crypto/chacha20_generic.c

   1 /*
   2  * ChaCha20 256-bit cipher algorithm, RFC7539
   3  *
   4  * Copyright (C) 2015 Martin Willi
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  */
  11
  12 #include <crypto/algapi.h>
  13 #include <linux/crypto.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <crypto/chacha20.h>
  17
  18 static inline u32 rotl32(u32 v, u8 n)
  19 {
  20         return (v << n) | (v >> (sizeof(v) * 8 - n));
  21 }
  22
  23 static inline u32 le32_to_cpuvp(const void *p)
  24 {
  25         return le32_to_cpup(p);
  26 }
  27
  28 static void chacha20_block(u32 *state, void *stream)
  29 {
  30         u32 x[16], *out = stream;
  31         int i;
  32
  33         for (i = 0; i < ARRAY_SIZE(x); i++)
  34                 x[i] = state[i];
  35
  36         for (i = 0; i < 20; i += 2) {
  37                 x[0]  += x[4];    x[12] = rotl32(x[12] ^ x[0],  16);
  38                 x[1]  += x[5];    x[13] = rotl32(x[13] ^ x[1],  16);
  39                 x[2]  += x[6];    x[14] = rotl32(x[14] ^ x[2],  16);
  40                 x[3]  += x[7];    x[15] = rotl32(x[15] ^ x[3],  16);
  41
  42                 x[8]  += x[12];   x[4]  = rotl32(x[4]  ^ x[8],  12);
  43                 x[9]  += x[13];   x[5]  = rotl32(x[5]  ^ x[9],  12);
  44                 x[10] += x[14];   x[6]  = rotl32(x[6]  ^ x[10], 12);
  45                 x[11] += x[15];   x[7]  = rotl32(x[7]  ^ x[11], 12);
  46
  47                 x[0]  += x[4];    x[12] = rotl32(x[12] ^ x[0],   8);
  48                 x[1]  += x[5];    x[13] = rotl32(x[13] ^ x[1],   8);
  49                 x[2]  += x[6];    x[14] = rotl32(x[14] ^ x[2],   8);
  50                 x[3]  += x[7];    x[15] = rotl32(x[15] ^ x[3],   8);
  51
  52                 x[8]  += x[12];   x[4]  = rotl32(x[4]  ^ x[8],   7);
  53                 x[9]  += x[13];   x[5]  = rotl32(x[5]  ^ x[9],   7);
  54                 x[10] += x[14];   x[6]  = rotl32(x[6]  ^ x[10],  7);
  55                 x[11] += x[15];   x[7]  = rotl32(x[7]  ^ x[11],  7);
  56
  57                 x[0]  += x[5];    x[15] = rotl32(x[15] ^ x[0],  16);
  58                 x[1]  += x[6];    x[12] = rotl32(x[12] ^ x[1],  16);
  59                 x[2]  += x[7];    x[13] = rotl32(x[13] ^ x[2],  16);
  60                 x[3]  += x[4];    x[14] = rotl32(x[14] ^ x[3],  16);
  61
  62                 x[10] += x[15];   x[5]  = rotl32(x[5]  ^ x[10], 12);
  63                 x[11] += x[12];   x[6]  = rotl32(x[6]  ^ x[11], 12);
  64                 x[8]  += x[13];   x[7]  = rotl32(x[7]  ^ x[8],  12);
  65                 x[9]  += x[14];   x[4]  = rotl32(x[4]  ^ x[9],  12);
  66
  67                 x[0]  += x[5];    x[15] = rotl32(x[15] ^ x[0],   8);
  68                 x[1]  += x[6];    x[12] = rotl32(x[12] ^ x[1],   8);
  69                 x[2]  += x[7];    x[13] = rotl32(x[13] ^ x[2],   8);
  70                 x[3]  += x[4];    x[14] = rotl32(x[14] ^ x[3],   8);
  71
  72                 x[10] += x[15];   x[5]  = rotl32(x[5]  ^ x[10],  7);
  73                 x[11] += x[12];   x[6]  = rotl32(x[6]  ^ x[11],  7);
  74                 x[8]  += x[13];   x[7]  = rotl32(x[7]  ^ x[8],   7);
  75                 x[9]  += x[14];   x[4]  = rotl32(x[4]  ^ x[9],   7);
  76         }
  77
  78         for (i = 0; i < ARRAY_SIZE(x); i++)
  79                 out[i] = cpu_to_le32(x[i] + state[i]);
  80
  81         state[12]++;
  82 }
  83
  84 static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
  85                              unsigned int bytes)
  86 {
  87         u8 stream[CHACHA20_BLOCK_SIZE];
  88
  89         if (dst != src)
  90                 memcpy(dst, src, bytes);
  91
  92         while (bytes >= CHACHA20_BLOCK_SIZE) {
  93                 chacha20_block(state, stream);
  94                 crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
  95                 bytes -= CHACHA20_BLOCK_SIZE;
  96                 dst += CHACHA20_BLOCK_SIZE;
  97         }
  98         if (bytes) {
  99                 chacha20_block(state, stream);
 100                 crypto_xor(dst, stream, bytes);
 101         }
 102 }
 103
 104 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
 105 {
 106         static const char constant[16] = "expand 32-byte k";
 107
 108         state[0]  = le32_to_cpuvp(constant +  0);
 109         state[1]  = le32_to_cpuvp(constant +  4);
 110         state[2]  = le32_to_cpuvp(constant +  8);
 111         state[3]  = le32_to_cpuvp(constant + 12);
 112         state[4]  = ctx->key[0];
 113         state[5]  = ctx->key[1];
 114         state[6]  = ctx->key[2];
 115         state[7]  = ctx->key[3];
 116         state[8]  = ctx->key[4];
 117         state[9]  = ctx->key[5];
 118         state[10] = ctx->key[6];
 119         state[11] = ctx->key[7];
 120         state[12] = le32_to_cpuvp(iv +  0);
 121         state[13] = le32_to_cpuvp(iv +  4);
 122         state[14] = le32_to_cpuvp(iv +  8);
 123         state[15] = le32_to_cpuvp(iv + 12);
 124 }
 125 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
 126
 127 int crypto_chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
 128                            unsigned int keysize)
 129 {
 130         struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
 131         int i;
 132
 133         if (keysize != CHACHA20_KEY_SIZE)
 134                 return -EINVAL;
 135
 136         for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
 137                 ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
 138
 139         return 0;
 140 }
 141 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
 142
 143 int crypto_chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
 144                           struct scatterlist *src, unsigned int nbytes)
 145 {
 146         struct blkcipher_walk walk;
 147         u32 state[16];
 148         int err;
 149
 150         blkcipher_walk_init(&walk, dst, src, nbytes);
 151         err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
 152
 153         crypto_chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
 154
 155         while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
 156                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
 157                                  rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
 158                 err = blkcipher_walk_done(desc, &walk,
 159                                           walk.nbytes % CHACHA20_BLOCK_SIZE);
 160         }
 161
 162         if (walk.nbytes) {
 163                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
 164                                  walk.nbytes);
 165                 err = blkcipher_walk_done(desc, &walk, 0);
 166         }
 167
 168         return err;
 169 }
 170 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
 171
 172 static struct crypto_alg alg = {
 173         .cra_name               = "chacha20",
 174         .cra_driver_name        = "chacha20-generic",
 175         .cra_priority           = 100,
 176         .cra_flags              = CRYPTO_ALG_TYPE_BLKCIPHER,
 177         .cra_blocksize          = 1,
 178         .cra_type               = &crypto_blkcipher_type,
 179         .cra_ctxsize            = sizeof(struct chacha20_ctx),
 180         .cra_alignmask          = sizeof(u32) - 1,
 181         .cra_module             = THIS_MODULE,
 182         .cra_u                  = {
 183                 .blkcipher = {
 184                         .min_keysize    = CHACHA20_KEY_SIZE,
 185                         .max_keysize    = CHACHA20_KEY_SIZE,
 186                         .ivsize         = CHACHA20_IV_SIZE,
 187                         .geniv          = "seqiv",
 188                         .setkey         = crypto_chacha20_setkey,
 189                         .encrypt        = crypto_chacha20_crypt,
 190                         .decrypt        = crypto_chacha20_crypt,
 191                 },
 192         },
 193 };
 194
 195 static int __init chacha20_generic_mod_init(void)
 196 {
 197         return crypto_register_alg(&alg);
 198 }
 199
 200 static void __exit chacha20_generic_mod_fini(void)
 201 {
 202         crypto_unregister_alg(&alg);
 203 }
 204
 205 module_init(chacha20_generic_mod_init);
 206 module_exit(chacha20_generic_mod_fini);
 207
 208 MODULE_LICENSE("GPL");
 209 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 210 MODULE_DESCRIPTION("chacha20 cipher algorithm");
 211 MODULE_ALIAS_CRYPTO("chacha20");
 212 MODULE_ALIAS_CRYPTO("chacha20-generic");