res_comp.c

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/*
 * Copyright (c) 1985 Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms are permitted provided
 * that: (1) source distributions retain this entire copyright notice and
 * comment, and (2) distributions including binaries display the following
 * acknowledgement:  ``This product includes software developed by the
 * University of California, Berkeley and its contributors'' in the
 * documentation or other materials provided with the distribution and in
 * all advertising materials mentioning features or use of this software.
 * 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 ``AS IS'' AND WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)res_comp.c  6.18 (Berkeley) 6/27/90";
#endif /* LIBC_SCCS and not lint */

#if _MINIX
#include <sys/types.h>
#include <stdlib.h>

#include <net/gen/in.h>
#include <net/gen/nameser.h>
#include <net/gen/resolv.h>

static int dn_find _ARGS(( const u_char *exp_dn, const u_char *msg,
        u_char **dnptrs, u_char **lastdnptr ));
int dn_skipname _ARGS(( const u_char *comp_dn, const u_char *eom ));

#define getshort _getshort
#define getlong _getlong
#define putshort __putshort
#define putlong __putlong
#else
#include <sys/types.h>
#include <stdio.h>
#include <arpa/nameser.h>

static dn_find();
#endif

#ifdef __STDC__
#define CONST   const
#else
#define CONST
#endif

/*
 * Expand compressed domain name 'comp_dn' to full domain name.
 * 'msg' is a pointer to the begining of the message,
 * 'eomorig' points to the first location after the message,
 * 'exp_dn' is a pointer to a buffer of size 'length' for the result.
 * Return size of compressed name or -1 if there was an error.
 */
dn_expand(msg, eomorig, comp_dn, exp_dn, length)
        CONST u_char *msg, *eomorig, *comp_dn;
        u_char *exp_dn;
        int length;
{
        register CONST u_char *cp;
        register u_char *dn;
        register int n, c;
        CONST u_char *eom;
        int len = -1, checked = 0;

        dn = exp_dn;
        cp = comp_dn;
        eom = exp_dn + length;
        /*
         * fetch next label in domain name
         */
        while (n = *cp++) {
                /*
                 * Check for indirection
                 */
                switch (n & INDIR_MASK) {
                case 0:
                        if (dn != exp_dn) {
                                if (dn >= eom)
                                        return (-1);
                                *dn++ = '.';
                        }
                        if (dn+n >= eom)
                                return (-1);
                        checked += n + 1;
                        while (--n >= 0) {
                                if ((c = *cp++) == '.') {
                                        if (dn + n + 2 >= eom)
                                                return (-1);
                                        *dn++ = '\\';
                                }
                                *dn++ = c;
                                if (cp >= eomorig)      /* out of range */
                                        return(-1);
                        }
                        break;

                case INDIR_MASK:
                        if (len < 0)
                                len = cp - comp_dn + 1;
                        cp = msg + (((n & 0x3f) << 8) | (*cp & 0xff));
                        if (cp < msg || cp >= eomorig)  /* out of range */
                                return(-1);
                        checked += 2;
                        /*
                         * Check for loops in the compressed name;
                         * if we've looked at the whole message,
                         * there must be a loop.
                         */
                        if (checked >= eomorig - msg)
                                return (-1);
                        break;

                default:
                        return (-1);                    /* flag error */
                }
        }
        *dn = '\0';
        if (len < 0)
                len = cp - comp_dn;
        return (len);
}

/*
 * Compress domain name 'exp_dn' into 'comp_dn'.
 * Return the size of the compressed name or -1.
 * 'length' is the size of the array pointed to by 'comp_dn'.
 * 'dnptrs' is a list of pointers to previous compressed names. dnptrs[0]
 * is a pointer to the beginning of the message. The list ends with NULL.
 * 'lastdnptr' is a pointer to the end of the arrary pointed to
 * by 'dnptrs'. Side effect is to update the list of pointers for
 * labels inserted into the message as we compress the name.
 * If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
 * is NULL, we don't update the list.
 */
int
dn_comp(exp_dn, comp_dn, length, dnptrs, lastdnptr)
        CONST u_char *exp_dn;
        u_char *comp_dn;
        int length;
        u_char **dnptrs, **lastdnptr;
{
        register u_char *cp;
        register CONST u_char *dn;
        register int c, l;
        u_char **cpp, **lpp, *sp, *eob;
        u_char *msg;

        dn = exp_dn;
        cp = comp_dn;
        eob = cp + length;
        if (dnptrs != NULL) {
                if ((msg = *dnptrs++) != NULL) {
                        for (cpp = dnptrs; *cpp != NULL; cpp++)
                                ;
                        lpp = cpp;      /* end of list to search */
                }
        } else
                msg = NULL;
        for (c = *dn++; c != '\0'; ) {
                /* look to see if we can use pointers */
                if (msg != NULL) {
                        if ((l = dn_find(dn-1, msg, dnptrs, lpp)) >= 0) {
                                if (cp+1 >= eob)
                                        return (-1);
                                *cp++ = (l >> 8) | INDIR_MASK;
                                *cp++ = l % 256;
                                return (cp - comp_dn);
                        }
                        /* not found, save it */
                        if (lastdnptr != NULL && cpp < lastdnptr-1) {
                                *cpp++ = cp;
                                *cpp = NULL;
                        }
                }
                sp = cp++;      /* save ptr to length byte */
                do {
                        if (c == '.') {
                                c = *dn++;
                                break;
                        }
                        if (c == '\\') {
                                if ((c = *dn++) == '\0')
                                        break;
                        }
                        if (cp >= eob) {
                                if (msg != NULL)
                                        *lpp = NULL;
                                return (-1);
                        }
                        *cp++ = c;
                } while ((c = *dn++) != '\0');
                /* catch trailing '.'s but not '..' */
                if ((l = cp - sp - 1) == 0 && c == '\0') {
                        cp--;
                        break;
                }
                if (l <= 0 || l > MAXLABEL) {
                        if (msg != NULL)
                                *lpp = NULL;
                        return (-1);
                }
                *sp = l;
        }
        if (cp >= eob) {
                if (msg != NULL)
                        *lpp = NULL;
                return (-1);
        }
        *cp++ = '\0';
        return (cp - comp_dn);
}

/*
 * Skip over a compressed domain name. Return the size or -1.
 */
dn_skipname(comp_dn, eom)
        CONST u_char *comp_dn, *eom;
{
        register CONST u_char *cp;
        register int n;

        cp = comp_dn;
        while (cp < eom && (n = *cp++)) {
                /*
                 * check for indirection
                 */
                switch (n & INDIR_MASK) {
                case 0:         /* normal case, n == len */
                        cp += n;
                        continue;
                default:        /* illegal type */
                        return (-1);
                case INDIR_MASK:        /* indirection */
                        cp++;
                }
                break;
        }
        return (cp - comp_dn);
}

/*
 * Search for expanded name from a list of previously compressed names.
 * Return the offset from msg if found or -1.
 * dnptrs is the pointer to the first name on the list,
 * not the pointer to the start of the message.
 */
static int
dn_find(exp_dn, msg, dnptrs, lastdnptr)
        CONST u_char *exp_dn, *msg;
        u_char **dnptrs, **lastdnptr;
{
        CONST register u_char *dn, *cp;
        register u_char **cpp;
        register int n;
        CONST u_char *sp;

        for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
                dn = exp_dn;
                sp = cp = *cpp;
                while (n = *cp++) {
                        /*
                         * check for indirection
                         */
                        switch (n & INDIR_MASK) {
                        case 0:         /* normal case, n == len */
                                while (--n >= 0) {
                                        if (*dn == '.')
                                                goto next;
                                        if (*dn == '\\')
                                                dn++;
                                        if (*dn++ != *cp++)
                                                goto next;
                                }
                                if ((n = *dn++) == '\0' && *cp == '\0')
                                        return (sp - msg);
                                if (n == '.')
                                        continue;
                                goto next;

                        default:        /* illegal type */
                                return (-1);

                        case INDIR_MASK:        /* indirection */
                                cp = msg + (((n & 0x3f) << 8) | *cp);
                        }
                }
                if (*dn == '\0')
                        return (sp - msg);
        next:   ;
        }
        return (-1);
}

/*
 * Routines to insert/extract short/long's. Must account for byte
 * order and non-alignment problems. This code at least has the
 * advantage of being portable.
 *
 * used by sendmail.
 */

u16_t
getshort(msgp)
        CONST u8_t *msgp;
{
        return ((msgp[0] << 8) | (msgp[1] << 0));
}

u32_t
getlong(msgp)
        CONST u8_t *msgp;
{
        return (  ((u32_t) msgp[0] << 24)
                | ((u32_t) msgp[1] << 16)
                | ((u32_t) msgp[2] <<  8)
                | ((u32_t) msgp[3] <<  0));
}


void
putshort(s, msgp)
        register U16_t s;
        register u8_t *msgp;
{

        msgp[1] = s;
        msgp[0] = s >> 8;
}

void
putlong(l, msgp)
        register u32_t l;
        register u8_t *msgp;
{

        msgp[3] = l;
        msgp[2] = (l >>= 8);
        msgp[1] = (l >>= 8);
        msgp[0] = l >> 8;
}

---