99 lines
2.4 KiB
C++
99 lines
2.4 KiB
C++
/*
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* Copyright 2015, Mozilla Foundation and contributors
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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 "ClearKeyBase64.h"
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#include <algorithm>
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using namespace std;
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/**
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* Take a base64-encoded string, convert (in-place) each character to its
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* corresponding value in the [0x00, 0x3f] range, and truncate any padding.
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*/
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static bool
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Decode6Bit(string& aStr)
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{
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for (size_t i = 0; i < aStr.length(); i++) {
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if (aStr[i] >= 'A' && aStr[i] <= 'Z') {
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aStr[i] -= 'A';
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}
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else if (aStr[i] >= 'a' && aStr[i] <= 'z') {
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aStr[i] -= 'a' - 26;
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}
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else if (aStr[i] >= '0' && aStr[i] <= '9') {
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aStr[i] -= '0' - 52;
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}
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else if (aStr[i] == '-' || aStr[i] == '+') {
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aStr[i] = 62;
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}
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else if (aStr[i] == '_' || aStr[i] == '/') {
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aStr[i] = 63;
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}
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else {
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// Truncate '=' padding at the end of the aString.
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if (aStr[i] != '=') {
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aStr.erase(i, string::npos);
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return false;
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}
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aStr[i] = '\0';
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aStr.resize(i);
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break;
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}
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}
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return true;
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}
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bool
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DecodeBase64(const string& aEncoded, vector<uint8_t>& aOutDecoded)
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{
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if (aEncoded.empty()) {
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aOutDecoded.clear();
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return true;
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}
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if (aEncoded.size() == 1) {
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// Invalid Base64 encoding.
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return false;
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}
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string encoded = aEncoded;
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if (!Decode6Bit(encoded)) {
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return false;
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}
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// The number of bytes we haven't yet filled in the current byte, mod 8.
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int shift = 0;
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aOutDecoded.resize((encoded.size() * 3) / 4);
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vector<uint8_t>::iterator out = aOutDecoded.begin();
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for (size_t i = 0; i < encoded.length(); i++) {
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if (!shift) {
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*out = encoded[i] << 2;
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}
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else {
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*out |= encoded[i] >> (6 - shift);
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out++;
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if (out == aOutDecoded.end()) {
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// Hit last 6bit octed in encoded, which is padding and can be ignored.
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break;
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}
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*out = encoded[i] << (shift + 2);
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}
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shift = (shift + 2) % 8;
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}
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return true;
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} |