/**************************************************************************/
/*  aes_context.cpp                                                       */
/**************************************************************************/
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/*                             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 "aes_context.h"

#include "core/object/class_db.h"

using AESMode = CryptoCore::AESContext::Mode;
using AESCipher = CryptoCore::AESContext::Cipher;

Error AESContext::start(Mode p_mode, const PackedByteArray &p_key, const PackedByteArray &p_iv) {
	ERR_FAIL_COND_V_MSG(mode != MODE_MAX, ERR_ALREADY_IN_USE, "AESContext already started. Call 'finish' before starting a new one.");
	ERR_FAIL_COND_V_MSG(p_mode < 0 || p_mode >= MODE_MAX, ERR_INVALID_PARAMETER, "Invalid mode requested.");
	// Key check.
	int key_bits = p_key.size() << 3;
	ERR_FAIL_COND_V_MSG(key_bits != 128 && key_bits != 256, ERR_INVALID_PARAMETER, "AES key must be either 16 or 32 bytes");

	AESMode ctx_mode = AESMode::NONE;
	AESCipher ctx_cipher = AESCipher::NONE;
	switch (p_mode) {
		case MODE_ECB_ENCRYPT:
			ctx_mode = AESMode::ENCRYPT;
			ctx_cipher = AESCipher::ECB;
			break;
		case MODE_ECB_DECRYPT:
			ctx_mode = AESMode::DECRYPT;
			ctx_cipher = AESCipher::ECB;
			break;
		case MODE_CBC_ENCRYPT:
			ctx_mode = AESMode::ENCRYPT;
			ctx_cipher = AESCipher::CBC;
			break;
		case MODE_CBC_DECRYPT:
			ctx_mode = AESMode::DECRYPT;
			ctx_cipher = AESCipher::CBC;
			break;
		default:
			ERR_FAIL_V(ERR_INVALID_PARAMETER);
	}

	// Initialization vector.
	PackedByteArray iv = p_iv;
	ERR_FAIL_COND_V_MSG(ctx_cipher == AESCipher::CBC && iv.size() != 16, ERR_INVALID_PARAMETER, "The initialization vector (IV) must be exactly 16 bytes.");
	if (unlikely(ctx_cipher == AESCipher::ECB && iv.size())) {
		WARN_PRINT("ECB mode does not require an initialization vector (IV). Pass an empty IV argument when using ECB.");
		iv.clear();
	}
	Error err = ctx.setup(ctx_mode, ctx_cipher, p_key.ptr(), p_key.size(), iv.size() ? iv.ptr() : nullptr, iv.size());
	if (err != OK) {
		return err;
	}
	mode = p_mode;
	return OK;
}

PackedByteArray AESContext::update(const PackedByteArray &p_src) {
	ERR_FAIL_COND_V_MSG(mode < 0 || mode >= MODE_MAX, PackedByteArray(), "AESContext not started. Call 'start' before calling 'update'.");
	int len = p_src.size();
	ERR_FAIL_COND_V_MSG(len % 16, PackedByteArray(), "The number of bytes to be encrypted must be multiple of 16. Add padding if needed");
	PackedByteArray out;
	out.resize(len);
	Error err = ctx.update(p_src.ptr(), len, out.ptrw(), len);
	ERR_FAIL_COND_V(err != OK, PackedByteArray());
	return out;
}

PackedByteArray AESContext::get_iv_state() {
	ERR_FAIL_V_MSG(PackedByteArray(), "Calling 'get_iv_state' is no longer supported.");
}

void AESContext::finish() {
	ctx.finish(nullptr, 0);
	mode = MODE_MAX;
}

void AESContext::_bind_methods() {
	ClassDB::bind_method(D_METHOD("start", "mode", "key", "iv"), &AESContext::start, DEFVAL(PackedByteArray()));
	ClassDB::bind_method(D_METHOD("update", "src"), &AESContext::update);
	ClassDB::bind_method(D_METHOD("get_iv_state"), &AESContext::get_iv_state);
	ClassDB::bind_method(D_METHOD("finish"), &AESContext::finish);
	BIND_ENUM_CONSTANT(MODE_ECB_ENCRYPT);
	BIND_ENUM_CONSTANT(MODE_ECB_DECRYPT);
	BIND_ENUM_CONSTANT(MODE_CBC_ENCRYPT);
	BIND_ENUM_CONSTANT(MODE_CBC_DECRYPT);
	BIND_ENUM_CONSTANT(MODE_MAX);
}