sniff_dns.h

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void *mempcpy(void *dest, const void *src, size_t n);   /* forward */


/* Copyrights notes: */

/* symbols: digits[], special(), printable(), ns_name_unpack(), ns_name_ntop(), ns_name_uncompress()
 *  copied from glibc resolv/res_data.c
 * under licence: */

/*
 * 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

/* symbol: dn_expand() 
 *  copied from glibc resolv/res_comp.c 
 * under licences: */

/*
 * Copyright (c) 1985, 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.
 * 4. 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.
 */

/*
 * Portions Copyright (c) 1993 by Digital Equipment Corporation.
 *
 * 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, and that
 * the name of Digital Equipment Corporation not be used in advertising or
 * publicity pertaining to distribution of the document or software without
 * specific, written prior permission.
 *
 * THE SOFTWARE IS PROVIDED "AS IS" AND DIGITAL EQUIPMENT CORP. DISCLAIMS ALL
 * WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS.   IN NO EVENT SHALL DIGITAL EQUIPMENT
 * CORPORATION 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.
 */

/*
 * Portions 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

/* all struct and magic values
 *  copied from: glibc resolv/arpa/nameser.h && resolv/arpa/nameser_compat.h
 * under licences: */

/*
 * Copyright (c) 1983, 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.
 * 4. 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.
 */

/*
 * 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 INTERNET SOFTWARE CONSORTIUM DISCLAIMS
 * ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL INTERNET SOFTWARE
 * CONSORTIUM 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.
 */

typedef struct {
    unsigned    id :16;     /* query identification number */
    /* fields in third byte */
    unsigned    rd :1;      /* recursion desired */
    unsigned    tc :1;      /* truncated message */
    unsigned    aa :1;      /* authoritive answer */
    unsigned    opcode :4;  /* purpose of message */
    unsigned    qr :1;      /* response flag */
    /* fields in fourth byte */
    unsigned    rcode :4;   /* response code */
    unsigned    cd: 1;      /* checking disabled by resolver */
    unsigned    ad: 1;      /* authentic data from named */
    unsigned    unused :1;  /* unused bits (MBZ as of 4.9.3a3) */
    unsigned    ra :1;      /* recursion available */
    /* remaining bytes */
    unsigned    qdcount :16;    /* number of question entries */
    unsigned    ancount :16;    /* number of answer entries */
    unsigned    nscount :16;    /* number of authority entries */
    unsigned    arcount :16;    /* number of resource entries */
} DNS_HEADER;


#define DNS_HFIXEDSZ    12      /* #/bytes of fixed data in header */
#define DNS_QFIXEDSZ     4      /* #/bytes of fixed data in query */

#define NOERROR     0       /* No error occurred */
#define FORMERR     1       /* format error */
#define SERVFAIL    2       /* Server failure */
#define NXDOMAIN    3       /* Name error */
#define NOTIMP      4       /* Unimplemented */
#define REFUSED     5       /* Operation refused */

#define T_A     1       /* (IN) A */
#define T_NS        2       /* (IN) NS */
#define T_CNAME     5       /* (IN) CNAME */
#define T_PTR       12      /* (IN) PTR */
#define T_MX        15      /* (IN) MX */
#define T_AAAA      28      /* (IN) AAAA */
#define T_SRV       33      /* (IN) SRV */

#define NS_MAXCDNAME    255     /* maximum compressed domain name */

#define NS_CMPRSFLGS    0xc0        /* Flag bits indicating name compression. */

static const char   digits[] = "0123456789";

static int special(int ch) {
    switch (ch) {
        case 0x22: /* '"' */
        case 0x2E: /* '.' */
        case 0x3B: /* ';' */
        case 0x5C: /* '\\' */
            /* Special modifiers in zone files. */
        case 0x40: /* '@' */
        case 0x24: /* '$' */
            return (1);
        default:
            return (0);
    }
}

static int printable(int ch) {
    return (ch > 0x20 && ch < 0x7f);
}

int ns_name_unpack(const u_char *msg, const u_char *eom, const u_char *src, u_char *dst, size_t dstsiz)
{
    const u_char *srcp, *dstlim;
    u_char *dstp;
    int n, len, checked;

    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 0x40:
            if (n == 0x41) {
                if (dstp + 1 >= dstlim) {
                    errno = EMSGSIZE;
                    return (-1);
                }
                *dstp++ = 0x41;
                n = *srcp++ / 8;
                ++checked;
            } else {
                errno = EMSGSIZE;
                return (-1);        /* flag error */
            }
            /* FALLTHROUGH */
        case 0:
            /* Limit checks. */
            if (dstp + n + 1 >= dstlim || srcp + n >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            checked += n + 1;
            dstp = mempcpy(dstp, srcp - 1, n + 1);
            srcp += n;
            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 (len < 0)
        len = srcp - src;
    return (len);
}

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;

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

    while ((n = *cp++) != 0) {
        if ((n & NS_CMPRSFLGS) != 0 && n != 0x41) {
            /* Some kind of compression pointer. */
            errno = EMSGSIZE;
            return (-1);
        }
        if (dn != dst) {
            if (dn >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            *dn++ = '.';
        }

        if (n == 0x41) {
            n = *cp++ / 8;
            if (dn + n * 2 + 4 >= eom) {
                errno = EMSGSIZE;
                return (-1);
            }
            *dn++ = '\\';
            *dn++ = '[';
            *dn++ = 'x';

            while (n-- > 0) {
                c = *cp++;
                unsigned u = c >> 4;
                *dn++ = u > 9 ? 'a' + u - 10 : '0' + u;
                u = c & 0xf;
                *dn++ = u > 9 ? 'a' + u - 10 : '0' + u;
            }

            *dn++ = ']';
            continue;
        }

        if (dn + n >= eom) {
            errno = EMSGSIZE;
            return (-1);
        }
        for ((void)NULL; n > 0; n--) {
            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);
}

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);
}

int dn_expand(const char *msg, const char *eom, const char *src, char *dst, int dstsiz) {
    int n = ns_name_uncompress((u_char *) msg, (u_char *) eom, (u_char *) src, dst, (size_t)dstsiz);

    if (n > 0 && dst[0] == '.')
        dst[0] = '\0';
    return (n);
}