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aes_generic.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).
 *
 * 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 <linux/module.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/crypto.h>
#include <asm/byteorder.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);
}

struct aes_ctx {
      int key_length;
      u32 buf[120];
};

#define E_KEY (&ctx->buf[0])
#define D_KEY (&ctx->buf[60])

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];
static u32 ft_tab[4][256];
static u32 it_tab[4][256];

static u32 fl_tab[4][256];
static u32 il_tab[4][256];

static inline u8 __init
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 f_rn(bo, bi, n, k)                            \
    bo[n] =  ft_tab[0][byte(bi[n],0)] ^                     \
             ft_tab[1][byte(bi[(n + 1) & 3],1)] ^           \
             ft_tab[2][byte(bi[(n + 2) & 3],2)] ^           \
             ft_tab[3][byte(bi[(n + 3) & 3],3)] ^ *(k + n)

#define i_rn(bo, bi, n, k)                            \
    bo[n] =  it_tab[0][byte(bi[n],0)] ^                     \
             it_tab[1][byte(bi[(n + 3) & 3],1)] ^           \
             it_tab[2][byte(bi[(n + 2) & 3],2)] ^           \
             it_tab[3][byte(bi[(n + 1) & 3],3)] ^ *(k + n)

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

#define f_rl(bo, bi, n, k)                            \
    bo[n] =  fl_tab[0][byte(bi[n],0)] ^                     \
             fl_tab[1][byte(bi[(n + 1) & 3],1)] ^           \
             fl_tab[2][byte(bi[(n + 2) & 3],2)] ^           \
             fl_tab[3][byte(bi[(n + 3) & 3],3)] ^ *(k + n)

#define i_rl(bo, bi, n, k)                            \
    bo[n] =  il_tab[0][byte(bi[n],0)] ^                     \
             il_tab[1][byte(bi[(n + 3) & 3],1)] ^           \
             il_tab[2][byte(bi[(n + 2) & 3],2)] ^           \
             il_tab[3][byte(bi[(n + 1) & 3],3)] ^ *(k + n)

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;
            fl_tab[0][i] = t;
            fl_tab[1][i] = rol32(t, 8);
            fl_tab[2][i] = rol32(t, 16);
            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);

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

            p = isb_tab[i];

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

            it_tab[0][i] = t;
            it_tab[1][i] = rol32(t, 8);
            it_tab[2][i] = rol32(t, 16);
            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(struct crypto_tfm *tfm, const u8 *in_key,
                   unsigned int key_len)
{
      struct aes_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *key = (const __le32 *)in_key;
      u32 *flags = &tfm->crt_flags;
      u32 i, t, u, v, w;

      if (key_len % 8) {
            *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
            return -EINVAL;
      }

      ctx->key_length = key_len;

      E_KEY[0] = le32_to_cpu(key[0]);
      E_KEY[1] = le32_to_cpu(key[1]);
      E_KEY[2] = le32_to_cpu(key[2]);
      E_KEY[3] = le32_to_cpu(key[3]);

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

      case 24:
            E_KEY[4] = le32_to_cpu(key[4]);
            t = E_KEY[5] = le32_to_cpu(key[5]);
            for (i = 0; i < 8; ++i)
                  loop6 (i);
            break;

      case 32:
            E_KEY[4] = le32_to_cpu(key[4]);
            E_KEY[5] = le32_to_cpu(key[5]);
            E_KEY[6] = le32_to_cpu(key[6]);
            t = E_KEY[7] = le32_to_cpu(key[7]);
            for (i = 0; i < 7; ++i)
                  loop8 (i);
            break;
      }

      D_KEY[0] = E_KEY[0];
      D_KEY[1] = E_KEY[1];
      D_KEY[2] = E_KEY[2];
      D_KEY[3] = E_KEY[3];

      for (i = 4; i < key_len + 24; ++i) {
            imix_col (D_KEY[i], E_KEY[i]);
      }

      return 0;
}

/* encrypt a block of text */

#define f_nround(bo, bi, k) \
    f_rn(bo, bi, 0, k);     \
    f_rn(bo, bi, 1, k);     \
    f_rn(bo, bi, 2, k);     \
    f_rn(bo, bi, 3, k);     \
    k += 4

#define f_lround(bo, bi, k) \
    f_rl(bo, bi, 0, k);     \
    f_rl(bo, bi, 1, k);     \
    f_rl(bo, bi, 2, k);     \
    f_rl(bo, bi, 3, k)

static void aes_encrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
      const struct aes_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *src = (const __le32 *)in;
      __le32 *dst = (__le32 *)out;
      u32 b0[4], b1[4];
      const u32 *kp = E_KEY + 4;

      b0[0] = le32_to_cpu(src[0]) ^ E_KEY[0];
      b0[1] = le32_to_cpu(src[1]) ^ E_KEY[1];
      b0[2] = le32_to_cpu(src[2]) ^ E_KEY[2];
      b0[3] = le32_to_cpu(src[3]) ^ E_KEY[3];

      if (ctx->key_length > 24) {
            f_nround (b1, b0, kp);
            f_nround (b0, b1, kp);
      }

      if (ctx->key_length > 16) {
            f_nround (b1, b0, kp);
            f_nround (b0, b1, kp);
      }

      f_nround (b1, b0, kp);
      f_nround (b0, b1, kp);
      f_nround (b1, b0, kp);
      f_nround (b0, b1, kp);
      f_nround (b1, b0, kp);
      f_nround (b0, b1, kp);
      f_nround (b1, b0, kp);
      f_nround (b0, b1, kp);
      f_nround (b1, b0, kp);
      f_lround (b0, b1, kp);

      dst[0] = cpu_to_le32(b0[0]);
      dst[1] = cpu_to_le32(b0[1]);
      dst[2] = cpu_to_le32(b0[2]);
      dst[3] = cpu_to_le32(b0[3]);
}

/* decrypt a block of text */

#define i_nround(bo, bi, k) \
    i_rn(bo, bi, 0, k);     \
    i_rn(bo, bi, 1, k);     \
    i_rn(bo, bi, 2, k);     \
    i_rn(bo, bi, 3, k);     \
    k -= 4

#define i_lround(bo, bi, k) \
    i_rl(bo, bi, 0, k);     \
    i_rl(bo, bi, 1, k);     \
    i_rl(bo, bi, 2, k);     \
    i_rl(bo, bi, 3, k)

static void aes_decrypt(struct crypto_tfm *tfm, u8 *out, const u8 *in)
{
      const struct aes_ctx *ctx = crypto_tfm_ctx(tfm);
      const __le32 *src = (const __le32 *)in;
      __le32 *dst = (__le32 *)out;
      u32 b0[4], b1[4];
      const int key_len = ctx->key_length;
      const u32 *kp = D_KEY + key_len + 20;

      b0[0] = le32_to_cpu(src[0]) ^ E_KEY[key_len + 24];
      b0[1] = le32_to_cpu(src[1]) ^ E_KEY[key_len + 25];
      b0[2] = le32_to_cpu(src[2]) ^ E_KEY[key_len + 26];
      b0[3] = le32_to_cpu(src[3]) ^ E_KEY[key_len + 27];

      if (key_len > 24) {
            i_nround (b1, b0, kp);
            i_nround (b0, b1, kp);
      }

      if (key_len > 16) {
            i_nround (b1, b0, kp);
            i_nround (b0, b1, kp);
      }

      i_nround (b1, b0, kp);
      i_nround (b0, b1, kp);
      i_nround (b1, b0, kp);
      i_nround (b0, b1, kp);
      i_nround (b1, b0, kp);
      i_nround (b0, b1, kp);
      i_nround (b1, b0, kp);
      i_nround (b0, b1, kp);
      i_nround (b1, b0, kp);
      i_lround (b0, b1, kp);

      dst[0] = cpu_to_le32(b0[0]);
      dst[1] = cpu_to_le32(b0[1]);
      dst[2] = cpu_to_le32(b0[2]);
      dst[3] = cpu_to_le32(b0[3]);
}


static struct crypto_alg aes_alg = {
      .cra_name         =     "aes",
      .cra_driver_name  =     "aes-generic",
      .cra_priority           =     100,
      .cra_flags        =     CRYPTO_ALG_TYPE_CIPHER,
      .cra_blocksize          =     AES_BLOCK_SIZE,
      .cra_ctxsize            =     sizeof(struct aes_ctx),
      .cra_alignmask          =     3,
      .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("Dual BSD/GPL");
MODULE_ALIAS("aes");

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