common/nameser/ns_name.c

/*
 * Copyright (c) 2004 by Internet Systems Consortium, Inc. ("ISC")
 * Copyright (c) 1996,1999 by Internet Software Consortium.
 *
 * Permission to use, copy, modify, and distribute this software for any
 * purpose with or without fee is hereby granted, provided that the above
 * copyright notice and this permission notice appear in all copies.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES
 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS.  IN NO EVENT SHALL ISC BE LIABLE FOR
 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
 * OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 */

#ifndef lint
static const char rcsid[] = "$Id: ns_name.c,v 1.11 2009/01/23 19:59:16 each Exp $";
#endif

#include "port_before.h"

#include <sys/types.h>

#include <netinet/in.h>
#include <arpa/nameser.h>

#include <errno.h>
#include <resolv.h>
#include <string.h>
#include <ctype.h>
#include <stdlib.h>
#include <limits.h>

#include "port_after.h"

#ifdef SPRINTF_CHAR
# define SPRINTF(x) strlen(sprintf/**/x)
#else
# define SPRINTF(x) ((size_t)sprintf x)
#endif

#define NS_TYPE_ELT         0x40 /*%< EDNS0 extended label type */
#define DNS_LABELTYPE_BITSTRING     0x41

/* Data. */

static const char   digits[] = "0123456789";

static const char digitvalue[256] = {
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*16*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*32*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*48*/
     0,  1,  2,  3,  4,  5,  6,  7,  8,  9, -1, -1, -1, -1, -1, -1, /*64*/
    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*80*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*96*/
    -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*112*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*128*/
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /*256*/
};

/* Forward. */

static int      special(int);
static int      printable(int);
static int      dn_find(const u_char *, const u_char *,
                const u_char * const *,
                const u_char * const *);
static int      encode_bitsring(const char **, const char *,
                    unsigned char **, unsigned char **,
                    unsigned const char *);
static int      labellen(const u_char *);
static int      decode_bitstring(const unsigned char **,
                     char *, const char *);

/* Public. */

/*%
 *  Convert an encoded domain name to printable ascii as per RFC1035.

 * return:
 *\li   Number of bytes written to buffer, or -1 (with errno set)
 *
 * notes:
 *\li   The root is returned as "."
 *\li   All other domains are returned in non absolute form
 */
int
ns_name_ntop(const u_char *src, char *dst, size_t dstsiz)
{
    const u_char *cp;
    char *dn, *eom;
    u_char c;
    u_int n;
    int l;

    cp = src;
    dn = dst;
    eom = dst + dstsiz;

    while ((n = *cp++) != 0) {
        if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
            /* Some kind of compression pointer. */
            errno = EMSGSIZE;
            return (-1);
        }
        if (dn != dst) {
            if (dn >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            *dn++ = '.';
        }
        if ((l = labellen(cp - 1)) < 0) {
            errno = EMSGSIZE; /*%< XXX */
            return (-1);
        }
        if (dn + l >= eom) {
            errno = EMSGSIZE;
            return (-1);
        }
        if ((n & NS_CMPRSFLGS) == NS_TYPE_ELT) {
            int m;

            if (n != DNS_LABELTYPE_BITSTRING) {
                /* XXX: labellen should reject this case */
                errno = EINVAL;
                return (-1);
            }
            if ((m = decode_bitstring(&cp, dn, eom)) < 0)
            {
                errno = EMSGSIZE;
                return (-1);
            }
            dn += m;
            continue;
        }
        for ((void)NULL; l > 0; l--) {
            c = *cp++;
            if (special(c)) {
                if (dn + 1 >= eom) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                *dn++ = '\\';
                *dn++ = (char)c;
            } else if (!printable(c)) {
                if (dn + 3 >= eom) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                *dn++ = '\\';
                *dn++ = digits[c / 100];
                *dn++ = digits[(c % 100) / 10];
                *dn++ = digits[c % 10];
            } else {
                if (dn >= eom) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                *dn++ = (char)c;
            }
        }
    }
    if (dn == dst) {
        if (dn >= eom) {
            errno = EMSGSIZE;
            return (-1);
        }
        *dn++ = '.';
    }
    if (dn >= eom) {
        errno = EMSGSIZE;
        return (-1);
    }
    *dn++ = '\0';
    return (dn - dst);
}

/*%
 *  Convert a ascii string into an encoded domain name as per RFC1035.
 *
 * return:
 *
 *\li   -1 if it fails
 *\li   1 if string was fully qualified
 *\li   0 is string was not fully qualified
 *
 * notes:
 *\li   Enforces label and domain length limits.
 */
int
ns_name_pton(const char *src, u_char *dst, size_t dstsiz) {
    return (ns_name_pton2(src, dst, dstsiz, NULL));
}

/*
 * ns_name_pton2(src, dst, dstsiz, *dstlen)
 *  Convert a ascii string into an encoded domain name as per RFC1035.
 * return:
 *  -1 if it fails
 *  1 if string was fully qualified
 *  0 is string was not fully qualified
 * side effects:
 *  fills in *dstlen (if non-NULL)
 * notes:
 *  Enforces label and domain length limits.
 */
int
ns_name_pton2(const char *src, u_char *dst, size_t dstsiz, size_t *dstlen) {
    u_char *label, *bp, *eom;
    int c, n, escaped, e = 0;
    char *cp;

    escaped = 0;
    bp = dst;
    eom = dst + dstsiz;
    label = bp++;

    while ((c = *src++) != 0) {
        if (escaped) {
            if (c == '[') { /*%< start a bit string label */
                if ((cp = strchr(src, ']')) == NULL) {
                    errno = EINVAL; /*%< ??? */
                    return (-1);
                }
                if ((e = encode_bitsring(&src, cp + 2,
                             &label, &bp, eom))
                    != 0) {
                    errno = e;
                    return (-1);
                }
                escaped = 0;
                label = bp++;
                if ((c = *src++) == 0)
                    goto done;
                else if (c != '.') {
                    errno = EINVAL;
                    return  (-1);
                }
                continue;
            }
            else if ((cp = strchr(digits, c)) != NULL) {
                n = (cp - digits) * 100;
                if ((c = *src++) == 0 ||
                    (cp = strchr(digits, c)) == NULL) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                n += (cp - digits) * 10;
                if ((c = *src++) == 0 ||
                    (cp = strchr(digits, c)) == NULL) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                n += (cp - digits);
                if (n > 255) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                c = n;
            }
            escaped = 0;
        } else if (c == '\\') {
            escaped = 1;
            continue;
        } else if (c == '.') {
            c = (bp - label - 1);
            if ((c & NS_CMPRSFLGS) != 0) {  /*%< Label too big. */
                errno = EMSGSIZE;
                return (-1);
            }
            if (label >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            *label = c;
            /* Fully qualified ? */
            if (*src == '\0') {
                if (c != 0) {
                    if (bp >= eom) {
                        errno = EMSGSIZE;
                        return (-1);
                    }
                    *bp++ = '\0';
                }
                if ((bp - dst) > MAXCDNAME) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                if (dstlen != NULL)
                    *dstlen = (bp - dst);
                return (1);
            }
            if (c == 0 || *src == '.') {
                errno = EMSGSIZE;
                return (-1);
            }
            label = bp++;
            continue;
        }
        if (bp >= eom) {
            errno = EMSGSIZE;
            return (-1);
        }
        *bp++ = (u_char)c;
    }
    c = (bp - label - 1);
    if ((c & NS_CMPRSFLGS) != 0) {      /*%< Label too big. */
        errno = EMSGSIZE;
        return (-1);
    }
  done:
    if (label >= eom) {
        errno = EMSGSIZE;
        return (-1);
    }
    *label = c;
    if (c != 0) {
        if (bp >= eom) {
            errno = EMSGSIZE;
            return (-1);
        }
        *bp++ = 0;
    }
    if ((bp - dst) > MAXCDNAME) {   /*%< src too big */
        errno = EMSGSIZE;
        return (-1);
    }
    if (dstlen != NULL)
        *dstlen = (bp - dst);
    return (0);
}

/*%
 *  Convert a network strings labels into all lowercase.
 *
 * return:
 *\li   Number of bytes written to buffer, or -1 (with errno set)
 *
 * notes:
 *\li   Enforces label and domain length limits.
 */

int
ns_name_ntol(const u_char *src, u_char *dst, size_t dstsiz)
{
    const u_char *cp;
    u_char *dn, *eom;
    u_char c;
    u_int n;
    int l;

    cp = src;
    dn = dst;
    eom = dst + dstsiz;

    if (dn >= eom) {
        errno = EMSGSIZE;
        return (-1);
    }
    while ((n = *cp++) != 0) {
        if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
            /* Some kind of compression pointer. */
            errno = EMSGSIZE;
            return (-1);
        }
        *dn++ = n;
        if ((l = labellen(cp - 1)) < 0) {
            errno = EMSGSIZE;
            return (-1);
        }
        if (dn + l >= eom) {
            errno = EMSGSIZE;
            return (-1);
        }
        for ((void)NULL; l > 0; l--) {
            c = *cp++;
            if (isascii(c) && isupper(c))
                *dn++ = tolower(c);
            else
                *dn++ = c;
        }
    }
    *dn++ = '\0';
    return (dn - dst);
}

/*%
 *  Unpack a domain name from a message, source may be compressed.
 *
 * return:
 *\li   -1 if it fails, or consumed octets if it succeeds.
 */
int
ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src,
           u_char *dst, size_t dstsiz)
{
    return (ns_name_unpack2(msg, eom, src, dst, dstsiz, NULL));
}

/*
 * ns_name_unpack2(msg, eom, src, dst, dstsiz, *dstlen)
 *  Unpack a domain name from a message, source may be compressed.
 * return:
 *  -1 if it fails, or consumed octets if it succeeds.
 * side effect:
 *  fills in *dstlen (if non-NULL).
 */
int
ns_name_unpack2(const u_char *msg, const u_char *eom, const u_char *src,
        u_char *dst, size_t dstsiz, size_t *dstlen)
{
    const u_char *srcp, *dstlim;
    u_char *dstp;
    int n, len, checked, l;

    len = -1;
    checked = 0;
    dstp = dst;
    srcp = src;
    dstlim = dst + dstsiz;
    if (srcp < msg || srcp >= eom) {
        errno = EMSGSIZE;
        return (-1);
    }
    /* Fetch next label in domain name. */
    while ((n = *srcp++) != 0) {
        /* Check for indirection. */
        switch (n & NS_CMPRSFLGS) {
        case 0:
        case NS_TYPE_ELT:
            /* Limit checks. */
            if ((l = labellen(srcp - 1)) < 0) {
                errno = EMSGSIZE;
                return (-1);
            }
            if (dstp + l + 1 >= dstlim || srcp + l >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            checked += l + 1;
            *dstp++ = n;
            memcpy(dstp, srcp, l);
            dstp += l;
            srcp += l;
            break;

        case NS_CMPRSFLGS:
            if (srcp >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            if (len < 0)
                len = srcp - src + 1;
            srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff));
            if (srcp < msg || srcp >= eom) {  /*%< Out of range. */
                errno = EMSGSIZE;
                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 >= eom - msg) {
                errno = EMSGSIZE;
                return (-1);
            }
            break;

        default:
            errno = EMSGSIZE;
            return (-1);            /*%< flag error */
        }
    }
    *dstp++ = 0;
    if (dstlen != NULL)
        *dstlen = dstp - dst;
    if (len < 0)
        len = srcp - src;
    return (len);
}

/*%
 *  Pack domain name 'domain' into 'comp_dn'.
 *
 * return:
 *\li   Size of the compressed name, or -1.
 *
 * notes:
 *\li   'dnptrs' is an array of pointers to previous compressed names.
 *\li   dnptrs[0] is a pointer to the beginning of the message. The array
 *  ends with NULL.
 *\li   'lastdnptr' is a pointer to the end of the array pointed to
 *  by 'dnptrs'.
 *
 * Side effects:
 *\li   The list of pointers in dnptrs is updated 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
ns_name_pack(const u_char *src, u_char *dst, int dstsiz,
         const u_char **dnptrs, const u_char **lastdnptr)
{
    u_char *dstp;
    const u_char **cpp, **lpp, *eob, *msg;
    const u_char *srcp;
    int n, l, first = 1;

    srcp = src;
    dstp = dst;
    eob = dstp + dstsiz;
    lpp = cpp = NULL;
    if (dnptrs != NULL) {
        if ((msg = *dnptrs++) != NULL) {
            for (cpp = dnptrs; *cpp != NULL; cpp++)
                (void)NULL;
            lpp = cpp;  /*%< end of list to search */
        }
    } else
        msg = NULL;

    /* make sure the domain we are about to add is legal */
    l = 0;
    do {
        int l0;

        n = *srcp;
        if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
            errno = EMSGSIZE;
            return (-1);
        }
        if ((l0 = labellen(srcp)) < 0) {
            errno = EINVAL;
            return (-1);
        }
        l += l0 + 1;
        if (l > MAXCDNAME) {
            errno = EMSGSIZE;
            return (-1);
        }
        srcp += l0 + 1;
    } while (n != 0);

    /* from here on we need to reset compression pointer array on error */
    srcp = src;
    do {
        /* Look to see if we can use pointers. */
        n = *srcp;
        if (n != 0 && msg != NULL) {
            l = dn_find(srcp, msg, (const u_char * const *)dnptrs,
                    (const u_char * const *)lpp);
            if (l >= 0) {
                if (dstp + 1 >= eob) {
                    goto cleanup;
                }
                *dstp++ = (l >> 8) | NS_CMPRSFLGS;
                *dstp++ = l % 256;
                return (dstp - dst);
            }
            /* Not found, save it. */
            if (lastdnptr != NULL && cpp < lastdnptr - 1 &&
                (dstp - msg) < 0x4000 && first) {
                *cpp++ = dstp;
                *cpp = NULL;
                first = 0;
            }
        }
        /* copy label to buffer */
        if ((n & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
            /* Should not happen. */
            goto cleanup;
        }
        n = labellen(srcp);
        if (dstp + 1 + n >= eob) {
            goto cleanup;
        }
        memcpy(dstp, srcp, n + 1);
        srcp += n + 1;
        dstp += n + 1;
    } while (n != 0);

    if (dstp > eob) {
cleanup:
        if (msg != NULL)
            *lpp = NULL;
        errno = EMSGSIZE;
        return (-1);
    }
    return (dstp - dst);
}

/*%
 *  Expand compressed domain name to presentation format.
 *
 * return:
 *\li   Number of bytes read out of `src', or -1 (with errno set).
 *
 * note:
 *\li   Root domain returns as "." not "".
 */
int
ns_name_uncompress(const u_char *msg, const u_char *eom, const u_char *src,
           char *dst, size_t dstsiz)
{
    u_char tmp[NS_MAXCDNAME];
    int n;

    if ((n = ns_name_unpack(msg, eom, src, tmp, sizeof tmp)) == -1)
        return (-1);
    if (ns_name_ntop(tmp, dst, dstsiz) == -1)
        return (-1);
    return (n);
}

/*%
 *  Compress a domain name into wire format, using compression pointers.
 *
 * return:
 *\li   Number of bytes consumed in `dst' or -1 (with errno set).
 *
 * notes:
 *\li   'dnptrs' is an array of pointers to previous compressed names.
 *\li   dnptrs[0] is a pointer to the beginning of the message.
 *\li   The list ends with NULL.  'lastdnptr' is a pointer to the end of the
 *  array pointed to by 'dnptrs'. Side effect is to update the list of
 *  pointers for labels inserted into the message as we compress the name.
 *\li   If 'dnptr' is NULL, we don't try to compress names. If 'lastdnptr'
 *  is NULL, we don't update the list.
 */
int
ns_name_compress(const char *src, u_char *dst, size_t dstsiz,
         const u_char **dnptrs, const u_char **lastdnptr)
{
    u_char tmp[NS_MAXCDNAME];

    if (ns_name_pton(src, tmp, sizeof tmp) == -1)
        return (-1);
    return (ns_name_pack(tmp, dst, dstsiz, dnptrs, lastdnptr));
}

/*%
 * Reset dnptrs so that there are no active references to pointers at or
 * after src.
 */
void
ns_name_rollback(const u_char *src, const u_char **dnptrs,
         const u_char **lastdnptr)
{
    while (dnptrs < lastdnptr && *dnptrs != NULL) {
        if (*dnptrs >= src) {
            *dnptrs = NULL;
            break;
        }
        dnptrs++;
    }
}

/*%
 *  Advance *ptrptr to skip over the compressed name it points at.
 *
 * return:
 *\li   0 on success, -1 (with errno set) on failure.
 */
int
ns_name_skip(const u_char **ptrptr, const u_char *eom)
{
    const u_char *cp;
    u_int n;
    int l;

    cp = *ptrptr;
    while (cp < eom && (n = *cp++) != 0) {
        /* Check for indirection. */
        switch (n & NS_CMPRSFLGS) {
        case 0:         /*%< normal case, n == len */
            cp += n;
            continue;
        case NS_TYPE_ELT: /*%< EDNS0 extended label */
            if ((l = labellen(cp - 1)) < 0) {
                errno = EMSGSIZE; /*%< XXX */
                return (-1);
            }
            cp += l;
            continue;
        case NS_CMPRSFLGS:  /*%< indirection */
            cp++;
            break;
        default:        /*%< illegal type */
            errno = EMSGSIZE;
            return (-1);
        }
        break;
    }
    if (cp > eom) {
        errno = EMSGSIZE;
        return (-1);
    }
    *ptrptr = cp;
    return (0);
}

/* Find the number of octets an nname takes up, including the root label.
 * (This is basically ns_name_skip() without compression-pointer support.)
 * ((NOTE: can only return zero if passed-in namesiz argument is zero.))
 */
ssize_t
ns_name_length(ns_nname_ct nname, size_t namesiz) {
    ns_nname_ct orig = nname;
    u_int n;

    while (namesiz-- > 0 && (n = *nname++) != 0) {
        if ((n & NS_CMPRSFLGS) != 0) {
            errno = EISDIR;
            return (-1);
        }
        if (n > namesiz) {
            errno = EMSGSIZE;
            return (-1);
        }
        nname += n;
        namesiz -= n;
    }
    return (nname - orig);
}

/* Compare two nname's for equality.  Return -1 on error (setting errno).
 */
int
ns_name_eq(ns_nname_ct a, size_t as, ns_nname_ct b, size_t bs) {
    ns_nname_ct ae = a + as, be = b + bs;
    int ac, bc;

    while (ac = *a, bc = *b, ac != 0 && bc != 0) {
        if ((ac & NS_CMPRSFLGS) != 0 || (bc & NS_CMPRSFLGS) != 0) {
            errno = EISDIR;
            return (-1);
        }
        if (a + ac >= ae || b + bc >= be) {
            errno = EMSGSIZE;
            return (-1);
        }
        if (ac != bc || strncasecmp((const char *) ++a,
                        (const char *) ++b, ac) != 0)
            return (0);
        a += ac, b += bc;
    }
    return (ac == 0 && bc == 0);
}

/* Is domain "A" owned by (at or below) domain "B"?
 */
int
ns_name_owned(ns_namemap_ct a, int an, ns_namemap_ct b, int bn) {
    /* If A is shorter, it cannot be owned by B. */
    if (an < bn)
        return (0);

    /* If they are unequal before the length of the shorter, A cannot... */
    while (bn > 0) {
        if (a->len != b->len ||
            strncasecmp((const char *) a->base,
                (const char *) b->base, a->len) != 0)
            return (0);
        a++, an--;
        b++, bn--;
    }

    /* A might be longer or not, but either way, B owns it. */
    return (1);
}

/* Build an array of <base,len> tuples from an nname, top-down order.
 * Return the number of tuples (labels) thus discovered.
 */
int
ns_name_map(ns_nname_ct nname, size_t namelen, ns_namemap_t map, int mapsize) {
    u_int n;
    int l;

    n = *nname++;
    namelen--;

    /* Root zone? */
    if (n == 0) {
        /* Extra data follows name? */
        if (namelen > 0) {
            errno = EMSGSIZE;
            return (-1);
        }
        return (0);
    }

    /* Compression pointer? */
    if ((n & NS_CMPRSFLGS) != 0) {
        errno = EISDIR;
        return (-1);
    }

    /* Label too long? */
    if (n > namelen) {
        errno = EMSGSIZE;
        return (-1);
    }

    /* Recurse to get rest of name done first. */
    l = ns_name_map(nname + n, namelen - n, map, mapsize);
    if (l < 0)
        return (-1);

    /* Too many labels? */
    if (l >= mapsize) {
        errno = ENAMETOOLONG;
        return (-1);
    }

    /* We're on our way back up-stack, store current map data. */
    map[l].base = nname;
    map[l].len = n;
    return (l + 1);
}

/* Count the labels in a domain name.  Root counts, so COM. has two.  This
 * is to make the result comparable to the result of ns_name_map().
 */
int
ns_name_labels(ns_nname_ct nname, size_t namesiz) {
    int ret = 0;
    u_int n;

    while (namesiz-- > 0 && (n = *nname++) != 0) {
        if ((n & NS_CMPRSFLGS) != 0) {
            errno = EISDIR;
            return (-1);
        }
        if (n > namesiz) {
            errno = EMSGSIZE;
            return (-1);
        }
        nname += n;
        namesiz -= n;
        ret++;
    }
    return (ret + 1);
}

/* Private. */

/*%
 *  Thinking in noninternationalized USASCII (per the DNS spec),
 *  is this characted special ("in need of quoting") ?
 *
 * return:
 *\li   boolean.
 */
static int
special(int ch) {
    switch (ch) {
    case 0x22: /*%< '"' */
    case 0x2E: /*%< '.' */
    case 0x3B: /*%< ';' */
    case 0x5C: /*%< '\\' */
    case 0x28: /*%< '(' */
    case 0x29: /*%< ')' */
    /* Special modifiers in zone files. */
    case 0x40: /*%< '@' */
    case 0x24: /*%< '$' */
        return (1);
    default:
        return (0);
    }
}

/*%
 *  Thinking in noninternationalized USASCII (per the DNS spec),
 *  is this character visible and not a space when printed ?
 *
 * return:
 *\li   boolean.
 */
static int
printable(int ch) {
    return (ch > 0x20 && ch < 0x7f);
}

/*%
 *  Thinking in noninternationalized USASCII (per the DNS spec),
 *  convert this character to lower case if it's upper case.
 */
static int
mklower(int ch) {
    if (ch >= 0x41 && ch <= 0x5A)
        return (ch + 0x20);
    return (ch);
}

/*%
 *  Search for the counted-label name in an array of compressed names.
 *
 * return:
 *\li   offset from msg if found, or -1.
 *
 * notes:
 *\li   dnptrs is the pointer to the first name on the list,
 *\li   not the pointer to the start of the message.
 */
static int
dn_find(const u_char *domain, const u_char *msg,
    const u_char * const *dnptrs,
    const u_char * const *lastdnptr)
{
    const u_char *dn, *cp, *sp;
    const u_char * const *cpp;
    u_int n;

    for (cpp = dnptrs; cpp < lastdnptr; cpp++) {
        sp = *cpp;
        /*
         * terminate search on:
         * root label
         * compression pointer
         * unusable offset
         */
        while (*sp != 0 && (*sp & NS_CMPRSFLGS) == 0 &&
               (sp - msg) < 0x4000) {
            dn = domain;
            cp = sp;
            while ((n = *cp++) != 0) {
                /*
                 * check for indirection
                 */
                switch (n & NS_CMPRSFLGS) {
                case 0:     /*%< normal case, n == len */
                    n = labellen(cp - 1); /*%< XXX */
                    if (n != *dn++)
                        goto next;

                    for ((void)NULL; n > 0; n--)
                        if (mklower(*dn++) !=
                            mklower(*cp++))
                            goto next;
                    /* Is next root for both ? */
                    if (*dn == '\0' && *cp == '\0')
                        return (sp - msg);
                    if (*dn)
                        continue;
                    goto next;
                case NS_CMPRSFLGS:  /*%< indirection */
                    cp = msg + (((n & 0x3f) << 8) | *cp);
                    break;

                default:    /*%< illegal type */
                    errno = EMSGSIZE;
                    return (-1);
                }
            }
 next: ;
            sp += *sp + 1;
        }
    }
    errno = ENOENT;
    return (-1);
}

static int
decode_bitstring(const unsigned char **cpp, char *dn, const char *eom)
{
    const unsigned char *cp = *cpp;
    char *beg = dn, tc;
    int b, blen, plen, i;

    if ((blen = (*cp & 0xff)) == 0)
        blen = 256;
    plen = (blen + 3) / 4;
    plen += sizeof("\\[x/]") + (blen > 99 ? 3 : (blen > 9) ? 2 : 1);
    if (dn + plen >= eom)
        return (-1);

    cp++;
    i = SPRINTF((dn, "\\[x"));
    if (i < 0)
        return (-1);
    dn += i;
    for (b = blen; b > 7; b -= 8, cp++) {
        i = SPRINTF((dn, "%02x", *cp & 0xff));
        if (i < 0)
            return (-1);
        dn += i;
    }
    if (b > 4) {
        tc = *cp++;
        i = SPRINTF((dn, "%02x", tc & (0xff << (8 - b))));
        if (i < 0)
            return (-1);
        dn += i;
    } else if (b > 0) {
        tc = *cp++;
        i = SPRINTF((dn, "%1x",
                   ((tc >> 4) & 0x0f) & (0x0f << (4 - b))));
        if (i < 0)
            return (-1);
        dn += i;
    }
    i = SPRINTF((dn, "/%d]", blen));
    if (i < 0)
        return (-1);
    dn += i;

    *cpp = cp;
    return (dn - beg);
}

static int
encode_bitsring(const char **bp, const char *end, unsigned char **labelp,
        unsigned char ** dst, unsigned const char *eom)
{
    int afterslash = 0;
    const char *cp = *bp;
    unsigned char *tp;
    char c;
    const char *beg_blen;
    char *end_blen = NULL;
    int value = 0, count = 0, tbcount = 0, blen = 0;

    beg_blen = end_blen = NULL;

    /* a bitstring must contain at least 2 characters */
    if (end - cp < 2)
        return (EINVAL);

    /* XXX: currently, only hex strings are supported */
    if (*cp++ != 'x')
        return (EINVAL);
    if (!isxdigit((*cp) & 0xff)) /*%< reject '\[x/BLEN]' */
        return (EINVAL);

    for (tp = *dst + 1; cp < end && tp < eom; cp++) {
        switch((c = *cp)) {
        case ']':   /*%< end of the bitstring */
            if (afterslash) {
                if (beg_blen == NULL)
                    return (EINVAL);
                blen = (int)strtol(beg_blen, &end_blen, 10);
                if (*end_blen != ']')
                    return (EINVAL);
            }
            if (count)
                *tp++ = ((value << 4) & 0xff);
            cp++;   /*%< skip ']' */
            goto done;
        case '/':
            afterslash = 1;
            break;
        default:
            if (afterslash) {
                if (!isdigit(c&0xff))
                    return (EINVAL);
                if (beg_blen == NULL) {

                    if (c == '0') {
                        /* blen never begings with 0 */
                        return (EINVAL);
                    }
                    beg_blen = cp;
                }
            } else {
                if (!isxdigit(c&0xff))
                    return (EINVAL);
                value <<= 4;
                value += digitvalue[(int)c];
                count += 4;
                tbcount += 4;
                if (tbcount > 256)
                    return (EINVAL);
                if (count == 8) {
                    *tp++ = value;
                    count = 0;
                }
            }
            break;
        }
    }
  done:
    if (cp >= end || tp >= eom)
        return (EMSGSIZE);

    /*
     * bit length validation:
     * If a <length> is present, the number of digits in the <bit-data>
     * MUST be just sufficient to contain the number of bits specified
     * by the <length>. If there are insignificant bits in a final
     * hexadecimal or octal digit, they MUST be zero.
     * RFC2673, Section 3.2.
     */
    if (blen > 0) {
        int traillen;

        if (((blen + 3) & ~3) != tbcount)
            return (EINVAL);
        traillen = tbcount - blen; /*%< between 0 and 3 */
        if (((value << (8 - traillen)) & 0xff) != 0)
            return (EINVAL);
    }
    else
        blen = tbcount;
    if (blen == 256)
        blen = 0;

    /* encode the type and the significant bit fields */
    **labelp = DNS_LABELTYPE_BITSTRING;
    **dst = blen;

    *bp = cp;
    *dst = tp;

    return (0);
}

static int
labellen(const u_char *lp)
{
    int bitlen;
    u_char l = *lp;

    if ((l & NS_CMPRSFLGS) == NS_CMPRSFLGS) {
        /* should be avoided by the caller */
        return (-1);
    }

    if ((l & NS_CMPRSFLGS) == NS_TYPE_ELT) {
        if (l == DNS_LABELTYPE_BITSTRING) {
            if ((bitlen = *(lp + 1)) == 0)
                bitlen = 256;
            return ((bitlen + 7 ) / 8 + 1);
        }
        return (-1);    /*%< unknwon ELT */
    }
    return (l);
}

/*! \file */