1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * ChaCha20-Poly1305 AEAD, RFC7539
4 *
5 * Copyright (C) 2015 Martin Willi
6 */
7
8 #include <crypto/internal/aead.h>
9 #include <crypto/internal/hash.h>
10 #include <crypto/internal/skcipher.h>
11 #include <crypto/scatterwalk.h>
12 #include <crypto/chacha.h>
13 #include <crypto/poly1305.h>
14 #include <linux/err.h>
15 #include <linux/kernel.h>
16 #include <linux/mm.h>
17 #include <linux/module.h>
18 #include <linux/string.h>
19
20 struct chachapoly_instance_ctx {
21 struct crypto_skcipher_spawn chacha;
22 unsigned int saltlen;
23 };
24
25 struct chachapoly_ctx {
26 struct crypto_skcipher *chacha;
27 /* key bytes we use for the ChaCha20 IV */
28 unsigned int saltlen;
29 u8 salt[] __counted_by(saltlen);
30 };
31
32 struct chacha_req {
33 u8 iv[CHACHA_IV_SIZE];
34 struct scatterlist src[1];
35 struct skcipher_request req; /* must be last member */
36 };
37
38 struct chachapoly_req_ctx {
39 struct scatterlist src[2];
40 struct scatterlist dst[2];
41 /* the key we generate for Poly1305 using Chacha20 */
42 u8 key[POLY1305_KEY_SIZE];
43 /* calculated Poly1305 tag */
44 u8 tag[POLY1305_DIGEST_SIZE];
45 /* length of data to en/decrypt, without ICV */
46 unsigned int cryptlen;
47 /* Actual AD, excluding IV */
48 unsigned int assoclen;
49 /* request flags, with MAY_SLEEP cleared if needed */
50 u32 flags;
51 union {
52 struct chacha_req chacha;
53 } u;
54 };
55
async_done_continue(struct aead_request * req,int err,int (* cont)(struct aead_request *))56 static inline void async_done_continue(struct aead_request *req, int err,
57 int (*cont)(struct aead_request *))
58 {
59 if (!err) {
60 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
61
62 rctx->flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
63 err = cont(req);
64 }
65
66 if (err != -EINPROGRESS && err != -EBUSY)
67 aead_request_complete(req, err);
68 }
69
chacha_iv(u8 * iv,struct aead_request * req,u32 icb)70 static void chacha_iv(u8 *iv, struct aead_request *req, u32 icb)
71 {
72 struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
73 __le32 leicb = cpu_to_le32(icb);
74
75 memcpy(iv, &leicb, sizeof(leicb));
76 memcpy(iv + sizeof(leicb), ctx->salt, ctx->saltlen);
77 memcpy(iv + sizeof(leicb) + ctx->saltlen, req->iv,
78 CHACHA_IV_SIZE - sizeof(leicb) - ctx->saltlen);
79 }
80
poly_verify_tag(struct aead_request * req)81 static int poly_verify_tag(struct aead_request *req)
82 {
83 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
84 u8 tag[sizeof(rctx->tag)];
85
86 scatterwalk_map_and_copy(tag, req->src,
87 req->assoclen + rctx->cryptlen,
88 sizeof(tag), 0);
89 if (crypto_memneq(tag, rctx->tag, sizeof(tag)))
90 return -EBADMSG;
91 return 0;
92 }
93
chacha_decrypt_done(void * data,int err)94 static void chacha_decrypt_done(void *data, int err)
95 {
96 async_done_continue(data, err, poly_verify_tag);
97 }
98
chacha_decrypt(struct aead_request * req)99 static int chacha_decrypt(struct aead_request *req)
100 {
101 struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
102 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
103 struct chacha_req *creq = &rctx->u.chacha;
104 struct scatterlist *src, *dst;
105 int err;
106
107 if (rctx->cryptlen == 0)
108 goto skip;
109
110 chacha_iv(creq->iv, req, 1);
111
112 src = scatterwalk_ffwd(rctx->src, req->src, req->assoclen);
113 dst = src;
114 if (req->src != req->dst)
115 dst = scatterwalk_ffwd(rctx->dst, req->dst, req->assoclen);
116
117 skcipher_request_set_callback(&creq->req, rctx->flags,
118 chacha_decrypt_done, req);
119 skcipher_request_set_tfm(&creq->req, ctx->chacha);
120 skcipher_request_set_crypt(&creq->req, src, dst,
121 rctx->cryptlen, creq->iv);
122 err = crypto_skcipher_decrypt(&creq->req);
123 if (err)
124 return err;
125
126 skip:
127 return poly_verify_tag(req);
128 }
129
poly_hash(struct aead_request * req)130 static int poly_hash(struct aead_request *req)
131 {
132 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
133 const void *zp = page_address(ZERO_PAGE(0));
134 struct scatterlist *sg = req->src;
135 struct poly1305_desc_ctx desc;
136 struct scatter_walk walk;
137 struct {
138 union {
139 struct {
140 __le64 assoclen;
141 __le64 cryptlen;
142 };
143 u8 u8[16];
144 };
145 } tail;
146 unsigned int padlen;
147 unsigned int total;
148
149 if (sg != req->dst)
150 memcpy_sglist(req->dst, sg, req->assoclen);
151
152 if (rctx->cryptlen == req->cryptlen) /* encrypting */
153 sg = req->dst;
154
155 poly1305_init(&desc, rctx->key);
156 scatterwalk_start(&walk, sg);
157
158 total = rctx->assoclen;
159 while (total) {
160 unsigned int n = scatterwalk_next(&walk, total);
161
162 poly1305_update(&desc, walk.addr, n);
163 scatterwalk_done_src(&walk, n);
164 total -= n;
165 }
166
167 padlen = -rctx->assoclen % POLY1305_BLOCK_SIZE;
168 poly1305_update(&desc, zp, padlen);
169
170 scatterwalk_skip(&walk, req->assoclen - rctx->assoclen);
171
172 total = rctx->cryptlen;
173 while (total) {
174 unsigned int n = scatterwalk_next(&walk, total);
175
176 poly1305_update(&desc, walk.addr, n);
177 scatterwalk_done_src(&walk, n);
178 total -= n;
179 }
180
181 padlen = -rctx->cryptlen % POLY1305_BLOCK_SIZE;
182 poly1305_update(&desc, zp, padlen);
183
184 tail.assoclen = cpu_to_le64(rctx->assoclen);
185 tail.cryptlen = cpu_to_le64(rctx->cryptlen);
186 poly1305_update(&desc, tail.u8, sizeof(tail));
187 memzero_explicit(&tail, sizeof(tail));
188 poly1305_final(&desc, rctx->tag);
189
190 if (rctx->cryptlen != req->cryptlen)
191 return chacha_decrypt(req);
192
193 memcpy_to_scatterwalk(&walk, rctx->tag, sizeof(rctx->tag));
194 return 0;
195 }
196
poly_genkey_done(void * data,int err)197 static void poly_genkey_done(void *data, int err)
198 {
199 async_done_continue(data, err, poly_hash);
200 }
201
poly_genkey(struct aead_request * req)202 static int poly_genkey(struct aead_request *req)
203 {
204 struct crypto_aead *tfm = crypto_aead_reqtfm(req);
205 struct chachapoly_ctx *ctx = crypto_aead_ctx(tfm);
206 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
207 struct chacha_req *creq = &rctx->u.chacha;
208 int err;
209
210 rctx->assoclen = req->assoclen;
211
212 if (crypto_aead_ivsize(tfm) == 8) {
213 if (rctx->assoclen < 8)
214 return -EINVAL;
215 rctx->assoclen -= 8;
216 }
217
218 memset(rctx->key, 0, sizeof(rctx->key));
219 sg_init_one(creq->src, rctx->key, sizeof(rctx->key));
220
221 chacha_iv(creq->iv, req, 0);
222
223 skcipher_request_set_callback(&creq->req, rctx->flags,
224 poly_genkey_done, req);
225 skcipher_request_set_tfm(&creq->req, ctx->chacha);
226 skcipher_request_set_crypt(&creq->req, creq->src, creq->src,
227 POLY1305_KEY_SIZE, creq->iv);
228
229 err = crypto_skcipher_decrypt(&creq->req);
230 if (err)
231 return err;
232
233 return poly_hash(req);
234 }
235
chacha_encrypt_done(void * data,int err)236 static void chacha_encrypt_done(void *data, int err)
237 {
238 async_done_continue(data, err, poly_genkey);
239 }
240
chacha_encrypt(struct aead_request * req)241 static int chacha_encrypt(struct aead_request *req)
242 {
243 struct chachapoly_ctx *ctx = crypto_aead_ctx(crypto_aead_reqtfm(req));
244 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
245 struct chacha_req *creq = &rctx->u.chacha;
246 struct scatterlist *src, *dst;
247 int err;
248
249 if (req->cryptlen == 0)
250 goto skip;
251
252 chacha_iv(creq->iv, req, 1);
253
254 src = scatterwalk_ffwd(rctx->src, req->src, req->assoclen);
255 dst = src;
256 if (req->src != req->dst)
257 dst = scatterwalk_ffwd(rctx->dst, req->dst, req->assoclen);
258
259 skcipher_request_set_callback(&creq->req, rctx->flags,
260 chacha_encrypt_done, req);
261 skcipher_request_set_tfm(&creq->req, ctx->chacha);
262 skcipher_request_set_crypt(&creq->req, src, dst,
263 req->cryptlen, creq->iv);
264 err = crypto_skcipher_encrypt(&creq->req);
265 if (err)
266 return err;
267
268 skip:
269 return poly_genkey(req);
270 }
271
chachapoly_encrypt(struct aead_request * req)272 static int chachapoly_encrypt(struct aead_request *req)
273 {
274 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
275
276 rctx->cryptlen = req->cryptlen;
277 rctx->flags = aead_request_flags(req);
278
279 /* encrypt call chain:
280 * - chacha_encrypt/done()
281 * - poly_genkey/done()
282 * - poly_hash()
283 */
284 return chacha_encrypt(req);
285 }
286
chachapoly_decrypt(struct aead_request * req)287 static int chachapoly_decrypt(struct aead_request *req)
288 {
289 struct chachapoly_req_ctx *rctx = aead_request_ctx(req);
290
291 rctx->cryptlen = req->cryptlen - POLY1305_DIGEST_SIZE;
292 rctx->flags = aead_request_flags(req);
293
294 /* decrypt call chain:
295 * - poly_genkey/done()
296 * - poly_hash()
297 * - chacha_decrypt/done()
298 * - poly_verify_tag()
299 */
300 return poly_genkey(req);
301 }
302
chachapoly_setkey(struct crypto_aead * aead,const u8 * key,unsigned int keylen)303 static int chachapoly_setkey(struct crypto_aead *aead, const u8 *key,
304 unsigned int keylen)
305 {
306 struct chachapoly_ctx *ctx = crypto_aead_ctx(aead);
307
308 if (keylen != ctx->saltlen + CHACHA_KEY_SIZE)
309 return -EINVAL;
310
311 keylen -= ctx->saltlen;
312 memcpy(ctx->salt, key + keylen, ctx->saltlen);
313
314 crypto_skcipher_clear_flags(ctx->chacha, CRYPTO_TFM_REQ_MASK);
315 crypto_skcipher_set_flags(ctx->chacha, crypto_aead_get_flags(aead) &
316 CRYPTO_TFM_REQ_MASK);
317 return crypto_skcipher_setkey(ctx->chacha, key, keylen);
318 }
319
chachapoly_setauthsize(struct crypto_aead * tfm,unsigned int authsize)320 static int chachapoly_setauthsize(struct crypto_aead *tfm,
321 unsigned int authsize)
322 {
323 if (authsize != POLY1305_DIGEST_SIZE)
324 return -EINVAL;
325
326 return 0;
327 }
328
chachapoly_init(struct crypto_aead * tfm)329 static int chachapoly_init(struct crypto_aead *tfm)
330 {
331 struct aead_instance *inst = aead_alg_instance(tfm);
332 struct chachapoly_instance_ctx *ictx = aead_instance_ctx(inst);
333 struct chachapoly_ctx *ctx = crypto_aead_ctx(tfm);
334 struct crypto_skcipher *chacha;
335 unsigned long align;
336
337 chacha = crypto_spawn_skcipher(&ictx->chacha);
338 if (IS_ERR(chacha))
339 return PTR_ERR(chacha);
340
341 ctx->chacha = chacha;
342 ctx->saltlen = ictx->saltlen;
343
344 align = crypto_aead_alignmask(tfm);
345 align &= ~(crypto_tfm_ctx_alignment() - 1);
346 crypto_aead_set_reqsize(
347 tfm,
348 align + offsetof(struct chachapoly_req_ctx, u) +
349 offsetof(struct chacha_req, req) +
350 sizeof(struct skcipher_request) +
351 crypto_skcipher_reqsize(chacha));
352
353 return 0;
354 }
355
chachapoly_exit(struct crypto_aead * tfm)356 static void chachapoly_exit(struct crypto_aead *tfm)
357 {
358 struct chachapoly_ctx *ctx = crypto_aead_ctx(tfm);
359
360 crypto_free_skcipher(ctx->chacha);
361 }
362
chachapoly_free(struct aead_instance * inst)363 static void chachapoly_free(struct aead_instance *inst)
364 {
365 struct chachapoly_instance_ctx *ctx = aead_instance_ctx(inst);
366
367 crypto_drop_skcipher(&ctx->chacha);
368 kfree(inst);
369 }
370
chachapoly_create(struct crypto_template * tmpl,struct rtattr ** tb,const char * name,unsigned int ivsize)371 static int chachapoly_create(struct crypto_template *tmpl, struct rtattr **tb,
372 const char *name, unsigned int ivsize)
373 {
374 u32 mask;
375 struct aead_instance *inst;
376 struct chachapoly_instance_ctx *ctx;
377 struct skcipher_alg_common *chacha;
378 int err;
379
380 if (ivsize > CHACHAPOLY_IV_SIZE)
381 return -EINVAL;
382
383 err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_AEAD, &mask);
384 if (err)
385 return err;
386
387 inst = kzalloc(sizeof(*inst) + sizeof(*ctx), GFP_KERNEL);
388 if (!inst)
389 return -ENOMEM;
390 ctx = aead_instance_ctx(inst);
391 ctx->saltlen = CHACHAPOLY_IV_SIZE - ivsize;
392
393 err = crypto_grab_skcipher(&ctx->chacha, aead_crypto_instance(inst),
394 crypto_attr_alg_name(tb[1]), 0, mask);
395 if (err)
396 goto err_free_inst;
397 chacha = crypto_spawn_skcipher_alg_common(&ctx->chacha);
398
399 err = -EINVAL;
400 if (strcmp(crypto_attr_alg_name(tb[2]), "poly1305") &&
401 strcmp(crypto_attr_alg_name(tb[2]), "poly1305-generic"))
402 goto err_free_inst;
403 /* Need 16-byte IV size, including Initial Block Counter value */
404 if (chacha->ivsize != CHACHA_IV_SIZE)
405 goto err_free_inst;
406 /* Not a stream cipher? */
407 if (chacha->base.cra_blocksize != 1)
408 goto err_free_inst;
409
410 err = -ENAMETOOLONG;
411 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
412 "%s(%s,poly1305)", name,
413 chacha->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
414 goto err_free_inst;
415 if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
416 "%s(%s,poly1305-generic)", name,
417 chacha->base.cra_driver_name) >= CRYPTO_MAX_ALG_NAME)
418 goto err_free_inst;
419
420 inst->alg.base.cra_priority = chacha->base.cra_priority;
421 inst->alg.base.cra_blocksize = 1;
422 inst->alg.base.cra_alignmask = chacha->base.cra_alignmask;
423 inst->alg.base.cra_ctxsize = sizeof(struct chachapoly_ctx) +
424 ctx->saltlen;
425 inst->alg.ivsize = ivsize;
426 inst->alg.chunksize = chacha->chunksize;
427 inst->alg.maxauthsize = POLY1305_DIGEST_SIZE;
428 inst->alg.init = chachapoly_init;
429 inst->alg.exit = chachapoly_exit;
430 inst->alg.encrypt = chachapoly_encrypt;
431 inst->alg.decrypt = chachapoly_decrypt;
432 inst->alg.setkey = chachapoly_setkey;
433 inst->alg.setauthsize = chachapoly_setauthsize;
434
435 inst->free = chachapoly_free;
436
437 err = aead_register_instance(tmpl, inst);
438 if (err) {
439 err_free_inst:
440 chachapoly_free(inst);
441 }
442 return err;
443 }
444
rfc7539_create(struct crypto_template * tmpl,struct rtattr ** tb)445 static int rfc7539_create(struct crypto_template *tmpl, struct rtattr **tb)
446 {
447 return chachapoly_create(tmpl, tb, "rfc7539", 12);
448 }
449
rfc7539esp_create(struct crypto_template * tmpl,struct rtattr ** tb)450 static int rfc7539esp_create(struct crypto_template *tmpl, struct rtattr **tb)
451 {
452 return chachapoly_create(tmpl, tb, "rfc7539esp", 8);
453 }
454
455 static struct crypto_template rfc7539_tmpls[] = {
456 {
457 .name = "rfc7539",
458 .create = rfc7539_create,
459 .module = THIS_MODULE,
460 }, {
461 .name = "rfc7539esp",
462 .create = rfc7539esp_create,
463 .module = THIS_MODULE,
464 },
465 };
466
chacha20poly1305_module_init(void)467 static int __init chacha20poly1305_module_init(void)
468 {
469 return crypto_register_templates(rfc7539_tmpls,
470 ARRAY_SIZE(rfc7539_tmpls));
471 }
472
chacha20poly1305_module_exit(void)473 static void __exit chacha20poly1305_module_exit(void)
474 {
475 crypto_unregister_templates(rfc7539_tmpls,
476 ARRAY_SIZE(rfc7539_tmpls));
477 }
478
479 module_init(chacha20poly1305_module_init);
480 module_exit(chacha20poly1305_module_exit);
481
482 MODULE_LICENSE("GPL");
483 MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
484 MODULE_DESCRIPTION("ChaCha20-Poly1305 AEAD");
485 MODULE_ALIAS_CRYPTO("rfc7539");
486 MODULE_ALIAS_CRYPTO("rfc7539esp");
487