// SPDX-License-Identifier: BSD-2-Clause
/*
  Copyright (c) 2012-2016, Matthias Schiffer <mschiffer@universe-factory.net>
  All rights reserved.
*/

/**
   \file

   cipher-test method provider (testing and benchmarking only)

   The cipher-test method provider performs encryption only and can be used to test
   and benchmark cipher implementations.
*/


#include "../../crypto.h"
#include "../../method.h"
#include "../common.h"


/** A specific method provided by this provider */
struct fastd_method {
	const fastd_cipher_info_t *cipher_info; /**< The cipher used */
};

/** The method-specific session state */
struct fastd_method_session_state {
	fastd_method_common_t common; /**< The common method state */

	const fastd_method_t *method;       /**< The specific method used */
	const fastd_cipher_t *cipher;       /**< The cipher implementation used */
	fastd_cipher_state_t *cipher_state; /**< The cipher state */
};


/** Instanciates a method using a name of the pattern "<cipher>+cipher-test" */
static bool method_create_by_name(const char *name, fastd_method_t **method) {
	fastd_method_t m;

	size_t len = strlen(name);
	if (len < 12)
		return false;

	if (strcmp(name + len - 12, "+cipher-test"))
		return false;

	char cipher_name[len - 11];
	memcpy(cipher_name, name, len - 12);
	cipher_name[len - 12] = 0;

	m.cipher_info = fastd_cipher_info_get_by_name(cipher_name);
	if (!m.cipher_info)
		return false;

	*method = fastd_new(fastd_method_t);
	**method = m;

	return true;
}

/** Frees a method */
static void method_destroy(fastd_method_t *method) {
	free(method);
}

/** Returns the key length used by a method */
static size_t method_key_length(const fastd_method_t *method) {
	return method->cipher_info->key_length;
}

/** Initializes a session */
static fastd_method_session_state_t *
method_session_init(const fastd_method_t *method, const uint8_t *secret, bool initiator) {
	fastd_method_session_state_t *session = fastd_new(fastd_method_session_state_t);

	fastd_method_common_init(&session->common, initiator);
	session->method = method;
	session->cipher = fastd_cipher_get(method->cipher_info);
	session->cipher_state = session->cipher->init(secret);

	pr_warn("using cipher-test method; this method must be used for testing and benchmarks only");

	return session;
}

/** Checks if the session is currently valid */
static bool method_session_is_valid(fastd_method_session_state_t *session) {
	return (session && fastd_method_session_common_is_valid(&session->common));
}

/** Checks if this side is the initator of the session */
static bool method_session_is_initiator(fastd_method_session_state_t *session) {
	return fastd_method_session_common_is_initiator(&session->common);
}

/** Checks if the session should be refreshed */
static bool method_session_want_refresh(fastd_method_session_state_t *session) {
	return fastd_method_session_common_want_refresh(&session->common);
}

/** Marks the session as superseded */
static void method_session_superseded(fastd_method_session_state_t *session) {
	fastd_method_session_common_superseded(&session->common);
}

/** Frees the session state */
static void method_session_free(fastd_method_session_state_t *session) {
	if (session) {
		session->cipher->free(session->cipher_state);
		free(session);
	}
}


/** Encrypts a packet and adds the common method header */
static bool method_encrypt(
	UNUSED fastd_peer_t *peer, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in) {
	size_t tail_len = alignto(in.len, sizeof(fastd_block128_t)) - in.len;
	*out = fastd_buffer_alloc(in.len, alignto(COMMON_HEADBYTES, 16), sizeof(fastd_block128_t) + tail_len);

	if (tail_len)
		memset(in.data + in.len, 0, tail_len);

	uint8_t nonce[session->method->cipher_info->iv_length ?: 1] __attribute__((aligned(8)));
	fastd_method_expand_nonce(nonce, session->common.send_nonce, sizeof(nonce));

	int n_blocks = block_count(in.len, sizeof(fastd_block128_t));

	fastd_block128_t *inblocks = in.data;
	fastd_block128_t *outblocks = out->data;

	bool ok = session->cipher->crypt(
		session->cipher_state, outblocks, inblocks, n_blocks * sizeof(fastd_block128_t), nonce);

	if (!ok) {
		fastd_buffer_free(*out);
		return false;
	}

	fastd_buffer_free(in);

	fastd_method_put_common_header(out, session->common.send_nonce, 0);
	fastd_method_increment_nonce(&session->common);

	return true;
}

/** Decrypts a packet */
static bool method_decrypt(
	fastd_peer_t *peer, fastd_method_session_state_t *session, fastd_buffer_t *out, fastd_buffer_t in,
	bool *reordered) {
	if (in.len < COMMON_HEADBYTES)
		return false;

	if (!method_session_is_valid(session))
		return false;

	uint8_t in_nonce[COMMON_NONCEBYTES];
	uint8_t flags;
	int64_t age;
	if (!fastd_method_handle_common_header(&session->common, &in, in_nonce, &flags, &age))
		return false;

	if (flags)
		return false;

	uint8_t nonce[session->method->cipher_info->iv_length ?: 1] __attribute__((aligned(8)));
	fastd_method_expand_nonce(nonce, in_nonce, sizeof(nonce));

	size_t tail_len = alignto(in.len, sizeof(fastd_block128_t)) - in.len;
	*out = fastd_buffer_alloc(in.len, 0, tail_len);

	int n_blocks = block_count(in.len, sizeof(fastd_block128_t));

	fastd_block128_t *inblocks = in.data;
	fastd_block128_t *outblocks = out->data;

	bool ok = session->cipher->crypt(
		session->cipher_state, outblocks, inblocks, n_blocks * sizeof(fastd_block128_t), nonce);

	if (!ok) {
		fastd_buffer_free(*out);
		return false;
	}

	fastd_tristate_t reorder_check = fastd_method_reorder_check(peer, &session->common, in_nonce, age);
	if (reorder_check.set) {
		*reordered = reorder_check.state;
	} else {
		fastd_buffer_free(*out);
		*out = fastd_buffer_alloc(0, 0, 0);
	}

	fastd_buffer_free(in);

	return true;
}


/** The cipher-test method provider */
const fastd_method_provider_t fastd_method_cipher_test = {
	.max_overhead = COMMON_HEADBYTES,
	.min_encrypt_head_space = 0,
	.min_decrypt_head_space = 0,
	.min_encrypt_tail_space = sizeof(fastd_block128_t) - 1,
	.min_decrypt_tail_space = sizeof(fastd_block128_t) - 1,

	.create_by_name = method_create_by_name,
	.destroy = method_destroy,

	.key_length = method_key_length,

	.session_init = method_session_init,
	.session_is_valid = method_session_is_valid,
	.session_is_initiator = method_session_is_initiator,
	.session_want_refresh = method_session_want_refresh,
	.session_superseded = method_session_superseded,
	.session_free = method_session_free,

	.encrypt = method_encrypt,
	.decrypt = method_decrypt,
};
