sys_term.c

这是关于远程登陆TELNET 的源代码 已经测试过的。

/*
 * A table of available terminal speeds
 */
struct termspeeds {
	int	speed;
	int	value;
} termspeeds[] = {
	{ 0,     B0 },    { 50,    B50 },   { 75,    B75 },
	{ 110,   B110 },  { 134,   B134 },  { 150,   B150 },
	{ 200,   B200 },  { 300,   B300 },  { 600,   B600 },
	{ 1200,  B1200 }, { 1800,  B1800 }, { 2400,  B2400 },
	{ 4800,  B4800 }, { 9600,  B9600 }, { 19200, B9600 },
	{ 38400, B9600 }, { -1,    B9600 }
};

void tty_tspeed(int val) {
    struct termspeeds *tp;
    for (tp = termspeeds; (tp->speed != -1) && (val > tp->speed); tp++);
    cfsetospeed(&termbuf, tp->value);
}

void tty_rspeed(int val) {
    struct termspeeds *tp;
    for (tp = termspeeds; (tp->speed != -1) && (val > tp->speed); tp++);
    cfsetispeed(&termbuf, tp->value);
}

/*
 * getptyslave()
 *
 * Open the slave side of the pty, and do any initialization
 * that is necessary.  The return value is a file descriptor
 * for the slave side.
 */
#ifdef	TIOCGWINSZ
extern int def_row, def_col;
#endif
extern int def_tspeed, def_rspeed;

static int getptyslave(void) {
#if 0
    register int t = -1;

# ifdef	LINEMODE
    int waslm;
# endif
# ifdef	TIOCGWINSZ
    struct winsize ws;
# endif
    /*
     * Opening the slave side may cause initilization of the
     * kernel tty structure.  We need remember the state of
     * 	if linemode was turned on
     *	terminal window size
     *	terminal speed
     * so that we can re-set them if we need to.
     */
# ifdef	LINEMODE
    waslm = tty_linemode();
# endif


    /*
     * Make sure that we don't have a controlling tty, and
     * that we are the session (process group) leader.
     */
    t = open(_PATH_TTY, O_RDWR);
    if (t >= 0) {
	ioctl(t, TIOCNOTTY, (char *)0);
	close(t);
    }

    t = cleanopen(line);
    if (t < 0) fatalperror(net, line);
#endif /* 0 */

    struct winsize ws;
    int t = ptyslavefd;

    /*
     * set up the tty modes as we like them to be.
     */
    init_termbuf();
# ifdef	TIOCGWINSZ
    if (def_row || def_col) {
	bzero((char *)&ws, sizeof(ws));
	ws.ws_col = def_col;
	ws.ws_row = def_row;
	ioctl(t, TIOCSWINSZ, (char *)&ws);
    }
# endif

    /*
     * Settings for all other termios/termio based
     * systems, other than 4.4BSD.  In 4.4BSD the
     * kernel does the initial terminal setup.
     *
     * XXX what about linux?
     */
#  ifndef	OXTABS
#   define OXTABS	0
#  endif
    termbuf.c_lflag |= ECHO;
    termbuf.c_oflag |= OPOST|ONLCR|OXTABS;
    termbuf.c_iflag |= ICRNL;
    termbuf.c_iflag &= ~IXOFF;

    tty_rspeed((def_rspeed > 0) ? def_rspeed : 9600);
    tty_tspeed((def_tspeed > 0) ? def_tspeed : 9600);
# ifdef	LINEMODE
    if (waslm) tty_setlinemode(1);
# endif	/* LINEMODE */

    /*
     * Set the tty modes, and make this our controlling tty.
     */
    set_termbuf();
    if (login_tty(t) == -1) fatalperror(net, "login_tty");

    if (net > 2) close(net);
    if (pty > 2) close(pty);
    return t;
}

#if 0
#ifndef	O_NOCTTY
#define	O_NOCTTY	0
#endif
/*
 * Open the specified slave side of the pty,
 * making sure that we have a clean tty.
 */
static int cleanopen(char *lyne) {
    register int t;

    /*
     * Make sure that other people can't open the
     * slave side of the connection.
     */
    chown(lyne, 0, 0);
    chmod(lyne, 0600);

#ifndef NO_REVOKE
    revoke(lyne);
#endif

    t = open(lyne, O_RDWR|O_NOCTTY);
    if (t < 0) return(-1);

    /*
     * Hangup anybody else using this ttyp, then reopen it for
     * ourselves.
     */
# if !defined(__linux__)
    /* this looks buggy to me, our ctty is really a pty at this point */
    signal(SIGHUP, SIG_IGN);
    vhangup();
    signal(SIGHUP, SIG_DFL);
    t = open(lyne, O_RDWR|O_NOCTTY);
    if (t < 0) return(-1);
# endif
    return(t);
}
#endif /* 0 */

int login_tty(int t) {
    if (setsid() < 0) fatalperror(net, "setsid()");
    if (ioctl(t, TIOCSCTTY, (char *)0) < 0) {
	fatalperror(net, "ioctl(sctty)");
    }
    if (t != 0) dup2(t, 0);
    if (t != 1) dup2(t, 1);
    if (t != 2) dup2(t, 2);
    if (t > 2) close(t);
    return 0;
}

/*
 * startslave(host)
 *
 * Given a hostname, do whatever
 * is necessary to startup the login process on the slave side of the pty.
 */

/* ARGSUSED */
void startslave(const char *host, int autologin, char *autoname) {
    int i;

#if defined(AUTHENTICATE)
    if (!autoname || !autoname[0]) autologin = 0;
    if (autologin < auth_level) {
	fatal(net, "Authorization failed");
	exit(1);
    }
#endif

    i = fork();
    if (i < 0) fatalperror(net, "fork");
    if (i) {
	/* parent */
	signal(SIGHUP,SIG_IGN);
	close(ptyslavefd);
    } 
    else {
	/* child */
	signal(SIGHUP,SIG_IGN);
	getptyslave();
	start_login(host, autologin, autoname);
	/*NOTREACHED*/
    }
}

char *envinit[3];

void init_env(void) {
    char **envp;
    envp = envinit;
    if ((*envp = getenv("TZ"))!=NULL)
	*envp++ -= 3;
    *envp = 0;
    environ = envinit;
}

/*
 * start_login(host)
 *
 * Assuming that we are now running as a child processes, this
 * function will turn us into the login process.
 */

struct argv_stuff {
   const char **argv;
   int argc;
   int argmax;
};

static void addarg(struct argv_stuff *, const char *);
static void initarg(struct argv_stuff *);

void start_login(const char *host, int autologin, const char *name) {
    struct argv_stuff avs;
    char *const *argvfoo;
    (void)autologin;

    initarg(&avs);

    /*
     * -h : pass on name of host.
     *		WARNING:  -h is accepted by login if and only if
     *			getuid() == 0.
     * -p : don't clobber the environment (so terminal type stays set).
     *
     * -f : force this login, he has already been authenticated
     */
    addarg(&avs, loginprg);
    addarg(&avs, "-h");
    addarg(&avs, host);
#if !defined(NO_LOGIN_P)
    addarg(&avs, "-p");
#endif
#ifdef BFTPDAEMON
    /*
     * Are we working as the bftp daemon?  If so, then ask login
     * to start bftp instead of shell.
     */
    if (bftpd) {
	addarg(&avs, "-e");
	addarg(&avs, BFTPPATH);
    } 
    else
#endif
    {
#if defined (SecurID)
	/*
	 * don't worry about the -f that might get sent.
	 * A -s is supposed to override it anyhow.
	 */
	if (require_SecurID) addarg(&avs, "-s");
#endif
	if (*name=='-') {
	    syslog(LOG_ERR, "Attempt to login with an option!");
	    name = "";
	}
#if defined (AUTHENTICATE)
	if (auth_level >= 0 && autologin == AUTH_VALID) {
# if !defined(NO_LOGIN_F)
	    addarg(&avs, "-f");
# endif
	    addarg(&avs, name);
	} 
	else
#endif
	{
	    if (getenv("USER")) {
		addarg(&avs, getenv("USER"));
		if (*getenv("USER") == '-') {
		    write(1,"I don't hear you!\r\n",19);
		    syslog(LOG_ERR,"Attempt to login with an option!");
		    exit(1);
		}
	    }
	}
    }
    closelog();
    /* execv() should really take char const* const *, but it can't */ 
    /*argvfoo = argv*/;
    memcpy(&argvfoo, &avs.argv, sizeof(argvfoo));
    execv(loginprg, argvfoo);

    syslog(LOG_ERR, "%s: %m\n", loginprg);
    fatalperror(net, loginprg);
}

static void initarg(struct argv_stuff *avs) {
   /*
    * 10 entries and a null
    */
   avs->argmax = 11;
   avs->argv = malloc(sizeof(avs->argv[0]) * avs->argmax);
   if (avs->argv == NULL) {
      fprintf(stderr, "Out of memory\n");
      exit(1);
   }
   avs->argc = 0;
   avs->argv[0] = NULL;
}

static void addarg(struct argv_stuff *avs, const char *val) {
   if (avs->argc>=avs->argmax-1) {
       avs->argmax += 10;
       avs->argv = realloc(avs->argv, sizeof(avs->argv[0])*avs->argmax);
       if (avs->argv == NULL) {
	  fprintf(stderr, "Out of memory\n");
	  exit(1);
       }
   }

   avs->argv[avs->argc++] = val;
   avs->argv[avs->argc] = NULL;
}

/*
 * cleanup()
 *
 * This is the routine to call when we are all through, to
 * clean up anything that needs to be cleaned up.
 */
void cleanup(int sig) {
    char *p;
    (void)sig;

    p = line + sizeof("/dev/") - 1;
    if (logout(p)) logwtmp(p, "", "");
#ifdef PARANOID_TTYS
    /*
     * dholland 16-Aug-96 chmod the tty when not in use
     * This will make it harder to attach unwanted stuff to it
     * (which is a security risk) but will break some programs.
     */
    chmod(line, 0600);
#else
    chmod(line, 0666);
#endif
    chown(line, 0, 0);
    *p = 'p';
    chmod(line, 0666);
    chown(line, 0, 0);
    shutdown(net, 2);
    exit(0);
}