include/crypto/cbc.h

   1 /*
   2  * CBC: Cipher Block Chaining mode
   3  *
   4  * Copyright (c) 2016 Herbert Xu <herbert@gondor.apana.org.au>
   5  *
   6  * This program is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU General Public License as published by the Free
   8  * Software Foundation; either version 2 of the License, or (at your option)
   9  * any later version.
  10  *
  11  */
  12
  13 #ifndef _CRYPTO_CBC_H
  14 #define _CRYPTO_CBC_H
  15
  16 #include <crypto/internal/skcipher.h>
  17 #include <linux/string.h>
  18 #include <linux/types.h>
  19
  20 static inline int crypto_cbc_encrypt_segment(
  21         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
  22         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
  23 {
  24         unsigned int bsize = crypto_skcipher_blocksize(tfm);
  25         unsigned int nbytes = walk->nbytes;
  26         u8 *src = walk->src.virt.addr;
  27         u8 *dst = walk->dst.virt.addr;
  28         u8 *iv = walk->iv;
  29
  30         do {
  31                 crypto_xor(iv, src, bsize);
  32                 fn(tfm, iv, dst);
  33                 memcpy(iv, dst, bsize);
  34
  35                 src += bsize;
  36                 dst += bsize;
  37         } while ((nbytes -= bsize) >= bsize);
  38
  39         return nbytes;
  40 }
  41
  42 static inline int crypto_cbc_encrypt_inplace(
  43         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
  44         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
  45 {
  46         unsigned int bsize = crypto_skcipher_blocksize(tfm);
  47         unsigned int nbytes = walk->nbytes;
  48         u8 *src = walk->src.virt.addr;
  49         u8 *iv = walk->iv;
  50
  51         do {
  52                 crypto_xor(src, iv, bsize);
  53                 fn(tfm, src, src);
  54                 iv = src;
  55
  56                 src += bsize;
  57         } while ((nbytes -= bsize) >= bsize);
  58
  59         memcpy(walk->iv, iv, bsize);
  60
  61         return nbytes;
  62 }
  63
  64 static inline int crypto_cbc_encrypt_walk(struct skcipher_request *req,
  65                                           void (*fn)(struct crypto_skcipher *,
  66                                                      const u8 *, u8 *))
  67 {
  68         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  69         struct skcipher_walk walk;
  70         int err;
  71
  72         err = skcipher_walk_virt(&walk, req, false);
  73
  74         while (walk.nbytes) {
  75                 if (walk.src.virt.addr == walk.dst.virt.addr)
  76                         err = crypto_cbc_encrypt_inplace(&walk, tfm, fn);
  77                 else
  78                         err = crypto_cbc_encrypt_segment(&walk, tfm, fn);
  79                 err = skcipher_walk_done(&walk, err);
  80         }
  81
  82         return err;
  83 }
  84
  85 static inline int crypto_cbc_decrypt_segment(
  86         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
  87         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
  88 {
  89         unsigned int bsize = crypto_skcipher_blocksize(tfm);
  90         unsigned int nbytes = walk->nbytes;
  91         u8 *src = walk->src.virt.addr;
  92         u8 *dst = walk->dst.virt.addr;
  93         u8 *iv = walk->iv;
  94
  95         do {
  96                 fn(tfm, src, dst);
  97                 crypto_xor(dst, iv, bsize);
  98                 iv = src;
  99
 100                 src += bsize;
 101                 dst += bsize;
 102         } while ((nbytes -= bsize) >= bsize);
 103
 104         memcpy(walk->iv, iv, bsize);
 105
 106         return nbytes;
 107 }
 108
 109 static inline int crypto_cbc_decrypt_inplace(
 110         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 111         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 112 {
 113         unsigned int bsize = crypto_skcipher_blocksize(tfm);
 114         unsigned int nbytes = walk->nbytes;
 115         u8 *src = walk->src.virt.addr;
 116         u8 last_iv[bsize];
 117
 118         /* Start of the last block. */
 119         src += nbytes - (nbytes & (bsize - 1)) - bsize;
 120         memcpy(last_iv, src, bsize);
 121
 122         for (;;) {
 123                 fn(tfm, src, src);
 124                 if ((nbytes -= bsize) < bsize)
 125                         break;
 126                 crypto_xor(src, src - bsize, bsize);
 127                 src -= bsize;
 128         }
 129
 130         crypto_xor(src, walk->iv, bsize);
 131         memcpy(walk->iv, last_iv, bsize);
 132
 133         return nbytes;
 134 }
 135
 136 static inline int crypto_cbc_decrypt_blocks(
 137         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 138         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 139 {
 140         if (walk->src.virt.addr == walk->dst.virt.addr)
 141                 return crypto_cbc_decrypt_inplace(walk, tfm, fn);
 142         else
 143                 return crypto_cbc_decrypt_segment(walk, tfm, fn);
 144 }
 145
 146 #endif  /* _CRYPTO_CBC_H */