lcp.c

Unix/Linux NAPT协议解析源码

	if (cishort != PPP_LQR) \
	    goto bad; \
	GETLONG(cilong, p); \
	if (cilong != val) \
	  goto bad; \
    }

    ACKCISHORT(CI_MRU, go->neg_mru, go->mru);
    ACKCILONG(CI_ASYNCMAP, go->neg_asyncmap, go->asyncmap);
    ACKCICHAP(CI_AUTHTYPE, go->neg_chap, PPP_CHAP, go->chap_mdtype);
    ACKCISHORT(CI_AUTHTYPE, !go->neg_chap && go->neg_upap, PPP_PAP);
    ACKCILQR(CI_QUALITY, go->neg_lqr, go->lqr_period);
    ACKCILONG(CI_MAGICNUMBER, go->neg_magicnumber, go->magicnumber);
    ACKCIVOID(CI_PCOMPRESSION, go->neg_pcompression);
    ACKCIVOID(CI_ACCOMPRESSION, go->neg_accompression);

    /*
     * If there are any remaining CIs, then this packet is bad.
     */
    if (len != 0)
	goto bad;
    return (1);
bad:
    LCPDEBUG((LOG_WARNING, "lcp_acki: received bad Ack!"));
    return (0);
}


/*
 * lcp_nakci - Peer has sent a NAK for some of our CIs.
 * This should not modify any state if the Nak is bad
 * or if LCP is in the OPENED state.
 *
 * Returns:
 *	0 - Nak was bad.
 *	1 - Nak was good.
 */
static int
lcp_nakci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    lcp_options *wo = &lcp_wantoptions[f->unit];
    u_char citype, cichar, *next;
    u_short cishort;
    u_int32_t cilong;
    lcp_options no;		/* options we've seen Naks for */
    lcp_options try;		/* options to request next time */
    int looped_back = 0;
    int cilen;

    BZERO(&no, sizeof(no));
    try = *go;

    /*
     * Any Nak'd CIs must be in exactly the same order that we sent.
     * Check packet length and CI length at each step.
     * If we find any deviations, then this packet is bad.
     */
#define NAKCIVOID(opt, neg, code) \
    if (go->neg && \
	len >= CILEN_VOID && \
	p[1] == CILEN_VOID && \
	p[0] == opt) { \
	len -= CILEN_VOID; \
	INCPTR(CILEN_VOID, p); \
	no.neg = 1; \
	code \
    }
#define NAKCICHAP(opt, neg, code) \
    if (go->neg && \
	len >= CILEN_CHAP && \
	p[1] == CILEN_CHAP && \
	p[0] == opt) { \
	len -= CILEN_CHAP; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	GETCHAR(cichar, p); \
	no.neg = 1; \
	code \
    }
#define NAKCISHORT(opt, neg, code) \
    if (go->neg && \
	len >= CILEN_SHORT && \
	p[1] == CILEN_SHORT && \
	p[0] == opt) { \
	len -= CILEN_SHORT; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	no.neg = 1; \
	code \
    }
#define NAKCILONG(opt, neg, code) \
    if (go->neg && \
	len >= CILEN_LONG && \
	p[1] == CILEN_LONG && \
	p[0] == opt) { \
	len -= CILEN_LONG; \
	INCPTR(2, p); \
	GETLONG(cilong, p); \
	no.neg = 1; \
	code \
    }
#define NAKCILQR(opt, neg, code) \
    if (go->neg && \
	len >= CILEN_LQR && \
	p[1] == CILEN_LQR && \
	p[0] == opt) { \
	len -= CILEN_LQR; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	GETLONG(cilong, p); \
	no.neg = 1; \
	code \
    }

    /*
     * We don't care if they want to send us smaller packets than
     * we want.  Therefore, accept any MRU less than what we asked for,
     * but then ignore the new value when setting the MRU in the kernel.
     * If they send us a bigger MRU than what we asked, accept it, up to
     * the limit of the default MRU we'd get if we didn't negotiate.
     */
    NAKCISHORT(CI_MRU, neg_mru,
	       if (cishort <= wo->mru || cishort < DEFMRU)
		   try.mru = cishort;
	       );

    /*
     * Add any characters they want to our (receive-side) asyncmap.
     */
    NAKCILONG(CI_ASYNCMAP, neg_asyncmap,
	      try.asyncmap = go->asyncmap | cilong;
	      );

    /*
     * If they've nak'd our authentication-protocol, check whether
     * they are proposing a different protocol, or a different
     * hash algorithm for CHAP.
     */
    if ((go->neg_chap || go->neg_upap)
	&& len >= CILEN_SHORT
	&& p[0] == CI_AUTHTYPE && p[1] >= CILEN_SHORT) {
	cilen = p[1];
	INCPTR(2, p);
        GETSHORT(cishort, p);
	if (cishort == PPP_PAP && cilen == CILEN_SHORT) {
	    /*
	     * If they are asking for PAP, then they don't want to do CHAP.
	     * If we weren't asking for CHAP, then we were asking for PAP,
	     * in which case this Nak is bad.
	     */
	    if (!go->neg_chap)
		goto bad;
	    go->neg_chap = 0;

	} else if (cishort == PPP_CHAP && cilen == CILEN_CHAP) {
	    GETCHAR(cichar, p);
	    if (go->neg_chap) {
		/*
		 * We were asking for CHAP/MD5; they must want a different
		 * algorithm.  If they can't do MD5, we'll have to stop
		 * asking for CHAP.
		 */
		if (cichar != go->chap_mdtype)
		    go->neg_chap = 0;
	    } else {
		/*
		 * Stop asking for PAP if we were asking for it.
		 */
		go->neg_upap = 0;
	    }

	} else {
	    /*
	     * We don't recognize what they're suggesting.
	     * Stop asking for what we were asking for.
	     */
	    if (go->neg_chap)
		go->neg_chap = 0;
	    else
		go->neg_upap = 0;
	    p += cilen - CILEN_SHORT;
	}
    }

    /*
     * Peer shouldn't send Nak for protocol compression or
     * address/control compression requests; they should send
     * a Reject instead.  If they send a Nak, treat it as a Reject.
     */
    if (!go->neg_chap ){
	NAKCISHORT(CI_AUTHTYPE, neg_upap,
		   try.neg_upap = 0;
		   );
    }

    /*
     * If they can't cope with our link quality protocol, we'll have
     * to stop asking for LQR.  We haven't got any other protocol.
     * If they Nak the reporting period, take their value XXX ?
     */
    NAKCILQR(CI_QUALITY, neg_lqr,
	     if (cishort != PPP_LQR)
		 try.neg_lqr = 0;
	     else
		 try.lqr_period = cilong;
	     );

    /*
     * Check for a looped-back line.
     */
    NAKCILONG(CI_MAGICNUMBER, neg_magicnumber,
	      try.magicnumber = magic();
	      looped_back = 1;
	      );

    NAKCIVOID(CI_PCOMPRESSION, neg_pcompression,
	      try.neg_pcompression = 0;
	      );
    NAKCIVOID(CI_ACCOMPRESSION, neg_accompression,
	      try.neg_accompression = 0;
	      );

    /*
     * There may be remaining CIs, if the peer is requesting negotiation
     * on an option that we didn't include in our request packet.
     * If we see an option that we requested, or one we've already seen
     * in this packet, then this packet is bad.
     * If we wanted to respond by starting to negotiate on the requested
     * option(s), we could, but we don't, because except for the
     * authentication type and quality protocol, if we are not negotiating
     * an option, it is because we were told not to.
     * For the authentication type, the Nak from the peer means
     * `let me authenticate myself with you' which is a bit pointless.
     * For the quality protocol, the Nak means `ask me to send you quality
     * reports', but if we didn't ask for them, we don't want them.
     */
    while (len > CILEN_VOID) {
	GETCHAR(citype, p);
	GETCHAR(cilen, p);
	if( (len -= cilen) < 0 )
	    goto bad;
	next = p + cilen - 2;

	switch (citype) {
	case CI_MRU:
	    if (go->neg_mru || no.neg_mru || cilen != CILEN_SHORT)
		goto bad;
	    break;
	case CI_ASYNCMAP:
	    if (go->neg_asyncmap || no.neg_asyncmap || cilen != CILEN_LONG)
		goto bad;
	    break;
	case CI_AUTHTYPE:
	    if (go->neg_chap || no.neg_chap || go->neg_upap || no.neg_upap)
		goto bad;
	    break;
	case CI_MAGICNUMBER:
	    if (go->neg_magicnumber || no.neg_magicnumber ||
		cilen != CILEN_LONG)
		goto bad;
	    break;
	case CI_PCOMPRESSION:
	    if (go->neg_pcompression || no.neg_pcompression
		|| cilen != CILEN_VOID)
		goto bad;
	    break;
	case CI_ACCOMPRESSION:
	    if (go->neg_accompression || no.neg_accompression
		|| cilen != CILEN_VOID)
		goto bad;
	    break;
	case CI_QUALITY:
	    if (go->neg_lqr || no.neg_lqr || cilen != CILEN_LQR)
		goto bad;
	    break;
	}
	p = next;
    }

    /* If there is still anything left, this packet is bad. */
    if (len != 0)
	goto bad;

    /*
     * OK, the Nak is good.  Now we can update state.
     */
    if (f->state != OPENED) {
	if (looped_back) {
	    if (++try.numloops >= lcp_loopbackfail) {
		do_syslog(LOG_NOTICE, "Serial line is looped back.");
		lcp_close(f->unit);
	    }
	} else
	    try.numloops = 0;
	*go = try;
    }

    return 1;

bad:
    LCPDEBUG((LOG_WARNING, "lcp_nakci: received bad Nak!"));
    return 0;
}


/*
 * lcp_rejci - Peer has Rejected some of our CIs.
 * This should not modify any state if the Reject is bad
 * or if LCP is in the OPENED state.
 *
 * Returns:
 *	0 - Reject was bad.
 *	1 - Reject was good.
 */
static int
lcp_rejci(f, p, len)
    fsm *f;
    u_char *p;
    int len;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    u_char cichar;
    u_short cishort;
    u_int32_t cilong;
    u_char *start = p;
    int plen = len;
    lcp_options try;		/* options to request next time */

    try = *go;

    /*
     * Any Rejected CIs must be in exactly the same order that we sent.
     * Check packet length and CI length at each step.
     * If we find any deviations, then this packet is bad.
     */
#define REJCIVOID(opt, neg) \
    if (go->neg && \
	len >= CILEN_VOID && \
	p[1] == CILEN_VOID && \
	p[0] == opt) { \
	len -= CILEN_VOID; \
	INCPTR(CILEN_VOID, p); \
	try.neg = 0; \
	LCPDEBUG((LOG_INFO, "lcp_rejci rejected void opt %d", opt)); \
    }
#define REJCISHORT(opt, neg, val) \
    if (go->neg && \
	len >= CILEN_SHORT && \
	p[1] == CILEN_SHORT && \
	p[0] == opt) { \
	len -= CILEN_SHORT; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	/* Check rejected value. */ \
	if (cishort != val) \
	    goto bad; \
	try.neg = 0; \
	LCPDEBUG((LOG_INFO,"lcp_rejci rejected short opt %d", opt)); \
    }
#define REJCICHAP(opt, neg, val, digest) \
    if (go->neg && \
	len >= CILEN_CHAP && \
	p[1] == CILEN_CHAP && \
	p[0] == opt) { \
	len -= CILEN_CHAP; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	GETCHAR(cichar, p); \
	/* Check rejected value. */ \
	if (cishort != val || cichar != digest) \
	    goto bad; \
	try.neg = 0; \
	try.neg_upap = 0; \
	LCPDEBUG((LOG_INFO,"lcp_rejci rejected chap opt %d", opt)); \
    }
#define REJCILONG(opt, neg, val) \
    if (go->neg && \
	len >= CILEN_LONG && \
	p[1] == CILEN_LONG && \
	p[0] == opt) { \
	len -= CILEN_LONG; \
	INCPTR(2, p); \
	GETLONG(cilong, p); \
	/* Check rejected value. */ \
	if (cilong != val) \
	    goto bad; \
	try.neg = 0; \
	LCPDEBUG((LOG_INFO,"lcp_rejci rejected long opt %d", opt)); \
    }
#define REJCILQR(opt, neg, val) \
    if (go->neg && \
	len >= CILEN_LQR && \
	p[1] == CILEN_LQR && \
	p[0] == opt) { \
	len -= CILEN_LQR; \
	INCPTR(2, p); \
	GETSHORT(cishort, p); \
	GETLONG(cilong, p); \
	/* Check rejected value. */ \
	if (cishort != PPP_LQR || cilong != val) \
	    goto bad; \
	try.neg = 0; \
	LCPDEBUG((LOG_INFO,"lcp_rejci rejected LQR opt %d", opt)); \
    }

    REJCISHORT(CI_MRU, neg_mru, go->mru);
    REJCILONG(CI_ASYNCMAP, neg_asyncmap, go->asyncmap);
    REJCICHAP(CI_AUTHTYPE, neg_chap, PPP_CHAP, go->chap_mdtype);
    if (!go->neg_chap) {
	REJCISHORT(CI_AUTHTYPE, neg_upap, PPP_PAP);
    }
    REJCILQR(CI_QUALITY, neg_lqr, go->lqr_period);
    REJCILONG(CI_MAGICNUMBER, neg_magicnumber, go->magicnumber);
    REJCIVOID(CI_PCOMPRESSION, neg_pcompression);
    REJCIVOID(CI_ACCOMPRESSION, neg_accompression);

    /*
     * If there are any remaining CIs, then this packet is bad.
     */
    if (len != 0)
	goto bad;
    /*
     * Now we can update state.
     */
    if (f->state != OPENED)
	*go = try;
    return 1;

bad:
    LCPDEBUG((LOG_WARNING, "lcp_rejci: received bad Reject!"));
    LCPDEBUG((LOG_WARNING, "lcp_rejci: plen %d len %d off %d",
	      plen, len, p - start));
    return 0;
}


/*
 * lcp_reqci - Check the peer's requested CIs and send appropriate response.
 *
 * Returns: CONFACK, CONFNAK or CONFREJ and input packet modified
 * appropriately.  If reject_if_disagree is non-zero, doesn't return
 * CONFNAK; returns CONFREJ if it can't return CONFACK.
 */
static int
lcp_reqci(f, inp, lenp, reject_if_disagree)
    fsm *f;
    u_char *inp;		/* Requested CIs */
    int *lenp;			/* Length of requested CIs */
    int reject_if_disagree;
{
    lcp_options *go = &lcp_gotoptions[f->unit];
    lcp_options *ho = &lcp_hisoptions[f->unit];
    lcp_options *ao = &lcp_allowoptions[f->unit];
    u_char *cip, *next;		/* Pointer to current and next CIs */
    u_char cilen, citype, cichar;/* Parsed len, type, char value */
    u_short cishort;		/* Parsed short value */
    u_int32_t cilong;		/* Parse long value */
    int rc = CONFACK;		/* Final packet return code */
    int orc;			/* Individual option return code */
    u_char *p;			/* Pointer to next char to parse */
    u_char *rejp;		/* Pointer to next char in reject frame */
    u_char *nakp;		/* Pointer to next char in Nak frame */
    int l = *lenp;		/* Length left */

    /*
     * Reset all his options.
     */
    BZERO(ho, sizeof(*ho));

    /*
     * Process all his options.
     */
    next = inp;
    nakp = nak_buffer;
    rejp = inp;
    while (l) {
	orc = CONFACK;			/* Assume success */
	cip = p = next;			/* Remember begining of CI */
	if (l < 2 ||			/* Not enough data for CI header or */
	    p[1] < 2 ||			/*  CI length too small or */
	    p[1] > l) {			/*  CI length too big? */
	    LCPDEBUG((LOG_WARNING, "lcp_reqci: bad CI length!"));
	    orc = CONFREJ;		/* Reject bad CI */
	    cilen = l;			/* Reject till end of packet */
	    l = 0;			/* Don't loop again */
	    goto endswitch;
	}
	GETCHAR(citype, p);		/* Parse CI type */
	GETCHAR(cilen, p);		/* Parse CI length */
	l -= cilen;			/* Adjust remaining length */
	next += cilen;			/* Step to next CI */

	switch (citype) {		/* Check CI type */
	case CI_MRU:
	    LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd MRU"));
	    if (!ao->neg_mru ||		/* Allow option? */
		cilen != CILEN_SHORT) {	/* Check CI length */
		orc = CONFREJ;		/* Reject CI */
		break;
	    }
	    GETSHORT(cishort, p);	/* Parse MRU */
	    LCPDEBUG((LOG_INFO, "(%d)", cishort));

	    /*
	     * He must be able to receive at least our minimum.
	     * No need to check a maximum.  If he sends a large number,
	     * we'll just ignore it.
	     */
	    if (cishort < MINMRU) {
		orc = CONFNAK;		/* Nak CI */
		PUTCHAR(CI_MRU, nakp);
		PUTCHAR(CILEN_SHORT, nakp);
		PUTSHORT(MINMRU, nakp);	/* Give him a hint */
		break;
	    }
	    ho->neg_mru = 1;		/* Remember he sent MRU */
	    ho->mru = cishort;		/* And remember value */
	    break;

	case CI_ASYNCMAP:
	    LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd ASYNCMAP"));
	    if (!ao->neg_asyncmap ||
		cilen != CILEN_LONG) {
		orc = CONFREJ;
		break;
	    }
	    GETLONG(cilong, p);
	    LCPDEBUG((LOG_INFO, "(%x)", (unsigned int) cilong));

	    /*
	     * Asyncmap must have set at least the bits
	     * which are set in lcp_allowoptions[unit].asyncmap.
	     */
	    if ((ao->asyncmap & ~cilong) != 0) {
		orc = CONFNAK;
		PUTCHAR(CI_ASYNCMAP, nakp);
		PUTCHAR(CILEN_LONG, nakp);
		PUTLONG(ao->asyncmap | cilong, nakp);
		break;
	    }
	    ho->neg_asyncmap = 1;
	    ho->asyncmap = cilong;
	    break;

	case CI_AUTHTYPE:
	    LCPDEBUG((LOG_INFO, "lcp_reqci: rcvd AUTHTYPE"));
	    if (cilen < CILEN_SHORT ||
		!(ao->neg_upap || ao->neg_chap)) {
		/*
		 * Reject the option if we're not willing to authenticate.
		 */
		orc = CONFREJ;
		break;
	    }
	    GETSHORT(cishort, p);
	    LCPDEBUG((LOG_INFO, "(%x)", cishort));

	    /*
	     * Authtype must be UPAP or CHAP.
	     *
	     * Note: if both ao->neg_upap and ao->neg_chap are set,
	     * and the peer sends a Configure-Request with two
	     * authenticate-protocol requests, one for CHAP and one
	     * for UPAP, then we will reject the second request.
	     * Whether we end up doing CHAP or UPAP depends then on
	     * the ordering of the CIs in the peer's Configure-Request.
	     */

	    if (cishort == PPP_PAP) {
		if (ho->neg_chap ||	/* we've already accepted CHAP */
		    cilen != CILEN_SHORT) {