chacha20poly1305.c

  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
 20struct chachapoly_instance_ctx {
 21	struct crypto_skcipher_spawn chacha;
 22	unsigned int saltlen;
 23};
 24
 25struct 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
 32struct chacha_req {
 33	u8 iv[CHACHA_IV_SIZE];
 34	struct scatterlist src[1];
 35	struct skcipher_request req; /* must be last member */
 36};
 37
 38struct 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
 56static 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
 70static 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
 81static 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
 94static void chacha_decrypt_done(void *data, int err)
 95{
 96	async_done_continue(data, err, poly_verify_tag);
 97}
 98
 99static 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
126skip:
127	return poly_verify_tag(req);
128}
129
130static 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
197static void poly_genkey_done(void *data, int err)
198{
199	async_done_continue(data, err, poly_hash);
200}
201
202static 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
236static void chacha_encrypt_done(void *data, int err)
237{
238	async_done_continue(data, err, poly_genkey);
239}
240
241static 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
268skip:
269	return poly_genkey(req);
270}
271
272static 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
287static 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
303static 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
320static 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
329static 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
356static 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
363static 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
371static 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) {
439err_free_inst:
440		chachapoly_free(inst);
441	}
442	return err;
443}
444
445static int rfc7539_create(struct crypto_template *tmpl, struct rtattr **tb)
446{
447	return chachapoly_create(tmpl, tb, "rfc7539", 12);
448}
449
450static int rfc7539esp_create(struct crypto_template *tmpl, struct rtattr **tb)
451{
452	return chachapoly_create(tmpl, tb, "rfc7539esp", 8);
453}
454
455static 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
467static int __init chacha20poly1305_module_init(void)
468{
469	return crypto_register_templates(rfc7539_tmpls,
470					 ARRAY_SIZE(rfc7539_tmpls));
471}
472
473static void __exit chacha20poly1305_module_exit(void)
474{
475	crypto_unregister_templates(rfc7539_tmpls,
476				    ARRAY_SIZE(rfc7539_tmpls));
477}
478
479module_init(chacha20poly1305_module_init);
480module_exit(chacha20poly1305_module_exit);
481
482MODULE_LICENSE("GPL");
483MODULE_AUTHOR("Martin Willi <martin@strongswan.org>");
484MODULE_DESCRIPTION("ChaCha20-Poly1305 AEAD");
485MODULE_ALIAS_CRYPTO("rfc7539");
486MODULE_ALIAS_CRYPTO("rfc7539esp");