lib/dns/tsig.c

	tsig.c revision 0c70ab306505d89983186e9f8bb8647de55b5d04
/*
 * Copyright (C) 1999, 2000  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.
 */

/*
 * $Id: tsig.c,v 1.99 2001/01/09 14:32:44 marka Exp $
 * Principal Author: Brian Wellington
 */

#include <config.h>
#include <stdlib.h>     /* Required for abs(). */

#include <isc/buffer.h>
#include <isc/mem.h>
#include <isc/print.h>
#include <isc/string.h>     /* Required for HP/UX (and others?) */
#include <isc/util.h>

#include <dns/keyvalues.h>
#include <dns/log.h>
#include <dns/message.h>
#include <dns/rbt.h>
#include <dns/rdata.h>
#include <dns/rdatalist.h>
#include <dns/rdataset.h>
#include <dns/rdatastruct.h>
#include <dns/result.h>
#include <dns/tsig.h>

#include <dst/result.h>

#define TSIG_MAGIC      0x54534947  /* TSIG */
#define VALID_TSIG_KEY(x)   ISC_MAGIC_VALID(x, TSIG_MAGIC)

#define is_response(msg) (msg->flags & DNS_MESSAGEFLAG_QR)
#define algname_is_allocated(algname) \
    ((algname) != dns_tsig_hmacmd5_name && \
     (algname) != dns_tsig_gssapi_name && \
     (algname) != dns_tsig_gssapims_name)

#define BADTIMELEN 6

/* Copied from name.c */
struct dns_constname {
    dns_name_t name;
    unsigned char const_ndata[30];
    unsigned char const_offsets[5];
};

static struct dns_constname hmacmd5 = {
    {
        DNS_NAME_MAGIC,
        hmacmd5.const_ndata, 26, 5,
        DNS_NAMEATTR_READONLY | DNS_NAMEATTR_ABSOLUTE,
        hmacmd5.const_offsets, NULL,
        {(void *)-1, (void *)-1},
        {NULL, NULL}
    },
    { "\010hmac-md5\007sig-alg\003reg\003int" },    /* const_ndata */
    { 0, 9, 17, 21, 25 }                /* const_offsets */
};

dns_name_t *dns_tsig_hmacmd5_name = &hmacmd5.name;

static struct dns_constname gsstsig = {
    {
        DNS_NAME_MAGIC,
        gsstsig.const_ndata, 10, 2,
        DNS_NAMEATTR_READONLY | DNS_NAMEATTR_ABSOLUTE,
        gsstsig.const_offsets, NULL,
        {(void *)-1, (void *)-1},
        {NULL, NULL}
    },
    { "\010gss-tsig" },             /* const_ndata */
    { 0, 9 }                    /* const_offsets */
};

dns_name_t *dns_tsig_gssapi_name = &gsstsig.name;

/* It's nice of Microsoft to conform to their own standard. */
static struct dns_constname gsstsigms = {
    {
        DNS_NAME_MAGIC,
        gsstsigms.const_ndata, 19, 4,
        DNS_NAMEATTR_READONLY | DNS_NAMEATTR_ABSOLUTE,
        gsstsigms.const_offsets, NULL,
        {(void *)-1, (void *)-1},
        {NULL, NULL}
    },
    { "\003gss\011microsoft\003com" },      /* const_ndata */
    { 0, 4, 14, 18 }                /* const_offsets */
};

dns_name_t *dns_tsig_gssapims_name = &gsstsigms.name;

static isc_result_t
tsig_verify_tcp(isc_buffer_t *source, dns_message_t *msg);

static void
tsig_log(dns_tsigkey_t *key, int level, const char *fmt, ...) {
    va_list ap;
    char message[4096];
    char namestr[DNS_NAME_FORMATSIZE];

    if (isc_log_wouldlog(dns_lctx, level) == ISC_FALSE)
        return;
    if (key != NULL)
        dns_name_format(&key->name, namestr, sizeof(namestr));
    else
        strcpy(namestr, "<null>");
    va_start(ap, fmt);
    vsnprintf(message, sizeof(message), fmt, ap);
    va_end(ap);
    isc_log_write(dns_lctx, DNS_LOGCATEGORY_DNSSEC, DNS_LOGMODULE_TSIG,
              level, "tsig key '%s': %s", namestr, message);
}

isc_result_t
dns_tsigkey_createfromkey(dns_name_t *name, dns_name_t *algorithm,
              dst_key_t *dstkey, isc_boolean_t generated,
              dns_name_t *creator, isc_stdtime_t inception,
              isc_stdtime_t expire, isc_mem_t *mctx,
              dns_tsig_keyring_t *ring, dns_tsigkey_t **key)
{
    dns_tsigkey_t *tkey;
    isc_result_t ret;

    REQUIRE(key == NULL || *key == NULL);
    REQUIRE(name != NULL);
    REQUIRE(algorithm != NULL);
    REQUIRE(mctx != NULL);

    tkey = (dns_tsigkey_t *) isc_mem_get(mctx, sizeof(dns_tsigkey_t));
    if (tkey == NULL)
        return (ISC_R_NOMEMORY);

    dns_name_init(&tkey->name, NULL);
    ret = dns_name_dup(name, mctx, &tkey->name);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_key;
    dns_name_downcase(&tkey->name, &tkey->name, NULL);

    if (dns_name_equal(algorithm, DNS_TSIG_HMACMD5_NAME))
        tkey->algorithm = DNS_TSIG_HMACMD5_NAME;
    else if (dns_name_equal(algorithm, DNS_TSIG_GSSAPI_NAME))
        tkey->algorithm = DNS_TSIG_GSSAPI_NAME;
    else if (dns_name_equal(algorithm, DNS_TSIG_GSSAPIMS_NAME))
        tkey->algorithm = DNS_TSIG_GSSAPIMS_NAME;
    else {
        if (key != NULL) {
            ret = DNS_R_BADALG;
            goto cleanup_name;
        }
        tkey->algorithm = isc_mem_get(mctx, sizeof(dns_name_t));
        if (tkey->algorithm == NULL) {
            ret = ISC_R_NOMEMORY;
            goto cleanup_name;
        }
        dns_name_init(tkey->algorithm, NULL);
        ret = dns_name_dup(algorithm, mctx, tkey->algorithm);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_algorithm;
        dns_name_downcase(tkey->algorithm, tkey->algorithm, NULL);
    }

    if (creator != NULL) {
        tkey->creator = isc_mem_get(mctx, sizeof(dns_name_t));
        if (tkey->creator == NULL) {
            ret = ISC_R_NOMEMORY;
            goto cleanup_algorithm;
        }
        dns_name_init(tkey->creator, NULL);
        ret = dns_name_dup(creator, mctx, tkey->creator);
        if (ret != ISC_R_SUCCESS) {
            isc_mem_put(mctx, tkey->creator, sizeof(dns_name_t));
            goto cleanup_algorithm;
        }
    } else
        tkey->creator = NULL;

    tkey->key = dstkey;
    tkey->ring = ring;
    tkey->refs = 0;

    if (ring != NULL) {
        RWLOCK(&ring->lock, isc_rwlocktype_write);
        ret = dns_rbt_addname(ring->keys, name, tkey);
        if (ret != ISC_R_SUCCESS) {
            RWUNLOCK(&ring->lock, isc_rwlocktype_write);
            goto cleanup_algorithm;
        }
        tkey->refs++;
        RWUNLOCK(&ring->lock, isc_rwlocktype_write);
    }

    if (key != NULL)
        tkey->refs++;
    tkey->generated = generated;
    tkey->inception = inception;
    tkey->expire = expire;
    tkey->mctx = mctx;
    ret = isc_mutex_init(&tkey->lock);
    if (ret != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_mutex_init() failed: %s",
                 isc_result_totext(ret));
        return (ISC_R_UNEXPECTED);
    }

    tkey->magic = TSIG_MAGIC;

    if (dstkey != NULL && dst_key_size(dstkey) < 64) {
        char namestr[DNS_NAME_FORMATSIZE];
        dns_name_format(name, namestr, sizeof(namestr));
        isc_log_write(dns_lctx, DNS_LOGCATEGORY_DNSSEC,
                  DNS_LOGMODULE_TSIG, ISC_LOG_INFO,
                  "the TSIG key for '%s' is too short to "
                  "be secure", namestr);
    }
    if (key != NULL)
        *key = tkey;

    return (ISC_R_SUCCESS);

 cleanup_algorithm:
    if (algname_is_allocated(tkey->algorithm)) {
        if (dns_name_dynamic(tkey->algorithm))
            dns_name_free(tkey->algorithm, mctx);
        isc_mem_put(mctx, tkey->algorithm, sizeof(dns_name_t));
    }
 cleanup_name:
    dns_name_free(&tkey->name, mctx);
 cleanup_key:
    isc_mem_put(mctx, tkey, sizeof(dns_tsigkey_t));

    return (ret);
}

isc_result_t
dns_tsigkey_create(dns_name_t *name, dns_name_t *algorithm,
           unsigned char *secret, int length, isc_boolean_t generated,
           dns_name_t *creator, isc_stdtime_t inception,
           isc_stdtime_t expire, isc_mem_t *mctx,
           dns_tsig_keyring_t *ring, dns_tsigkey_t **key)
{
    dst_key_t *dstkey = NULL;
    isc_result_t result;

    REQUIRE(length >= 0);
    if (length > 0)
        REQUIRE(secret != NULL);

    if (!dns_name_equal(algorithm, DNS_TSIG_HMACMD5_NAME) && length > 0)
        return (DNS_R_BADALG);

    if (length > 0) {
        isc_buffer_t b;

        isc_buffer_init(&b, secret, length);
        isc_buffer_add(&b, length);
        result = dst_key_frombuffer(name, DST_ALG_HMACMD5,
                        DNS_KEYOWNER_ENTITY,
                        DNS_KEYPROTO_DNSSEC,
                        dns_rdataclass_in,
                        &b, mctx, &dstkey);
        if (result != ISC_R_SUCCESS)
            return (result);
    }
    result = dns_tsigkey_createfromkey(name, algorithm, dstkey,
                       generated, creator,
                       inception, expire, mctx, ring, key);
    if (result != ISC_R_SUCCESS && dstkey != NULL)
        dst_key_free(&dstkey);
    return (result);
}

void
dns_tsigkey_attach(dns_tsigkey_t *source, dns_tsigkey_t **targetp) {
    REQUIRE(VALID_TSIG_KEY(source));
    REQUIRE(targetp != NULL && *targetp == NULL);

    LOCK(&source->lock);
    source->refs++;
    UNLOCK(&source->lock);
    *targetp = source;
}

static void
tsigkey_free(dns_tsigkey_t *key) {
    REQUIRE(VALID_TSIG_KEY(key));

    key->magic = 0;
    dns_name_free(&key->name, key->mctx);
    if (algname_is_allocated(key->algorithm)) {
        dns_name_free(key->algorithm, key->mctx);
        isc_mem_put(key->mctx, key->algorithm, sizeof(dns_name_t));
    }
    if (key->key != NULL)
        dst_key_free(&key->key);
    if (key->creator != NULL) {
        dns_name_free(key->creator, key->mctx);
        isc_mem_put(key->mctx, key->creator, sizeof(dns_name_t));
    }
    DESTROYLOCK(&key->lock);
    isc_mem_put(key->mctx, key, sizeof(dns_tsigkey_t));
}

void
dns_tsigkey_detach(dns_tsigkey_t **keyp) {
    dns_tsigkey_t *key;
    isc_boolean_t should_free = ISC_FALSE;

    REQUIRE(keyp != NULL);
    REQUIRE(VALID_TSIG_KEY(*keyp));
    key = *keyp;
    *keyp = NULL;

    LOCK(&key->lock);
    key->refs--;
    if (key->refs == 0)
        should_free = ISC_TRUE;
    UNLOCK(&key->lock);
    if (should_free)
        tsigkey_free(key);
}

void
dns_tsigkey_setdeleted(dns_tsigkey_t *key) {
    REQUIRE(VALID_TSIG_KEY(key));
    REQUIRE(key->ring != NULL);

    RWLOCK(&key->ring->lock, isc_rwlocktype_write);
    (void)dns_rbt_deletename(key->ring->keys, &key->name, ISC_FALSE);
    RWUNLOCK(&key->ring->lock, isc_rwlocktype_write);
}

static void
buffer_putuint48(isc_buffer_t *b, isc_uint64_t val) {
    isc_uint16_t valhi;
    isc_uint32_t vallo;

    valhi = (isc_uint16_t)(val >> 32);
    vallo = (isc_uint32_t)(val & 0xFFFFFFFF);
    isc_buffer_putuint16(b, valhi);
    isc_buffer_putuint32(b, vallo);
}

isc_result_t
dns_tsig_sign(dns_message_t *msg) {
    dns_tsigkey_t *key;
    dns_rdata_any_tsig_t tsig, querytsig;
    unsigned char data[128];
    isc_buffer_t databuf, sigbuf;
    isc_buffer_t *dynbuf;
    dns_name_t *owner;
    dns_rdata_t *rdata;
    dns_rdatalist_t *datalist;
    dns_rdataset_t *dataset;
    isc_region_t r;
    isc_stdtime_t now;
    isc_mem_t *mctx;
    dst_context_t *ctx = NULL;
    isc_result_t ret;
    unsigned char badtimedata[BADTIMELEN];
    unsigned int sigsize = 0;

    REQUIRE(msg != NULL);
    REQUIRE(VALID_TSIG_KEY(dns_message_gettsigkey(msg)));

    /*
     * If this is a response, there should be a query tsig.
     */
    if (is_response(msg) && msg->querytsig == NULL)
        return (DNS_R_EXPECTEDTSIG);

    dynbuf = NULL;

    mctx = msg->mctx;
    key = dns_message_gettsigkey(msg);

    tsig.mctx = mctx;
    tsig.common.rdclass = dns_rdataclass_any;
    tsig.common.rdtype = dns_rdatatype_tsig;
    ISC_LINK_INIT(&tsig.common, link);
    dns_name_init(&tsig.algorithm, NULL);
    dns_name_clone(key->algorithm, &tsig.algorithm);

    isc_stdtime_get(&now);
    tsig.timesigned = now;
    tsig.fudge = DNS_TSIG_FUDGE;

    tsig.originalid = msg->id;

    isc_buffer_init(&databuf, data, sizeof(data));

    if (is_response(msg))
        tsig.error = msg->querytsigstatus;
    else
        tsig.error = dns_rcode_noerror;

    if (tsig.error != dns_tsigerror_badtime) {
        tsig.otherlen = 0;
        tsig.other = NULL;
    } else {
        isc_buffer_t otherbuf;

        tsig.otherlen = BADTIMELEN;
        tsig.other = badtimedata;
        isc_buffer_init(&otherbuf, tsig.other, tsig.otherlen);
        buffer_putuint48(&otherbuf, tsig.timesigned);
    }

    if (key->key != NULL && tsig.error != dns_tsigerror_badsig) {
        unsigned char header[DNS_MESSAGE_HEADERLEN];
        isc_buffer_t headerbuf;

        ret = dst_context_create(key->key, mctx, &ctx);
        if (ret != ISC_R_SUCCESS)
            return (ret);

        /*
         * If this is a response, digest the query signature.
         */
        if (is_response(msg)) {
            dns_rdata_t querytsigrdata = DNS_RDATA_INIT;

            ret = dns_rdataset_first(msg->querytsig);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;
            dns_rdataset_current(msg->querytsig, &querytsigrdata);
            ret = dns_rdata_tostruct(&querytsigrdata, &querytsig,
                         NULL);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;
            isc_buffer_putuint16(&databuf, querytsig.siglen);
            if (isc_buffer_availablelength(&databuf) <
                querytsig.siglen)
            {
                ret = ISC_R_NOSPACE;
                goto cleanup_context;
            }
            isc_buffer_putmem(&databuf, querytsig.signature,
                      querytsig.siglen);
            isc_buffer_usedregion(&databuf, &r);
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;
        }

        /*
         * Digest the header.
         */
        isc_buffer_init(&headerbuf, header, sizeof(header));
        dns_message_renderheader(msg, &headerbuf);
        isc_buffer_usedregion(&headerbuf, &r);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        /*
         * Digest the remainder of the message.
         */
        isc_buffer_usedregion(msg->buffer, &r);
        isc_region_consume(&r, DNS_MESSAGE_HEADERLEN);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        if (msg->tcp_continuation == 0) {
            /*
             * Digest the name, class, ttl, alg.
             */
            dns_name_toregion(&key->name, &r);
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;

            isc_buffer_clear(&databuf);
            isc_buffer_putuint16(&databuf, dns_rdataclass_any);
            isc_buffer_putuint32(&databuf, 0); /* ttl */
            isc_buffer_usedregion(&databuf, &r);
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;

            dns_name_toregion(&tsig.algorithm, &r);
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;

        }
        /* Digest the timesigned and fudge */
        isc_buffer_clear(&databuf);
        if (tsig.error == dns_tsigerror_badtime)
            tsig.timesigned = querytsig.timesigned;
        buffer_putuint48(&databuf, tsig.timesigned);
        isc_buffer_putuint16(&databuf, tsig.fudge);
        isc_buffer_usedregion(&databuf, &r);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        if (msg->tcp_continuation == 0) {
            /*
             * Digest the error and other data length.
             */
            isc_buffer_clear(&databuf);
            isc_buffer_putuint16(&databuf, tsig.error);
            isc_buffer_putuint16(&databuf, tsig.otherlen);

            isc_buffer_usedregion(&databuf, &r);
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;

            /*
             * Digest the error and other data.
             */
            if (tsig.otherlen > 0) {
                r.length = tsig.otherlen;
                r.base = tsig.other;
                ret = dst_context_adddata(ctx, &r);
                if (ret != ISC_R_SUCCESS)
                    goto cleanup_context;
            }
        }

        ret = dst_key_sigsize(key->key, &sigsize);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;
        tsig.signature = (unsigned char *) isc_mem_get(mctx, sigsize);
        if (tsig.signature == NULL) {
            ret = ISC_R_NOMEMORY;
            goto cleanup_context;
        }

        isc_buffer_init(&sigbuf, tsig.signature, sigsize);
        ret = dst_context_sign(ctx, &sigbuf);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_signature;
        dst_context_destroy(&ctx);
        tsig.siglen = isc_buffer_usedlength(&sigbuf);
    } else {
        tsig.siglen = 0;
        tsig.signature = NULL;
    }

    rdata = NULL;
    ret = dns_message_gettemprdata(msg, &rdata);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_signature;
    ret = isc_buffer_allocate(msg->mctx, &dynbuf, 512);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_signature;
    ret = dns_rdata_fromstruct(rdata, dns_rdataclass_any,
                   dns_rdatatype_tsig, &tsig, dynbuf);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_dynbuf;

    dns_message_takebuffer(msg, &dynbuf);

    if (tsig.signature != NULL) {
        isc_mem_put(mctx, tsig.signature, sigsize);
        tsig.signature = NULL;
    }

    owner = NULL;
    ret = dns_message_gettempname(msg, &owner);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_dynbuf;
    dns_name_init(owner, NULL);
    ret = dns_name_dup(&key->name, msg->mctx, owner);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_owner;

    datalist = NULL;
    ret = dns_message_gettemprdatalist(msg, &datalist);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_dynbuf;
    datalist->rdclass = dns_rdataclass_any;
    datalist->type = dns_rdatatype_tsig;
    datalist->covers = 0;
    datalist->ttl = 0;
    ISC_LIST_INIT(datalist->rdata);
    ISC_LIST_APPEND(datalist->rdata, rdata, link);
    dataset = NULL;
    ret = dns_message_gettemprdataset(msg, &dataset);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_owner;
    dns_rdataset_init(dataset);
    dns_rdatalist_tordataset(datalist, dataset);
    msg->tsig = dataset;
    msg->tsigname = owner;

    return (ISC_R_SUCCESS);

cleanup_owner:
    if (owner != NULL)
        dns_message_puttempname(msg, &owner);
cleanup_dynbuf:
    if (dynbuf != NULL)
        isc_buffer_free(&dynbuf);
cleanup_signature:
    if (tsig.signature != NULL)
        isc_mem_put(mctx, tsig.signature, sigsize);
cleanup_context:
    if (ctx != NULL)
        dst_context_destroy(&ctx);
    return (ret);
}

isc_result_t
dns_tsig_verify(isc_buffer_t *source, dns_message_t *msg,
        dns_tsig_keyring_t *ring1, dns_tsig_keyring_t *ring2)
{
    dns_rdata_any_tsig_t tsig, querytsig;
    isc_region_t r, source_r, header_r, sig_r;
    isc_buffer_t databuf;
    unsigned char data[32];
    dns_name_t *keyname;
    dns_rdata_t rdata = DNS_RDATA_INIT;
    isc_stdtime_t now;
    isc_result_t ret;
    dns_tsigkey_t *tsigkey;
    dst_key_t *key = NULL;
    unsigned char header[DNS_MESSAGE_HEADERLEN];
    dst_context_t *ctx = NULL;
    isc_mem_t *mctx;
    isc_uint16_t addcount, id;

    REQUIRE(source != NULL);
    REQUIRE(DNS_MESSAGE_VALID(msg));
    tsigkey = dns_message_gettsigkey(msg);
    REQUIRE(tsigkey == NULL || VALID_TSIG_KEY(tsigkey));

    msg->verify_attempted = 1;

    if (msg->tcp_continuation)
        return (tsig_verify_tcp(source, msg));

    /*
     * There should be a TSIG record...
     */
    if (msg->tsig == NULL)
        return (DNS_R_EXPECTEDTSIG);

    /*
     * If this is a response and there's no key or query TSIG, there
     * shouldn't be one on the response.
     */
    if (is_response(msg) &&
        (tsigkey == NULL || msg->querytsig == NULL))
        return (DNS_R_UNEXPECTEDTSIG);

    mctx = msg->mctx;

    /*
     * If we're here, we know the message is well formed and contains a
     * TSIG record.
     */

    keyname = msg->tsigname;
    ret = dns_rdataset_first(msg->tsig);
    if (ret != ISC_R_SUCCESS)
        return (ret);
    dns_rdataset_current(msg->tsig, &rdata);
    ret = dns_rdata_tostruct(&rdata, &tsig, NULL);
    if (ret != ISC_R_SUCCESS)
        return (ret);
    dns_rdata_reset(&rdata);
    if (is_response(msg)) {
        ret = dns_rdataset_first(msg->querytsig);
        if (ret != ISC_R_SUCCESS)
            return (ret);
        dns_rdataset_current(msg->querytsig, &rdata);
        ret = dns_rdata_tostruct(&rdata, &querytsig, NULL);
        if (ret != ISC_R_SUCCESS)
            return (ret);
    }

    /*
     * Do the key name and algorithm match that of the query?
     */
    if (is_response(msg) &&
        (!dns_name_equal(keyname, &tsigkey->name) ||
         !dns_name_equal(&tsig.algorithm, &querytsig.algorithm)))
    {
        msg->tsigstatus = dns_tsigerror_badkey;
        tsig_log(msg->tsigkey, 2,
             "key name and algorithm do not match");
        return (DNS_R_TSIGVERIFYFAILURE);
    }

    /*
     * Get the current time.
     */
    isc_stdtime_get(&now);

    /*
     * Find dns_tsigkey_t based on keyname.
     */
    if (tsigkey == NULL) {
        ret = ISC_R_NOTFOUND;
        if (ring1 != NULL)
            ret = dns_tsigkey_find(&tsigkey, keyname,
                           &tsig.algorithm, ring1);
        if (ret == ISC_R_NOTFOUND && ring2 != NULL)
            ret = dns_tsigkey_find(&tsigkey, keyname,
                           &tsig.algorithm, ring2);
        if (ret != ISC_R_SUCCESS) {
            msg->tsigstatus = dns_tsigerror_badkey;
            ret = dns_tsigkey_create(keyname, &tsig.algorithm,
                         NULL, 0, ISC_FALSE, NULL,
                         now, now,
                         mctx, NULL, &msg->tsigkey);
            if (ret != ISC_R_SUCCESS)
                return (ret);
            tsig_log(msg->tsigkey, 2, "unknown key");
            return (DNS_R_TSIGVERIFYFAILURE);
        }
        msg->tsigkey = tsigkey;
    }

    key = tsigkey->key;

    /*
     * Is the time ok?
     */
    if (abs(now - tsig.timesigned) > tsig.fudge) {
        msg->tsigstatus = dns_tsigerror_badtime;
        if (now > tsig.timesigned + tsig.fudge)
            tsig_log(msg->tsigkey, 2,
                 "signature has expired");
        else
            tsig_log(msg->tsigkey, 2,
                 "signature is in the future");
        return (DNS_R_TSIGVERIFYFAILURE);
    }

    if (tsig.siglen > 0) {
        sig_r.base = tsig.signature;
        sig_r.length = tsig.siglen;

        ret = dst_context_create(key, mctx, &ctx);
        if (ret != ISC_R_SUCCESS)
            return (ret);

        if (is_response(msg)) {
            isc_buffer_init(&databuf, data, sizeof(data));
            isc_buffer_putuint16(&databuf, querytsig.siglen);
            isc_buffer_usedregion(&databuf, &r);
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;
            if (querytsig.siglen > 0) {
                r.length = querytsig.siglen;
                r.base = querytsig.signature;
                ret = dst_context_adddata(ctx, &r);
                if (ret != ISC_R_SUCCESS)
                    goto cleanup_context;
            }
        }

        /*
         * Extract the header.
         */
        isc_buffer_usedregion(source, &r);
        memcpy(header, r.base, DNS_MESSAGE_HEADERLEN);
        isc_region_consume(&r, DNS_MESSAGE_HEADERLEN);

        /*
         * Decrement the additional field counter.
         */
        memcpy(&addcount, &header[DNS_MESSAGE_HEADERLEN - 2], 2);
        addcount = htons(ntohs(addcount) - 1);
        memcpy(&header[DNS_MESSAGE_HEADERLEN - 2], &addcount, 2);

        /*
         * Put in the original id.
         */
        id = htons(tsig.originalid);
        memcpy(&header[0], &id, 2);

        /*
         * Digest the modified header.
         */
        header_r.base = (unsigned char *) header;
        header_r.length = DNS_MESSAGE_HEADERLEN;
        ret = dst_context_adddata(ctx, &header_r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        /*
         * Digest all non-TSIG records.
         */
        isc_buffer_usedregion(source, &source_r);
        r.base = source_r.base + DNS_MESSAGE_HEADERLEN;
        r.length = msg->sigstart - DNS_MESSAGE_HEADERLEN;
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        /*
         * Digest the key name.
         */
        dns_name_toregion(&tsigkey->name, &r);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        isc_buffer_init(&databuf, data, sizeof(data));
        isc_buffer_putuint16(&databuf, tsig.common.rdclass);
        isc_buffer_putuint32(&databuf, msg->tsig->ttl);
        isc_buffer_usedregion(&databuf, &r);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        /*
         * Digest the key algorithm.
         */
        dns_name_toregion(tsigkey->algorithm, &r);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        isc_buffer_clear(&databuf);
        buffer_putuint48(&databuf, tsig.timesigned);
        isc_buffer_putuint16(&databuf, tsig.fudge);
        isc_buffer_putuint16(&databuf, tsig.error);
        isc_buffer_putuint16(&databuf, tsig.otherlen);
        isc_buffer_usedregion(&databuf, &r);
        ret = dst_context_adddata(ctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        if (tsig.otherlen > 0) {
            r.base = tsig.other;
            r.length = tsig.otherlen;
            ret = dst_context_adddata(ctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;
        }

        ret = dst_context_verify(ctx, &sig_r);
        if (ret == DST_R_VERIFYFAILURE) {
            msg->tsigstatus = dns_tsigerror_badsig;
            ret = DNS_R_TSIGVERIFYFAILURE;
            tsig_log(msg->tsigkey, 2,
                 "signature failed to verify");
            goto cleanup_context;
        } else if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        dst_context_destroy(&ctx);
    } else if (tsig.error != dns_tsigerror_badsig &&
           tsig.error != dns_tsigerror_badkey)
    {
        msg->tsigstatus = dns_tsigerror_badsig;
        tsig_log(msg->tsigkey, 2, "signature was empty");
        return (DNS_R_TSIGVERIFYFAILURE);
    }

    msg->tsigstatus = dns_rcode_noerror;

    if (tsig.error != dns_rcode_noerror)
        return (DNS_R_TSIGERRORSET);

    msg->verified_sig = 1;

    return (ISC_R_SUCCESS);

cleanup_context:
    if (ctx != NULL)
        dst_context_destroy(&ctx);

    return (ret);
}

static isc_result_t
tsig_verify_tcp(isc_buffer_t *source, dns_message_t *msg) {
    dns_rdata_any_tsig_t tsig, querytsig;
    isc_region_t r, source_r, header_r, sig_r;
    isc_buffer_t databuf;
    unsigned char data[32];
    dns_name_t *keyname;
    dns_rdata_t rdata = DNS_RDATA_INIT;
    isc_stdtime_t now;
    isc_result_t ret;
    dns_tsigkey_t *tsigkey;
    dst_key_t *key = NULL;
    unsigned char header[DNS_MESSAGE_HEADERLEN];
    isc_uint16_t addcount, id;
    isc_boolean_t has_tsig = ISC_FALSE;
    isc_mem_t *mctx;

    REQUIRE(source != NULL);
    REQUIRE(msg != NULL);
    REQUIRE(dns_message_gettsigkey(msg) != NULL);
    REQUIRE(msg->tcp_continuation == 1);
    REQUIRE(is_response(msg));
    REQUIRE(msg->querytsig != NULL);

    mctx = msg->mctx;

    tsigkey = dns_message_gettsigkey(msg);

    /*
     * Extract and parse the previous TSIG
     */
    ret = dns_rdataset_first(msg->querytsig);
    if (ret != ISC_R_SUCCESS)
        return (ret);
    dns_rdataset_current(msg->querytsig, &rdata);
    ret = dns_rdata_tostruct(&rdata, &querytsig, NULL);
    if (ret != ISC_R_SUCCESS)
        return (ret);
    dns_rdata_reset(&rdata);

    /*
     * If there is a TSIG in this message, do some checks.
     */
    if (msg->tsig != NULL) {
        has_tsig = ISC_TRUE;

        keyname = msg->tsigname;
        ret = dns_rdataset_first(msg->tsig);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_querystruct;
        dns_rdataset_current(msg->tsig, &rdata);
        ret = dns_rdata_tostruct(&rdata, &tsig, NULL);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_querystruct;

        /*
         * Do the key name and algorithm match that of the query?
         */
        if (!dns_name_equal(keyname, &tsigkey->name) ||
            !dns_name_equal(&tsig.algorithm, &querytsig.algorithm))
        {
            msg->tsigstatus = dns_tsigerror_badkey;
            ret = DNS_R_TSIGVERIFYFAILURE;
            tsig_log(msg->tsigkey, 2,
                 "key name and algorithm do not match");
            goto cleanup_querystruct;
        }

        /*
         * Is the time ok?
         */
        isc_stdtime_get(&now);
        if (abs(now - tsig.timesigned) > tsig.fudge) {
            msg->tsigstatus = dns_tsigerror_badtime;
            ret = DNS_R_TSIGVERIFYFAILURE;
            if (now > tsig.timesigned + tsig.fudge)
                tsig_log(msg->tsigkey, 2,
                     "signature has expired");
            else
                tsig_log(msg->tsigkey, 2,
                     "signature is in the future");
            goto cleanup_querystruct;
        }
    }

    key = tsigkey->key;

    if (msg->tsigctx == NULL) {
        ret = dst_context_create(key, mctx, &msg->tsigctx);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_querystruct;

        /*
         * Digest the length of the query signature
         */
        isc_buffer_init(&databuf, data, sizeof(data));
        isc_buffer_putuint16(&databuf, querytsig.siglen);
        isc_buffer_usedregion(&databuf, &r);
        ret = dst_context_adddata(msg->tsigctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        /*
         * Digest the data of the query signature
         */
        if (querytsig.siglen > 0) {
            r.length = querytsig.siglen;
            r.base = querytsig.signature;
            ret = dst_context_adddata(msg->tsigctx, &r);
            if (ret != ISC_R_SUCCESS)
                goto cleanup_context;
        }
    }

    /*
     * Extract the header.
     */
    isc_buffer_usedregion(source, &r);
    memcpy(header, r.base, DNS_MESSAGE_HEADERLEN);
    isc_region_consume(&r, DNS_MESSAGE_HEADERLEN);

    /*
     * Decrement the additional field counter if necessary.
     */
    if (has_tsig) {
        memcpy(&addcount, &header[DNS_MESSAGE_HEADERLEN - 2], 2);
        addcount = htons(ntohs(addcount) - 1);
        memcpy(&header[DNS_MESSAGE_HEADERLEN - 2], &addcount, 2);
    }

    /*
     * Put in the original id.
     */
    /* XXX Can TCP transfers be forwarded?  How would that work? */
    if (has_tsig) {
        id = htons(tsig.originalid);
        memcpy(&header[0], &id, 2);
    }

    /*
     * Digest the modified header.
     */
    header_r.base = (unsigned char *) header;
    header_r.length = DNS_MESSAGE_HEADERLEN;
    ret = dst_context_adddata(msg->tsigctx, &header_r);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_context;

    /*
     * Digest all non-TSIG records.
     */
    isc_buffer_usedregion(source, &source_r);
    r.base = source_r.base + DNS_MESSAGE_HEADERLEN;
    if (has_tsig)
        r.length = msg->sigstart - DNS_MESSAGE_HEADERLEN;
    else
        r.length = source_r.length - DNS_MESSAGE_HEADERLEN;
    ret = dst_context_adddata(msg->tsigctx, &r);
    if (ret != ISC_R_SUCCESS)
        goto cleanup_context;

    /*
     * Digest the time signed and fudge.
     */
    if (has_tsig) {
        isc_buffer_init(&databuf, data, sizeof(data));
        buffer_putuint48(&databuf, tsig.timesigned);
        isc_buffer_putuint16(&databuf, tsig.fudge);
        isc_buffer_usedregion(&databuf, &r);
        ret = dst_context_adddata(msg->tsigctx, &r);
        if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        sig_r.base = tsig.signature;
        sig_r.length = tsig.siglen;
        if (tsig.siglen == 0) {
            if (tsig.error != dns_rcode_noerror)
                ret = DNS_R_TSIGERRORSET;
            else {
                tsig_log(msg->tsigkey, 2,
                     "signature is empty");
                ret = DNS_R_TSIGVERIFYFAILURE;
            }
            goto cleanup_context;
        }

        ret = dst_context_verify(msg->tsigctx, &sig_r);
        if (ret == DST_R_VERIFYFAILURE) {
            msg->tsigstatus = dns_tsigerror_badsig;
            tsig_log(msg->tsigkey, 2,
                 "signature failed to verify");
            ret = DNS_R_TSIGVERIFYFAILURE;
            goto cleanup_context;
        }
        else if (ret != ISC_R_SUCCESS)
            goto cleanup_context;

        dst_context_destroy(&msg->tsigctx);
    }

    msg->tsigstatus = dns_rcode_noerror;
    return (ISC_R_SUCCESS);

 cleanup_context:
    dst_context_destroy(&msg->tsigctx);

 cleanup_querystruct:
    dns_rdata_freestruct(&querytsig);

    return (ret);

}

isc_result_t
dns_tsigkey_find(dns_tsigkey_t **tsigkey, dns_name_t *name,
         dns_name_t *algorithm, dns_tsig_keyring_t *ring)
{
    dns_tsigkey_t *key;
    isc_stdtime_t now;
    isc_result_t result;

    REQUIRE(tsigkey != NULL);
    REQUIRE(*tsigkey == NULL);
    REQUIRE(name != NULL);
    REQUIRE(ring != NULL);

    isc_stdtime_get(&now);
    RWLOCK(&ring->lock, isc_rwlocktype_read);
    key = NULL;
    result = dns_rbt_findname(ring->keys, name, 0, NULL, (void *)&key);
    if (result == DNS_R_PARTIALMATCH || result == ISC_R_NOTFOUND) {
        RWUNLOCK(&ring->lock, isc_rwlocktype_read);
        return (ISC_R_NOTFOUND);
    }
    if (algorithm != NULL && !dns_name_equal(key->algorithm, algorithm)) {
        RWUNLOCK(&ring->lock, isc_rwlocktype_read);
        return (ISC_R_NOTFOUND);
    }
    if (key->inception != key->expire && key->expire < now) {
        /*
         * The key has expired.
         */
        RWUNLOCK(&ring->lock, isc_rwlocktype_read);
        LOCK(&key->lock);
        key->refs--;
        UNLOCK(&key->lock);
        RWLOCK(&ring->lock, isc_rwlocktype_write);
        (void) dns_rbt_deletename(ring->keys, name, ISC_FALSE);
        RWUNLOCK(&ring->lock, isc_rwlocktype_write);
        return (ISC_R_NOTFOUND);
    }

    LOCK(&key->lock);
    key->refs++;
    UNLOCK(&key->lock);
    RWUNLOCK(&ring->lock, isc_rwlocktype_read);
    *tsigkey = key;
    return (ISC_R_SUCCESS);
}

static void
free_tsignode(void *node, void *_unused) {
    dns_tsigkey_t *key;

    UNUSED(_unused);

    REQUIRE(node != NULL);

    key = node;
    dns_tsigkey_detach(&key);
}

isc_result_t
dns_tsigkeyring_create(isc_mem_t *mctx, dns_tsig_keyring_t **ringp) {
    isc_result_t result;
    dns_tsig_keyring_t *ring;

    REQUIRE(mctx != NULL);
    REQUIRE(ringp != NULL);
    REQUIRE(*ringp == NULL);

    ring = isc_mem_get(mctx, sizeof(dns_tsig_keyring_t));
    if (ring == NULL)
        return (ISC_R_NOMEMORY);

    result = isc_rwlock_init(&ring->lock, 0, 0);
    if (result != ISC_R_SUCCESS) {
        UNEXPECTED_ERROR(__FILE__, __LINE__,
                 "isc_rwlock_init() failed: %s",
                 isc_result_totext(result));
        return (ISC_R_UNEXPECTED);
    }

    ring->keys = NULL;
    result = dns_rbt_create(mctx, free_tsignode, NULL, &ring->keys);
    if (result != ISC_R_SUCCESS) {
        isc_rwlock_destroy(&ring->lock);
        isc_mem_put(mctx, ring, sizeof(dns_tsig_keyring_t));
        return (result);
    }

    ring->mctx = mctx;

    *ringp = ring;
    return (ISC_R_SUCCESS);
}

void
dns_tsigkeyring_destroy(dns_tsig_keyring_t **ringp) {
    dns_tsig_keyring_t *ring;

    REQUIRE(ringp != NULL);
    REQUIRE(*ringp != NULL);

    ring = *ringp;
    *ringp = NULL;

    dns_rbt_destroy(&ring->keys);
    isc_rwlock_destroy(&ring->lock);
    isc_mem_put(ring->mctx, ring, sizeof(dns_tsig_keyring_t));
}