LXR linux/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
  20static 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 */
  66