auth-pam.c

   1 /*-
   2  * Copyright (c) 2002 Networks Associates Technology, Inc.
   3  * All rights reserved.
   4  *
   5  * This software was developed for the FreeBSD Project by ThinkSec AS and
   6  * NAI Labs, the Security Research Division of Network Associates, Inc.
   7  * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
   8  * DARPA CHATS research program.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31 /*
  32  * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org>
  33  * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au>
  34  *
  35  * Permission to use, copy, modify, and distribute this software for any
  36  * purpose with or without fee is hereby granted, provided that the above
  37  * copyright notice and this permission notice appear in all copies.
  38  *
  39  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  40  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  41  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  42  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  43  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  44  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  45  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  46  */
  47
  48 /* Based on $FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des Exp $ */
  49 #include "includes.h"
  50
  51 #include <sys/types.h>
  52 #include <sys/stat.h>
  53 #include <sys/wait.h>
  54
  55 #include <errno.h>
  56 #include <signal.h>
  57 #include <string.h>
  58 #include <unistd.h>
  59
  60 #ifdef USE_PAM
  61 #if defined(HAVE_SECURITY_PAM_APPL_H)
  62 #include <security/pam_appl.h>
  63 #elif defined (HAVE_PAM_PAM_APPL_H)
  64 #include <pam/pam_appl.h>
  65 #endif
  66
  67 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
  68 #ifdef PAM_SUN_CODEBASE
  69 # define sshpam_const           /* Solaris, HP-UX, AIX */
  70 #else
  71 # define sshpam_const   const   /* LinuxPAM, OpenPAM */
  72 #endif
  73
  74 #include "auth.h"
  75 #include "auth-pam.h"
  76 #include "buffer.h"
  77 #include "bufaux.h"
  78 #include "canohost.h"
  79 #include "log.h"
  80 #include "monitor_wrap.h"
  81 #include "msg.h"
  82 #include "packet.h"
  83 #include "misc.h"
  84 #include "servconf.h"
  85 #include "ssh2.h"
  86 #include "xmalloc.h"
  87 #include "auth-options.h"
  88
  89 extern ServerOptions options;
  90 extern Buffer loginmsg;
  91 extern int compat20;
  92 extern u_int utmp_len;
  93
  94 /* so we don't silently change behaviour */
  95 #ifdef USE_POSIX_THREADS
  96 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
  97 #endif
  98
  99 /*
 100  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
 101  * and generally a bad idea.  Use at own risk and do not expect support if
 102  * this breaks.
 103  */
 104 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
 105 #include <pthread.h>
 106 /*
 107  * Avoid namespace clash when *not* using pthreads for systems *with*
 108  * pthreads, which unconditionally define pthread_t via sys/types.h
 109  * (e.g. Linux)
 110  */
 111 typedef pthread_t sp_pthread_t;
 112 #else
 113 typedef pid_t sp_pthread_t;
 114 #endif
 115
 116 struct pam_ctxt {
 117         sp_pthread_t     pam_thread;
 118         int              pam_psock;
 119         int              pam_csock;
 120         int              pam_done;
 121 };
 122
 123 static void sshpam_free_ctx(void *);
 124 static struct pam_ctxt *cleanup_ctxt;
 125
 126 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 127 /*
 128  * Simulate threads with processes.
 129  */
 130
 131 static int sshpam_thread_status = -1;
 132 static mysig_t sshpam_oldsig;
 133
 134 static void
 135 sshpam_sigchld_handler(int sig)
 136 {
 137         signal(SIGCHLD, SIG_DFL);
 138         if (cleanup_ctxt == NULL)
 139                 return; /* handler called after PAM cleanup, shouldn't happen */
 140         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 141             <= 0) {
 142                 /* PAM thread has not exitted, privsep slave must have */
 143                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 144                 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
 145                     <= 0)
 146                         return; /* could not wait */
 147         }
 148         if (WIFSIGNALED(sshpam_thread_status) &&
 149             WTERMSIG(sshpam_thread_status) == SIGTERM)
 150                 return; /* terminated by pthread_cancel */
 151         if (!WIFEXITED(sshpam_thread_status))
 152                 fatal("PAM: authentication thread exited unexpectedly");
 153         if (WEXITSTATUS(sshpam_thread_status) != 0)
 154                 fatal("PAM: authentication thread exited uncleanly");
 155 }
 156
 157 /* ARGSUSED */
 158 static void
 159 pthread_exit(void *value)
 160 {
 161         _exit(0);
 162 }
 163
 164 /* ARGSUSED */
 165 static int
 166 pthread_create(sp_pthread_t *thread, const void *attr,
 167     void *(*thread_start)(void *), void *arg)
 168 {
 169         pid_t pid;
 170         struct pam_ctxt *ctx = arg;
 171
 172         sshpam_thread_status = -1;
 173         switch ((pid = fork())) {
 174         case -1:
 175                 error("fork(): %s", strerror(errno));
 176                 return (-1);
 177         case 0:
 178                 close(ctx->pam_psock);
 179                 ctx->pam_psock = -1;
 180                 thread_start(arg);
 181                 _exit(1);
 182         default:
 183                 *thread = pid;
 184                 close(ctx->pam_csock);
 185                 ctx->pam_csock = -1;
 186                 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
 187                 return (0);
 188         }
 189 }
 190
 191 static int
 192 pthread_cancel(sp_pthread_t thread)
 193 {
 194         signal(SIGCHLD, sshpam_oldsig);
 195         return (kill(thread, SIGTERM));
 196 }
 197
 198 /* ARGSUSED */
 199 static int
 200 pthread_join(sp_pthread_t thread, void **value)
 201 {
 202         int status;
 203
 204         if (sshpam_thread_status != -1)
 205                 return (sshpam_thread_status);
 206         signal(SIGCHLD, sshpam_oldsig);
 207         waitpid(thread, &status, 0);
 208         return (status);
 209 }
 210 #endif
 211
 212
 213 static pam_handle_t *sshpam_handle = NULL;
 214 static int sshpam_err = 0;
 215 static int sshpam_authenticated = 0;
 216 static int sshpam_session_open = 0;
 217 static int sshpam_cred_established = 0;
 218 static int sshpam_account_status = -1;
 219 static char **sshpam_env = NULL;
 220 static Authctxt *sshpam_authctxt = NULL;
 221 static const char *sshpam_password = NULL;
 222 static char badpw[] = "\b\n\r\177INCORRECT";
 223
 224 /* Some PAM implementations don't implement this */
 225 #ifndef HAVE_PAM_GETENVLIST
 226 static char **
 227 pam_getenvlist(pam_handle_t *pamh)
 228 {
 229         /*
 230          * XXX - If necessary, we can still support envrionment passing
 231          * for platforms without pam_getenvlist by searching for known
 232          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 233          */
 234          return NULL;
 235 }
 236 #endif
 237
 238 /*
 239  * Some platforms, notably Solaris, do not enforce password complexity
 240  * rules during pam_chauthtok() if the real uid of the calling process
 241  * is 0, on the assumption that it's being called by "passwd" run by root.
 242  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 243  * the right thing.
 244  */
 245 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 246 static int
 247 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 248 {
 249         int result;
 250
 251         if (sshpam_authctxt == NULL)
 252                 fatal("PAM: sshpam_authctxt not initialized");
 253         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 254                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 255         result = pam_chauthtok(pamh, flags);
 256         if (setreuid(0, -1) == -1)
 257                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 258         return result;
 259 }
 260 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 261 #endif
 262
 263 void
 264 sshpam_password_change_required(int reqd)
 265 {
 266         debug3("%s %d", __func__, reqd);
 267         if (sshpam_authctxt == NULL)
 268                 fatal("%s: PAM authctxt not initialized", __func__);
 269         sshpam_authctxt->force_pwchange = reqd;
 270         if (reqd) {
 271                 no_port_forwarding_flag |= 2;
 272                 no_agent_forwarding_flag |= 2;
 273                 no_x11_forwarding_flag |= 2;
 274         } else {
 275                 no_port_forwarding_flag &= ~2;
 276                 no_agent_forwarding_flag &= ~2;
 277                 no_x11_forwarding_flag &= ~2;
 278         }
 279 }
 280
 281 /* Import regular and PAM environment from subprocess */
 282 static void
 283 import_environments(Buffer *b)
 284 {
 285         char *env;
 286         u_int i, num_env;
 287         int err;
 288
 289         debug3("PAM: %s entering", __func__);
 290
 291 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 292         /* Import variables set by do_pam_account */
 293         sshpam_account_status = buffer_get_int(b);
 294         sshpam_password_change_required(buffer_get_int(b));
 295
 296         /* Import environment from subprocess */
 297         num_env = buffer_get_int(b);
 298         if (num_env > 1024)
 299                 fatal("%s: received %u environment variables, expected <= 1024",
 300                     __func__, num_env);
 301         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 302         debug3("PAM: num env strings %d", num_env);
 303         for(i = 0; i < num_env; i++)
 304                 sshpam_env[i] = buffer_get_string(b, NULL);
 305
 306         sshpam_env[num_env] = NULL;
 307
 308         /* Import PAM environment from subprocess */
 309         num_env = buffer_get_int(b);
 310         debug("PAM: num PAM env strings %d", num_env);
 311         for(i = 0; i < num_env; i++) {
 312                 env = buffer_get_string(b, NULL);
 313
 314 #ifdef HAVE_PAM_PUTENV
 315                 /* Errors are not fatal here */
 316                 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 317                         error("PAM: pam_putenv: %s",
 318                             pam_strerror(sshpam_handle, sshpam_err));
 319                 }
 320 #endif
 321         }
 322 #endif
 323 }
 324
 325 /*
 326  * Conversation function for authentication thread.
 327  */
 328 static int
 329 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 330     struct pam_response **resp, void *data)
 331 {
 332         Buffer buffer;
 333         struct pam_ctxt *ctxt;
 334         struct pam_response *reply;
 335         int i;
 336
 337         debug3("PAM: %s entering, %d messages", __func__, n);
 338         *resp = NULL;
 339
 340         if (data == NULL) {
 341                 error("PAM: conversation function passed a null context");
 342                 return (PAM_CONV_ERR);
 343         }
 344         ctxt = data;
 345         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 346                 return (PAM_CONV_ERR);
 347
 348         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 349                 return (PAM_CONV_ERR);
 350
 351         buffer_init(&buffer);
 352         for (i = 0; i < n; ++i) {
 353                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 354                 case PAM_PROMPT_ECHO_OFF:
 355                         buffer_put_cstring(&buffer,
 356                             PAM_MSG_MEMBER(msg, i, msg));
 357                         if (ssh_msg_send(ctxt->pam_csock,
 358                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 359                                 goto fail;
 360                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 361                                 goto fail;
 362                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 363                                 goto fail;
 364                         reply[i].resp = buffer_get_string(&buffer, NULL);
 365                         break;
 366                 case PAM_PROMPT_ECHO_ON:
 367                         buffer_put_cstring(&buffer,
 368                             PAM_MSG_MEMBER(msg, i, msg));
 369                         if (ssh_msg_send(ctxt->pam_csock,
 370                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 371                                 goto fail;
 372                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 373                                 goto fail;
 374                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 375                                 goto fail;
 376                         reply[i].resp = buffer_get_string(&buffer, NULL);
 377                         break;
 378                 case PAM_ERROR_MSG:
 379                         buffer_put_cstring(&buffer,
 380                             PAM_MSG_MEMBER(msg, i, msg));
 381                         if (ssh_msg_send(ctxt->pam_csock,
 382                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 383                                 goto fail;
 384                         break;
 385                 case PAM_TEXT_INFO:
 386                         buffer_put_cstring(&buffer,
 387                             PAM_MSG_MEMBER(msg, i, msg));
 388                         if (ssh_msg_send(ctxt->pam_csock,
 389                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 390                                 goto fail;
 391                         break;
 392                 default:
 393                         goto fail;
 394                 }
 395                 buffer_clear(&buffer);
 396         }
 397         buffer_free(&buffer);
 398         *resp = reply;
 399         return (PAM_SUCCESS);
 400
 401  fail:
 402         for(i = 0; i < n; i++) {
 403                 if (reply[i].resp != NULL)
 404                         xfree(reply[i].resp);
 405         }
 406         xfree(reply);
 407         buffer_free(&buffer);
 408         return (PAM_CONV_ERR);
 409 }
 410
 411 /*
 412  * Authentication thread.
 413  */
 414 static void *
 415 sshpam_thread(void *ctxtp)
 416 {
 417         struct pam_ctxt *ctxt = ctxtp;
 418         Buffer buffer;
 419         struct pam_conv sshpam_conv;
 420         int flags = (options.permit_empty_passwd == 0 ?
 421             PAM_DISALLOW_NULL_AUTHTOK : 0);
 422 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 423         extern char **environ;
 424         char **env_from_pam;
 425         u_int i;
 426         const char *pam_user;
 427         const char **ptr_pam_user = &pam_user;
 428
 429         pam_get_item(sshpam_handle, PAM_USER,
 430             (sshpam_const void **)ptr_pam_user);
 431         environ[0] = NULL;
 432
 433         if (sshpam_authctxt != NULL) {
 434                 setproctitle("%s [pam]",
 435                     sshpam_authctxt->valid ? pam_user : "unknown");
 436         }
 437 #endif
 438
 439         sshpam_conv.conv = sshpam_thread_conv;
 440         sshpam_conv.appdata_ptr = ctxt;
 441
 442         if (sshpam_authctxt == NULL)
 443                 fatal("%s: PAM authctxt not initialized", __func__);
 444
 445         buffer_init(&buffer);
 446         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 447             (const void *)&sshpam_conv);
 448         if (sshpam_err != PAM_SUCCESS)
 449                 goto auth_fail;
 450         sshpam_err = pam_authenticate(sshpam_handle, flags);
 451         if (sshpam_err != PAM_SUCCESS)
 452                 goto auth_fail;
 453
 454         if (compat20) {
 455                 if (!do_pam_account()) {
 456                         sshpam_err = PAM_ACCT_EXPIRED;
 457                         goto auth_fail;
 458                 }
 459                 if (sshpam_authctxt->force_pwchange) {
 460                         sshpam_err = pam_chauthtok(sshpam_handle,
 461                             PAM_CHANGE_EXPIRED_AUTHTOK);
 462                         if (sshpam_err != PAM_SUCCESS)
 463                                 goto auth_fail;
 464                         sshpam_password_change_required(0);
 465                 }
 466         }
 467
 468         buffer_put_cstring(&buffer, "OK");
 469
 470 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 471         /* Export variables set by do_pam_account */
 472         buffer_put_int(&buffer, sshpam_account_status);
 473         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 474
 475         /* Export any environment strings set in child */
 476         for(i = 0; environ[i] != NULL; i++)
 477                 ; /* Count */
 478         buffer_put_int(&buffer, i);
 479         for(i = 0; environ[i] != NULL; i++)
 480                 buffer_put_cstring(&buffer, environ[i]);
 481
 482         /* Export any environment strings set by PAM in child */
 483         env_from_pam = pam_getenvlist(sshpam_handle);
 484         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 485                 ; /* Count */
 486         buffer_put_int(&buffer, i);
 487         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 488                 buffer_put_cstring(&buffer, env_from_pam[i]);
 489 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 490
 491         /* XXX - can't do much about an error here */
 492         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 493         buffer_free(&buffer);
 494         pthread_exit(NULL);
 495
 496  auth_fail:
 497         buffer_put_cstring(&buffer,
 498             pam_strerror(sshpam_handle, sshpam_err));
 499         /* XXX - can't do much about an error here */
 500         if (sshpam_err == PAM_ACCT_EXPIRED)
 501                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);
 502         else
 503                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 504         buffer_free(&buffer);
 505         pthread_exit(NULL);
 506
 507         return (NULL); /* Avoid warning for non-pthread case */
 508 }
 509
 510 void
 511 sshpam_thread_cleanup(void)
 512 {
 513         struct pam_ctxt *ctxt = cleanup_ctxt;
 514
 515         debug3("PAM: %s entering", __func__);
 516         if (ctxt != NULL && ctxt->pam_thread != 0) {
 517                 pthread_cancel(ctxt->pam_thread);
 518                 pthread_join(ctxt->pam_thread, NULL);
 519                 close(ctxt->pam_psock);
 520                 close(ctxt->pam_csock);
 521                 memset(ctxt, 0, sizeof(*ctxt));
 522                 cleanup_ctxt = NULL;
 523         }
 524 }
 525
 526 static int
 527 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 528     struct pam_response **resp, void *data)
 529 {
 530         debug3("PAM: %s entering, %d messages", __func__, n);
 531         return (PAM_CONV_ERR);
 532 }
 533
 534 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 535
 536 static int
 537 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 538     struct pam_response **resp, void *data)
 539 {
 540         struct pam_response *reply;
 541         int i;
 542         size_t len;
 543
 544         debug3("PAM: %s called with %d messages", __func__, n);
 545         *resp = NULL;
 546
 547         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 548                 return (PAM_CONV_ERR);
 549
 550         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 551                 return (PAM_CONV_ERR);
 552
 553         for (i = 0; i < n; ++i) {
 554                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 555                 case PAM_ERROR_MSG:
 556                 case PAM_TEXT_INFO:
 557                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 558                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 559                         buffer_append(&loginmsg, "\n", 1 );
 560                         reply[i].resp_retcode = PAM_SUCCESS;
 561                         break;
 562                 default:
 563                         goto fail;
 564                 }
 565         }
 566         *resp = reply;
 567         return (PAM_SUCCESS);
 568
 569  fail:
 570         for(i = 0; i < n; i++) {
 571                 if (reply[i].resp != NULL)
 572                         xfree(reply[i].resp);
 573         }
 574         xfree(reply);
 575         return (PAM_CONV_ERR);
 576 }
 577
 578 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 579
 580 void
 581 sshpam_cleanup(void)
 582 {
 583         debug("PAM: cleanup");
 584         if (sshpam_handle == NULL)
 585                 return;
 586         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 587         if (sshpam_cred_established) {
 588                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 589                 sshpam_cred_established = 0;
 590         }
 591         if (sshpam_session_open) {
 592                 pam_close_session(sshpam_handle, PAM_SILENT);
 593                 sshpam_session_open = 0;
 594         }
 595         sshpam_authenticated = 0;
 596         pam_end(sshpam_handle, sshpam_err);
 597         sshpam_handle = NULL;
 598 }
 599
 600 static int
 601 sshpam_init(Authctxt *authctxt)
 602 {
 603         extern char *__progname;
 604         const char *pam_rhost, *pam_user, *user = authctxt->user;
 605         const char **ptr_pam_user = &pam_user;
 606
 607         if (sshpam_handle != NULL) {
 608                 /* We already have a PAM context; check if the user matches */
 609                 sshpam_err = pam_get_item(sshpam_handle,
 610                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 611                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 612                         return (0);
 613                 pam_end(sshpam_handle, sshpam_err);
 614                 sshpam_handle = NULL;
 615         }
 616         debug("PAM: initializing for \"%s\"", user);
 617         sshpam_err =
 618             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 619         sshpam_authctxt = authctxt;
 620
 621         if (sshpam_err != PAM_SUCCESS) {
 622                 pam_end(sshpam_handle, sshpam_err);
 623                 sshpam_handle = NULL;
 624                 return (-1);
 625         }
 626         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 627         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 628         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 629         if (sshpam_err != PAM_SUCCESS) {
 630                 pam_end(sshpam_handle, sshpam_err);
 631                 sshpam_handle = NULL;
 632                 return (-1);
 633         }
 634 #ifdef PAM_TTY_KLUDGE
 635         /*
 636          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 637          * sshd doesn't set the tty until too late in the auth process and
 638          * may not even set one (for tty-less connections)
 639          */
 640         debug("PAM: setting PAM_TTY to \"ssh\"");
 641         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 642         if (sshpam_err != PAM_SUCCESS) {
 643                 pam_end(sshpam_handle, sshpam_err);
 644                 sshpam_handle = NULL;
 645                 return (-1);
 646         }
 647 #endif
 648         return (0);
 649 }
 650
 651 static void *
 652 sshpam_init_ctx(Authctxt *authctxt)
 653 {
 654         struct pam_ctxt *ctxt;
 655         int socks[2];
 656
 657         debug3("PAM: %s entering", __func__);
 658         /*
 659          * Refuse to start if we don't have PAM enabled or do_pam_account
 660          * has previously failed.
 661          */
 662         if (!options.use_pam || sshpam_account_status == 0)
 663                 return NULL;
 664
 665         /* Initialize PAM */
 666         if (sshpam_init(authctxt) == -1) {
 667                 error("PAM: initialization failed");
 668                 return (NULL);
 669         }
 670
 671         ctxt = xmalloc(sizeof *ctxt);
 672         memset(ctxt, 0, sizeof(*ctxt));
 673
 674         /* Start the authentication thread */
 675         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 676                 error("PAM: failed create sockets: %s", strerror(errno));
 677                 xfree(ctxt);
 678                 return (NULL);
 679         }
 680         ctxt->pam_psock = socks[0];
 681         ctxt->pam_csock = socks[1];
 682         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 683                 error("PAM: failed to start authentication thread: %s",
 684                     strerror(errno));
 685                 close(socks[0]);
 686                 close(socks[1]);
 687                 xfree(ctxt);
 688                 return (NULL);
 689         }
 690         cleanup_ctxt = ctxt;
 691         return (ctxt);
 692 }
 693
 694 static int
 695 sshpam_query(void *ctx, char **name, char **info,
 696     u_int *num, char ***prompts, u_int **echo_on)
 697 {
 698         Buffer buffer;
 699         struct pam_ctxt *ctxt = ctx;
 700         size_t plen;
 701         u_char type;
 702         char *msg;
 703         size_t len, mlen;
 704
 705         debug3("PAM: %s entering", __func__);
 706         buffer_init(&buffer);
 707         *name = xstrdup("");
 708         *info = xstrdup("");
 709         *prompts = xmalloc(sizeof(char *));
 710         **prompts = NULL;
 711         plen = 0;
 712         *echo_on = xmalloc(sizeof(u_int));
 713         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 714                 type = buffer_get_char(&buffer);
 715                 msg = buffer_get_string(&buffer, NULL);
 716                 mlen = strlen(msg);
 717                 switch (type) {
 718                 case PAM_PROMPT_ECHO_ON:
 719                 case PAM_PROMPT_ECHO_OFF:
 720                         *num = 1;
 721                         len = plen + mlen + 1;
 722                         **prompts = xrealloc(**prompts, 1, len);
 723                         strlcpy(**prompts + plen, msg, len - plen);
 724                         plen += mlen;
 725                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 726                         xfree(msg);
 727                         return (0);
 728                 case PAM_ERROR_MSG:
 729                 case PAM_TEXT_INFO:
 730                         /* accumulate messages */
 731                         len = plen + mlen + 2;
 732                         **prompts = xrealloc(**prompts, 1, len);
 733                         strlcpy(**prompts + plen, msg, len - plen);
 734                         plen += mlen;
 735                         strlcat(**prompts + plen, "\n", len - plen);
 736                         plen++;
 737                         xfree(msg);
 738                         break;
 739                 case PAM_ACCT_EXPIRED:
 740                         sshpam_account_status = 0;
 741                         /* FALLTHROUGH */
 742                 case PAM_AUTH_ERR:
 743                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 744                         if (**prompts != NULL && strlen(**prompts) != 0) {
 745                                 *info = **prompts;
 746                                 **prompts = NULL;
 747                                 *num = 0;
 748                                 **echo_on = 0;
 749                                 ctxt->pam_done = -1;
 750                                 xfree(msg);
 751                                 return 0;
 752                         }
 753                         /* FALLTHROUGH */
 754                 case PAM_SUCCESS:
 755                         if (**prompts != NULL) {
 756                                 /* drain any accumulated messages */
 757                                 debug("PAM: %s", **prompts);
 758                                 buffer_append(&loginmsg, **prompts,
 759                                     strlen(**prompts));
 760                                 xfree(**prompts);
 761                                 **prompts = NULL;
 762                         }
 763                         if (type == PAM_SUCCESS) {
 764                                 if (!sshpam_authctxt->valid ||
 765                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 766                                     options.permit_root_login != PERMIT_YES))
 767                                         fatal("Internal error: PAM auth "
 768                                             "succeeded when it should have "
 769                                             "failed");
 770                                 import_environments(&buffer);
 771                                 *num = 0;
 772                                 **echo_on = 0;
 773                                 ctxt->pam_done = 1;
 774                                 xfree(msg);
 775                                 return (0);
 776                         }
 777                         error("PAM: %s for %s%.100s from %.100s", msg,
 778                             sshpam_authctxt->valid ? "" : "illegal user ",
 779                             sshpam_authctxt->user,
 780                             get_remote_name_or_ip(utmp_len, options.use_dns));
 781                         /* FALLTHROUGH */
 782                 default:
 783                         *num = 0;
 784                         **echo_on = 0;
 785                         xfree(msg);
 786                         ctxt->pam_done = -1;
 787                         return (-1);
 788                 }
 789         }
 790         return (-1);
 791 }
 792
 793 /* XXX - see also comment in auth-chall.c:verify_response */
 794 static int
 795 sshpam_respond(void *ctx, u_int num, char **resp)
 796 {
 797         Buffer buffer;
 798         struct pam_ctxt *ctxt = ctx;
 799
 800         debug2("PAM: %s entering, %u responses", __func__, num);
 801         switch (ctxt->pam_done) {
 802         case 1:
 803                 sshpam_authenticated = 1;
 804                 return (0);
 805         case 0:
 806                 break;
 807         default:
 808                 return (-1);
 809         }
 810         if (num != 1) {
 811                 error("PAM: expected one response, got %u", num);
 812                 return (-1);
 813         }
 814         buffer_init(&buffer);
 815         if (sshpam_authctxt->valid &&
 816             (sshpam_authctxt->pw->pw_uid != 0 ||
 817             options.permit_root_login == PERMIT_YES))
 818                 buffer_put_cstring(&buffer, *resp);
 819         else
 820                 buffer_put_cstring(&buffer, badpw);
 821         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 822                 buffer_free(&buffer);
 823                 return (-1);
 824         }
 825         buffer_free(&buffer);
 826         return (1);
 827 }
 828
 829 static void
 830 sshpam_free_ctx(void *ctxtp)
 831 {
 832         struct pam_ctxt *ctxt = ctxtp;
 833
 834         debug3("PAM: %s entering", __func__);
 835         sshpam_thread_cleanup();
 836         xfree(ctxt);
 837         /*
 838          * We don't call sshpam_cleanup() here because we may need the PAM
 839          * handle at a later stage, e.g. when setting up a session.  It's
 840          * still on the cleanup list, so pam_end() *will* be called before
 841          * the server process terminates.
 842          */
 843 }
 844
 845 KbdintDevice sshpam_device = {
 846         "pam",
 847         sshpam_init_ctx,
 848         sshpam_query,
 849         sshpam_respond,
 850         sshpam_free_ctx
 851 };
 852
 853 KbdintDevice mm_sshpam_device = {
 854         "pam",
 855         mm_sshpam_init_ctx,
 856         mm_sshpam_query,
 857         mm_sshpam_respond,
 858         mm_sshpam_free_ctx
 859 };
 860
 861 /*
 862  * This replaces auth-pam.c
 863  */
 864 void
 865 start_pam(Authctxt *authctxt)
 866 {
 867         if (!options.use_pam)
 868                 fatal("PAM: initialisation requested when UsePAM=no");
 869
 870         if (sshpam_init(authctxt) == -1)
 871                 fatal("PAM: initialisation failed");
 872 }
 873
 874 void
 875 finish_pam(void)
 876 {
 877         sshpam_cleanup();
 878 }
 879
 880 u_int
 881 do_pam_account(void)
 882 {
 883         debug("%s: called", __func__);
 884         if (sshpam_account_status != -1)
 885                 return (sshpam_account_status);
 886
 887         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 888         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 889             pam_strerror(sshpam_handle, sshpam_err));
 890
 891         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 892                 sshpam_account_status = 0;
 893                 return (sshpam_account_status);
 894         }
 895
 896         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 897                 sshpam_password_change_required(1);
 898
 899         sshpam_account_status = 1;
 900         return (sshpam_account_status);
 901 }
 902
 903 void
 904 do_pam_set_tty(const char *tty)
 905 {
 906         if (tty != NULL) {
 907                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 908                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 909                 if (sshpam_err != PAM_SUCCESS)
 910                         fatal("PAM: failed to set PAM_TTY: %s",
 911                             pam_strerror(sshpam_handle, sshpam_err));
 912         }
 913 }
 914
 915 void
 916 do_pam_setcred(int init)
 917 {
 918         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 919             (const void *)&store_conv);
 920         if (sshpam_err != PAM_SUCCESS)
 921                 fatal("PAM: failed to set PAM_CONV: %s",
 922                     pam_strerror(sshpam_handle, sshpam_err));
 923         if (init) {
 924                 debug("PAM: establishing credentials");
 925                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 926         } else {
 927                 debug("PAM: reinitializing credentials");
 928                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 929         }
 930         if (sshpam_err == PAM_SUCCESS) {
 931                 sshpam_cred_established = 1;
 932                 return;
 933         }
 934         if (sshpam_authenticated)
 935                 fatal("PAM: pam_setcred(): %s",
 936                     pam_strerror(sshpam_handle, sshpam_err));
 937         else
 938                 debug("PAM: pam_setcred(): %s",
 939                     pam_strerror(sshpam_handle, sshpam_err));
 940 }
 941
 942 static int
 943 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 944     struct pam_response **resp, void *data)
 945 {
 946         char input[PAM_MAX_MSG_SIZE];
 947         struct pam_response *reply;
 948         int i;
 949
 950         debug3("PAM: %s called with %d messages", __func__, n);
 951
 952         *resp = NULL;
 953
 954         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 955                 return (PAM_CONV_ERR);
 956
 957         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 958                 return (PAM_CONV_ERR);
 959
 960         for (i = 0; i < n; ++i) {
 961                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 962                 case PAM_PROMPT_ECHO_OFF:
 963                         reply[i].resp =
 964                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 965                             RP_ALLOW_STDIN);
 966                         reply[i].resp_retcode = PAM_SUCCESS;
 967                         break;
 968                 case PAM_PROMPT_ECHO_ON:
 969                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 970                         fgets(input, sizeof input, stdin);
 971                         if ((reply[i].resp = strdup(input)) == NULL)
 972                                 goto fail;
 973                         reply[i].resp_retcode = PAM_SUCCESS;
 974                         break;
 975                 case PAM_ERROR_MSG:
 976                 case PAM_TEXT_INFO:
 977                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 978                         reply[i].resp_retcode = PAM_SUCCESS;
 979                         break;
 980                 default:
 981                         goto fail;
 982                 }
 983         }
 984         *resp = reply;
 985         return (PAM_SUCCESS);
 986
 987  fail:
 988         for(i = 0; i < n; i++) {
 989                 if (reply[i].resp != NULL)
 990                         xfree(reply[i].resp);
 991         }
 992         xfree(reply);
 993         return (PAM_CONV_ERR);
 994 }
 995
 996 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
 997
 998 /*
 999  * XXX this should be done in the authentication phase, but ssh1 doesn't
1000  * support that
1001  */
1002 void
1003 do_pam_chauthtok(void)
1004 {
1005         if (use_privsep)
1006                 fatal("Password expired (unable to change with privsep)");
1007         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1008             (const void *)&tty_conv);
1009         if (sshpam_err != PAM_SUCCESS)
1010                 fatal("PAM: failed to set PAM_CONV: %s",
1011                     pam_strerror(sshpam_handle, sshpam_err));
1012         debug("PAM: changing password");
1013         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1014         if (sshpam_err != PAM_SUCCESS)
1015                 fatal("PAM: pam_chauthtok(): %s",
1016                     pam_strerror(sshpam_handle, sshpam_err));
1017 }
1018
1019 void
1020 do_pam_session(void)
1021 {
1022         debug3("PAM: opening session");
1023         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1024             (const void *)&store_conv);
1025         if (sshpam_err != PAM_SUCCESS)
1026                 fatal("PAM: failed to set PAM_CONV: %s",
1027                     pam_strerror(sshpam_handle, sshpam_err));
1028         sshpam_err = pam_open_session(sshpam_handle, 0);
1029         if (sshpam_err == PAM_SUCCESS)
1030                 sshpam_session_open = 1;
1031         else {
1032                 sshpam_session_open = 0;
1033                 disable_forwarding();
1034                 error("PAM: pam_open_session(): %s",
1035                     pam_strerror(sshpam_handle, sshpam_err));
1036         }
1037
1038 }
1039
1040 int
1041 is_pam_session_open(void)
1042 {
1043         return sshpam_session_open;
1044 }
1045
1046 /*
1047  * Set a PAM environment string. We need to do this so that the session
1048  * modules can handle things like Kerberos/GSI credentials that appear
1049  * during the ssh authentication process.
1050  */
1051 int
1052 do_pam_putenv(char *name, char *value)
1053 {
1054         int ret = 1;
1055 #ifdef HAVE_PAM_PUTENV
1056         char *compound;
1057         size_t len;
1058
1059         len = strlen(name) + strlen(value) + 2;
1060         compound = xmalloc(len);
1061
1062         snprintf(compound, len, "%s=%s", name, value);
1063         ret = pam_putenv(sshpam_handle, compound);
1064         xfree(compound);
1065 #endif
1066
1067         return (ret);
1068 }
1069
1070 char **
1071 fetch_pam_child_environment(void)
1072 {
1073         return sshpam_env;
1074 }
1075
1076 char **
1077 fetch_pam_environment(void)
1078 {
1079         return (pam_getenvlist(sshpam_handle));
1080 }
1081
1082 void
1083 free_pam_environment(char **env)
1084 {
1085         char **envp;
1086
1087         if (env == NULL)
1088                 return;
1089
1090         for (envp = env; *envp; envp++)
1091                 xfree(*envp);
1092         xfree(env);
1093 }
1094
1095 /*
1096  * "Blind" conversation function for password authentication.  Assumes that
1097  * echo-off prompts are for the password and stores messages for later
1098  * display.
1099  */
1100 static int
1101 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1102     struct pam_response **resp, void *data)
1103 {
1104         struct pam_response *reply;
1105         int i;
1106         size_t len;
1107
1108         debug3("PAM: %s called with %d messages", __func__, n);
1109
1110         *resp = NULL;
1111
1112         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1113                 return (PAM_CONV_ERR);
1114
1115         if ((reply = malloc(n * sizeof(*reply))) == NULL)
1116                 return (PAM_CONV_ERR);
1117         memset(reply, 0, n * sizeof(*reply));
1118
1119         for (i = 0; i < n; ++i) {
1120                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1121                 case PAM_PROMPT_ECHO_OFF:
1122                         if (sshpam_password == NULL)
1123                                 goto fail;
1124                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1125                                 goto fail;
1126                         reply[i].resp_retcode = PAM_SUCCESS;
1127                         break;
1128                 case PAM_ERROR_MSG:
1129                 case PAM_TEXT_INFO:
1130                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1131                         if (len > 0) {
1132                                 buffer_append(&loginmsg,
1133                                     PAM_MSG_MEMBER(msg, i, msg), len);
1134                                 buffer_append(&loginmsg, "\n", 1);
1135                         }
1136                         if ((reply[i].resp = strdup("")) == NULL)
1137                                 goto fail;
1138                         reply[i].resp_retcode = PAM_SUCCESS;
1139                         break;
1140                 default:
1141                         goto fail;
1142                 }
1143         }
1144         *resp = reply;
1145         return (PAM_SUCCESS);
1146
1147  fail:
1148         for(i = 0; i < n; i++) {
1149                 if (reply[i].resp != NULL)
1150                         xfree(reply[i].resp);
1151         }
1152         xfree(reply);
1153         return (PAM_CONV_ERR);
1154 }
1155
1156 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1157
1158 /*
1159  * Attempt password authentication via PAM
1160  */
1161 int
1162 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1163 {
1164         int flags = (options.permit_empty_passwd == 0 ?
1165             PAM_DISALLOW_NULL_AUTHTOK : 0);
1166
1167         if (!options.use_pam || sshpam_handle == NULL)
1168                 fatal("PAM: %s called when PAM disabled or failed to "
1169                     "initialise.", __func__);
1170
1171         sshpam_password = password;
1172         sshpam_authctxt = authctxt;
1173
1174         /*
1175          * If the user logging in is invalid, or is root but is not permitted
1176          * by PermitRootLogin, use an invalid password to prevent leaking
1177          * information via timing (eg if the PAM config has a delay on fail).
1178          */
1179         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1180             options.permit_root_login != PERMIT_YES))
1181                 sshpam_password = badpw;
1182
1183         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1184             (const void *)&passwd_conv);
1185         if (sshpam_err != PAM_SUCCESS)
1186                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1187                     pam_strerror(sshpam_handle, sshpam_err));
1188
1189         sshpam_err = pam_authenticate(sshpam_handle, flags);
1190         sshpam_password = NULL;
1191         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1192                 debug("PAM: password authentication accepted for %.100s",
1193                     authctxt->user);
1194                 return 1;
1195         } else {
1196                 debug("PAM: password authentication failed for %.100s: %s",
1197                     authctxt->valid ? authctxt->user : "an illegal user",
1198                     pam_strerror(sshpam_handle, sshpam_err));
1199                 return 0;
1200         }
1201 }
1202 #endif /* USE_PAM */