1// SPDX-License-Identifier: GPL-2.0-or-later
2/*
3 * CTR: Counter mode
4 *
5 * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
6 */
7
8#include <crypto/algapi.h>
9#include <crypto/ctr.h>
10#include <crypto/internal/cipher.h>
11#include <crypto/internal/skcipher.h>
12#include <linux/err.h>
13#include <linux/init.h>
14#include <linux/kernel.h>
15#include <linux/module.h>
16#include <linux/slab.h>
17
18struct crypto_rfc3686_ctx {
19 struct crypto_skcipher *child;
20 u8 nonce[CTR_RFC3686_NONCE_SIZE];
21};
22
23struct crypto_rfc3686_req_ctx {
24 u8 iv[CTR_RFC3686_BLOCK_SIZE];
25 struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;
26};
27
28static void crypto_ctr_crypt_final(struct skcipher_walk *walk,
29 struct crypto_cipher *tfm)
30{
31 unsigned int bsize = crypto_cipher_blocksize(tfm);
32 unsigned long alignmask = crypto_cipher_alignmask(tfm);
33 u8 *ctrblk = walk->iv;
34 u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
35 u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
36 u8 *src = walk->src.virt.addr;
37 u8 *dst = walk->dst.virt.addr;
38 unsigned int nbytes = walk->nbytes;
39
40 crypto_cipher_encrypt_one(tfm, dst: keystream, src: ctrblk);
41 crypto_xor_cpy(dst, src1: keystream, src2: src, size: nbytes);
42
43 crypto_inc(a: ctrblk, size: bsize);
44}
45
46static int crypto_ctr_crypt_segment(struct skcipher_walk *walk,
47 struct crypto_cipher *tfm)
48{
49 void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
50 crypto_cipher_alg(tfm)->cia_encrypt;
51 unsigned int bsize = crypto_cipher_blocksize(tfm);
52 u8 *ctrblk = walk->iv;
53 u8 *src = walk->src.virt.addr;
54 u8 *dst = walk->dst.virt.addr;
55 unsigned int nbytes = walk->nbytes;
56
57 do {
58 /* create keystream */
59 fn(crypto_cipher_tfm(tfm), dst, ctrblk);
60 crypto_xor(dst, src, size: bsize);
61
62 /* increment counter in counterblock */
63 crypto_inc(a: ctrblk, size: bsize);
64
65 src += bsize;
66 dst += bsize;
67 } while ((nbytes -= bsize) >= bsize);
68
69 return nbytes;
70}
71
72static int crypto_ctr_crypt_inplace(struct skcipher_walk *walk,
73 struct crypto_cipher *tfm)
74{
75 void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
76 crypto_cipher_alg(tfm)->cia_encrypt;
77 unsigned int bsize = crypto_cipher_blocksize(tfm);
78 unsigned long alignmask = crypto_cipher_alignmask(tfm);
79 unsigned int nbytes = walk->nbytes;
80 u8 *ctrblk = walk->iv;
81 u8 *src = walk->src.virt.addr;
82 u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
83 u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
84
85 do {
86 /* create keystream */
87 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
88 crypto_xor(dst: src, src: keystream, size: bsize);
89
90 /* increment counter in counterblock */
91 crypto_inc(a: ctrblk, size: bsize);
92
93 src += bsize;
94 } while ((nbytes -= bsize) >= bsize);
95
96 return nbytes;
97}
98
99static int crypto_ctr_crypt(struct skcipher_request *req)
100{
101 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
102 struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
103 const unsigned int bsize = crypto_cipher_blocksize(tfm: cipher);
104 struct skcipher_walk walk;
105 unsigned int nbytes;
106 int err;
107
108 err = skcipher_walk_virt(walk: &walk, req, atomic: false);
109
110 while (walk.nbytes >= bsize) {
111 if (walk.src.virt.addr == walk.dst.virt.addr)
112 nbytes = crypto_ctr_crypt_inplace(walk: &walk, tfm: cipher);
113 else
114 nbytes = crypto_ctr_crypt_segment(walk: &walk, tfm: cipher);
115
116 err = skcipher_walk_done(walk: &walk, err: nbytes);
117 }
118
119 if (walk.nbytes) {
120 crypto_ctr_crypt_final(walk: &walk, tfm: cipher);
121 err = skcipher_walk_done(walk: &walk, err: 0);
122 }
123
124 return err;
125}
126
127static int crypto_ctr_create(struct crypto_template *tmpl, struct rtattr **tb)
128{
129 struct skcipher_instance *inst;
130 struct crypto_alg *alg;
131 int err;
132
133 inst = skcipher_alloc_instance_simple(tmpl, tb);
134 if (IS_ERR(ptr: inst))
135 return PTR_ERR(ptr: inst);
136
137 alg = skcipher_ialg_simple(inst);
138
139 /* Block size must be >= 4 bytes. */
140 err = -EINVAL;
141 if (alg->cra_blocksize < 4)
142 goto out_free_inst;
143
144 /* If this is false we'd fail the alignment of crypto_inc. */
145 if (alg->cra_blocksize % 4)
146 goto out_free_inst;
147
148 /* CTR mode is a stream cipher. */
149 inst->alg.base.cra_blocksize = 1;
150
151 /*
152 * To simplify the implementation, configure the skcipher walk to only
153 * give a partial block at the very end, never earlier.
154 */
155 inst->alg.chunksize = alg->cra_blocksize;
156
157 inst->alg.encrypt = crypto_ctr_crypt;
158 inst->alg.decrypt = crypto_ctr_crypt;
159
160 err = skcipher_register_instance(tmpl, inst);
161 if (err) {
162out_free_inst:
163 inst->free(inst);
164 }
165
166 return err;
167}
168
169static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
170 const u8 *key, unsigned int keylen)
171{
172 struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm: parent);
173 struct crypto_skcipher *child = ctx->child;
174
175 /* the nonce is stored in bytes at end of key */
176 if (keylen < CTR_RFC3686_NONCE_SIZE)
177 return -EINVAL;
178
179 memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
180 CTR_RFC3686_NONCE_SIZE);
181
182 keylen -= CTR_RFC3686_NONCE_SIZE;
183
184 crypto_skcipher_clear_flags(tfm: child, CRYPTO_TFM_REQ_MASK);
185 crypto_skcipher_set_flags(tfm: child, flags: crypto_skcipher_get_flags(tfm: parent) &
186 CRYPTO_TFM_REQ_MASK);
187 return crypto_skcipher_setkey(tfm: child, key, keylen);
188}
189
190static int crypto_rfc3686_crypt(struct skcipher_request *req)
191{
192 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
193 struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
194 struct crypto_skcipher *child = ctx->child;
195 unsigned long align = crypto_skcipher_alignmask(tfm);
196 struct crypto_rfc3686_req_ctx *rctx =
197 (void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
198 struct skcipher_request *subreq = &rctx->subreq;
199 u8 *iv = rctx->iv;
200
201 /* set up counter block */
202 memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
203 memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
204
205 /* initialize counter portion of counter block */
206 *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
207 cpu_to_be32(1);
208
209 skcipher_request_set_tfm(req: subreq, tfm: child);
210 skcipher_request_set_callback(req: subreq, flags: req->base.flags,
211 compl: req->base.complete, data: req->base.data);
212 skcipher_request_set_crypt(req: subreq, src: req->src, dst: req->dst,
213 cryptlen: req->cryptlen, iv);
214
215 return crypto_skcipher_encrypt(req: subreq);
216}
217
218static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
219{
220 struct skcipher_instance *inst = skcipher_alg_instance(skcipher: tfm);
221 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
222 struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
223 struct crypto_skcipher *cipher;
224 unsigned long align;
225 unsigned int reqsize;
226
227 cipher = crypto_spawn_skcipher(spawn);
228 if (IS_ERR(ptr: cipher))
229 return PTR_ERR(ptr: cipher);
230
231 ctx->child = cipher;
232
233 align = crypto_skcipher_alignmask(tfm);
234 align &= ~(crypto_tfm_ctx_alignment() - 1);
235 reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
236 crypto_skcipher_reqsize(tfm: cipher);
237 crypto_skcipher_set_reqsize(skcipher: tfm, reqsize);
238
239 return 0;
240}
241
242static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
243{
244 struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
245
246 crypto_free_skcipher(tfm: ctx->child);
247}
248
249static void crypto_rfc3686_free(struct skcipher_instance *inst)
250{
251 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
252
253 crypto_drop_skcipher(spawn);
254 kfree(objp: inst);
255}
256
257static int crypto_rfc3686_create(struct crypto_template *tmpl,
258 struct rtattr **tb)
259{
260 struct skcipher_instance *inst;
261 struct crypto_skcipher_spawn *spawn;
262 struct skcipher_alg_common *alg;
263 u32 mask;
264 int err;
265
266 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, mask_ret: &mask);
267 if (err)
268 return err;
269
270 inst = kzalloc(size: sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
271 if (!inst)
272 return -ENOMEM;
273
274 spawn = skcipher_instance_ctx(inst);
275
276 err = crypto_grab_skcipher(spawn, inst: skcipher_crypto_instance(inst),
277 name: crypto_attr_alg_name(rta: tb[1]), type: 0, mask);
278 if (err)
279 goto err_free_inst;
280
281 alg = crypto_spawn_skcipher_alg_common(spawn);
282
283 /* We only support 16-byte blocks. */
284 err = -EINVAL;
285 if (alg->ivsize != CTR_RFC3686_BLOCK_SIZE)
286 goto err_free_inst;
287
288 /* Not a stream cipher? */
289 if (alg->base.cra_blocksize != 1)
290 goto err_free_inst;
291
292 err = -ENAMETOOLONG;
293 if (snprintf(buf: inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
294 fmt: "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
295 goto err_free_inst;
296 if (snprintf(buf: inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
297 fmt: "rfc3686(%s)", alg->base.cra_driver_name) >=
298 CRYPTO_MAX_ALG_NAME)
299 goto err_free_inst;
300
301 inst->alg.base.cra_priority = alg->base.cra_priority;
302 inst->alg.base.cra_blocksize = 1;
303 inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
304
305 inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
306 inst->alg.chunksize = alg->chunksize;
307 inst->alg.min_keysize = alg->min_keysize + CTR_RFC3686_NONCE_SIZE;
308 inst->alg.max_keysize = alg->max_keysize + CTR_RFC3686_NONCE_SIZE;
309
310 inst->alg.setkey = crypto_rfc3686_setkey;
311 inst->alg.encrypt = crypto_rfc3686_crypt;
312 inst->alg.decrypt = crypto_rfc3686_crypt;
313
314 inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
315
316 inst->alg.init = crypto_rfc3686_init_tfm;
317 inst->alg.exit = crypto_rfc3686_exit_tfm;
318
319 inst->free = crypto_rfc3686_free;
320
321 err = skcipher_register_instance(tmpl, inst);
322 if (err) {
323err_free_inst:
324 crypto_rfc3686_free(inst);
325 }
326 return err;
327}
328
329static struct crypto_template crypto_ctr_tmpls[] = {
330 {
331 .name = "ctr",
332 .create = crypto_ctr_create,
333 .module = THIS_MODULE,
334 }, {
335 .name = "rfc3686",
336 .create = crypto_rfc3686_create,
337 .module = THIS_MODULE,
338 },
339};
340
341static int __init crypto_ctr_module_init(void)
342{
343 return crypto_register_templates(tmpls: crypto_ctr_tmpls,
344 ARRAY_SIZE(crypto_ctr_tmpls));
345}
346
347static void __exit crypto_ctr_module_exit(void)
348{
349 crypto_unregister_templates(tmpls: crypto_ctr_tmpls,
350 ARRAY_SIZE(crypto_ctr_tmpls));
351}
352
353subsys_initcall(crypto_ctr_module_init);
354module_exit(crypto_ctr_module_exit);
355
356MODULE_LICENSE("GPL");
357MODULE_DESCRIPTION("CTR block cipher mode of operation");
358MODULE_ALIAS_CRYPTO("rfc3686");
359MODULE_ALIAS_CRYPTO("ctr");
360MODULE_IMPORT_NS(CRYPTO_INTERNAL);
361

source code of linux/crypto/ctr.c