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/* Copyright (C) 2018 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 <stdbool.h>
#include "libdnssec/shared/bignum.h"
#include "libdnssec/binary.h"
#include "libdnssec/error.h"
#include "libdnssec/sign/der.h"
#include "libdnssec/shared/binary_wire.h"
/*
* In fact, this is a very tiny subset of ASN.1 encoding format implementation,
* which is necessary for the purpose of DNSSEC.
*
* References: RFC 3279 (X.509 PKI), X.690, RFC 6605 (ECDSA), RFC8080 (EDDSA)
*
* Dss-Sig-Value ::= SEQUENCE { r INTEGER, s INTEGER }
*/
#define ASN1_TYPE_SEQUENCE 0x30
#define ASN1_TYPE_INTEGER 0x02
#define ASN1_MAX_SIZE 127
/*!
* Check if the next object has a given type.
*/
static bool asn1_expect_type(wire_ctx_t *wire, uint8_t type)
{
assert(wire);
return (wire_ctx_available(wire) >= 1 && wire_ctx_read_u8(wire) == type);
}
/*!
* Decode the size of the object (only short format is supported).
*/
static int asn1_decode_size(wire_ctx_t *wire, size_t *size)
{
assert(wire);
assert(size);
if (wire_ctx_available(wire) < 1) {
return DNSSEC_MALFORMED_DATA;
}
uint8_t byte = wire_ctx_read_u8(wire);
if (byte & 0x80) {
// long form, we do not need it for DNSSEC
return DNSSEC_NOT_IMPLEMENTED_ERROR;
}
*size = byte;
return DNSSEC_EOK;
}
/*!
* Decode an unsigned integer object.
*/
static int asn1_decode_integer(wire_ctx_t *wire, dnssec_binary_t *_value)
{
assert(wire);
assert(_value);
if (!asn1_expect_type(wire, ASN1_TYPE_INTEGER)) {
return DNSSEC_MALFORMED_DATA;
}
size_t size;
int result = asn1_decode_size(wire, &size);
if (result != DNSSEC_EOK) {
return result;
}
if (size == 0 || size > wire_ctx_available(wire)) {
return DNSSEC_MALFORMED_DATA;
}
dnssec_binary_t value = { .data = wire->position, .size = size };
wire->position += size;
// skip leading zeroes (unless equal to zero)
while (value.size > 1 && value.data[0] == 0) {
value.data += 1;
value.size -= 1;
}
*_value = value;
return DNSSEC_EOK;
}
/*!
* Encode object header (type and length).
*/
static void asn1_write_header(wire_ctx_t *wire, uint8_t type, size_t length)
{
assert(wire);
assert(length < ASN1_MAX_SIZE);
wire_ctx_write_u8(wire, type);
wire_ctx_write_u8(wire, length);
}
/*!
* Encode unsigned integer object.
*/
static void asn1_write_integer(wire_ctx_t *wire, size_t integer_size,
const dnssec_binary_t *integer)
{
assert(wire);
assert(integer);
assert(integer->data);
asn1_write_header(wire, ASN1_TYPE_INTEGER, integer_size);
bignum_write(wire, integer_size, integer);
}
/*!
* Decode signature parameters from X.509 ECDSA signature.
*/
int dss_sig_value_decode(const dnssec_binary_t *der,
dnssec_binary_t *r, dnssec_binary_t *s)
{
if (!der || !der->data || !r || !s) {
return DNSSEC_EINVAL;
}
wire_ctx_t wire = binary_init(der);
size_t size;
int result;
// decode the sequence
if (!asn1_expect_type(&wire, ASN1_TYPE_SEQUENCE)) {
return DNSSEC_MALFORMED_DATA;
}
result = asn1_decode_size(&wire, &size);
if (result != DNSSEC_EOK) {
return result;
}
if (size != wire_ctx_available(&wire)) {
return DNSSEC_MALFORMED_DATA;
}
// decode the 'r' and 's' values
dnssec_binary_t der_r;
result = asn1_decode_integer(&wire, &der_r);
if (result != DNSSEC_EOK) {
return result;
}
dnssec_binary_t der_s;
result = asn1_decode_integer(&wire, &der_s);
if (result != DNSSEC_EOK) {
return result;
}
if (wire_ctx_available(&wire) != 0) {
return DNSSEC_MALFORMED_DATA;
}
*r = der_r;
*s = der_s;
return DNSSEC_EOK;
}
/*!
* Encode signature parameters from X.509 ECDSA signature.
*/
int dss_sig_value_encode(const dnssec_binary_t *r, const dnssec_binary_t *s,
dnssec_binary_t *der)
{
if (!r || !r->data || !s || !s->data || !der) {
return DNSSEC_EINVAL;
}
size_t r_size = bignum_size_s(r);
size_t s_size = bignum_size_s(s);
// check supported inputs range
if (r_size > ASN1_MAX_SIZE || s_size > ASN1_MAX_SIZE) {
return DNSSEC_NOT_IMPLEMENTED_ERROR;
}
size_t seq_size = 2 + r_size + 2 + s_size;
if (seq_size > ASN1_MAX_SIZE) {
return DNSSEC_NOT_IMPLEMENTED_ERROR;
}
// encode result
size_t total_size = 2 + seq_size;
dnssec_binary_t _der = { 0 };
if (dnssec_binary_alloc(&_der, total_size)) {
return DNSSEC_ENOMEM;
}
wire_ctx_t wire = binary_init(&_der);
asn1_write_header(&wire, ASN1_TYPE_SEQUENCE, seq_size);
asn1_write_integer(&wire, r_size, r);
asn1_write_integer(&wire, s_size, s);
assert(wire_ctx_available(&wire) == 0);
*der = _der;
return DNSSEC_EOK;
}
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