1 // SPDX-License-Identifier: GPL-2.0-or-later 1
2 /*
3 * XCTR: XOR Counter mode - Adapted from ctr.c
4 *
5 * (C) Copyright IBM Corp. 2007 - Joy Latten <
6 * Copyright 2021 Google LLC
7 */
8
9 /*
10 * XCTR mode is a blockcipher mode of operatio
11 * closely related to the CTR mode of operatio
12 * generates the keystream using E(CTR + IV) w
13 * keystream using E(CTR ^ IV). This allows im
14 * with multi-limb integers (as is required in
15 * using little-endian arithmetic which makes
16 *
17 * See the HCTR2 paper for more details:
18 * Length-preserving encryption with HCTR
19 * (https://eprint.iacr.org/2021/1441.pdf
20 */
21
22 #include <crypto/algapi.h>
23 #include <crypto/internal/cipher.h>
24 #include <crypto/internal/skcipher.h>
25 #include <linux/err.h>
26 #include <linux/init.h>
27 #include <linux/kernel.h>
28 #include <linux/module.h>
29 #include <linux/slab.h>
30
31 /* For now this implementation is limited to 1
32 #define XCTR_BLOCKSIZE 16
33
34 static void crypto_xctr_crypt_final(struct skc
35 struct cryp
36 {
37 u8 keystream[XCTR_BLOCKSIZE];
38 const u8 *src = walk->src.virt.addr;
39 u8 *dst = walk->dst.virt.addr;
40 unsigned int nbytes = walk->nbytes;
41 __le32 ctr32 = cpu_to_le32(byte_ctr /
42
43 crypto_xor(walk->iv, (u8 *)&ctr32, siz
44 crypto_cipher_encrypt_one(tfm, keystre
45 crypto_xor_cpy(dst, keystream, src, nb
46 crypto_xor(walk->iv, (u8 *)&ctr32, siz
47 }
48
49 static int crypto_xctr_crypt_segment(struct sk
50 struct cry
51 {
52 void (*fn)(struct crypto_tfm *, u8 *,
53 crypto_cipher_alg(tfm)->cia
54 const u8 *src = walk->src.virt.addr;
55 u8 *dst = walk->dst.virt.addr;
56 unsigned int nbytes = walk->nbytes;
57 __le32 ctr32 = cpu_to_le32(byte_ctr /
58
59 do {
60 crypto_xor(walk->iv, (u8 *)&ct
61 fn(crypto_cipher_tfm(tfm), dst
62 crypto_xor(dst, src, XCTR_BLOC
63 crypto_xor(walk->iv, (u8 *)&ct
64
65 le32_add_cpu(&ctr32, 1);
66
67 src += XCTR_BLOCKSIZE;
68 dst += XCTR_BLOCKSIZE;
69 } while ((nbytes -= XCTR_BLOCKSIZE) >=
70
71 return nbytes;
72 }
73
74 static int crypto_xctr_crypt_inplace(struct sk
75 struct cry
76 {
77 void (*fn)(struct crypto_tfm *, u8 *,
78 crypto_cipher_alg(tfm)->cia
79 unsigned long alignmask = crypto_ciphe
80 unsigned int nbytes = walk->nbytes;
81 u8 *data = walk->src.virt.addr;
82 u8 tmp[XCTR_BLOCKSIZE + MAX_CIPHER_ALI
83 u8 *keystream = PTR_ALIGN(tmp + 0, ali
84 __le32 ctr32 = cpu_to_le32(byte_ctr /
85
86 do {
87 crypto_xor(walk->iv, (u8 *)&ct
88 fn(crypto_cipher_tfm(tfm), key
89 crypto_xor(data, keystream, XC
90 crypto_xor(walk->iv, (u8 *)&ct
91
92 le32_add_cpu(&ctr32, 1);
93
94 data += XCTR_BLOCKSIZE;
95 } while ((nbytes -= XCTR_BLOCKSIZE) >=
96
97 return nbytes;
98 }
99
100 static int crypto_xctr_crypt(struct skcipher_r
101 {
102 struct crypto_skcipher *tfm = crypto_s
103 struct crypto_cipher *cipher = skciphe
104 struct skcipher_walk walk;
105 unsigned int nbytes;
106 int err;
107 u32 byte_ctr = 0;
108
109 err = skcipher_walk_virt(&walk, req, f
110
111 while (walk.nbytes >= XCTR_BLOCKSIZE)
112 if (walk.src.virt.addr == walk
113 nbytes = crypto_xctr_c
114
115 else
116 nbytes = crypto_xctr_c
117
118
119 byte_ctr += walk.nbytes - nbyt
120 err = skcipher_walk_done(&walk
121 }
122
123 if (walk.nbytes) {
124 crypto_xctr_crypt_final(&walk,
125 err = skcipher_walk_done(&walk
126 }
127
128 return err;
129 }
130
131 static int crypto_xctr_create(struct crypto_te
132 {
133 struct skcipher_instance *inst;
134 struct crypto_alg *alg;
135 int err;
136
137 inst = skcipher_alloc_instance_simple(
138 if (IS_ERR(inst))
139 return PTR_ERR(inst);
140
141 alg = skcipher_ialg_simple(inst);
142
143 /* Block size must be 16 bytes. */
144 err = -EINVAL;
145 if (alg->cra_blocksize != XCTR_BLOCKSI
146 goto out_free_inst;
147
148 /* XCTR mode is a stream cipher. */
149 inst->alg.base.cra_blocksize = 1;
150
151 /*
152 * To simplify the implementation, con
153 * give a partial block at the very en
154 */
155 inst->alg.chunksize = alg->cra_blocksi
156
157 inst->alg.encrypt = crypto_xctr_crypt;
158 inst->alg.decrypt = crypto_xctr_crypt;
159
160 err = skcipher_register_instance(tmpl,
161 if (err) {
162 out_free_inst:
163 inst->free(inst);
164 }
165
166 return err;
167 }
168
169 static struct crypto_template crypto_xctr_tmpl
170 .name = "xctr",
171 .create = crypto_xctr_create,
172 .module = THIS_MODULE,
173 };
174
175 static int __init crypto_xctr_module_init(void
176 {
177 return crypto_register_template(&crypt
178 }
179
180 static void __exit crypto_xctr_module_exit(voi
181 {
182 crypto_unregister_template(&crypto_xct
183 }
184
185 subsys_initcall(crypto_xctr_module_init);
186 module_exit(crypto_xctr_module_exit);
187
188 MODULE_LICENSE("GPL");
189 MODULE_DESCRIPTION("XCTR block cipher mode of
190 MODULE_ALIAS_CRYPTO("xctr");
191 MODULE_IMPORT_NS(CRYPTO_INTERNAL);
192
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