git.sesse.net Git - bcachefs-tools-debian/blob - c_src/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 <linux/byteorder.h>
  13 #include <linux/errno.h>
  14 #include <linux/kernel.h>
  15 #include <linux/scatterlist.h>
  16 #include <asm/unaligned.h>
  17
  18 #include <linux/crypto.h>
  19 #include <crypto/algapi.h>
  20 #include <crypto/chacha.h>
  21 #include <crypto/skcipher.h>
  22
  23 #include <sodium/crypto_stream_chacha20.h>
  24
  25 static struct skcipher_alg alg;
  26
  27 struct chacha20_tfm {
  28         struct crypto_skcipher  tfm;
  29         u32                     key[8];
  30 };
  31
  32 static int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
  33                                   unsigned int keysize)
  34 {
  35         struct chacha20_tfm *ctx =
  36                 container_of(tfm, struct chacha20_tfm, tfm);
  37         int i;
  38
  39         if (keysize != CHACHA_KEY_SIZE)
  40                 return -EINVAL;
  41
  42         for (i = 0; i < ARRAY_SIZE(ctx->key); i++)
  43                 ctx->key[i] = get_unaligned_le32(key + i * sizeof(u32));
  44
  45         return 0;
  46 }
  47
  48 static int crypto_chacha20_crypt(struct skcipher_request *req)
  49 {
  50         struct chacha20_tfm *ctx =
  51                 container_of(req->tfm, struct chacha20_tfm, tfm.base);
  52         struct scatterlist *sg = req->src;
  53         unsigned nbytes = req->cryptlen;
  54         u32 iv[4];
  55         int ret;
  56
  57         BUG_ON(req->src != req->dst);
  58
  59         memcpy(iv, req->iv, sizeof(iv));
  60
  61         while (1) {
  62                 ret = crypto_stream_chacha20_xor_ic(sg_virt(sg),
  63                                                     sg_virt(sg),
  64                                                     sg->length,
  65                                                     (void *) &iv[2],
  66                                                     iv[0] | ((u64) iv[1] << 32),
  67                                                     (void *) ctx->key);
  68                 BUG_ON(ret);
  69
  70                 nbytes -= sg->length;
  71
  72                 if (sg_is_last(sg))
  73                         break;
  74
  75                 BUG_ON(sg->length % CHACHA_BLOCK_SIZE);
  76                 iv[0] += sg->length / CHACHA_BLOCK_SIZE;
  77                 sg = sg_next(sg);
  78         };
  79
  80         BUG_ON(nbytes);
  81
  82         return 0;
  83 }
  84
  85 static void *crypto_chacha20_alloc_tfm(void)
  86 {
  87         struct chacha20_tfm *tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
  88
  89         if (!tfm)
  90                 return NULL;
  91
  92         tfm->tfm.base.alg       = &alg.base;
  93         tfm->tfm.setkey         = crypto_chacha20_setkey;
  94         tfm->tfm.encrypt        = crypto_chacha20_crypt;
  95         tfm->tfm.decrypt        = crypto_chacha20_crypt;
  96         tfm->tfm.ivsize         = CHACHA_IV_SIZE;
  97         tfm->tfm.keysize        = CHACHA_KEY_SIZE;
  98
  99         return tfm;
 100 }
 101
 102 static struct skcipher_alg alg = {
 103         .base.cra_name          = "chacha20",
 104         .base.alloc_tfm         = crypto_chacha20_alloc_tfm,
 105 };
 106
 107 __attribute__((constructor(110)))
 108 static int chacha20_generic_mod_init(void)
 109 {
 110         return crypto_register_skcipher(&alg);
 111 }