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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "private/asn1_decoder.h"
int asn1_context::peek_byte() const {
if (length_ == 0) {
return -1;
}
return *p_;
}
int asn1_context::get_byte() {
if (length_ == 0) {
return -1;
}
int byte = *p_;
p_++;
length_--;
return byte;
}
bool asn1_context::skip_bytes(size_t num_skip) {
if (length_ < num_skip) {
return false;
}
p_ += num_skip;
length_ -= num_skip;
return true;
}
bool asn1_context::decode_length(size_t* out_len) {
int num_octets = get_byte();
if (num_octets == -1) {
return false;
}
if ((num_octets & 0x80) == 0x00) {
*out_len = num_octets;
return true;
}
num_octets &= kMaskTag;
if (static_cast<size_t>(num_octets) >= sizeof(size_t)) {
return false;
}
size_t length = 0;
for (int i = 0; i < num_octets; ++i) {
int byte = get_byte();
if (byte == -1) {
return false;
}
length <<= 8;
length += byte;
}
*out_len = length;
return true;
}
/**
* Returns the constructed type and advances the pointer. E.g. A0 -> 0
*/
asn1_context* asn1_context::asn1_constructed_get() {
int type = get_byte();
if (type == -1 || (type & kMaskConstructed) != kTagConstructed) {
return nullptr;
}
size_t length;
if (!decode_length(&length) || length > length_) {
return nullptr;
}
asn1_context* app_ctx = new asn1_context(p_, length);
app_ctx->app_type_ = type & kMaskAppType;
return app_ctx;
}
bool asn1_context::asn1_constructed_skip_all() {
int byte = peek_byte();
while (byte != -1 && (byte & kMaskConstructed) == kTagConstructed) {
skip_bytes(1);
size_t length;
if (!decode_length(&length) || !skip_bytes(length)) {
return false;
}
byte = peek_byte();
}
return byte != -1;
}
int asn1_context::asn1_constructed_type() const {
return app_type_;
}
asn1_context* asn1_context::asn1_sequence_get() {
if ((get_byte() & kMaskTag) != kTagSequence) {
return nullptr;
}
size_t length;
if (!decode_length(&length) || length > length_) {
return nullptr;
}
return new asn1_context(p_, length);
}
asn1_context* asn1_context::asn1_set_get() {
if ((get_byte() & kMaskTag) != kTagSet) {
return nullptr;
}
size_t length;
if (!decode_length(&length) || length > length_) {
return nullptr;
}
return new asn1_context(p_, length);
}
bool asn1_context::asn1_sequence_next() {
size_t length;
if (get_byte() == -1 || !decode_length(&length) || !skip_bytes(length)) {
return false;
}
return true;
}
bool asn1_context::asn1_oid_get(const uint8_t** oid, size_t* length) {
if (get_byte() != kTagOid) {
return false;
}
if (!decode_length(length) || *length == 0 || *length > length_) {
return false;
}
*oid = p_;
return true;
}
bool asn1_context::asn1_octet_string_get(const uint8_t** octet_string, size_t* length) {
if (get_byte() != kTagOctetString) {
return false;
}
if (!decode_length(length) || *length == 0 || *length > length_) {
return false;
}
*octet_string = p_;
return true;
}
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