include/crypto/ctr.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /*
   3  * CTR: Counter mode
   4  *
   5  * Copyright (c) 2007 Herbert Xu <herbert@gondor.apana.org.au>
   6  */
   7
   8 #ifndef _CRYPTO_CTR_H
   9 #define _CRYPTO_CTR_H
  10
  11 #include <crypto/algapi.h>
  12 #include <crypto/internal/skcipher.h>
  13 #include <linux/string.h>
  14 #include <linux/types.h>
  15
  16 #define CTR_RFC3686_NONCE_SIZE 4
  17 #define CTR_RFC3686_IV_SIZE 8
  18 #define CTR_RFC3686_BLOCK_SIZE 16
  19
  20 static inline int crypto_ctr_encrypt_walk(struct skcipher_request *req,
  21                                           void (*fn)(struct crypto_skcipher *,
  22                                                      const u8 *, u8 *))
  23 {
  24         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  25         int blocksize = crypto_skcipher_chunksize(tfm);
  26         u8 buf[MAX_CIPHER_BLOCKSIZE];
  27         struct skcipher_walk walk;
  28         int err;
  29
  30         /* avoid integer division due to variable blocksize parameter */
  31         if (WARN_ON_ONCE(!is_power_of_2(blocksize)))
  32                 return -EINVAL;
  33
  34         err = skcipher_walk_virt(&walk, req, false);
  35
  36         while (walk.nbytes > 0) {
  37                 u8 *dst = walk.dst.virt.addr;
  38                 u8 *src = walk.src.virt.addr;
  39                 int nbytes = walk.nbytes;
  40                 int tail = 0;
  41
  42                 if (nbytes < walk.total) {
  43                         tail = walk.nbytes & (blocksize - 1);
  44                         nbytes -= tail;
  45                 }
  46
  47                 do {
  48                         int bsize = min(nbytes, blocksize);
  49
  50                         fn(tfm, walk.iv, buf);
  51
  52                         crypto_xor_cpy(dst, src, buf, bsize);
  53                         crypto_inc(walk.iv, blocksize);
  54
  55                         dst += bsize;
  56                         src += bsize;
  57                         nbytes -= bsize;
  58                 } while (nbytes > 0);
  59
  60                 err = skcipher_walk_done(&walk, tail);
  61         }
  62         return err;
  63 }
  64
  65 #endif  /* _CRYPTO_CTR_H */