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 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
  75 #ifdef PAM_SUN_CODEBASE
  76 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
  77 #else
  78 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
  79 #endif
  80
  81 #include "xmalloc.h"
  82 #include "buffer.h"
  83 #include "key.h"
  84 #include "hostfile.h"
  85 #include "auth.h"
  86 #include "auth-pam.h"
  87 #include "canohost.h"
  88 #include "log.h"
  89 #include "msg.h"
  90 #include "packet.h"
  91 #include "misc.h"
  92 #include "servconf.h"
  93 #include "ssh2.h"
  94 #include "auth-options.h"
  95 #ifdef GSSAPI
  96 #include "ssh-gss.h"
  97 #endif
  98 #include "monitor_wrap.h"
  99
 100 extern ServerOptions options;
 101 extern Buffer loginmsg;
 102 extern int compat20;
 103 extern u_int utmp_len;
 104
 105 /* so we don't silently change behaviour */
 106 #ifdef USE_POSIX_THREADS
 107 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
 108 #endif
 109
 110 /*
 111  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
 112  * and generally a bad idea.  Use at own risk and do not expect support if
 113  * this breaks.
 114  */
 115 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
 116 #include <pthread.h>
 117 /*
 118  * Avoid namespace clash when *not* using pthreads for systems *with*
 119  * pthreads, which unconditionally define pthread_t via sys/types.h
 120  * (e.g. Linux)
 121  */
 122 typedef pthread_t sp_pthread_t;
 123 #else
 124 typedef pid_t sp_pthread_t;
 125 #endif
 126
 127 struct pam_ctxt {
 128         sp_pthread_t     pam_thread;
 129         int              pam_psock;
 130         int              pam_csock;
 131         int              pam_done;
 132 };
 133
 134 static void sshpam_free_ctx(void *);
 135 static struct pam_ctxt *cleanup_ctxt;
 136
 137 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 138 /*
 139  * Simulate threads with processes.
 140  */
 141
 142 static int sshpam_thread_status = -1;
 143 static mysig_t sshpam_oldsig;
 144
 145 static void
 146 sshpam_sigchld_handler(int sig)
 147 {
 148         signal(SIGCHLD, SIG_DFL);
 149         if (cleanup_ctxt == NULL)
 150                 return; /* handler called after PAM cleanup, shouldn't happen */
 151         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 152             <= 0) {
 153                 /* PAM thread has not exitted, privsep slave must have */
 154                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 155                 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
 156                     <= 0)
 157                         return; /* could not wait */
 158         }
 159         if (WIFSIGNALED(sshpam_thread_status) &&
 160             WTERMSIG(sshpam_thread_status) == SIGTERM)
 161                 return; /* terminated by pthread_cancel */
 162         if (!WIFEXITED(sshpam_thread_status))
 163                 fatal("PAM: authentication thread exited unexpectedly");
 164         if (WEXITSTATUS(sshpam_thread_status) != 0)
 165                 fatal("PAM: authentication thread exited uncleanly");
 166 }
 167
 168 /* ARGSUSED */
 169 static void
 170 pthread_exit(void *value)
 171 {
 172         _exit(0);
 173 }
 174
 175 /* ARGSUSED */
 176 static int
 177 pthread_create(sp_pthread_t *thread, const void *attr,
 178     void *(*thread_start)(void *), void *arg)
 179 {
 180         pid_t pid;
 181         struct pam_ctxt *ctx = arg;
 182
 183         sshpam_thread_status = -1;
 184         switch ((pid = fork())) {
 185         case -1:
 186                 error("fork(): %s", strerror(errno));
 187                 return (-1);
 188         case 0:
 189                 close(ctx->pam_psock);
 190                 ctx->pam_psock = -1;
 191                 thread_start(arg);
 192                 _exit(1);
 193         default:
 194                 *thread = pid;
 195                 close(ctx->pam_csock);
 196                 ctx->pam_csock = -1;
 197                 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
 198                 return (0);
 199         }
 200 }
 201
 202 static int
 203 pthread_cancel(sp_pthread_t thread)
 204 {
 205         signal(SIGCHLD, sshpam_oldsig);
 206         return (kill(thread, SIGTERM));
 207 }
 208
 209 /* ARGSUSED */
 210 static int
 211 pthread_join(sp_pthread_t thread, void **value)
 212 {
 213         int status;
 214
 215         if (sshpam_thread_status != -1)
 216                 return (sshpam_thread_status);
 217         signal(SIGCHLD, sshpam_oldsig);
 218         waitpid(thread, &status, 0);
 219         return (status);
 220 }
 221 #endif
 222
 223
 224 static pam_handle_t *sshpam_handle = NULL;
 225 static int sshpam_err = 0;
 226 static int sshpam_authenticated = 0;
 227 static int sshpam_session_open = 0;
 228 static int sshpam_cred_established = 0;
 229 static int sshpam_account_status = -1;
 230 static char **sshpam_env = NULL;
 231 static Authctxt *sshpam_authctxt = NULL;
 232 static const char *sshpam_password = NULL;
 233 static char badpw[] = "\b\n\r\177INCORRECT";
 234
 235 /* Some PAM implementations don't implement this */
 236 #ifndef HAVE_PAM_GETENVLIST
 237 static char **
 238 pam_getenvlist(pam_handle_t *pamh)
 239 {
 240         /*
 241          * XXX - If necessary, we can still support envrionment passing
 242          * for platforms without pam_getenvlist by searching for known
 243          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 244          */
 245          return NULL;
 246 }
 247 #endif
 248
 249 /*
 250  * Some platforms, notably Solaris, do not enforce password complexity
 251  * rules during pam_chauthtok() if the real uid of the calling process
 252  * is 0, on the assumption that it's being called by "passwd" run by root.
 253  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 254  * the right thing.
 255  */
 256 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 257 static int
 258 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 259 {
 260         int result;
 261
 262         if (sshpam_authctxt == NULL)
 263                 fatal("PAM: sshpam_authctxt not initialized");
 264         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 265                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 266         result = pam_chauthtok(pamh, flags);
 267         if (setreuid(0, -1) == -1)
 268                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 269         return result;
 270 }
 271 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 272 #endif
 273
 274 void
 275 sshpam_password_change_required(int reqd)
 276 {
 277         debug3("%s %d", __func__, reqd);
 278         if (sshpam_authctxt == NULL)
 279                 fatal("%s: PAM authctxt not initialized", __func__);
 280         sshpam_authctxt->force_pwchange = reqd;
 281         if (reqd) {
 282                 no_port_forwarding_flag |= 2;
 283                 no_agent_forwarding_flag |= 2;
 284                 no_x11_forwarding_flag |= 2;
 285         } else {
 286                 no_port_forwarding_flag &= ~2;
 287                 no_agent_forwarding_flag &= ~2;
 288                 no_x11_forwarding_flag &= ~2;
 289         }
 290 }
 291
 292 /* Import regular and PAM environment from subprocess */
 293 static void
 294 import_environments(Buffer *b)
 295 {
 296         char *env;
 297         u_int i, num_env;
 298         int err;
 299
 300         debug3("PAM: %s entering", __func__);
 301
 302 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 303         /* Import variables set by do_pam_account */
 304         sshpam_account_status = buffer_get_int(b);
 305         sshpam_password_change_required(buffer_get_int(b));
 306
 307         /* Import environment from subprocess */
 308         num_env = buffer_get_int(b);
 309         if (num_env > 1024)
 310                 fatal("%s: received %u environment variables, expected <= 1024",
 311                     __func__, num_env);
 312         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 313         debug3("PAM: num env strings %d", num_env);
 314         for(i = 0; i < num_env; i++)
 315                 sshpam_env[i] = buffer_get_string(b, NULL);
 316
 317         sshpam_env[num_env] = NULL;
 318
 319         /* Import PAM environment from subprocess */
 320         num_env = buffer_get_int(b);
 321         debug("PAM: num PAM env strings %d", num_env);
 322         for(i = 0; i < num_env; i++) {
 323                 env = buffer_get_string(b, NULL);
 324
 325 #ifdef HAVE_PAM_PUTENV
 326                 /* Errors are not fatal here */
 327                 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 328                         error("PAM: pam_putenv: %s",
 329                             pam_strerror(sshpam_handle, sshpam_err));
 330                 }
 331 #endif
 332         }
 333 #endif
 334 }
 335
 336 /*
 337  * Conversation function for authentication thread.
 338  */
 339 static int
 340 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 341     struct pam_response **resp, void *data)
 342 {
 343         Buffer buffer;
 344         struct pam_ctxt *ctxt;
 345         struct pam_response *reply;
 346         int i;
 347
 348         debug3("PAM: %s entering, %d messages", __func__, n);
 349         *resp = NULL;
 350
 351         if (data == NULL) {
 352                 error("PAM: conversation function passed a null context");
 353                 return (PAM_CONV_ERR);
 354         }
 355         ctxt = data;
 356         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 357                 return (PAM_CONV_ERR);
 358
 359         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 360                 return (PAM_CONV_ERR);
 361
 362         buffer_init(&buffer);
 363         for (i = 0; i < n; ++i) {
 364                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 365                 case PAM_PROMPT_ECHO_OFF:
 366                         buffer_put_cstring(&buffer,
 367                             PAM_MSG_MEMBER(msg, i, msg));
 368                         if (ssh_msg_send(ctxt->pam_csock,
 369                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 370                                 goto fail;
 371                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 372                                 goto fail;
 373                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 374                                 goto fail;
 375                         reply[i].resp = buffer_get_string(&buffer, NULL);
 376                         break;
 377                 case PAM_PROMPT_ECHO_ON:
 378                         buffer_put_cstring(&buffer,
 379                             PAM_MSG_MEMBER(msg, i, msg));
 380                         if (ssh_msg_send(ctxt->pam_csock,
 381                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 382                                 goto fail;
 383                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 384                                 goto fail;
 385                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 386                                 goto fail;
 387                         reply[i].resp = buffer_get_string(&buffer, NULL);
 388                         break;
 389                 case PAM_ERROR_MSG:
 390                         buffer_put_cstring(&buffer,
 391                             PAM_MSG_MEMBER(msg, i, msg));
 392                         if (ssh_msg_send(ctxt->pam_csock,
 393                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 394                                 goto fail;
 395                         break;
 396                 case PAM_TEXT_INFO:
 397                         buffer_put_cstring(&buffer,
 398                             PAM_MSG_MEMBER(msg, i, msg));
 399                         if (ssh_msg_send(ctxt->pam_csock,
 400                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 401                                 goto fail;
 402                         break;
 403                 default:
 404                         goto fail;
 405                 }
 406                 buffer_clear(&buffer);
 407         }
 408         buffer_free(&buffer);
 409         *resp = reply;
 410         return (PAM_SUCCESS);
 411
 412  fail:
 413         for(i = 0; i < n; i++) {
 414                 if (reply[i].resp != NULL)
 415                         xfree(reply[i].resp);
 416         }
 417         xfree(reply);
 418         buffer_free(&buffer);
 419         return (PAM_CONV_ERR);
 420 }
 421
 422 /*
 423  * Authentication thread.
 424  */
 425 static void *
 426 sshpam_thread(void *ctxtp)
 427 {
 428         struct pam_ctxt *ctxt = ctxtp;
 429         Buffer buffer;
 430         struct pam_conv sshpam_conv;
 431         int flags = (options.permit_empty_passwd == 0 ?
 432             PAM_DISALLOW_NULL_AUTHTOK : 0);
 433 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 434         extern char **environ;
 435         char **env_from_pam;
 436         u_int i;
 437         const char *pam_user;
 438         const char **ptr_pam_user = &pam_user;
 439
 440         pam_get_item(sshpam_handle, PAM_USER,
 441             (sshpam_const void **)ptr_pam_user);
 442         environ[0] = NULL;
 443
 444         if (sshpam_authctxt != NULL) {
 445                 setproctitle("%s [pam]",
 446                     sshpam_authctxt->valid ? pam_user : "unknown");
 447         }
 448 #endif
 449
 450         sshpam_conv.conv = sshpam_thread_conv;
 451         sshpam_conv.appdata_ptr = ctxt;
 452
 453         if (sshpam_authctxt == NULL)
 454                 fatal("%s: PAM authctxt not initialized", __func__);
 455
 456         buffer_init(&buffer);
 457         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 458             (const void *)&sshpam_conv);
 459         if (sshpam_err != PAM_SUCCESS)
 460                 goto auth_fail;
 461         sshpam_err = pam_authenticate(sshpam_handle, flags);
 462         if (sshpam_err != PAM_SUCCESS)
 463                 goto auth_fail;
 464
 465         if (compat20) {
 466                 if (!do_pam_account()) {
 467                         sshpam_err = PAM_ACCT_EXPIRED;
 468                         goto auth_fail;
 469                 }
 470                 if (sshpam_authctxt->force_pwchange) {
 471                         sshpam_err = pam_chauthtok(sshpam_handle,
 472                             PAM_CHANGE_EXPIRED_AUTHTOK);
 473                         if (sshpam_err != PAM_SUCCESS)
 474                                 goto auth_fail;
 475                         sshpam_password_change_required(0);
 476                 }
 477         }
 478
 479         buffer_put_cstring(&buffer, "OK");
 480
 481 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 482         /* Export variables set by do_pam_account */
 483         buffer_put_int(&buffer, sshpam_account_status);
 484         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 485
 486         /* Export any environment strings set in child */
 487         for(i = 0; environ[i] != NULL; i++)
 488                 ; /* Count */
 489         buffer_put_int(&buffer, i);
 490         for(i = 0; environ[i] != NULL; i++)
 491                 buffer_put_cstring(&buffer, environ[i]);
 492
 493         /* Export any environment strings set by PAM in child */
 494         env_from_pam = pam_getenvlist(sshpam_handle);
 495         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 496                 ; /* Count */
 497         buffer_put_int(&buffer, i);
 498         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 499                 buffer_put_cstring(&buffer, env_from_pam[i]);
 500 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 501
 502         /* XXX - can't do much about an error here */
 503         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 504         buffer_free(&buffer);
 505         pthread_exit(NULL);
 506
 507  auth_fail:
 508         buffer_put_cstring(&buffer,
 509             pam_strerror(sshpam_handle, sshpam_err));
 510         /* XXX - can't do much about an error here */
 511         if (sshpam_err == PAM_ACCT_EXPIRED)
 512                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);
 513         else
 514                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 515         buffer_free(&buffer);
 516         pthread_exit(NULL);
 517
 518         return (NULL); /* Avoid warning for non-pthread case */
 519 }
 520
 521 void
 522 sshpam_thread_cleanup(void)
 523 {
 524         struct pam_ctxt *ctxt = cleanup_ctxt;
 525
 526         debug3("PAM: %s entering", __func__);
 527         if (ctxt != NULL && ctxt->pam_thread != 0) {
 528                 pthread_cancel(ctxt->pam_thread);
 529                 pthread_join(ctxt->pam_thread, NULL);
 530                 close(ctxt->pam_psock);
 531                 close(ctxt->pam_csock);
 532                 memset(ctxt, 0, sizeof(*ctxt));
 533                 cleanup_ctxt = NULL;
 534         }
 535 }
 536
 537 static int
 538 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 539     struct pam_response **resp, void *data)
 540 {
 541         debug3("PAM: %s entering, %d messages", __func__, n);
 542         return (PAM_CONV_ERR);
 543 }
 544
 545 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 546
 547 static int
 548 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 549     struct pam_response **resp, void *data)
 550 {
 551         struct pam_response *reply;
 552         int i;
 553         size_t len;
 554
 555         debug3("PAM: %s called with %d messages", __func__, n);
 556         *resp = NULL;
 557
 558         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 559                 return (PAM_CONV_ERR);
 560
 561         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 562                 return (PAM_CONV_ERR);
 563
 564         for (i = 0; i < n; ++i) {
 565                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 566                 case PAM_ERROR_MSG:
 567                 case PAM_TEXT_INFO:
 568                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 569                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 570                         buffer_append(&loginmsg, "\n", 1 );
 571                         reply[i].resp_retcode = PAM_SUCCESS;
 572                         break;
 573                 default:
 574                         goto fail;
 575                 }
 576         }
 577         *resp = reply;
 578         return (PAM_SUCCESS);
 579
 580  fail:
 581         for(i = 0; i < n; i++) {
 582                 if (reply[i].resp != NULL)
 583                         xfree(reply[i].resp);
 584         }
 585         xfree(reply);
 586         return (PAM_CONV_ERR);
 587 }
 588
 589 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 590
 591 void
 592 sshpam_cleanup(void)
 593 {
 594         debug("PAM: cleanup");
 595         if (sshpam_handle == NULL)
 596                 return;
 597         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 598         if (sshpam_cred_established) {
 599                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 600                 sshpam_cred_established = 0;
 601         }
 602         if (sshpam_session_open) {
 603                 pam_close_session(sshpam_handle, PAM_SILENT);
 604                 sshpam_session_open = 0;
 605         }
 606         sshpam_authenticated = 0;
 607         pam_end(sshpam_handle, sshpam_err);
 608         sshpam_handle = NULL;
 609 }
 610
 611 static int
 612 sshpam_init(Authctxt *authctxt)
 613 {
 614         extern char *__progname;
 615         const char *pam_rhost, *pam_user, *user = authctxt->user;
 616         const char **ptr_pam_user = &pam_user;
 617
 618         if (sshpam_handle != NULL) {
 619                 /* We already have a PAM context; check if the user matches */
 620                 sshpam_err = pam_get_item(sshpam_handle,
 621                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 622                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 623                         return (0);
 624                 pam_end(sshpam_handle, sshpam_err);
 625                 sshpam_handle = NULL;
 626         }
 627         debug("PAM: initializing for \"%s\"", user);
 628         sshpam_err =
 629             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 630         sshpam_authctxt = authctxt;
 631
 632         if (sshpam_err != PAM_SUCCESS) {
 633                 pam_end(sshpam_handle, sshpam_err);
 634                 sshpam_handle = NULL;
 635                 return (-1);
 636         }
 637         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 638         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 639         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 640         if (sshpam_err != PAM_SUCCESS) {
 641                 pam_end(sshpam_handle, sshpam_err);
 642                 sshpam_handle = NULL;
 643                 return (-1);
 644         }
 645 #ifdef PAM_TTY_KLUDGE
 646         /*
 647          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 648          * sshd doesn't set the tty until too late in the auth process and
 649          * may not even set one (for tty-less connections)
 650          */
 651         debug("PAM: setting PAM_TTY to \"ssh\"");
 652         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 653         if (sshpam_err != PAM_SUCCESS) {
 654                 pam_end(sshpam_handle, sshpam_err);
 655                 sshpam_handle = NULL;
 656                 return (-1);
 657         }
 658 #endif
 659         return (0);
 660 }
 661
 662 static void *
 663 sshpam_init_ctx(Authctxt *authctxt)
 664 {
 665         struct pam_ctxt *ctxt;
 666         int socks[2];
 667
 668         debug3("PAM: %s entering", __func__);
 669         /*
 670          * Refuse to start if we don't have PAM enabled or do_pam_account
 671          * has previously failed.
 672          */
 673         if (!options.use_pam || sshpam_account_status == 0)
 674                 return NULL;
 675
 676         /* Initialize PAM */
 677         if (sshpam_init(authctxt) == -1) {
 678                 error("PAM: initialization failed");
 679                 return (NULL);
 680         }
 681
 682         ctxt = xmalloc(sizeof *ctxt);
 683         memset(ctxt, 0, sizeof(*ctxt));
 684
 685         /* Start the authentication thread */
 686         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 687                 error("PAM: failed create sockets: %s", strerror(errno));
 688                 xfree(ctxt);
 689                 return (NULL);
 690         }
 691         ctxt->pam_psock = socks[0];
 692         ctxt->pam_csock = socks[1];
 693         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 694                 error("PAM: failed to start authentication thread: %s",
 695                     strerror(errno));
 696                 close(socks[0]);
 697                 close(socks[1]);
 698                 xfree(ctxt);
 699                 return (NULL);
 700         }
 701         cleanup_ctxt = ctxt;
 702         return (ctxt);
 703 }
 704
 705 static int
 706 sshpam_query(void *ctx, char **name, char **info,
 707     u_int *num, char ***prompts, u_int **echo_on)
 708 {
 709         Buffer buffer;
 710         struct pam_ctxt *ctxt = ctx;
 711         size_t plen;
 712         u_char type;
 713         char *msg;
 714         size_t len, mlen;
 715
 716         debug3("PAM: %s entering", __func__);
 717         buffer_init(&buffer);
 718         *name = xstrdup("");
 719         *info = xstrdup("");
 720         *prompts = xmalloc(sizeof(char *));
 721         **prompts = NULL;
 722         plen = 0;
 723         *echo_on = xmalloc(sizeof(u_int));
 724         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 725                 type = buffer_get_char(&buffer);
 726                 msg = buffer_get_string(&buffer, NULL);
 727                 mlen = strlen(msg);
 728                 switch (type) {
 729                 case PAM_PROMPT_ECHO_ON:
 730                 case PAM_PROMPT_ECHO_OFF:
 731                         *num = 1;
 732                         len = plen + mlen + 1;
 733                         **prompts = xrealloc(**prompts, 1, len);
 734                         strlcpy(**prompts + plen, msg, len - plen);
 735                         plen += mlen;
 736                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 737                         xfree(msg);
 738                         return (0);
 739                 case PAM_ERROR_MSG:
 740                 case PAM_TEXT_INFO:
 741                         /* accumulate messages */
 742                         len = plen + mlen + 2;
 743                         **prompts = xrealloc(**prompts, 1, len);
 744                         strlcpy(**prompts + plen, msg, len - plen);
 745                         plen += mlen;
 746                         strlcat(**prompts + plen, "\n", len - plen);
 747                         plen++;
 748                         xfree(msg);
 749                         break;
 750                 case PAM_ACCT_EXPIRED:
 751                         sshpam_account_status = 0;
 752                         /* FALLTHROUGH */
 753                 case PAM_AUTH_ERR:
 754                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 755                         if (**prompts != NULL && strlen(**prompts) != 0) {
 756                                 *info = **prompts;
 757                                 **prompts = NULL;
 758                                 *num = 0;
 759                                 **echo_on = 0;
 760                                 ctxt->pam_done = -1;
 761                                 xfree(msg);
 762                                 return 0;
 763                         }
 764                         /* FALLTHROUGH */
 765                 case PAM_SUCCESS:
 766                         if (**prompts != NULL) {
 767                                 /* drain any accumulated messages */
 768                                 debug("PAM: %s", **prompts);
 769                                 buffer_append(&loginmsg, **prompts,
 770                                     strlen(**prompts));
 771                                 xfree(**prompts);
 772                                 **prompts = NULL;
 773                         }
 774                         if (type == PAM_SUCCESS) {
 775                                 if (!sshpam_authctxt->valid ||
 776                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 777                                     options.permit_root_login != PERMIT_YES))
 778                                         fatal("Internal error: PAM auth "
 779                                             "succeeded when it should have "
 780                                             "failed");
 781                                 import_environments(&buffer);
 782                                 *num = 0;
 783                                 **echo_on = 0;
 784                                 ctxt->pam_done = 1;
 785                                 xfree(msg);
 786                                 return (0);
 787                         }
 788                         error("PAM: %s for %s%.100s from %.100s", msg,
 789                             sshpam_authctxt->valid ? "" : "illegal user ",
 790                             sshpam_authctxt->user,
 791                             get_remote_name_or_ip(utmp_len, options.use_dns));
 792                         /* FALLTHROUGH */
 793                 default:
 794                         *num = 0;
 795                         **echo_on = 0;
 796                         xfree(msg);
 797                         ctxt->pam_done = -1;
 798                         return (-1);
 799                 }
 800         }
 801         return (-1);
 802 }
 803
 804 /* XXX - see also comment in auth-chall.c:verify_response */
 805 static int
 806 sshpam_respond(void *ctx, u_int num, char **resp)
 807 {
 808         Buffer buffer;
 809         struct pam_ctxt *ctxt = ctx;
 810
 811         debug2("PAM: %s entering, %u responses", __func__, num);
 812         switch (ctxt->pam_done) {
 813         case 1:
 814                 sshpam_authenticated = 1;
 815                 return (0);
 816         case 0:
 817                 break;
 818         default:
 819                 return (-1);
 820         }
 821         if (num != 1) {
 822                 error("PAM: expected one response, got %u", num);
 823                 return (-1);
 824         }
 825         buffer_init(&buffer);
 826         if (sshpam_authctxt->valid &&
 827             (sshpam_authctxt->pw->pw_uid != 0 ||
 828             options.permit_root_login == PERMIT_YES))
 829                 buffer_put_cstring(&buffer, *resp);
 830         else
 831                 buffer_put_cstring(&buffer, badpw);
 832         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 833                 buffer_free(&buffer);
 834                 return (-1);
 835         }
 836         buffer_free(&buffer);
 837         return (1);
 838 }
 839
 840 static void
 841 sshpam_free_ctx(void *ctxtp)
 842 {
 843         struct pam_ctxt *ctxt = ctxtp;
 844
 845         debug3("PAM: %s entering", __func__);
 846         sshpam_thread_cleanup();
 847         xfree(ctxt);
 848         /*
 849          * We don't call sshpam_cleanup() here because we may need the PAM
 850          * handle at a later stage, e.g. when setting up a session.  It's
 851          * still on the cleanup list, so pam_end() *will* be called before
 852          * the server process terminates.
 853          */
 854 }
 855
 856 KbdintDevice sshpam_device = {
 857         "pam",
 858         sshpam_init_ctx,
 859         sshpam_query,
 860         sshpam_respond,
 861         sshpam_free_ctx
 862 };
 863
 864 KbdintDevice mm_sshpam_device = {
 865         "pam",
 866         mm_sshpam_init_ctx,
 867         mm_sshpam_query,
 868         mm_sshpam_respond,
 869         mm_sshpam_free_ctx
 870 };
 871
 872 /*
 873  * This replaces auth-pam.c
 874  */
 875 void
 876 start_pam(Authctxt *authctxt)
 877 {
 878         if (!options.use_pam)
 879                 fatal("PAM: initialisation requested when UsePAM=no");
 880
 881         if (sshpam_init(authctxt) == -1)
 882                 fatal("PAM: initialisation failed");
 883 }
 884
 885 void
 886 finish_pam(void)
 887 {
 888         sshpam_cleanup();
 889 }
 890
 891 u_int
 892 do_pam_account(void)
 893 {
 894         debug("%s: called", __func__);
 895         if (sshpam_account_status != -1)
 896                 return (sshpam_account_status);
 897
 898         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 899         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 900             pam_strerror(sshpam_handle, sshpam_err));
 901
 902         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 903                 sshpam_account_status = 0;
 904                 return (sshpam_account_status);
 905         }
 906
 907         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 908                 sshpam_password_change_required(1);
 909
 910         sshpam_account_status = 1;
 911         return (sshpam_account_status);
 912 }
 913
 914 void
 915 do_pam_set_tty(const char *tty)
 916 {
 917         if (tty != NULL) {
 918                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 919                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 920                 if (sshpam_err != PAM_SUCCESS)
 921                         fatal("PAM: failed to set PAM_TTY: %s",
 922                             pam_strerror(sshpam_handle, sshpam_err));
 923         }
 924 }
 925
 926 void
 927 do_pam_setcred(int init)
 928 {
 929         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 930             (const void *)&store_conv);
 931         if (sshpam_err != PAM_SUCCESS)
 932                 fatal("PAM: failed to set PAM_CONV: %s",
 933                     pam_strerror(sshpam_handle, sshpam_err));
 934         if (init) {
 935                 debug("PAM: establishing credentials");
 936                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 937         } else {
 938                 debug("PAM: reinitializing credentials");
 939                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 940         }
 941         if (sshpam_err == PAM_SUCCESS) {
 942                 sshpam_cred_established = 1;
 943                 return;
 944         }
 945         if (sshpam_authenticated)
 946                 fatal("PAM: pam_setcred(): %s",
 947                     pam_strerror(sshpam_handle, sshpam_err));
 948         else
 949                 debug("PAM: pam_setcred(): %s",
 950                     pam_strerror(sshpam_handle, sshpam_err));
 951 }
 952
 953 static int
 954 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 955     struct pam_response **resp, void *data)
 956 {
 957         char input[PAM_MAX_MSG_SIZE];
 958         struct pam_response *reply;
 959         int i;
 960
 961         debug3("PAM: %s called with %d messages", __func__, n);
 962
 963         *resp = NULL;
 964
 965         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 966                 return (PAM_CONV_ERR);
 967
 968         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 969                 return (PAM_CONV_ERR);
 970
 971         for (i = 0; i < n; ++i) {
 972                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 973                 case PAM_PROMPT_ECHO_OFF:
 974                         reply[i].resp =
 975                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 976                             RP_ALLOW_STDIN);
 977                         reply[i].resp_retcode = PAM_SUCCESS;
 978                         break;
 979                 case PAM_PROMPT_ECHO_ON:
 980                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 981                         fgets(input, sizeof input, stdin);
 982                         if ((reply[i].resp = strdup(input)) == NULL)
 983                                 goto fail;
 984                         reply[i].resp_retcode = PAM_SUCCESS;
 985                         break;
 986                 case PAM_ERROR_MSG:
 987                 case PAM_TEXT_INFO:
 988                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 989                         reply[i].resp_retcode = PAM_SUCCESS;
 990                         break;
 991                 default:
 992                         goto fail;
 993                 }
 994         }
 995         *resp = reply;
 996         return (PAM_SUCCESS);
 997
 998  fail:
 999         for(i = 0; i < n; i++) {
1000                 if (reply[i].resp != NULL)
1001                         xfree(reply[i].resp);
1002         }
1003         xfree(reply);
1004         return (PAM_CONV_ERR);
1005 }
1006
1007 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1008
1009 /*
1010  * XXX this should be done in the authentication phase, but ssh1 doesn't
1011  * support that
1012  */
1013 void
1014 do_pam_chauthtok(void)
1015 {
1016         if (use_privsep)
1017                 fatal("Password expired (unable to change with privsep)");
1018         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1019             (const void *)&tty_conv);
1020         if (sshpam_err != PAM_SUCCESS)
1021                 fatal("PAM: failed to set PAM_CONV: %s",
1022                     pam_strerror(sshpam_handle, sshpam_err));
1023         debug("PAM: changing password");
1024         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1025         if (sshpam_err != PAM_SUCCESS)
1026                 fatal("PAM: pam_chauthtok(): %s",
1027                     pam_strerror(sshpam_handle, sshpam_err));
1028 }
1029
1030 void
1031 do_pam_session(void)
1032 {
1033         debug3("PAM: opening session");
1034         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1035             (const void *)&store_conv);
1036         if (sshpam_err != PAM_SUCCESS)
1037                 fatal("PAM: failed to set PAM_CONV: %s",
1038                     pam_strerror(sshpam_handle, sshpam_err));
1039         sshpam_err = pam_open_session(sshpam_handle, 0);
1040         if (sshpam_err == PAM_SUCCESS)
1041                 sshpam_session_open = 1;
1042         else {
1043                 sshpam_session_open = 0;
1044                 disable_forwarding();
1045                 error("PAM: pam_open_session(): %s",
1046                     pam_strerror(sshpam_handle, sshpam_err));
1047         }
1048
1049 }
1050
1051 int
1052 is_pam_session_open(void)
1053 {
1054         return sshpam_session_open;
1055 }
1056
1057 /*
1058  * Set a PAM environment string. We need to do this so that the session
1059  * modules can handle things like Kerberos/GSI credentials that appear
1060  * during the ssh authentication process.
1061  */
1062 int
1063 do_pam_putenv(char *name, char *value)
1064 {
1065         int ret = 1;
1066 #ifdef HAVE_PAM_PUTENV
1067         char *compound;
1068         size_t len;
1069
1070         len = strlen(name) + strlen(value) + 2;
1071         compound = xmalloc(len);
1072
1073         snprintf(compound, len, "%s=%s", name, value);
1074         ret = pam_putenv(sshpam_handle, compound);
1075         xfree(compound);
1076 #endif
1077
1078         return (ret);
1079 }
1080
1081 char **
1082 fetch_pam_child_environment(void)
1083 {
1084         return sshpam_env;
1085 }
1086
1087 char **
1088 fetch_pam_environment(void)
1089 {
1090         return (pam_getenvlist(sshpam_handle));
1091 }
1092
1093 void
1094 free_pam_environment(char **env)
1095 {
1096         char **envp;
1097
1098         if (env == NULL)
1099                 return;
1100
1101         for (envp = env; *envp; envp++)
1102                 xfree(*envp);
1103         xfree(env);
1104 }
1105
1106 /*
1107  * "Blind" conversation function for password authentication.  Assumes that
1108  * echo-off prompts are for the password and stores messages for later
1109  * display.
1110  */
1111 static int
1112 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1113     struct pam_response **resp, void *data)
1114 {
1115         struct pam_response *reply;
1116         int i;
1117         size_t len;
1118
1119         debug3("PAM: %s called with %d messages", __func__, n);
1120
1121         *resp = NULL;
1122
1123         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1124                 return (PAM_CONV_ERR);
1125
1126         if ((reply = malloc(n * sizeof(*reply))) == NULL)
1127                 return (PAM_CONV_ERR);
1128         memset(reply, 0, n * sizeof(*reply));
1129
1130         for (i = 0; i < n; ++i) {
1131                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1132                 case PAM_PROMPT_ECHO_OFF:
1133                         if (sshpam_password == NULL)
1134                                 goto fail;
1135                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1136                                 goto fail;
1137                         reply[i].resp_retcode = PAM_SUCCESS;
1138                         break;
1139                 case PAM_ERROR_MSG:
1140                 case PAM_TEXT_INFO:
1141                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1142                         if (len > 0) {
1143                                 buffer_append(&loginmsg,
1144                                     PAM_MSG_MEMBER(msg, i, msg), len);
1145                                 buffer_append(&loginmsg, "\n", 1);
1146                         }
1147                         if ((reply[i].resp = strdup("")) == NULL)
1148                                 goto fail;
1149                         reply[i].resp_retcode = PAM_SUCCESS;
1150                         break;
1151                 default:
1152                         goto fail;
1153                 }
1154         }
1155         *resp = reply;
1156         return (PAM_SUCCESS);
1157
1158  fail:
1159         for(i = 0; i < n; i++) {
1160                 if (reply[i].resp != NULL)
1161                         xfree(reply[i].resp);
1162         }
1163         xfree(reply);
1164         return (PAM_CONV_ERR);
1165 }
1166
1167 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1168
1169 /*
1170  * Attempt password authentication via PAM
1171  */
1172 int
1173 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1174 {
1175         int flags = (options.permit_empty_passwd == 0 ?
1176             PAM_DISALLOW_NULL_AUTHTOK : 0);
1177
1178         if (!options.use_pam || sshpam_handle == NULL)
1179                 fatal("PAM: %s called when PAM disabled or failed to "
1180                     "initialise.", __func__);
1181
1182         sshpam_password = password;
1183         sshpam_authctxt = authctxt;
1184
1185         /*
1186          * If the user logging in is invalid, or is root but is not permitted
1187          * by PermitRootLogin, use an invalid password to prevent leaking
1188          * information via timing (eg if the PAM config has a delay on fail).
1189          */
1190         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1191             options.permit_root_login != PERMIT_YES))
1192                 sshpam_password = badpw;
1193
1194         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1195             (const void *)&passwd_conv);
1196         if (sshpam_err != PAM_SUCCESS)
1197                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1198                     pam_strerror(sshpam_handle, sshpam_err));
1199
1200         sshpam_err = pam_authenticate(sshpam_handle, flags);
1201         sshpam_password = NULL;
1202         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1203                 debug("PAM: password authentication accepted for %.100s",
1204                     authctxt->user);
1205                 return 1;
1206         } else {
1207                 debug("PAM: password authentication failed for %.100s: %s",
1208                     authctxt->valid ? authctxt->user : "an illegal user",
1209                     pam_strerror(sshpam_handle, sshpam_err));
1210                 return 0;
1211         }
1212 }
1213 #endif /* USE_PAM */