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/* Copyright (C) 2020 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 <https://www.gnu.org/licenses/>.
*/
#include "libdnssec/binary.h"
#include "libdnssec/error.h"
#include "libdnssec/key.h"
#include "libdnssec/key/internal.h"
#include "libdnssec/shared/dname.h"
#include "libdnssec/shared/shared.h"
#include "libdnssec/shared/binary_wire.h"
#include <gnutls/gnutls.h>
#include <gnutls/crypto.h>
/*!
* Convert DNSSEC DS digest algorithm to GnuTLS digest algorithm.
*/
static gnutls_digest_algorithm_t lookup_algorithm(dnssec_key_digest_t algorithm)
{
switch (algorithm) {
case DNSSEC_KEY_DIGEST_SHA1: return GNUTLS_DIG_SHA1;
case DNSSEC_KEY_DIGEST_SHA256: return GNUTLS_DIG_SHA256;
case DNSSEC_KEY_DIGEST_SHA384: return GNUTLS_DIG_SHA384;
default:
return GNUTLS_DIG_UNKNOWN;
};
}
_public_
bool dnssec_algorithm_digest_support(dnssec_key_digest_t algorithm)
{
/* GnuTLS docs:
* > It is not possible to query for insecure hash algorithms directly
* > (only indirectly through the signature API).
* So let's query combining the hash with RSA.
*/
gnutls_sign_algorithm_t rsa;
switch (algorithm) {
case DNSSEC_KEY_DIGEST_SHA1: rsa = GNUTLS_SIGN_RSA_SHA1; break;
case DNSSEC_KEY_DIGEST_SHA256: rsa = GNUTLS_SIGN_RSA_SHA256; break;
case DNSSEC_KEY_DIGEST_SHA384: rsa = GNUTLS_SIGN_RSA_SHA384; break;
default:
return false;
};
return gnutls_sign_is_secure(rsa);
}
static void wire_write_digest(wire_ctx_t *wire,
gnutls_hash_hd_t digest, int digest_size)
{
assert(wire_ctx_available(wire) >= digest_size);
gnutls_hash_output(digest, wire->position);
wire->position += digest_size;
}
_public_
int dnssec_key_create_ds(const dnssec_key_t *key,
dnssec_key_digest_t ds_algorithm,
dnssec_binary_t *rdata_ptr)
{
if (!key || !rdata_ptr) {
return DNSSEC_EINVAL;
}
if (!key->dname) {
return DNSSEC_INVALID_KEY_NAME;
}
if (!key->public_key){
return DNSSEC_INVALID_PUBLIC_KEY;
}
gnutls_digest_algorithm_t algorithm = lookup_algorithm(ds_algorithm);
if (algorithm == GNUTLS_DIG_UNKNOWN) {
return DNSSEC_INVALID_DS_ALGORITHM;
}
// compute DS hash
_cleanup_hash_ gnutls_hash_hd_t digest = NULL;
int r = gnutls_hash_init(&digest, algorithm);
if (r < 0) {
return DNSSEC_DS_HASHING_ERROR;
}
if (gnutls_hash(digest, key->dname, dname_length(key->dname)) != 0 ||
gnutls_hash(digest, key->rdata.data, key->rdata.size) != 0
) {
return DNSSEC_DS_HASHING_ERROR;
}
// build DS RDATA
int digest_size = gnutls_hash_get_len(algorithm);
if (digest_size == 0) {
return DNSSEC_DS_HASHING_ERROR;
}
dnssec_binary_t rdata = { 0 };
r = dnssec_binary_alloc(&rdata, 4 + digest_size);
if (r != DNSSEC_EOK) {
return r;
}
wire_ctx_t wire = binary_init(&rdata);
wire_ctx_write_u16(&wire, dnssec_key_get_keytag(key));
wire_ctx_write_u8(&wire, dnssec_key_get_algorithm(key));
wire_ctx_write_u8(&wire, ds_algorithm);
wire_write_digest(&wire, digest, digest_size);
assert(wire_ctx_offset(&wire) == wire.size);
*rdata_ptr = rdata;
return DNSSEC_EOK;
}
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