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