file_access_encrypted.cpp

/**************************************************************************/
/*  file_access_encrypted.cpp                                             */
/**************************************************************************/
/*                         This file is part of:                          */
/*                             GODOT ENGINE                               */
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/* Copyright (c) 2014-present Godot Engine contributors (see AUTHORS.md). */
/* Copyright (c) 2007-2014 Juan Linietsky, Ariel Manzur.                  */
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#include "file_access_encrypted.h"

#include "core/variant/variant.h"

CryptoCore::RandomGenerator *FileAccessEncrypted::_fae_static_rng = nullptr;

void FileAccessEncrypted::deinitialize() {
	if (_fae_static_rng) {
		memdelete(_fae_static_rng);
		_fae_static_rng = nullptr;
	}
}

Error FileAccessEncrypted::open_and_parse(Ref<FileAccess> p_base, const Vector<uint8_t> &p_key, Mode p_mode, bool p_with_magic, const Vector<uint8_t> &p_iv) {
	ERR_FAIL_COND_V_MSG(file.is_valid(), ERR_ALREADY_IN_USE, vformat("Can't open file while another file from path '%s' is open.", file->get_path_absolute()));
	ERR_FAIL_COND_V(p_key.size() != 32, ERR_INVALID_PARAMETER);

	pos = 0;
	eofed = false;
	use_magic = p_with_magic;

	if (p_mode == MODE_WRITE_AES256) {
		data.clear();
		writing = true;
		file = p_base;
		key = p_key;
		if (p_iv.is_empty()) {
			iv.resize(16);
			if (unlikely(!_fae_static_rng)) {
				_fae_static_rng = memnew(CryptoCore::RandomGenerator);
				if (_fae_static_rng->init() != OK) {
					memdelete(_fae_static_rng);
					_fae_static_rng = nullptr;
					ERR_FAIL_V_MSG(FAILED, "Failed to initialize random number generator.");
				}
			}
			Error err = _fae_static_rng->get_random_bytes(iv.ptrw(), 16);
			ERR_FAIL_COND_V(err != OK, err);
		} else {
			ERR_FAIL_COND_V(p_iv.size() != 16, ERR_INVALID_PARAMETER);
			iv = p_iv;
		}

	} else if (p_mode == MODE_READ) {
		writing = false;
		key = p_key;

		if (use_magic) {
			uint32_t magic = p_base->get_32();
			ERR_FAIL_COND_V(magic != ENCRYPTED_HEADER_MAGIC, ERR_FILE_UNRECOGNIZED);
		}

		unsigned char md5d[16];
		p_base->get_buffer(md5d, 16);
		length = p_base->get_64();

		iv.resize(16);
		p_base->get_buffer(iv.ptrw(), 16);

		base = p_base->get_position();
		ERR_FAIL_COND_V(p_base->get_length() < base + length, ERR_FILE_CORRUPT);
		uint64_t ds = length;
		if (ds % 16) {
			ds += 16 - (ds % 16);
		}
		data.resize(ds);

		uint64_t blen = p_base->get_buffer(data.ptrw(), ds);
		ERR_FAIL_COND_V(blen != ds, ERR_FILE_CORRUPT);

		{
			CryptoCore::AESContext ctx;

			ctx.set_encode_key(key.ptrw(), 256); // Due to the nature of CFB, same key schedule is used for both encryption and decryption!
			ctx.decrypt_cfb(ds, iv.ptrw(), data.ptrw(), data.ptrw());
		}

		data.resize(length);

		unsigned char hash[16];
		ERR_FAIL_COND_V(CryptoCore::md5(data.ptr(), data.size(), hash) != OK, ERR_BUG);

		ERR_FAIL_COND_V_MSG(String::md5(hash) != String::md5(md5d), ERR_FILE_CORRUPT, "The MD5 sum of the decrypted file does not match the expected value. It could be that the file is corrupt, or that the provided decryption key is invalid.");

		file = p_base;
	}

	return OK;
}

Error FileAccessEncrypted::open_and_parse_password(Ref<FileAccess> p_base, const String &p_key, Mode p_mode) {
	String cs = p_key.md5_text();
	ERR_FAIL_COND_V(cs.length() != 32, ERR_INVALID_PARAMETER);
	Vector<uint8_t> key_md5;
	key_md5.resize(32);
	for (int i = 0; i < 32; i++) {
		key_md5.write[i] = cs[i];
	}

	return open_and_parse(p_base, key_md5, p_mode);
}

Error FileAccessEncrypted::open_internal(const String &p_path, int p_mode_flags) {
	return OK;
}

void FileAccessEncrypted::_close() {
	if (file.is_null()) {
		return;
	}

	if (writing) {
		Vector<uint8_t> compressed;
		uint64_t len = data.size();
		if (len % 16) {
			len += 16 - (len % 16);
		}

		unsigned char hash[16];
		ERR_FAIL_COND(CryptoCore::md5(data.ptr(), data.size(), hash) != OK); // Bug?

		compressed.resize(len);
		memset(compressed.ptrw(), 0, len);
		for (int i = 0; i < data.size(); i++) {
			compressed.write[i] = data[i];
		}

		CryptoCore::AESContext ctx;
		ctx.set_encode_key(key.ptrw(), 256);

		if (use_magic) {
			file->store_32(ENCRYPTED_HEADER_MAGIC);
		}

		file->store_buffer(hash, 16);
		file->store_64(data.size());
		file->store_buffer(iv.ptr(), 16);

		ctx.encrypt_cfb(len, iv.ptrw(), compressed.ptrw(), compressed.ptrw());

		file->store_buffer(compressed.ptr(), compressed.size());
		data.clear();
	}

	file.unref();
}

bool FileAccessEncrypted::is_open() const {
	return file.is_valid();
}

String FileAccessEncrypted::get_path() const {
	if (file.is_valid()) {
		return file->get_path();
	} else {
		return "";
	}
}

String FileAccessEncrypted::get_path_absolute() const {
	if (file.is_valid()) {
		return file->get_path_absolute();
	} else {
		return "";
	}
}

void FileAccessEncrypted::seek(uint64_t p_position) {
	if (p_position > get_length()) {
		p_position = get_length();
	}

	pos = p_position;
	eofed = false;
}

void FileAccessEncrypted::seek_end(int64_t p_position) {
	seek(get_length() + p_position);
}

uint64_t FileAccessEncrypted::get_position() const {
	return pos;
}

uint64_t FileAccessEncrypted::get_length() const {
	return data.size();
}

bool FileAccessEncrypted::eof_reached() const {
	return eofed;
}

uint64_t FileAccessEncrypted::get_buffer(uint8_t *p_dst, uint64_t p_length) const {
	ERR_FAIL_COND_V_MSG(writing, -1, "File has not been opened in read mode.");

	if (!p_length) {
		return 0;
	}

	ERR_FAIL_NULL_V(p_dst, -1);

	uint64_t to_copy = MIN(p_length, get_length() - pos);

	memcpy(p_dst, data.ptr() + pos, to_copy);
	pos += to_copy;

	if (to_copy < p_length) {
		eofed = true;
	}

	return to_copy;
}

Error FileAccessEncrypted::get_error() const {
	return eofed ? ERR_FILE_EOF : OK;
}

bool FileAccessEncrypted::store_buffer(const uint8_t *p_src, uint64_t p_length) {
	ERR_FAIL_COND_V_MSG(!writing, false, "File has not been opened in write mode.");

	if (!p_length) {
		return true;
	}

	ERR_FAIL_NULL_V(p_src, false);

	if (pos + p_length >= get_length()) {
		ERR_FAIL_COND_V(data.resize(pos + p_length) != OK, false);
	}

	memcpy(data.ptrw() + pos, p_src, p_length);
	pos += p_length;

	return true;
}

void FileAccessEncrypted::flush() {
	ERR_FAIL_COND_MSG(!writing, "File has not been opened in write mode.");

	// encrypted files keep data in memory till close()
}

bool FileAccessEncrypted::file_exists(const String &p_name) {
	Ref<FileAccess> fa = FileAccess::open(p_name, FileAccess::READ);
	if (fa.is_null()) {
		return false;
	}
	return true;
}

uint64_t FileAccessEncrypted::_get_modified_time(const String &p_file) {
	if (file.is_valid()) {
		return file->get_modified_time(p_file);
	} else {
		return 0;
	}
}

uint64_t FileAccessEncrypted::_get_access_time(const String &p_file) {
	if (file.is_valid()) {
		return file->get_access_time(p_file);
	} else {
		return 0;
	}
}

int64_t FileAccessEncrypted::_get_size(const String &p_file) {
	if (file.is_valid()) {
		return file->get_size(p_file);
	} else {
		return -1;
	}
}

BitField<FileAccess::UnixPermissionFlags> FileAccessEncrypted::_get_unix_permissions(const String &p_file) {
	if (file.is_valid()) {
		return file->_get_unix_permissions(p_file);
	}
	return 0;
}

Error FileAccessEncrypted::_set_unix_permissions(const String &p_file, BitField<FileAccess::UnixPermissionFlags> p_permissions) {
	if (file.is_valid()) {
		return file->_set_unix_permissions(p_file, p_permissions);
	}
	return FAILED;
}

bool FileAccessEncrypted::_get_hidden_attribute(const String &p_file) {
	if (file.is_valid()) {
		return file->_get_hidden_attribute(p_file);
	}
	return false;
}

Error FileAccessEncrypted::_set_hidden_attribute(const String &p_file, bool p_hidden) {
	if (file.is_valid()) {
		return file->_set_hidden_attribute(p_file, p_hidden);
	}
	return FAILED;
}

bool FileAccessEncrypted::_get_read_only_attribute(const String &p_file) {
	if (file.is_valid()) {
		return file->_get_read_only_attribute(p_file);
	}
	return false;
}

Error FileAccessEncrypted::_set_read_only_attribute(const String &p_file, bool p_ro) {
	if (file.is_valid()) {
		return file->_set_read_only_attribute(p_file, p_ro);
	}
	return FAILED;
}

void FileAccessEncrypted::close() {
	_close();
}

FileAccessEncrypted::~FileAccessEncrypted() {
	_close();
}