1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * algif_aead: User-space interface for AEAD algorithms
4 *
5 * Copyright (C) 2014, Stephan Mueller <smueller@chronox.de>
6 *
7 * This file provides the user-space API for AEAD ciphers.
8 *
9 * The following concept of the memory management is used:
10 *
11 * The kernel maintains two SGLs, the TX SGL and the RX SGL. The TX SGL is
12 * filled by user space with the data submitted via sendmsg (maybe with
13 * MSG_SPLICE_PAGES). Filling up the TX SGL does not cause a crypto operation
14 * -- the data will only be tracked by the kernel. Upon receipt of one recvmsg
15 * call, the caller must provide a buffer which is tracked with the RX SGL.
16 *
17 * During the processing of the recvmsg operation, the cipher request is
18 * allocated and prepared. As part of the recvmsg operation, the processed
19 * TX buffers are extracted from the TX SGL into a separate SGL.
20 *
21 * After the completion of the crypto operation, the RX SGL and the cipher
22 * request is released. The extracted TX SGL parts are released together with
23 * the RX SGL release.
24 */
25
26 #include <crypto/internal/aead.h>
27 #include <crypto/scatterwalk.h>
28 #include <crypto/if_alg.h>
29 #include <crypto/skcipher.h>
30 #include <crypto/null.h>
31 #include <linux/init.h>
32 #include <linux/list.h>
33 #include <linux/kernel.h>
34 #include <linux/mm.h>
35 #include <linux/module.h>
36 #include <linux/net.h>
37 #include <net/sock.h>
38
39 struct aead_tfm {
40 struct crypto_aead *aead;
41 struct crypto_sync_skcipher *null_tfm;
42 };
43
44 static inline bool aead_sufficient_data(struct sock *sk)
45 {
46 struct alg_sock *ask = alg_sk(sk);
47 struct sock *psk = ask->parent;
48 struct alg_sock *pask = alg_sk(psk);
49 struct af_alg_ctx *ctx = ask->private;
50 struct aead_tfm *aeadc = pask->private;
51 struct crypto_aead *tfm = aeadc->aead;
52 unsigned int as = crypto_aead_authsize(tfm);
53
54 /*
55 * The minimum amount of memory needed for an AEAD cipher is
56 * the AAD and in case of decryption the tag.
57 */
58 return ctx->used >= ctx->aead_assoclen + (ctx->enc ? 0 : as);
59 }
60
61 static int aead_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
62 {
63 struct sock *sk = sock->sk;
64 struct alg_sock *ask = alg_sk(sk);
65 struct sock *psk = ask->parent;
66 struct alg_sock *pask = alg_sk(psk);
67 struct aead_tfm *aeadc = pask->private;
68 struct crypto_aead *tfm = aeadc->aead;
69 unsigned int ivsize = crypto_aead_ivsize(tfm);
70
71 return af_alg_sendmsg(sock, msg, size, ivsize);
72 }
73
74 static int crypto_aead_copy_sgl(struct crypto_sync_skcipher *null_tfm,
75 struct scatterlist *src,
76 struct scatterlist *dst, unsigned int len)
77 {
78 SYNC_SKCIPHER_REQUEST_ON_STACK(skreq, null_tfm);
79
80 skcipher_request_set_sync_tfm(skreq, null_tfm);
81 skcipher_request_set_callback(skreq, CRYPTO_TFM_REQ_MAY_SLEEP,
82 NULL, NULL);
83 skcipher_request_set_crypt(skreq, src, dst, len, NULL);
84
85 return crypto_skcipher_encrypt(skreq);
86 }
87
88 static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
89 size_t ignored, int flags)
90 {
91 struct sock *sk = sock->sk;
92 struct alg_sock *ask = alg_sk(sk);
93 struct sock *psk = ask->parent;
94 struct alg_sock *pask = alg_sk(psk);
95 struct af_alg_ctx *ctx = ask->private;
96 struct aead_tfm *aeadc = pask->private;
97 struct crypto_aead *tfm = aeadc->aead;
98 struct crypto_sync_skcipher *null_tfm = aeadc->null_tfm;
99 unsigned int i, as = crypto_aead_authsize(tfm);
100 struct af_alg_async_req *areq;
101 struct af_alg_tsgl *tsgl, *tmp;
102 struct scatterlist *rsgl_src, *tsgl_src = NULL;
103 int err = 0;
104 size_t used = 0; /* [in] TX bufs to be en/decrypted */
105 size_t outlen = 0; /* [out] RX bufs produced by kernel */
106 size_t usedpages = 0; /* [in] RX bufs to be used from user */
107 size_t processed = 0; /* [in] TX bufs to be consumed */
108
109 if (!ctx->init || ctx->more) {
110 err = af_alg_wait_for_data(sk, flags, 0);
111 if (err)
112 return err;
113 }
114
115 /*
116 * Data length provided by caller via sendmsg that has not yet been
117 * processed.
118 */
119 used = ctx->used;
120
121 /*
122 * Make sure sufficient data is present -- note, the same check is also
123 * present in sendmsg. The checks in sendmsg shall provide an
124 * information to the data sender that something is wrong, but they are
125 * irrelevant to maintain the kernel integrity. We need this check
126 * here too in case user space decides to not honor the error message
127 * in sendmsg and still call recvmsg. This check here protects the
128 * kernel integrity.
129 */
130 if (!aead_sufficient_data(sk))
131 return -EINVAL;
132
133 /*
134 * Calculate the minimum output buffer size holding the result of the
135 * cipher operation. When encrypting data, the receiving buffer is
136 * larger by the tag length compared to the input buffer as the
137 * encryption operation generates the tag. For decryption, the input
138 * buffer provides the tag which is consumed resulting in only the
139 * plaintext without a buffer for the tag returned to the caller.
140 */
141 if (ctx->enc)
142 outlen = used + as;
143 else
144 outlen = used - as;
145
146 /*
147 * The cipher operation input data is reduced by the associated data
148 * length as this data is processed separately later on.
149 */
150 used -= ctx->aead_assoclen;
151
152 /* Allocate cipher request for current operation. */
153 areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
154 crypto_aead_reqsize(tfm));
155 if (IS_ERR(areq))
156 return PTR_ERR(areq);
157
158 /* convert iovecs of output buffers into RX SGL */
159 err = af_alg_get_rsgl(sk, msg, flags, areq, outlen, &usedpages);
160 if (err)
161 goto free;
162
163 /*
164 * Ensure output buffer is sufficiently large. If the caller provides
165 * less buffer space, only use the relative required input size. This
166 * allows AIO operation where the caller sent all data to be processed
167 * and the AIO operation performs the operation on the different chunks
168 * of the input data.
169 */
170 if (usedpages < outlen) {
171 size_t less = outlen - usedpages;
172
173 if (used < less) {
174 err = -EINVAL;
175 goto free;
176 }
177 used -= less;
178 outlen -= less;
179 }
180
181 processed = used + ctx->aead_assoclen;
182 list_for_each_entry_safe(tsgl, tmp, &ctx->tsgl_list, list) {
183 for (i = 0; i < tsgl->cur; i++) {
184 struct scatterlist *process_sg = tsgl->sg + i;
185
186 if (!(process_sg->length) || !sg_page(process_sg))
187 continue;
188 tsgl_src = process_sg;
189 break;
190 }
191 if (tsgl_src)
192 break;
193 }
194 if (processed && !tsgl_src) {
195 err = -EFAULT;
196 goto free;
197 }
198
199 /*
200 * Copy of AAD from source to destination
201 *
202 * The AAD is copied to the destination buffer without change. Even
203 * when user space uses an in-place cipher operation, the kernel
204 * will copy the data as it does not see whether such in-place operation
205 * is initiated.
206 *
207 * To ensure efficiency, the following implementation ensure that the
208 * ciphers are invoked to perform a crypto operation in-place. This
209 * is achieved by memory management specified as follows.
210 */
211
212 /* Use the RX SGL as source (and destination) for crypto op. */
213 rsgl_src = areq->first_rsgl.sgl.sgt.sgl;
214
215 if (ctx->enc) {
216 /*
217 * Encryption operation - The in-place cipher operation is
218 * achieved by the following operation:
219 *
220 * TX SGL: AAD || PT
221 * | |
222 * | copy |
223 * v v
224 * RX SGL: AAD || PT || Tag
225 */
226 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
227 areq->first_rsgl.sgl.sgt.sgl,
228 processed);
229 if (err)
230 goto free;
231 af_alg_pull_tsgl(sk, processed, NULL, 0);
232 } else {
233 /*
234 * Decryption operation - To achieve an in-place cipher
235 * operation, the following SGL structure is used:
236 *
237 * TX SGL: AAD || CT || Tag
238 * | | ^
239 * | copy | | Create SGL link.
240 * v v |
241 * RX SGL: AAD || CT ----+
242 */
243
244 /* Copy AAD || CT to RX SGL buffer for in-place operation. */
245 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
246 areq->first_rsgl.sgl.sgt.sgl,
247 outlen);
248 if (err)
249 goto free;
250
251 /* Create TX SGL for tag and chain it to RX SGL. */
252 areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
253 processed - as);
254 if (!areq->tsgl_entries)
255 areq->tsgl_entries = 1;
256 areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
257 areq->tsgl_entries),
258 GFP_KERNEL);
259 if (!areq->tsgl) {
260 err = -ENOMEM;
261 goto free;
262 }
263 sg_init_table(areq->tsgl, areq->tsgl_entries);
264
265 /* Release TX SGL, except for tag data and reassign tag data. */
266 af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);
267
268 /* chain the areq TX SGL holding the tag with RX SGL */
269 if (usedpages) {
270 /* RX SGL present */
271 struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;
272 struct scatterlist *sg = sgl_prev->sgt.sgl;
273
274 sg_unmark_end(sg + sgl_prev->sgt.nents - 1);
275 sg_chain(sg, sgl_prev->sgt.nents + 1, areq->tsgl);
276 } else
277 /* no RX SGL present (e.g. authentication only) */
278 rsgl_src = areq->tsgl;
279 }
280
281 /* Initialize the crypto operation */
282 aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,
283 areq->first_rsgl.sgl.sgt.sgl, used, ctx->iv);
284 aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
285 aead_request_set_tfm(&areq->cra_u.aead_req, tfm);
286
287 if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
288 /* AIO operation */
289 sock_hold(sk);
290 areq->iocb = msg->msg_iocb;
291
292 /* Remember output size that will be generated. */
293 areq->outlen = outlen;
294
295 aead_request_set_callback(&areq->cra_u.aead_req,
296 CRYPTO_TFM_REQ_MAY_SLEEP,
297 af_alg_async_cb, areq);
298 err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
299 crypto_aead_decrypt(&areq->cra_u.aead_req);
300
301 /* AIO operation in progress */
302 if (err == -EINPROGRESS)
303 return -EIOCBQUEUED;
304
305 sock_put(sk);
306 } else {
307 /* Synchronous operation */
308 aead_request_set_callback(&areq->cra_u.aead_req,
309 CRYPTO_TFM_REQ_MAY_SLEEP |
310 CRYPTO_TFM_REQ_MAY_BACKLOG,
311 crypto_req_done, &ctx->wait);
312 err = crypto_wait_req(ctx->enc ?
313 crypto_aead_encrypt(&areq->cra_u.aead_req) :
314 crypto_aead_decrypt(&areq->cra_u.aead_req),
315 &ctx->wait);
316 }
317
318
319 free:
320 af_alg_free_resources(areq);
321
322 return err ? err : outlen;
323 }
324
325 static int aead_recvmsg(struct socket *sock, struct msghdr *msg,
326 size_t ignored, int flags)
327 {
328 struct sock *sk = sock->sk;
329 int ret = 0;
330
331 lock_sock(sk);
332 while (msg_data_left(msg)) {
333 int err = _aead_recvmsg(sock, msg, ignored, flags);
334
335 /*
336 * This error covers -EIOCBQUEUED which implies that we can
337 * only handle one AIO request. If the caller wants to have
338 * multiple AIO requests in parallel, he must make multiple
339 * separate AIO calls.
340 *
341 * Also return the error if no data has been processed so far.
342 */
343 if (err <= 0) {
344 if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)
345 ret = err;
346 goto out;
347 }
348
349 ret += err;
350 }
351
352 out:
353 af_alg_wmem_wakeup(sk);
354 release_sock(sk);
355 return ret;
356 }
357
358 static struct proto_ops algif_aead_ops = {
359 .family = PF_ALG,
360
361 .connect = sock_no_connect,
362 .socketpair = sock_no_socketpair,
363 .getname = sock_no_getname,
364 .ioctl = sock_no_ioctl,
365 .listen = sock_no_listen,
366 .shutdown = sock_no_shutdown,
367 .mmap = sock_no_mmap,
368 .bind = sock_no_bind,
369 .accept = sock_no_accept,
370
371 .release = af_alg_release,
372 .sendmsg = aead_sendmsg,
373 .recvmsg = aead_recvmsg,
374 .poll = af_alg_poll,
375 };
376
377 static int aead_check_key(struct socket *sock)
378 {
379 int err = 0;
380 struct sock *psk;
381 struct alg_sock *pask;
382 struct aead_tfm *tfm;
383 struct sock *sk = sock->sk;
384 struct alg_sock *ask = alg_sk(sk);
385
386 lock_sock(sk);
387 if (!atomic_read(&ask->nokey_refcnt))
388 goto unlock_child;
389
390 psk = ask->parent;
391 pask = alg_sk(ask->parent);
392 tfm = pask->private;
393
394 err = -ENOKEY;
395 lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
396 if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
397 goto unlock;
398
399 atomic_dec(&pask->nokey_refcnt);
400 atomic_set(&ask->nokey_refcnt, 0);
401
402 err = 0;
403
404 unlock:
405 release_sock(psk);
406 unlock_child:
407 release_sock(sk);
408
409 return err;
410 }
411
412 static int aead_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
413 size_t size)
414 {
415 int err;
416
417 err = aead_check_key(sock);
418 if (err)
419 return err;
420
421 return aead_sendmsg(sock, msg, size);
422 }
423
424 static int aead_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
425 size_t ignored, int flags)
426 {
427 int err;
428
429 err = aead_check_key(sock);
430 if (err)
431 return err;
432
433 return aead_recvmsg(sock, msg, ignored, flags);
434 }
435
436 static struct proto_ops algif_aead_ops_nokey = {
437 .family = PF_ALG,
438
439 .connect = sock_no_connect,
440 .socketpair = sock_no_socketpair,
441 .getname = sock_no_getname,
442 .ioctl = sock_no_ioctl,
443 .listen = sock_no_listen,
444 .shutdown = sock_no_shutdown,
445 .mmap = sock_no_mmap,
446 .bind = sock_no_bind,
447 .accept = sock_no_accept,
448
449 .release = af_alg_release,
450 .sendmsg = aead_sendmsg_nokey,
451 .recvmsg = aead_recvmsg_nokey,
452 .poll = af_alg_poll,
453 };
454
455 static void *aead_bind(const char *name, u32 type, u32 mask)
456 {
457 struct aead_tfm *tfm;
458 struct crypto_aead *aead;
459 struct crypto_sync_skcipher *null_tfm;
460
461 tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
462 if (!tfm)
463 return ERR_PTR(-ENOMEM);
464
465 aead = crypto_alloc_aead(name, type, mask);
466 if (IS_ERR(aead)) {
467 kfree(tfm);
468 return ERR_CAST(aead);
469 }
470
471 null_tfm = crypto_get_default_null_skcipher();
472 if (IS_ERR(null_tfm)) {
473 crypto_free_aead(aead);
474 kfree(tfm);
475 return ERR_CAST(null_tfm);
476 }
477
478 tfm->aead = aead;
479 tfm->null_tfm = null_tfm;
480
481 return tfm;
482 }
483
484 static void aead_release(void *private)
485 {
486 struct aead_tfm *tfm = private;
487
488 crypto_free_aead(tfm->aead);
489 crypto_put_default_null_skcipher();
490 kfree(tfm);
491 }
492
493 static int aead_setauthsize(void *private, unsigned int authsize)
494 {
495 struct aead_tfm *tfm = private;
496
497 return crypto_aead_setauthsize(tfm->aead, authsize);
498 }
499
500 static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
501 {
502 struct aead_tfm *tfm = private;
503
504 return crypto_aead_setkey(tfm->aead, key, keylen);
505 }
506
507 static void aead_sock_destruct(struct sock *sk)
508 {
509 struct alg_sock *ask = alg_sk(sk);
510 struct af_alg_ctx *ctx = ask->private;
511 struct sock *psk = ask->parent;
512 struct alg_sock *pask = alg_sk(psk);
513 struct aead_tfm *aeadc = pask->private;
514 struct crypto_aead *tfm = aeadc->aead;
515 unsigned int ivlen = crypto_aead_ivsize(tfm);
516
517 af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
518 sock_kzfree_s(sk, ctx->iv, ivlen);
519 sock_kfree_s(sk, ctx, ctx->len);
520 af_alg_release_parent(sk);
521 }
522
523 static int aead_accept_parent_nokey(void *private, struct sock *sk)
524 {
525 struct af_alg_ctx *ctx;
526 struct alg_sock *ask = alg_sk(sk);
527 struct aead_tfm *tfm = private;
528 struct crypto_aead *aead = tfm->aead;
529 unsigned int len = sizeof(*ctx);
530 unsigned int ivlen = crypto_aead_ivsize(aead);
531
532 ctx = sock_kmalloc(sk, len, GFP_KERNEL);
533 if (!ctx)
534 return -ENOMEM;
535 memset(ctx, 0, len);
536
537 ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
538 if (!ctx->iv) {
539 sock_kfree_s(sk, ctx, len);
540 return -ENOMEM;
541 }
542 memset(ctx->iv, 0, ivlen);
543
544 INIT_LIST_HEAD(&ctx->tsgl_list);
545 ctx->len = len;
546 crypto_init_wait(&ctx->wait);
547
548 ask->private = ctx;
549
550 sk->sk_destruct = aead_sock_destruct;
551
552 return 0;
553 }
554
555 static int aead_accept_parent(void *private, struct sock *sk)
556 {
557 struct aead_tfm *tfm = private;
558
559 if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
560 return -ENOKEY;
561
562 return aead_accept_parent_nokey(private, sk);
563 }
564
565 static const struct af_alg_type algif_type_aead = {
566 .bind = aead_bind,
567 .release = aead_release,
568 .setkey = aead_setkey,
569 .setauthsize = aead_setauthsize,
570 .accept = aead_accept_parent,
571 .accept_nokey = aead_accept_parent_nokey,
572 .ops = &algif_aead_ops,
573 .ops_nokey = &algif_aead_ops_nokey,
574 .name = "aead",
575 .owner = THIS_MODULE
576 };
577
578 static int __init algif_aead_init(void)
579 {
580 return af_alg_register_type(&algif_type_aead);
581 }
582
583 static void __exit algif_aead_exit(void)
584 {
585 int err = af_alg_unregister_type(&algif_type_aead);
586 BUG_ON(err);
587 }
588
589 module_init(algif_aead_init);
590 module_exit(algif_aead_exit);
591 MODULE_LICENSE("GPL");
592 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
593 MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");
594
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.