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