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 <linux/init.h>
  23 #include <linux/module.h>
  24 #include <linux/errno.h>
  25 #include <linux/crypto.h>
  26 #include <linux/types.h>
  27 #include <crypto/algapi.h>
  28 #include <asm/byteorder.h>
  29
  30 #define SALSA20_IV_SIZE        8U
  31 #define SALSA20_MIN_KEY_SIZE  16U
  32 #define SALSA20_MAX_KEY_SIZE  32U
  33
  34 /*
  35  * Start of code taken from D. J. Bernstein's reference implementation.
  36  * With some modifications and optimizations made to suit our needs.
  37  */
  38
  39 /*
  40 salsa20-ref.c version 20051118
  41 D. J. Bernstein
  42 Public domain.
  43 */
  44
  45 #define ROTATE(v,n) (((v) << (n)) | ((v) >> (32 - (n))))
  46 #define XOR(v,w) ((v) ^ (w))
  47 #define PLUS(v,w) (((v) + (w)))
  48 #define PLUSONE(v) (PLUS((v),1))
  49 #define U32TO8_LITTLE(p, v) \
  50         { (p)[0] = (v >>  0) & 0xff; (p)[1] = (v >>  8) & 0xff; \
  51           (p)[2] = (v >> 16) & 0xff; (p)[3] = (v >> 24) & 0xff; }
  52 #define U8TO32_LITTLE(p)   \
  53         (((u32)((p)[0])      ) | ((u32)((p)[1]) <<  8) | \
  54          ((u32)((p)[2]) << 16) | ((u32)((p)[3]) << 24)   )
  55
  56 struct salsa20_ctx
  57 {
  58         u32 input[16];
  59 };
  60
  61 static void salsa20_wordtobyte(u8 output[64], const u32 input[16])
  62 {
  63         u32 x[16];
  64         int i;
  65
  66         memcpy(x, input, sizeof(x));
  67         for (i = 20; i > 0; i -= 2) {
  68                 x[ 4] = XOR(x[ 4],ROTATE(PLUS(x[ 0],x[12]), 7));
  69                 x[ 8] = XOR(x[ 8],ROTATE(PLUS(x[ 4],x[ 0]), 9));
  70                 x[12] = XOR(x[12],ROTATE(PLUS(x[ 8],x[ 4]),13));
  71                 x[ 0] = XOR(x[ 0],ROTATE(PLUS(x[12],x[ 8]),18));
  72                 x[ 9] = XOR(x[ 9],ROTATE(PLUS(x[ 5],x[ 1]), 7));
  73                 x[13] = XOR(x[13],ROTATE(PLUS(x[ 9],x[ 5]), 9));
  74                 x[ 1] = XOR(x[ 1],ROTATE(PLUS(x[13],x[ 9]),13));
  75                 x[ 5] = XOR(x[ 5],ROTATE(PLUS(x[ 1],x[13]),18));
  76                 x[14] = XOR(x[14],ROTATE(PLUS(x[10],x[ 6]), 7));
  77                 x[ 2] = XOR(x[ 2],ROTATE(PLUS(x[14],x[10]), 9));
  78                 x[ 6] = XOR(x[ 6],ROTATE(PLUS(x[ 2],x[14]),13));
  79                 x[10] = XOR(x[10],ROTATE(PLUS(x[ 6],x[ 2]),18));
  80                 x[ 3] = XOR(x[ 3],ROTATE(PLUS(x[15],x[11]), 7));
  81                 x[ 7] = XOR(x[ 7],ROTATE(PLUS(x[ 3],x[15]), 9));
  82                 x[11] = XOR(x[11],ROTATE(PLUS(x[ 7],x[ 3]),13));
  83                 x[15] = XOR(x[15],ROTATE(PLUS(x[11],x[ 7]),18));
  84                 x[ 1] = XOR(x[ 1],ROTATE(PLUS(x[ 0],x[ 3]), 7));
  85                 x[ 2] = XOR(x[ 2],ROTATE(PLUS(x[ 1],x[ 0]), 9));
  86                 x[ 3] = XOR(x[ 3],ROTATE(PLUS(x[ 2],x[ 1]),13));
  87                 x[ 0] = XOR(x[ 0],ROTATE(PLUS(x[ 3],x[ 2]),18));
  88                 x[ 6] = XOR(x[ 6],ROTATE(PLUS(x[ 5],x[ 4]), 7));
  89                 x[ 7] = XOR(x[ 7],ROTATE(PLUS(x[ 6],x[ 5]), 9));
  90                 x[ 4] = XOR(x[ 4],ROTATE(PLUS(x[ 7],x[ 6]),13));
  91                 x[ 5] = XOR(x[ 5],ROTATE(PLUS(x[ 4],x[ 7]),18));
  92                 x[11] = XOR(x[11],ROTATE(PLUS(x[10],x[ 9]), 7));
  93                 x[ 8] = XOR(x[ 8],ROTATE(PLUS(x[11],x[10]), 9));
  94                 x[ 9] = XOR(x[ 9],ROTATE(PLUS(x[ 8],x[11]),13));
  95                 x[10] = XOR(x[10],ROTATE(PLUS(x[ 9],x[ 8]),18));
  96                 x[12] = XOR(x[12],ROTATE(PLUS(x[15],x[14]), 7));
  97                 x[13] = XOR(x[13],ROTATE(PLUS(x[12],x[15]), 9));
  98                 x[14] = XOR(x[14],ROTATE(PLUS(x[13],x[12]),13));
  99                 x[15] = XOR(x[15],ROTATE(PLUS(x[14],x[13]),18));
 100         }
 101         for (i = 0; i < 16; ++i)
 102                 x[i] = PLUS(x[i],input[i]);
 103         for (i = 0; i < 16; ++i)
 104                 U32TO8_LITTLE(output + 4 * i,x[i]);
 105 }
 106
 107 static const char sigma[16] = "expand 32-byte k";
 108 static const char tau[16] = "expand 16-byte k";
 109
 110 static void salsa20_keysetup(struct salsa20_ctx *ctx, const u8 *k, u32 kbytes)
 111 {
 112         const char *constants;
 113
 114         ctx->input[1] = U8TO32_LITTLE(k + 0);
 115         ctx->input[2] = U8TO32_LITTLE(k + 4);
 116         ctx->input[3] = U8TO32_LITTLE(k + 8);
 117         ctx->input[4] = U8TO32_LITTLE(k + 12);
 118         if (kbytes == 32) { /* recommended */
 119                 k += 16;
 120                 constants = sigma;
 121         } else { /* kbytes == 16 */
 122                 constants = tau;
 123         }
 124         ctx->input[11] = U8TO32_LITTLE(k + 0);
 125         ctx->input[12] = U8TO32_LITTLE(k + 4);
 126         ctx->input[13] = U8TO32_LITTLE(k + 8);
 127         ctx->input[14] = U8TO32_LITTLE(k + 12);
 128         ctx->input[0] = U8TO32_LITTLE(constants + 0);
 129         ctx->input[5] = U8TO32_LITTLE(constants + 4);
 130         ctx->input[10] = U8TO32_LITTLE(constants + 8);
 131         ctx->input[15] = U8TO32_LITTLE(constants + 12);
 132 }
 133
 134 static void salsa20_ivsetup(struct salsa20_ctx *ctx, const u8 *iv)
 135 {
 136         ctx->input[6] = U8TO32_LITTLE(iv + 0);
 137         ctx->input[7] = U8TO32_LITTLE(iv + 4);
 138         ctx->input[8] = 0;
 139         ctx->input[9] = 0;
 140 }
 141
 142 static void salsa20_encrypt_bytes(struct salsa20_ctx *ctx, u8 *dst,
 143                                   const u8 *src, unsigned int bytes)
 144 {
 145         u8 buf[64];
 146
 147         if (dst != src)
 148                 memcpy(dst, src, bytes);
 149
 150         while (bytes) {
 151                 salsa20_wordtobyte(buf, ctx->input);
 152
 153                 ctx->input[8] = PLUSONE(ctx->input[8]);
 154                 if (!ctx->input[8])
 155                         ctx->input[9] = PLUSONE(ctx->input[9]);
 156
 157                 if (bytes <= 64) {
 158                         crypto_xor(dst, buf, bytes);
 159                         return;
 160                 }
 161
 162                 crypto_xor(dst, buf, 64);
 163                 bytes -= 64;
 164                 dst += 64;
 165         }
 166 }
 167
 168 /*
 169  * End of code taken from D. J. Bernstein's reference implementation.
 170  */
 171
 172 static int setkey(struct crypto_tfm *tfm, const u8 *key,
 173                   unsigned int keysize)
 174 {
 175         struct salsa20_ctx *ctx = crypto_tfm_ctx(tfm);
 176         salsa20_keysetup(ctx, key, keysize);
 177         return 0;
 178 }
 179
 180 static int encrypt(struct blkcipher_desc *desc,
 181                    struct scatterlist *dst, struct scatterlist *src,
 182                    unsigned int nbytes)
 183 {
 184         struct blkcipher_walk walk;
 185         struct crypto_blkcipher *tfm = desc->tfm;
 186         struct salsa20_ctx *ctx = crypto_blkcipher_ctx(tfm);
 187         int err;
 188
 189         blkcipher_walk_init(&walk, dst, src, nbytes);
 190         err = blkcipher_walk_virt_block(desc, &walk, 64);
 191
 192         salsa20_ivsetup(ctx, walk.iv);
 193
 194         if (likely(walk.nbytes == nbytes))
 195         {
 196                 salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
 197                                       walk.src.virt.addr, nbytes);
 198                 return blkcipher_walk_done(desc, &walk, 0);
 199         }
 200
 201         while (walk.nbytes >= 64) {
 202                 salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
 203                                       walk.src.virt.addr,
 204                                       walk.nbytes - (walk.nbytes % 64));
 205                 err = blkcipher_walk_done(desc, &walk, walk.nbytes % 64);
 206         }
 207
 208         if (walk.nbytes) {
 209                 salsa20_encrypt_bytes(ctx, walk.dst.virt.addr,
 210                                       walk.src.virt.addr, walk.nbytes);
 211                 err = blkcipher_walk_done(desc, &walk, 0);
 212         }
 213
 214         return err;
 215 }
 216
 217 static struct crypto_alg alg = {
 218         .cra_name           =   "salsa20",
 219         .cra_driver_name    =   "salsa20-generic",
 220         .cra_priority       =   100,
 221         .cra_flags          =   CRYPTO_ALG_TYPE_BLKCIPHER,
 222         .cra_type           =   &crypto_blkcipher_type,
 223         .cra_blocksize      =   1,
 224         .cra_ctxsize        =   sizeof(struct salsa20_ctx),
 225         .cra_alignmask      =   3,
 226         .cra_module         =   THIS_MODULE,
 227         .cra_list           =   LIST_HEAD_INIT(alg.cra_list),
 228         .cra_u              =   {
 229                 .blkcipher = {
 230                         .setkey         =   setkey,
 231                         .encrypt        =   encrypt,
 232                         .decrypt        =   encrypt,
 233                         .min_keysize    =   SALSA20_MIN_KEY_SIZE,
 234                         .max_keysize    =   SALSA20_MAX_KEY_SIZE,
 235                         .ivsize         =   SALSA20_IV_SIZE,
 236                 }
 237         }
 238 };
 239
 240 static int __init salsa20_generic_mod_init(void)
 241 {
 242         return crypto_register_alg(&alg);
 243 }
 244
 245 static void __exit salsa20_generic_mod_fini(void)
 246 {
 247         crypto_unregister_alg(&alg);
 248 }
 249
 250 module_init(salsa20_generic_mod_init);
 251 module_exit(salsa20_generic_mod_fini);
 252
 253 MODULE_LICENSE("GPL");
 254 MODULE_DESCRIPTION ("Salsa20 stream cipher algorithm");
 255 MODULE_ALIAS("salsa20");