1 | // SPDX-License-Identifier: GPL-2.0 |
2 | |
3 | /* |
4 | * OFB: Output FeedBack mode |
5 | * |
6 | * Copyright (C) 2018 ARM Limited or its affiliates. |
7 | * All rights reserved. |
8 | */ |
9 | |
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> |
17 | |
18 | static int crypto_ofb_crypt(struct skcipher_request *req) |
19 | { |
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(tfm: cipher); |
23 | struct skcipher_walk walk; |
24 | int err; |
25 | |
26 | err = skcipher_walk_virt(walk: &walk, req, atomic: false); |
27 | |
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; |
33 | |
34 | do { |
35 | crypto_cipher_encrypt_one(tfm: cipher, dst: iv, src: iv); |
36 | crypto_xor_cpy(dst, src1: src, src2: iv, size: bsize); |
37 | dst += bsize; |
38 | src += bsize; |
39 | } while ((nbytes -= bsize) >= bsize); |
40 | |
41 | err = skcipher_walk_done(walk: &walk, err: nbytes); |
42 | } |
43 | |
44 | if (walk.nbytes) { |
45 | crypto_cipher_encrypt_one(tfm: cipher, dst: walk.iv, src: walk.iv); |
46 | crypto_xor_cpy(dst: walk.dst.virt.addr, src1: walk.src.virt.addr, src2: walk.iv, |
47 | size: walk.nbytes); |
48 | err = skcipher_walk_done(walk: &walk, err: 0); |
49 | } |
50 | return err; |
51 | } |
52 | |
53 | static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb) |
54 | { |
55 | struct skcipher_instance *inst; |
56 | struct crypto_alg *alg; |
57 | int err; |
58 | |
59 | inst = skcipher_alloc_instance_simple(tmpl, tb); |
60 | if (IS_ERR(ptr: inst)) |
61 | return PTR_ERR(ptr: inst); |
62 | |
63 | alg = skcipher_ialg_simple(inst); |
64 | |
65 | /* OFB mode is a stream cipher. */ |
66 | inst->alg.base.cra_blocksize = 1; |
67 | |
68 | /* |
69 | * To simplify the implementation, configure the skcipher walk to only |
70 | * give a partial block at the very end, never earlier. |
71 | */ |
72 | inst->alg.chunksize = alg->cra_blocksize; |
73 | |
74 | inst->alg.encrypt = crypto_ofb_crypt; |
75 | inst->alg.decrypt = crypto_ofb_crypt; |
76 | |
77 | err = skcipher_register_instance(tmpl, inst); |
78 | if (err) |
79 | inst->free(inst); |
80 | |
81 | return err; |
82 | } |
83 | |
84 | static struct crypto_template crypto_ofb_tmpl = { |
85 | .name = "ofb" , |
86 | .create = crypto_ofb_create, |
87 | .module = THIS_MODULE, |
88 | }; |
89 | |
90 | static int __init crypto_ofb_module_init(void) |
91 | { |
92 | return crypto_register_template(tmpl: &crypto_ofb_tmpl); |
93 | } |
94 | |
95 | static void __exit crypto_ofb_module_exit(void) |
96 | { |
97 | crypto_unregister_template(tmpl: &crypto_ofb_tmpl); |
98 | } |
99 | |
100 | subsys_initcall(crypto_ofb_module_init); |
101 | module_exit(crypto_ofb_module_exit); |
102 | |
103 | MODULE_LICENSE("GPL" ); |
104 | MODULE_DESCRIPTION("OFB block cipher mode of operation" ); |
105 | MODULE_ALIAS_CRYPTO("ofb" ); |
106 | MODULE_IMPORT_NS(CRYPTO_INTERNAL); |
107 | |