aes.c

/*
 * Cryptographic API.
 *
 * AES Cipher Algorithm.
 *
 * Based on Brian Gladman's code.
 *
 * Linux developers:
 *  Alexander Kjeldaas <astor@fast.no>
 *  Herbert Valerio Riedel <hvr@hvrlab.org>
 *  Kyle McMartin <kyle@debian.org>
 *  Adam J. Richter <adam@yggdrasil.com> (conversion to 2.5 API).
 *  Andreas Steinmetz <ast@domdv.de> (adapted to x86_64 assembler)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * ---------------------------------------------------------------------------
 * Copyright (c) 2002, Dr Brian Gladman <brg@gladman.me.uk>, Worcester, UK.
 * All rights reserved.
 *
 * LICENSE TERMS
 *
 * The free distribution and use of this software in both source and binary
 * form is allowed (with or without changes) provided that:
 *
 *   1. distributions of this source code include the above copyright
 *      notice, this list of conditions and the following disclaimer;
 *
 *   2. distributions in binary form include the above copyright
 *      notice, this list of conditions and the following disclaimer
 *      in the documentation and/or other associated materials;
 *
 *   3. the copyright holder's name is not used to endorse products
 *      built using this software without specific written permission.
 *
 * ALTERNATIVELY, provided that this notice is retained in full, this product
 * may be distributed under the terms of the GNU General Public License (GPL),
 * in which case the provisions of the GPL apply INSTEAD OF those given above.
 *
 * DISCLAIMER
 *
 * This software is provided 'as is' with no explicit or implied warranties
 * in respect of its properties, including, but not limited to, correctness
 * and/or fitness for purpose.
 * ---------------------------------------------------------------------------
 */

/* Some changes from the Gladman version:
    s/RIJNDAEL(e_key)/E_KEY/g
    s/RIJNDAEL(d_key)/D_KEY/g
*/

#include <asm/byteorder.h>
#include <linux/bitops.h>
#include <linux/crypto.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/types.h>

#define AES_MIN_KEY_SIZE	16
#define AES_MAX_KEY_SIZE	32

#define AES_BLOCK_SIZE		16

/*
 * #define byte(x, nr) ((unsigned char)((x) >> (nr*8)))
 */
static inline u8 byte(const u32 x, const unsigned n)
{
	return x >> (n << 3);
}

#define u32_in(x) le32_to_cpu(*(const __le32 *)(x))

struct aes_ctx
{
	u32 key_length;
	u32 E[60];
	u32 D[60];
};

#define E_KEY ctx->E
#define D_KEY ctx->D

static u8 pow_tab[256] __initdata;
static u8 log_tab[256] __initdata;
static u8 sbx_tab[256] __initdata;
static u8 isb_tab[256] __initdata;
static u32 rco_tab[10];
u32 aes_ft_tab[4][256];
u32 aes_it_tab[4][256];

u32 aes_fl_tab[4][256];
u32 aes_il_tab[4][256];

static inline u8 f_mult(u8 a, u8 b)
{
	u8 aa = log_tab[a], cc = aa + log_tab[b];

	return pow_tab[cc + (cc < aa ? 1 : 0)];
}

#define ff_mult(a, b) (a && b ? f_mult(a, b) : 0)

#define ls_box(x)				\
	(aes_fl_tab[0][byte(x, 0)] ^		\
	 aes_fl_tab[1][byte(x, 1)] ^		\
	 aes_fl_tab[2][byte(x, 2)] ^		\
	 aes_fl_tab[3][byte(x, 3)])

static void __init gen_tabs(void)
{
	u32 i, t;
	u8 p, q;

	/* log and power tables for GF(2**8) finite field with
	   0x011b as modular polynomial - the simplest primitive
	   root is 0x03, used here to generate the tables */

	for (i = 0, p = 1; i < 256; ++i) {
		pow_tab[i] = (u8)p;
		log_tab[p] = (u8)i;

		p ^= (p << 1) ^ (p & 0x80 ? 0x01b : 0);
	}

	log_tab[1] = 0;

	for (i = 0, p = 1; i < 10; ++i) {
		rco_tab[i] = p;

		p = (p << 1) ^ (p & 0x80 ? 0x01b : 0);
	}

	for (i = 0; i < 256; ++i) {
		p = (i ? pow_tab[255 - log_tab[i]] : 0);
		q = ((p >> 7) | (p << 1)) ^ ((p >> 6) | (p << 2));
		p ^= 0x63 ^ q ^ ((q >> 6) | (q << 2));
		sbx_tab[i] = p;
		isb_tab[p] = (u8)i;
	}

	for (i = 0; i < 256; ++i) {
		p = sbx_tab[i];

		t = p;
		aes_fl_tab[0][i] = t;
		aes_fl_tab[1][i] = rol32(t, 8);
		aes_fl_tab[2][i] = rol32(t, 16);
		aes_fl_tab[3][i] = rol32(t, 24);

		t = ((u32)ff_mult(2, p)) |
		    ((u32)p << 8) |
		    ((u32)p << 16) | ((u32)ff_mult(3, p) << 24);

		aes_ft_tab[0][i] = t;
		aes_ft_tab[1][i] = rol32(t, 8);
		aes_ft_tab[2][i] = rol32(t, 16);
		aes_ft_tab[3][i] = rol32(t, 24);

		p = isb_tab[i];

		t = p;
		aes_il_tab[0][i] = t;
		aes_il_tab[1][i] = rol32(t, 8);
		aes_il_tab[2][i] = rol32(t, 16);
		aes_il_tab[3][i] = rol32(t, 24);

		t = ((u32)ff_mult(14, p)) |
		    ((u32)ff_mult(9, p) << 8) |
		    ((u32)ff_mult(13, p) << 16) |
		    ((u32)ff_mult(11, p) << 24);

		aes_it_tab[0][i] = t;
		aes_it_tab[1][i] = rol32(t, 8);
		aes_it_tab[2][i] = rol32(t, 16);
		aes_it_tab[3][i] = rol32(t, 24);
	}
}

#define star_x(x) (((x) & 0x7f7f7f7f) << 1) ^ ((((x) & 0x80808080) >> 7) * 0x1b)

#define imix_col(y, x)			\
	u    = star_x(x);		\
	v    = star_x(u);		\
	w    = star_x(v);		\
	t    = w ^ (x);			\
	(y)  = u ^ v ^ w;		\
	(y) ^= ror32(u ^ t,  8) ^	\
	       ror32(v ^ t, 16) ^	\
	       ror32(t, 24)

/* initialise the key schedule from the user supplied key */

#define loop4(i)					\
{							\
	t = ror32(t,  8); t = ls_box(t) ^ rco_tab[i];	\
	t ^= E_KEY[4 * i];     E_KEY[4 * i + 4] = t;	\
	t ^= E_KEY[4 * i + 1]; E_KEY[4 * i + 5] = t;	\
	t ^= E_KEY[4 * i + 2]; E_KEY[4 * i + 6] = t;	\
	t ^= E_KEY[4 * i + 3]; E_KEY[4 * i + 7] = t;	\
}

#define loop6(i)					\
{							\
	t = ror32(t,  8); t = ls_box(t) ^ rco_tab[i];	\
	t ^= E_KEY[6 * i];     E_KEY[6 * i + 6] = t;	\
	t ^= E_KEY[6 * i + 1]; E_KEY[6 * i + 7] = t;	\
	t ^= E_KEY[6 * i + 2]; E_KEY[6 * i + 8] = t;	\
	t ^= E_KEY[6 * i + 3]; E_KEY[6 * i + 9] = t;	\
	t ^= E_KEY[6 * i + 4]; E_KEY[6 * i + 10] = t;	\
	t ^= E_KEY[6 * i + 5]; E_KEY[6 * i + 11] = t;	\
}

#define loop8(i)					\
{							\
	t = ror32(t,  8); ; t = ls_box(t) ^ rco_tab[i];	\
	t ^= E_KEY[8 * i];     E_KEY[8 * i + 8] = t;	\
	t ^= E_KEY[8 * i + 1]; E_KEY[8 * i + 9] = t;	\
	t ^= E_KEY[8 * i + 2]; E_KEY[8 * i + 10] = t;	\
	t ^= E_KEY[8 * i + 3]; E_KEY[8 * i + 11] = t;	\
	t  = E_KEY[8 * i + 4] ^ ls_box(t);		\
	E_KEY[8 * i + 12] = t;				\
	t ^= E_KEY[8 * i + 5]; E_KEY[8 * i + 13] = t;	\
	t ^= E_KEY[8 * i + 6]; E_KEY[8 * i + 14] = t;	\
	t ^= E_KEY[8 * i + 7]; E_KEY[8 * i + 15] = t;	\
}

static int aes_set_key(void *ctx_arg, const u8 *in_key, unsigned int key_len,
		       u32 *flags)
{
	struct aes_ctx *ctx = ctx_arg;
	u32 i, j, t, u, v, w;

	if (key_len != 16 && key_len != 24 && key_len != 32) {
		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
		return -EINVAL;
	}

	ctx->key_length = key_len;

	D_KEY[key_len + 24] = E_KEY[0] = u32_in(in_key);
	D_KEY[key_len + 25] = E_KEY[1] = u32_in(in_key + 4);
	D_KEY[key_len + 26] = E_KEY[2] = u32_in(in_key + 8);
	D_KEY[key_len + 27] = E_KEY[3] = u32_in(in_key + 12);

	switch (key_len) {
	case 16:
		t = E_KEY[3];
		for (i = 0; i < 10; ++i)
			loop4(i);
		break;

	case 24:
		E_KEY[4] = u32_in(in_key + 16);
		t = E_KEY[5] = u32_in(in_key + 20);
		for (i = 0; i < 8; ++i)
			loop6 (i);
		break;

	case 32:
		E_KEY[4] = u32_in(in_key + 16);
		E_KEY[5] = u32_in(in_key + 20);
		E_KEY[6] = u32_in(in_key + 24);
		t = E_KEY[7] = u32_in(in_key + 28);
		for (i = 0; i < 7; ++i)
			loop8(i);
		break;
	}

	D_KEY[0] = E_KEY[key_len + 24];
	D_KEY[1] = E_KEY[key_len + 25];
	D_KEY[2] = E_KEY[key_len + 26];
	D_KEY[3] = E_KEY[key_len + 27];

	for (i = 4; i < key_len + 24; ++i) {
		j = key_len + 24 - (i & ~3) + (i & 3);
		imix_col(D_KEY[j], E_KEY[i]);
	}

	return 0;
}

extern void aes_encrypt(void *ctx_arg, u8 *out, const u8 *in);
extern void aes_decrypt(void *ctx_arg, u8 *out, const u8 *in);

static struct crypto_alg aes_alg = {
	.cra_name		=	"aes",
	.cra_flags		=	CRYPTO_ALG_TYPE_CIPHER,
	.cra_blocksize		=	AES_BLOCK_SIZE,
	.cra_ctxsize		=	sizeof(struct aes_ctx),
	.cra_module		=	THIS_MODULE,
	.cra_list		=	LIST_HEAD_INIT(aes_alg.cra_list),
	.cra_u			=	{
		.cipher = {
			.cia_min_keysize	=	AES_MIN_KEY_SIZE,
			.cia_max_keysize	=	AES_MAX_KEY_SIZE,
			.cia_setkey	   	= 	aes_set_key,
			.cia_encrypt	 	=	aes_encrypt,
			.cia_decrypt	  	=	aes_decrypt
		}
	}
};

static int __init aes_init(void)
{
	gen_tabs();
	return crypto_register_alg(&aes_alg);
}

static void __exit aes_fini(void)
{
	crypto_unregister_alg(&aes_alg);
}

module_init(aes_init);
module_exit(aes_fini);

MODULE_DESCRIPTION("Rijndael (AES) Cipher Algorithm");
MODULE_LICENSE("GPL");