1 // SPDX-License-Identifier: GPL-2.0
4 * OFB: Output FeedBack mode
6 * Copyright (C) 2018 ARM Limited or its affiliates.
10 #include <crypto/algapi.h>
11 #include <crypto/internal/cipher.h>
12 #include <crypto/internal/skcipher.h>
13 #include <linux/err.h>
14 #include <linux/init.h>
15 #include <linux/kernel.h>
16 #include <linux/module.h>
18 static int crypto_ofb_crypt(struct skcipher_request
*req
)
20 struct crypto_skcipher
*tfm
= crypto_skcipher_reqtfm(req
);
21 struct crypto_cipher
*cipher
= skcipher_cipher_simple(tfm
);
22 const unsigned int bsize
= crypto_cipher_blocksize(cipher
);
23 struct skcipher_walk walk
;
26 err
= skcipher_walk_virt(&walk
, req
, false);
28 while (walk
.nbytes
>= bsize
) {
29 const u8
*src
= walk
.src
.virt
.addr
;
30 u8
*dst
= walk
.dst
.virt
.addr
;
31 u8
* const iv
= walk
.iv
;
32 unsigned int nbytes
= walk
.nbytes
;
35 crypto_cipher_encrypt_one(cipher
, iv
, iv
);
36 crypto_xor_cpy(dst
, src
, iv
, bsize
);
39 } while ((nbytes
-= bsize
) >= bsize
);
41 err
= skcipher_walk_done(&walk
, nbytes
);
45 crypto_cipher_encrypt_one(cipher
, walk
.iv
, walk
.iv
);
46 crypto_xor_cpy(walk
.dst
.virt
.addr
, walk
.src
.virt
.addr
, walk
.iv
,
48 err
= skcipher_walk_done(&walk
, 0);
53 static int crypto_ofb_create(struct crypto_template
*tmpl
, struct rtattr
**tb
)
55 struct skcipher_instance
*inst
;
56 struct crypto_alg
*alg
;
59 inst
= skcipher_alloc_instance_simple(tmpl
, tb
);
63 alg
= skcipher_ialg_simple(inst
);
65 /* OFB mode is a stream cipher. */
66 inst
->alg
.base
.cra_blocksize
= 1;
69 * To simplify the implementation, configure the skcipher walk to only
70 * give a partial block at the very end, never earlier.
72 inst
->alg
.chunksize
= alg
->cra_blocksize
;
74 inst
->alg
.encrypt
= crypto_ofb_crypt
;
75 inst
->alg
.decrypt
= crypto_ofb_crypt
;
77 err
= skcipher_register_instance(tmpl
, inst
);
84 static struct crypto_template crypto_ofb_tmpl
= {
86 .create
= crypto_ofb_create
,
87 .module
= THIS_MODULE
,
90 static int __init
crypto_ofb_module_init(void)
92 return crypto_register_template(&crypto_ofb_tmpl
);
95 static void __exit
crypto_ofb_module_exit(void)
97 crypto_unregister_template(&crypto_ofb_tmpl
);
100 subsys_initcall(crypto_ofb_module_init
);
101 module_exit(crypto_ofb_module_exit
);
103 MODULE_LICENSE("GPL");
104 MODULE_DESCRIPTION("OFB block cipher mode of operation");
105 MODULE_ALIAS_CRYPTO("ofb");
106 MODULE_IMPORT_NS(CRYPTO_INTERNAL
);