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 <stdarg.h>
  58 #include <string.h>
  59 #include <unistd.h>
  60
  61 #ifdef USE_PAM
  62 #if defined(HAVE_SECURITY_PAM_APPL_H)
  63 #include <security/pam_appl.h>
  64 #elif defined (HAVE_PAM_PAM_APPL_H)
  65 #include <pam/pam_appl.h>
  66 #endif
  67
  68 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
  69 #ifdef PAM_SUN_CODEBASE
  70 # define sshpam_const           /* Solaris, HP-UX, AIX */
  71 #else
  72 # define sshpam_const   const   /* LinuxPAM, OpenPAM */
  73 #endif
  74
  75 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
  76 #ifdef PAM_SUN_CODEBASE
  77 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
  78 #else
  79 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
  80 #endif
  81
  82 #include "xmalloc.h"
  83 #include "buffer.h"
  84 #include "key.h"
  85 #include "hostfile.h"
  86 #include "auth.h"
  87 #include "auth-pam.h"
  88 #include "canohost.h"
  89 #include "log.h"
  90 #include "msg.h"
  91 #include "packet.h"
  92 #include "misc.h"
  93 #include "servconf.h"
  94 #include "ssh2.h"
  95 #include "auth-options.h"
  96 #ifdef GSSAPI
  97 #include "ssh-gss.h"
  98 #endif
  99 #include "monitor_wrap.h"
 100
 101 extern ServerOptions options;
 102 extern Buffer loginmsg;
 103 extern int compat20;
 104 extern u_int utmp_len;
 105
 106 /* so we don't silently change behaviour */
 107 #ifdef USE_POSIX_THREADS
 108 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
 109 #endif
 110
 111 /*
 112  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
 113  * and generally a bad idea.  Use at own risk and do not expect support if
 114  * this breaks.
 115  */
 116 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
 117 #include <pthread.h>
 118 /*
 119  * Avoid namespace clash when *not* using pthreads for systems *with*
 120  * pthreads, which unconditionally define pthread_t via sys/types.h
 121  * (e.g. Linux)
 122  */
 123 typedef pthread_t sp_pthread_t;
 124 #else
 125 typedef pid_t sp_pthread_t;
 126 #endif
 127
 128 struct pam_ctxt {
 129         sp_pthread_t     pam_thread;
 130         int              pam_psock;
 131         int              pam_csock;
 132         int              pam_done;
 133 };
 134
 135 static void sshpam_free_ctx(void *);
 136 static struct pam_ctxt *cleanup_ctxt;
 137
 138 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 139 /*
 140  * Simulate threads with processes.
 141  */
 142
 143 static int sshpam_thread_status = -1;
 144 static mysig_t sshpam_oldsig;
 145
 146 static void
 147 sshpam_sigchld_handler(int sig)
 148 {
 149         signal(SIGCHLD, SIG_DFL);
 150         if (cleanup_ctxt == NULL)
 151                 return; /* handler called after PAM cleanup, shouldn't happen */
 152         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 153             <= 0) {
 154                 /* PAM thread has not exitted, privsep slave must have */
 155                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 156                 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
 157                     <= 0)
 158                         return; /* could not wait */
 159         }
 160         if (WIFSIGNALED(sshpam_thread_status) &&
 161             WTERMSIG(sshpam_thread_status) == SIGTERM)
 162                 return; /* terminated by pthread_cancel */
 163         if (!WIFEXITED(sshpam_thread_status))
 164                 fatal("PAM: authentication thread exited unexpectedly");
 165         if (WEXITSTATUS(sshpam_thread_status) != 0)
 166                 fatal("PAM: authentication thread exited uncleanly");
 167 }
 168
 169 /* ARGSUSED */
 170 static void
 171 pthread_exit(void *value)
 172 {
 173         _exit(0);
 174 }
 175
 176 /* ARGSUSED */
 177 static int
 178 pthread_create(sp_pthread_t *thread, const void *attr,
 179     void *(*thread_start)(void *), void *arg)
 180 {
 181         pid_t pid;
 182         struct pam_ctxt *ctx = arg;
 183
 184         sshpam_thread_status = -1;
 185         switch ((pid = fork())) {
 186         case -1:
 187                 error("fork(): %s", strerror(errno));
 188                 return (-1);
 189         case 0:
 190                 close(ctx->pam_psock);
 191                 ctx->pam_psock = -1;
 192                 thread_start(arg);
 193                 _exit(1);
 194         default:
 195                 *thread = pid;
 196                 close(ctx->pam_csock);
 197                 ctx->pam_csock = -1;
 198                 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
 199                 return (0);
 200         }
 201 }
 202
 203 static int
 204 pthread_cancel(sp_pthread_t thread)
 205 {
 206         signal(SIGCHLD, sshpam_oldsig);
 207         return (kill(thread, SIGTERM));
 208 }
 209
 210 /* ARGSUSED */
 211 static int
 212 pthread_join(sp_pthread_t thread, void **value)
 213 {
 214         int status;
 215
 216         if (sshpam_thread_status != -1)
 217                 return (sshpam_thread_status);
 218         signal(SIGCHLD, sshpam_oldsig);
 219         waitpid(thread, &status, 0);
 220         return (status);
 221 }
 222 #endif
 223
 224
 225 static pam_handle_t *sshpam_handle = NULL;
 226 static int sshpam_err = 0;
 227 static int sshpam_authenticated = 0;
 228 static int sshpam_session_open = 0;
 229 static int sshpam_cred_established = 0;
 230 static int sshpam_account_status = -1;
 231 static char **sshpam_env = NULL;
 232 static Authctxt *sshpam_authctxt = NULL;
 233 static const char *sshpam_password = NULL;
 234 static char badpw[] = "\b\n\r\177INCORRECT";
 235
 236 /* Some PAM implementations don't implement this */
 237 #ifndef HAVE_PAM_GETENVLIST
 238 static char **
 239 pam_getenvlist(pam_handle_t *pamh)
 240 {
 241         /*
 242          * XXX - If necessary, we can still support envrionment passing
 243          * for platforms without pam_getenvlist by searching for known
 244          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 245          */
 246          return NULL;
 247 }
 248 #endif
 249
 250 /*
 251  * Some platforms, notably Solaris, do not enforce password complexity
 252  * rules during pam_chauthtok() if the real uid of the calling process
 253  * is 0, on the assumption that it's being called by "passwd" run by root.
 254  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 255  * the right thing.
 256  */
 257 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 258 static int
 259 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 260 {
 261         int result;
 262
 263         if (sshpam_authctxt == NULL)
 264                 fatal("PAM: sshpam_authctxt not initialized");
 265         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 266                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 267         result = pam_chauthtok(pamh, flags);
 268         if (setreuid(0, -1) == -1)
 269                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 270         return result;
 271 }
 272 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 273 #endif
 274
 275 void
 276 sshpam_password_change_required(int reqd)
 277 {
 278         debug3("%s %d", __func__, reqd);
 279         if (sshpam_authctxt == NULL)
 280                 fatal("%s: PAM authctxt not initialized", __func__);
 281         sshpam_authctxt->force_pwchange = reqd;
 282         if (reqd) {
 283                 no_port_forwarding_flag |= 2;
 284                 no_agent_forwarding_flag |= 2;
 285                 no_x11_forwarding_flag |= 2;
 286         } else {
 287                 no_port_forwarding_flag &= ~2;
 288                 no_agent_forwarding_flag &= ~2;
 289                 no_x11_forwarding_flag &= ~2;
 290         }
 291 }
 292
 293 /* Import regular and PAM environment from subprocess */
 294 static void
 295 import_environments(Buffer *b)
 296 {
 297         char *env;
 298         u_int i, num_env;
 299         int err;
 300
 301         debug3("PAM: %s entering", __func__);
 302
 303 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 304         /* Import variables set by do_pam_account */
 305         sshpam_account_status = buffer_get_int(b);
 306         sshpam_password_change_required(buffer_get_int(b));
 307
 308         /* Import environment from subprocess */
 309         num_env = buffer_get_int(b);
 310         if (num_env > 1024)
 311                 fatal("%s: received %u environment variables, expected <= 1024",
 312                     __func__, num_env);
 313         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 314         debug3("PAM: num env strings %d", num_env);
 315         for(i = 0; i < num_env; i++)
 316                 sshpam_env[i] = buffer_get_string(b, NULL);
 317
 318         sshpam_env[num_env] = NULL;
 319
 320         /* Import PAM environment from subprocess */
 321         num_env = buffer_get_int(b);
 322         debug("PAM: num PAM env strings %d", num_env);
 323         for(i = 0; i < num_env; i++) {
 324                 env = buffer_get_string(b, NULL);
 325
 326 #ifdef HAVE_PAM_PUTENV
 327                 /* Errors are not fatal here */
 328                 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 329                         error("PAM: pam_putenv: %s",
 330                             pam_strerror(sshpam_handle, sshpam_err));
 331                 }
 332 #endif
 333         }
 334 #endif
 335 }
 336
 337 /*
 338  * Conversation function for authentication thread.
 339  */
 340 static int
 341 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 342     struct pam_response **resp, void *data)
 343 {
 344         Buffer buffer;
 345         struct pam_ctxt *ctxt;
 346         struct pam_response *reply;
 347         int i;
 348
 349         debug3("PAM: %s entering, %d messages", __func__, n);
 350         *resp = NULL;
 351
 352         if (data == NULL) {
 353                 error("PAM: conversation function passed a null context");
 354                 return (PAM_CONV_ERR);
 355         }
 356         ctxt = data;
 357         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 358                 return (PAM_CONV_ERR);
 359
 360         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 361                 return (PAM_CONV_ERR);
 362
 363         buffer_init(&buffer);
 364         for (i = 0; i < n; ++i) {
 365                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 366                 case PAM_PROMPT_ECHO_OFF:
 367                         buffer_put_cstring(&buffer,
 368                             PAM_MSG_MEMBER(msg, i, msg));
 369                         if (ssh_msg_send(ctxt->pam_csock,
 370                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 371                                 goto fail;
 372                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 373                                 goto fail;
 374                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 375                                 goto fail;
 376                         reply[i].resp = buffer_get_string(&buffer, NULL);
 377                         break;
 378                 case PAM_PROMPT_ECHO_ON:
 379                         buffer_put_cstring(&buffer,
 380                             PAM_MSG_MEMBER(msg, i, msg));
 381                         if (ssh_msg_send(ctxt->pam_csock,
 382                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 383                                 goto fail;
 384                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 385                                 goto fail;
 386                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 387                                 goto fail;
 388                         reply[i].resp = buffer_get_string(&buffer, NULL);
 389                         break;
 390                 case PAM_ERROR_MSG:
 391                         buffer_put_cstring(&buffer,
 392                             PAM_MSG_MEMBER(msg, i, msg));
 393                         if (ssh_msg_send(ctxt->pam_csock,
 394                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 395                                 goto fail;
 396                         break;
 397                 case PAM_TEXT_INFO:
 398                         buffer_put_cstring(&buffer,
 399                             PAM_MSG_MEMBER(msg, i, msg));
 400                         if (ssh_msg_send(ctxt->pam_csock,
 401                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 402                                 goto fail;
 403                         break;
 404                 default:
 405                         goto fail;
 406                 }
 407                 buffer_clear(&buffer);
 408         }
 409         buffer_free(&buffer);
 410         *resp = reply;
 411         return (PAM_SUCCESS);
 412
 413  fail:
 414         for(i = 0; i < n; i++) {
 415                 if (reply[i].resp != NULL)
 416                         xfree(reply[i].resp);
 417         }
 418         xfree(reply);
 419         buffer_free(&buffer);
 420         return (PAM_CONV_ERR);
 421 }
 422
 423 /*
 424  * Authentication thread.
 425  */
 426 static void *
 427 sshpam_thread(void *ctxtp)
 428 {
 429         struct pam_ctxt *ctxt = ctxtp;
 430         Buffer buffer;
 431         struct pam_conv sshpam_conv;
 432         int flags = (options.permit_empty_passwd == 0 ?
 433             PAM_DISALLOW_NULL_AUTHTOK : 0);
 434 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 435         extern char **environ;
 436         char **env_from_pam;
 437         u_int i;
 438         const char *pam_user;
 439         const char **ptr_pam_user = &pam_user;
 440
 441         pam_get_item(sshpam_handle, PAM_USER,
 442             (sshpam_const void **)ptr_pam_user);
 443         environ[0] = NULL;
 444
 445         if (sshpam_authctxt != NULL) {
 446                 setproctitle("%s [pam]",
 447                     sshpam_authctxt->valid ? pam_user : "unknown");
 448         }
 449 #endif
 450
 451         sshpam_conv.conv = sshpam_thread_conv;
 452         sshpam_conv.appdata_ptr = ctxt;
 453
 454         if (sshpam_authctxt == NULL)
 455                 fatal("%s: PAM authctxt not initialized", __func__);
 456
 457         buffer_init(&buffer);
 458         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 459             (const void *)&sshpam_conv);
 460         if (sshpam_err != PAM_SUCCESS)
 461                 goto auth_fail;
 462         sshpam_err = pam_authenticate(sshpam_handle, flags);
 463         if (sshpam_err != PAM_SUCCESS)
 464                 goto auth_fail;
 465
 466         if (compat20) {
 467                 if (!do_pam_account()) {
 468                         sshpam_err = PAM_ACCT_EXPIRED;
 469                         goto auth_fail;
 470                 }
 471                 if (sshpam_authctxt->force_pwchange) {
 472                         sshpam_err = pam_chauthtok(sshpam_handle,
 473                             PAM_CHANGE_EXPIRED_AUTHTOK);
 474                         if (sshpam_err != PAM_SUCCESS)
 475                                 goto auth_fail;
 476                         sshpam_password_change_required(0);
 477                 }
 478         }
 479
 480         buffer_put_cstring(&buffer, "OK");
 481
 482 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 483         /* Export variables set by do_pam_account */
 484         buffer_put_int(&buffer, sshpam_account_status);
 485         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 486
 487         /* Export any environment strings set in child */
 488         for(i = 0; environ[i] != NULL; i++)
 489                 ; /* Count */
 490         buffer_put_int(&buffer, i);
 491         for(i = 0; environ[i] != NULL; i++)
 492                 buffer_put_cstring(&buffer, environ[i]);
 493
 494         /* Export any environment strings set by PAM in child */
 495         env_from_pam = pam_getenvlist(sshpam_handle);
 496         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 497                 ; /* Count */
 498         buffer_put_int(&buffer, i);
 499         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 500                 buffer_put_cstring(&buffer, env_from_pam[i]);
 501 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 502
 503         /* XXX - can't do much about an error here */
 504         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 505         buffer_free(&buffer);
 506         pthread_exit(NULL);
 507
 508  auth_fail:
 509         buffer_put_cstring(&buffer,
 510             pam_strerror(sshpam_handle, sshpam_err));
 511         /* XXX - can't do much about an error here */
 512         if (sshpam_err == PAM_ACCT_EXPIRED)
 513                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);
 514         else
 515                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 516         buffer_free(&buffer);
 517         pthread_exit(NULL);
 518
 519         return (NULL); /* Avoid warning for non-pthread case */
 520 }
 521
 522 void
 523 sshpam_thread_cleanup(void)
 524 {
 525         struct pam_ctxt *ctxt = cleanup_ctxt;
 526
 527         debug3("PAM: %s entering", __func__);
 528         if (ctxt != NULL && ctxt->pam_thread != 0) {
 529                 pthread_cancel(ctxt->pam_thread);
 530                 pthread_join(ctxt->pam_thread, NULL);
 531                 close(ctxt->pam_psock);
 532                 close(ctxt->pam_csock);
 533                 memset(ctxt, 0, sizeof(*ctxt));
 534                 cleanup_ctxt = NULL;
 535         }
 536 }
 537
 538 static int
 539 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 540     struct pam_response **resp, void *data)
 541 {
 542         debug3("PAM: %s entering, %d messages", __func__, n);
 543         return (PAM_CONV_ERR);
 544 }
 545
 546 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 547
 548 static int
 549 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 550     struct pam_response **resp, void *data)
 551 {
 552         struct pam_response *reply;
 553         int i;
 554         size_t len;
 555
 556         debug3("PAM: %s called with %d messages", __func__, n);
 557         *resp = NULL;
 558
 559         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 560                 return (PAM_CONV_ERR);
 561
 562         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 563                 return (PAM_CONV_ERR);
 564
 565         for (i = 0; i < n; ++i) {
 566                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 567                 case PAM_ERROR_MSG:
 568                 case PAM_TEXT_INFO:
 569                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 570                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 571                         buffer_append(&loginmsg, "\n", 1 );
 572                         reply[i].resp_retcode = PAM_SUCCESS;
 573                         break;
 574                 default:
 575                         goto fail;
 576                 }
 577         }
 578         *resp = reply;
 579         return (PAM_SUCCESS);
 580
 581  fail:
 582         for(i = 0; i < n; i++) {
 583                 if (reply[i].resp != NULL)
 584                         xfree(reply[i].resp);
 585         }
 586         xfree(reply);
 587         return (PAM_CONV_ERR);
 588 }
 589
 590 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 591
 592 void
 593 sshpam_cleanup(void)
 594 {
 595         debug("PAM: cleanup");
 596         if (sshpam_handle == NULL)
 597                 return;
 598         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 599         if (sshpam_cred_established) {
 600                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 601                 sshpam_cred_established = 0;
 602         }
 603         if (sshpam_session_open) {
 604                 pam_close_session(sshpam_handle, PAM_SILENT);
 605                 sshpam_session_open = 0;
 606         }
 607         sshpam_authenticated = 0;
 608         pam_end(sshpam_handle, sshpam_err);
 609         sshpam_handle = NULL;
 610 }
 611
 612 static int
 613 sshpam_init(Authctxt *authctxt)
 614 {
 615         extern char *__progname;
 616         const char *pam_rhost, *pam_user, *user = authctxt->user;
 617         const char **ptr_pam_user = &pam_user;
 618
 619         if (sshpam_handle != NULL) {
 620                 /* We already have a PAM context; check if the user matches */
 621                 sshpam_err = pam_get_item(sshpam_handle,
 622                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 623                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 624                         return (0);
 625                 pam_end(sshpam_handle, sshpam_err);
 626                 sshpam_handle = NULL;
 627         }
 628         debug("PAM: initializing for \"%s\"", user);
 629         sshpam_err =
 630             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 631         sshpam_authctxt = authctxt;
 632
 633         if (sshpam_err != PAM_SUCCESS) {
 634                 pam_end(sshpam_handle, sshpam_err);
 635                 sshpam_handle = NULL;
 636                 return (-1);
 637         }
 638         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 639         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 640         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 641         if (sshpam_err != PAM_SUCCESS) {
 642                 pam_end(sshpam_handle, sshpam_err);
 643                 sshpam_handle = NULL;
 644                 return (-1);
 645         }
 646 #ifdef PAM_TTY_KLUDGE
 647         /*
 648          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 649          * sshd doesn't set the tty until too late in the auth process and
 650          * may not even set one (for tty-less connections)
 651          */
 652         debug("PAM: setting PAM_TTY to \"ssh\"");
 653         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 654         if (sshpam_err != PAM_SUCCESS) {
 655                 pam_end(sshpam_handle, sshpam_err);
 656                 sshpam_handle = NULL;
 657                 return (-1);
 658         }
 659 #endif
 660         return (0);
 661 }
 662
 663 static void *
 664 sshpam_init_ctx(Authctxt *authctxt)
 665 {
 666         struct pam_ctxt *ctxt;
 667         int socks[2];
 668
 669         debug3("PAM: %s entering", __func__);
 670         /*
 671          * Refuse to start if we don't have PAM enabled or do_pam_account
 672          * has previously failed.
 673          */
 674         if (!options.use_pam || sshpam_account_status == 0)
 675                 return NULL;
 676
 677         /* Initialize PAM */
 678         if (sshpam_init(authctxt) == -1) {
 679                 error("PAM: initialization failed");
 680                 return (NULL);
 681         }
 682
 683         ctxt = xmalloc(sizeof *ctxt);
 684         memset(ctxt, 0, sizeof(*ctxt));
 685
 686         /* Start the authentication thread */
 687         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 688                 error("PAM: failed create sockets: %s", strerror(errno));
 689                 xfree(ctxt);
 690                 return (NULL);
 691         }
 692         ctxt->pam_psock = socks[0];
 693         ctxt->pam_csock = socks[1];
 694         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 695                 error("PAM: failed to start authentication thread: %s",
 696                     strerror(errno));
 697                 close(socks[0]);
 698                 close(socks[1]);
 699                 xfree(ctxt);
 700                 return (NULL);
 701         }
 702         cleanup_ctxt = ctxt;
 703         return (ctxt);
 704 }
 705
 706 static int
 707 sshpam_query(void *ctx, char **name, char **info,
 708     u_int *num, char ***prompts, u_int **echo_on)
 709 {
 710         Buffer buffer;
 711         struct pam_ctxt *ctxt = ctx;
 712         size_t plen;
 713         u_char type;
 714         char *msg;
 715         size_t len, mlen;
 716
 717         debug3("PAM: %s entering", __func__);
 718         buffer_init(&buffer);
 719         *name = xstrdup("");
 720         *info = xstrdup("");
 721         *prompts = xmalloc(sizeof(char *));
 722         **prompts = NULL;
 723         plen = 0;
 724         *echo_on = xmalloc(sizeof(u_int));
 725         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 726                 type = buffer_get_char(&buffer);
 727                 msg = buffer_get_string(&buffer, NULL);
 728                 mlen = strlen(msg);
 729                 switch (type) {
 730                 case PAM_PROMPT_ECHO_ON:
 731                 case PAM_PROMPT_ECHO_OFF:
 732                         *num = 1;
 733                         len = plen + mlen + 1;
 734                         **prompts = xrealloc(**prompts, 1, len);
 735                         strlcpy(**prompts + plen, msg, len - plen);
 736                         plen += mlen;
 737                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 738                         xfree(msg);
 739                         return (0);
 740                 case PAM_ERROR_MSG:
 741                 case PAM_TEXT_INFO:
 742                         /* accumulate messages */
 743                         len = plen + mlen + 2;
 744                         **prompts = xrealloc(**prompts, 1, len);
 745                         strlcpy(**prompts + plen, msg, len - plen);
 746                         plen += mlen;
 747                         strlcat(**prompts + plen, "\n", len - plen);
 748                         plen++;
 749                         xfree(msg);
 750                         break;
 751                 case PAM_ACCT_EXPIRED:
 752                         sshpam_account_status = 0;
 753                         /* FALLTHROUGH */
 754                 case PAM_AUTH_ERR:
 755                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 756                         if (**prompts != NULL && strlen(**prompts) != 0) {
 757                                 *info = **prompts;
 758                                 **prompts = NULL;
 759                                 *num = 0;
 760                                 **echo_on = 0;
 761                                 ctxt->pam_done = -1;
 762                                 xfree(msg);
 763                                 return 0;
 764                         }
 765                         /* FALLTHROUGH */
 766                 case PAM_SUCCESS:
 767                         if (**prompts != NULL) {
 768                                 /* drain any accumulated messages */
 769                                 debug("PAM: %s", **prompts);
 770                                 buffer_append(&loginmsg, **prompts,
 771                                     strlen(**prompts));
 772                                 xfree(**prompts);
 773                                 **prompts = NULL;
 774                         }
 775                         if (type == PAM_SUCCESS) {
 776                                 if (!sshpam_authctxt->valid ||
 777                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 778                                     options.permit_root_login != PERMIT_YES))
 779                                         fatal("Internal error: PAM auth "
 780                                             "succeeded when it should have "
 781                                             "failed");
 782                                 import_environments(&buffer);
 783                                 *num = 0;
 784                                 **echo_on = 0;
 785                                 ctxt->pam_done = 1;
 786                                 xfree(msg);
 787                                 return (0);
 788                         }
 789                         error("PAM: %s for %s%.100s from %.100s", msg,
 790                             sshpam_authctxt->valid ? "" : "illegal user ",
 791                             sshpam_authctxt->user,
 792                             get_remote_name_or_ip(utmp_len, options.use_dns));
 793                         /* FALLTHROUGH */
 794                 default:
 795                         *num = 0;
 796                         **echo_on = 0;
 797                         xfree(msg);
 798                         ctxt->pam_done = -1;
 799                         return (-1);
 800                 }
 801         }
 802         return (-1);
 803 }
 804
 805 /* XXX - see also comment in auth-chall.c:verify_response */
 806 static int
 807 sshpam_respond(void *ctx, u_int num, char **resp)
 808 {
 809         Buffer buffer;
 810         struct pam_ctxt *ctxt = ctx;
 811
 812         debug2("PAM: %s entering, %u responses", __func__, num);
 813         switch (ctxt->pam_done) {
 814         case 1:
 815                 sshpam_authenticated = 1;
 816                 return (0);
 817         case 0:
 818                 break;
 819         default:
 820                 return (-1);
 821         }
 822         if (num != 1) {
 823                 error("PAM: expected one response, got %u", num);
 824                 return (-1);
 825         }
 826         buffer_init(&buffer);
 827         if (sshpam_authctxt->valid &&
 828             (sshpam_authctxt->pw->pw_uid != 0 ||
 829             options.permit_root_login == PERMIT_YES))
 830                 buffer_put_cstring(&buffer, *resp);
 831         else
 832                 buffer_put_cstring(&buffer, badpw);
 833         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 834                 buffer_free(&buffer);
 835                 return (-1);
 836         }
 837         buffer_free(&buffer);
 838         return (1);
 839 }
 840
 841 static void
 842 sshpam_free_ctx(void *ctxtp)
 843 {
 844         struct pam_ctxt *ctxt = ctxtp;
 845
 846         debug3("PAM: %s entering", __func__);
 847         sshpam_thread_cleanup();
 848         xfree(ctxt);
 849         /*
 850          * We don't call sshpam_cleanup() here because we may need the PAM
 851          * handle at a later stage, e.g. when setting up a session.  It's
 852          * still on the cleanup list, so pam_end() *will* be called before
 853          * the server process terminates.
 854          */
 855 }
 856
 857 KbdintDevice sshpam_device = {
 858         "pam",
 859         sshpam_init_ctx,
 860         sshpam_query,
 861         sshpam_respond,
 862         sshpam_free_ctx
 863 };
 864
 865 KbdintDevice mm_sshpam_device = {
 866         "pam",
 867         mm_sshpam_init_ctx,
 868         mm_sshpam_query,
 869         mm_sshpam_respond,
 870         mm_sshpam_free_ctx
 871 };
 872
 873 /*
 874  * This replaces auth-pam.c
 875  */
 876 void
 877 start_pam(Authctxt *authctxt)
 878 {
 879         if (!options.use_pam)
 880                 fatal("PAM: initialisation requested when UsePAM=no");
 881
 882         if (sshpam_init(authctxt) == -1)
 883                 fatal("PAM: initialisation failed");
 884 }
 885
 886 void
 887 finish_pam(void)
 888 {
 889         sshpam_cleanup();
 890 }
 891
 892 u_int
 893 do_pam_account(void)
 894 {
 895         debug("%s: called", __func__);
 896         if (sshpam_account_status != -1)
 897                 return (sshpam_account_status);
 898
 899         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 900         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 901             pam_strerror(sshpam_handle, sshpam_err));
 902
 903         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 904                 sshpam_account_status = 0;
 905                 return (sshpam_account_status);
 906         }
 907
 908         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 909                 sshpam_password_change_required(1);
 910
 911         sshpam_account_status = 1;
 912         return (sshpam_account_status);
 913 }
 914
 915 void
 916 do_pam_set_tty(const char *tty)
 917 {
 918         if (tty != NULL) {
 919                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 920                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 921                 if (sshpam_err != PAM_SUCCESS)
 922                         fatal("PAM: failed to set PAM_TTY: %s",
 923                             pam_strerror(sshpam_handle, sshpam_err));
 924         }
 925 }
 926
 927 void
 928 do_pam_setcred(int init)
 929 {
 930         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 931             (const void *)&store_conv);
 932         if (sshpam_err != PAM_SUCCESS)
 933                 fatal("PAM: failed to set PAM_CONV: %s",
 934                     pam_strerror(sshpam_handle, sshpam_err));
 935         if (init) {
 936                 debug("PAM: establishing credentials");
 937                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 938         } else {
 939                 debug("PAM: reinitializing credentials");
 940                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 941         }
 942         if (sshpam_err == PAM_SUCCESS) {
 943                 sshpam_cred_established = 1;
 944                 return;
 945         }
 946         if (sshpam_authenticated)
 947                 fatal("PAM: pam_setcred(): %s",
 948                     pam_strerror(sshpam_handle, sshpam_err));
 949         else
 950                 debug("PAM: pam_setcred(): %s",
 951                     pam_strerror(sshpam_handle, sshpam_err));
 952 }
 953
 954 static int
 955 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 956     struct pam_response **resp, void *data)
 957 {
 958         char input[PAM_MAX_MSG_SIZE];
 959         struct pam_response *reply;
 960         int i;
 961
 962         debug3("PAM: %s called with %d messages", __func__, n);
 963
 964         *resp = NULL;
 965
 966         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 967                 return (PAM_CONV_ERR);
 968
 969         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 970                 return (PAM_CONV_ERR);
 971
 972         for (i = 0; i < n; ++i) {
 973                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 974                 case PAM_PROMPT_ECHO_OFF:
 975                         reply[i].resp =
 976                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 977                             RP_ALLOW_STDIN);
 978                         reply[i].resp_retcode = PAM_SUCCESS;
 979                         break;
 980                 case PAM_PROMPT_ECHO_ON:
 981                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 982                         fgets(input, sizeof input, stdin);
 983                         if ((reply[i].resp = strdup(input)) == NULL)
 984                                 goto fail;
 985                         reply[i].resp_retcode = PAM_SUCCESS;
 986                         break;
 987                 case PAM_ERROR_MSG:
 988                 case PAM_TEXT_INFO:
 989                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 990                         reply[i].resp_retcode = PAM_SUCCESS;
 991                         break;
 992                 default:
 993                         goto fail;
 994                 }
 995         }
 996         *resp = reply;
 997         return (PAM_SUCCESS);
 998
 999  fail:
1000         for(i = 0; i < n; i++) {
1001                 if (reply[i].resp != NULL)
1002                         xfree(reply[i].resp);
1003         }
1004         xfree(reply);
1005         return (PAM_CONV_ERR);
1006 }
1007
1008 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1009
1010 /*
1011  * XXX this should be done in the authentication phase, but ssh1 doesn't
1012  * support that
1013  */
1014 void
1015 do_pam_chauthtok(void)
1016 {
1017         if (use_privsep)
1018                 fatal("Password expired (unable to change with privsep)");
1019         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1020             (const void *)&tty_conv);
1021         if (sshpam_err != PAM_SUCCESS)
1022                 fatal("PAM: failed to set PAM_CONV: %s",
1023                     pam_strerror(sshpam_handle, sshpam_err));
1024         debug("PAM: changing password");
1025         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1026         if (sshpam_err != PAM_SUCCESS)
1027                 fatal("PAM: pam_chauthtok(): %s",
1028                     pam_strerror(sshpam_handle, sshpam_err));
1029 }
1030
1031 void
1032 do_pam_session(void)
1033 {
1034         debug3("PAM: opening session");
1035         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1036             (const void *)&store_conv);
1037         if (sshpam_err != PAM_SUCCESS)
1038                 fatal("PAM: failed to set PAM_CONV: %s",
1039                     pam_strerror(sshpam_handle, sshpam_err));
1040         sshpam_err = pam_open_session(sshpam_handle, 0);
1041         if (sshpam_err == PAM_SUCCESS)
1042                 sshpam_session_open = 1;
1043         else {
1044                 sshpam_session_open = 0;
1045                 disable_forwarding();
1046                 error("PAM: pam_open_session(): %s",
1047                     pam_strerror(sshpam_handle, sshpam_err));
1048         }
1049
1050 }
1051
1052 int
1053 is_pam_session_open(void)
1054 {
1055         return sshpam_session_open;
1056 }
1057
1058 /*
1059  * Set a PAM environment string. We need to do this so that the session
1060  * modules can handle things like Kerberos/GSI credentials that appear
1061  * during the ssh authentication process.
1062  */
1063 int
1064 do_pam_putenv(char *name, char *value)
1065 {
1066         int ret = 1;
1067 #ifdef HAVE_PAM_PUTENV
1068         char *compound;
1069         size_t len;
1070
1071         len = strlen(name) + strlen(value) + 2;
1072         compound = xmalloc(len);
1073
1074         snprintf(compound, len, "%s=%s", name, value);
1075         ret = pam_putenv(sshpam_handle, compound);
1076         xfree(compound);
1077 #endif
1078
1079         return (ret);
1080 }
1081
1082 char **
1083 fetch_pam_child_environment(void)
1084 {
1085         return sshpam_env;
1086 }
1087
1088 char **
1089 fetch_pam_environment(void)
1090 {
1091         return (pam_getenvlist(sshpam_handle));
1092 }
1093
1094 void
1095 free_pam_environment(char **env)
1096 {
1097         char **envp;
1098
1099         if (env == NULL)
1100                 return;
1101
1102         for (envp = env; *envp; envp++)
1103                 xfree(*envp);
1104         xfree(env);
1105 }
1106
1107 /*
1108  * "Blind" conversation function for password authentication.  Assumes that
1109  * echo-off prompts are for the password and stores messages for later
1110  * display.
1111  */
1112 static int
1113 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1114     struct pam_response **resp, void *data)
1115 {
1116         struct pam_response *reply;
1117         int i;
1118         size_t len;
1119
1120         debug3("PAM: %s called with %d messages", __func__, n);
1121
1122         *resp = NULL;
1123
1124         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1125                 return (PAM_CONV_ERR);
1126
1127         if ((reply = malloc(n * sizeof(*reply))) == NULL)
1128                 return (PAM_CONV_ERR);
1129         memset(reply, 0, n * sizeof(*reply));
1130
1131         for (i = 0; i < n; ++i) {
1132                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1133                 case PAM_PROMPT_ECHO_OFF:
1134                         if (sshpam_password == NULL)
1135                                 goto fail;
1136                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1137                                 goto fail;
1138                         reply[i].resp_retcode = PAM_SUCCESS;
1139                         break;
1140                 case PAM_ERROR_MSG:
1141                 case PAM_TEXT_INFO:
1142                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1143                         if (len > 0) {
1144                                 buffer_append(&loginmsg,
1145                                     PAM_MSG_MEMBER(msg, i, msg), len);
1146                                 buffer_append(&loginmsg, "\n", 1);
1147                         }
1148                         if ((reply[i].resp = strdup("")) == NULL)
1149                                 goto fail;
1150                         reply[i].resp_retcode = PAM_SUCCESS;
1151                         break;
1152                 default:
1153                         goto fail;
1154                 }
1155         }
1156         *resp = reply;
1157         return (PAM_SUCCESS);
1158
1159  fail:
1160         for(i = 0; i < n; i++) {
1161                 if (reply[i].resp != NULL)
1162                         xfree(reply[i].resp);
1163         }
1164         xfree(reply);
1165         return (PAM_CONV_ERR);
1166 }
1167
1168 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1169
1170 /*
1171  * Attempt password authentication via PAM
1172  */
1173 int
1174 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1175 {
1176         int flags = (options.permit_empty_passwd == 0 ?
1177             PAM_DISALLOW_NULL_AUTHTOK : 0);
1178
1179         if (!options.use_pam || sshpam_handle == NULL)
1180                 fatal("PAM: %s called when PAM disabled or failed to "
1181                     "initialise.", __func__);
1182
1183         sshpam_password = password;
1184         sshpam_authctxt = authctxt;
1185
1186         /*
1187          * If the user logging in is invalid, or is root but is not permitted
1188          * by PermitRootLogin, use an invalid password to prevent leaking
1189          * information via timing (eg if the PAM config has a delay on fail).
1190          */
1191         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1192             options.permit_root_login != PERMIT_YES))
1193                 sshpam_password = badpw;
1194
1195         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1196             (const void *)&passwd_conv);
1197         if (sshpam_err != PAM_SUCCESS)
1198                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1199                     pam_strerror(sshpam_handle, sshpam_err));
1200
1201         sshpam_err = pam_authenticate(sshpam_handle, flags);
1202         sshpam_password = NULL;
1203         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1204                 debug("PAM: password authentication accepted for %.100s",
1205                     authctxt->user);
1206                 return 1;
1207         } else {
1208                 debug("PAM: password authentication failed for %.100s: %s",
1209                     authctxt->valid ? authctxt->user : "an illegal user",
1210                     pam_strerror(sshpam_handle, sshpam_err));
1211                 return 0;
1212         }
1213 }
1214 #endif /* USE_PAM */