lib/isccc/cc.c

	cc.c revision dafcb997e390efa4423883dafd100c975c4095d6
/*
 * Portions Copyright (C) 2004  Internet Systems Consortium, Inc. ("ISC")
 * Portions Copyright (C) 2001-2003  Internet Software Consortium.
 * Portions Copyright (C) 2001  Nominum, Inc.
 *
 * 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 AND NOMINUM 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.
 */

/* $Id: cc.c,v 1.10 2004/03/05 05:12:09 marka Exp $ */

#include <config.h>

#include <stdio.h>
#include <string.h>
#include <errno.h>

#include <isc/assertions.h>
#include <isc/hmacmd5.h>
#include <isc/stdlib.h>

#include <isccc/alist.h>
#include <isccc/base64.h>
#include <isccc/cc.h>
#include <isccc/result.h>
#include <isccc/sexpr.h>
#include <isccc/symtab.h>
#include <isccc/symtype.h>
#include <isccc/util.h>

#define MAX_TAGS        256
#define DUP_LIFETIME        900

typedef isccc_sexpr_t *sexpr_ptr;

static unsigned char auth_hmd5[] = {
    0x05, 0x5f, 0x61, 0x75, 0x74, 0x68,     /* len + _auth */
    ISCCC_CCMSGTYPE_TABLE,              /* message type */
    0x00, 0x00, 0x00, 0x20,             /* length == 32 */
    0x04, 0x68, 0x6d, 0x64, 0x35,           /* len + hmd5 */
    ISCCC_CCMSGTYPE_BINARYDATA,         /* message type */
    0x00, 0x00, 0x00, 0x16,             /* length == 22 */
    /*
     * The base64 encoding of one of our HMAC-MD5 signatures is
     * 22 bytes.
     */
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x00, 0x00, 0x00
};

#define HMD5_OFFSET 21      /* 6 + 1 + 4 + 5 + 1 + 4 */
#define HMD5_LENGTH 22

static isc_result_t
table_towire(isccc_sexpr_t *alist, isccc_region_t *target);

static isc_result_t
list_towire(isccc_sexpr_t *alist, isccc_region_t *target);

static isc_result_t
value_towire(isccc_sexpr_t *elt, isccc_region_t *target)
{
    size_t len;
    unsigned char *lenp;
    isccc_region_t *vr;
    isc_result_t result;

    if (isccc_sexpr_binaryp(elt)) {
        vr = isccc_sexpr_tobinary(elt);
        len = REGION_SIZE(*vr);
        if (REGION_SIZE(*target) < 1 + 4 + len)
            return (ISC_R_NOSPACE);
        PUT8(ISCCC_CCMSGTYPE_BINARYDATA, target->rstart);
        PUT32(len, target->rstart);
        if (REGION_SIZE(*target) < len)
            return (ISC_R_NOSPACE);
        PUT_MEM(vr->rstart, len, target->rstart);
    } else if (isccc_alist_alistp(elt)) {
        if (REGION_SIZE(*target) < 1 + 4)
            return (ISC_R_NOSPACE);
        PUT8(ISCCC_CCMSGTYPE_TABLE, target->rstart);
        /*
         * Emit a placeholder length.
         */
        lenp = target->rstart;
        PUT32(0, target->rstart);
        /*
         * Emit the table.
         */
        result = table_towire(elt, target);
        if (result != ISC_R_SUCCESS)
            return (result);
        len = (size_t)(target->rstart - lenp);
        /*
         * 'len' is 4 bytes too big, since it counts
         * the placeholder length too.  Adjust and
         * emit.
         */
        INSIST(len >= 4U);
        len -= 4;
        PUT32(len, lenp);
    } else if (isccc_sexpr_listp(elt)) {
        if (REGION_SIZE(*target) < 1 + 4)
            return (ISC_R_NOSPACE);
        PUT8(ISCCC_CCMSGTYPE_LIST, target->rstart);
        /*
         * Emit a placeholder length and count.
         */
        lenp = target->rstart;
        PUT32(0, target->rstart);
        /*
         * Emit the list.
         */
        result = list_towire(elt, target);
        if (result != ISC_R_SUCCESS)
            return (result);
        len = (size_t)(target->rstart - lenp);
        /*
         * 'len' is 4 bytes too big, since it counts
         * the placeholder length.  Adjust and emit.
         */
        INSIST(len >= 4U);
        len -= 4;
        PUT32(len, lenp);
    }

    return (ISC_R_SUCCESS);
}

static isc_result_t
table_towire(isccc_sexpr_t *alist, isccc_region_t *target)
{
    isccc_sexpr_t *kv, *elt, *k, *v;
    char *ks;
    isc_result_t result;
    size_t len;

    for (elt = isccc_alist_first(alist);
         elt != NULL;
         elt = ISCCC_SEXPR_CDR(elt)) {
        kv = ISCCC_SEXPR_CAR(elt);
        k = ISCCC_SEXPR_CAR(kv);
        ks = isccc_sexpr_tostring(k);
        v = ISCCC_SEXPR_CDR(kv);
        len = strlen(ks);
        INSIST(len <= 255U);
        /*
         * Emit the key name.
         */
        if (REGION_SIZE(*target) < 1 + len)
            return (ISC_R_NOSPACE);
        PUT8(len, target->rstart);
        PUT_MEM(ks, len, target->rstart);
        /*
         * Emit the value.
         */
        result = value_towire(v, target);
        if (result != ISC_R_SUCCESS)
            return (result);
    }

    return (ISC_R_SUCCESS);
}

static isc_result_t
list_towire(isccc_sexpr_t *list, isccc_region_t *target)
{
    isc_result_t result;

    while (list != NULL) {
        result = value_towire(ISCCC_SEXPR_CAR(list), target);
        if (result != ISC_R_SUCCESS)
            return (result);
        list = ISCCC_SEXPR_CDR(list);
    }

    return (ISC_R_SUCCESS);
}

static isc_result_t
sign(unsigned char *data, unsigned int length, unsigned char *hmd5,
     isccc_region_t *secret)
{
    isc_hmacmd5_t ctx;
    isc_result_t result;
    isccc_region_t source, target;
    unsigned char digest[ISC_MD5_DIGESTLENGTH];
    unsigned char digestb64[ISC_MD5_DIGESTLENGTH * 4];

    isc_hmacmd5_init(&ctx, secret->rstart, REGION_SIZE(*secret));
    isc_hmacmd5_update(&ctx, data, length);
    isc_hmacmd5_sign(&ctx, digest);
    source.rstart = digest;
    source.rend = digest + ISC_MD5_DIGESTLENGTH;
    target.rstart = digestb64;
    target.rend = digestb64 + ISC_MD5_DIGESTLENGTH * 4;
    result = isccc_base64_encode(&source, 64, "", &target);
    if (result != ISC_R_SUCCESS)
        return (result);
    PUT_MEM(digestb64, HMD5_LENGTH, hmd5);

    return (ISC_R_SUCCESS);
}

isc_result_t
isccc_cc_towire(isccc_sexpr_t *alist, isccc_region_t *target,
          isccc_region_t *secret)
{
    unsigned char *hmd5_rstart, *signed_rstart;
    isc_result_t result;

    if (REGION_SIZE(*target) < 4 + sizeof(auth_hmd5))
        return (ISC_R_NOSPACE);
    /*
     * Emit protocol version.
     */
    PUT32(1, target->rstart);
    if (secret != NULL) {
        /*
         * Emit _auth section with zeroed HMAC-MD5 signature.
         * We'll replace the zeros with the real signature once
         * we know what it is.
         */
        hmd5_rstart = target->rstart + HMD5_OFFSET;
        PUT_MEM(auth_hmd5, sizeof(auth_hmd5), target->rstart);
    } else
        hmd5_rstart = NULL;
    signed_rstart = target->rstart;
    /*
     * Delete any existing _auth section so that we don't try
     * to encode it.
     */
    isccc_alist_delete(alist, "_auth");
    /*
     * Emit the message.
     */
    result = table_towire(alist, target);
    if (result != ISC_R_SUCCESS)
        return (result);
    if (secret != NULL)
        return (sign(signed_rstart, (target->rstart - signed_rstart),
                 hmd5_rstart, secret));
    return (ISC_R_SUCCESS);
}

static isc_result_t
verify(isccc_sexpr_t *alist, unsigned char *data, unsigned int length,
       isccc_region_t *secret)
{
    isc_hmacmd5_t ctx;
    isccc_region_t source;
    isccc_region_t target;
    isc_result_t result;
    isccc_sexpr_t *_auth, *hmd5;
    unsigned char digest[ISC_MD5_DIGESTLENGTH];
    unsigned char digestb64[ISC_MD5_DIGESTLENGTH * 4];

    /*
     * Extract digest.
     */
    _auth = isccc_alist_lookup(alist, "_auth");
    if (_auth == NULL)
        return (ISC_R_FAILURE);
    hmd5 = isccc_alist_lookup(_auth, "hmd5");
    if (hmd5 == NULL)
        return (ISC_R_FAILURE);
    /*
     * Compute digest.
     */
    isc_hmacmd5_init(&ctx, secret->rstart, REGION_SIZE(*secret));
    isc_hmacmd5_update(&ctx, data, length);
    isc_hmacmd5_sign(&ctx, digest);
    source.rstart = digest;
    source.rend = digest + ISC_MD5_DIGESTLENGTH;
    target.rstart = digestb64;
    target.rend = digestb64 + ISC_MD5_DIGESTLENGTH * 4;
    result = isccc_base64_encode(&source, 64, "", &target);
    if (result != ISC_R_SUCCESS)
        return (result);
    /*
     * Strip trailing == and NUL terminate target.
     */
    target.rstart -= 2;
    *target.rstart++ = '\0';
    /*
     * Verify.
     */
    if (strcmp((char *)digestb64, isccc_sexpr_tostring(hmd5)) != 0)
        return (ISCCC_R_BADAUTH);

    return (ISC_R_SUCCESS);
}

static isc_result_t
table_fromwire(isccc_region_t *source, isccc_region_t *secret,
           isccc_sexpr_t **alistp);

static isc_result_t
list_fromwire(isccc_region_t *source, isccc_sexpr_t **listp);

static isc_result_t
value_fromwire(isccc_region_t *source, isccc_sexpr_t **valuep)
{
    unsigned int msgtype;
    isc_uint32_t len;
    isccc_sexpr_t *value;
    isccc_region_t active;
    isc_result_t result;

    if (REGION_SIZE(*source) < 1 + 4)
        return (ISC_R_UNEXPECTEDEND);
    GET8(msgtype, source->rstart);
    GET32(len, source->rstart);
    if (REGION_SIZE(*source) < len)
        return (ISC_R_UNEXPECTEDEND);
    active.rstart = source->rstart;
    active.rend = active.rstart + len;
    source->rstart = active.rend;
    if (msgtype == ISCCC_CCMSGTYPE_BINARYDATA) {
        value = isccc_sexpr_frombinary(&active);
        if (value != NULL) {
            *valuep = value;
            result = ISC_R_SUCCESS;
        } else
            result = ISC_R_NOMEMORY;
    } else if (msgtype == ISCCC_CCMSGTYPE_TABLE)
        result = table_fromwire(&active, NULL, valuep);
    else if (msgtype == ISCCC_CCMSGTYPE_LIST)
        result = list_fromwire(&active, valuep);
    else
        result = ISCCC_R_SYNTAX;

    return (result);
}

static isc_result_t
table_fromwire(isccc_region_t *source, isccc_region_t *secret,
           isccc_sexpr_t **alistp)
{
    char key[256];
    isc_uint32_t len;
    isc_result_t result;
    isccc_sexpr_t *alist, *value;
    isc_boolean_t first_tag;
    unsigned char *checksum_rstart;

    REQUIRE(alistp != NULL && *alistp == NULL);

    checksum_rstart = NULL;
    first_tag = ISC_TRUE;
    alist = isccc_alist_create();
    if (alist == NULL)
        return (ISC_R_NOMEMORY);

    while (!REGION_EMPTY(*source)) {
        GET8(len, source->rstart);
        if (REGION_SIZE(*source) < len) {
            result = ISC_R_UNEXPECTEDEND;
            goto bad;
        }
        GET_MEM(key, len, source->rstart);
        key[len] = '\0';    /* Ensure NUL termination. */
        value = NULL;
        result = value_fromwire(source, &value);
        if (result != ISC_R_SUCCESS)
            goto bad;
        if (isccc_alist_define(alist, key, value) == NULL) {
            result = ISC_R_NOMEMORY;
            goto bad;
        }
        if (first_tag && secret != NULL && strcmp(key, "_auth") == 0)
            checksum_rstart = source->rstart;
        first_tag = ISC_FALSE;
    }

    *alistp = alist;

    if (secret != NULL) {
        if (checksum_rstart != NULL)
            return (verify(alist, checksum_rstart,
                       (source->rend - checksum_rstart),
                       secret));
        return (ISCCC_R_BADAUTH);
    }

    return (ISC_R_SUCCESS);

 bad:
    isccc_sexpr_free(&alist);

    return (result);
}

static isc_result_t
list_fromwire(isccc_region_t *source, isccc_sexpr_t **listp)
{
    isccc_sexpr_t *list, *value;
    isc_result_t result;

    list = NULL;
    while (!REGION_EMPTY(*source)) {
        value = NULL;
        result = value_fromwire(source, &value);
        if (result != ISC_R_SUCCESS) {
            isccc_sexpr_free(&list);
            return (result);
        }
        if (isccc_sexpr_addtolist(&list, value) == NULL) {
            isccc_sexpr_free(&value);
            isccc_sexpr_free(&list);
            return (result);
        }
    }

    *listp = list;

    return (ISC_R_SUCCESS);
}

isc_result_t
isccc_cc_fromwire(isccc_region_t *source, isccc_sexpr_t **alistp,
        isccc_region_t *secret)
{
    unsigned int size;
    isc_uint32_t version;

    size = REGION_SIZE(*source);
    if (size < 4)
        return (ISC_R_UNEXPECTEDEND);
    GET32(version, source->rstart);
    if (version != 1)
        return (ISCCC_R_UNKNOWNVERSION);

    return (table_fromwire(source, secret, alistp));
}

static isc_result_t
createmessage(isc_uint32_t version, const char *from, const char *to,
          isc_uint32_t serial, isccc_time_t now,
          isccc_time_t expires, isccc_sexpr_t **alistp,
          isc_boolean_t want_expires)
{
    isccc_sexpr_t *alist, *_ctrl, *_data;
    isc_result_t result;

    REQUIRE(alistp != NULL && *alistp == NULL);

    if (version != 1)
        return (ISCCC_R_UNKNOWNVERSION);

    alist = isccc_alist_create();
    if (alist == NULL)
        return (ISC_R_NOMEMORY);

    result = ISC_R_NOMEMORY;

    _ctrl = isccc_alist_create();
    _data = isccc_alist_create();
    if (_ctrl == NULL || _data == NULL)
        goto bad;
    if (isccc_alist_define(alist, "_ctrl", _ctrl) == NULL ||
        isccc_alist_define(alist, "_data", _data) == NULL)
        goto bad;
    if (isccc_cc_defineuint32(_ctrl, "_ser", serial) == NULL ||
        isccc_cc_defineuint32(_ctrl, "_tim", now) == NULL ||
        (want_expires &&
         isccc_cc_defineuint32(_ctrl, "_exp", expires) == NULL))
        goto bad;
    if (from != NULL &&
        isccc_cc_definestring(_ctrl, "_frm", from) == NULL)
        goto bad;
    if (to != NULL &&
        isccc_cc_definestring(_ctrl, "_to", to) == NULL)
        goto bad;

    *alistp = alist;

    return (ISC_R_SUCCESS);

 bad:
    isccc_sexpr_free(&alist);

    return (result);
}

isc_result_t
isccc_cc_createmessage(isc_uint32_t version, const char *from, const char *to,
             isc_uint32_t serial, isccc_time_t now,
             isccc_time_t expires, isccc_sexpr_t **alistp)
{
    return (createmessage(version, from, to, serial, now, expires,
                  alistp, ISC_TRUE));
}

isc_result_t
isccc_cc_createack(isccc_sexpr_t *message, isc_boolean_t ok,
         isccc_sexpr_t **ackp)
{
    char *_frm, *_to;
    isc_uint32_t serial;
    isccc_sexpr_t *ack, *_ctrl;
    isc_result_t result;
    isccc_time_t t;

    REQUIRE(ackp != NULL && *ackp == NULL);

    _ctrl = isccc_alist_lookup(message, "_ctrl");
    if (_ctrl == NULL ||
        isccc_cc_lookupuint32(_ctrl, "_ser", &serial) != ISC_R_SUCCESS ||
        isccc_cc_lookupuint32(_ctrl, "_tim", &t) != ISC_R_SUCCESS)
        return (ISC_R_FAILURE);
    /*
     * _frm and _to are optional.
     */
    _frm = NULL;
    (void)isccc_cc_lookupstring(_ctrl, "_frm", &_frm);
    _to = NULL;
    (void)isccc_cc_lookupstring(_ctrl, "_to", &_to);
    /*
     * Create the ack.
     */
    ack = NULL;
    result = createmessage(1, _to, _frm, serial, t, 0, &ack, ISC_FALSE);
    if (result != ISC_R_SUCCESS)
        return (result);

    _ctrl = isccc_alist_lookup(ack, "_ctrl");
    if (_ctrl == NULL)
        return (ISC_R_FAILURE);
    if (isccc_cc_definestring(ack, "_ack", (ok) ? "1" : "0") == NULL) {
        result = ISC_R_NOMEMORY;
        goto bad;
    }

    *ackp = ack;

    return (ISC_R_SUCCESS);

 bad:
    isccc_sexpr_free(&ack);

    return (result);
}

isc_boolean_t
isccc_cc_isack(isccc_sexpr_t *message)
{
    isccc_sexpr_t *_ctrl;

    _ctrl = isccc_alist_lookup(message, "_ctrl");
    if (_ctrl == NULL)
        return (ISC_FALSE);
    if (isccc_cc_lookupstring(_ctrl, "_ack", NULL) == ISC_R_SUCCESS)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_boolean_t
isccc_cc_isreply(isccc_sexpr_t *message)
{
    isccc_sexpr_t *_ctrl;

    _ctrl = isccc_alist_lookup(message, "_ctrl");
    if (_ctrl == NULL)
        return (ISC_FALSE);
    if (isccc_cc_lookupstring(_ctrl, "_rpl", NULL) == ISC_R_SUCCESS)
        return (ISC_TRUE);
    return (ISC_FALSE);
}

isc_result_t
isccc_cc_createresponse(isccc_sexpr_t *message, isccc_time_t now,
              isccc_time_t expires, isccc_sexpr_t **alistp)
{
    char *_frm, *_to, *type;
    isc_uint32_t serial;
    isccc_sexpr_t *alist, *_ctrl, *_data;
    isc_result_t result;

    REQUIRE(alistp != NULL && *alistp == NULL);

    _ctrl = isccc_alist_lookup(message, "_ctrl");
    _data = isccc_alist_lookup(message, "_data");
    if (_ctrl == NULL ||
        _data == NULL ||
        isccc_cc_lookupuint32(_ctrl, "_ser", &serial) != ISC_R_SUCCESS ||
        isccc_cc_lookupstring(_data, "type", &type) != ISC_R_SUCCESS)
        return (ISC_R_FAILURE);
    /*
     * _frm and _to are optional.
     */
    _frm = NULL;
    (void)isccc_cc_lookupstring(_ctrl, "_frm", &_frm);
    _to = NULL;
    (void)isccc_cc_lookupstring(_ctrl, "_to", &_to);
    /*
     * Create the response.
     */
    alist = NULL;
    result = isccc_cc_createmessage(1, _to, _frm, serial, now, expires,
                     &alist);
    if (result != ISC_R_SUCCESS)
        return (result);
    _ctrl = isccc_alist_lookup(alist, "_ctrl");
    if (_ctrl == NULL)
        return (ISC_R_FAILURE);
    _data = isccc_alist_lookup(alist, "_data");
    if (_data == NULL)
        return (ISC_R_FAILURE);
    if (isccc_cc_definestring(_ctrl, "_rpl", "1") == NULL ||
        isccc_cc_definestring(_data, "type", type) == NULL) {
        isccc_sexpr_free(&alist);
        return (ISC_R_NOMEMORY);
    }

    *alistp = alist;

    return (ISC_R_SUCCESS);
}

isccc_sexpr_t *
isccc_cc_definestring(isccc_sexpr_t *alist, const char *key, const char *str)
{
    size_t len;
    isccc_region_t r;

    len = strlen(str);
    DE_CONST(str, r.rstart);
    r.rend = r.rstart + len;

    return (isccc_alist_definebinary(alist, key, &r));
}

isccc_sexpr_t *
isccc_cc_defineuint32(isccc_sexpr_t *alist, const char *key, isc_uint32_t i)
{
    char b[100];
    size_t len;
    isccc_region_t r;

    snprintf(b, sizeof(b), "%u", i);
    len = strlen(b);
    r.rstart = (unsigned char *)b;
    r.rend = (unsigned char *)b + len;

    return (isccc_alist_definebinary(alist, key, &r));
}

isc_result_t
isccc_cc_lookupstring(isccc_sexpr_t *alist, const char *key, char **strp)
{
    isccc_sexpr_t *kv, *v;

    kv = isccc_alist_assq(alist, key);
    if (kv != NULL) {
        v = ISCCC_SEXPR_CDR(kv);
        if (isccc_sexpr_binaryp(v)) {
            if (strp != NULL)
                *strp = isccc_sexpr_tostring(v);
            return (ISC_R_SUCCESS);
        } else
            return (ISC_R_EXISTS);
    }

    return (ISC_R_NOTFOUND);
}

isc_result_t
isccc_cc_lookupuint32(isccc_sexpr_t *alist, const char *key,
               isc_uint32_t *uintp)
{
    isccc_sexpr_t *kv, *v;

    kv = isccc_alist_assq(alist, key);
    if (kv != NULL) {
        v = ISCCC_SEXPR_CDR(kv);
        if (isccc_sexpr_binaryp(v)) {
            if (uintp != NULL)
                *uintp = (isc_uint32_t)
                    strtoul(isccc_sexpr_tostring(v),
                        NULL, 10);
            return (ISC_R_SUCCESS);
        } else
            return (ISC_R_EXISTS);
    }

    return (ISC_R_NOTFOUND);
}

static void
symtab_undefine(char *key, unsigned int type, isccc_symvalue_t value,
        void *arg)
{
    UNUSED(type);
    UNUSED(value);
    UNUSED(arg);

    free(key);
}

static isc_boolean_t
symtab_clean(char *key, unsigned int type, isccc_symvalue_t value,
         void *arg)
{
    isccc_time_t *now;

    UNUSED(key);
    UNUSED(type);

    now = arg;

    if (*now < value.as_uinteger)
        return (ISC_FALSE);
    if ((*now - value.as_uinteger) < DUP_LIFETIME)
        return (ISC_FALSE);
    return (ISC_TRUE);
}

isc_result_t
isccc_cc_createsymtab(isccc_symtab_t **symtabp)
{
    return (isccc_symtab_create(11897, symtab_undefine, NULL, ISC_FALSE,
                  symtabp));
}

void
isccc_cc_cleansymtab(isccc_symtab_t *symtab, isccc_time_t now)
{
    isccc_symtab_foreach(symtab, symtab_clean, &now);
}

static isc_boolean_t
has_whitespace(const char *str)
{
    char c;

    if (str == NULL)
        return (ISC_FALSE);
    while ((c = *str++) != '\0') {
        if (c == ' ' || c == '\t' || c == '\n')
            return (ISC_TRUE);
    }
    return (ISC_FALSE);
}

isc_result_t
isccc_cc_checkdup(isccc_symtab_t *symtab, isccc_sexpr_t *message,
        isccc_time_t now)
{
    const char *_frm;
    const char *_to;
    char *_ser, *_tim, *tmp;
    isc_result_t result;
    char *key;
    size_t len;
    isccc_symvalue_t value;
    isccc_sexpr_t *_ctrl;

    _ctrl = isccc_alist_lookup(message, "_ctrl");
    if (_ctrl == NULL ||
        isccc_cc_lookupstring(_ctrl, "_ser", &_ser) != ISC_R_SUCCESS ||
        isccc_cc_lookupstring(_ctrl, "_tim", &_tim) != ISC_R_SUCCESS)
        return (ISC_R_FAILURE);
    /*
     * _frm and _to are optional.
     */
    if (isccc_cc_lookupstring(_ctrl, "_frm", &tmp) != ISC_R_SUCCESS)
        _frm = "";
    else
        _frm = tmp;
    if (isccc_cc_lookupstring(_ctrl, "_to", &tmp) != ISC_R_SUCCESS)
        _to = "";
    else
        _to = tmp;
    /*
     * Ensure there is no newline in any of the strings.  This is so
     * we can write them to a file later.
     */
    if (has_whitespace(_frm) || has_whitespace(_to) ||
        has_whitespace(_ser) || has_whitespace(_tim))
        return (ISC_R_FAILURE);
    len = strlen(_frm) + strlen(_to) + strlen(_ser) + strlen(_tim) + 4;
    key = malloc(len);
    if (key == NULL)
        return (ISC_R_NOMEMORY);
    snprintf(key, len, "%s;%s;%s;%s", _frm, _to, _ser, _tim);
    value.as_uinteger = now;
    result = isccc_symtab_define(symtab, key, ISCCC_SYMTYPE_CCDUP, value,
                   isccc_symexists_reject);
    if (result != ISC_R_SUCCESS) {
        free(key);
        return (result);
    }

    return (ISC_R_SUCCESS);
}