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