312 lines
7.6 KiB
C
312 lines
7.6 KiB
C
/*
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* X server wrapper.
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*
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* This wrapper makes some sanity checks on the command line arguments
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* and environment variables when run with euid == 0 && euid != uid.
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* If the checks fail, the wrapper exits with a message.
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* If they succeed, it exec's the Xserver.
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*/
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/*
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* Copyright (c) 1998 by The XFree86 Project, Inc. All Rights Reserved.
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject
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* to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included
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* in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE XFREE86 PROJECT BE LIABLE FOR ANY CLAIM, DAMAGES
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* OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
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* ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
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* OR OTHER DEALINGS IN THE SOFTWARE.
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*
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* Except as contained in this notice, the name of the XFree86 Project
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* shall not be used in advertising or otherwise to promote the sale,
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* use or other dealings in this Software without prior written
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* authorization from the XFree86 Project.
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*/
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/* $XFree86: xc/programs/Xserver/os/wrapper.c,v 1.1.2.9 1999/07/29 09:23:02 hohndel Exp $ */
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/* This is normally set in the Imakefile */
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#ifndef XSERVER_PATH
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#define XSERVER_PATH "/usr/X11R6/bin/XFree86"
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#endif
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <unistd.h>
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#include <sys/types.h>
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#ifdef USE_PAM
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#include <security/pam_appl.h>
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#include <security/pam_misc.h>
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#include <pwd.h>
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#endif /* USE_PAM */
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/* Neither of these should be required for XFree86 3.3.2 */
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#ifndef REJECT_CONFIG
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#define REJECT_CONFIG 0
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#endif
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#ifndef REJECT_XKBDIR
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#define REJECT_XKBDIR 0
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#endif
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/* Consider LD* variables insecure ? */
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#ifndef REMOVE_ENV_LD
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#define REMOVE_ENV_LD 1
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#endif
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/* Remove long environment variables? */
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#ifndef REMOVE_LONG_ENV
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#define REMOVE_LONG_ENV 1
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#endif
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/* Check args and env only if running setuid (euid == 0 && euid != uid) ? */
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#ifndef CHECK_EUID
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#define CHECK_EUID 1
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#endif
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/*
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* Maybe the locale can be faked to make isprint(3) report that everything
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* is printable? Avoid it by default.
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*/
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#ifndef USE_ISPRINT
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#define USE_ISPRINT 0
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#endif
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#define MAX_ARG_LENGTH 128
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#define MAX_ENV_LENGTH 256
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#define MAX_ENV_PATH_LENGTH 2048
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#if USE_ISPRINT
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#include <ctype.h>
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#define checkPrintable(c) isprint(c)
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#else
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#define checkPrintable(c) (((c) & 0x7f) >= 0x20 && ((c) & 0x7f) != 0x7f)
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#endif
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enum BadCode {
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NotBad = 0,
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UnsafeArg,
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ArgTooLong,
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UnprintableArg,
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EnvTooLong,
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InternalError
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#ifdef USE_PAM
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,PamFailed,
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PamAuthFailed
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#endif /* USE_PAM */
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};
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#define ARGMSG \
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"\nIf the arguments used are valid, and have been rejected incorrectly\n" \
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"please send details of the arguments and why they are valid to\n" \
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"XFree86@XFree86.org. In the meantime, you can start the Xserver as\n" \
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"the \"super user\" (root).\n"
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#define ENVMSG \
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"\nIf the environment is valid, and have been rejected incorrectly\n" \
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"please send details of the environment and why it is valid to\n" \
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"XFree86@XFree86.org. In the meantime, you can start the Xserver as\n" \
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"the \"super user\" (root).\n"
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#ifdef USE_PAM
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static struct pam_conv conv = {
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misc_conv,
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NULL
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};
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#endif /* USE_PAM */
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int
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main(int argc, char **argv, char **envp)
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{
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enum BadCode bad = NotBad;
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int i, j;
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char *a, *e;
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#if defined(__QNX__) && !defined(__QNXNTO__)
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char cmd_name[64];
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#endif
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#ifdef USE_PAM
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pam_handle_t *pamh = NULL;
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struct passwd *pw;
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int retval;
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pw = getpwuid(getuid());
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if (pw == NULL) {
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bad = InternalError;
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}
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if (!bad) {
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retval = pam_start("xserver", pw->pw_name, &conv, &pamh);
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if (retval != PAM_SUCCESS)
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bad = PamFailed;
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}
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if (!bad) {
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retval = pam_authenticate(pamh, 0);
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if (retval != PAM_SUCCESS) {
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pam_end(pamh, retval);
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bad = PamAuthFailed;
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}
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}
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if (!bad) {
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retval = pam_acct_mgmt(pamh, 0);
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if (retval != PAM_SUCCESS) {
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pam_end(pamh, retval);
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bad = PamAuthFailed;
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}
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}
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/* this is not a session, so do not do session management */
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if (!bad) pam_end(pamh, PAM_SUCCESS);
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#endif /* USE_PAM */
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#if CHECK_EUID
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if (!bad && geteuid() == 0 && getuid() != geteuid()) {
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#else
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if (!bad) {
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#endif
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/* Check each argv[] */
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for (i = 1; i < argc; i++) {
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/* Check for known bad arguments */
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#if REJECT_CONFIG
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if (strcmp(argv[i], "-config") == 0) {
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bad = UnsafeArg;
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break;
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}
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#endif
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#if REJECT_XKBDIR
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if (strcmp(argv[i], "-xkbdir") == 0) {
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bad = UnsafeArg;
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break;
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}
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#endif
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if (strlen(argv[i]) > MAX_ARG_LENGTH) {
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bad = ArgTooLong;
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break;
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}
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a = argv[i];
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while (*a) {
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if (checkPrintable(*a) == 0) {
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bad = UnprintableArg;
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break;
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}
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a++;
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}
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if (bad)
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break;
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}
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/* Check each envp[] */
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if (!bad)
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for (i = 0; envp[i]; i++) {
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/* Check for bad environment variables and values */
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#if REMOVE_ENV_LD
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while (envp[i] && (strncmp(envp[i], "LD", 2) == 0)) {
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for (j = i; envp[j]; j++) {
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envp[j] = envp[j+1];
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}
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}
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#endif
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if (envp[i] && (strlen(envp[i]) > MAX_ENV_LENGTH)) {
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#if REMOVE_LONG_ENV
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for (j = i; envp[j]; j++) {
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envp[j] = envp[j+1];
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}
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i--;
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#else
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char *eq;
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int len;
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eq = strchr(envp[i], '=');
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if (!eq)
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continue;
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len = eq - envp[i];
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e = malloc(len + 1);
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if (!e) {
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bad = InternalError;
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break;
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}
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strncpy(e, envp[i], len);
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e[len] = 0;
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if (len >= 4 &&
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(strcmp(e + len - 4, "PATH") == 0 ||
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strcmp(e, "TERMCAP") == 0)) {
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if (strlen(envp[i]) > MAX_ENV_PATH_LENGTH) {
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bad = EnvTooLong;
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break;
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} else {
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free(e);
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}
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} else {
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bad = EnvTooLong;
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break;
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}
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#endif
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}
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}
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}
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switch (bad) {
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case NotBad:
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argv[0] = XSERVER_PATH;
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#if defined(__QNX__) && !defined(__QNXNTO__)
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sprintf(cmd_name,"%s.%d",XSERVER_PATH,getnid());
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execve(cmd_name, argv, envp);
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#else
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execve(XSERVER_PATH, argv, envp);
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#endif
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fprintf(stderr, "execve failed for %s (errno %d)\n", XSERVER_PATH,
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errno);
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break;
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case UnsafeArg:
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fprintf(stderr, "Command line argument number %d is unsafe\n", i);
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fprintf(stderr, ARGMSG);
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break;
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case ArgTooLong:
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fprintf(stderr, "Command line argument number %d is too long\n", i);
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fprintf(stderr, ARGMSG);
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break;
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case UnprintableArg:
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fprintf(stderr, "Command line argument number %d contains unprintable"
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" characters\n", i);
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fprintf(stderr, ARGMSG);
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break;
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case EnvTooLong:
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fprintf(stderr, "Environment variable `%s' is too long\n", e);
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fprintf(stderr, ENVMSG);
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break;
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case InternalError:
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fprintf(stderr, "Internal Error\n");
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break;
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#ifdef USE_PAM
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case PamFailed:
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fprintf(stderr, "Authentication System Failure, "
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"missing or mangled PAM configuration file or module?\n");
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break;
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case PamAuthFailed:
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fprintf(stderr, "Authentication failed - cannot start X server.\nPerhaps you do not have console ownership?");
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break;
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#endif
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default:
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fprintf(stderr, "Unknown error\n");
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fprintf(stderr, ARGMSG);
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fprintf(stderr, ENVMSG);
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break;
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}
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exit(1);
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}
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