src/crypto/aes-eax.c

/*
 * AES-128 EAX
 *
 * Copyright (c) 2003-2007, Jouni Malinen <j@w1.fi>
 *
 * This software may be distributed under the terms of the BSD license.
 * See README for more details.
 */

#include "includes.h"

#include "common.h"
#include "aes.h"
#include "aes_wrap.h"

/**
 * aes_128_eax_encrypt - AES-128 EAX mode encryption
 * @key: Key for encryption (16 bytes)
 * @nonce: Nonce for counter mode
 * @nonce_len: Nonce length in bytes
 * @hdr: Header data to be authenticity protected
 * @hdr_len: Length of the header data bytes
 * @data: Data to encrypt in-place
 * @data_len: Length of data in bytes
 * @tag: 16-byte tag value
 * Returns: 0 on success, -1 on failure
 */
int aes_128_eax_encrypt(const u8 *key, const u8 *nonce, size_t nonce_len,
			const u8 *hdr, size_t hdr_len,
			u8 *data, size_t data_len, u8 *tag)
{
	u8 *buf;
	size_t buf_len;
	u8 nonce_mac[AES_BLOCK_SIZE], hdr_mac[AES_BLOCK_SIZE],
		data_mac[AES_BLOCK_SIZE];
	int i, ret = -1;

	if (nonce_len > data_len)
		buf_len = nonce_len;
	else
		buf_len = data_len;
	if (hdr_len > buf_len)
		buf_len = hdr_len;
	buf_len += 16;

	buf = os_malloc(buf_len);
	if (buf == NULL)
		return -1;

	os_memset(buf, 0, 15);

	buf[15] = 0;
	os_memcpy(buf + 16, nonce, nonce_len);
	if (omac1_aes_128(key, buf, 16 + nonce_len, nonce_mac))
		goto fail;

	buf[15] = 1;
	os_memcpy(buf + 16, hdr, hdr_len);
	if (omac1_aes_128(key, buf, 16 + hdr_len, hdr_mac))
		goto fail;

	if (aes_128_ctr_encrypt(key, nonce_mac, data, data_len))
		goto fail;
	buf[15] = 2;
	os_memcpy(buf + 16, data, data_len);
	if (omac1_aes_128(key, buf, 16 + data_len, data_mac))
		goto fail;

	for (i = 0; i < AES_BLOCK_SIZE; i++)
		tag[i] = nonce_mac[i] ^ data_mac[i] ^ hdr_mac[i];

	ret = 0;
fail:
	os_free(buf);

	return ret;
}


/**
 * aes_128_eax_decrypt - AES-128 EAX mode decryption
 * @key: Key for decryption (16 bytes)
 * @nonce: Nonce for counter mode
 * @nonce_len: Nonce length in bytes
 * @hdr: Header data to be authenticity protected
 * @hdr_len: Length of the header data bytes
 * @data: Data to encrypt in-place
 * @data_len: Length of data in bytes
 * @tag: 16-byte tag value
 * Returns: 0 on success, -1 on failure, -2 if tag does not match
 */
int aes_128_eax_decrypt(const u8 *key, const u8 *nonce, size_t nonce_len,
			const u8 *hdr, size_t hdr_len,
			u8 *data, size_t data_len, const u8 *tag)
{
	u8 *buf;
	size_t buf_len;
	u8 nonce_mac[AES_BLOCK_SIZE], hdr_mac[AES_BLOCK_SIZE],
		data_mac[AES_BLOCK_SIZE];
	int i;

	if (nonce_len > data_len)
		buf_len = nonce_len;
	else
		buf_len = data_len;
	if (hdr_len > buf_len)
		buf_len = hdr_len;
	buf_len += 16;

	buf = os_malloc(buf_len);
	if (buf == NULL)
		return -1;

	os_memset(buf, 0, 15);

	buf[15] = 0;
	os_memcpy(buf + 16, nonce, nonce_len);
	if (omac1_aes_128(key, buf, 16 + nonce_len, nonce_mac)) {
		os_free(buf);
		return -1;
	}

	buf[15] = 1;
	os_memcpy(buf + 16, hdr, hdr_len);
	if (omac1_aes_128(key, buf, 16 + hdr_len, hdr_mac)) {
		os_free(buf);
		return -1;
	}

	buf[15] = 2;
	os_memcpy(buf + 16, data, data_len);
	if (omac1_aes_128(key, buf, 16 + data_len, data_mac)) {
		os_free(buf);
		return -1;
	}

	os_free(buf);

	for (i = 0; i < AES_BLOCK_SIZE; i++) {
		if (tag[i] != (nonce_mac[i] ^ data_mac[i] ^ hdr_mac[i]))
			return -2;
	}

	return aes_128_ctr_encrypt(key, nonce_mac, data, data_len);
}