dslinux/user/autologin README autologin.c config.h

[amadeus]

Update of /cvsroot/dslinux/dslinux/user/autologin
In directory antilope:/tmp/cvs-serv5942

Added Files:
	README autologin.c config.h 
Log Message:
adding pristine copy of autologin to HEAD so I can branch from it

--- NEW FILE: config.h ---
/* config.h.in.  Generated automatically from configure.in by autoheader.  */

/* Define HAVE_PAM if you, well, have PAM. */
#undef HAVE_PAM

/* Define if you have the setegid function.  */
#undef HAVE_SETEGID

/* Define if you have the seteuid function.  */
#undef HAVE_SETEUID

/* Define if you have the setgid function.  */
#undef HAVE_SETGID

/* Define if you have the setregid function.  */
#undef HAVE_SETREGID

/* Define if you have the setreuid function.  */
#undef HAVE_SETREUID

/* Define if you have the setuid function.  */
#undef HAVE_SETUID

/* Define if you have the dl library (-ldl).  */
#undef HAVE_LIBDL

/* Name of package */
#undef PACKAGE

/* Version number of package */
#undef VERSION

/* be paranoid */
#undef PARANOID


--- NEW FILE: README ---
Autologin 0.99.0
================
(c) 2000 Red Hat, Inc.
Written by Bernhard Rosenkraenzer <bero at redhat.com>


What is it?
===========
Autologin is a tool that lets you bypass the login screens on a unix system.
It needs to be installed and configured by root (it is definitely not a
cracking tool ;) ).
Possible uses include providing a simple end-user system as well as creating
a one-purpose (e.g. web browsing) station that returns to where it's supposed
to be after a reboot or power outage without any intervention.

autologin affects only local users - it doesn't open up any leaks for crackers
from the outside world.


How is it configured?
=====================
Create the file /etc/sysconfig/autologin, containing the following settings:

USER=[username]
	Start the session as the user specified here.
	This setting is mandatory. If omitted, autologin will not run.
	If autologin was compiled with --enable-paranoid, autologin will
	not run if the user specified has UID or GID 0.
EXEC=[script or program]
	The script or program listed here will be executed as the user
	specified above.
	If this setting is omitted, /usr/X11R6/bin/startx will be used.
AUTOLOGIN={yes,no}
	You can use this setting to turn off autologin even if it is
	installed and the config file exists and is considered safe.
	If this setting is omitted, "yes" is assumed.

/etc/sysconfig/autologin must not be writable by anyone but root. If it is,
it is detected as a possible cracking attempt and autologin will not run.


Do I need to do anything else?
==============================
Yes - you need to have runlevel 5 start autologin. Starting from the
initscripts 5.15 package, Red Hat Linux does this for you.
If you are running a prior version or a different OS, simply replace
the call to kdm, gdm or xdm with a call to autologin, or better yet, to
a script that calls autologin and falls back to [kgx]dm if autologin fails.


Is it safe?
===========
I think so. Read the source to make sure.


Patches etc
===========
Send patches, comments, suggestions, big CPUs, money etc to bero at redhat.com,
SPAM to /dev/null.


--- NEW FILE: autologin.c ---
#include "config.h"
#if !defined(HAVE_SETUID) && !defined(HAVE_SETEUID) && !defined(HAVE_SETREUID)
#error Your OS does not support changing user IDs.
#endif

#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <pwd.h>
#define CONFIG "/etc/sysconfig/autologin"
#define DEFAULT "/usr/X11R6/bin/startx"

#ifdef HAVE_PAM
#include <security/pam_appl.h>
#include <sys/wait.h>
static int PAM_conv(int num_msg, const struct pam_message **msg, struct pam_response **resp, void *appdata_ptr)
{
	/* We use PAM to authenticate for pam_console only, we don't need
	 * its messages */
	*resp=NULL;
	return PAM_SUCCESS;
}
static struct pam_conv PAM_conversation = {
	&PAM_conv,
	NULL
};
#endif

char runthis[1024];

int main(int argc, char **argv)
{
	struct stat st;
	FILE *f;
	char *cfg;
	struct passwd *pw;
	int user_found=0;
	uid_t uid;
	gid_t gid;
	char *dir, *shell;
	char *user=NULL;
	char *cmd=NULL;
#ifdef HAVE_PAM
	pam_handle_t *pamh;
	pid_t child;
	int status;
#endif

	runthis[0]=0; runthis[1023]=0;
	if(getuid()) {
		puts("ERROR: This program needs to change user IDs; therefore, it must be run as root.");
		return 1;
	}
	if(stat(CONFIG, &st)) {
		perror("ERROR: Couldn't stat "CONFIG":");
		return 1;
	}
	if(st.st_mode & S_IWGRP) {
		puts("ERROR: "CONFIG" must not be group-writable!");
		return 1;
	}
	if(st.st_mode & S_IWOTH) {
		puts("ERROR: "CONFIG" must not be world-writable!");
		return 1;
	}
	if(st.st_uid || st.st_gid) {
		puts("ERROR: "CONFIG" must be owned by user root, group root!");
		return 1;
	}	
	f=fopen(CONFIG, "r");
	if(!f) {
		perror("ERROR: Couldn't open "CONFIG":");
		return 1;
	}
	cfg=(char *) malloc(st.st_size+1);
	while(!feof(f) && !ferror(f)) {
		if(fgets(cfg, st.st_size+1, f)) {
			/* Ignore comments... */
			if(cfg[0]=='#')
				continue;
			
			/* Remove whitespaces... */
			while(isspace(cfg[0]))
				strcpy(cfg, cfg+1);
			while(isspace(cfg[strlen(cfg)-1]))
				cfg[strlen(cfg)-1]=0;
			while(strstr(cfg, " ="))
				strcpy(strstr(cfg, " ="), strstr(cfg, " =")+1);
			while(strstr(cfg, "\t="))
				strcpy(strstr(cfg, "\t="), strstr(cfg, "\t=")+1);
			while(strstr(cfg, "= "))
				strcpy(strstr(cfg, "= ")+1, strstr(cfg, "= ")+2);
			while(strstr(cfg, "=\t"))
				strcpy(strstr(cfg, "=\t")+1, strstr(cfg,"=\t")+2);
			if(!strncasecmp(cfg, "AUTOLOGIN=", 10)) {
				if(strlen(cfg)<11 || (strncasecmp(cfg+10, "Y", 1) && strncasecmp(cfg+10, "1", 1)))
					return 0; /* Why did we get called??? */
			} else if(!strncasecmp(cfg, "USER=", 5))
				user=strdup(cfg+5);
			else if(!strncasecmp(cfg, "EXEC=", 5))
				cmd=strdup(cfg+5);
		}
	}
	fclose(f);
	free(cfg);
	if(user==NULL) {
		puts("ERROR: Required variable USER= not found in "CONFIG".");
		if(cmd)
			free(cmd);
		return 1;
	}
	if(cmd==NULL) /* Try a reasonable default... */
		cmd=strdup(DEFAULT);

	snprintf(runthis, 1023, "%s", cmd);
	free(cmd);
	
	pw = getpwnam(user);
	if(pw) {
		user_found=1;
		uid=pw->pw_uid;
		gid=pw->pw_gid;
		dir=strdup(pw->pw_dir);
		shell=strdup(pw->pw_shell);
	} else {
		printf("ERROR: No such user %s!\n", user);
		return 1;
	}

#ifdef PARANOID
	if(pw->pw_uid==0 || pw->pw_gid==0) {
		free(dir); free(shell);
		puts("Autologin as root is not permitted!");
		return 1;
	}
#endif

	/* Take console ownership and satisfy PAM */
#ifdef HAVE_PAM
	pam_start("autologin", user, &PAM_conversation, &pamh);
	pam_acct_mgmt(pamh, PAM_SILENT);
	pam_set_item(pamh, PAM_USER, user);
	pam_set_item(pamh, PAM_TTY, "tty0");
	pam_set_item(pamh, PAM_RHOST, NULL);
	pam_set_item(pamh, PAM_RUSER, user);
	pam_open_session(pamh, PAM_SILENT);
	child=fork();
	if(child==0) {
#else
	chown("/dev/console", uid, gid);
	chown("/dev/tty", uid, gid);
#endif

#ifdef HAVE_SETREGID
	setregid(gid, gid);
#else /* !HAVE_SETREGID */
#ifdef HAVE_SETEGID
	setegid(gid);
#endif
#ifdef HAVE_SETGID
	setgid(gid);
#endif
#endif

#ifdef HAVE_SETREUID
	setreuid(uid, uid);
#else /* !HAVE_SETREUID */
#ifdef HAVE_SETEUID
	seteuid(uid);
#endif /* HAVE_SETEUID */
#ifdef HAVE_SETUID
	setuid(uid);
#endif /* HAVE_SETUID */
#endif /* !HAVE_SETREUID */

	setenv("HOME", dir, 1);
	setenv("SHELL", shell, 1);
	setenv("USER", user, 1);
	setenv("LOGNAME", user, 1);

	chdir(dir);
	free(user);
	user=NULL;
	
	execvp(runthis, argv);
	free(dir); free(shell);
	printf("ERROR: Couldn't exec %s: %s\n", runthis, strerror(errno));
	return 2;
#ifdef HAVE_PAM
	} else {
		waitpid(child, &status, 0);
		pam_close_session(pamh, 0);
		pam_end(pamh, PAM_SUCCESS);
		if(WIFEXITED(status))
			return 0;
		else
			return WEXITSTATUS(status);
	}
#endif
}