx(Authctxt *authctxt)
 801 {
 802         struct pam_ctxt *ctxt;
 803         int result, socks[2];
 804
 805         debug3("PAM: %s entering", __func__);
 806         /*
 807          * Refuse to start if we don't have PAM enabled or do_pam_account
 808          * has previously failed.
 809          */
 810         if (!options.use_pam || sshpam_account_status == 0)
 811                 return NULL;
 812
 813         /* Initialize PAM */
 814         if (sshpam_init(NULL, authctxt) == -1) {
 815                 error("PAM: initialization failed");
 816                 return (NULL);
 817         }
 818
 819         expose_authinfo(__func__);
 820         ctxt = xcalloc(1, sizeof *ctxt);
 821
 822         /* Start the authentication thread */
 823         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 824                 error("PAM: failed create sockets: %s", strerror(errno));
 825                 free(ctxt);
 826                 return (NULL);
 827         }
 828         ctxt->pam_psock = socks[0];
 829         ctxt->pam_csock = socks[1];
 830         result = pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt);
 831         if (result != 0) {
 832                 error("PAM: failed to start authentication thread: %s",
 833                     strerror(result));
 834                 close(socks[0]);
 835                 close(socks[1]);
 836                 free(ctxt);
 837                 return (NULL);
 838         }
 839         cleanup_ctxt = ctxt;
 840         return (ctxt);
 841 }
 842
 843 static int
 844 sshpam_query(void *ctx, char **name, char **info,
 845     u_int *num, char ***prompts, u_int **echo_on)
 846 {
 847         struct sshbuf *buffer;
 848         struct pam_ctxt *ctxt = ctx;
 849         size_t plen;
 850         u_char type;
 851         char *msg;
 852         size_t len, mlen;
 853         int r;
 854
 855         debug3("PAM: %s entering", __func__);
 856         if ((buffer = sshbuf_new()) == NULL)
 857                 fatal("%s: sshbuf_new failed", __func__);
 858         *name = xstrdup("");
 859         *info = xstrdup("");
 860         *prompts = xmalloc(sizeof(char *));
 861         **prompts = NULL;
 862         plen = 0;
 863         *echo_on = xmalloc(sizeof(u_int));
 864         while (ssh_msg_recv(ctxt->pam_psock, buffer) == 0) {
 865                 if ((r = sshbuf_get_u8(buffer, &type)) != 0 ||
 866                     (r = sshbuf_get_cstring(buffer, &msg, &mlen)) != 0)
 867                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
 868                 switch (type) {
 869                 case PAM_PROMPT_ECHO_ON:
 870                 case PAM_PROMPT_ECHO_OFF:
 871                         *num = 1;
 872                         len = plen + mlen + 1;
 873                         **prompts = xreallocarray(**prompts, 1, len);
 874                         strlcpy(**prompts + plen, msg, len - plen);
 875                         plen += mlen;
 876                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 877                         free(msg);
 878                         sshbuf_free(buffer);
 879                         return (0);
 880                 case PAM_ERROR_MSG:
 881                 case PAM_TEXT_INFO:
 882                         /* accumulate messages */
 883                         len = plen + mlen + 2;
 884                         **prompts = xreallocarray(**prompts, 1, len);
 885                         strlcpy(**prompts + plen, msg, len - plen);
 886                         plen += mlen;
 887                         strlcat(**prompts + plen, "\n", len - plen);
 888                         plen++;
 889                         free(msg);
 890                         break;
 891                 case PAM_ACCT_EXPIRED:
 892                 case PAM_MAXTRIES:
 893                         if (type == PAM_ACCT_EXPIRED)
 894                                 sshpam_account_status = 0;
 895                         if (type == PAM_MAXTRIES)
 896                                 sshpam_set_maxtries_reached(1);
 897                         /* FALLTHROUGH */
 898                 case PAM_AUTH_ERR:
 899                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 900                         if (**prompts != NULL && strlen(**prompts) != 0) {
 901                                 free(*info);
 902                                 *info = **prompts;
 903                                 **prompts = NULL;
 904                                 *num = 0;
 905                                 **echo_on = 0;
 906                                 ctxt->pam_done = -1;
 907                                 free(msg);
 908                                 sshbuf_free(buffer);
 909                                 return 0;
 910                         }
 911                         /* FALLTHROUGH */
 912                 case PAM_SUCCESS:
 913                         if (**prompts != NULL) {
 914                                 /* drain any accumulated messages */
 915                                 debug("PAM: %s", **prompts);
 916                                 if ((r = sshbuf_put(loginmsg, **prompts,
 917                                     strlen(**prompts))) != 0)
 918                                         fatal("%s: buffer error: %s",
 919                                             __func__, ssh_err(r));
 920                                 free(**prompts);
 921                                 **prompts = NULL;
 922                         }
 923                         if (type == PAM_SUCCESS) {
 924                                 if (!sshpam_authctxt->valid ||
 925                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 926                                     options.permit_root_login != PERMIT_YES))
 927                                         fatal("Internal error: PAM auth "
 928                                             "succeeded when it should have "
 929                                             "failed");
 930                                 import_environments(buffer);
 931                                 *num = 0;
 932                                 **echo_on = 0;
 933                                 ctxt->pam_done = 1;
 934                                 free(msg);
 935                                 sshbuf_free(buffer);
 936                                 return (0);
 937                         }
 938                         BLACKLIST_NOTIFY(NULL, BLACKLIST_BAD_USER,
 939                             sshpam_authctxt->user);
 940                         error("PAM: %s for %s%.100s from %.100s", msg,
 941                             sshpam_authctxt->valid ? "" : "illegal user ",
 942                             sshpam_authctxt->user, sshpam_rhost);
 943                         /* FALLTHROUGH */
 944                 default:
 945                         *num = 0;
 946                         **echo_on = 0;
 947                         free(msg);
 948                         ctxt->pam_done = -1;
 949                         sshbuf_free(buffer);
 950                         return (-1);
 951                 }
 952         }
 953         sshbuf_free(buffer);
 954         return (-1);
 955 }
 956
 957 /*
 958  * Returns a junk password of identical length to that the user supplied.
 959  * Used to mitigate timing attacks against crypt(3)/PAM stacks that
 960  * vary processing time in proportion to password length.
 961  */
 962 static char *
 963 fake_password(const char *wire_password)
 964 {
 965         const char junk[] = "\b\n\r\177INCORRECT";
 966         char *ret = NULL;
 967         size_t i, l = wire_password != NULL ? strlen(wire_password) : 0;
 968
 969         if (l >= INT_MAX)
 970                 fatal("%s: password length too long: %zu", __func__, l);
 971
 972         ret = malloc(l + 1);
 973         if (ret == NULL)
 974                 return NULL;
 975         for (i = 0; i < l; i++)
 976                 ret[i] = junk[i % (sizeof(junk) - 1)];
 977         ret[i] = '\0';
 978         return ret;
 979 }
 980
 981 /* XXX - see also comment in auth-chall.c:verify_response */
 982 static int
 983 sshpam_respond(void *ctx, u_int num, char **resp)
 984 {
 985         struct sshbuf *buffer;
 986         struct pam_ctxt *ctxt = ctx;
 987         char *fake;
 988         int r;
 989
 990         debug2("PAM: %s entering, %u responses", __func__, num);
 991         switch (ctxt->pam_done) {
 992         case 1:
 993                 sshpam_authenticated = 1;
 994                 return (0);
 995         case 0:
 996                 break;
 997         default:
 998                 return (-1);
 999         }
1000         if (num != 1) {
1001                 error("PAM: expected one response, got %u", num);
1002                 return (-1);
1003         }
1004         if ((buffer = sshbuf_new()) == NULL)
1005                 fatal("%s: sshbuf_new failed", __func__);
1006         if (sshpam_authctxt->valid &&
1007             (sshpam_authctxt->pw->pw_uid != 0 ||
1008             options.permit_root_login == PERMIT_YES)) {
1009                 if ((r = sshbuf_put_cstring(buffer, *resp)) != 0)
1010                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
1011         } else {
1012                 fake = fake_password(*resp);
1013                 if ((r = sshbuf_put_cstring(buffer, fake)) != 0)
1014                         fatal("%s: buffer error: %s", __func__, ssh_err(r));
1015                 free(fake);
1016         }
1017         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, buffer) == -1) {
1018                 sshbuf_free(buffer);
1019                 return (-1);
1020         }
1021         sshbuf_free(buffer);
1022         return (1);
1023 }
1024
1025 static void
1026 sshpam_free_ctx(void *ctxtp)
1027 {
1028         struct pam_ctxt *ctxt = ctxtp;
1029
1030         debug3("PAM: %s entering", __func__);
1031         sshpam_thread_cleanup();
1032         free(ctxt);
1033         /*
1034          * We don't call sshpam_cleanup() here because we may need the PAM
1035          * handle at a later stage, e.g. when setting up a session.  It's
1036          * still on the cleanup list, so pam_end() *will* be called before
1037          * the server process terminates.
1038          */
1039 }
1040
1041 KbdintDevice sshpam_device = {
1042         "pam",
1043         sshpam_init_ctx,
1044         sshpam_query,
1045         sshpam_respond,
1046         sshpam_free_ctx
1047 };
1048
1049 KbdintDevice mm_sshpam_device = {
1050         "pam",
1051         mm_sshpam_init_ctx,
1052         mm_sshpam_query,
1053         mm_sshpam_respond,
1054         mm_sshpam_free_ctx
1055 };
1056
1057 /*
1058  * This replaces auth-pam.c
1059  */
1060 void
1061 start_pam(struct ssh *ssh)
1062 {
1063         Authctxt *authctxt = (Authctxt *)ssh->authctxt;
1064
1065         if (!options.use_pam)
1066                 fatal("PAM: initialisation requested when UsePAM=no");
1067
1068         if (sshpam_init(ssh, authctxt) == -1)
1069                 fatal("PAM: initialisation failed");
1070 }
1071
1072 void
1073 finish_pam(void)
1074 {
1075         sshpam_cleanup();
1076 }
1077
1078
1079 u_int
1080 do_pam_account(void)
1081 {
1082         debug("%s: called", __func__);
1083         if (sshpam_account_status != -1)
1084                 return (sshpam_account_status);
1085
1086         expose_authinfo(__func__);
1087
1088         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
1089         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
1090             pam_strerror(sshpam_handle, sshpam_err));
1091
1092         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
1093                 sshpam_account_status = 0;
1094                 return (sshpam_account_status);
1095         }
1096
1097         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
1098                 sshpam_password_change_required(1);
1099
1100         sshpam_account_status = 1;
1101         return (sshpam_account_status);
1102 }
1103
1104 void
1105 do_pam_setcred(int init)
1106 {
1107         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1108             (const void *)&store_conv);
1109         if (sshpam_err != PAM_SUCCESS)
1110                 fatal("PAM: failed to set PAM_CONV: %s",
1111                     pam_strerror(sshpam_handle, sshpam_err));
1112         if (init) {
1113                 debug("PAM: establishing credentials");
1114                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
1115         } else {
1116                 debug("PAM: reinitializing credentials");
1117                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
1118         }
1119         if (sshpam_err == PAM_SUCCESS) {
1120                 sshpam_cred_established = 1;
1121                 return;
1122         }
1123         if (sshpam_authenticated)
1124                 fatal("PAM: pam_setcred(): %s",
1125                     pam_strerror(sshpam_handle, sshpam_err));
1126         else
1127                 debug("PAM: pam_setcred(): %s",
1128                     pam_strerror(sshpam_handle, sshpam_err));
1129 }
1130
1131 static int
1132 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
1133     struct pam_response **resp, void *data)
1134 {
1135         char input[PAM_MAX_MSG_SIZE];
1136         struct pam_response *reply;
1137         int i;
1138
1139         debug3("PAM: %s called with %d messages", __func__, n);
1140
1141         *resp = NULL;
1142
1143         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
1144                 return (PAM_CONV_ERR);
1145
1146         if ((reply = calloc(n, sizeof(*reply))) == NULL)
1147                 return (PAM_CONV_ERR);
1148
1149         for (i = 0; i < n; ++i) {
1150                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1151                 case PAM_PROMPT_ECHO_OFF:
1152                         reply[i].resp =
1153                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
1154                             RP_ALLOW_STDIN);
1155                         reply[i].resp_retcode = PAM_SUCCESS;
1156                         break;
1157                 case PAM_PROMPT_ECHO_ON:
1158                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
1159                         if (fgets(input, sizeof input, stdin) == NULL)
1160                                 input[0] = '\0';
1161                         if ((reply[i].resp = strdup(input)) == NULL)
1162                                 goto fail;
1163                         reply[i].resp_retcode = PAM_SUCCESS;
1164                         break;
1165                 case PAM_ERROR_MSG:
1166                 case PAM_TEXT_INFO:
1167                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
1168                         reply[i].resp_retcode = PAM_SUCCESS;
1169                         break;
1170                 default:
1171                         goto fail;
1172                 }
1173         }
1174         *resp = reply;
1175         return (PAM_SUCCESS);
1176
1177  fail:
1178         for(i = 0; i < n; i++) {
1179                 free(reply[i].resp);
1180         }
1181         free(reply);
1182         return (PAM_CONV_ERR);
1183 }
1184
1185 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1186
1187 /*
1188  * XXX this should be done in the authentication phase, but ssh1 doesn't
1189  * support that
1190  */
1191 void
1192 do_pam_chauthtok(void)
1193 {
1194         if (use_privsep)
1195                 fatal("Password expired (unable to change with privsep)");
1196         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1197             (const void *)&tty_conv);
1198         if (sshpam_err != PAM_SUCCESS)
1199                 fatal("PAM: failed to set PAM_CONV: %s",
1200                     pam_strerror(sshpam_handle, sshpam_err));
1201         debug("PAM: changing password");
1202         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1203         if (sshpam_err != PAM_SUCCESS)
1204                 fatal("PAM: pam_chauthtok(): %s",
1205                     pam_strerror(sshpam_handle, sshpam_err));
1206 }
1207
1208 void
1209 do_pam_session(struct ssh *ssh)
1210 {
1211         debug3("PAM: opening session");
1212
1213         expose_authinfo(__func__);
1214
1215         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1216             (const void *)&store_conv);
1217         if (sshpam_err != PAM_SUCCESS)
1218                 fatal("PAM: failed to set PAM_CONV: %s",
1219                     pam_strerror(sshpam_handle, sshpam_err));
1220         sshpam_err = pam_open_session(sshpam_handle, 0);
1221         if (sshpam_err == PAM_SUCCESS)
1222                 sshpam_session_open = 1;
1223         else {
1224                 sshpam_session_open = 0;
1225                 auth_restrict_session(ssh);
1226                 error("PAM: pam_open_session(): %s",
1227                     pam_strerror(sshpam_handle, sshpam_err));
1228         }
1229
1230 }
1231
1232 int
1233 is_pam_session_open(void)
1234 {
1235         return sshpam_session_open;
1236 }
1237
1238 /*
1239  * Set a PAM environment string. We need to do this so that the session
1240  * modules can handle things like Kerberos/GSI credentials that appear
1241  * during the ssh authentication process.
1242  */
1243 int
1244 do_pam_putenv(char *name, char *value)
1245 {
1246         int ret = 1;
1247         char *compound;
1248         size_t len;
1249
1250         len = strlen(name) + strlen(value) + 2;
1251         compound = xmalloc(len);
1252
1253         snprintf(compound, len, "%s=%s", name, value);
1254         ret = pam_putenv(sshpam_handle, compound);
1255         free(compound);
1256
1257         return (ret);
1258 }
1259
1260 char **
1261 fetch_pam_child_environment(void)
1262 {
1263         return sshpam_env;
1264 }
1265
1266 char **
1267 fetch_pam_environment(void)
1268 {
1269         return (pam_getenvlist(sshpam_handle));
1270 }
1271
1272 void
1273 free_pam_environment(char **env)
1274 {
1275         char **envp;
1276
1277         if (env == NULL)
1278                 return;
1279
1280         for (envp = env; *envp; envp++)
1281                 free(*envp);
1282         free(env);
1283 }
1284
1285 /*
1286  * "Blind" conversation function for password authentication.  Assumes that
1287  * echo-off prompts are for the password and stores messages for later
1288  * display.
1289  */
1290 static int
1291 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1292     struct pam_response **resp, void *data)
1293 {
1294         struct pam_response *reply;
1295         int r, i;
1296         size_t len;
1297
1298         debug3("PAM: %s called with %d messages", __func__, n);
1299
1300         *resp = NULL;
1301
1302         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1303                 return (PAM_CONV_ERR);
1304
1305         if ((reply = calloc(n, sizeof(*reply))) == NULL)
1306                 return (PAM_CONV_ERR);
1307
1308         for (i = 0; i < n; ++i) {
1309                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1310                 case PAM_PROMPT_ECHO_OFF:
1311                         if (sshpam_password == NULL)
1312                                 goto fail;
1313                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1314                                 goto fail;
1315                         reply[i].resp_retcode = PAM_SUCCESS;
1316                         break;
1317                 case PAM_ERROR_MSG:
1318                 case PAM_TEXT_INFO:
1319                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1320                         if (len > 0) {
1321                                 if ((r = sshbuf_putf(loginmsg, "%s\n",
1322                                     PAM_MSG_MEMBER(msg, i, msg))) != 0)
1323                                         fatal("%s: buffer error: %s",
1324                                             __func__, ssh_err(r));
1325                         }
1326                         if ((reply[i].resp = strdup("")) == NULL)
1327                                 goto fail;
1328                         reply[i].resp_retcode = PAM_SUCCESS;
1329                         break;
1330                 default:
1331                         goto fail;
1332                 }
1333         }
1334         *resp = reply;
1335         return (PAM_SUCCESS);
1336
1337  fail:
1338         for(i = 0; i < n; i++) {
1339                 free(reply[i].resp);
1340         }
1341         free(reply);
1342         return (PAM_CONV_ERR);
1343 }
1344
1345 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1346
1347 /*
1348  * Attempt password authentication via PAM
1349  */
1350 int
1351 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1352 {
1353         int flags = (options.permit_empty_passwd == 0 ?
1354             PAM_DISALLOW_NULL_AUTHTOK : 0);
1355         char *fake = NULL;
1356
1357         if (!options.use_pam || sshpam_handle == NULL)
1358                 fatal("PAM: %s called when PAM disabled or failed to "
1359                     "initialise.", __func__);
1360
1361         sshpam_password = password;
1362         sshpam_authctxt = authctxt;
1363
1364         /*
1365          * If the user logging in is invalid, or is root but is not permitted
1366          * by PermitRootLogin, use an invalid password to prevent leaking
1367          * information via timing (eg if the PAM config has a delay on fail).
1368          */
1369         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1370             options.permit_root_login != PERMIT_YES))
1371                 sshpam_password = fake = fake_password(password);
1372
1373         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1374             (const void *)&passwd_conv);
1375         if (sshpam_err != PAM_SUCCESS)
1376                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1377                     pam_strerror(sshpam_handle, sshpam_err));
1378
1379         sshpam_err = pam_authenticate(sshpam_handle, flags);
1380         sshpam_password = NULL;
1381         free(fake);
1382         if (sshpam_err == PAM_MAXTRIES)
1383                 sshpam_set_maxtries_reached(1);
1384         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1385                 debug("PAM: password authentication accepted for %.100s",
1386                     authctxt->user);
1387                 return 1;
1388         } else {
1389                 debug("PAM: password authentication failed for %.100s: %s",
1390                     authctxt->valid ? authctxt->user : "an illegal user",
1391                     pam_strerror(sshpam_handle, sshpam_err));
1392                 return 0;
1393         }
1394 }
1395
1396 int
1397 sshpam_get_maxtries_reached(void)
1398 {
1399         return sshpam_maxtries_reached;
1400 }
1401
1402 void
1403 sshpam_set_maxtries_reached(int reached)
1404 {
1405         if (reached == 0 || sshpam_maxtries_reached)
1406                 return;
1407         sshpam_maxtries_reached = 1;
1408         options.password_authentication = 0;
1409         options.kbd_interactive_authentication = 0;
1410 }
1411 #endif /* USE_PAM */