crypto/salsa20_generic.c

   1 /*
   2  * Salsa20: Salsa20 stream cipher algorithm
   3  *
   4  * Copyright (c) 2007 Tan Swee Heng <thesweeheng@gmail.com>
   5  *
   6  * Derived from:
   7  * - salsa20.c: Public domain C code by Daniel J. Bernstein <djb@cr.yp.to>
   8  *
   9  * Salsa20 is a stream cipher candidate in eSTREAM, the ECRYPT Stream
  10  * Cipher Project. It is designed by Daniel J. Bernstein <djb@cr.yp.to>.
  11  * More information about eSTREAM and Salsa20 can be found here:
  12  *   http://www.ecrypt.eu.org/stream/
  13  *   http://cr.yp.to/snuffle.html
  14  *
  15  * This program is free software; you can redistribute it and/or modify it
  16  * under the terms of the GNU General Public License as published by the Free
  17  * Software Foundation; either version 2 of the License, or (at your option)
  18  * any later version.
  19  *
  20  */
  21
  22 #include <asm/unaligned.h>
  23 #include <crypto/internal/skcipher.h>
  24 #include <crypto/salsa20.h>
  25 #include <linux/module.h>
  26
  27 static void salsa20_block(u32 *state, __le32 *stream)
  28 {
  29         u32 x[16];
  30         int i;
  31
  32         memcpy(x, state, sizeof(x));
  33
  34         for (i = 0; i < 20; i += 2) {
  35                 x[ 4] ^= rol32((x[ 0] + x[12]),  7);
  36                 x[ 8] ^= rol32((x[ 4] + x[ 0]),  9);
  37                 x[12] ^= rol32((x[ 8] + x[ 4]), 13);
  38                 x[ 0] ^= rol32((x[12] + x[ 8]), 18);
  39                 x[ 9] ^= rol32((x[ 5] + x[ 1]),  7);
  40                 x[13] ^= rol32((x[ 9] + x[ 5]),  9);
  41                 x[ 1] ^= rol32((x[13] + x[ 9]), 13);
  42                 x[ 5] ^= rol32((x[ 1] + x[13]), 18);
  43                 x[14] ^= rol32((x[10] + x[ 6]),  7);
  44                 x[ 2] ^= rol32((x[14] + x[10]),  9);
  45                 x[ 6] ^= rol32((x[ 2] + x[14]), 13);
  46                 x[10] ^= rol32((x[ 6] + x[ 2]), 18);
  47                 x[ 3] ^= rol32((x[15] + x[11]),  7);
  48                 x[ 7] ^= rol32((x[ 3] + x[15]),  9);
  49                 x[11] ^= rol32((x[ 7] + x[ 3]), 13);
  50                 x[15] ^= rol32((x[11] + x[ 7]), 18);
  51                 x[ 1] ^= rol32((x[ 0] + x[ 3]),  7);
  52                 x[ 2] ^= rol32((x[ 1] + x[ 0]),  9);
  53                 x[ 3] ^= rol32((x[ 2] + x[ 1]), 13);
  54                 x[ 0] ^= rol32((x[ 3] + x[ 2]), 18);
  55                 x[ 6] ^= rol32((x[ 5] + x[ 4]),  7);
  56                 x[ 7] ^= rol32((x[ 6] + x[ 5]),  9);
  57                 x[ 4] ^= rol32((x[ 7] + x[ 6]), 13);
  58                 x[ 5] ^= rol32((x[ 4] + x[ 7]), 18);
  59                 x[11] ^= rol32((x[10] + x[ 9]),  7);
  60                 x[ 8] ^= rol32((x[11] + x[10]),  9);
  61                 x[ 9] ^= rol32((x[ 8] + x[11]), 13);
  62                 x[10] ^= rol32((x[ 9] + x[ 8]), 18);
  63                 x[12] ^= rol32((x[15] + x[14]),  7);
  64                 x[13] ^= rol32((x[12] + x[15]),  9);
  65                 x[14] ^= rol32((x[13] + x[12]), 13);
  66                 x[15] ^= rol32((x[14] + x[13]), 18);
  67         }
  68
  69         for (i = 0; i < 16; i++)
  70                 stream[i] = cpu_to_le32(x[i] + state[i]);
  71
  72         if (++state[8] == 0)
  73                 state[9]++;
  74 }
  75
  76 static void salsa20_docrypt(u32 *state, u8 *dst, const u8 *src,
  77                             unsigned int bytes)
  78 {
  79         __le32 stream[SALSA20_BLOCK_SIZE / sizeof(__le32)];
  80
  81         if (dst != src)
  82                 memcpy(dst, src, bytes);
  83
  84         while (bytes >= SALSA20_BLOCK_SIZE) {
  85                 salsa20_block(state, stream);
  86                 crypto_xor(dst, (const u8 *)stream, SALSA20_BLOCK_SIZE);
  87                 bytes -= SALSA20_BLOCK_SIZE;
  88                 dst += SALSA20_BLOCK_SIZE;
  89         }
  90         if (bytes) {
  91                 salsa20_block(state, stream);
  92                 crypto_xor(dst, (const u8 *)stream, bytes);
  93         }
  94 }
  95
  96 void crypto_salsa20_init(u32 *state, const struct salsa20_ctx *ctx,
  97                          const u8 *iv)
  98 {
  99         memcpy(state, ctx->initial_state, sizeof(ctx->initial_state));
 100         state[6] = get_unaligned_le32(iv + 0);
 101         state[7] = get_unaligned_le32(iv + 4);
 102 }
 103 EXPORT_SYMBOL_GPL(crypto_salsa20_init);
 104
 105 int crypto_salsa20_setkey(struct crypto_skcipher *tfm, const u8 *key,
 106                           unsigned int keysize)
 107 {
 108         static const char sigma[16] = "expand 32-byte k";
 109         static const char tau[16] = "expand 16-byte k";
 110         struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
 111         const char *constants;
 112
 113         if (keysize != SALSA20_MIN_KEY_SIZE &&
 114             keysize != SALSA20_MAX_KEY_SIZE)
 115                 return -EINVAL;
 116
 117         ctx->initial_state[1] = get_unaligned_le32(key + 0);
 118         ctx->initial_state[2] = get_unaligned_le32(key + 4);
 119         ctx->initial_state[3] = get_unaligned_le32(key + 8);
 120         ctx->initial_state[4] = get_unaligned_le32(key + 12);
 121         if (keysize == 32) { /* recommended */
 122                 key += 16;
 123                 constants = sigma;
 124         } else { /* keysize == 16 */
 125                 constants = tau;
 126         }
 127         ctx->initial_state[11] = get_unaligned_le32(key + 0);
 128         ctx->initial_state[12] = get_unaligned_le32(key + 4);
 129         ctx->initial_state[13] = get_unaligned_le32(key + 8);
 130         ctx->initial_state[14] = get_unaligned_le32(key + 12);
 131         ctx->initial_state[0]  = get_unaligned_le32(constants + 0);
 132         ctx->initial_state[5]  = get_unaligned_le32(constants + 4);
 133         ctx->initial_state[10] = get_unaligned_le32(constants + 8);
 134         ctx->initial_state[15] = get_unaligned_le32(constants + 12);
 135
 136         /* space for the nonce; it will be overridden for each request */
 137         ctx->initial_state[6] = 0;
 138         ctx->initial_state[7] = 0;
 139
 140         /* initial block number */
 141         ctx->initial_state[8] = 0;
 142         ctx->initial_state[9] = 0;
 143
 144         return 0;
 145 }
 146 EXPORT_SYMBOL_GPL(crypto_salsa20_setkey);
 147
 148 static int salsa20_crypt(struct skcipher_request *req)
 149 {
 150         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 151         const struct salsa20_ctx *ctx = crypto_skcipher_ctx(tfm);
 152         struct skcipher_walk walk;
 153         u32 state[16];
 154         int err;
 155
 156         err = skcipher_walk_virt(&walk, req, true);
 157
 158         crypto_salsa20_init(state, ctx, walk.iv);
 159
 160         while (walk.nbytes > 0) {
 161                 unsigned int nbytes = walk.nbytes;
 162
 163                 if (nbytes < walk.total)
 164                         nbytes = round_down(nbytes, walk.stride);
 165
 166                 salsa20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
 167                                 nbytes);
 168                 err = skcipher_walk_done(&walk, walk.nbytes - nbytes);
 169         }
 170
 171         return err;
 172 }
 173
 174 static struct skcipher_alg alg = {
 175         .base.cra_name          = "salsa20",
 176         .base.cra_driver_name   = "salsa20-generic",
 177         .base.cra_priority      = 100,
 178         .base.cra_blocksize     = 1,
 179         .base.cra_ctxsize       = sizeof(struct salsa20_ctx),
 180         .base.cra_module        = THIS_MODULE,
 181
 182         .min_keysize            = SALSA20_MIN_KEY_SIZE,
 183         .max_keysize            = SALSA20_MAX_KEY_SIZE,
 184         .ivsize                 = SALSA20_IV_SIZE,
 185         .chunksize              = SALSA20_BLOCK_SIZE,
 186         .setkey                 = crypto_salsa20_setkey,
 187         .encrypt                = salsa20_crypt,
 188         .decrypt                = salsa20_crypt,
 189 };
 190
 191 static int __init salsa20_generic_mod_init(void)
 192 {
 193         return crypto_register_skcipher(&alg);
 194 }
 195
 196 static void __exit salsa20_generic_mod_fini(void)
 197 {
 198         crypto_unregister_skcipher(&alg);
 199 }
 200
 201 module_init(salsa20_generic_mod_init);
 202 module_exit(salsa20_generic_mod_fini);
 203
 204 MODULE_LICENSE("GPL");
 205 MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
 206 MODULE_ALIAS_CRYPTO("salsa20");
 207 MODULE_ALIAS_CRYPTO("salsa20-generic");