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/* Copyright (C) 2011 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>
#include <assert.h>
#include <time.h>
#include "common/errcode.h"
#include "libknot/dnssec/rrset-sign.h"
#include "libknot/dnssec/sig0.h"
#include "libknot/dnssec/sign.h"
#include "libknot/util/wire.h"
/*!
* \brief Lifetime fudge of the SIG(0) packets in seconds.
*
* RFC recommends [now-5min, now+5min] lifetime interval.
*/
#define SIG0_LIFETIME_FUDGE_SECONDS 300
/*- SIG(0) internals ---------------------------------------------------------*/
/*!
* \brief Create and initialize SIG(0) RR set.
*
* \return SIG(0) RR set.
*/
static knot_rrset_t *sig0_create_rrset(void)
{
knot_dname_t *root = knot_dname_from_str(".");
uint32_t ttl = 0;
knot_rrset_t *sig_record = knot_rrset_new(root, KNOT_RRTYPE_SIG,
KNOT_CLASS_ANY, ttl);
return sig_record;
}
static void sig0_write_rdata(uint8_t *rdata, const knot_dnssec_key_t *key)
{
uint32_t incepted = time(NULL) - SIG0_LIFETIME_FUDGE_SECONDS;
uint32_t expires = incepted + 2 * SIG0_LIFETIME_FUDGE_SECONDS;
uint16_t type = 0;
uint8_t labels = 0;
uint32_t ttl = 0;
knot_rrsig_write_rdata(rdata, key, type, labels, ttl, incepted, expires);
}
/*!
* \brief Create and zero SIG(0) RDATA field.
*
* \param rrset SIG(0) RR set.
* \param key Signing key.
*
* \return SIG(0) RDATA.
*/
static uint8_t *sig0_create_rdata(knot_rrset_t *rrset, knot_dnssec_key_t *key)
{
assert(rrset);
assert(key);
size_t rdata_size = knot_rrsig_rdata_size(key);
uint8_t *rdata = knot_rrset_create_rdata(rrset, rdata_size);
if (!rdata) {
return NULL;
}
sig0_write_rdata(rdata, key);
return rdata;
}
/*!
* \brief Write SIG(0) signature to a given binary wire.
*
* The signature covers SIG(0) RDATA section without signature field. And the
* whole preceeding request before the SIG(0) record was added (i.e. before the
* AR count in header was increased).
*
* \param wire Output wire to be signed.
* \param request_size Size of the request in the wire.
* \param sig_rr_size Size of the SIG(0) RR in the wire.
* \param key Signing key.
*
* \return Error code, KNOT_EOK if successful.
*/
static int sig0_write_signature(uint8_t* wire, size_t request_size,
size_t sig_rr_size, knot_dnssec_key_t *key)
{
assert(key);
assert(key->data);
knot_dnssec_sign_context_t *ctx = knot_dnssec_sign_init(key);
if (!ctx) {
return KNOT_ENOMEM;
}
size_t signature_size = knot_dnssec_sign_size(key);
size_t sig_rr_header_size = 11; // owner (== root), type, class, TTL
size_t sig_rdata_size = sig_rr_size - sig_rr_header_size;
uint8_t *sig_rdata = wire + request_size + sig_rr_header_size;
uint8_t *signature = wire + request_size + sig_rr_size - signature_size;
knot_dnssec_sign_add(ctx, sig_rdata, sig_rdata_size - signature_size);
knot_dnssec_sign_add(ctx, wire, request_size);
int result = knot_dnssec_sign_write(ctx, signature, signature_size);
knot_dnssec_sign_free(ctx);
return result;
}
/*- SIG(0) public ------------------------------------------------------------*/
/*!
* \brief Sign a packet using SIG(0) mechanism.
*/
int knot_sig0_sign(uint8_t *wire, size_t *wire_size, size_t wire_max_size,
knot_dnssec_key_t *key)
{
knot_rrset_t *sig_rrset = sig0_create_rrset();
if (!sig_rrset) {
return KNOT_ENOMEM;
}
// SIG(0) headers without signature
uint8_t *sig_rdata = sig0_create_rdata(sig_rrset, key);
if (!sig_rdata) {
knot_rrset_deep_free(&sig_rrset, 1);
return KNOT_ENOMEM;
}
// convert to wire
uint8_t *wire_end = wire + *wire_size;
size_t wire_avail_size = wire_max_size - *wire_size;
size_t wire_sig_size = 0;
uint16_t written_rr_count = 0;
int result = knot_rrset_to_wire(sig_rrset, wire_end, &wire_sig_size,
wire_avail_size, &written_rr_count,
NULL);
knot_rrset_deep_free(&sig_rrset, 1);
if (result != KNOT_EOK) {
return result;
}
assert(written_rr_count == 1);
// create signature
result = sig0_write_signature(wire, *wire_size, wire_sig_size, key);
if (result != KNOT_EOK) {
return result;
}
uint16_t wire_arcount = knot_wire_get_arcount(wire);
knot_wire_set_arcount(wire, wire_arcount + written_rr_count);
*wire_size += wire_sig_size;
return KNOT_EOK;
}
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