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 le32_to_cpuvp(const void *p)
  19 {
  20         return le32_to_cpup(p);
  21 }
  22
  23 static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
  24                              unsigned int bytes)
  25 {
  26         /* aligned to potentially speed up crypto_xor() */
  27         u8 stream[CHACHA20_BLOCK_SIZE] __aligned(sizeof(long));
  28
  29         if (dst != src)
  30                 memcpy(dst, src, bytes);
  31
  32         while (bytes >= CHACHA20_BLOCK_SIZE) {
  33                 chacha20_block(state, stream);
  34                 crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE);
  35                 bytes -= CHACHA20_BLOCK_SIZE;
  36                 dst += CHACHA20_BLOCK_SIZE;
  37         }
  38         if (bytes) {
  39                 chacha20_block(state, stream);
  40                 crypto_xor(dst, stream, bytes);
  41         }
  42 }
  43
  44 void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv)
  45 {
  46         static const char constant[16] = "expand 32-byte k";
  47
  48         state[0]  = le32_to_cpuvp(constant +  0);
  49         state[1]  = le32_to_cpuvp(constant +  4);
  50         state[2]  = le32_to_cpuvp(constant +  8);
  51         state[3]  = le32_to_cpuvp(constant + 12);
  52         state[4]  = ctx->key[0];
  53         state[5]  = ctx->key[1];
  54         state[6]  = ctx->key[2];
  55         state[7]  = ctx->key[3];
  56         state[8]  = ctx->key[4];
  57         state[9]  = ctx->key[5];
  58         state[10] = ctx->key[6];
  59         state[11] = ctx->key[7];
  60         state[12] = le32_to_cpuvp(iv +  0);
  61         state[13] = le32_to_cpuvp(iv +  4);
  62         state[14] = le32_to_cpuvp(iv +  8);
  63         state[15] = le32_to_cpuvp(iv + 12);
  64 }
  65 EXPORT_SYMBOL_GPL(crypto_chacha20_init);
  66
  67 int crypto_chacha20_setkey(struct crypto_tfm *tfm, const u8 *key,
  68                            unsigned int keysize)
  69 {
  70         struct chacha20_ctx *ctx = crypto_tfm_ctx(tfm);
  71         int i;
  72
  73         if (keysize != CHACHA20_KEY_SIZE)
  74                 return -EINVAL;
  75
  76         for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
  77                 ctx->key[i] = le32_to_cpuvp(key + i * sizeof(u32));
  78
  79         return 0;
  80 }
  81 EXPORT_SYMBOL_GPL(crypto_chacha20_setkey);
  82
  83 int crypto_chacha20_crypt(struct blkcipher_desc *desc, struct scatterlist *dst,
  84                           struct scatterlist *src, unsigned int nbytes)
  85 {
  86         struct blkcipher_walk walk;
  87         u32 state[16];
  88         int err;
  89
  90         blkcipher_walk_init(&walk, dst, src, nbytes);
  91         err = blkcipher_walk_virt_block(desc, &walk, CHACHA20_BLOCK_SIZE);
  92
  93         crypto_chacha20_init(state, crypto_blkcipher_ctx(desc->tfm), walk.iv);
  94
  95         while (walk.nbytes >= CHACHA20_BLOCK_SIZE) {
  96                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
  97                                  rounddown(walk.nbytes, CHACHA20_BLOCK_SIZE));
  98                 err = blkcipher_walk_done(desc, &walk,
  99                                           walk.nbytes % CHACHA20_BLOCK_SIZE);
 100         }
 101
 102         if (walk.nbytes) {
 103                 chacha20_docrypt(state, walk.dst.virt.addr, walk.src.virt.addr,
 104                                  walk.nbytes);
 105                 err = blkcipher_walk_done(desc, &walk, 0);
 106         }
 107
 108         return err;
 109 }
 110 EXPORT_SYMBOL_GPL(crypto_chacha20_crypt);
 111
 112 static struct crypto_alg alg = {
 113         .cra_name               = "chacha20",
 114         .cra_driver_name        = "chacha20-generic",
 115         .cra_priority           = 100,
 116         .cra_flags              = CRYPTO_ALG_TYPE_BLKCIPHER,
 117         .cra_blocksize          = 1,
 118         .cra_type               = &crypto_blkcipher_type,
 119         .cra_ctxsize            = sizeof(struct chacha20_ctx),
 120         .cra_alignmask          = sizeof(u32) - 1,
 121         .cra_module             = THIS_MODULE,
 122         .cra_u                  = {
 123                 .blkcipher = {
 124                         .min_keysize    = CHACHA20_KEY_SIZE,
 125                         .max_keysize    = CHACHA20_KEY_SIZE,
 126                         .ivsize         = CHACHA20_IV_SIZE,
 127                         .geniv          = "seqiv",
 128                         .setkey         = crypto_chacha20_setkey,
 129                         .encrypt        = crypto_chacha20_crypt,
 130                         .decrypt        = crypto_chacha20_crypt,
 131                 },
 132         },
 133 };
 134
 135 static int __init chacha20_generic_mod_init(void)
 136 {
 137         return crypto_register_alg(&alg);
 138 }
 139
 140 static void __exit chacha20_generic_mod_fini(void)
 141 {
 142         crypto_unregister_alg(&alg);
 143 }
 144
 145 module_init(chacha20_generic_mod_init);
 146 module_exit(chacha20_generic_mod_fini);
 147
 148 MODULE_LICENSE("GPL");
 149 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
 150 MODULE_DESCRIPTION("chacha20 cipher algorithm");
 151 MODULE_ALIAS_CRYPTO("chacha20");
 152 MODULE_ALIAS_CRYPTO("chacha20-generic");