utility.c

经典的unix下telnetd代码

/*
 * Copyright (c) 1989, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#define PRINTOPTIONS
#include "telnetd.h"

/* RCSID("$KTH: utility.c,v 1.25 2001/05/17 00:34:42 assar Exp $"); */

/*
 * utility functions performing io related tasks
 */

/*
 * ttloop
 *
 * A small subroutine to flush the network output buffer, get some
 * data from the network, and pass it through the telnet state
 * machine.  We also flush the pty input buffer (by dropping its data)
 * if it becomes too full.
 *
 * return 0 if OK or 1 if interrupted by a signal.
 */

int
ttloop(void)
{
    void netflush(void);
    
    DIAG(TD_REPORT, {
	output_data("td: ttloop\r\n");
    });
    if (nfrontp-nbackp)
	netflush();
    ncc = read(net, netibuf, sizeof netibuf);
    if (ncc < 0) {
	if (errno == EINTR)
	    return 1;
	syslog(LOG_INFO, "ttloop:  read: %m");
	exit(1);
    } else if (ncc == 0) {
	syslog(LOG_INFO, "ttloop:  peer died");
	exit(1);
    }
    DIAG(TD_REPORT, {
	output_data("td: ttloop read %d chars\r\n", ncc);
    });
    netip = netibuf;
    telrcv();			/* state machine */
    if (ncc > 0) {
	pfrontp = pbackp = ptyobuf;
	telrcv();
    }
    return 0;
}  /* end of ttloop */

/*
 * Check a descriptor to see if out of band data exists on it.
 */
int
stilloob(int s)
{
    static struct timeval timeout = { 0 };
    fd_set	excepts;
    int value;

    if (s >= FD_SETSIZE)
	fatal(ourpty, "fd too large");

    do {
	FD_ZERO(&excepts);
	FD_SET(s, &excepts);
	value = select(s+1, 0, 0, &excepts, &timeout);
    } while ((value == -1) && (errno == EINTR));

    if (value < 0) {
	fatalperror(ourpty, "select");
    }
    if (FD_ISSET(s, &excepts)) {
	return 1;
    } else {
	return 0;
    }
}

void
ptyflush(void)
{
    int n;

    if ((n = pfrontp - pbackp) > 0) {
	DIAG((TD_REPORT | TD_PTYDATA), { 
	    output_data("td: ptyflush %d chars\r\n", n);
	});
	DIAG(TD_PTYDATA, printdata("pd", pbackp, n));
	n = write(ourpty, pbackp, n);
    }
    if (n < 0) {
	if (errno == EWOULDBLOCK || errno == EINTR)
	    return;
	cleanup(0);
    }
    pbackp += n;
    if (pbackp == pfrontp)
	pbackp = pfrontp = ptyobuf;
}

/*
 * nextitem()
 *
 *	Return the address of the next "item" in the TELNET data
 * stream.  This will be the address of the next character if
 * the current address is a user data character, or it will
 * be the address of the character following the TELNET command
 * if the current address is a TELNET IAC ("I Am a Command")
 * character.
 */
char *
nextitem(char *current)
{
    if ((*current&0xff) != IAC) {
	return current+1;
    }
    switch (*(current+1)&0xff) {
    case DO:
    case DONT:
    case WILL:
    case WONT:
	return current+3;
    case SB:{
	/* loop forever looking for the SE */
	char *look = current+2;

	for (;;) {
	    if ((*look++&0xff) == IAC) {
		if ((*look++&0xff) == SE) {
		    return look;
		}
	    }
	}
    }
    default:
	return current+2;
    }
}


/*
 * netclear()
 *
 *	We are about to do a TELNET SYNCH operation.  Clear
 * the path to the network.
 *
 *	Things are a bit tricky since we may have sent the first
 * byte or so of a previous TELNET command into the network.
 * So, we have to scan the network buffer from the beginning
 * until we are up to where we want to be.
 *
 *	A side effect of what we do, just to keep things
 * simple, is to clear the urgent data pointer.  The principal
 * caller should be setting the urgent data pointer AFTER calling
 * us in any case.
 */
void
netclear(void)
{
    char *thisitem, *next;
    char *good;
#define	wewant(p)	((nfrontp > p) && ((*p&0xff) == IAC) && \
			 ((*(p+1)&0xff) != EC) && ((*(p+1)&0xff) != EL))

#ifdef ENCRYPTION
	thisitem = nclearto > netobuf ? nclearto : netobuf;
#else
	thisitem = netobuf;
#endif

	while ((next = nextitem(thisitem)) <= nbackp) {
	    thisitem = next;
	}

	/* Now, thisitem is first before/at boundary. */

#ifdef ENCRYPTION
	good = nclearto > netobuf ? nclearto : netobuf;
#else
	good = netobuf;	/* where the good bytes go */
#endif

	while (nfrontp > thisitem) {
	    if (wewant(thisitem)) {
		int length;

		next = thisitem;
		do {
		    next = nextitem(next);
		} while (wewant(next) && (nfrontp > next));
		length = next-thisitem;
		memmove(good, thisitem, length);
		good += length;
		thisitem = next;
	    } else {
		thisitem = nextitem(thisitem);
	    }
	}

	nbackp = netobuf;
	nfrontp = good;		/* next byte to be sent */
	neturg = 0;
}  /* end of netclear */

/*
 *  netflush
 *		Send as much data as possible to the network,
 *	handling requests for urgent data.
 */
void
netflush(void)
{
    int n;
    extern int not42;

    if ((n = nfrontp - nbackp) > 0) {
	DIAG(TD_REPORT,
	     { n += output_data("td: netflush %d chars\r\n", n);
	     });
#ifdef ENCRYPTION
	if (encrypt_output) {
	    char *s = nclearto ? nclearto : nbackp;
	    if (nfrontp - s > 0) {
		(*encrypt_output)((unsigned char *)s, nfrontp-s);
		nclearto = nfrontp;
	    }
	}
#endif
	/*
	 * if no urgent data, or if the other side appears to be an
	 * old 4.2 client (and thus unable to survive TCP urgent data),
	 * write the entire buffer in non-OOB mode.
	 */
#if 1 /* remove this to make it work between solaris 2.6 and linux */
	if ((neturg == 0) || (not42 == 0)) {
#endif
	    n = write(net, nbackp, n);	/* normal write */
#if 1 /* remove this to make it work between solaris 2.6 and linux */
	} else {
	    n = neturg - nbackp;
	    /*
	     * In 4.2 (and 4.3) systems, there is some question about
	     * what byte in a sendOOB operation is the "OOB" data.
	     * To make ourselves compatible, we only send ONE byte
	     * out of band, the one WE THINK should be OOB (though
	     * we really have more the TCP philosophy of urgent data
	     * rather than the Unix philosophy of OOB data).
	     */
	    if (n > 1) {
		n = send(net, nbackp, n-1, 0);	/* send URGENT all by itself */
	    } else {
		n = send(net, nbackp, n, MSG_OOB);	/* URGENT data */
	    }
	}
#endif
    }
    if (n < 0) {
	if (errno == EWOULDBLOCK || errno == EINTR)
	    return;
	cleanup(0);
    }
    nbackp += n;
#ifdef ENCRYPTION
    if (nbackp > nclearto)
	nclearto = 0;
#endif
    if (nbackp >= neturg) {
	neturg = 0;
    }
    if (nbackp == nfrontp) {
	nbackp = nfrontp = netobuf;
#ifdef ENCRYPTION
	nclearto = 0;
#endif
    }
    return;
}


/*
 * writenet
 *
 * Just a handy little function to write a bit of raw data to the net.
 * It will force a transmit of the buffer if necessary
 *
 * arguments
 *    ptr - A pointer to a character string to write
 *    len - How many bytes to write
 */
void
writenet(unsigned char *ptr, int len)
{
    /* flush buffer if no room for new data) */
    while ((&netobuf[BUFSIZ] - nfrontp) < len) {
	/* if this fails, don't worry, buffer is a little big */
	netflush();
    }

    memmove(nfrontp, ptr, len);
    nfrontp += len;
}


/*
 * miscellaneous functions doing a variety of little jobs follow ...
 */


void fatal(int f, char *msg)
{
    char buf[BUFSIZ];

    snprintf(buf, sizeof(buf), "telnetd: %s.\r\n", msg);
#ifdef ENCRYPTION
    if (encrypt_output) {
	/*
	 * Better turn off encryption first....
	 * Hope it flushes...
	 */
	encrypt_send_end();
	netflush();
    }
#endif
    write(f, buf, (int)strlen(buf));
    sleep(1);	/*XXX*/
    exit(1);
}

void
fatalperror_errno(int f, const char *msg, int error)
{
    char buf[BUFSIZ];
    
    snprintf(buf, sizeof(buf), "%s: %s", msg, strerror(error));
    fatal(f, buf);
}

void
fatalperror(int f, const char *msg)
{
    fatalperror_errno(f, msg, errno);
}

char editedhost[32];

void edithost(char *pat, char *host)
{
    char *res = editedhost;

    if (!pat)
	pat = "";
    while (*pat) {
	switch (*pat) {

	case '#':
	    if (*host)
		host++;
	    break;

	case '@':
	    if (*host)
		*res++ = *host++;
	    break;

	default:
	    *res++ = *pat;
	    break;
	}
	if (res == &editedhost[sizeof editedhost - 1]) {
	    *res = '\0';
	    return;
	}
	pat++;
    }
    if (*host)
	strlcpy (res, host,
			 sizeof editedhost - (res - editedhost));
    else
	*res = '\0';
    editedhost[sizeof editedhost - 1] = '\0';
}

static char *putlocation;

void
putstr(char *s)
{

    while (*s)
	putchr(*s++);
}

void
putchr(int cc)
{
    *putlocation++ = cc;
}

/*
 * This is split on two lines so that SCCS will not see the M
 * between two % signs and expand it...
 */
static char fmtstr[] = { "%l:%M" "%P on %A, %d %B %Y" };

void putf(char *cp, char *where)
{
#ifdef HAVE_UNAME
    struct utsname name;
#endif
    char *slash;
    time_t t;
    char db[100];

    /* if we don't have uname, set these to sensible values */
    char *sysname = "Unix", 
	*machine = "", 
	*release = "",
	*version = ""; 

#ifdef HAVE_UNAME
    uname(&name);
    sysname=name.sysname;
    machine=name.machine;
    release=name.release;
    version=name.version;
#endif

    putlocation = where;

    while (*cp) {
	if (*cp != '%') {
	    putchr(*cp++);
	    continue;
	}
	switch (*++cp) {

	case 't':
#ifdef	STREAMSPTY
	    /* names are like /dev/pts/2 -- we want pts/2 */
	    slash = strchr(line+1, '/');
#else
	    slash = strrchr(line, '/');
#endif
	    if (slash == (char *) 0)
		putstr(line);
	    else
		putstr(&slash[1]);
	    break;

	case 'h':
	    putstr(editedhost);
	    break;

	case 's':
	    putstr(sysname);
	    break;

	case 'm':
	    putstr(machine);
	    break;

	case 'r':
	    putstr(release);
	    break;

	case 'v':
	    putstr(version);
	    break;

	case 'd':
	    time(&t);
	    strftime(db, sizeof(db), fmtstr, localtime(&t));
	    putstr(db);
	    break;

	case '%':
	    putchr('%');
	    break;
	}
	cp++;
    }
}

#ifdef DIAGNOSTICS
/*
 * Print telnet options and commands in plain text, if possible.
 */
void
printoption(char *fmt, int option)
{
    if (TELOPT_OK(option))
	output_data("%s %s\r\n",
		    fmt,
		    TELOPT(option));
    else if (TELCMD_OK(option))
	output_data("%s %s\r\n",
		    fmt,
		    TELCMD(option));
    else
	output_data("%s %d\r\n",
		    fmt,
		    option);
    return;
}

void
printsub(int direction, unsigned char *pointer, int length)
        		          	/* '<' or '>' */
                 	         	/* where suboption data sits */
       			       		/* length of suboption data */
{
    int i = 0;
#ifdef AUTHENTICATION
    unsigned char buf[512];
#endif

    if (!(diagnostic & TD_OPTIONS))
	return;

    if (direction) {
	output_data("td: %s suboption ",
		    direction == '<' ? "recv" : "send");
	if (length >= 3) {
	    int j;

	    i = pointer[length-2];
	    j = pointer[length-1];

	    if (i != IAC || j != SE) {
		output_data("(terminated by ");
		if (TELOPT_OK(i))
		    output_data("%s ",
				TELOPT(i));
		else if (TELCMD_OK(i))
		    output_data("%s ",
				TELCMD(i));
		else
		    output_data("%d ",
				i);
		if (TELOPT_OK(j))
		    output_data("%s",
				TELOPT(j));
		else if (TELCMD_OK(j))
		    output_data("%s",
				TELCMD(j));
		else
		    output_data("%d",
				j);
		output_data(", not IAC SE!) ");
	    }
	}
	length -= 2;
    }