auth-pam.c

   1 /*-
   2  * Copyright (c) 2002 Networks Associates Technology, Inc.
   3  * All rights reserved.
   4  *
   5  * This software was developed for the FreeBSD Project by ThinkSec AS and
   6  * NAI Labs, the Security Research Division of Network Associates, Inc.
   7  * under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the
   8  * DARPA CHATS research program.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31 /*
  32  * Copyright (c) 2003,2004 Damien Miller <djm@mindrot.org>
  33  * Copyright (c) 2003,2004 Darren Tucker <dtucker@zip.com.au>
  34  *
  35  * Permission to use, copy, modify, and distribute this software for any
  36  * purpose with or without fee is hereby granted, provided that the above
  37  * copyright notice and this permission notice appear in all copies.
  38  *
  39  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  40  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  41  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  42  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  43  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  44  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  45  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  46  */
  47
  48 /* Based on $FreeBSD: src/crypto/openssh/auth2-pam-freebsd.c,v 1.11 2003/03/31 13:48:18 des Exp $ */
  49 #include "includes.h"
  50
  51 #include <sys/types.h>
  52 #include <sys/stat.h>
  53 #include <sys/wait.h>
  54
  55 #include <errno.h>
  56 #include <signal.h>
  57 #include <string.h>
  58 #include <unistd.h>
  59
  60 #ifdef USE_PAM
  61 #if defined(HAVE_SECURITY_PAM_APPL_H)
  62 #include <security/pam_appl.h>
  63 #elif defined (HAVE_PAM_PAM_APPL_H)
  64 #include <pam/pam_appl.h>
  65 #endif
  66
  67 /* OpenGroup RFC86.0 and XSSO specify no "const" on arguments */
  68 #ifdef PAM_SUN_CODEBASE
  69 # define sshpam_const           /* Solaris, HP-UX, AIX */
  70 #else
  71 # define sshpam_const   const   /* LinuxPAM, OpenPAM */
  72 #endif
  73
  74 /* Ambiguity in spec: is it an array of pointers or a pointer to an array? */
  75 #ifdef PAM_SUN_CODEBASE
  76 # define PAM_MSG_MEMBER(msg, n, member) ((*(msg))[(n)].member)
  77 #else
  78 # define PAM_MSG_MEMBER(msg, n, member) ((msg)[(n)]->member)
  79 #endif
  80
  81 #include "auth.h"
  82 #include "auth-pam.h"
  83 #include "buffer.h"
  84 #include "bufaux.h"
  85 #include "canohost.h"
  86 #include "log.h"
  87 #include "monitor_wrap.h"
  88 #include "msg.h"
  89 #include "packet.h"
  90 #include "misc.h"
  91 #include "servconf.h"
  92 #include "ssh2.h"
  93 #include "xmalloc.h"
  94 #include "auth-options.h"
  95
  96 extern ServerOptions options;
  97 extern Buffer loginmsg;
  98 extern int compat20;
  99 extern u_int utmp_len;
 100
 101 /* so we don't silently change behaviour */
 102 #ifdef USE_POSIX_THREADS
 103 # error "USE_POSIX_THREADS replaced by UNSUPPORTED_POSIX_THREADS_HACK"
 104 #endif
 105
 106 /*
 107  * Formerly known as USE_POSIX_THREADS, using this is completely unsupported
 108  * and generally a bad idea.  Use at own risk and do not expect support if
 109  * this breaks.
 110  */
 111 #ifdef UNSUPPORTED_POSIX_THREADS_HACK
 112 #include <pthread.h>
 113 /*
 114  * Avoid namespace clash when *not* using pthreads for systems *with*
 115  * pthreads, which unconditionally define pthread_t via sys/types.h
 116  * (e.g. Linux)
 117  */
 118 typedef pthread_t sp_pthread_t;
 119 #else
 120 typedef pid_t sp_pthread_t;
 121 #endif
 122
 123 struct pam_ctxt {
 124         sp_pthread_t     pam_thread;
 125         int              pam_psock;
 126         int              pam_csock;
 127         int              pam_done;
 128 };
 129
 130 static void sshpam_free_ctx(void *);
 131 static struct pam_ctxt *cleanup_ctxt;
 132
 133 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 134 /*
 135  * Simulate threads with processes.
 136  */
 137
 138 static int sshpam_thread_status = -1;
 139 static mysig_t sshpam_oldsig;
 140
 141 static void
 142 sshpam_sigchld_handler(int sig)
 143 {
 144         signal(SIGCHLD, SIG_DFL);
 145         if (cleanup_ctxt == NULL)
 146                 return; /* handler called after PAM cleanup, shouldn't happen */
 147         if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, WNOHANG)
 148             <= 0) {
 149                 /* PAM thread has not exitted, privsep slave must have */
 150                 kill(cleanup_ctxt->pam_thread, SIGTERM);
 151                 if (waitpid(cleanup_ctxt->pam_thread, &sshpam_thread_status, 0)
 152                     <= 0)
 153                         return; /* could not wait */
 154         }
 155         if (WIFSIGNALED(sshpam_thread_status) &&
 156             WTERMSIG(sshpam_thread_status) == SIGTERM)
 157                 return; /* terminated by pthread_cancel */
 158         if (!WIFEXITED(sshpam_thread_status))
 159                 fatal("PAM: authentication thread exited unexpectedly");
 160         if (WEXITSTATUS(sshpam_thread_status) != 0)
 161                 fatal("PAM: authentication thread exited uncleanly");
 162 }
 163
 164 /* ARGSUSED */
 165 static void
 166 pthread_exit(void *value)
 167 {
 168         _exit(0);
 169 }
 170
 171 /* ARGSUSED */
 172 static int
 173 pthread_create(sp_pthread_t *thread, const void *attr,
 174     void *(*thread_start)(void *), void *arg)
 175 {
 176         pid_t pid;
 177         struct pam_ctxt *ctx = arg;
 178
 179         sshpam_thread_status = -1;
 180         switch ((pid = fork())) {
 181         case -1:
 182                 error("fork(): %s", strerror(errno));
 183                 return (-1);
 184         case 0:
 185                 close(ctx->pam_psock);
 186                 ctx->pam_psock = -1;
 187                 thread_start(arg);
 188                 _exit(1);
 189         default:
 190                 *thread = pid;
 191                 close(ctx->pam_csock);
 192                 ctx->pam_csock = -1;
 193                 sshpam_oldsig = signal(SIGCHLD, sshpam_sigchld_handler);
 194                 return (0);
 195         }
 196 }
 197
 198 static int
 199 pthread_cancel(sp_pthread_t thread)
 200 {
 201         signal(SIGCHLD, sshpam_oldsig);
 202         return (kill(thread, SIGTERM));
 203 }
 204
 205 /* ARGSUSED */
 206 static int
 207 pthread_join(sp_pthread_t thread, void **value)
 208 {
 209         int status;
 210
 211         if (sshpam_thread_status != -1)
 212                 return (sshpam_thread_status);
 213         signal(SIGCHLD, sshpam_oldsig);
 214         waitpid(thread, &status, 0);
 215         return (status);
 216 }
 217 #endif
 218
 219
 220 static pam_handle_t *sshpam_handle = NULL;
 221 static int sshpam_err = 0;
 222 static int sshpam_authenticated = 0;
 223 static int sshpam_session_open = 0;
 224 static int sshpam_cred_established = 0;
 225 static int sshpam_account_status = -1;
 226 static char **sshpam_env = NULL;
 227 static Authctxt *sshpam_authctxt = NULL;
 228 static const char *sshpam_password = NULL;
 229 static char badpw[] = "\b\n\r\177INCORRECT";
 230
 231 /* Some PAM implementations don't implement this */
 232 #ifndef HAVE_PAM_GETENVLIST
 233 static char **
 234 pam_getenvlist(pam_handle_t *pamh)
 235 {
 236         /*
 237          * XXX - If necessary, we can still support envrionment passing
 238          * for platforms without pam_getenvlist by searching for known
 239          * env vars (e.g. KRB5CCNAME) from the PAM environment.
 240          */
 241          return NULL;
 242 }
 243 #endif
 244
 245 /*
 246  * Some platforms, notably Solaris, do not enforce password complexity
 247  * rules during pam_chauthtok() if the real uid of the calling process
 248  * is 0, on the assumption that it's being called by "passwd" run by root.
 249  * This wraps pam_chauthtok and sets/restore the real uid so PAM will do
 250  * the right thing.
 251  */
 252 #ifdef SSHPAM_CHAUTHTOK_NEEDS_RUID
 253 static int
 254 sshpam_chauthtok_ruid(pam_handle_t *pamh, int flags)
 255 {
 256         int result;
 257
 258         if (sshpam_authctxt == NULL)
 259                 fatal("PAM: sshpam_authctxt not initialized");
 260         if (setreuid(sshpam_authctxt->pw->pw_uid, -1) == -1)
 261                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 262         result = pam_chauthtok(pamh, flags);
 263         if (setreuid(0, -1) == -1)
 264                 fatal("%s: setreuid failed: %s", __func__, strerror(errno));
 265         return result;
 266 }
 267 # define pam_chauthtok(a,b)     (sshpam_chauthtok_ruid((a), (b)))
 268 #endif
 269
 270 void
 271 sshpam_password_change_required(int reqd)
 272 {
 273         debug3("%s %d", __func__, reqd);
 274         if (sshpam_authctxt == NULL)
 275                 fatal("%s: PAM authctxt not initialized", __func__);
 276         sshpam_authctxt->force_pwchange = reqd;
 277         if (reqd) {
 278                 no_port_forwarding_flag |= 2;
 279                 no_agent_forwarding_flag |= 2;
 280                 no_x11_forwarding_flag |= 2;
 281         } else {
 282                 no_port_forwarding_flag &= ~2;
 283                 no_agent_forwarding_flag &= ~2;
 284                 no_x11_forwarding_flag &= ~2;
 285         }
 286 }
 287
 288 /* Import regular and PAM environment from subprocess */
 289 static void
 290 import_environments(Buffer *b)
 291 {
 292         char *env;
 293         u_int i, num_env;
 294         int err;
 295
 296         debug3("PAM: %s entering", __func__);
 297
 298 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 299         /* Import variables set by do_pam_account */
 300         sshpam_account_status = buffer_get_int(b);
 301         sshpam_password_change_required(buffer_get_int(b));
 302
 303         /* Import environment from subprocess */
 304         num_env = buffer_get_int(b);
 305         if (num_env > 1024)
 306                 fatal("%s: received %u environment variables, expected <= 1024",
 307                     __func__, num_env);
 308         sshpam_env = xcalloc(num_env + 1, sizeof(*sshpam_env));
 309         debug3("PAM: num env strings %d", num_env);
 310         for(i = 0; i < num_env; i++)
 311                 sshpam_env[i] = buffer_get_string(b, NULL);
 312
 313         sshpam_env[num_env] = NULL;
 314
 315         /* Import PAM environment from subprocess */
 316         num_env = buffer_get_int(b);
 317         debug("PAM: num PAM env strings %d", num_env);
 318         for(i = 0; i < num_env; i++) {
 319                 env = buffer_get_string(b, NULL);
 320
 321 #ifdef HAVE_PAM_PUTENV
 322                 /* Errors are not fatal here */
 323                 if ((err = pam_putenv(sshpam_handle, env)) != PAM_SUCCESS) {
 324                         error("PAM: pam_putenv: %s",
 325                             pam_strerror(sshpam_handle, sshpam_err));
 326                 }
 327 #endif
 328         }
 329 #endif
 330 }
 331
 332 /*
 333  * Conversation function for authentication thread.
 334  */
 335 static int
 336 sshpam_thread_conv(int n, sshpam_const struct pam_message **msg,
 337     struct pam_response **resp, void *data)
 338 {
 339         Buffer buffer;
 340         struct pam_ctxt *ctxt;
 341         struct pam_response *reply;
 342         int i;
 343
 344         debug3("PAM: %s entering, %d messages", __func__, n);
 345         *resp = NULL;
 346
 347         if (data == NULL) {
 348                 error("PAM: conversation function passed a null context");
 349                 return (PAM_CONV_ERR);
 350         }
 351         ctxt = data;
 352         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 353                 return (PAM_CONV_ERR);
 354
 355         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 356                 return (PAM_CONV_ERR);
 357
 358         buffer_init(&buffer);
 359         for (i = 0; i < n; ++i) {
 360                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 361                 case PAM_PROMPT_ECHO_OFF:
 362                         buffer_put_cstring(&buffer,
 363                             PAM_MSG_MEMBER(msg, i, msg));
 364                         if (ssh_msg_send(ctxt->pam_csock,
 365                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 366                                 goto fail;
 367                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 368                                 goto fail;
 369                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 370                                 goto fail;
 371                         reply[i].resp = buffer_get_string(&buffer, NULL);
 372                         break;
 373                 case PAM_PROMPT_ECHO_ON:
 374                         buffer_put_cstring(&buffer,
 375                             PAM_MSG_MEMBER(msg, i, msg));
 376                         if (ssh_msg_send(ctxt->pam_csock,
 377                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 378                                 goto fail;
 379                         if (ssh_msg_recv(ctxt->pam_csock, &buffer) == -1)
 380                                 goto fail;
 381                         if (buffer_get_char(&buffer) != PAM_AUTHTOK)
 382                                 goto fail;
 383                         reply[i].resp = buffer_get_string(&buffer, NULL);
 384                         break;
 385                 case PAM_ERROR_MSG:
 386                         buffer_put_cstring(&buffer,
 387                             PAM_MSG_MEMBER(msg, i, msg));
 388                         if (ssh_msg_send(ctxt->pam_csock,
 389                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 390                                 goto fail;
 391                         break;
 392                 case PAM_TEXT_INFO:
 393                         buffer_put_cstring(&buffer,
 394                             PAM_MSG_MEMBER(msg, i, msg));
 395                         if (ssh_msg_send(ctxt->pam_csock,
 396                             PAM_MSG_MEMBER(msg, i, msg_style), &buffer) == -1)
 397                                 goto fail;
 398                         break;
 399                 default:
 400                         goto fail;
 401                 }
 402                 buffer_clear(&buffer);
 403         }
 404         buffer_free(&buffer);
 405         *resp = reply;
 406         return (PAM_SUCCESS);
 407
 408  fail:
 409         for(i = 0; i < n; i++) {
 410                 if (reply[i].resp != NULL)
 411                         xfree(reply[i].resp);
 412         }
 413         xfree(reply);
 414         buffer_free(&buffer);
 415         return (PAM_CONV_ERR);
 416 }
 417
 418 /*
 419  * Authentication thread.
 420  */
 421 static void *
 422 sshpam_thread(void *ctxtp)
 423 {
 424         struct pam_ctxt *ctxt = ctxtp;
 425         Buffer buffer;
 426         struct pam_conv sshpam_conv;
 427         int flags = (options.permit_empty_passwd == 0 ?
 428             PAM_DISALLOW_NULL_AUTHTOK : 0);
 429 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 430         extern char **environ;
 431         char **env_from_pam;
 432         u_int i;
 433         const char *pam_user;
 434         const char **ptr_pam_user = &pam_user;
 435
 436         pam_get_item(sshpam_handle, PAM_USER,
 437             (sshpam_const void **)ptr_pam_user);
 438         environ[0] = NULL;
 439
 440         if (sshpam_authctxt != NULL) {
 441                 setproctitle("%s [pam]",
 442                     sshpam_authctxt->valid ? pam_user : "unknown");
 443         }
 444 #endif
 445
 446         sshpam_conv.conv = sshpam_thread_conv;
 447         sshpam_conv.appdata_ptr = ctxt;
 448
 449         if (sshpam_authctxt == NULL)
 450                 fatal("%s: PAM authctxt not initialized", __func__);
 451
 452         buffer_init(&buffer);
 453         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 454             (const void *)&sshpam_conv);
 455         if (sshpam_err != PAM_SUCCESS)
 456                 goto auth_fail;
 457         sshpam_err = pam_authenticate(sshpam_handle, flags);
 458         if (sshpam_err != PAM_SUCCESS)
 459                 goto auth_fail;
 460
 461         if (compat20) {
 462                 if (!do_pam_account()) {
 463                         sshpam_err = PAM_ACCT_EXPIRED;
 464                         goto auth_fail;
 465                 }
 466                 if (sshpam_authctxt->force_pwchange) {
 467                         sshpam_err = pam_chauthtok(sshpam_handle,
 468                             PAM_CHANGE_EXPIRED_AUTHTOK);
 469                         if (sshpam_err != PAM_SUCCESS)
 470                                 goto auth_fail;
 471                         sshpam_password_change_required(0);
 472                 }
 473         }
 474
 475         buffer_put_cstring(&buffer, "OK");
 476
 477 #ifndef UNSUPPORTED_POSIX_THREADS_HACK
 478         /* Export variables set by do_pam_account */
 479         buffer_put_int(&buffer, sshpam_account_status);
 480         buffer_put_int(&buffer, sshpam_authctxt->force_pwchange);
 481
 482         /* Export any environment strings set in child */
 483         for(i = 0; environ[i] != NULL; i++)
 484                 ; /* Count */
 485         buffer_put_int(&buffer, i);
 486         for(i = 0; environ[i] != NULL; i++)
 487                 buffer_put_cstring(&buffer, environ[i]);
 488
 489         /* Export any environment strings set by PAM in child */
 490         env_from_pam = pam_getenvlist(sshpam_handle);
 491         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 492                 ; /* Count */
 493         buffer_put_int(&buffer, i);
 494         for(i = 0; env_from_pam != NULL && env_from_pam[i] != NULL; i++)
 495                 buffer_put_cstring(&buffer, env_from_pam[i]);
 496 #endif /* UNSUPPORTED_POSIX_THREADS_HACK */
 497
 498         /* XXX - can't do much about an error here */
 499         ssh_msg_send(ctxt->pam_csock, sshpam_err, &buffer);
 500         buffer_free(&buffer);
 501         pthread_exit(NULL);
 502
 503  auth_fail:
 504         buffer_put_cstring(&buffer,
 505             pam_strerror(sshpam_handle, sshpam_err));
 506         /* XXX - can't do much about an error here */
 507         if (sshpam_err == PAM_ACCT_EXPIRED)
 508                 ssh_msg_send(ctxt->pam_csock, PAM_ACCT_EXPIRED, &buffer);
 509         else
 510                 ssh_msg_send(ctxt->pam_csock, PAM_AUTH_ERR, &buffer);
 511         buffer_free(&buffer);
 512         pthread_exit(NULL);
 513
 514         return (NULL); /* Avoid warning for non-pthread case */
 515 }
 516
 517 void
 518 sshpam_thread_cleanup(void)
 519 {
 520         struct pam_ctxt *ctxt = cleanup_ctxt;
 521
 522         debug3("PAM: %s entering", __func__);
 523         if (ctxt != NULL && ctxt->pam_thread != 0) {
 524                 pthread_cancel(ctxt->pam_thread);
 525                 pthread_join(ctxt->pam_thread, NULL);
 526                 close(ctxt->pam_psock);
 527                 close(ctxt->pam_csock);
 528                 memset(ctxt, 0, sizeof(*ctxt));
 529                 cleanup_ctxt = NULL;
 530         }
 531 }
 532
 533 static int
 534 sshpam_null_conv(int n, sshpam_const struct pam_message **msg,
 535     struct pam_response **resp, void *data)
 536 {
 537         debug3("PAM: %s entering, %d messages", __func__, n);
 538         return (PAM_CONV_ERR);
 539 }
 540
 541 static struct pam_conv null_conv = { sshpam_null_conv, NULL };
 542
 543 static int
 544 sshpam_store_conv(int n, sshpam_const struct pam_message **msg,
 545     struct pam_response **resp, void *data)
 546 {
 547         struct pam_response *reply;
 548         int i;
 549         size_t len;
 550
 551         debug3("PAM: %s called with %d messages", __func__, n);
 552         *resp = NULL;
 553
 554         if (n <= 0 || n > PAM_MAX_NUM_MSG)
 555                 return (PAM_CONV_ERR);
 556
 557         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 558                 return (PAM_CONV_ERR);
 559
 560         for (i = 0; i < n; ++i) {
 561                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 562                 case PAM_ERROR_MSG:
 563                 case PAM_TEXT_INFO:
 564                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
 565                         buffer_append(&loginmsg, PAM_MSG_MEMBER(msg, i, msg), len);
 566                         buffer_append(&loginmsg, "\n", 1 );
 567                         reply[i].resp_retcode = PAM_SUCCESS;
 568                         break;
 569                 default:
 570                         goto fail;
 571                 }
 572         }
 573         *resp = reply;
 574         return (PAM_SUCCESS);
 575
 576  fail:
 577         for(i = 0; i < n; i++) {
 578                 if (reply[i].resp != NULL)
 579                         xfree(reply[i].resp);
 580         }
 581         xfree(reply);
 582         return (PAM_CONV_ERR);
 583 }
 584
 585 static struct pam_conv store_conv = { sshpam_store_conv, NULL };
 586
 587 void
 588 sshpam_cleanup(void)
 589 {
 590         debug("PAM: cleanup");
 591         if (sshpam_handle == NULL)
 592                 return;
 593         pam_set_item(sshpam_handle, PAM_CONV, (const void *)&null_conv);
 594         if (sshpam_cred_established) {
 595                 pam_setcred(sshpam_handle, PAM_DELETE_CRED);
 596                 sshpam_cred_established = 0;
 597         }
 598         if (sshpam_session_open) {
 599                 pam_close_session(sshpam_handle, PAM_SILENT);
 600                 sshpam_session_open = 0;
 601         }
 602         sshpam_authenticated = 0;
 603         pam_end(sshpam_handle, sshpam_err);
 604         sshpam_handle = NULL;
 605 }
 606
 607 static int
 608 sshpam_init(Authctxt *authctxt)
 609 {
 610         extern char *__progname;
 611         const char *pam_rhost, *pam_user, *user = authctxt->user;
 612         const char **ptr_pam_user = &pam_user;
 613
 614         if (sshpam_handle != NULL) {
 615                 /* We already have a PAM context; check if the user matches */
 616                 sshpam_err = pam_get_item(sshpam_handle,
 617                     PAM_USER, (sshpam_const void **)ptr_pam_user);
 618                 if (sshpam_err == PAM_SUCCESS && strcmp(user, pam_user) == 0)
 619                         return (0);
 620                 pam_end(sshpam_handle, sshpam_err);
 621                 sshpam_handle = NULL;
 622         }
 623         debug("PAM: initializing for \"%s\"", user);
 624         sshpam_err =
 625             pam_start(SSHD_PAM_SERVICE, user, &store_conv, &sshpam_handle);
 626         sshpam_authctxt = authctxt;
 627
 628         if (sshpam_err != PAM_SUCCESS) {
 629                 pam_end(sshpam_handle, sshpam_err);
 630                 sshpam_handle = NULL;
 631                 return (-1);
 632         }
 633         pam_rhost = get_remote_name_or_ip(utmp_len, options.use_dns);
 634         debug("PAM: setting PAM_RHOST to \"%s\"", pam_rhost);
 635         sshpam_err = pam_set_item(sshpam_handle, PAM_RHOST, pam_rhost);
 636         if (sshpam_err != PAM_SUCCESS) {
 637                 pam_end(sshpam_handle, sshpam_err);
 638                 sshpam_handle = NULL;
 639                 return (-1);
 640         }
 641 #ifdef PAM_TTY_KLUDGE
 642         /*
 643          * Some silly PAM modules (e.g. pam_time) require a TTY to operate.
 644          * sshd doesn't set the tty until too late in the auth process and
 645          * may not even set one (for tty-less connections)
 646          */
 647         debug("PAM: setting PAM_TTY to \"ssh\"");
 648         sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, "ssh");
 649         if (sshpam_err != PAM_SUCCESS) {
 650                 pam_end(sshpam_handle, sshpam_err);
 651                 sshpam_handle = NULL;
 652                 return (-1);
 653         }
 654 #endif
 655         return (0);
 656 }
 657
 658 static void *
 659 sshpam_init_ctx(Authctxt *authctxt)
 660 {
 661         struct pam_ctxt *ctxt;
 662         int socks[2];
 663
 664         debug3("PAM: %s entering", __func__);
 665         /*
 666          * Refuse to start if we don't have PAM enabled or do_pam_account
 667          * has previously failed.
 668          */
 669         if (!options.use_pam || sshpam_account_status == 0)
 670                 return NULL;
 671
 672         /* Initialize PAM */
 673         if (sshpam_init(authctxt) == -1) {
 674                 error("PAM: initialization failed");
 675                 return (NULL);
 676         }
 677
 678         ctxt = xmalloc(sizeof *ctxt);
 679         memset(ctxt, 0, sizeof(*ctxt));
 680
 681         /* Start the authentication thread */
 682         if (socketpair(AF_UNIX, SOCK_STREAM, PF_UNSPEC, socks) == -1) {
 683                 error("PAM: failed create sockets: %s", strerror(errno));
 684                 xfree(ctxt);
 685                 return (NULL);
 686         }
 687         ctxt->pam_psock = socks[0];
 688         ctxt->pam_csock = socks[1];
 689         if (pthread_create(&ctxt->pam_thread, NULL, sshpam_thread, ctxt) == -1) {
 690                 error("PAM: failed to start authentication thread: %s",
 691                     strerror(errno));
 692                 close(socks[0]);
 693                 close(socks[1]);
 694                 xfree(ctxt);
 695                 return (NULL);
 696         }
 697         cleanup_ctxt = ctxt;
 698         return (ctxt);
 699 }
 700
 701 static int
 702 sshpam_query(void *ctx, char **name, char **info,
 703     u_int *num, char ***prompts, u_int **echo_on)
 704 {
 705         Buffer buffer;
 706         struct pam_ctxt *ctxt = ctx;
 707         size_t plen;
 708         u_char type;
 709         char *msg;
 710         size_t len, mlen;
 711
 712         debug3("PAM: %s entering", __func__);
 713         buffer_init(&buffer);
 714         *name = xstrdup("");
 715         *info = xstrdup("");
 716         *prompts = xmalloc(sizeof(char *));
 717         **prompts = NULL;
 718         plen = 0;
 719         *echo_on = xmalloc(sizeof(u_int));
 720         while (ssh_msg_recv(ctxt->pam_psock, &buffer) == 0) {
 721                 type = buffer_get_char(&buffer);
 722                 msg = buffer_get_string(&buffer, NULL);
 723                 mlen = strlen(msg);
 724                 switch (type) {
 725                 case PAM_PROMPT_ECHO_ON:
 726                 case PAM_PROMPT_ECHO_OFF:
 727                         *num = 1;
 728                         len = plen + mlen + 1;
 729                         **prompts = xrealloc(**prompts, 1, len);
 730                         strlcpy(**prompts + plen, msg, len - plen);
 731                         plen += mlen;
 732                         **echo_on = (type == PAM_PROMPT_ECHO_ON);
 733                         xfree(msg);
 734                         return (0);
 735                 case PAM_ERROR_MSG:
 736                 case PAM_TEXT_INFO:
 737                         /* accumulate messages */
 738                         len = plen + mlen + 2;
 739                         **prompts = xrealloc(**prompts, 1, len);
 740                         strlcpy(**prompts + plen, msg, len - plen);
 741                         plen += mlen;
 742                         strlcat(**prompts + plen, "\n", len - plen);
 743                         plen++;
 744                         xfree(msg);
 745                         break;
 746                 case PAM_ACCT_EXPIRED:
 747                         sshpam_account_status = 0;
 748                         /* FALLTHROUGH */
 749                 case PAM_AUTH_ERR:
 750                         debug3("PAM: %s", pam_strerror(sshpam_handle, type));
 751                         if (**prompts != NULL && strlen(**prompts) != 0) {
 752                                 *info = **prompts;
 753                                 **prompts = NULL;
 754                                 *num = 0;
 755                                 **echo_on = 0;
 756                                 ctxt->pam_done = -1;
 757                                 xfree(msg);
 758                                 return 0;
 759                         }
 760                         /* FALLTHROUGH */
 761                 case PAM_SUCCESS:
 762                         if (**prompts != NULL) {
 763                                 /* drain any accumulated messages */
 764                                 debug("PAM: %s", **prompts);
 765                                 buffer_append(&loginmsg, **prompts,
 766                                     strlen(**prompts));
 767                                 xfree(**prompts);
 768                                 **prompts = NULL;
 769                         }
 770                         if (type == PAM_SUCCESS) {
 771                                 if (!sshpam_authctxt->valid ||
 772                                     (sshpam_authctxt->pw->pw_uid == 0 &&
 773                                     options.permit_root_login != PERMIT_YES))
 774                                         fatal("Internal error: PAM auth "
 775                                             "succeeded when it should have "
 776                                             "failed");
 777                                 import_environments(&buffer);
 778                                 *num = 0;
 779                                 **echo_on = 0;
 780                                 ctxt->pam_done = 1;
 781                                 xfree(msg);
 782                                 return (0);
 783                         }
 784                         error("PAM: %s for %s%.100s from %.100s", msg,
 785                             sshpam_authctxt->valid ? "" : "illegal user ",
 786                             sshpam_authctxt->user,
 787                             get_remote_name_or_ip(utmp_len, options.use_dns));
 788                         /* FALLTHROUGH */
 789                 default:
 790                         *num = 0;
 791                         **echo_on = 0;
 792                         xfree(msg);
 793                         ctxt->pam_done = -1;
 794                         return (-1);
 795                 }
 796         }
 797         return (-1);
 798 }
 799
 800 /* XXX - see also comment in auth-chall.c:verify_response */
 801 static int
 802 sshpam_respond(void *ctx, u_int num, char **resp)
 803 {
 804         Buffer buffer;
 805         struct pam_ctxt *ctxt = ctx;
 806
 807         debug2("PAM: %s entering, %u responses", __func__, num);
 808         switch (ctxt->pam_done) {
 809         case 1:
 810                 sshpam_authenticated = 1;
 811                 return (0);
 812         case 0:
 813                 break;
 814         default:
 815                 return (-1);
 816         }
 817         if (num != 1) {
 818                 error("PAM: expected one response, got %u", num);
 819                 return (-1);
 820         }
 821         buffer_init(&buffer);
 822         if (sshpam_authctxt->valid &&
 823             (sshpam_authctxt->pw->pw_uid != 0 ||
 824             options.permit_root_login == PERMIT_YES))
 825                 buffer_put_cstring(&buffer, *resp);
 826         else
 827                 buffer_put_cstring(&buffer, badpw);
 828         if (ssh_msg_send(ctxt->pam_psock, PAM_AUTHTOK, &buffer) == -1) {
 829                 buffer_free(&buffer);
 830                 return (-1);
 831         }
 832         buffer_free(&buffer);
 833         return (1);
 834 }
 835
 836 static void
 837 sshpam_free_ctx(void *ctxtp)
 838 {
 839         struct pam_ctxt *ctxt = ctxtp;
 840
 841         debug3("PAM: %s entering", __func__);
 842         sshpam_thread_cleanup();
 843         xfree(ctxt);
 844         /*
 845          * We don't call sshpam_cleanup() here because we may need the PAM
 846          * handle at a later stage, e.g. when setting up a session.  It's
 847          * still on the cleanup list, so pam_end() *will* be called before
 848          * the server process terminates.
 849          */
 850 }
 851
 852 KbdintDevice sshpam_device = {
 853         "pam",
 854         sshpam_init_ctx,
 855         sshpam_query,
 856         sshpam_respond,
 857         sshpam_free_ctx
 858 };
 859
 860 KbdintDevice mm_sshpam_device = {
 861         "pam",
 862         mm_sshpam_init_ctx,
 863         mm_sshpam_query,
 864         mm_sshpam_respond,
 865         mm_sshpam_free_ctx
 866 };
 867
 868 /*
 869  * This replaces auth-pam.c
 870  */
 871 void
 872 start_pam(Authctxt *authctxt)
 873 {
 874         if (!options.use_pam)
 875                 fatal("PAM: initialisation requested when UsePAM=no");
 876
 877         if (sshpam_init(authctxt) == -1)
 878                 fatal("PAM: initialisation failed");
 879 }
 880
 881 void
 882 finish_pam(void)
 883 {
 884         sshpam_cleanup();
 885 }
 886
 887 u_int
 888 do_pam_account(void)
 889 {
 890         debug("%s: called", __func__);
 891         if (sshpam_account_status != -1)
 892                 return (sshpam_account_status);
 893
 894         sshpam_err = pam_acct_mgmt(sshpam_handle, 0);
 895         debug3("PAM: %s pam_acct_mgmt = %d (%s)", __func__, sshpam_err,
 896             pam_strerror(sshpam_handle, sshpam_err));
 897
 898         if (sshpam_err != PAM_SUCCESS && sshpam_err != PAM_NEW_AUTHTOK_REQD) {
 899                 sshpam_account_status = 0;
 900                 return (sshpam_account_status);
 901         }
 902
 903         if (sshpam_err == PAM_NEW_AUTHTOK_REQD)
 904                 sshpam_password_change_required(1);
 905
 906         sshpam_account_status = 1;
 907         return (sshpam_account_status);
 908 }
 909
 910 void
 911 do_pam_set_tty(const char *tty)
 912 {
 913         if (tty != NULL) {
 914                 debug("PAM: setting PAM_TTY to \"%s\"", tty);
 915                 sshpam_err = pam_set_item(sshpam_handle, PAM_TTY, tty);
 916                 if (sshpam_err != PAM_SUCCESS)
 917                         fatal("PAM: failed to set PAM_TTY: %s",
 918                             pam_strerror(sshpam_handle, sshpam_err));
 919         }
 920 }
 921
 922 void
 923 do_pam_setcred(int init)
 924 {
 925         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
 926             (const void *)&store_conv);
 927         if (sshpam_err != PAM_SUCCESS)
 928                 fatal("PAM: failed to set PAM_CONV: %s",
 929                     pam_strerror(sshpam_handle, sshpam_err));
 930         if (init) {
 931                 debug("PAM: establishing credentials");
 932                 sshpam_err = pam_setcred(sshpam_handle, PAM_ESTABLISH_CRED);
 933         } else {
 934                 debug("PAM: reinitializing credentials");
 935                 sshpam_err = pam_setcred(sshpam_handle, PAM_REINITIALIZE_CRED);
 936         }
 937         if (sshpam_err == PAM_SUCCESS) {
 938                 sshpam_cred_established = 1;
 939                 return;
 940         }
 941         if (sshpam_authenticated)
 942                 fatal("PAM: pam_setcred(): %s",
 943                     pam_strerror(sshpam_handle, sshpam_err));
 944         else
 945                 debug("PAM: pam_setcred(): %s",
 946                     pam_strerror(sshpam_handle, sshpam_err));
 947 }
 948
 949 static int
 950 sshpam_tty_conv(int n, sshpam_const struct pam_message **msg,
 951     struct pam_response **resp, void *data)
 952 {
 953         char input[PAM_MAX_MSG_SIZE];
 954         struct pam_response *reply;
 955         int i;
 956
 957         debug3("PAM: %s called with %d messages", __func__, n);
 958
 959         *resp = NULL;
 960
 961         if (n <= 0 || n > PAM_MAX_NUM_MSG || !isatty(STDIN_FILENO))
 962                 return (PAM_CONV_ERR);
 963
 964         if ((reply = calloc(n, sizeof(*reply))) == NULL)
 965                 return (PAM_CONV_ERR);
 966
 967         for (i = 0; i < n; ++i) {
 968                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
 969                 case PAM_PROMPT_ECHO_OFF:
 970                         reply[i].resp =
 971                             read_passphrase(PAM_MSG_MEMBER(msg, i, msg),
 972                             RP_ALLOW_STDIN);
 973                         reply[i].resp_retcode = PAM_SUCCESS;
 974                         break;
 975                 case PAM_PROMPT_ECHO_ON:
 976                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 977                         fgets(input, sizeof input, stdin);
 978                         if ((reply[i].resp = strdup(input)) == NULL)
 979                                 goto fail;
 980                         reply[i].resp_retcode = PAM_SUCCESS;
 981                         break;
 982                 case PAM_ERROR_MSG:
 983                 case PAM_TEXT_INFO:
 984                         fprintf(stderr, "%s\n", PAM_MSG_MEMBER(msg, i, msg));
 985                         reply[i].resp_retcode = PAM_SUCCESS;
 986                         break;
 987                 default:
 988                         goto fail;
 989                 }
 990         }
 991         *resp = reply;
 992         return (PAM_SUCCESS);
 993
 994  fail:
 995         for(i = 0; i < n; i++) {
 996                 if (reply[i].resp != NULL)
 997                         xfree(reply[i].resp);
 998         }
 999         xfree(reply);
1000         return (PAM_CONV_ERR);
1001 }
1002
1003 static struct pam_conv tty_conv = { sshpam_tty_conv, NULL };
1004
1005 /*
1006  * XXX this should be done in the authentication phase, but ssh1 doesn't
1007  * support that
1008  */
1009 void
1010 do_pam_chauthtok(void)
1011 {
1012         if (use_privsep)
1013                 fatal("Password expired (unable to change with privsep)");
1014         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1015             (const void *)&tty_conv);
1016         if (sshpam_err != PAM_SUCCESS)
1017                 fatal("PAM: failed to set PAM_CONV: %s",
1018                     pam_strerror(sshpam_handle, sshpam_err));
1019         debug("PAM: changing password");
1020         sshpam_err = pam_chauthtok(sshpam_handle, PAM_CHANGE_EXPIRED_AUTHTOK);
1021         if (sshpam_err != PAM_SUCCESS)
1022                 fatal("PAM: pam_chauthtok(): %s",
1023                     pam_strerror(sshpam_handle, sshpam_err));
1024 }
1025
1026 void
1027 do_pam_session(void)
1028 {
1029         debug3("PAM: opening session");
1030         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1031             (const void *)&store_conv);
1032         if (sshpam_err != PAM_SUCCESS)
1033                 fatal("PAM: failed to set PAM_CONV: %s",
1034                     pam_strerror(sshpam_handle, sshpam_err));
1035         sshpam_err = pam_open_session(sshpam_handle, 0);
1036         if (sshpam_err == PAM_SUCCESS)
1037                 sshpam_session_open = 1;
1038         else {
1039                 sshpam_session_open = 0;
1040                 disable_forwarding();
1041                 error("PAM: pam_open_session(): %s",
1042                     pam_strerror(sshpam_handle, sshpam_err));
1043         }
1044
1045 }
1046
1047 int
1048 is_pam_session_open(void)
1049 {
1050         return sshpam_session_open;
1051 }
1052
1053 /*
1054  * Set a PAM environment string. We need to do this so that the session
1055  * modules can handle things like Kerberos/GSI credentials that appear
1056  * during the ssh authentication process.
1057  */
1058 int
1059 do_pam_putenv(char *name, char *value)
1060 {
1061         int ret = 1;
1062 #ifdef HAVE_PAM_PUTENV
1063         char *compound;
1064         size_t len;
1065
1066         len = strlen(name) + strlen(value) + 2;
1067         compound = xmalloc(len);
1068
1069         snprintf(compound, len, "%s=%s", name, value);
1070         ret = pam_putenv(sshpam_handle, compound);
1071         xfree(compound);
1072 #endif
1073
1074         return (ret);
1075 }
1076
1077 char **
1078 fetch_pam_child_environment(void)
1079 {
1080         return sshpam_env;
1081 }
1082
1083 char **
1084 fetch_pam_environment(void)
1085 {
1086         return (pam_getenvlist(sshpam_handle));
1087 }
1088
1089 void
1090 free_pam_environment(char **env)
1091 {
1092         char **envp;
1093
1094         if (env == NULL)
1095                 return;
1096
1097         for (envp = env; *envp; envp++)
1098                 xfree(*envp);
1099         xfree(env);
1100 }
1101
1102 /*
1103  * "Blind" conversation function for password authentication.  Assumes that
1104  * echo-off prompts are for the password and stores messages for later
1105  * display.
1106  */
1107 static int
1108 sshpam_passwd_conv(int n, sshpam_const struct pam_message **msg,
1109     struct pam_response **resp, void *data)
1110 {
1111         struct pam_response *reply;
1112         int i;
1113         size_t len;
1114
1115         debug3("PAM: %s called with %d messages", __func__, n);
1116
1117         *resp = NULL;
1118
1119         if (n <= 0 || n > PAM_MAX_NUM_MSG)
1120                 return (PAM_CONV_ERR);
1121
1122         if ((reply = malloc(n * sizeof(*reply))) == NULL)
1123                 return (PAM_CONV_ERR);
1124         memset(reply, 0, n * sizeof(*reply));
1125
1126         for (i = 0; i < n; ++i) {
1127                 switch (PAM_MSG_MEMBER(msg, i, msg_style)) {
1128                 case PAM_PROMPT_ECHO_OFF:
1129                         if (sshpam_password == NULL)
1130                                 goto fail;
1131                         if ((reply[i].resp = strdup(sshpam_password)) == NULL)
1132                                 goto fail;
1133                         reply[i].resp_retcode = PAM_SUCCESS;
1134                         break;
1135                 case PAM_ERROR_MSG:
1136                 case PAM_TEXT_INFO:
1137                         len = strlen(PAM_MSG_MEMBER(msg, i, msg));
1138                         if (len > 0) {
1139                                 buffer_append(&loginmsg,
1140                                     PAM_MSG_MEMBER(msg, i, msg), len);
1141                                 buffer_append(&loginmsg, "\n", 1);
1142                         }
1143                         if ((reply[i].resp = strdup("")) == NULL)
1144                                 goto fail;
1145                         reply[i].resp_retcode = PAM_SUCCESS;
1146                         break;
1147                 default:
1148                         goto fail;
1149                 }
1150         }
1151         *resp = reply;
1152         return (PAM_SUCCESS);
1153
1154  fail:
1155         for(i = 0; i < n; i++) {
1156                 if (reply[i].resp != NULL)
1157                         xfree(reply[i].resp);
1158         }
1159         xfree(reply);
1160         return (PAM_CONV_ERR);
1161 }
1162
1163 static struct pam_conv passwd_conv = { sshpam_passwd_conv, NULL };
1164
1165 /*
1166  * Attempt password authentication via PAM
1167  */
1168 int
1169 sshpam_auth_passwd(Authctxt *authctxt, const char *password)
1170 {
1171         int flags = (options.permit_empty_passwd == 0 ?
1172             PAM_DISALLOW_NULL_AUTHTOK : 0);
1173
1174         if (!options.use_pam || sshpam_handle == NULL)
1175                 fatal("PAM: %s called when PAM disabled or failed to "
1176                     "initialise.", __func__);
1177
1178         sshpam_password = password;
1179         sshpam_authctxt = authctxt;
1180
1181         /*
1182          * If the user logging in is invalid, or is root but is not permitted
1183          * by PermitRootLogin, use an invalid password to prevent leaking
1184          * information via timing (eg if the PAM config has a delay on fail).
1185          */
1186         if (!authctxt->valid || (authctxt->pw->pw_uid == 0 &&
1187             options.permit_root_login != PERMIT_YES))
1188                 sshpam_password = badpw;
1189
1190         sshpam_err = pam_set_item(sshpam_handle, PAM_CONV,
1191             (const void *)&passwd_conv);
1192         if (sshpam_err != PAM_SUCCESS)
1193                 fatal("PAM: %s: failed to set PAM_CONV: %s", __func__,
1194                     pam_strerror(sshpam_handle, sshpam_err));
1195
1196         sshpam_err = pam_authenticate(sshpam_handle, flags);
1197         sshpam_password = NULL;
1198         if (sshpam_err == PAM_SUCCESS && authctxt->valid) {
1199                 debug("PAM: password authentication accepted for %.100s",
1200                     authctxt->user);
1201                 return 1;
1202         } else {
1203                 debug("PAM: password authentication failed for %.100s: %s",
1204                     authctxt->valid ? authctxt->user : "an illegal user",
1205                     pam_strerror(sshpam_handle, sshpam_err));
1206                 return 0;
1207         }
1208 }
1209 #endif /* USE_PAM */