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 */
66
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