1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun
3*4882a593Smuzhiyun /*
4*4882a593Smuzhiyun * OFB: Output FeedBack mode
5*4882a593Smuzhiyun *
6*4882a593Smuzhiyun * Copyright (C) 2018 ARM Limited or its affiliates.
7*4882a593Smuzhiyun * All rights reserved.
8*4882a593Smuzhiyun */
9*4882a593Smuzhiyun
10*4882a593Smuzhiyun #include <crypto/algapi.h>
11*4882a593Smuzhiyun #include <crypto/internal/cipher.h>
12*4882a593Smuzhiyun #include <crypto/internal/skcipher.h>
13*4882a593Smuzhiyun #include <linux/err.h>
14*4882a593Smuzhiyun #include <linux/init.h>
15*4882a593Smuzhiyun #include <linux/kernel.h>
16*4882a593Smuzhiyun #include <linux/module.h>
17*4882a593Smuzhiyun
crypto_ofb_crypt(struct skcipher_request * req)18*4882a593Smuzhiyun static int crypto_ofb_crypt(struct skcipher_request *req)
19*4882a593Smuzhiyun {
20*4882a593Smuzhiyun struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
21*4882a593Smuzhiyun struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
22*4882a593Smuzhiyun const unsigned int bsize = crypto_cipher_blocksize(cipher);
23*4882a593Smuzhiyun struct skcipher_walk walk;
24*4882a593Smuzhiyun int err;
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun err = skcipher_walk_virt(&walk, req, false);
27*4882a593Smuzhiyun
28*4882a593Smuzhiyun while (walk.nbytes >= bsize) {
29*4882a593Smuzhiyun const u8 *src = walk.src.virt.addr;
30*4882a593Smuzhiyun u8 *dst = walk.dst.virt.addr;
31*4882a593Smuzhiyun u8 * const iv = walk.iv;
32*4882a593Smuzhiyun unsigned int nbytes = walk.nbytes;
33*4882a593Smuzhiyun
34*4882a593Smuzhiyun do {
35*4882a593Smuzhiyun crypto_cipher_encrypt_one(cipher, iv, iv);
36*4882a593Smuzhiyun crypto_xor_cpy(dst, src, iv, bsize);
37*4882a593Smuzhiyun dst += bsize;
38*4882a593Smuzhiyun src += bsize;
39*4882a593Smuzhiyun } while ((nbytes -= bsize) >= bsize);
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun err = skcipher_walk_done(&walk, nbytes);
42*4882a593Smuzhiyun }
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun if (walk.nbytes) {
45*4882a593Smuzhiyun crypto_cipher_encrypt_one(cipher, walk.iv, walk.iv);
46*4882a593Smuzhiyun crypto_xor_cpy(walk.dst.virt.addr, walk.src.virt.addr, walk.iv,
47*4882a593Smuzhiyun walk.nbytes);
48*4882a593Smuzhiyun err = skcipher_walk_done(&walk, 0);
49*4882a593Smuzhiyun }
50*4882a593Smuzhiyun return err;
51*4882a593Smuzhiyun }
52*4882a593Smuzhiyun
crypto_ofb_create(struct crypto_template * tmpl,struct rtattr ** tb)53*4882a593Smuzhiyun static int crypto_ofb_create(struct crypto_template *tmpl, struct rtattr **tb)
54*4882a593Smuzhiyun {
55*4882a593Smuzhiyun struct skcipher_instance *inst;
56*4882a593Smuzhiyun struct crypto_alg *alg;
57*4882a593Smuzhiyun int err;
58*4882a593Smuzhiyun
59*4882a593Smuzhiyun inst = skcipher_alloc_instance_simple(tmpl, tb);
60*4882a593Smuzhiyun if (IS_ERR(inst))
61*4882a593Smuzhiyun return PTR_ERR(inst);
62*4882a593Smuzhiyun
63*4882a593Smuzhiyun alg = skcipher_ialg_simple(inst);
64*4882a593Smuzhiyun
65*4882a593Smuzhiyun /* OFB mode is a stream cipher. */
66*4882a593Smuzhiyun inst->alg.base.cra_blocksize = 1;
67*4882a593Smuzhiyun
68*4882a593Smuzhiyun /*
69*4882a593Smuzhiyun * To simplify the implementation, configure the skcipher walk to only
70*4882a593Smuzhiyun * give a partial block at the very end, never earlier.
71*4882a593Smuzhiyun */
72*4882a593Smuzhiyun inst->alg.chunksize = alg->cra_blocksize;
73*4882a593Smuzhiyun
74*4882a593Smuzhiyun inst->alg.encrypt = crypto_ofb_crypt;
75*4882a593Smuzhiyun inst->alg.decrypt = crypto_ofb_crypt;
76*4882a593Smuzhiyun
77*4882a593Smuzhiyun err = skcipher_register_instance(tmpl, inst);
78*4882a593Smuzhiyun if (err)
79*4882a593Smuzhiyun inst->free(inst);
80*4882a593Smuzhiyun
81*4882a593Smuzhiyun return err;
82*4882a593Smuzhiyun }
83*4882a593Smuzhiyun
84*4882a593Smuzhiyun static struct crypto_template crypto_ofb_tmpl = {
85*4882a593Smuzhiyun .name = "ofb",
86*4882a593Smuzhiyun .create = crypto_ofb_create,
87*4882a593Smuzhiyun .module = THIS_MODULE,
88*4882a593Smuzhiyun };
89*4882a593Smuzhiyun
crypto_ofb_module_init(void)90*4882a593Smuzhiyun static int __init crypto_ofb_module_init(void)
91*4882a593Smuzhiyun {
92*4882a593Smuzhiyun return crypto_register_template(&crypto_ofb_tmpl);
93*4882a593Smuzhiyun }
94*4882a593Smuzhiyun
crypto_ofb_module_exit(void)95*4882a593Smuzhiyun static void __exit crypto_ofb_module_exit(void)
96*4882a593Smuzhiyun {
97*4882a593Smuzhiyun crypto_unregister_template(&crypto_ofb_tmpl);
98*4882a593Smuzhiyun }
99*4882a593Smuzhiyun
100*4882a593Smuzhiyun subsys_initcall(crypto_ofb_module_init);
101*4882a593Smuzhiyun module_exit(crypto_ofb_module_exit);
102*4882a593Smuzhiyun
103*4882a593Smuzhiyun MODULE_LICENSE("GPL");
104*4882a593Smuzhiyun MODULE_DESCRIPTION("OFB block cipher mode of operation");
105*4882a593Smuzhiyun MODULE_ALIAS_CRYPTO("ofb");
106*4882a593Smuzhiyun MODULE_IMPORT_NS(CRYPTO_INTERNAL);
107