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 $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                 sigdie("PAM: authentication thread exited unexpectedly");
 165         if (WEXITSTATUS(sshpam_thread_status) != 0)
 166                 sigdie("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                 free(reply[i].resp);
 416         }
 417         free(reply);
 418         buffer_free(&buffer);
 419         return (PAM_CONV_ERR);
 420 }
 421
 422 /*
 423  * Authentication thread.
 424  */
 425 static void *
 426 sshpam_thread(void *ctxtp)
 427 {
 428         struct pam_ctxt *ctxt = ctxtp;
 429         Buffer buffer;
 430         struct pam_conv sshpam_conv;
 431         int flags = (options.permit_empty_passwd == 0 ?
 432             PAM_DISALLOW_NULL_AUTHTOK : 0);
 433 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 434         extern char **environ;
 435         char **env_from_pam;
 436         u_int i;
 437         const char *pam_user;
 438         const char **ptr_pam_user = &pam_user;
 439         char *tz = getenv("TZ");
 440
 441         pam_get_item(sshpam_handle, PAM_USER,
 442             (sshpam_const void **)ptr_pam_user);
 443
 444         environ[0] = NULL;
 445         if (tz != NULL)
 446                 if (setenv("TZ", tz, 1) == -1)
 447                         error("PAM: could not set TZ environment: %s",
 448                             strerror(errno));
 449
 450         if (sshpam_authctxt != NULL) {
 451                 setproctitle("%s [pam]",
 452                     sshpam_authctxt->valid ? pam_user : "unknown");
 453         }
 454 #endif
 455
 456         sshpam_conv.conv = sshpam_thread_conv;
 457         sshpam_conv.appdata_ptr = ctxt;
 458
 459         if (sshpam_authctxt == NULL)
 460                 fatal("%s: PAM authctxt not initialized", __func__);
 461
 462         buffer_init(&buffer);
 463         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 464             (const void *)&sshpam_conv);
 465         if (sshpam_err != PAM_SUCCESS)
 466                 goto auth_fail;
 467         sshpam_err = pam_authenticate(sshpam_handle, flags);
 468         if (sshpam_err != PAM_SUCCESS)
 469                 goto auth_fail;
 470
 471         if (compat20) {
 472                 if (!do_pam_account()) {
 473                         sshpam_err = PAM_ACCT_EXPIRED;
 474                         goto auth_fail;
 475                 }
 476                 if (sshpam_authctxt->force_pwchange) {
 477                         sshpam_err = pam_chauthtok(sshpam_handle,
 478                             PAM_CHANGE_EXPIRED_AUTHTOK);
 479                         if (sshpam_err != PAM_SUCCESS)
 480                                 goto auth_fail;
 481                         sshpam_password_change_required(0);
 482                 }
 483         }
 484
 485         buffer_put_cstring(&buffer, "OK");
 486
 487 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 488         /* Export variables set by do_pam_account */
 489         buffer_put_int(&buffer, sshpam_account_status);
 490         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 491
 492         /* Export any environment strings set in child */
 493         for(i = 0; environ[i] != NULL; i++)
 494                 ; /* Count */
 495         buffer_put_int(&buffer, i);
 496         for(i = 0; environ[i] != NULL; i++)
 497                 buffer_put_cstring(&buffer, environ[i]);
 498
 499         /* Export any environment strings set by PAM in child */
 500         env_from_pam = pam_getenvlist(sshpam_handle);
 501         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 502                 ; /* Count */
 503         buffer_put_int(&buffer, i);
 504         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 505                 buffer_put_cstring(&buffer, env_from_pam[i]);
 506 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 507
 508         /* XXX - can't do much about an error here */
 509         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 510         buffer_free(&buffer);
 511         pthread_exit(NULL);
 512
 513  auth_fail:
 514         buffer_put_cstring(&buffer,
 515             pam_strerror(sshpam_handle, sshpam_err));
 516         /* XXX - can't do much about an error here */
 517         if (sshpam_err == PAM_ACCT_EXPIRED)
 518                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);
 519         else
 520                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 521         buffer_free(&buffer);
 522         pthread_exit(NULL);
 523
 524         return (NULL); /* Avoid warning for non-pthread case */
 525 }
 526
 527 void
 528 sshpam_thread_cleanup(void)
 529 {
 530         struct pam_ctxt *ctxt = cleanup_ctxt;
 531
 532         debug3("PAM: %s entering", __func__);
 533         if (ctxt != NULL && ctxt->pam_thread != 0) {
 534                 pthread_cancel(ctxt->pam_thread);
 535                 pthread_join(ctxt->pam_thread, NULL);
 536                 close(ctxt->pam_psock);
 537                 close(ctxt->pam_csock);
 538                 memset(ctxt, 0, sizeof(*ctxt));
 539                 cleanup_ctxt = NULL;
 540         }
 541 }
 542
 543 static int
 544 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 545     struct pam_response **resp, void *data)
 546 {
 547         debug3("PAM: %s entering, %d messages", __func__, n);
 548         return (PAM_CONV_ERR);
 549 }
 550
 551 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 552
 553 static int
 554 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 555     struct pam_response **resp, void *data)
 556 {
 557         struct pam_response *reply;
 558         int i;
 559         size_t len;
 560
 561         debug3("PAM: %s called with %d messages", __func__, n);
 562         *resp = NULL;
 563
 564         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 565                 return (PAM_CONV_ERR);
 566
 567         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 568                 return (PAM_CONV_ERR);
 569
 570         for (i = 0; i < n; ++i) {
 571                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 572                 case PAM_ERROR_MSG:
 573                 case PAM_TEXT_INFO:
 574                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 575                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 576                         buffer_append(&loginmsg, "\n", 1 );
 577                         reply[i].resp_retcode = PAM_SUCCESS;
 578                         break;
 579                 default:
 580                         goto fail;
 581                 }
 582         }
 583         *resp = reply;
 584         return (PAM_SUCCESS);
 585
 586  fail:
 587         for(i = 0; i < n; i++) {
 588                 free(reply[i].resp);
 589         }
 590         free(reply);
 591         return (PAM_CONV_ERR);
 592 }
 593
 594 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 595
 596 void
 597 sshpam_cleanup(void)
 598 {
 599         if (sshpam_handle == NULL || (use_privsep && !mm_is_monitor()))
 600                 return;
 601         debug("PAM: cleanup");
 602         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 603         if (sshpam_session_open) {
 604                 debug("PAM: closing session");
 605                 pam_close_session(sshpam_handle, PAM_SILENT);
 606                 sshpam_session_open = 0;
 607         }
 608         if (sshpam_cred_established) {
 609                 debug("PAM: deleting credentials");
 610                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 611                 sshpam_cred_established = 0;
 612         }
 613         sshpam_authenticated = 0;
 614         pam_end(sshpam_handle, sshpam_err);
 615         sshpam_handle = NULL;
 616 }
 617
 618 static int
 619 sshpam_init(Authctxt *authctxt)
 620 {
 621         extern char *__progname;
 622         const char *pam_rhost, *pam_user, *user = authctxt->user;
 623         const char **ptr_pam_user = &pam_user;
 624
 625         if (sshpam_handle != NULL) {
 626                 /* We already have a PAM context; check if the user matches */
 627                 sshpam_err = pam_get_item(sshpam_handle,
 628                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 629                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 630                         return (0);
 631                 pam_end(sshpam_handle, sshpam_err);
 632                 sshpam_handle = NULL;
 633         }
 634         debug("PAM: initializing for \"%s\"", user);
 635         sshpam_err =
 636             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 637         sshpam_authctxt = authctxt;
 638
 639         if (sshpam_err != PAM_SUCCESS) {
 640                 pam_end(sshpam_handle, sshpam_err);
 641                 sshpam_handle = NULL;
 642                 return (-1);
 643         }
 644         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 645         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 646         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 647         if (sshpam_err != PAM_SUCCESS) {
 648                 pam_end(sshpam_handle, sshpam_err);
 649                 sshpam_handle = NULL;
 650                 return (-1);
 651         }
 652 #ifdef PAM_TTY_KLUDGE
 653         /*
 654          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 655          * sshd doesn't set the tty until too late in the auth process and
 656          * may not even set one (for tty-less connections)
 657          */
 658         debug("PAM: setting PAM_TTY to \"ssh\"");
 659         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 660         if (sshpam_err != PAM_SUCCESS) {
 661                 pam_end(sshpam_handle, sshpam_err);
 662                 sshpam_handle = NULL;
 663                 return (-1);
 664         }
 665 #endif
 666         return (0);
 667 }
 668
 669 static void *
 670 sshpam_init_ctx(Authctxt *authctxt)
 671 {
 672         struct pam_ctxt *ctxt;
 673         int socks[2];
 674
 675         debug3("PAM: %s entering", __func__);
 676         /*
 677          * Refuse to start if we don't have PAM enabled or do_pam_account
 678          * has previously failed.
 679          */
 680         if (!options.use_pam || sshpam_account_status == 0)
 681                 return NULL;
 682
 683         /* Initialize PAM */
 684         if (sshpam_init(authctxt) == -1) {
 685                 error("PAM: initialization failed");
 686                 return (NULL);
 687         }
 688
 689         ctxt = xcalloc(1, sizeof *ctxt);
 690
 691         /* Start the authentication thread */
 692         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 693                 error("PAM: failed create sockets: %s", strerror(errno));
 694                 free(ctxt);
 695                 return (NULL);
 696         }
 697         ctxt->pam_psock = socks[0];
 698         ctxt->pam_csock = socks[1];
 699         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 700                 error("PAM: failed to start authentication thread: %s",
 701                     strerror(errno));
 702                 close(socks[0]);
 703                 close(socks[1]);
 704                 free(ctxt);
 705                 return (NULL);
 706         }
 707         cleanup_ctxt = ctxt;
 708         return (ctxt);
 709 }
 710
 711 static int
 712 sshpam_query(void *ctx, char **name, char **info,
 713     u_int *num, char ***prompts, u_int **echo_on)
 714 {
 715         Buffer buffer;
 716         struct pam_ctxt *ctxt = ctx;
 717         size_t plen;
 718         u_char type;
 719         char *msg;
 720         size_t len, mlen;
 721
 722         debug3("PAM: %s entering", __func__);
 723         buffer_init(&buffer);
 724         *name = xstrdup("");
 725         *info = xstrdup("");
 726         *prompts = xmalloc(sizeof(char *));
 727         **prompts = NULL;
 728         plen = 0;
 729         *echo_on = xmalloc(sizeof(u_int));
 730         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 731                 type = buffer_get_char(&buffer);
 732                 msg = buffer_get_string(&buffer, NULL);
 733                 mlen = strlen(msg);
 734                 switch (type) {
 735                 case PAM_PROMPT_ECHO_ON:
 736                 case PAM_PROMPT_ECHO_OFF:
 737                         *num = 1;
 738                         len = plen + mlen + 1;
 739                         **prompts = xrealloc(**prompts, 1, len);
 740                         strlcpy(**prompts + plen, msg, len - plen);
 741                         plen += mlen;
 742                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 743                         free(msg);
 744                         return (0);
 745                 case PAM_ERROR_MSG:
 746                 case PAM_TEXT_INFO:
 747                         /* accumulate messages */
 748                         len = plen + mlen + 2;
 749                         **prompts = xrealloc(**prompts, 1, len);
 750                         strlcpy(**prompts + plen, msg, len - plen);
 751                         plen += mlen;
 752                         strlcat(**prompts + plen, "\n", len - plen);
 753                         plen++;
 754                         free(msg);
 755                         break;
 756                 case PAM_ACCT_EXPIRED:
 757                         sshpam_account_status = 0;
 758                         /* FALLTHROUGH */
 759                 case PAM_AUTH_ERR:
 760                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 761                         if (**prompts != NULL && strlen(**prompts) != 0) {
 762                                 *info = **prompts;
 763                                 **prompts = NULL;
 764                                 *num = 0;
 765                                 **echo_on = 0;
 766                                 ctxt->pam_done = -1;
 767                                 free(msg);
 768                                 return 0;
 769                         }
 770                         /* FALLTHROUGH */
 771                 case PAM_SUCCESS:
 772                         if (**prompts != NULL) {
 773                                 /* drain any accumulated messages */
 774                                 debug("PAM: %s", **prompts);
 775                                 buffer_append(&loginmsg, **prompts,
 776                                     strlen(**prompts));
 777                                 free(**prompts);
 778                                 **prompts = NULL;
 779                         }
 780                         if (type == PAM_SUCCESS) {
 781                                 if (!sshpam_authctxt->valid ||
 782                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 783                                     options.permit_root_login != PERMIT_YES))
 784                                         fatal("Internal error: PAM auth "
 785                                             "succeeded when it should have "
 786                                             "failed");
 787                                 import_environments(&buffer);
 788                                 *num = 0;
 789                                 **echo_on = 0;
 790                                 ctxt->pam_done = 1;
 791                                 free(msg);
 792                                 return (0);
 793                         }
 794                         error("PAM: %s for %s%.100s from %.100s", msg,
 795                             sshpam_authctxt->valid ? "" : "illegal user ",
 796                             sshpam_authctxt->user,
 797                             get_remote_name_or_ip(utmp_len, options.use_dns));
 798                         /* FALLTHROUGH */
 799                 default:
 800                         *num = 0;
 801                         **echo_on = 0;
 802                         free(msg);
 803                         ctxt->pam_done = -1;
 804                         return (-1);
 805                 }
 806         }
 807         return (-1);
 808 }
 809
 810 /* XXX - see also comment in auth-chall.c:verify_response */
 811 static int
 812 sshpam_respond(void *ctx, u_int num, char **resp)
 813 {
 814         Buffer buffer;
 815         struct pam_ctxt *ctxt = ctx;
 816
 817         debug2("PAM: %s entering, %u responses", __func__, num);
 818         switch (ctxt->pam_done) {
 819         case 1:
 820                 sshpam_authenticated = 1;
 821                 return (0);
 822         case 0:
 823                 break;
 824         default:
 825                 return (-1);
 826         }
 827         if (num != 1) {
 828                 error("PAM: expected one response, got %u", num);
 829                 return (-1);
 830         }
 831         buffer_init(&buffer);
 832         if (sshpam_authctxt->valid &&
 833             (sshpam_authctxt->pw->pw_uid != 0 ||
 834             options.permit_root_login == PERMIT_YES))
 835                 buffer_put_cstring(&buffer, *resp);
 836         else
 837                 buffer_put_cstring(&buffer, badpw);
 838         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 839                 buffer_free(&buffer);
 840                 return (-1);
 841         }
 842         buffer_free(&buffer);
 843         return (1);
 844 }
 845
 846 static void
 847 sshpam_free_ctx(void *ctxtp)
 848 {
 849         struct pam_ctxt *ctxt = ctxtp;
 850
 851         debug3("PAM: %s entering", __func__);
 852         sshpam_thread_cleanup();
 853         free(ctxt);
 854         /*
 855          * We don't call sshpam_cleanup() here because we may need the PAM
 856          * handle at a later stage, e.g. when setting up a session.  It's
 857          * still on the cleanup list, so pam_end() *will* be called before
 858          * the server process terminates.
 859          */
 860 }
 861
 862 KbdintDevice sshpam_device = {
 863         "pam",
 864         sshpam_init_ctx,
 865         sshpam_query,
 866         sshpam_respond,
 867         sshpam_free_ctx
 868 };
 869
 870 KbdintDevice mm_sshpam_device = {
 871         "pam",
 872         mm_sshpam_init_ctx,
 873         mm_sshpam_query,
 874         mm_sshpam_respond,
 875         mm_sshpam_free_ctx
 876 };
 877
 878 /*
 879  * This replaces auth-pam.c
 880  */
 881 void
 882 start_pam(Authctxt *authctxt)
 883 {
 884         if (!options.use_pam)
 885                 fatal("PAM: initialisation requested when UsePAM=no");
 886
 887         if (sshpam_init(authctxt) == -1)
 888                 fatal("PAM: initialisation failed");
 889 }
 890
 891 void
 892 finish_pam(void)
 893 {
 894         sshpam_cleanup();
 895 }
 896
 897 u_int
 898 do_pam_account(void)
 899 {
 900         debug("%s: called", __func__);
 901         if (sshpam_account_status != -1)
 902                 return (sshpam_account_status);
 903
 904         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 905         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 906             pam_strerror(sshpam_handle, sshpam_err));
 907
 908         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 909                 sshpam_account_status = 0;
 910                 return (sshpam_account_status);
 911         }
 912
 913         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 914                 sshpam_password_change_required(1);
 915
 916         sshpam_account_status = 1;
 917         return (sshpam_account_status);
 918 }
 919
 920 void
 921 do_pam_set_tty(const char *tty)
 922 {
 923         if (tty != NULL) {
 924                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 925                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 926                 if (sshpam_err != PAM_SUCCESS)
 927                         fatal("PAM: failed to set PAM_TTY: %s",
 928                             pam_strerror(sshpam_handle, sshpam_err));
 929         }
 930 }
 931
 932 void
 933 do_pam_setcred(int init)
 934 {
 935         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 936             (const void *)&store_conv);
 937         if (sshpam_err != PAM_SUCCESS)
 938                 fatal("PAM: failed to set PAM_CONV: %s",
 939                     pam_strerror(sshpam_handle, sshpam_err));
 940         if (init) {
 941                 debug("PAM: establishing credentials");
 942                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 943         } else {
 944                 debug("PAM: reinitializing credentials");
 945                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 946         }
 947         if (sshpam_err == PAM_SUCCESS) {
 948                 sshpam_cred_established = 1;
 949                 return;
 950         }
 951         if (sshpam_authenticated)
 952                 fatal("PAM: pam_setcred(): %s",
 953                     pam_strerror(sshpam_handle, sshpam_err));
 954         else
 955                 debug("PAM: pam_setcred(): %s",
 956                     pam_strerror(sshpam_handle, sshpam_err));
 957 }
 958
 959 static int
 960 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 961     struct pam_response **resp, void *data)
 962 {
 963         char input[PAM_MAX_MSG_SIZE];
 964         struct pam_response *reply;
 965         int i;
 966
 967         debug3("PAM: %s called with %d messages", __func__, n);
 968
 969         *resp = NULL;
 970
 971         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 972                 return (PAM_CONV_ERR);
 973
 974         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 975                 return (PAM_CONV_ERR);
 976
 977         for (i = 0; i < n; ++i) {
 978                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 979                 case PAM_PROMPT_ECHO_OFF:
 980                         reply[i].resp =
 981                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 982                             RP_ALLOW_STDIN);
 983                         reply[i].resp_retcode = PAM_SUCCESS;
 984                         break;
 985                 case PAM_PROMPT_ECHO_ON:
 986                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 987                         if (fgets(input, sizeof input, stdin) == NULL)
 988                                 input[0] = '\0';
 989                         if ((reply[i].resp = strdup(input)) == NULL)
 990                                 goto fail;
 991                         reply[i].resp_retcode = PAM_SUCCESS;
 992                         break;
 993                 case PAM_ERROR_MSG:
 994                 case PAM_TEXT_INFO:
 995                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 996                         reply[i].resp_retcode = PAM_SUCCESS;
 997                         break;
 998                 default:
 999                         goto fail;
1000                 }
1001         }
1002         *resp = reply;
1003         return (PAM_SUCCESS);
1004
1005  fail:
1006         for(i = 0; i < n; i++) {
1007                 free(reply[i].resp);
1008         }
1009         free(reply);
1010         return (PAM_CONV_ERR);
1011 }
1012
1013 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1014
1015 /*
1016  * XXX this should be done in the authentication phase, but ssh1 doesn't
1017  * support that
1018  */
1019 void
1020 do_pam_chauthtok(void)
1021 {
1022         if (use_privsep)
1023                 fatal("Password expired (unable to change with privsep)");
1024         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1025             (const void *)&tty_conv);
1026         if (sshpam_err != PAM_SUCCESS)
1027                 fatal("PAM: failed to set PAM_CONV: %s",
1028                     pam_strerror(sshpam_handle, sshpam_err));
1029         debug("PAM: changing password");
1030         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1031         if (sshpam_err != PAM_SUCCESS)
1032                 fatal("PAM: pam_chauthtok(): %s",
1033                     pam_strerror(sshpam_handle, sshpam_err));
1034 }
1035
1036 void
1037 do_pam_session(void)
1038 {
1039         debug3("PAM: opening session");
1040         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1041             (const void *)&store_conv);
1042         if (sshpam_err != PAM_SUCCESS)
1043                 fatal("PAM: failed to set PAM_CONV: %s",
1044                     pam_strerror(sshpam_handle, sshpam_err));
1045         sshpam_err = pam_open_session(sshpam_handle, 0);
1046         if (sshpam_err == PAM_SUCCESS)
1047                 sshpam_session_open = 1;
1048         else {
1049                 sshpam_session_open = 0;
1050                 disable_forwarding();
1051                 error("PAM: pam_open_session(): %s",
1052                     pam_strerror(sshpam_handle, sshpam_err));
1053         }
1054
1055 }
1056
1057 int
1058 is_pam_session_open(void)
1059 {
1060         return sshpam_session_open;
1061 }
1062
1063 /*
1064  * Set a PAM environment string. We need to do this so that the session
1065  * modules can handle things like Kerberos/GSI credentials that appear
1066  * during the ssh authentication process.
1067  */
1068 int
1069 do_pam_putenv(char *name, char *value)
1070 {
1071         int ret = 1;
1072 #ifdef HAVE_PAM_PUTENV
1073         char *compound;
1074         size_t len;
1075
1076         len = strlen(name) + strlen(value) + 2;
1077         compound = xmalloc(len);
1078
1079         snprintf(compound, len, "%s=%s", name, value);
1080         ret = pam_putenv(sshpam_handle, compound);
1081         free(compound);
1082 #endif
1083
1084         return (ret);
1085 }
1086
1087 char **
1088 fetch_pam_child_environment(void)
1089 {
1090         return sshpam_env;
1091 }
1092
1093 char **
1094 fetch_pam_environment(void)
1095 {
1096         return (pam_getenvlist(sshpam_handle));
1097 }
1098
1099 void
1100 free_pam_environment(char **env)
1101 {
1102         char **envp;
1103
1104         if (env == NULL)
1105                 return;
1106
1107         for (envp = env; *envp; envp++)
1108                 free(*envp);
1109         free(env);
1110 }
1111
1112 /*
1113  * "Blind" conversation function for password authentication.  Assumes that
1114  * echo-off prompts are for the password and stores messages for later
1115  * display.
1116  */
1117 static int
1118 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1119     struct pam_response **resp, void *data)
1120 {
1121         struct pam_response *reply;
1122         int i;
1123         size_t len;
1124
1125         debug3("PAM: %s called with %d messages", __func__, n);
1126
1127         *resp = NULL;
1128
1129         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1130                 return (PAM_CONV_ERR);
1131
1132         if ((reply = calloc(n, sizeof(*reply))) == NULL)
1133                 return (PAM_CONV_ERR);
1134
1135         for (i = 0; i < n; ++i) {
1136                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1137                 case PAM_PROMPT_ECHO_OFF:
1138                         if (sshpam_password == NULL)
1139                                 goto fail;
1140                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1141                                 goto fail;
1142                         reply[i].resp_retcode = PAM_SUCCESS;
1143                         break;
1144                 case PAM_ERROR_MSG:
1145                 case PAM_TEXT_INFO:
1146                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1147                         if (len > 0) {
1148                                 buffer_append(&loginmsg,
1149                                     PAM_MSG_MEMBER(msg, i, msg), len);
1150                                 buffer_append(&loginmsg, "\n", 1);
1151                         }
1152                         if ((reply[i].resp = strdup("")) == NULL)
1153                                 goto fail;
1154                         reply[i].resp_retcode = PAM_SUCCESS;
1155                         break;
1156                 default:
1157                         goto fail;
1158                 }
1159         }
1160         *resp = reply;
1161         return (PAM_SUCCESS);
1162
1163  fail:
1164         for(i = 0; i < n; i++) {
1165                 free(reply[i].resp);
1166         }
1167         free(reply);
1168         return (PAM_CONV_ERR);
1169 }
1170
1171 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1172
1173 /*
1174  * Attempt password authentication via PAM
1175  */
1176 int
1177 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1178 {
1179         int flags = (options.permit_empty_passwd == 0 ?
1180             PAM_DISALLOW_NULL_AUTHTOK : 0);
1181
1182         if (!options.use_pam || sshpam_handle == NULL)
1183                 fatal("PAM: %s called when PAM disabled or failed to "
1184                     "initialise.", __func__);
1185
1186         sshpam_password = password;
1187         sshpam_authctxt = authctxt;
1188
1189         /*
1190          * If the user logging in is invalid, or is root but is not permitted
1191          * by PermitRootLogin, use an invalid password to prevent leaking
1192          * information via timing (eg if the PAM config has a delay on fail).
1193          */
1194         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1195             options.permit_root_login != PERMIT_YES))
1196                 sshpam_password = badpw;
1197
1198         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1199             (const void *)&passwd_conv);
1200         if (sshpam_err != PAM_SUCCESS)
1201                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1202                     pam_strerror(sshpam_handle, sshpam_err));
1203
1204         sshpam_err = pam_authenticate(sshpam_handle, flags);
1205         sshpam_password = NULL;
1206         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1207                 debug("PAM: password authentication accepted for %.100s",
1208                     authctxt->user);
1209                 return 1;
1210         } else {
1211                 debug("PAM: password authentication failed for %.100s: %s",
1212                     authctxt->valid ? authctxt->user : "an illegal user",
1213                     pam_strerror(sshpam_handle, sshpam_err));
1214                 return 0;
1215         }
1216 }
1217 #endif /* USE_PAM */