include/crypto/cbc.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * CBC: Cipher Block Chaining mode
   4  *
   5  * Copyright (c) 2016 Herbert Xu <herbert@gondor.apana.org.au>
   6  */
   7
   8 #ifndef _CRYPTO_CBC_H
   9 #define _CRYPTO_CBC_H
  10
  11 #include <crypto/internal/skcipher.h>
  12 #include <linux/string.h>
  13 #include <linux/types.h>
  14
  15 static inline int crypto_cbc_encrypt_segment(
  16         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
  17         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
  18 {
  19         unsigned int bsize = crypto_skcipher_blocksize(tfm);
  20         unsigned int nbytes = walk->nbytes;
  21         u8 *src = walk->src.virt.addr;
  22         u8 *dst = walk->dst.virt.addr;
  23         u8 *iv = walk->iv;
  24
  25         do {
  26                 crypto_xor(iv, src, bsize);
  27                 fn(tfm, iv, dst);
  28                 memcpy(iv, dst, bsize);
  29
  30                 src += bsize;
  31                 dst += bsize;
  32         } while ((nbytes -= bsize) >= bsize);
  33
  34         return nbytes;
  35 }
  36
  37 static inline int crypto_cbc_encrypt_inplace(
  38         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
  39         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
  40 {
  41         unsigned int bsize = crypto_skcipher_blocksize(tfm);
  42         unsigned int nbytes = walk->nbytes;
  43         u8 *src = walk->src.virt.addr;
  44         u8 *iv = walk->iv;
  45
  46         do {
  47                 crypto_xor(src, iv, bsize);
  48                 fn(tfm, src, src);
  49                 iv = src;
  50
  51                 src += bsize;
  52         } while ((nbytes -= bsize) >= bsize);
  53
  54         memcpy(walk->iv, iv, bsize);
  55
  56         return nbytes;
  57 }
  58
  59 static inline int crypto_cbc_encrypt_walk(struct skcipher_request *req,
  60                                           void (*fn)(struct crypto_skcipher *,
  61                                                      const u8 *, u8 *))
  62 {
  63         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  64         struct skcipher_walk walk;
  65         int err;
  66
  67         err = skcipher_walk_virt(&walk, req, false);
  68
  69         while (walk.nbytes) {
  70                 if (walk.src.virt.addr == walk.dst.virt.addr)
  71                         err = crypto_cbc_encrypt_inplace(&walk, tfm, fn);
  72                 else
  73                         err = crypto_cbc_encrypt_segment(&walk, tfm, fn);
  74                 err = skcipher_walk_done(&walk, err);
  75         }
  76
  77         return err;
  78 }
  79
  80 static inline int crypto_cbc_decrypt_segment(
  81         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
  82         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
  83 {
  84         unsigned int bsize = crypto_skcipher_blocksize(tfm);
  85         unsigned int nbytes = walk->nbytes;
  86         u8 *src = walk->src.virt.addr;
  87         u8 *dst = walk->dst.virt.addr;
  88         u8 *iv = walk->iv;
  89
  90         do {
  91                 fn(tfm, src, dst);
  92                 crypto_xor(dst, iv, bsize);
  93                 iv = src;
  94
  95                 src += bsize;
  96                 dst += bsize;
  97         } while ((nbytes -= bsize) >= bsize);
  98
  99         memcpy(walk->iv, iv, bsize);
 100
 101         return nbytes;
 102 }
 103
 104 static inline int crypto_cbc_decrypt_inplace(
 105         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 106         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 107 {
 108         unsigned int bsize = crypto_skcipher_blocksize(tfm);
 109         unsigned int nbytes = walk->nbytes;
 110         u8 *src = walk->src.virt.addr;
 111         u8 last_iv[MAX_CIPHER_BLOCKSIZE];
 112
 113         /* Start of the last block. */
 114         src += nbytes - (nbytes & (bsize - 1)) - bsize;
 115         memcpy(last_iv, src, bsize);
 116
 117         for (;;) {
 118                 fn(tfm, src, src);
 119                 if ((nbytes -= bsize) < bsize)
 120                         break;
 121                 crypto_xor(src, src - bsize, bsize);
 122                 src -= bsize;
 123         }
 124
 125         crypto_xor(src, walk->iv, bsize);
 126         memcpy(walk->iv, last_iv, bsize);
 127
 128         return nbytes;
 129 }
 130
 131 static inline int crypto_cbc_decrypt_blocks(
 132         struct skcipher_walk *walk, struct crypto_skcipher *tfm,
 133         void (*fn)(struct crypto_skcipher *, const u8 *, u8 *))
 134 {
 135         if (walk->src.virt.addr == walk->dst.virt.addr)
 136                 return crypto_cbc_decrypt_inplace(walk, tfm, fn);
 137         else
 138                 return crypto_cbc_decrypt_segment(walk, tfm, fn);
 139 }
 140
 141 #endif  /* _CRYPTO_CBC_H */