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