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(tfm: 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(buf: tag, sg: req->src,
87 start: req->assoclen + rctx->cryptlen,
88 nbytes: sizeof(tag), out: 0);
89 if (crypto_memneq(a: tag, b: rctx->tag, size: sizeof(tag)))
90 return -EBADMSG;
91 return 0;
92}
93
94static void chacha_decrypt_done(void *data, int err)
95{
96 async_done_continue(req: data, err, cont: poly_verify_tag);
97}
98
99static int chacha_decrypt(struct aead_request *req)
100{
101 struct chachapoly_ctx *ctx = crypto_aead_ctx(tfm: 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(iv: creq->iv, req, icb: 1);
111
112 src = scatterwalk_ffwd(dst: rctx->src, src: req->src, len: req->assoclen);
113 dst = src;
114 if (req->src != req->dst)
115 dst = scatterwalk_ffwd(dst: rctx->dst, src: req->dst, len: req->assoclen);
116
117 skcipher_request_set_callback(req: &creq->req, flags: rctx->flags,
118 compl: chacha_decrypt_done, data: req);
119 skcipher_request_set_tfm(req: &creq->req, tfm: ctx->chacha);
120 skcipher_request_set_crypt(req: &creq->req, src, dst,
121 cryptlen: rctx->cryptlen, iv: creq->iv);
122 err = crypto_skcipher_decrypt(req: &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(dst: req->dst, src: sg, nbytes: req->assoclen);
151
152 if (rctx->cryptlen == req->cryptlen) /* encrypting */
153 sg = req->dst;
154
155 poly1305_init(desc: &desc, key: rctx->key);
156 scatterwalk_start(walk: &walk, sg);
157
158 total = rctx->assoclen;
159 while (total) {
160 unsigned int n = scatterwalk_next(walk: &walk, total);
161
162 poly1305_update(desc: &desc, src: walk.addr, nbytes: n);
163 scatterwalk_done_src(walk: &walk, nbytes: n);
164 total -= n;
165 }
166
167 padlen = -rctx->assoclen % POLY1305_BLOCK_SIZE;
168 poly1305_update(desc: &desc, src: zp, nbytes: padlen);
169
170 scatterwalk_skip(walk: &walk, nbytes: req->assoclen - rctx->assoclen);
171
172 total = rctx->cryptlen;
173 while (total) {
174 unsigned int n = scatterwalk_next(walk: &walk, total);
175
176 poly1305_update(desc: &desc, src: walk.addr, nbytes: n);
177 scatterwalk_done_src(walk: &walk, nbytes: n);
178 total -= n;
179 }
180
181 padlen = -rctx->cryptlen % POLY1305_BLOCK_SIZE;
182 poly1305_update(desc: &desc, src: zp, nbytes: padlen);
183
184 tail.assoclen = cpu_to_le64(rctx->assoclen);
185 tail.cryptlen = cpu_to_le64(rctx->cryptlen);
186 poly1305_update(desc: &desc, src: tail.u8, nbytes: sizeof(tail));
187 memzero_explicit(s: &tail, count: sizeof(tail));
188 poly1305_final(desc: &desc, digest: rctx->tag);
189
190 if (rctx->cryptlen != req->cryptlen)
191 return chacha_decrypt(req);
192
193 memcpy_to_scatterwalk(walk: &walk, buf: rctx->tag, nbytes: sizeof(rctx->tag));
194 return 0;
195}
196
197static void poly_genkey_done(void *data, int err)
198{
199 async_done_continue(req: data, err, cont: 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(iv: creq->iv, req, icb: 0);
222
223 skcipher_request_set_callback(req: &creq->req, flags: rctx->flags,
224 compl: poly_genkey_done, data: req);
225 skcipher_request_set_tfm(req: &creq->req, tfm: ctx->chacha);
226 skcipher_request_set_crypt(req: &creq->req, src: creq->src, dst: creq->src,
227 POLY1305_KEY_SIZE, iv: creq->iv);
228
229 err = crypto_skcipher_decrypt(req: &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(req: data, err, cont: poly_genkey);
239}
240
241static int chacha_encrypt(struct aead_request *req)
242{
243 struct chachapoly_ctx *ctx = crypto_aead_ctx(tfm: 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(iv: creq->iv, req, icb: 1);
253
254 src = scatterwalk_ffwd(dst: rctx->src, src: req->src, len: req->assoclen);
255 dst = src;
256 if (req->src != req->dst)
257 dst = scatterwalk_ffwd(dst: rctx->dst, src: req->dst, len: req->assoclen);
258
259 skcipher_request_set_callback(req: &creq->req, flags: rctx->flags,
260 compl: chacha_encrypt_done, data: req);
261 skcipher_request_set_tfm(req: &creq->req, tfm: ctx->chacha);
262 skcipher_request_set_crypt(req: &creq->req, src, dst,
263 cryptlen: req->cryptlen, iv: creq->iv);
264 err = crypto_skcipher_encrypt(req: &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(tfm: 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(tfm: ctx->chacha, CRYPTO_TFM_REQ_MASK);
315 crypto_skcipher_set_flags(tfm: ctx->chacha, flags: crypto_aead_get_flags(tfm: aead) &
316 CRYPTO_TFM_REQ_MASK);
317 return crypto_skcipher_setkey(tfm: 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(aead: 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(spawn: &ictx->chacha);
338 if (IS_ERR(ptr: chacha))
339 return PTR_ERR(ptr: 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 aead: tfm,
348 reqsize: align + offsetof(struct chachapoly_req_ctx, u) +
349 offsetof(struct chacha_req, req) +
350 sizeof(struct skcipher_request) +
351 crypto_skcipher_reqsize(tfm: 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(tfm: 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(spawn: &ctx->chacha);
368 kfree(objp: 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_ret: &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(spawn: &ctx->chacha, inst: aead_crypto_instance(inst),
394 name: crypto_attr_alg_name(rta: tb[1]), type: 0, mask);
395 if (err)
396 goto err_free_inst;
397 chacha = crypto_spawn_skcipher_alg_common(spawn: &ctx->chacha);
398
399 err = -EINVAL;
400 if (strcmp(crypto_attr_alg_name(rta: tb[2]), "poly1305") &&
401 strcmp(crypto_attr_alg_name(rta: 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(buf: inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
412 fmt: "%s(%s,poly1305)", name,
413 chacha->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
414 goto err_free_inst;
415 if (snprintf(buf: inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
416 fmt: "%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, name: "rfc7539", ivsize: 12);
448}
449
450static int rfc7539esp_create(struct crypto_template *tmpl, struct rtattr **tb)
451{
452 return chachapoly_create(tmpl, tb, name: "rfc7539esp", ivsize: 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(tmpls: rfc7539_tmpls,
470 ARRAY_SIZE(rfc7539_tmpls));
471}
472
473static void __exit chacha20poly1305_module_exit(void)
474{
475 crypto_unregister_templates(tmpls: 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");
487

source code of linux/crypto/chacha20poly1305.c