crypto/openssh/auth-pam.c

   1 /*-
   2  * Copyright (c) 2002 Networks Associates Technology, Inc.
   3  * All rights reserved.
   4  *
   5  * This software was developed for the FreeBSD Project by ThinkSec AS and
   6  * NAI Labs, the Security Research Division of Network Associates, Inc.
   7  * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
   8  * DARPA CHATS research program.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31 /*
  32  * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org>
  33  * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au>
  34  *
  35  * Permission to use, copy, modify, and distribute this software for any
  36  * purpose with or without fee is hereby granted, provided that the above
  37  * copyright notice and this permission notice appear in all copies.
  38  *
  39  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  40  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  41  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  42  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  43  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  44  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  45  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  46  */
  47
  48 /* Based on $xFreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des Exp $ */
  49 #include "includes.h"
  50 RCSID("$Id: auth-pam.c,v 1.128 2006/01/29 05:46:13 dtucker Exp $");
  51 RCSID("$FreeBSD$");
  52
  53 #ifdef USE_PAM
  54 #if defined(HAVE_SECURITY_PAM_APPL_H)
  55 #include <security/pam_appl.h>
  56 #elif defined (HAVE_PAM_PAM_APPL_H)
  57 #include <pam/pam_appl.h>
  58 #endif
  59
  60 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
  61 #ifdef PAM_SUN_CODEBASE
  62 # define sshpam_const           /* Solaris, HP-UX, AIX */
  63 #else
  64 # define sshpam_const   const   /* LinuxPAM, OpenPAM */
  65 #endif
  66
  67 #include "auth.h"
  68 #include "auth-pam.h"
  69 #include "buffer.h"
  70 #include "bufaux.h"
  71 #include "canohost.h"
  72 #include "log.h"
  73 #include "monitor_wrap.h"
  74 #include "msg.h"
  75 #include "packet.h"
  76 #include "misc.h"
  77 #include "servconf.h"
  78 #include "ssh2.h"
  79 #include "xmalloc.h"
  80 #include "auth-options.h"
  81
  82 extern ServerOptions options;
  83 extern Buffer loginmsg;
  84 extern int compat20;
  85 extern u_int utmp_len;
  86
  87 /* so we don't silently change behaviour */
  88 #ifdef USE_POSIX_THREADS
  89 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
  90 #endif
  91
  92 /*
  93  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
  94  * and generally a bad idea.  Use at own risk and do not expect support if
  95  * this breaks.
  96  */
  97 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
  98 #include <pthread.h>
  99 /*
 100  * Avoid namespace clash when *not* using pthreads for systems *with*
 101  * pthreads, which unconditionally define pthread_t via sys/types.h
 102  * (e.g. Linux)
 103  */
 104 typedef pthread_t sp_pthread_t;
 105 #else
 106 typedef pid_t sp_pthread_t;
 107 #endif
 108
 109 struct pam_ctxt {
 110         sp_pthread_t     pam_thread;
 111         int              pam_psock;
 112         int              pam_csock;
 113         int              pam_done;
 114 };
 115
 116 static void sshpam_free_ctx(void *);
 117 static struct pam_ctxt *cleanup_ctxt;
 118
 119 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 120 /*
 121  * Simulate threads with processes.
 122  */
 123
 124 static int sshpam_thread_status = -1;
 125 static mysig_t sshpam_oldsig;
 126
 127 static void
 128 sshpam_sigchld_handler(int sig)
 129 {
 130         signal(SIGCHLD, SIG_DFL);
 131         if (cleanup_ctxt == NULL)
 132                 return; /* handler called after PAM cleanup, shouldn't happen */
 133         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 134             <= 0) {
 135                 /* PAM thread has not exitted, privsep slave must have */
 136                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 137                 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
 138                     <= 0)
 139                         return; /* could not wait */
 140         }
 141         if (WIFSIGNALED(sshpam_thread_status) &&
 142             WTERMSIG(sshpam_thread_status) == SIGTERM)
 143                 return; /* terminated by pthread_cancel */
 144         if (!WIFEXITED(sshpam_thread_status))
 145                 fatal("PAM: authentication thread exited unexpectedly");
 146         if (WEXITSTATUS(sshpam_thread_status) != 0)
 147                 fatal("PAM: authentication thread exited uncleanly");
 148 }
 149
 150 static void
 151 pthread_exit(void *value __unused)
 152 {
 153         _exit(0);
 154 }
 155
 156 static int
 157 pthread_create(sp_pthread_t *thread, const void *attr __unused,
 158     void *(*thread_start)(void *), void *arg)
 159 {
 160         pid_t pid;
 161         struct pam_ctxt *ctx = arg;
 162
 163         sshpam_thread_status = -1;
 164         switch ((pid = fork())) {
 165         case -1:
 166                 error("fork(): %s", strerror(errno));
 167                 return (-1);
 168         case 0:
 169                 close(ctx->pam_psock);
 170                 ctx->pam_psock = -1;
 171                 thread_start(arg);
 172                 _exit(1);
 173         default:
 174                 *thread = pid;
 175                 close(ctx->pam_csock);
 176                 ctx->pam_csock = -1;
 177                 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
 178                 return (0);
 179         }
 180 }
 181
 182 static int
 183 pthread_cancel(sp_pthread_t thread)
 184 {
 185         signal(SIGCHLD, sshpam_oldsig);
 186         return (kill(thread, SIGTERM));
 187 }
 188
 189 static int
 190 pthread_join(sp_pthread_t thread, void **value __unused)
 191 {
 192         int status;
 193
 194         if (sshpam_thread_status != -1)
 195                 return (sshpam_thread_status);
 196         signal(SIGCHLD, sshpam_oldsig);
 197         waitpid(thread, &status, 0);
 198         return (status);
 199 }
 200 #endif
 201
 202
 203 static pam_handle_t *sshpam_handle = NULL;
 204 static int sshpam_err = 0;
 205 static int sshpam_authenticated = 0;
 206 static int sshpam_session_open = 0;
 207 static int sshpam_cred_established = 0;
 208 static int sshpam_account_status = -1;
 209 static char **sshpam_env = NULL;
 210 static Authctxt *sshpam_authctxt = NULL;
 211 static const char *sshpam_password = NULL;
 212 static char badpw[] = "\b\n\r\177INCORRECT";
 213
 214 /* Some PAM implementations don't implement this */
 215 #ifndef HAVE_PAM_GETENVLIST
 216 static char **
 217 pam_getenvlist(pam_handle_t *pamh)
 218 {
 219         /*
 220          * XXX - If necessary, we can still support envrionment passing
 221          * for platforms without pam_getenvlist by searching for known
 222          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 223          */
 224          return NULL;
 225 }
 226 #endif
 227
 228 /*
 229  * Some platforms, notably Solaris, do not enforce password complexity
 230  * rules during pam_chauthtok() if the real uid of the calling process
 231  * is 0, on the assumption that it's being called by "passwd" run by root.
 232  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 233  * the right thing.
 234  */
 235 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 236 static int
 237 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 238 {
 239         int result;
 240
 241         if (sshpam_authctxt == NULL)
 242                 fatal("PAM: sshpam_authctxt not initialized");
 243         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 244                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 245         result = pam_chauthtok(pamh, flags);
 246         if (setreuid(0, -1) == -1)
 247                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 248         return result;
 249 }
 250 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 251 #endif
 252
 253 void
 254 sshpam_password_change_required(int reqd)
 255 {
 256         debug3("%s %d", __func__, reqd);
 257         if (sshpam_authctxt == NULL)
 258                 fatal("%s: PAM authctxt not initialized", __func__);
 259         sshpam_authctxt->force_pwchange = reqd;
 260         if (reqd) {
 261                 no_port_forwarding_flag |= 2;
 262                 no_agent_forwarding_flag |= 2;
 263                 no_x11_forwarding_flag |= 2;
 264         } else {
 265                 no_port_forwarding_flag &= ~2;
 266                 no_agent_forwarding_flag &= ~2;
 267                 no_x11_forwarding_flag &= ~2;
 268         }
 269 }
 270
 271 /* Import regular and PAM environment from subprocess */
 272 static void
 273 import_environments(Buffer *b)
 274 {
 275         char *env;
 276         u_int i, num_env;
 277         int err;
 278
 279         debug3("PAM: %s entering", __func__);
 280
 281 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 282         /* Import variables set by do_pam_account */
 283         sshpam_account_status = buffer_get_int(b);
 284         sshpam_password_change_required(buffer_get_int(b));
 285
 286         /* Import environment from subprocess */
 287         num_env = buffer_get_int(b);
 288         sshpam_env = xmalloc((num_env + 1) * sizeof(*sshpam_env));
 289         debug3("PAM: num env strings %d", num_env);
 290         for(i = 0; i < num_env; i++)
 291                 sshpam_env[i] = buffer_get_string(b, NULL);
 292
 293         sshpam_env[num_env] = NULL;
 294
 295         /* Import PAM environment from subprocess */
 296         num_env = buffer_get_int(b);
 297         debug("PAM: num PAM env strings %d", num_env);
 298         for(i = 0; i < num_env; i++) {
 299                 env = buffer_get_string(b, NULL);
 300
 301 #ifdef HAVE_PAM_PUTENV
 302                 /* Errors are not fatal here */
 303                 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 304                         error("PAM: pam_putenv: %s",
 305                             pam_strerror(sshpam_handle, sshpam_err));
 306                 }
 307 #endif
 308         }
 309 #endif
 310 }
 311
 312 /*
 313  * Conversation function for authentication thread.
 314  */
 315 static int
 316 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 317     struct pam_response **resp, void *data)
 318 {
 319         Buffer buffer;
 320         struct pam_ctxt *ctxt;
 321         struct pam_response *reply;
 322         int i;
 323
 324         debug3("PAM: %s entering, %d messages", __func__, n);
 325         *resp = NULL;
 326
 327         if (data == NULL) {
 328                 error("PAM: conversation function passed a null context");
 329                 return (PAM_CONV_ERR);
 330         }
 331         ctxt = data;
 332         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 333                 return (PAM_CONV_ERR);
 334
 335         if ((reply = malloc(n * sizeof(*reply))) == NULL)
 336                 return (PAM_CONV_ERR);
 337         memset(reply, 0, n * sizeof(*reply));
 338
 339         buffer_init(&buffer);
 340         for (i = 0; i < n; ++i) {
 341                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 342                 case PAM_PROMPT_ECHO_OFF:
 343                         buffer_put_cstring(&buffer,
 344                             PAM_MSG_MEMBER(msg, i, msg));
 345                         if (ssh_msg_send(ctxt->pam_csock,
 346                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 347                                 goto fail;
 348                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 349                                 goto fail;
 350                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 351                                 goto fail;
 352                         reply[i].resp = buffer_get_string(&buffer, NULL);
 353                         break;
 354                 case PAM_PROMPT_ECHO_ON:
 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_ERROR_MSG:
 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                         break;
 373                 case PAM_TEXT_INFO:
 374                         buffer_put_cstring(&buffer,
 375                             PAM_MSG_MEMBER(msg, i, msg));
 376                         if (ssh_msg_send(ctxt->pam_csock,
 377                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 378                                 goto fail;
 379                         break;
 380                 default:
 381                         goto fail;
 382                 }
 383                 buffer_clear(&buffer);
 384         }
 385         buffer_free(&buffer);
 386         *resp = reply;
 387         return (PAM_SUCCESS);
 388
 389  fail:
 390         for(i = 0; i < n; i++) {
 391                 if (reply[i].resp != NULL)
 392                         xfree(reply[i].resp);
 393         }
 394         xfree(reply);
 395         buffer_free(&buffer);
 396         return (PAM_CONV_ERR);
 397 }
 398
 399 /*
 400  * Authentication thread.
 401  */
 402 static void *
 403 sshpam_thread(void *ctxtp)
 404 {
 405         struct pam_ctxt *ctxt = ctxtp;
 406         Buffer buffer;
 407         struct pam_conv sshpam_conv;
 408         int flags = (options.permit_empty_passwd == 0 ?
 409             PAM_DISALLOW_NULL_AUTHTOK : 0);
 410 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 411         extern char **environ;
 412         char **env_from_pam;
 413         u_int i;
 414         const char *pam_user;
 415         const char **ptr_pam_user = &pam_user;
 416
 417         pam_get_item(sshpam_handle, PAM_USER,
 418             (sshpam_const void **)ptr_pam_user);
 419         environ[0] = NULL;
 420
 421         if (sshpam_authctxt != NULL) {
 422                 setproctitle("%s [pam]",
 423                     sshpam_authctxt->valid ? pam_user : "unknown");
 424         }
 425 #endif
 426
 427         sshpam_conv.conv = sshpam_thread_conv;
 428         sshpam_conv.appdata_ptr = ctxt;
 429
 430         if (sshpam_authctxt == NULL)
 431                 fatal("%s: PAM authctxt not initialized", __func__);
 432
 433         buffer_init(&buffer);
 434         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 435             (const void *)&sshpam_conv);
 436         if (sshpam_err != PAM_SUCCESS)
 437                 goto auth_fail;
 438         sshpam_err = pam_authenticate(sshpam_handle, flags);
 439         if (sshpam_err != PAM_SUCCESS)
 440                 goto auth_fail;
 441
 442         if (compat20) {
 443                 if (!do_pam_account())
 444                         goto auth_fail;
 445                 if (sshpam_authctxt->force_pwchange) {
 446                         sshpam_err = pam_chauthtok(sshpam_handle,
 447                             PAM_CHANGE_EXPIRED_AUTHTOK);
 448                         if (sshpam_err != PAM_SUCCESS)
 449                                 goto auth_fail;
 450                         sshpam_password_change_required(0);
 451                 }
 452         }
 453
 454         buffer_put_cstring(&buffer, "OK");
 455
 456 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 457         /* Export variables set by do_pam_account */
 458         buffer_put_int(&buffer, sshpam_account_status);
 459         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 460
 461         /* Export any environment strings set in child */
 462         for(i = 0; environ[i] != NULL; i++)
 463                 ; /* Count */
 464         buffer_put_int(&buffer, i);
 465         for(i = 0; environ[i] != NULL; i++)
 466                 buffer_put_cstring(&buffer, environ[i]);
 467
 468         /* Export any environment strings set by PAM in child */
 469         env_from_pam = pam_getenvlist(sshpam_handle);
 470         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 471                 ; /* Count */
 472         buffer_put_int(&buffer, i);
 473         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 474                 buffer_put_cstring(&buffer, env_from_pam[i]);
 475 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 476
 477         /* XXX - can't do much about an error here */
 478         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 479         buffer_free(&buffer);
 480         pthread_exit(NULL);
 481
 482  auth_fail:
 483         buffer_put_cstring(&buffer,
 484             pam_strerror(sshpam_handle, sshpam_err));
 485         /* XXX - can't do much about an error here */
 486         ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 487         buffer_free(&buffer);
 488         pthread_exit(NULL);
 489
 490         return (NULL); /* Avoid warning for non-pthread case */
 491 }
 492
 493 void
 494 sshpam_thread_cleanup(void)
 495 {
 496         struct pam_ctxt *ctxt = cleanup_ctxt;
 497
 498         debug3("PAM: %s entering", __func__);
 499         if (ctxt != NULL && ctxt->pam_thread != 0) {
 500                 pthread_cancel(ctxt->pam_thread);
 501                 pthread_join(ctxt->pam_thread, NULL);
 502                 close(ctxt->pam_psock);
 503                 close(ctxt->pam_csock);
 504                 memset(ctxt, 0, sizeof(*ctxt));
 505                 cleanup_ctxt = NULL;
 506         }
 507 }
 508
 509 static int
 510 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 511     struct pam_response **resp, void *data)
 512 {
 513         debug3("PAM: %s entering, %d messages", __func__, n);
 514         return (PAM_CONV_ERR);
 515 }
 516
 517 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 518
 519 static int
 520 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 521     struct pam_response **resp, void *data)
 522 {
 523         struct pam_response *reply;
 524         int i;
 525         size_t len;
 526
 527         debug3("PAM: %s called with %d messages", __func__, n);
 528         *resp = NULL;
 529
 530         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 531                 return (PAM_CONV_ERR);
 532
 533         if ((reply = malloc(n * sizeof(*reply))) == NULL)
 534                 return (PAM_CONV_ERR);
 535         memset(reply, 0, n * sizeof(*reply));
 536
 537         for (i = 0; i < n; ++i) {
 538                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 539                 case PAM_ERROR_MSG:
 540                 case PAM_TEXT_INFO:
 541                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 542                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 543                         buffer_append(&loginmsg, "\n", 1 );
 544                         reply[i].resp_retcode = PAM_SUCCESS;
 545                         break;
 546                 default:
 547                         goto fail;
 548                 }
 549         }
 550         *resp = reply;
 551         return (PAM_SUCCESS);
 552
 553  fail:
 554         for(i = 0; i < n; i++) {
 555                 if (reply[i].resp != NULL)
 556                         xfree(reply[i].resp);
 557         }
 558         xfree(reply);
 559         return (PAM_CONV_ERR);
 560 }
 561
 562 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 563
 564 void
 565 sshpam_cleanup(void)
 566 {
 567         debug("PAM: cleanup");
 568         if (sshpam_handle == NULL)
 569                 return;
 570         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 571         if (sshpam_cred_established) {
 572                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 573                 sshpam_cred_established = 0;
 574         }
 575         if (sshpam_session_open) {
 576                 pam_close_session(sshpam_handle, PAM_SILENT);
 577                 sshpam_session_open = 0;
 578         }
 579         sshpam_authenticated = 0;
 580         pam_end(sshpam_handle, sshpam_err);
 581         sshpam_handle = NULL;
 582 }
 583
 584 static int
 585 sshpam_init(Authctxt *authctxt)
 586 {
 587         extern char *__progname;
 588         const char *pam_rhost, *pam_user, *user = authctxt->user;
 589         const char **ptr_pam_user = &pam_user;
 590
 591         if (sshpam_handle != NULL) {
 592                 /* We already have a PAM context; check if the user matches */
 593                 sshpam_err = pam_get_item(sshpam_handle,
 594                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 595                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 596                         return (0);
 597                 pam_end(sshpam_handle, sshpam_err);
 598                 sshpam_handle = NULL;
 599         }
 600         debug("PAM: initializing for \"%s\"", user);
 601         sshpam_err =
 602             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 603         sshpam_authctxt = authctxt;
 604
 605         if (sshpam_err != PAM_SUCCESS) {
 606                 pam_end(sshpam_handle, sshpam_err);
 607                 sshpam_handle = NULL;
 608                 return (-1);
 609         }
 610         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 611         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 612         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 613         if (sshpam_err != PAM_SUCCESS) {
 614                 pam_end(sshpam_handle, sshpam_err);
 615                 sshpam_handle = NULL;
 616                 return (-1);
 617         }
 618 #ifdef PAM_TTY_KLUDGE
 619         /*
 620          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 621          * sshd doesn't set the tty until too late in the auth process and
 622          * may not even set one (for tty-less connections)
 623          */
 624         debug("PAM: setting PAM_TTY to \"ssh\"");
 625         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 626         if (sshpam_err != PAM_SUCCESS) {
 627                 pam_end(sshpam_handle, sshpam_err);
 628                 sshpam_handle = NULL;
 629                 return (-1);
 630         }
 631 #endif
 632         return (0);
 633 }
 634
 635 static void *
 636 sshpam_init_ctx(Authctxt *authctxt)
 637 {
 638         struct pam_ctxt *ctxt;
 639         int socks[2];
 640
 641         debug3("PAM: %s entering", __func__);
 642         /* Refuse to start if we don't have PAM enabled */
 643         if (!options.use_pam)
 644                 return NULL;
 645
 646         /* Initialize PAM */
 647         if (sshpam_init(authctxt) == -1) {
 648                 error("PAM: initialization failed");
 649                 return (NULL);
 650         }
 651
 652         ctxt = xmalloc(sizeof *ctxt);
 653         memset(ctxt, 0, sizeof(*ctxt));
 654
 655         /* Start the authentication thread */
 656         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 657                 error("PAM: failed create sockets: %s", strerror(errno));
 658                 xfree(ctxt);
 659                 return (NULL);
 660         }
 661         ctxt->pam_psock = socks[0];
 662         ctxt->pam_csock = socks[1];
 663         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 664                 error("PAM: failed to start authentication thread: %s",
 665                     strerror(errno));
 666                 close(socks[0]);
 667                 close(socks[1]);
 668                 xfree(ctxt);
 669                 return (NULL);
 670         }
 671         cleanup_ctxt = ctxt;
 672         return (ctxt);
 673 }
 674
 675 static int
 676 sshpam_query(void *ctx, char **name, char **info,
 677     u_int *num, char ***prompts, u_int **echo_on)
 678 {
 679         Buffer buffer;
 680         struct pam_ctxt *ctxt = ctx;
 681         size_t plen;
 682         u_char type;
 683         char *msg;
 684         size_t len, mlen;
 685
 686         debug3("PAM: %s entering", __func__);
 687         buffer_init(&buffer);
 688         *name = xstrdup("");
 689         *info = xstrdup("");
 690         *prompts = xmalloc(sizeof(char *));
 691         **prompts = NULL;
 692         plen = 0;
 693         *echo_on = xmalloc(sizeof(u_int));
 694         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 695                 type = buffer_get_char(&buffer);
 696                 msg = buffer_get_string(&buffer, NULL);
 697                 mlen = strlen(msg);
 698                 switch (type) {
 699                 case PAM_PROMPT_ECHO_ON:
 700                 case PAM_PROMPT_ECHO_OFF:
 701                         *num = 1;
 702                         len = plen + mlen + 1;
 703                         **prompts = xrealloc(**prompts, len);
 704                         strlcpy(**prompts + plen, msg, len - plen);
 705                         plen += mlen;
 706                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 707                         xfree(msg);
 708                         return (0);
 709                 case PAM_ERROR_MSG:
 710                 case PAM_TEXT_INFO:
 711                         /* accumulate messages */
 712                         len = plen + mlen + 2;
 713                         **prompts = xrealloc(**prompts, len);
 714                         strlcpy(**prompts + plen, msg, len - plen);
 715                         plen += mlen;
 716                         strlcat(**prompts + plen, "\n", len - plen);
 717                         plen++;
 718                         xfree(msg);
 719                         break;
 720                 case PAM_AUTH_ERR:
 721                         debug3("PAM: PAM_AUTH_ERR");
 722                         if (**prompts != NULL && strlen(**prompts) != 0) {
 723                                 *info = **prompts;
 724                                 **prompts = NULL;
 725                                 *num = 0;
 726                                 **echo_on = 0;
 727                                 ctxt->pam_done = -1;
 728                                 return 0;
 729                         }
 730                         /* FALLTHROUGH */
 731                 case PAM_SUCCESS:
 732                         if (**prompts != NULL) {
 733                                 /* drain any accumulated messages */
 734                                 debug("PAM: %s", **prompts);
 735                                 buffer_append(&loginmsg, **prompts,
 736                                     strlen(**prompts));
 737                                 xfree(**prompts);
 738                                 **prompts = NULL;
 739                         }
 740                         if (type == PAM_SUCCESS) {
 741                                 if (!sshpam_authctxt->valid ||
 742                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 743                                     options.permit_root_login != PERMIT_YES))
 744                                         fatal("Internal error: PAM auth "
 745                                             "succeeded when it should have "
 746                                             "failed");
 747                                 import_environments(&buffer);
 748                                 *num = 0;
 749                                 **echo_on = 0;
 750                                 ctxt->pam_done = 1;
 751                                 xfree(msg);
 752                                 return (0);
 753                         }
 754                         error("PAM: %s for %s%.100s from %.100s", msg,
 755                             sshpam_authctxt->valid ? "" : "illegal user ",
 756                             sshpam_authctxt->user,
 757                             get_remote_name_or_ip(utmp_len, options.use_dns));
 758                         /* FALLTHROUGH */
 759                 default:
 760                         *num = 0;
 761                         **echo_on = 0;
 762                         xfree(msg);
 763                         ctxt->pam_done = -1;
 764                         return (-1);
 765                 }
 766         }
 767         return (-1);
 768 }
 769
 770 /* XXX - see also comment in auth-chall.c:verify_response */
 771 static int
 772 sshpam_respond(void *ctx, u_int num, char **resp)
 773 {
 774         Buffer buffer;
 775         struct pam_ctxt *ctxt = ctx;
 776
 777         debug2("PAM: %s entering, %u responses", __func__, num);
 778         switch (ctxt->pam_done) {
 779         case 1:
 780                 sshpam_authenticated = 1;
 781                 return (0);
 782         case 0:
 783                 break;
 784         default:
 785                 return (-1);
 786         }
 787         if (num != 1) {
 788                 error("PAM: expected one response, got %u", num);
 789                 return (-1);
 790         }
 791         buffer_init(&buffer);
 792         if (sshpam_authctxt->valid &&
 793             (sshpam_authctxt->pw->pw_uid != 0 ||
 794             options.permit_root_login == PERMIT_YES))
 795                 buffer_put_cstring(&buffer, *resp);
 796         else
 797                 buffer_put_cstring(&buffer, badpw);
 798         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 799                 buffer_free(&buffer);
 800                 return (-1);
 801         }
 802         buffer_free(&buffer);
 803         return (1);
 804 }
 805
 806 static void
 807 sshpam_free_ctx(void *ctxtp)
 808 {
 809         struct pam_ctxt *ctxt = ctxtp;
 810
 811         debug3("PAM: %s entering", __func__);
 812         sshpam_thread_cleanup();
 813         xfree(ctxt);
 814         /*
 815          * We don't call sshpam_cleanup() here because we may need the PAM
 816          * handle at a later stage, e.g. when setting up a session.  It's
 817          * still on the cleanup list, so pam_end() *will* be called before
 818          * the server process terminates.
 819          */
 820 }
 821
 822 KbdintDevice sshpam_device = {
 823         "pam",
 824         sshpam_init_ctx,
 825         sshpam_query,
 826         sshpam_respond,
 827         sshpam_free_ctx
 828 };
 829
 830 KbdintDevice mm_sshpam_device = {
 831         "pam",
 832         mm_sshpam_init_ctx,
 833         mm_sshpam_query,
 834         mm_sshpam_respond,
 835         mm_sshpam_free_ctx
 836 };
 837
 838 /*
 839  * This replaces auth-pam.c
 840  */
 841 void
 842 start_pam(Authctxt *authctxt)
 843 {
 844         if (!options.use_pam)
 845                 fatal("PAM: initialisation requested when UsePAM=no");
 846
 847         if (sshpam_init(authctxt) == -1)
 848                 fatal("PAM: initialisation failed");
 849 }
 850
 851 void
 852 finish_pam(void)
 853 {
 854         sshpam_cleanup();
 855 }
 856
 857 u_int
 858 do_pam_account(void)
 859 {
 860         debug("%s: called", __func__);
 861         if (sshpam_account_status != -1)
 862                 return (sshpam_account_status);
 863
 864         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 865         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 866             pam_strerror(sshpam_handle, sshpam_err));
 867
 868         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 869                 sshpam_account_status = 0;
 870                 return (sshpam_account_status);
 871         }
 872
 873         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 874                 sshpam_password_change_required(1);
 875
 876         sshpam_account_status = 1;
 877         return (sshpam_account_status);
 878 }
 879
 880 void
 881 do_pam_set_tty(const char *tty)
 882 {
 883         if (tty != NULL) {
 884                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 885                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 886                 if (sshpam_err != PAM_SUCCESS)
 887                         fatal("PAM: failed to set PAM_TTY: %s",
 888                             pam_strerror(sshpam_handle, sshpam_err));
 889         }
 890 }
 891
 892 void
 893 do_pam_setcred(int init)
 894 {
 895         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 896             (const void *)&store_conv);
 897         if (sshpam_err != PAM_SUCCESS)
 898                 fatal("PAM: failed to set PAM_CONV: %s",
 899                     pam_strerror(sshpam_handle, sshpam_err));
 900         if (init) {
 901                 debug("PAM: establishing credentials");
 902                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 903         } else {
 904                 debug("PAM: reinitializing credentials");
 905                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 906         }
 907         if (sshpam_err == PAM_SUCCESS) {
 908                 sshpam_cred_established = 1;
 909                 return;
 910         }
 911         if (sshpam_authenticated)
 912                 fatal("PAM: pam_setcred(): %s",
 913                     pam_strerror(sshpam_handle, sshpam_err));
 914         else
 915                 debug("PAM: pam_setcred(): %s",
 916                     pam_strerror(sshpam_handle, sshpam_err));
 917 }
 918
 919 static int
 920 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 921     struct pam_response **resp, void *data)
 922 {
 923         char input[PAM_MAX_MSG_SIZE];
 924         struct pam_response *reply;
 925         int i;
 926
 927         debug3("PAM: %s called with %d messages", __func__, n);
 928
 929         *resp = NULL;
 930
 931         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 932                 return (PAM_CONV_ERR);
 933
 934         if ((reply = malloc(n * sizeof(*reply))) == NULL)
 935                 return (PAM_CONV_ERR);
 936         memset(reply, 0, n * sizeof(*reply));
 937
 938         for (i = 0; i < n; ++i) {
 939                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 940                 case PAM_PROMPT_ECHO_OFF:
 941                         reply[i].resp =
 942                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 943                             RP_ALLOW_STDIN);
 944                         reply[i].resp_retcode = PAM_SUCCESS;
 945                         break;
 946                 case PAM_PROMPT_ECHO_ON:
 947                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 948                         fgets(input, sizeof input, stdin);
 949                         if ((reply[i].resp = strdup(input)) == NULL)
 950                                 goto fail;
 951                         reply[i].resp_retcode = PAM_SUCCESS;
 952                         break;
 953                 case PAM_ERROR_MSG:
 954                 case PAM_TEXT_INFO:
 955                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 956                         reply[i].resp_retcode = PAM_SUCCESS;
 957                         break;
 958                 default:
 959                         goto fail;
 960                 }
 961         }
 962         *resp = reply;
 963         return (PAM_SUCCESS);
 964
 965  fail:
 966         for(i = 0; i < n; i++) {
 967                 if (reply[i].resp != NULL)
 968                         xfree(reply[i].resp);
 969         }
 970         xfree(reply);
 971         return (PAM_CONV_ERR);
 972 }
 973
 974 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
 975
 976 /*
 977  * XXX this should be done in the authentication phase, but ssh1 doesn't
 978  * support that
 979  */
 980 void
 981 do_pam_chauthtok(void)
 982 {
 983         if (use_privsep)
 984                 fatal("Password expired (unable to change with privsep)");
 985         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 986             (const void *)&tty_conv);
 987         if (sshpam_err != PAM_SUCCESS)
 988                 fatal("PAM: failed to set PAM_CONV: %s",
 989                     pam_strerror(sshpam_handle, sshpam_err));
 990         debug("PAM: changing password");
 991         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
 992         if (sshpam_err != PAM_SUCCESS)
 993                 fatal("PAM: pam_chauthtok(): %s",
 994                     pam_strerror(sshpam_handle, sshpam_err));
 995 }
 996
 997 void
 998 do_pam_session(void)
 999 {
1000         debug3("PAM: opening session");
1001         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1002             (const void *)&store_conv);
1003         if (sshpam_err != PAM_SUCCESS)
1004                 fatal("PAM: failed to set PAM_CONV: %s",
1005                     pam_strerror(sshpam_handle, sshpam_err));
1006         sshpam_err = pam_open_session(sshpam_handle, 0);
1007         if (sshpam_err == PAM_SUCCESS)
1008                 sshpam_session_open = 1;
1009         else {
1010                 sshpam_session_open = 0;
1011                 disable_forwarding();
1012                 error("PAM: pam_open_session(): %s",
1013                     pam_strerror(sshpam_handle, sshpam_err));
1014         }
1015
1016 }
1017
1018 int
1019 is_pam_session_open(void)
1020 {
1021         return sshpam_session_open;
1022 }
1023
1024 /*
1025  * Set a PAM environment string. We need to do this so that the session
1026  * modules can handle things like Kerberos/GSI credentials that appear
1027  * during the ssh authentication process.
1028  */
1029 int
1030 do_pam_putenv(char *name, char *value)
1031 {
1032         int ret = 1;
1033 #ifdef HAVE_PAM_PUTENV
1034         char *compound;
1035         size_t len;
1036
1037         len = strlen(name) + strlen(value) + 2;
1038         compound = xmalloc(len);
1039
1040         snprintf(compound, len, "%s=%s", name, value);
1041         ret = pam_putenv(sshpam_handle, compound);
1042         xfree(compound);
1043 #endif
1044
1045         return (ret);
1046 }
1047
1048 char **
1049 fetch_pam_child_environment(void)
1050 {
1051         return sshpam_env;
1052 }
1053
1054 char **
1055 fetch_pam_environment(void)
1056 {
1057         return (pam_getenvlist(sshpam_handle));
1058 }
1059
1060 void
1061 free_pam_environment(char **env)
1062 {
1063         char **envp;
1064
1065         if (env == NULL)
1066                 return;
1067
1068         for (envp = env; *envp; envp++)
1069                 xfree(*envp);
1070         xfree(env);
1071 }
1072
1073 /*
1074  * "Blind" conversation function for password authentication.  Assumes that
1075  * echo-off prompts are for the password and stores messages for later
1076  * display.
1077  */
1078 static int
1079 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1080     struct pam_response **resp, void *data)
1081 {
1082         struct pam_response *reply;
1083         int i;
1084         size_t len;
1085
1086         debug3("PAM: %s called with %d messages", __func__, n);
1087
1088         *resp = NULL;
1089
1090         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1091                 return (PAM_CONV_ERR);
1092
1093         if ((reply = malloc(n * sizeof(*reply))) == NULL)
1094                 return (PAM_CONV_ERR);
1095         memset(reply, 0, n * sizeof(*reply));
1096
1097         for (i = 0; i < n; ++i) {
1098                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1099                 case PAM_PROMPT_ECHO_OFF:
1100                         if (sshpam_password == NULL)
1101                                 goto fail;
1102                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1103                                 goto fail;
1104                         reply[i].resp_retcode = PAM_SUCCESS;
1105                         break;
1106                 case PAM_ERROR_MSG:
1107                 case PAM_TEXT_INFO:
1108                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1109                         if (len > 0) {
1110                                 buffer_append(&loginmsg,
1111                                     PAM_MSG_MEMBER(msg, i, msg), len);
1112                                 buffer_append(&loginmsg, "\n", 1);
1113                         }
1114                         if ((reply[i].resp = strdup("")) == NULL)
1115                                 goto fail;
1116                         reply[i].resp_retcode = PAM_SUCCESS;
1117                         break;
1118                 default:
1119                         goto fail;
1120                 }
1121         }
1122         *resp = reply;
1123         return (PAM_SUCCESS);
1124
1125  fail:
1126         for(i = 0; i < n; i++) {
1127                 if (reply[i].resp != NULL)
1128                         xfree(reply[i].resp);
1129         }
1130         xfree(reply);
1131         return (PAM_CONV_ERR);
1132 }
1133
1134 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1135
1136 /*
1137  * Attempt password authentication via PAM
1138  */
1139 int
1140 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1141 {
1142         int flags = (options.permit_empty_passwd == 0 ?
1143             PAM_DISALLOW_NULL_AUTHTOK : 0);
1144
1145         if (!options.use_pam || sshpam_handle == NULL)
1146                 fatal("PAM: %s called when PAM disabled or failed to "
1147                     "initialise.", __func__);
1148
1149         sshpam_password = password;
1150         sshpam_authctxt = authctxt;
1151
1152         /*
1153          * If the user logging in is invalid, or is root but is not permitted
1154          * by PermitRootLogin, use an invalid password to prevent leaking
1155          * information via timing (eg if the PAM config has a delay on fail).
1156          */
1157         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1158             options.permit_root_login != PERMIT_YES))
1159                 sshpam_password = badpw;
1160
1161         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1162             (const void *)&passwd_conv);
1163         if (sshpam_err != PAM_SUCCESS)
1164                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1165                     pam_strerror(sshpam_handle, sshpam_err));
1166
1167         sshpam_err = pam_authenticate(sshpam_handle, flags);
1168         sshpam_password = NULL;
1169         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1170                 debug("PAM: password authentication accepted for %.100s",
1171                     authctxt->user);
1172                 return 1;
1173         } else {
1174                 debug("PAM: password authentication failed for %.100s: %s",
1175                     authctxt->valid ? authctxt->user : "an illegal user",
1176                     pam_strerror(sshpam_handle, sshpam_err));
1177                 return 0;
1178         }
1179 }
1180 #endif /* USE_PAM */