aes.c

/* 
 * 
 * Glue Code for optimized 586 assembler version of AES
 *
 * Copyright (c) 2002, Dr Brian Gladman <>, 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.
 *
 * Copyright (c) 2003, Adam J. Richter <adam@yggdrasil.com> (conversion to
 * 2.5 API).
 * Copyright (c) 2003, 2004 Fruhwirth Clemens <clemens@endorphin.org>
 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>
 *
 */

#include <asm/byteorder.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/crypto.h>
#include <linux/linkage.h>

asmlinkage void aes_enc_blk(struct crypto_tfm *tfm, u8 *dst, const u8 *src);
asmlinkage void aes_dec_blk(struct crypto_tfm *tfm, u8 *dst, const u8 *src);

#define AES_MIN_KEY_SIZE	16
#define AES_MAX_KEY_SIZE	32
#define AES_BLOCK_SIZE		16
#define AES_KS_LENGTH		4 * AES_BLOCK_SIZE
#define RC_LENGTH		29

struct aes_ctx {
	u32 ekey[AES_KS_LENGTH];
	u32 rounds;
	u32 dkey[AES_KS_LENGTH];
};

#define WPOLY 0x011b
#define bytes2word(b0, b1, b2, b3)  \
	(((u32)(b3) << 24) | ((u32)(b2) << 16) | ((u32)(b1) << 8) | (b0))

/* define the finite field multiplies required for Rijndael */
#define f2(x) ((x) ? pow[log[x] + 0x19] : 0)
#define f3(x) ((x) ? pow[log[x] + 0x01] : 0)
#define f9(x) ((x) ? pow[log[x] + 0xc7] : 0)
#define fb(x) ((x) ? pow[log[x] + 0x68] : 0)
#define fd(x) ((x) ? pow[log[x] + 0xee] : 0)
#define fe(x) ((x) ? pow[log[x] + 0xdf] : 0)
#define fi(x) ((x) ?   pow[255 - log[x]]: 0)

static inline u32 upr(u32 x, int n)
{
	return (x << 8 * n) | (x >> (32 - 8 * n));
}

static inline u8 bval(u32 x, int n)
{
	return x >> 8 * n;
}

/* The forward and inverse affine transformations used in the S-box */
#define fwd_affine(x) \
	(w = (u32)x, w ^= (w<<1)^(w<<2)^(w<<3)^(w<<4), 0x63^(u8)(w^(w>>8)))

#define inv_affine(x) \
	(w = (u32)x, w = (w<<1)^(w<<3)^(w<<6), 0x05^(u8)(w^(w>>8)))

static u32 rcon_tab[RC_LENGTH];

u32 ft_tab[4][256];
u32 fl_tab[4][256];
static u32 im_tab[4][256];
u32 il_tab[4][256];
u32 it_tab[4][256];

static void gen_tabs(void)
{
	u32 i, w;
	u8 pow[512], log[256];

	/*
	 * log and power tables for GF(2^8) finite field with
	 * WPOLY as modular polynomial - the simplest primitive
	 * root is 0x03, used here to generate the tables.
	 */
	i = 0; w = 1; 
	
	do {
		pow[i] = (u8)w;
		pow[i + 255] = (u8)w;
		log[w] = (u8)i++;
		w ^=  (w << 1) ^ (w & 0x80 ? WPOLY : 0);
	} while (w != 1);
	
	for(i = 0, w = 1; i < RC_LENGTH; ++i) {
		rcon_tab[i] = bytes2word(w, 0, 0, 0);
		w = f2(w);
	}

	for(i = 0; i < 256; ++i) {
		u8 b;
		
		b = fwd_affine(fi((u8)i));
		w = bytes2word(f2(b), b, b, f3(b));

		/* tables for a normal encryption round */
		ft_tab[0][i] = w;
		ft_tab[1][i] = upr(w, 1);
		ft_tab[2][i] = upr(w, 2);
		ft_tab[3][i] = upr(w, 3);
		w = bytes2word(b, 0, 0, 0);
		
		/*
		 * tables for last encryption round
		 * (may also be used in the key schedule)
		 */
		fl_tab[0][i] = w;
		fl_tab[1][i] = upr(w, 1);
		fl_tab[2][i] = upr(w, 2);
		fl_tab[3][i] = upr(w, 3);
		
		b = fi(inv_affine((u8)i));
		w = bytes2word(fe(b), f9(b), fd(b), fb(b));

		/* tables for the inverse mix column operation  */
		im_tab[0][b] = w;
		im_tab[1][b] = upr(w, 1);
		im_tab[2][b] = upr(w, 2);
		im_tab[3][b] = upr(w, 3);

		/* tables for a normal decryption round */
		it_tab[0][i] = w;
		it_tab[1][i] = upr(w,1);
		it_tab[2][i] = upr(w,2);
		it_tab[3][i] = upr(w,3);

		w = bytes2word(b, 0, 0, 0);
		
		/* tables for last decryption round */
		il_tab[0][i] = w;
		il_tab[1][i] = upr(w,1);
		il_tab[2][i] = upr(w,2);
		il_tab[3][i] = upr(w,3);
    }
}

#define four_tables(x,tab,vf,rf,c)		\
(	tab[0][bval(vf(x,0,c),rf(0,c))]	^	\
	tab[1][bval(vf(x,1,c),rf(1,c))] ^	\
	tab[2][bval(vf(x,2,c),rf(2,c))] ^	\
	tab[3][bval(vf(x,3,c),rf(3,c))]		\
)

#define vf1(x,r,c)  (x)
#define rf1(r,c)    (r)
#define rf2(r,c)    ((r-c)&3)

#define inv_mcol(x) four_tables(x,im_tab,vf1,rf1,0)
#define ls_box(x,c) four_tables(x,fl_tab,vf1,rf2,c)

#define ff(x) inv_mcol(x)

#define ke4(k,i)							\
{									\
	k[4*(i)+4] = ss[0] ^= ls_box(ss[3],3) ^ rcon_tab[i];		\
	k[4*(i)+5] = ss[1] ^= ss[0];					\
	k[4*(i)+6] = ss[2] ^= ss[1];					\
	k[4*(i)+7] = ss[3] ^= ss[2];					\
}

#define kel4(k,i)							\
{									\
	k[4*(i)+4] = ss[0] ^= ls_box(ss[3],3) ^ rcon_tab[i];		\
	k[4*(i)+5] = ss[1] ^= ss[0];					\
	k[4*(i)+6] = ss[2] ^= ss[1]; k[4*(i)+7] = ss[3] ^= ss[2];	\
}

#define ke6(k,i)							\
{									\
	k[6*(i)+ 6] = ss[0] ^= ls_box(ss[5],3) ^ rcon_tab[i];		\
	k[6*(i)+ 7] = ss[1] ^= ss[0];					\
	k[6*(i)+ 8] = ss[2] ^= ss[1];					\
	k[6*(i)+ 9] = ss[3] ^= ss[2];					\
	k[6*(i)+10] = ss[4] ^= ss[3];					\
	k[6*(i)+11] = ss[5] ^= ss[4];					\
}

#define kel6(k,i)							\
{									\
	k[6*(i)+ 6] = ss[0] ^= ls_box(ss[5],3) ^ rcon_tab[i];		\
	k[6*(i)+ 7] = ss[1] ^= ss[0];					\
	k[6*(i)+ 8] = ss[2] ^= ss[1];					\
	k[6*(i)+ 9] = ss[3] ^= ss[2];					\
}

#define ke8(k,i)							\
{									\
	k[8*(i)+ 8] = ss[0] ^= ls_box(ss[7],3) ^ rcon_tab[i];		\
	k[8*(i)+ 9] = ss[1] ^= ss[0];					\
	k[8*(i)+10] = ss[2] ^= ss[1];					\
	k[8*(i)+11] = ss[3] ^= ss[2];					\
	k[8*(i)+12] = ss[4] ^= ls_box(ss[3],0);				\
	k[8*(i)+13] = ss[5] ^= ss[4];					\
	k[8*(i)+14] = ss[6] ^= ss[5];					\
	k[8*(i)+15] = ss[7] ^= ss[6];					\
}

#define kel8(k,i)							\
{									\
	k[8*(i)+ 8] = ss[0] ^= ls_box(ss[7],3) ^ rcon_tab[i];		\
	k[8*(i)+ 9] = ss[1] ^= ss[0];					\
	k[8*(i)+10] = ss[2] ^= ss[1];					\
	k[8*(i)+11] = ss[3] ^= ss[2];					\
}

#define kdf4(k,i)							\
{									\
	ss[0] = ss[0] ^ ss[2] ^ ss[1] ^ ss[3];				\
	ss[1] = ss[1] ^ ss[3];						\
	ss[2] = ss[2] ^ ss[3];						\
	ss[3] = ss[3];							\
	ss[4] = ls_box(ss[(i+3) % 4], 3) ^ rcon_tab[i];			\
	ss[i % 4] ^= ss[4];						\
	ss[4] ^= k[4*(i)];						\
	k[4*(i)+4] = ff(ss[4]);						\
	ss[4] ^= k[4*(i)+1];						\
	k[4*(i)+5] = ff(ss[4]);						\
	ss[4] ^= k[4*(i)+2];						\
	k[4*(i)+6] = ff(ss[4]);						\
	ss[4] ^= k[4*(i)+3];						\
	k[4*(i)+7] = ff(ss[4]);						\
}

#define kd4(k,i)							\
{									\
	ss[4] = ls_box(ss[(i+3) % 4], 3) ^ rcon_tab[i];			\
	ss[i % 4] ^= ss[4];						\
	ss[4] = ff(ss[4]);						\
	k[4*(i)+4] = ss[4] ^= k[4*(i)];					\
	k[4*(i)+5] = ss[4] ^= k[4*(i)+1];				\
	k[4*(i)+6] = ss[4] ^= k[4*(i)+2];				\
	k[4*(i)+7] = ss[4] ^= k[4*(i)+3];				\
}

#define kdl4(k,i)							\
{									\
	ss[4] = ls_box(ss[(i+3) % 4], 3) ^ rcon_tab[i];			\
	ss[i % 4] ^= ss[4];						\
	k[4*(i)+4] = (ss[0] ^= ss[1]) ^ ss[2] ^ ss[3];			\
	k[4*(i)+5] = ss[1] ^ ss[3];					\
	k[4*(i)+6] = ss[0];						\
	k[4*(i)+7] = ss[1];						\
}

#define kdf6(k,i)							\
{									\
	ss[0] ^= ls_box(ss[5],3) ^ rcon_tab[i];				\
	k[6*(i)+ 6] = ff(ss[0]);					\
	ss[1] ^= ss[0];							\
	k[6*(i)+ 7] = ff(ss[1]);					\
	ss[2] ^= ss[1];							\
	k[6*(i)+ 8] = ff(ss[2]);					\
	ss[3] ^= ss[2];							\
	k[6*(i)+ 9] = ff(ss[3]);					\
	ss[4] ^= ss[3];							\
	k[6*(i)+10] = ff(ss[4]);					\
	ss[5] ^= ss[4];							\
	k[6*(i)+11] = ff(ss[5]);					\
}

#define kd6(k,i)							\
{									\
	ss[6] = ls_box(ss[5],3) ^ rcon_tab[i];				\
	ss[0] ^= ss[6]; ss[6] = ff(ss[6]);				\
	k[6*(i)+ 6] = ss[6] ^= k[6*(i)];				\
	ss[1] ^= ss[0];							\
	k[6*(i)+ 7] = ss[6] ^= k[6*(i)+ 1];				\
	ss[2] ^= ss[1];							\
	k[6*(i)+ 8] = ss[6] ^= k[6*(i)+ 2];				\
	ss[3] ^= ss[2];							\
	k[6*(i)+ 9] = ss[6] ^= k[6*(i)+ 3];				\
	ss[4] ^= ss[3];							\
	k[6*(i)+10] = ss[6] ^= k[6*(i)+ 4];				\
	ss[5] ^= ss[4];							\
	k[6*(i)+11] = ss[6] ^= k[6*(i)+ 5];				\
}

#define kdl6(k,i)							\
{									\
	ss[0] ^= ls_box(ss[5],3) ^ rcon_tab[i];				\
	k[6*(i)+ 6] = ss[0];						\
	ss[1] ^= ss[0];							\
	k[6*(i)+ 7] = ss[1];						\
	ss[2] ^= ss[1];							\
	k[6*(i)+ 8] = ss[2];						\
	ss[3] ^= ss[2];							\
	k[6*(i)+ 9] = ss[3];						\
}

#define kdf8(k,i)							\
{									\
	ss[0] ^= ls_box(ss[7],3) ^ rcon_tab[i];				\
	k[8*(i)+ 8] = ff(ss[0]);					\
	ss[1] ^= ss[0];							\
	k[8*(i)+ 9] = ff(ss[1]);					\
	ss[2] ^= ss[1];							\
	k[8*(i)+10] = ff(ss[2]);					\
	ss[3] ^= ss[2];							\
	k[8*(i)+11] = ff(ss[3]);					\
	ss[4] ^= ls_box(ss[3],0);					\
	k[8*(i)+12] = ff(ss[4]);					\
	ss[5] ^= ss[4];							\
	k[8*(i)+13] = ff(ss[5]);					\
	ss[6] ^= ss[5];							\
	k[8*(i)+14] = ff(ss[6]);					\
	ss[7] ^= ss[6];							\
	k[8*(i)+15] = ff(ss[7]);					\
}

#define kd8(k,i)							\
{									\
	u32 __g = ls_box(ss[7],3) ^ rcon_tab[i];			\
	ss[0] ^= __g;							\
	__g = ff(__g);							\
	k[8*(i)+ 8] = __g ^= k[8*(i)];					\
	ss[1] ^= ss[0];							\
	k[8*(i)+ 9] = __g ^= k[8*(i)+ 1];				\
	ss[2] ^= ss[1];							\
	k[8*(i)+10] = __g ^= k[8*(i)+ 2];				\
	ss[3] ^= ss[2];							\
	k[8*(i)+11] = __g ^= k[8*(i)+ 3];				\
	__g = ls_box(ss[3],0);						\
	ss[4] ^= __g;							\
	__g = ff(__g);							\
	k[8*(i)+12] = __g ^= k[8*(i)+ 4];				\
	ss[5] ^= ss[4];							\
	k[8*(i)+13] = __g ^= k[8*(i)+ 5];				\
	ss[6] ^= ss[5];							\
	k[8*(i)+14] = __g ^= k[8*(i)+ 6];				\
	ss[7] ^= ss[6];							\
	k[8*(i)+15] = __g ^= k[8*(i)+ 7];				\
}

#define kdl8(k,i)							\
{									\
	ss[0] ^= ls_box(ss[7],3) ^ rcon_tab[i];				\
	k[8*(i)+ 8] = ss[0];						\
	ss[1] ^= ss[0];							\
	k[8*(i)+ 9] = ss[1];						\
	ss[2] ^= ss[1];							\
	k[8*(i)+10] = ss[2];						\
	ss[3] ^= ss[2];							\
	k[8*(i)+11] = ss[3];						\
}

static int aes_set_key(struct crypto_tfm *tfm, const u8 *in_key,
		       unsigned int key_len, u32 *flags)
{
	int i;
	u32 ss[8];
	struct aes_ctx *ctx = crypto_tfm_ctx(tfm);
	const __le32 *key = (const __le32 *)in_key;

	/* encryption schedule */
	
	ctx->ekey[0] = ss[0] = le32_to_cpu(key[0]);
	ctx->ekey[1] = ss[1] = le32_to_cpu(key[1]);
	ctx->ekey[2] = ss[2] = le32_to_cpu(key[2]);
	ctx->ekey[3] = ss[3] = le32_to_cpu(key[3]);

	switch(key_len) {
	case 16:
		for (i = 0; i < 9; i++)
			ke4(ctx->ekey, i);
		kel4(ctx->ekey, 9);
		ctx->rounds = 10;
		break;
		
	case 24:
		ctx->ekey[4] = ss[4] = le32_to_cpu(key[4]);
		ctx->ekey[5] = ss[5] = le32_to_cpu(key[5]);
		for (i = 0; i < 7; i++)
			ke6(ctx->ekey, i);
		kel6(ctx->ekey, 7); 
		ctx->rounds = 12;
		break;

	case 32:
		ctx->ekey[4] = ss[4] = le32_to_cpu(key[4]);
		ctx->ekey[5] = ss[5] = le32_to_cpu(key[5]);
		ctx->ekey[6] = ss[6] = le32_to_cpu(key[6]);
		ctx->ekey[7] = ss[7] = le32_to_cpu(key[7]);
		for (i = 0; i < 6; i++)
			ke8(ctx->ekey, i);
		kel8(ctx->ekey, 6);
		ctx->rounds = 14;
		break;

	default:
		*flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
		return -EINVAL;
	}
	
	/* decryption schedule */
	
	ctx->dkey[0] = ss[0] = le32_to_cpu(key[0]);
	ctx->dkey[1] = ss[1] = le32_to_cpu(key[1]);
	ctx->dkey[2] = ss[2] = le32_to_cpu(key[2]);
	ctx->dkey[3] = ss[3] = le32_to_cpu(key[3]);

	switch (key_len) {
	case 16:
		kdf4(ctx->dkey, 0);
		for (i = 1; i < 9; i++)
			kd4(ctx->dkey, i);
		kdl4(ctx->dkey, 9);
		break;
		
	case 24:
		ctx->dkey[4] = ff(ss[4] = le32_to_cpu(key[4]));
		ctx->dkey[5] = ff(ss[5] = le32_to_cpu(key[5]));
		kdf6(ctx->dkey, 0);
		for (i = 1; i < 7; i++)
			kd6(ctx->dkey, i);
		kdl6(ctx->dkey, 7);
		break;

	case 32:
		ctx->dkey[4] = ff(ss[4] = le32_to_cpu(key[4]));
		ctx->dkey[5] = ff(ss[5] = le32_to_cpu(key[5]));
		ctx->dkey[6] = ff(ss[6] = le32_to_cpu(key[6]));
		ctx->dkey[7] = ff(ss[7] = le32_to_cpu(key[7]));
		kdf8(ctx->dkey, 0);
		for (i = 1; i < 6; i++)
			kd8(ctx->dkey, i);
		kdl8(ctx->dkey, 6);
		break;
	}
	return 0;
}

static void aes_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
	aes_enc_blk(tfm, dst, src);
}

static void aes_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
	aes_dec_blk(tfm, dst, src);
}

static struct crypto_alg aes_alg = {
	.cra_name		=	"aes",
	.cra_driver_name	=	"aes-i586",
	.cra_priority		=	200,
	.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, i586 asm optimized");
MODULE_LICENSE("Dual BSD/GPL");
MODULE_AUTHOR("Fruhwirth Clemens, James Morris, Brian Gladman, Adam Richter");
MODULE_ALIAS("aes");