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