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/*
* QEMU Crypto ASN.1 DER decoder
*
* Copyright (c) 2022 Bytedance
* Author: lei he <helei.sig11@bytedance.com>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "crypto/der.h"
enum QCryptoDERTypeTag {
QCRYPTO_DER_TYPE_TAG_BOOL = 0x1,
QCRYPTO_DER_TYPE_TAG_INT = 0x2,
QCRYPTO_DER_TYPE_TAG_BIT_STR = 0x3,
QCRYPTO_DER_TYPE_TAG_OCT_STR = 0x4,
QCRYPTO_DER_TYPE_TAG_OCT_NULL = 0x5,
QCRYPTO_DER_TYPE_TAG_OCT_OID = 0x6,
QCRYPTO_DER_TYPE_TAG_SEQ = 0x10,
QCRYPTO_DER_TYPE_TAG_SET = 0x11,
};
#define QCRYPTO_DER_CONSTRUCTED_MASK 0x20
#define QCRYPTO_DER_SHORT_LEN_MASK 0x80
static uint8_t qcrypto_der_peek_byte(const uint8_t **data, size_t *dlen)
{
return **data;
}
static void qcrypto_der_cut_nbytes(const uint8_t **data,
size_t *dlen,
size_t nbytes)
{
*data += nbytes;
*dlen -= nbytes;
}
static uint8_t qcrypto_der_cut_byte(const uint8_t **data, size_t *dlen)
{
uint8_t val = qcrypto_der_peek_byte(data, dlen);
qcrypto_der_cut_nbytes(data, dlen, 1);
return val;
}
static int qcrypto_der_invoke_callback(QCryptoDERDecodeCb cb, void *ctx,
const uint8_t *value, size_t vlen,
Error **errp)
{
if (!cb) {
return 0;
}
return cb(ctx, value, vlen, errp);
}
static int qcrypto_der_extract_definite_data(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx,
Error **errp)
{
const uint8_t *value;
size_t vlen = 0;
uint8_t byte_count = qcrypto_der_cut_byte(data, dlen);
/* short format of definite-length */
if (!(byte_count & QCRYPTO_DER_SHORT_LEN_MASK)) {
if (byte_count > *dlen) {
error_setg(errp, "Invalid content length: %u", byte_count);
return -1;
}
value = *data;
vlen = byte_count;
qcrypto_der_cut_nbytes(data, dlen, vlen);
if (qcrypto_der_invoke_callback(cb, ctx, value, vlen, errp) != 0) {
return -1;
}
return vlen;
}
/* Ignore highest bit */
byte_count &= ~QCRYPTO_DER_SHORT_LEN_MASK;
/*
* size_t is enough to store the value of length, although the DER
* encoding standard supports larger length.
*/
if (byte_count > sizeof(size_t)) {
error_setg(errp, "Invalid byte count of content length: %u",
byte_count);
return -1;
}
if (byte_count > *dlen) {
error_setg(errp, "Invalid content length: %u", byte_count);
return -1;
}
while (byte_count--) {
vlen <<= 8;
vlen += qcrypto_der_cut_byte(data, dlen);
}
if (vlen > *dlen) {
error_setg(errp, "Invalid content length: %zu", vlen);
return -1;
}
value = *data;
qcrypto_der_cut_nbytes(data, dlen, vlen);
if (qcrypto_der_invoke_callback(cb, ctx, value, vlen, errp) != 0) {
return -1;
}
return vlen;
}
static int qcrypto_der_extract_data(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx,
Error **errp)
{
uint8_t val;
if (*dlen < 1) {
error_setg(errp, "Need more data");
return -1;
}
val = qcrypto_der_peek_byte(data, dlen);
/* must use definite length format */
if (val == QCRYPTO_DER_SHORT_LEN_MASK) {
error_setg(errp, "Only definite length format is allowed");
return -1;
}
return qcrypto_der_extract_definite_data(data, dlen, cb, ctx, errp);
}
int qcrypto_der_decode_int(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag;
if (*dlen < 1) {
error_setg(errp, "Need more data");
return -1;
}
tag = qcrypto_der_cut_byte(data, dlen);
/* INTEGER must encoded in primitive-form */
if (tag != QCRYPTO_DER_TYPE_TAG_INT) {
error_setg(errp, "Invalid integer type tag: %u", tag);
return -1;
}
return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
}
int qcrypto_der_decode_seq(const uint8_t **data, size_t *dlen,
QCryptoDERDecodeCb cb, void *ctx, Error **errp)
{
uint8_t tag;
if (*dlen < 1) {
error_setg(errp, "Need more data");
return -1;
}
tag = qcrypto_der_cut_byte(data, dlen);
/* SEQUENCE must use constructed form */
if (tag != (QCRYPTO_DER_TYPE_TAG_SEQ | QCRYPTO_DER_CONSTRUCTED_MASK)) {
error_setg(errp, "Invalid type sequence tag: %u", tag);
return -1;
}
return qcrypto_der_extract_data(data, dlen, cb, ctx, errp);
}
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