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