source: MondoRescue/branches/stable/mindi-busybox/loginutils/login.c@ 1247

/* vi: set sw=4 ts=4: */
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <termios.h>
#include <unistd.h>
#include <utmp.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <ctype.h>
#include <time.h>

#include "busybox.h"
#ifdef CONFIG_SELINUX
#include <selinux/selinux.h>  /* for is_selinux_enabled()  */
#include <selinux/get_context_list.h> /* for get_default_context() */
#include <selinux/flask.h> /* for security class definitions  */
#include <errno.h>
#endif

#ifdef CONFIG_FEATURE_UTMP
// import from utmp.c
static void checkutmp(int picky);
static void setutmp(const char *name, const char *line);
/* Stuff global to this file */
static struct utmp utent;
#endif

// login defines
#define TIMEOUT       60
#define EMPTY_USERNAME_COUNT    10
#define USERNAME_SIZE 32


static int check_nologin ( int amroot );

#if defined CONFIG_FEATURE_SECURETTY
static int check_tty ( const char *tty );

#else
static inline int check_tty ( const char *tty )  { return 1; }

#endif

static int is_my_tty ( const char *tty );
static int login_prompt ( char *buf_name );
static void motd ( void );


static void alarm_handler ( int sig ATTRIBUTE_UNUSED)
{
    fprintf (stderr, "\nLogin timed out after %d seconds.\n", TIMEOUT );
    exit ( EXIT_SUCCESS );
}


int login_main(int argc, char **argv)
{
    char tty[BUFSIZ];
    char full_tty[200];
    char fromhost[512];
    char username[USERNAME_SIZE];
    const char *tmp;
    int amroot;
    int flag;
    int failed;
    int count=0;
    struct passwd *pw, pw_copy;
#ifdef CONFIG_WHEEL_GROUP
    struct group *grp;
#endif
    int opt_preserve = 0;
    int opt_fflag = 0;
    char *opt_host = 0;
    int alarmstarted = 0;
#ifdef CONFIG_SELINUX
    security_context_t user_sid = NULL;
#endif

    username[0]=0;
    amroot = ( getuid ( ) == 0 );
    signal ( SIGALRM, alarm_handler );
    alarm ( TIMEOUT );
    alarmstarted = 1;

    while (( flag = getopt(argc, argv, "f:h:p")) != EOF ) {
        switch ( flag ) {
        case 'p':
            opt_preserve = 1;
            break;
        case 'f':
            /*
             * username must be a separate token
             * (-f root, *NOT* -froot). --marekm
             */
            if ( optarg != argv[optind-1] )
                bb_show_usage( );

            if ( !amroot )      /* Auth bypass only if real UID is zero */
                bb_error_msg_and_die ( "-f permission denied" );

            safe_strncpy(username, optarg, USERNAME_SIZE);
            opt_fflag = 1;
            break;
        case 'h':
            opt_host = optarg;
            break;
        default:
            bb_show_usage( );
        }
    }

    if (optind < argc)             // user from command line (getty)
        safe_strncpy(username, argv[optind], USERNAME_SIZE);

    if ( !isatty ( 0 ) || !isatty ( 1 ) || !isatty ( 2 ))
        return EXIT_FAILURE;        /* Must be a terminal */

#ifdef CONFIG_FEATURE_UTMP
    checkutmp ( !amroot );
#endif

    tmp = ttyname ( 0 );
    if ( tmp && ( strncmp ( tmp, "/dev/", 5 ) == 0 ))
        safe_strncpy ( tty, tmp + 5, sizeof( tty ));
    else if ( tmp && *tmp == '/' )
        safe_strncpy ( tty, tmp, sizeof( tty ));
    else
        safe_strncpy ( tty, "UNKNOWN", sizeof( tty ));

#ifdef CONFIG_FEATURE_UTMP
    if ( amroot )
        memset ( utent.ut_host, 0, sizeof utent.ut_host );
#endif

    if ( opt_host ) {
#ifdef CONFIG_FEATURE_UTMP
        safe_strncpy ( utent.ut_host, opt_host, sizeof( utent. ut_host ));
#endif
        snprintf ( fromhost, sizeof( fromhost ) - 1, " on `%.100s' from `%.200s'", tty, opt_host );
    }
    else
        snprintf ( fromhost, sizeof( fromhost ) - 1, " on `%.100s'", tty );

    bb_setpgrp;

    openlog ( "login", LOG_PID | LOG_CONS | LOG_NOWAIT, LOG_AUTH );

    while ( 1 ) {
        failed = 0;

        if ( !username[0] )
            if(!login_prompt ( username ))
                return EXIT_FAILURE;

        if ( !alarmstarted && ( TIMEOUT > 0 )) {
            alarm ( TIMEOUT );
            alarmstarted = 1;
        }

        if (!( pw = getpwnam ( username ))) {
            pw_copy.pw_name   = "UNKNOWN";
            pw_copy.pw_passwd = "!";
            opt_fflag = 0;
            failed = 1;
        } else
            pw_copy = *pw;

        pw = &pw_copy;

        if (( pw-> pw_passwd [0] == '!' ) || ( pw-> pw_passwd[0] == '*' ))
            failed = 1;

        if ( opt_fflag ) {
            opt_fflag = 0;
            goto auth_ok;
        }

        if (!failed && ( pw-> pw_uid == 0 ) && ( !check_tty ( tty )))
            failed = 1;

        /* Don't check the password if password entry is empty (!) */
        if ( !pw-> pw_passwd[0] )
            goto auth_ok;

        /* authorization takes place here */
        if ( correct_password ( pw ))
            goto auth_ok;

        failed = 1;

auth_ok:
        if ( !failed)
            break;

        bb_do_delay(FAIL_DELAY);
        puts("Login incorrect");
        username[0] = 0;
        if ( ++count == 3 ) {
            syslog ( LOG_WARNING, "invalid password for `%s'%s\n", pw->pw_name, fromhost);
            return EXIT_FAILURE;
    }
    }

    alarm ( 0 );
    if ( check_nologin ( pw-> pw_uid == 0 ))
        return EXIT_FAILURE;

#ifdef CONFIG_FEATURE_UTMP
    setutmp ( username, tty );
#endif

    if ( *tty != '/' )
        snprintf ( full_tty, sizeof( full_tty ) - 1, "/dev/%s", tty);
    else
        safe_strncpy ( full_tty, tty, sizeof( full_tty ) - 1 );

#ifdef CONFIG_SELINUX
    if (is_selinux_enabled())
    {
        security_context_t old_tty_sid, new_tty_sid;

        if (get_default_context(username, NULL, &user_sid))
        {
            fprintf(stderr, "Unable to get SID for %s\n", username);
            exit(1);
        }
        if (getfilecon(full_tty, &old_tty_sid) < 0)
        {
            fprintf(stderr, "getfilecon(%.100s) failed: %.100s\n", full_tty, strerror(errno));
            return EXIT_FAILURE;
        }
        if (security_compute_relabel(user_sid, old_tty_sid, SECCLASS_CHR_FILE, &new_tty_sid) != 0)
        {
            fprintf(stderr, "security_change_sid(%.100s) failed: %.100s\n", full_tty, strerror(errno));
            return EXIT_FAILURE;
        }
        if(setfilecon(full_tty, new_tty_sid) != 0)
        {
            fprintf(stderr, "chsid(%.100s, %s) failed: %.100s\n", full_tty, new_tty_sid, strerror(errno));
            return EXIT_FAILURE;
        }
    }
#endif
    if ( !is_my_tty ( full_tty ))
        syslog ( LOG_ERR, "unable to determine TTY name, got %s\n", full_tty );

    /* Try these, but don't complain if they fail
     * (for example when the root fs is read only) */
    chown ( full_tty, pw-> pw_uid, pw-> pw_gid );
    chmod ( full_tty, 0600 );

    change_identity ( pw );
    tmp = pw-> pw_shell;
    if(!tmp || !*tmp)
        tmp = DEFAULT_SHELL;
    setup_environment ( tmp, 1, !opt_preserve, pw );

    motd ( );
    signal ( SIGALRM, SIG_DFL );    /* default alarm signal */

    if ( pw-> pw_uid == 0 )
        syslog ( LOG_INFO, "root login %s\n", fromhost );
#ifdef CONFIG_SELINUX
    /* well, a simple setexeccon() here would do the job as well,
     * but let's play the game for now */
    set_current_security_context(user_sid);
#endif
    run_shell ( tmp, 1, 0, 0);  /* exec the shell finally. */

    return EXIT_FAILURE;
}



static int login_prompt ( char *buf_name )
{
    char buf [1024];
    char *sp, *ep;
    int i;

    for(i=0; i<EMPTY_USERNAME_COUNT; i++) {
        print_login_prompt();

        if ( !fgets ( buf, sizeof( buf ) - 1, stdin ))
            return 0;

        if ( !strchr ( buf, '\n' ))
            return 0;

        for ( sp = buf; isspace ( *sp ); sp++ ) { }
        for ( ep = sp; isgraph ( *ep ); ep++ ) { }

        *ep = 0;
        safe_strncpy(buf_name, sp, USERNAME_SIZE);
        if(buf_name[0])
            return 1;
    }
    return 0;
}


static int check_nologin ( int amroot )
{
    if ( access ( bb_path_nologin_file, F_OK ) == 0 ) {
        FILE *fp;
        int c;

        if (( fp = fopen ( bb_path_nologin_file, "r" ))) {
            while (( c = getc ( fp )) != EOF )
                putchar (( c == '\n' ) ? '\r' : c );

            fflush ( stdout );
            fclose ( fp );
        } else {
            puts ( "\r\nSystem closed for routine maintenance.\r" );
        }
        if ( !amroot )
            return 1;

        puts ( "\r\n[Disconnect bypassed -- root login allowed.]\r" );
    }
    return 0;
}

#ifdef CONFIG_FEATURE_SECURETTY

static int check_tty ( const char *tty )
{
    FILE *fp;
    int i;
    char buf[BUFSIZ];

    if (( fp = fopen ( bb_path_securetty_file, "r" ))) {
        while ( fgets ( buf, sizeof( buf ) - 1, fp )) {
            for ( i = strlen( buf ) - 1; i >= 0; --i ) {
                if ( !isspace ( buf[i] ))
                    break;
            }
            buf[++i] = '\0';
            if (( buf [0] == '\0' ) || ( buf [0] == '#' ))
                continue;

            if ( strcmp ( buf, tty ) == 0 ) {
                fclose ( fp );
                return 1;
            }
        }
        fclose(fp);
        return 0;
    }
    /* A missing securetty file is not an error. */
    return 1;
}

#endif

/* returns 1 if true */
static int is_my_tty ( const char *tty )
{
    struct stat by_name, by_fd;

    if ( stat ( tty, &by_name ) || fstat ( 0, &by_fd ))
        return 0;

    if ( by_name. st_rdev != by_fd. st_rdev )
        return 0;
    else
        return 1;
}


static void motd (void)
{
    FILE *fp;
    register int c;

    if (( fp = fopen ( bb_path_motd_file, "r" ))) {
        while (( c = getc ( fp )) != EOF )
            putchar ( c );
        fclose ( fp );
    }
}


#ifdef CONFIG_FEATURE_UTMP
// vv  Taken from tinylogin utmp.c  vv

#define NO_UTENT \
    "No utmp entry.  You must exec \"login\" from the lowest level \"sh\""
#define NO_TTY \
    "Unable to determine your tty name."

/*
 * checkutmp - see if utmp file is correct for this process
 *
 *  System V is very picky about the contents of the utmp file
 *  and requires that a slot for the current process exist.
 *  The utmp file is scanned for an entry with the same process
 *  ID.  If no entry exists the process exits with a message.
 *
 *  The "picky" flag is for network and other logins that may
 *  use special flags.  It allows the pid checks to be overridden.
 *  This means that getty should never invoke login with any
 *  command line flags.
 */

static void checkutmp(int picky)
{
    char *line;
    struct utmp *ut;
    pid_t pid = getpid();

    setutent();

    /* First, try to find a valid utmp entry for this process.  */
    while ((ut = getutent()))
        if (ut->ut_pid == pid && ut->ut_line[0] && ut->ut_id[0] &&
            (ut->ut_type == LOGIN_PROCESS || ut->ut_type == USER_PROCESS))
            break;

    /* If there is one, just use it, otherwise create a new one.  */
    if (ut) {
        utent = *ut;
    } else {
        time_t t_tmp;
        
        if (picky) {
            puts(NO_UTENT);
            exit(1);
        }
        line = ttyname(0);
        if (!line) {
            puts(NO_TTY);
            exit(1);
        }
        if (strncmp(line, "/dev/", 5) == 0)
            line += 5;
        memset((void *) &utent, 0, sizeof utent);
        utent.ut_type = LOGIN_PROCESS;
        utent.ut_pid = pid;
        strncpy(utent.ut_line, line, sizeof utent.ut_line);
        /* XXX - assumes /dev/tty?? */
        strncpy(utent.ut_id, utent.ut_line + 3, sizeof utent.ut_id);
        strncpy(utent.ut_user, "LOGIN", sizeof utent.ut_user);
        t_tmp = (time_t)utent.ut_time;
        time(&t_tmp);
    }
}

/*
 * setutmp - put a USER_PROCESS entry in the utmp file
 *
 *  setutmp changes the type of the current utmp entry to
 *  USER_PROCESS.  the wtmp file will be updated as well.
 */

static void setutmp(const char *name, const char *line ATTRIBUTE_UNUSED)
{
    time_t t_tmp = (time_t)utent.ut_time;

    utent.ut_type = USER_PROCESS;
    strncpy(utent.ut_user, name, sizeof utent.ut_user);
    time(&t_tmp);
    /* other fields already filled in by checkutmp above */
    setutent();
    pututline(&utent);
    endutent();
#ifdef CONFIG_FEATURE_WTMP
    if (access(bb_path_wtmp_file, R_OK|W_OK) == -1) {
        close(creat(bb_path_wtmp_file, 0664));
    }
    updwtmp(bb_path_wtmp_file, &utent);
#endif
}
#endif /* CONFIG_FEATURE_UTMP */