tea.c

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/* 
 * Cryptographic API.
 *
 * TEA, XTEA, and XETA crypto alogrithms
 *
 * The TEA and Xtended TEA algorithms were developed by David Wheeler 
 * and Roger Needham at the Computer Laboratory of Cambridge University.
 *
 * Due to the order of evaluation in XTEA many people have incorrectly
 * implemented it.  XETA (XTEA in the wrong order), exists for
 * compatibility with these implementations.
 *
 * Copyright (c) 2004 Aaron Grothe [email protected]
 *
 * 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.
 *
 */

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

#define TEA_KEY_SIZE        16
#define TEA_BLOCK_SIZE      8
#define TEA_ROUNDS      32
#define TEA_DELTA       0x9e3779b9

#define XTEA_KEY_SIZE       16
#define XTEA_BLOCK_SIZE     8
#define XTEA_ROUNDS     32
#define XTEA_DELTA      0x9e3779b9

struct tea_ctx {
    u32 KEY[4];
};

struct xtea_ctx {
    u32 KEY[4];
};

static int tea_setkey(struct crypto_tfm *tfm, const u8 *in_key,
              unsigned int key_len)
{
    struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *key = (const __le32 *)in_key;

    ctx->KEY[0] = le32_to_cpu(key[0]);
    ctx->KEY[1] = le32_to_cpu(key[1]);
    ctx->KEY[2] = le32_to_cpu(key[2]);
    ctx->KEY[3] = le32_to_cpu(key[3]);

    return 0; 

}

static void tea_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
    u32 y, z, n, sum = 0;
    u32 k0, k1, k2, k3;
    struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *in = (const __le32 *)src;
    __le32 *out = (__le32 *)dst;

    y = le32_to_cpu(in[0]);
    z = le32_to_cpu(in[1]);

    k0 = ctx->KEY[0];
    k1 = ctx->KEY[1];
    k2 = ctx->KEY[2];
    k3 = ctx->KEY[3];

    n = TEA_ROUNDS;

    while (n-- > 0) {
        sum += TEA_DELTA;
        y += ((z << 4) + k0) ^ (z + sum) ^ ((z >> 5) + k1);
        z += ((y << 4) + k2) ^ (y + sum) ^ ((y >> 5) + k3);
    }
    
    out[0] = cpu_to_le32(y);
    out[1] = cpu_to_le32(z);
}

static void tea_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
    u32 y, z, n, sum;
    u32 k0, k1, k2, k3;
    struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *in = (const __le32 *)src;
    __le32 *out = (__le32 *)dst;

    y = le32_to_cpu(in[0]);
    z = le32_to_cpu(in[1]);

    k0 = ctx->KEY[0];
    k1 = ctx->KEY[1];
    k2 = ctx->KEY[2];
    k3 = ctx->KEY[3];

    sum = TEA_DELTA << 5;

    n = TEA_ROUNDS;

    while (n-- > 0) {
        z -= ((y << 4) + k2) ^ (y + sum) ^ ((y >> 5) + k3);
        y -= ((z << 4) + k0) ^ (z + sum) ^ ((z >> 5) + k1);
        sum -= TEA_DELTA;
    }
    
    out[0] = cpu_to_le32(y);
    out[1] = cpu_to_le32(z);
}

static int xtea_setkey(struct crypto_tfm *tfm, const u8 *in_key,
               unsigned int key_len)
{
    struct xtea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *key = (const __le32 *)in_key;

    ctx->KEY[0] = le32_to_cpu(key[0]);
    ctx->KEY[1] = le32_to_cpu(key[1]);
    ctx->KEY[2] = le32_to_cpu(key[2]);
    ctx->KEY[3] = le32_to_cpu(key[3]);

    return 0; 

}

static void xtea_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
    u32 y, z, sum = 0;
    u32 limit = XTEA_DELTA * XTEA_ROUNDS;
    struct xtea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *in = (const __le32 *)src;
    __le32 *out = (__le32 *)dst;

    y = le32_to_cpu(in[0]);
    z = le32_to_cpu(in[1]);

    while (sum != limit) {
        y += ((z << 4 ^ z >> 5) + z) ^ (sum + ctx->KEY[sum&3]); 
        sum += XTEA_DELTA;
        z += ((y << 4 ^ y >> 5) + y) ^ (sum + ctx->KEY[sum>>11 &3]); 
    }
    
    out[0] = cpu_to_le32(y);
    out[1] = cpu_to_le32(z);
}

static void xtea_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
    u32 y, z, sum;
    struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *in = (const __le32 *)src;
    __le32 *out = (__le32 *)dst;

    y = le32_to_cpu(in[0]);
    z = le32_to_cpu(in[1]);

    sum = XTEA_DELTA * XTEA_ROUNDS;

    while (sum) {
        z -= ((y << 4 ^ y >> 5) + y) ^ (sum + ctx->KEY[sum>>11 & 3]);
        sum -= XTEA_DELTA;
        y -= ((z << 4 ^ z >> 5) + z) ^ (sum + ctx->KEY[sum & 3]);
    }
    
    out[0] = cpu_to_le32(y);
    out[1] = cpu_to_le32(z);
}


static void xeta_encrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
    u32 y, z, sum = 0;
    u32 limit = XTEA_DELTA * XTEA_ROUNDS;
    struct xtea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *in = (const __le32 *)src;
    __le32 *out = (__le32 *)dst;

    y = le32_to_cpu(in[0]);
    z = le32_to_cpu(in[1]);

    while (sum != limit) {
        y += (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum&3];
        sum += XTEA_DELTA;
        z += (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 &3];
    }
    
    out[0] = cpu_to_le32(y);
    out[1] = cpu_to_le32(z);
}

static void xeta_decrypt(struct crypto_tfm *tfm, u8 *dst, const u8 *src)
{
    u32 y, z, sum;
    struct tea_ctx *ctx = crypto_tfm_ctx(tfm);
    const __le32 *in = (const __le32 *)src;
    __le32 *out = (__le32 *)dst;

    y = le32_to_cpu(in[0]);
    z = le32_to_cpu(in[1]);

    sum = XTEA_DELTA * XTEA_ROUNDS;

    while (sum) {
        z -= (y << 4 ^ y >> 5) + (y ^ sum) + ctx->KEY[sum>>11 & 3];
        sum -= XTEA_DELTA;
        y -= (z << 4 ^ z >> 5) + (z ^ sum) + ctx->KEY[sum & 3];
    }
    
    out[0] = cpu_to_le32(y);
    out[1] = cpu_to_le32(z);
}

static struct crypto_alg tea_algs[3] = { {
    .cra_name       =   "tea",
    .cra_flags      =   CRYPTO_ALG_TYPE_CIPHER,
    .cra_blocksize      =   TEA_BLOCK_SIZE,
    .cra_ctxsize        =   sizeof (struct tea_ctx),
    .cra_alignmask      =   3,
    .cra_module     =   THIS_MODULE,
    .cra_u          =   { .cipher = {
    .cia_min_keysize    =   TEA_KEY_SIZE,
    .cia_max_keysize    =   TEA_KEY_SIZE,
    .cia_setkey     =   tea_setkey,
    .cia_encrypt        =   tea_encrypt,
    .cia_decrypt        =   tea_decrypt } }
}, {
    .cra_name       =   "xtea",
    .cra_flags      =   CRYPTO_ALG_TYPE_CIPHER,
    .cra_blocksize      =   XTEA_BLOCK_SIZE,
    .cra_ctxsize        =   sizeof (struct xtea_ctx),
    .cra_alignmask      =   3,
    .cra_module     =   THIS_MODULE,
    .cra_u          =   { .cipher = {
    .cia_min_keysize    =   XTEA_KEY_SIZE,
    .cia_max_keysize    =   XTEA_KEY_SIZE,
    .cia_setkey     =   xtea_setkey,
    .cia_encrypt        =   xtea_encrypt,
    .cia_decrypt        =   xtea_decrypt } }
}, {
    .cra_name       =   "xeta",
    .cra_flags      =   CRYPTO_ALG_TYPE_CIPHER,
    .cra_blocksize      =   XTEA_BLOCK_SIZE,
    .cra_ctxsize        =   sizeof (struct xtea_ctx),
    .cra_alignmask      =   3,
    .cra_module     =   THIS_MODULE,
    .cra_u          =   { .cipher = {
    .cia_min_keysize    =   XTEA_KEY_SIZE,
    .cia_max_keysize    =   XTEA_KEY_SIZE,
    .cia_setkey     =   xtea_setkey,
    .cia_encrypt        =   xeta_encrypt,
    .cia_decrypt        =   xeta_decrypt } }
} };

static int __init tea_mod_init(void)
{
    return crypto_register_algs(tea_algs, ARRAY_SIZE(tea_algs));
}

static void __exit tea_mod_fini(void)
{
    crypto_unregister_algs(tea_algs, ARRAY_SIZE(tea_algs));
}

MODULE_ALIAS("xtea");
MODULE_ALIAS("xeta");

module_init(tea_mod_init);
module_exit(tea_mod_fini);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("TEA, XTEA & XETA Cryptographic Algorithms");