Initial commit

src/core/decryptor.cpp

@@ -0,0 +1,91 @@
+// Copyright 2019 threeSD Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <array>
+#include <vector>
+#include <cryptopp/aes.h>
+#include <cryptopp/files.h>
+#include <cryptopp/filters.h>
+#include <cryptopp/modes.h>
+#include <cryptopp/sha.h>
+#include "common/assert.h"
+#include "common/file_util.h"
+#include "common/string_util.h"
+#include "core/decryptor.h"
+#include "core/key/key.h"
+
+SDMCDecryptor::SDMCDecryptor(const std::string& root_folder_) : root_folder(root_folder_) {
+    ASSERT_MSG(Key::IsNormalKeyAvailable(Key::SDKey),
+               "SD Key must be available in order to decrypt");
+
+    if (root_folder.back() == '/' || root_folder.back() == '\\') {
+        // Remove '/' or '\' character at the end as we will add them back when combining path
+        root_folder.erase(root_folder.size() - 1);
+    }
+}
+
+SDMCDecryptor::~SDMCDecryptor() = default;
+
+namespace {
+std::array<u8, 16> GetFileCTR(const std::string& path) {
+    auto path_utf16 = Common::UTF8ToUTF16(path);
+    std::vector<u8> path_data(path_utf16.size() * 2 + 2, 0); // Add the '\0' character
+    std::memcpy(path_data.data(), path_utf16.data(), path_utf16.size() * 2);
+
+    CryptoPP::SHA256 sha;
+    std::array<u8, CryptoPP::SHA256::DIGESTSIZE> hash;
+    sha.CalculateDigest(hash.data(), path_data.data(), path_data.size());
+
+    std::array<u8, 16> ctr;
+    for (int i = 0; i < 16; i++) {
+        ctr[i] = hash[i] ^ hash[16 + i];
+    }
+    return ctr;
+}
+} // namespace
+
+bool SDMCDecryptor::DecryptAndWriteFile(const std::string& source,
+                                        const std::string& destination) const {
+    auto ctr = GetFileCTR(source);
+    auto key = Key::GetNormalKey(Key::SDKey);
+    CryptoPP::CTR_Mode<CryptoPP::AES>::Decryption aes;
+    aes.SetKeyWithIV(key.data(), key.size(), ctr.data());
+
+    std::string absolute_source = root_folder + source;
+    try {
+        CryptoPP::FileSource(absolute_source.c_str(), true,
+                             new CryptoPP::StreamTransformationFilter(
+                                 aes, new CryptoPP::FileSink(destination.c_str(), true)),
+                             true);
+    } catch (CryptoPP::Exception& e) {
+        LOG_ERROR(Frontend, "Error decrypting and writing file: {}", e.what());
+        return false;
+    }
+    return true;
+}
+
+std::vector<u8> SDMCDecryptor::DecryptFile(const std::string& source) const {
+    auto ctr = GetFileCTR(source);
+    auto key = Key::GetNormalKey(Key::SDKey);
+    CryptoPP::CTR_Mode<CryptoPP::AES>::Decryption aes;
+    aes.SetKeyWithIV(key.data(), key.size(), ctr.data());
+
+    FileUtil::IOFile file(root_folder + source, "rb");
+    if (!file) {
+        LOG_ERROR(Frontend, "Could not open {}", root_folder + source);
+        return {};
+    }
+
+    auto size = file.GetSize();
+
+    std::vector<u8> encrypted_data(size);
+    if (file.ReadBytes(encrypted_data.data(), size) != size) {
+        LOG_ERROR(Frontend, "Could not read file {}", root_folder + source);
+        return {};
+    }
+
+    std::vector<u8> data(size);
+    aes.ProcessData(data.data(), encrypted_data.data(), encrypted_data.size());
+    return data;
+}