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/*
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* Cryptographic API
*
* ARC4 Cipher Algorithm
*
* Jon Oberheide < jon @ oberheide . org >
*
* 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 .
*
*/
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# include <linux/module.h>
# include <linux/init.h>
# include <linux/crypto.h>
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# include <crypto/algapi.h>
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# define ARC4_MIN_KEY_SIZE 1
# define ARC4_MAX_KEY_SIZE 256
# define ARC4_BLOCK_SIZE 1
struct arc4_ctx {
u8 S [ 256 ] ;
u8 x , y ;
} ;
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static int arc4_set_key ( struct crypto_tfm * tfm , const u8 * in_key ,
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unsigned int key_len )
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{
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struct arc4_ctx * ctx = crypto_tfm_ctx ( tfm ) ;
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int i , j = 0 , k = 0 ;
ctx - > x = 1 ;
ctx - > y = 0 ;
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for ( i = 0 ; i < 256 ; i + + )
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ctx - > S [ i ] = i ;
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for ( i = 0 ; i < 256 ; i + + ) {
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u8 a = ctx - > S [ i ] ;
j = ( j + in_key [ k ] + a ) & 0xff ;
ctx - > S [ i ] = ctx - > S [ j ] ;
ctx - > S [ j ] = a ;
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if ( + + k > = key_len )
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k = 0 ;
}
return 0 ;
}
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static void arc4_crypt ( struct arc4_ctx * ctx , u8 * out , const u8 * in ,
unsigned int len )
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{
u8 * const S = ctx - > S ;
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u8 x , y , a , b ;
u8 ty , ta , tb ;
if ( len = = 0 )
return ;
x = ctx - > x ;
y = ctx - > y ;
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a = S [ x ] ;
y = ( y + a ) & 0xff ;
b = S [ y ] ;
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do {
S [ y ] = a ;
a = ( a + b ) & 0xff ;
S [ x ] = b ;
x = ( x + 1 ) & 0xff ;
ta = S [ x ] ;
ty = ( y + ta ) & 0xff ;
tb = S [ ty ] ;
* out + + = * in + + ^ S [ a ] ;
if ( - - len = = 0 )
break ;
y = ty ;
a = ta ;
b = tb ;
} while ( true ) ;
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ctx - > x = x ;
ctx - > y = y ;
}
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static void arc4_crypt_one ( struct crypto_tfm * tfm , u8 * out , const u8 * in )
{
arc4_crypt ( crypto_tfm_ctx ( tfm ) , out , in , 1 ) ;
}
static int ecb_arc4_crypt ( struct blkcipher_desc * desc , struct scatterlist * dst ,
struct scatterlist * src , unsigned int nbytes )
{
struct arc4_ctx * ctx = crypto_blkcipher_ctx ( desc - > tfm ) ;
struct blkcipher_walk walk ;
int err ;
blkcipher_walk_init ( & walk , dst , src , nbytes ) ;
err = blkcipher_walk_virt ( desc , & walk ) ;
while ( walk . nbytes > 0 ) {
u8 * wsrc = walk . src . virt . addr ;
u8 * wdst = walk . dst . virt . addr ;
arc4_crypt ( ctx , wdst , wsrc , walk . nbytes ) ;
err = blkcipher_walk_done ( desc , & walk , 0 ) ;
}
return err ;
}
static struct crypto_alg arc4_algs [ 2 ] = { {
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. cra_name = " arc4 " ,
. cra_flags = CRYPTO_ALG_TYPE_CIPHER ,
. cra_blocksize = ARC4_BLOCK_SIZE ,
. cra_ctxsize = sizeof ( struct arc4_ctx ) ,
. cra_module = THIS_MODULE ,
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. cra_u = {
. cipher = {
. cia_min_keysize = ARC4_MIN_KEY_SIZE ,
. cia_max_keysize = ARC4_MAX_KEY_SIZE ,
. cia_setkey = arc4_set_key ,
. cia_encrypt = arc4_crypt_one ,
. cia_decrypt = arc4_crypt_one ,
} ,
} ,
} , {
. cra_name = " ecb(arc4) " ,
. cra_priority = 100 ,
. cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER ,
. cra_blocksize = ARC4_BLOCK_SIZE ,
. cra_ctxsize = sizeof ( struct arc4_ctx ) ,
. cra_alignmask = 0 ,
. cra_type = & crypto_blkcipher_type ,
. cra_module = THIS_MODULE ,
. cra_u = {
. blkcipher = {
. min_keysize = ARC4_MIN_KEY_SIZE ,
. max_keysize = ARC4_MAX_KEY_SIZE ,
. setkey = arc4_set_key ,
. encrypt = ecb_arc4_crypt ,
. decrypt = ecb_arc4_crypt ,
} ,
} ,
} } ;
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static int __init arc4_init ( void )
{
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return crypto_register_algs ( arc4_algs , ARRAY_SIZE ( arc4_algs ) ) ;
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}
static void __exit arc4_exit ( void )
{
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crypto_unregister_algs ( arc4_algs , ARRAY_SIZE ( arc4_algs ) ) ;
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}
module_init ( arc4_init ) ;
module_exit ( arc4_exit ) ;
MODULE_LICENSE ( " GPL " ) ;
MODULE_DESCRIPTION ( " ARC4 Cipher Algorithm " ) ;
MODULE_AUTHOR ( " Jon Oberheide <jon@oberheide.org> " ) ;