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Linux/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");
152 

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