리눅스 login.c 소스에 관하여...

/*
 * login [ name ]
 * login -h hostname	(for telnetd, etc.)
 * login -f name	(for pre-authenticated login: datakit, xterm, etc.)
 */
 
/* #define TESTING */
 
#ifdef TESTING
#include "param.h"
#else
//#include <sys/param.h>
#endif
 
#include <stdio.h>
#include <ctype.h>
#include <unistd.h>
#include <getopt.h>
#include <memory.h>
#include <time.h>
#include <sys/stat.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/file.h>
#include <termios.h>
#include <string.h>
#define index strchr
#define rindex strrchr
#include <sys/ioctl.h>
#include <sys/wait.h>
#include <signal.h>
#include <errno.h>
#include <grp.h>
#include <pwd.h>
#include <utmp.h>
#include <setjmp.h>
#include <stdlib.h>
#include <string.h>
#include <sys/syslog.h>
#include <sys/sysmacros.h>
#include <netdb.h>
#include "pathnames.h"
#include "my_crypt.h"
#include "login.h"
#include "xstrncpy.h"
#include "nls.h"
 
#ifdef __linux__
#  include <sys/sysmacros.h>
#  include <linux/major.h>
#endif
 
#ifdef TESTING
#  include "utmp.h"
#else
#  include <utmp.h>
#endif
 
#ifdef SHADOW_PWD
#  include <shadow.h>
#endif
 
#ifdef USE_PAM
#  include <security/pam_appl.h>
#  include <security/pam_misc.h>
#  define PAM_MAX_LOGIN_TRIES	3
#  define PAM_FAIL_CHECK if (retcode != PAM_SUCCESS) { \
       fprintf(stderr,"\n%s\n",pam_strerror(pamh, retcode)); \
       syslog(LOG_ERR,"%s",pam_strerror(pamh, retcode)); \
       pam_end(pamh, retcode); exit(1); \
   }
#  define PAM_END { \
	pam_setcred(pamh, PAM_DELETE_CRED); \
	retcode = pam_close_session(pamh,0); \
	pam_end(pamh,retcode); \
}
#endif
 
#ifndef __linux__
#  include <tzfile.h>
#endif
#include <lastlog.h>
 
#define SLEEP_EXIT_TIMEOUT 5
 
#ifdef __linux__
#define DO_PS_FIDDLING
#endif
 
#ifdef DO_PS_FIDDLING
#include "setproctitle.h"
#endif
 
#if 0
/* from before we had a lastlog.h file in linux */
struct  lastlog
{ long ll_time;
  char ll_line[12];
  char ll_host[16];
};
#endif
 
#ifndef USE_PAM
static void getloginname (void);
static void checknologin (void);
static int rootterm (char *ttyn);
#endif
static void timedout (int);
static void sigint (int);
static void motd (void);
static void dolastlog (int quiet);
 
#ifdef CRYPTOCARD
#include "cryptocard.h"
#endif
 
#ifdef	KERBEROS
#include <kerberos/krb.h>
#include <sys/termios.h>
char	realm[REALM_SZ];
int	kerror = KSUCCESS, notickets = 1;
#endif
 
#ifdef USE_TTY_GROUP
#  define TTY_MODE 0620
#else
#  define TTY_MODE 0600
#endif
 
#define	TTYGRPNAME	"tty"		/* name of group to own ttys */
 
#ifndef MAXPATHLEN
#  define MAXPATHLEN 1024
#endif
 
/*
 * This bounds the time given to login.  Not a define so it can
 * be patched on machines where it's too small.
 */
#ifndef __linux__
int	timeout = 300;
#else
int     timeout = 60;		/* used in cryptocard.c */
#endif
 
struct	passwd *pwd;		/* used in cryptocard.c */
#if USE_PAM
static struct passwd pwdcopy;
#endif
char    hostaddress[4];		/* used in checktty.c */
char	*hostname;		/* idem */
static char	*username, *tty_name, *tty_number;
static char	thishost[100];
static int	failures = 1;
static pid_t	pid;
 
#ifndef __linux__
struct	sgttyb sgttyb;
struct	tchars tc = {
	CINTR, CQUIT, CSTART, CSTOP, CEOT, CBRK
};
struct	ltchars ltc = {
	CSUSP, CDSUSP, CRPRNT, CFLUSH, CWERASE, CLNEXT
};
#endif
 
/* Nice and simple code provided by Linus Torvalds 16-Feb-93 */
/* Nonblocking stuff by Maciej W. Rozycki, <a href="mailto:macro@ds2.pg.gda.pl" rel="nofollow">macro@ds2.pg.gda.pl</a>, 1999.
   He writes: "Login performs open() on a tty in a blocking mode.
   In some cases it may make login wait in open() for carrier infinitely,
   for example if the line is a simplistic case of a three-wire serial
   connection. I believe login should open the line in the non-blocking mode
   leaving the decision to make a connection to getty (where it actually
   belongs). */
static void
opentty(const char * tty) {
	int i, fd, flags;
 
	fd = open(tty, O_RDWR | O_NONBLOCK);
	if (fd == -1) {
		syslog(LOG_ERR, _("FATAL: can't reopen tty: %s"),
		       strerror(errno));
		sleep(1);
		exit(1);
	}
 
	flags = fcntl(fd, F_GETFL);
	flags &= ~O_NONBLOCK;
	fcntl(fd, F_SETFL, flags);
 
	for (i = 0; i < fd; i++)
		close(i);
	for (i = 0; i < 3; i++)
		if (fd != i)
			dup2(fd, i);
	if (fd >= 3)
		close(fd);
}
 
/* In case login is suid it was possible to use a hardlink as stdin
   and exploit races for a local root exploit. (Wojciech Purczynski). */
/* More precisely, the problem is  ttyn := ttyname(0); ...; chown(ttyn);
   here ttyname() might return "/tmp/x", a hardlink to a pseudotty. */
/* All of this is a problem only when login is suid, which it isnt. */
static void
check_ttyname(char *ttyn) {
	struct stat statbuf;
 
	if (lstat(ttyn, &statbuf)
	    || !S_ISCHR(statbuf.st_mode)
	    || (statbuf.st_nlink > 1 && strncmp(ttyn, "/dev/", 5))) {
		syslog(LOG_ERR, _("FATAL: bad tty"));
		sleep(1);
		exit(1);
	}
}
 
/* true if the filedescriptor fd is a console tty, very Linux specific */
static int
consoletty(int fd) {
#ifdef __linux__
    struct stat stb;
 
    if ((fstat(fd, &stb) >= 0) 
	&& (major(stb.st_rdev) == TTY_MAJOR)
	&& (minor(stb.st_rdev) < 64)) {
	return 1;
    }
#endif
    return 0;
}
 
#if USE_PAM
/*
 * Log failed login attempts in _PATH_BTMP if that exists.
 * Must be called only with username the name of an actual user.
 * The most common login failure is to give password instead of username.
 */
#define	_PATH_BTMP	"/var/log/btmp"
static void
logbtmp(const char *line, const char *username, const char *hostname) {
	struct utmp ut;
 
	memset(&ut, 0, sizeof(ut));
 
	strncpy(ut.ut_user, username ? username : "(unknown)",
		sizeof(ut.ut_user));
 
	strncpy(ut.ut_id, line + 3, sizeof(ut.ut_id));
	xstrncpy(ut.ut_line, line, sizeof(ut.ut_line));
 
#if defined(_HAVE_UT_TV)	    /* in <utmpbits.h> included by <utmp.h> */
	gettimeofday(&ut.ut_tv, NULL);
#else
	{
		time_t t;
		time(&t);
		ut.ut_time = t;	    /* ut_time is not always a time_t */
	}
#endif
 
	ut.ut_type = LOGIN_PROCESS; /* XXX doesn't matter */
	ut.ut_pid = pid;
	if (hostname) {
		xstrncpy(ut.ut_host, hostname, sizeof(ut.ut_host));
		if (hostaddress[0])
			memcpy(&ut.ut_addr, hostaddress, sizeof(ut.ut_addr));
	}
#ifdef HAVE_updwtmp		/* bad luck for ancient systems */
	updwtmp(_PATH_BTMP, &ut);
#endif
}
#endif	/* USE_PAM */
 
int
main(int argc, char **argv)
{
    extern int optind;
    extern char *optarg, **environ;
    struct group *gr;
    register int ch;
    register char *p;
    int ask, fflag, hflag, pflag, cnt, errsv;
    int quietlog, passwd_req;
    char *domain, *ttyn;
    char tbuf[MAXPATHLEN + 2], tname[sizeof(_PATH_TTY) + 10];
    char *termenv;
    char *childArgv[10];
    char *buff;
    int childArgc = 0;
#ifdef USE_PAM
    int retcode;
    pam_handle_t *pamh = NULL;
    struct pam_conv conv = { misc_conv, NULL };
    pid_t childPid;
#else
    char *salt, *pp;
#endif
#ifdef CHOWNVCS
    char vcsn[20], vcsan[20];
#endif
 
    pid = getpid();
 
    signal(SIGALRM, timedout);
    alarm((unsigned int)timeout);
    signal(SIGQUIT, SIG_IGN);
    signal(SIGINT, SIG_IGN);
 
    setlocale(LC_ALL, "");
    bindtextdomain(PACKAGE, LOCALEDIR);
    textdomain(PACKAGE);
 
    setpriority(PRIO_PROCESS, 0, 0);
#ifdef HAVE_QUOTA
    quota(Q_SETUID, 0, 0, 0);
#endif
#ifdef DO_PS_FIDDLING
    initproctitle(argc, argv);
#endif
 
    /*
     * -p is used by getty to tell login not to destroy the environment
     * -f is used to skip a second login authentication 
     * -h is used by other servers to pass the name of the remote
     *    host to login so that it may be placed in utmp and wtmp
     */
    gethostname(tbuf, sizeof(tbuf));
    xstrncpy(thishost, tbuf, sizeof(thishost));
    domain = index(tbuf, '.');
 
    username = tty_name = hostname = NULL;
    fflag = hflag = pflag = 0;
    passwd_req = 1;
 
    while ((ch = getopt(argc, argv, "fh:p")) != -1)
      switch (ch) {
	case 'f':
	  fflag = 1;
	  break;
 
	case 'h':
	  if (getuid()) {
	      fprintf(stderr,
		      _("login: -h for super-user only.\n"));
	      exit(1);
	  }
	  hflag = 1;
	  if (domain && (p = index(optarg, '.')) &&
	      strcasecmp(p, domain) == 0)
	    *p = 0;
 
	  hostname = strdup(optarg); 	/* strdup: Ambrose C. Li */
	  {
		  struct hostent *he = gethostbyname(hostname);
 
		  /* he points to static storage; copy the part we use */
		  hostaddress[0] = 0;
		  if (he && he->h_addr_list && he->h_addr_list[0])
			  memcpy(hostaddress, he->h_addr_list[0],
				 sizeof(hostaddress));
	  }
	  break;
 
	case 'p':
	  pflag = 1;
	  break;
 
	case '?':
	default:
	  fprintf(stderr,
		  _("usage: login [-fp] [username]\n"));
	  exit(1);
      }
    argc -= optind;
    argv += optind;
    if (*argv) {
	char *p = *argv;
	username = strdup(p);
	ask = 0;
	/* wipe name - some people mistype their password here */
	/* (of course we are too late, but perhaps this helps a little ..) */
	while(*p)
	    *p++ = ' ';
    } else
        ask = 1;
 
    for (cnt = getdtablesize(); cnt > 2; cnt--)
      close(cnt);
 
    ttyn = ttyname(0);
 
    if (ttyn == NULL || *ttyn == '\0') {
	/* no snprintf required - see definition of tname */
	sprintf(tname, "%s??", _PATH_TTY);
	ttyn = tname;
    }
 
    check_ttyname(ttyn);
 
    if (strncmp(ttyn, "/dev/", 5) == 0)
	tty_name = ttyn+5;
    else
	tty_name = ttyn;
 
    if (strncmp(ttyn, "/dev/tty", 8) == 0)
	tty_number = ttyn+8;
    else {
	char *p = ttyn;
	while (*p && !isdigit(*p)) p++;
	tty_number = p;
    }
 
#ifdef CHOWNVCS
    /* find names of Virtual Console devices, for later mode change */
    snprintf(vcsn, sizeof(vcsn), "/dev/vcs%s", tty_number);
    snprintf(vcsan, sizeof(vcsan), "/dev/vcsa%s", tty_number);
#endif
 
    /* set pgid to pid */
    setpgrp();
    /* this means that setsid() will fail */
 
    {
	struct termios tt, ttt;
 
	tcgetattr(0, &tt);
	ttt = tt;
	ttt.c_cflag &= ~HUPCL;
 
	/* These can fail, e.g. with ttyn on a read-only filesystem */
	chown(ttyn, 0, 0);
	chmod(ttyn, TTY_MODE);
 
	/* Kill processes left on this tty */
	tcsetattr(0,TCSAFLUSH,&ttt);
	signal(SIGHUP, SIG_IGN); /* so vhangup() wont kill us */
	vhangup();
	signal(SIGHUP, SIG_DFL);
 
	/* open stdin,stdout,stderr to the tty */
	opentty(ttyn);
 
	/* restore tty modes */
	tcsetattr(0,TCSAFLUSH,&tt);
    }
 
    openlog("login", LOG_ODELAY, LOG_AUTHPRIV);
 
#if 0
    /* other than iso-8859-1 */
    printf("\033(K");
    fprintf(stderr,"\033(K");
#endif
 
#ifdef USE_PAM
    /*
     * username is initialized to NULL
     * and if specified on the command line it is set.
     * Therefore, we are safe not setting it to anything
     */
 
    retcode = pam_start("login",username, &conv, &pamh);
    if(retcode != PAM_SUCCESS) {
	fprintf(stderr, _("login: PAM Failure, aborting: %s\n"),
		pam_strerror(pamh, retcode));
	syslog(LOG_ERR, _("Couldn't initialize PAM: %s"),
	       pam_strerror(pamh, retcode));
	exit(99);
    }
    /* hostname & tty are either set to NULL or their correct values,
       depending on how much we know */
    retcode = pam_set_item(pamh, PAM_RHOST, hostname);
    PAM_FAIL_CHECK;
    retcode = pam_set_item(pamh, PAM_TTY, tty_name);
    PAM_FAIL_CHECK;
 
    /*
     * <a href="mailto:Andrew.Taylor@cal.montage.ca" rel="nofollow">Andrew.Taylor@cal.montage.ca</a>: Provide a user prompt to PAM
     * so that the "login: " prompt gets localized. Unfortunately,
     * PAM doesn't have an interface to specify the "Password: " string
     * (yet).
     */
    retcode = pam_set_item(pamh, PAM_USER_PROMPT, _("login: "));
    PAM_FAIL_CHECK;
 
#if 0
    /*
     * other than iso-8859-1
     * one more time due to reset tty by PAM
     */
    printf("\033(K");
    fprintf(stderr,"\033(K");
#endif
 
    /* if fflag == 1, then the user has already been authenticated */
    if (fflag && (getuid() == 0))
	passwd_req = 0;
    else
	passwd_req = 1;
 
    if(passwd_req == 1) {
	int failcount=0;
 
	/* if we didn't get a user on the command line, set it to NULL */
	pam_get_item(pamh,  PAM_USER, (const void **) &username);
	if (!username)
		pam_set_item(pamh, PAM_USER, NULL);
 
	/* there may be better ways to deal with some of these
	   conditions, but at least this way I don't think we'll
	   be giving away information... */
	/* Perhaps someday we can trust that all PAM modules will
	   pay attention to failure count and get rid of MAX_LOGIN_TRIES? */
 
	retcode = pam_authenticate(pamh, 0);
	while((failcount++ < PAM_MAX_LOGIN_TRIES) &&
	      ((retcode == PAM_AUTH_ERR) ||
	       (retcode == PAM_USER_UNKNOWN) ||
	       (retcode == PAM_CRED_INSUFFICIENT) ||
	       (retcode == PAM_AUTHINFO_UNAVAIL))) {
	    pam_get_item(pamh, PAM_USER, (const void **) &username);
 
	    syslog(LOG_NOTICE,_("FAILED LOGIN %d FROM %s FOR %s, %s"),
		   failcount, hostname, username, pam_strerror(pamh, retcode));
	    logbtmp(tty_name, username, hostname);
 
	    fprintf(stderr,_("Login incorrect\n\n"));
	    pam_set_item(pamh,PAM_USER,NULL);
	    retcode = pam_authenticate(pamh, 0);
	}
 
	if (retcode != PAM_SUCCESS) {
	    pam_get_item(pamh, PAM_USER, (const void **) &username);
 
	    if (retcode == PAM_MAXTRIES)
		syslog(LOG_NOTICE,_("TOO MANY LOGIN TRIES (%d) FROM %s FOR "
			"%s, %s"), failcount, hostname, username,
			 pam_strerror(pamh, retcode));
	    else
		syslog(LOG_NOTICE,_("FAILED LOGIN SESSION FROM %s FOR %s, %s"),
			hostname, username, pam_strerror(pamh, retcode));
	    logbtmp(tty_name, username, hostname);
 
	    fprintf(stderr,_("\nLogin incorrect\n"));
	    pam_end(pamh, retcode);
	    exit(0);
	}
 
	retcode = pam_acct_mgmt(pamh, 0);
 
	if(retcode == PAM_NEW_AUTHTOK_REQD) {
	    retcode = pam_chauthtok(pamh, PAM_CHANGE_EXPIRED_AUTHTOK);
	}
 
	PAM_FAIL_CHECK;
    }
 
    /*
     * Grab the user information out of the password file for future usage
     * First get the username that we are actually using, though.
     */
    retcode = pam_get_item(pamh, PAM_USER, (const void **) &username);
    PAM_FAIL_CHECK;
 
    if (!username || !*username) {
	    fprintf(stderr, _("\nSession setup problem, abort.\n"));
	    syslog(LOG_ERR, _("NULL user name in %s:%d. Abort."),
		   __FUNCTION__, __LINE__);
	    pam_end(pamh, PAM_SYSTEM_ERR);
	    exit(1);
    }
    if (!(pwd = getpwnam(username))) {
	    fprintf(stderr, _("\nSession setup problem, abort.\n"));
	    syslog(LOG_ERR, _("Invalid user name \"%s\" in %s:%d. Abort."),
		   username, __FUNCTION__, __LINE__);
	    pam_end(pamh, PAM_SYSTEM_ERR);
	    exit(1);
    }
 
    /*
     * Create a copy of the pwd struct - otherwise it may get
     * clobbered by PAM
     */
    memcpy(&pwdcopy, pwd, sizeof(*pwd));
    pwd = &pwdcopy;
    pwd->pw_name   = strdup(pwd->pw_name);
    pwd->pw_passwd = strdup(pwd->pw_passwd);
    pwd->pw_gecos  = strdup(pwd->pw_gecos);
    pwd->pw_dir    = strdup(pwd->pw_dir);
    pwd->pw_shell  = strdup(pwd->pw_shell);
    if (!pwd->pw_name || !pwd->pw_passwd || !pwd->pw_gecos ||
	!pwd->pw_dir || !pwd->pw_shell) {
	    fprintf(stderr, _("login: Out of memory\n"));
	    syslog(LOG_ERR, "Out of memory");
	    pam_end(pamh, PAM_SYSTEM_ERR);
	    exit(1);
    }
    username = pwd->pw_name;
 
    /*
     * Initialize the supplementary group list.
     * This should be done before pam_setcred because
     * the PAM modules might add groups during pam_setcred.
     */
    if (initgroups(username, pwd->pw_gid) < 0) {
	    syslog(LOG_ERR, "initgroups: %m");
	    fprintf(stderr, _("\nSession setup problem, abort.\n"));
	    pam_end(pamh, PAM_SYSTEM_ERR);
	    exit(1);
    }
 
    retcode = pam_open_session(pamh, 0);
    PAM_FAIL_CHECK;
 
    retcode = pam_setcred(pamh, PAM_ESTABLISH_CRED);
    PAM_FAIL_CHECK;
 
#else /* ! USE_PAM */
 
    for (cnt = 0;; ask = 1) {
 
	if (ask) {
	    fflag = 0;
	    getloginname();
	}
 
	/* Dirty patch to fix a gigantic security hole when using 
	   yellow pages. This problem should be solved by the
	   libraries, and not by programs, but this must be fixed
	   urgently! If the first char of the username is '+', we 
	   avoid login success.
	   Feb 95 <alvaro@etsit.upm.es> */
 
	if (username[0] == '+') {
	    puts(_("Illegal username"));
	    badlogin(username);
	    sleepexit(1);
	}
 
	/* (void)strcpy(tbuf, username); why was this here? */
	if ((pwd = getpwnam(username))) {
#  ifdef SHADOW_PWD
	    struct spwd *sp;
 
	    if ((sp = getspnam(username)))
	      pwd->pw_passwd = sp->sp_pwdp;
#  endif
	    salt = pwd->pw_passwd;
	} else
	  salt = "xx";
 
	if (pwd) {
	    initgroups(username, pwd->pw_gid);
	    checktty(username, tty_name, pwd); /* in checktty.c */
	}
 
	/* if user not super-user, check for disabled logins */
	if (pwd == NULL || pwd->pw_uid)
	  checknologin();
 
	/*
	 * Disallow automatic login to root; if not invoked by
	 * root, disallow if the uid's differ.
	 */
	if (fflag && pwd) {
	    int uid = getuid();
 
	    passwd_req = pwd->pw_uid == 0 ||
	      (uid && uid != pwd->pw_uid);
	}
 
	/*
	 * If trying to log in as root, but with insecure terminal,
	 * refuse the login attempt.
	 */
	if (pwd && pwd->pw_uid == 0 && !rootterm(tty_name)) {
	    fprintf(stderr,
		    _("%s login refused on this terminal.\n"),
		    pwd->pw_name);
 
	    if (hostname)
	      syslog(LOG_NOTICE,
		     _("LOGIN %s REFUSED FROM %s ON TTY %s"),
		     pwd->pw_name, hostname, tty_name);
	    else
	      syslog(LOG_NOTICE,
		     _("LOGIN %s REFUSED ON TTY %s"),
		     pwd->pw_name, tty_name);
	    continue;
	}
 
	/*
	 * If no pre-authentication and a password exists
	 * for this user, prompt for one and verify it.
	 */
	if (!passwd_req || (pwd && !*pwd->pw_passwd))
	  break;
 
	setpriority(PRIO_PROCESS, 0, -4);
	pp = getpass(_("Password: "));
 
#  ifdef CRYPTOCARD
	if (strncmp(pp, "CRYPTO", 6) == 0) {
	    if (pwd && cryptocard()) break;
	}
#  endif /* CRYPTOCARD */
 
	p = crypt(pp, salt);
	setpriority(PRIO_PROCESS, 0, 0);
 
#  ifdef KERBEROS
	/*
	 * If not present in pw file, act as we normally would.
	 * If we aren't Kerberos-authenticated, try the normal
	 * pw file for a password.  If that's ok, log the user
	 * in without issueing any tickets.
	 */
 
	if (pwd && !krb_get_lrealm(realm,1)) {
	    /*
	     * get TGT for local realm; be careful about uid's
	     * here for ticket file ownership
	     */
	    setreuid(geteuid(),pwd->pw_uid);
	    kerror = krb_get_pw_in_tkt(pwd->pw_name, "", realm,
				       "krbtgt", realm, DEFAULT_TKT_LIFE, pp);
	    setuid(0);
	    if (kerror == INTK_OK) {
		memset(pp, 0, strlen(pp));
		notickets = 0;	/* user got ticket */
		break;
	    }
	}
#  endif /* KERBEROS */
	memset(pp, 0, strlen(pp));
 
	if (pwd && !strcmp(p, pwd->pw_passwd))
	  break;
 
	printf(_("Login incorrect\n"));
	badlogin(username); /* log ALL bad logins */
	failures++;
 
	/* we allow 10 tries, but after 3 we start backing off */
	if (++cnt > 3) {
	    if (cnt >= 10) {
		sleepexit(1);
	    }
	    sleep((unsigned int)((cnt - 3) * 5));
	}
    }
#endif /* !USE_PAM */
 
    /* committed to login -- turn off timeout */
    alarm((unsigned int)0);
 
#ifdef HAVE_QUOTA
    if (quota(Q_SETUID, pwd->pw_uid, 0, 0) < 0 && errno != EINVAL) {
	switch(errno) {
	  case EUSERS:
	    fprintf(stderr,
		    _("Too many users logged on already.\nTry again later.\n"));
	    break;
	  case EPROCLIM:
	    fprintf(stderr,
		    _("You have too many processes running.\n"));
	    break;
	  default:
	    perror("quota (Q_SETUID)");
	}
	sleepexit(0);		/* %% */
    }
#endif
 
    /* paranoia... */
#ifdef SHADOW_PWD
    endspent();
#endif
    endpwent();
 
    /* This requires some explanation: As root we may not be able to
       read the directory of the user if it is on an NFS mounted
       filesystem. We temporarily set our effective uid to the user-uid
       making sure that we keep root privs. in the real uid. 
 
       A portable solution would require a fork(), but we rely on Linux
       having the BSD setreuid() */
 
    {
	char tmpstr[MAXPATHLEN];
	uid_t ruid = getuid();
	gid_t egid = getegid();
 
	/* avoid snprintf - old systems do not have it, or worse,
	   have a libc in which snprintf is the same as sprintf */
	if (strlen(pwd->pw_dir) + sizeof(_PATH_HUSHLOGIN) + 2 > MAXPATHLEN)
		quietlog = 0;
	else {
		sprintf(tmpstr, "%s/%s", pwd->pw_dir, _PATH_HUSHLOGIN);
		setregid(-1, pwd->pw_gid);
		setreuid(0, pwd->pw_uid);
		quietlog = (access(tmpstr, R_OK) == 0);
		setuid(0); /* setreuid doesn't do it alone! */
		setreuid(ruid, 0);
		setregid(-1, egid);
	}
    }
 
    /* for linux, write entries in utmp and wtmp */
    {
	struct utmp ut;
	struct utmp *utp;
 
	utmpname(_PATH_UTMP);
	setutent();
 
	/* Find pid in utmp.
login sometimes overwrites the runlevel entry in /var/run/utmp,
confusing sysvinit. I added a test for the entry type, and the problem
was gone. (In a runlevel entry, st_pid is not really a pid but some number
calculated from the previous and current runlevel).
Michael Riepe <michael@stud.uni-hannover.de>
	*/
	while ((utp = getutent()))
		if (utp->ut_pid == pid
		    && utp->ut_type >= INIT_PROCESS
		    && utp->ut_type <= DEAD_PROCESS)
			break;
 
	/* If we can't find a pre-existing entry by pid, try by line.
	   BSD network daemons may rely on this. (anonymous) */
	if (utp == NULL) {
	     setutent();
	     ut.ut_type = LOGIN_PROCESS;
	     strncpy(ut.ut_line, tty_name, sizeof(ut.ut_line));
	     utp = getutline(&ut);
	}
 
	if (utp) {
	    memcpy(&ut, utp, sizeof(ut));
	} else {
	    /* some gettys/telnetds don't initialize utmp... */
	    memset(&ut, 0, sizeof(ut));
	}
 
	if (ut.ut_id[0] == 0)
	  strncpy(ut.ut_id, tty_number, sizeof(ut.ut_id));
 
	strncpy(ut.ut_user, username, sizeof(ut.ut_user));
	xstrncpy(ut.ut_line, tty_name, sizeof(ut.ut_line));
#ifdef _HAVE_UT_TV		/* in <utmpbits.h> included by <utmp.h> */
	gettimeofday(&ut.ut_tv, NULL);
#else
	{
	    time_t t;
	    time(&t);
	    ut.ut_time = t;	/* ut_time is not always a time_t */
				/* glibc2 #defines it as ut_tv.tv_sec */
	}
#endif
	ut.ut_type = USER_PROCESS;
	ut.ut_pid = pid;
	if (hostname) {
		xstrncpy(ut.ut_host, hostname, sizeof(ut.ut_host));
		if (hostaddress[0])
			memcpy(&ut.ut_addr, hostaddress, sizeof(ut.ut_addr));
	}
 
	pututline(&ut);
	endutent();
 
#ifdef HAVE_updwtmp
	updwtmp(_PATH_WTMP, &ut);
#else
#if 0
	/* The O_APPEND open() flag should be enough to guarantee
	   atomic writes at end of file. */
	{
	    int wtmp;
 
	    if((wtmp = open(_PATH_WTMP, O_APPEND|O_WRONLY)) >= 0) {
		write(wtmp, (char *)&ut, sizeof(ut));
		close(wtmp);
	    }
	}
#else
	/* Probably all this locking below is just nonsense,
	   and the short version is OK as well. */
	{ 
	    int lf, wtmp;
	    if ((lf = open(_PATH_WTMPLOCK, O_CREAT|O_WRONLY, 0660)) >= 0) {
		flock(lf, LOCK_EX);
		if ((wtmp = open(_PATH_WTMP, O_APPEND|O_WRONLY)) >= 0) {
		    write(wtmp, (char *)&ut, sizeof(ut));
		    close(wtmp);
		}
		flock(lf, LOCK_UN);
		close(lf);
	    }
	}
#endif
#endif
    }
 
    dolastlog(quietlog);
 
    chown(ttyn, pwd->pw_uid,
	  (gr = getgrnam(TTYGRPNAME)) ? gr->gr_gid : pwd->pw_gid);
    chmod(ttyn, TTY_MODE);
 
#ifdef CHOWNVCS
    /* if tty is one of the VC's then change owner and mode of the 
       special /dev/vcs devices as well */
    if (consoletty(0)) {
	chown(vcsn, pwd->pw_uid, (gr ? gr->gr_gid : pwd->pw_gid));
	chown(vcsan, pwd->pw_uid, (gr ? gr->gr_gid : pwd->pw_gid));
	chmod(vcsn, TTY_MODE);
	chmod(vcsan, TTY_MODE);
    }
#endif
 
    setgid(pwd->pw_gid);
 
#ifdef HAVE_QUOTA
    quota(Q_DOWARN, pwd->pw_uid, (dev_t)-1, 0);
#endif
 
    if (*pwd->pw_shell == '\0')
      pwd->pw_shell = _PATH_BSHELL;
 
    /* preserve TERM even without -p flag */
    {
	char *ep;
 
	if(!((ep = getenv("TERM")) && (termenv = strdup(ep))))
	  termenv = "dumb";
    }
 
    /* destroy environment unless user has requested preservation */
    if (!pflag)
      {
          environ = (char**)malloc(sizeof(char*));
	  memset(environ, 0, sizeof(char*));
      }
 
    setenv("HOME", pwd->pw_dir, 0);      /* legal to override */
    if(pwd->pw_uid)
      setenv("PATH", _PATH_DEFPATH, 1);
    else
      setenv("PATH", _PATH_DEFPATH_ROOT, 1);
 
    setenv("SHELL", pwd->pw_shell, 1);
    setenv("TERM", termenv, 1);
 
    /* mailx will give a funny error msg if you forget this one */
    {
      char tmp[MAXPATHLEN];
      /* avoid snprintf */
      if (sizeof(_PATH_MAILDIR) + strlen(pwd->pw_name) + 1 < MAXPATHLEN) {
	      sprintf(tmp, "%s/%s", _PATH_MAILDIR, pwd->pw_name);
	      setenv("MAIL",tmp,0);
      }
    }
 
    /* LOGNAME is not documented in login(1) but
       HP-UX 6.5 does it. We'll not allow modifying it.
       */
    setenv("LOGNAME", pwd->pw_name, 1);
 
#ifdef USE_PAM
    {
	int i;
	char ** env = pam_getenvlist(pamh);
 
	if (env != NULL) {
	    for (i=0; env[i]; i++) {
		putenv(env[i]);
		/* D(("env[%d] = %s", i,env[i])); */
	    }
	}
    }
#endif
 
#ifdef DO_PS_FIDDLING
    setproctitle("login", username);
#endif
 
    if (!strncmp(tty_name, "ttyS", 4))
      syslog(LOG_INFO, _("DIALUP AT %s BY %s"), tty_name, pwd->pw_name);
 
    /* allow tracking of good logins.
       -steve philp (sphilp@mail.alliance.net) */
 
    if (pwd->pw_uid == 0) {
	if (hostname)
	  syslog(LOG_NOTICE, _("ROOT LOGIN ON %s FROM %s"),
		 tty_name, hostname);
	else
	  syslog(LOG_NOTICE, _("ROOT LOGIN ON %s"), tty_name);
    } else {
	if (hostname) 
	  syslog(LOG_INFO, _("LOGIN ON %s BY %s FROM %s"), tty_name, 
		 pwd->pw_name, hostname);
	else 
	  syslog(LOG_INFO, _("LOGIN ON %s BY %s"), tty_name, 
		 pwd->pw_name);
    }
 
    if (!quietlog) {
	motd();
 
#ifdef DO_STAT_MAIL
	/*
	 * This turns out to be a bad idea: when the mail spool
	 * is NFS mounted, and the NFS connection hangs, the
	 * login hangs, even root cannot login.
	 * Checking for mail should be done from the shell.
	 */
	{
	    struct stat st;
	    char *mail;
 
	    mail = getenv("MAIL");
	    if (mail && stat(mail, &st) == 0 && st.st_size != 0) {
		if (st.st_mtime > st.st_atime)
			printf(_("You have new mail.\n"));
		else
			printf(_("You have mail.\n"));
	    }
	}
#endif
    }
 
    signal(SIGALRM, SIG_DFL);
    signal(SIGQUIT, SIG_DFL);
    signal(SIGTSTP, SIG_IGN);
 
#ifdef USE_PAM
    /*
     * We must fork before setuid() because we need to call
     * pam_close_session() as root.
     */
 
    childPid = fork();
    if (childPid < 0) {
       int errsv = errno;
       /* error in fork() */
       fprintf(stderr, _("login: failure forking: %s"), strerror(errsv));
       PAM_END;
       exit(0);
    }
 
    if (childPid) {
       /* parent - wait for child to finish, then cleanup session */
       signal(SIGHUP, SIG_IGN);
       signal(SIGINT, SIG_IGN);
       signal(SIGQUIT, SIG_IGN);
       signal(SIGTSTP, SIG_IGN);
       signal(SIGTTIN, SIG_IGN);
       signal(SIGTTOU, SIG_IGN);
 
       wait(NULL);
       PAM_END;
       exit(0);
    }
 
    /* child */
    /*
     * Problem: if the user's shell is a shell like ash that doesnt do
     * setsid() or setpgrp(), then a ctrl-\, sending SIGQUIT to every
     * process in the pgrp, will kill us.
     */
 
    /* start new session */
    setsid();
 
    /* make sure we have a controlling tty */
    opentty(ttyn);
    openlog("login", LOG_ODELAY, LOG_AUTHPRIV);	/* reopen */
 
    /*
     * TIOCSCTTY: steal tty from other process group.
     */
    if (ioctl(0, TIOCSCTTY, 1))
	    syslog(LOG_ERR, _("TIOCSCTTY failed: %m"));
#endif
    signal(SIGINT, SIG_DFL);
 
    /* discard permissions last so can't get killed and drop core */
    if(setuid(pwd->pw_uid) < 0 && pwd->pw_uid) {
	syslog(LOG_ALERT, _("setuid() failed"));
	exit(1);
    }
 
    /* wait until here to change directory! */
    if (chdir(pwd->pw_dir) < 0) {
	printf(_("No directory %s!\n"), pwd->pw_dir);
	if (chdir("/"))
	  exit(0);
	pwd->pw_dir = "/";
	printf(_("Logging in with home = \"/\".\n"));
    }
 
    /* if the shell field has a space: treat it like a shell script */
    if (strchr(pwd->pw_shell, ' ')) {
	buff = malloc(strlen(pwd->pw_shell) + 6);
 
	if (!buff) {
	    fprintf(stderr, _("login: no memory for shell script.\n"));
	    exit(0);
	}
 
	strcpy(buff, "exec ");
	strcat(buff, pwd->pw_shell);
	childArgv[childArgc++] = "/bin/sh";
	childArgv[childArgc++] = "-sh";
	childArgv[childArgc++] = "-c";
	childArgv[childArgc++] = buff;
    } else {
	tbuf[0] = '-';
	xstrncpy(tbuf + 1, ((p = rindex(pwd->pw_shell, '/')) ?
			   p + 1 : pwd->pw_shell),
		sizeof(tbuf)-1);
 
	childArgv[childArgc++] = pwd->pw_shell;
	childArgv[childArgc++] = tbuf;
    }
 
    childArgv[childArgc++] = NULL;
 
    execvp(childArgv[0], childArgv + 1);
 
    errsv = errno;
 
    if (!strcmp(childArgv[0], "/bin/sh"))
	fprintf(stderr, _("login: couldn't exec shell script: %s.\n"),
		strerror(errsv));
    else
	fprintf(stderr, _("login: no shell: %s.\n"), strerror(errsv));
 
    exit(0);
}
 
#ifndef USE_PAM
static void
getloginname(void) {
    int ch, cnt, cnt2;
    char *p;
    static char nbuf[UT_NAMESIZE + 1];
 
    cnt2 = 0;
    for (;;) {
	cnt = 0;
	printf(_("\n%s login: "), thishost); fflush(stdout);
	for (p = nbuf; (ch = getchar()) != '\n'; ) {
	    if (ch == EOF) {
		badlogin("EOF");
		exit(0);
	    }
	    if (p < nbuf + UT_NAMESIZE)
	      *p++ = ch;
 
	    cnt++;
	    if (cnt > UT_NAMESIZE + 20) {
		fprintf(stderr, _("login name much too long.\n"));
		badlogin(_("NAME too long"));
		exit(0);
	    }
	}
	if (p > nbuf) {
	  if (nbuf[0] == '-')
	    fprintf(stderr,
		    _("login names may not start with '-'.\n"));
	  else {
	      *p = '\0';
	      username = nbuf;
	      break;
	  }
	}
 
	cnt2++;
	if (cnt2 > 50) {
	    fprintf(stderr, _("too many bare linefeeds.\n"));
	    badlogin(_("EXCESSIVE linefeeds"));
	    exit(0);
	}
    }
}
#endif
 
/*
 * Robert Ambrose writes:
 * A couple of my users have a problem with login processes hanging around
 * soaking up pts's.  What they seem to hung up on is trying to write out the
 * message 'Login timed out after %d seconds' when the connection has already
 * been dropped.
 * What I did was add a second timeout while trying to write the message so
 * the process just exits if the second timeout expires.
 */
 
static void
timedout2(int sig) {
	struct termio ti;
 
	/* reset echo */
	ioctl(0, TCGETA, &ti);
	ti.c_lflag |= ECHO;
	ioctl(0, TCSETA, &ti);
	exit(0);			/* %% */
}
 
static void
timedout(int sig) {
	signal(SIGALRM, timedout2);
	alarm(10);
	fprintf(stderr, _("Login timed out after %d seconds\n"), timeout);
	signal(SIGALRM, SIG_IGN);
	alarm(0);
	timedout2(0);
}
 
#ifndef USE_PAM
int
rootterm(char * ttyn)
{ 
    int fd;
    char buf[100],*p;
    int cnt, more = 0;
 
    fd = open(SECURETTY, O_RDONLY);
    if(fd < 0) return 1;
 
    /* read each line in /etc/securetty, if a line matches our ttyline
       then root is allowed to login on this tty, and we should return
       true. */
    for(;;) {
	p = buf; cnt = 100;
	while(--cnt >= 0 && (more = read(fd, p, 1)) == 1 && *p != '\n') p++;
	if(more && *p == '\n') {
	    *p = '\0';
	    if(!strcmp(buf, ttyn)) {
		close(fd);
		return 1;
	    } else
	      continue;
  	} else {
	    close(fd);
	    return 0;
  	}
    }
}
#endif /* !USE_PAM */
 
jmp_buf motdinterrupt;
 
void
motd(void) {
    int fd, nchars;
    void (*oldint)(int);
    char tbuf[8192];
 
    if ((fd = open(_PATH_MOTDFILE, O_RDONLY, 0)) < 0)
      return;
    oldint = signal(SIGINT, sigint);
    if (setjmp(motdinterrupt) == 0)
      while ((nchars = read(fd, tbuf, sizeof(tbuf))) > 0)
	write(fileno(stdout), tbuf, nchars);
    signal(SIGINT, oldint);
    close(fd);
}
 
void
sigint(int sig) {
    longjmp(motdinterrupt, 1);
}
 
#ifndef USE_PAM				/* PAM takes care of this */
void
checknologin(void) {
    int fd, nchars;
    char tbuf[8192];
 
    if ((fd = open(_PATH_NOLOGIN, O_RDONLY, 0)) >= 0) {
	while ((nchars = read(fd, tbuf, sizeof(tbuf))) > 0)
	  write(fileno(stdout), tbuf, nchars);
	close(fd);
	sleepexit(0);
    }
}
#endif
 
void
dolastlog(int quiet) {
    struct lastlog ll;
    int fd;
 
    if ((fd = open(_PATH_LASTLOG, O_RDWR, 0)) >= 0) {
	lseek(fd, (off_t)pwd->pw_uid * sizeof(ll), SEEK_SET);
	if (!quiet) {
	    if (read(fd, (char *)&ll, sizeof(ll)) == sizeof(ll) &&
		ll.ll_time != 0) {
		    time_t ll_time = (time_t) ll.ll_time;
 
		    printf(_("Last login: %.*s "),
			   24-5, ctime(&ll_time));
 
		    if (*ll.ll_host != '\0')
			    printf(_("from %.*s\n"),
				   (int)sizeof(ll.ll_host), ll.ll_host);
		    else
			    printf(_("on %.*s\n"),
				   (int)sizeof(ll.ll_line), ll.ll_line);
	    }
	    lseek(fd, (off_t)pwd->pw_uid * sizeof(ll), SEEK_SET);
	}
	memset((char *)&ll, 0, sizeof(ll));
	time(&ll.ll_time);
	xstrncpy(ll.ll_line, tty_name, sizeof(ll.ll_line));
	if (hostname)
	    xstrncpy(ll.ll_host, hostname, sizeof(ll.ll_host));
 
	write(fd, (char *)&ll, sizeof(ll));
	close(fd);
    }
}
 
void
badlogin(const char *name) {       //이건 원본 파일이지만 이 부분이 제가 수정한 부분입니다.
    if (failures == 1) {
	if (hostname)
	  syslog(LOG_NOTICE, _("LOGIN FAILURE FROM %s, %s"),
		 hostname, name);
	else
	  syslog(LOG_NOTICE, _("LOGIN FAILURE ON %s, %s"),
		 tty_name, name);
    } else {
	if (hostname)
	  syslog(LOG_NOTICE, _("%d LOGIN FAILURES FROM %s, %s"),
		 failures, hostname, name);
	else
	  syslog(LOG_NOTICE, _("%d LOGIN FAILURES ON %s, %s"),
		 failures, tty_name, name);
    }
}
 
/* Should not be called from PAM code... */
void
sleepexit(int eval) {
    sleep(SLEEP_EXIT_TIMEOUT);
    exit(eval);
}