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 sendpage/sendmsg. Filling
13 * up the TX SGL does not cause a crypto operation -- the data will only be
14 * tracked by the kernel. Upon receipt of one recvmsg call, the caller must
15 * 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
aead_sufficient_data(struct sock * sk)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
aead_sendmsg(struct socket * sock,struct msghdr * msg,size_t size)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
crypto_aead_copy_sgl(struct crypto_sync_skcipher * null_tfm,struct scatterlist * src,struct scatterlist * dst,unsigned int len)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_BACKLOG,
82 NULL, NULL);
83 skcipher_request_set_crypt(skreq, src, dst, len, NULL);
84
85 return crypto_skcipher_encrypt(skreq);
86 }
87
_aead_recvmsg(struct socket * sock,struct msghdr * msg,size_t ignored,int flags)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->used) {
110 err = af_alg_wait_for_data(sk, flags);
111 if (err)
112 return err;
113 }
114
115 /*
116 * Data length provided by caller via sendmsg/sendpage that has not
117 * yet been processed.
118 */
119 used = ctx->used;
120
121 /*
122 * Make sure sufficient data is present -- note, the same check is
123 * is also present in sendmsg/sendpage. The checks in sendpage/sendmsg
124 * shall provide an information to the data sender that something is
125 * wrong, but they are irrelevant to maintain the kernel integrity.
126 * We need this check here too in case user space decides to not honor
127 * the error message in sendmsg/sendpage and still call recvmsg. This
128 * check here protects the 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.sg;
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.sg, processed);
228 if (err)
229 goto free;
230 af_alg_pull_tsgl(sk, processed, NULL, 0);
231 } else {
232 /*
233 * Decryption operation - To achieve an in-place cipher
234 * operation, the following SGL structure is used:
235 *
236 * TX SGL: AAD || CT || Tag
237 * | | ^
238 * | copy | | Create SGL link.
239 * v v |
240 * RX SGL: AAD || CT ----+
241 */
242
243 /* Copy AAD || CT to RX SGL buffer for in-place operation. */
244 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
245 areq->first_rsgl.sgl.sg, outlen);
246 if (err)
247 goto free;
248
249 /* Create TX SGL for tag and chain it to RX SGL. */
250 areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
251 processed - as);
252 if (!areq->tsgl_entries)
253 areq->tsgl_entries = 1;
254 areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
255 areq->tsgl_entries),
256 GFP_KERNEL);
257 if (!areq->tsgl) {
258 err = -ENOMEM;
259 goto free;
260 }
261 sg_init_table(areq->tsgl, areq->tsgl_entries);
262
263 /* Release TX SGL, except for tag data and reassign tag data. */
264 af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);
265
266 /* chain the areq TX SGL holding the tag with RX SGL */
267 if (usedpages) {
268 /* RX SGL present */
269 struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;
270
271 sg_unmark_end(sgl_prev->sg + sgl_prev->npages - 1);
272 sg_chain(sgl_prev->sg, sgl_prev->npages + 1,
273 areq->tsgl);
274 } else
275 /* no RX SGL present (e.g. authentication only) */
276 rsgl_src = areq->tsgl;
277 }
278
279 /* Initialize the crypto operation */
280 aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,
281 areq->first_rsgl.sgl.sg, used, ctx->iv);
282 aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
283 aead_request_set_tfm(&areq->cra_u.aead_req, tfm);
284
285 if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
286 /* AIO operation */
287 sock_hold(sk);
288 areq->iocb = msg->msg_iocb;
289
290 /* Remember output size that will be generated. */
291 areq->outlen = outlen;
292
293 aead_request_set_callback(&areq->cra_u.aead_req,
294 CRYPTO_TFM_REQ_MAY_BACKLOG,
295 af_alg_async_cb, areq);
296 err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
297 crypto_aead_decrypt(&areq->cra_u.aead_req);
298
299 /* AIO operation in progress */
300 if (err == -EINPROGRESS || err == -EBUSY)
301 return -EIOCBQUEUED;
302
303 sock_put(sk);
304 } else {
305 /* Synchronous operation */
306 aead_request_set_callback(&areq->cra_u.aead_req,
307 CRYPTO_TFM_REQ_MAY_BACKLOG,
308 crypto_req_done, &ctx->wait);
309 err = crypto_wait_req(ctx->enc ?
310 crypto_aead_encrypt(&areq->cra_u.aead_req) :
311 crypto_aead_decrypt(&areq->cra_u.aead_req),
312 &ctx->wait);
313 }
314
315
316 free:
317 af_alg_free_resources(areq);
318
319 return err ? err : outlen;
320 }
321
aead_recvmsg(struct socket * sock,struct msghdr * msg,size_t ignored,int flags)322 static int aead_recvmsg(struct socket *sock, struct msghdr *msg,
323 size_t ignored, int flags)
324 {
325 struct sock *sk = sock->sk;
326 int ret = 0;
327
328 lock_sock(sk);
329 while (msg_data_left(msg)) {
330 int err = _aead_recvmsg(sock, msg, ignored, flags);
331
332 /*
333 * This error covers -EIOCBQUEUED which implies that we can
334 * only handle one AIO request. If the caller wants to have
335 * multiple AIO requests in parallel, he must make multiple
336 * separate AIO calls.
337 *
338 * Also return the error if no data has been processed so far.
339 */
340 if (err <= 0) {
341 if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)
342 ret = err;
343 goto out;
344 }
345
346 ret += err;
347 }
348
349 out:
350 af_alg_wmem_wakeup(sk);
351 release_sock(sk);
352 return ret;
353 }
354
355 static struct proto_ops algif_aead_ops = {
356 .family = PF_ALG,
357
358 .connect = sock_no_connect,
359 .socketpair = sock_no_socketpair,
360 .getname = sock_no_getname,
361 .ioctl = sock_no_ioctl,
362 .listen = sock_no_listen,
363 .shutdown = sock_no_shutdown,
364 .getsockopt = sock_no_getsockopt,
365 .mmap = sock_no_mmap,
366 .bind = sock_no_bind,
367 .accept = sock_no_accept,
368 .setsockopt = sock_no_setsockopt,
369
370 .release = af_alg_release,
371 .sendmsg = aead_sendmsg,
372 .sendpage = af_alg_sendpage,
373 .recvmsg = aead_recvmsg,
374 .poll = af_alg_poll,
375 };
376
aead_check_key(struct socket * sock)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 (ask->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 if (!pask->refcnt++)
400 sock_hold(psk);
401
402 ask->refcnt = 1;
403 sock_put(psk);
404
405 err = 0;
406
407 unlock:
408 release_sock(psk);
409 unlock_child:
410 release_sock(sk);
411
412 return err;
413 }
414
aead_sendmsg_nokey(struct socket * sock,struct msghdr * msg,size_t size)415 static int aead_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
416 size_t size)
417 {
418 int err;
419
420 err = aead_check_key(sock);
421 if (err)
422 return err;
423
424 return aead_sendmsg(sock, msg, size);
425 }
426
aead_sendpage_nokey(struct socket * sock,struct page * page,int offset,size_t size,int flags)427 static ssize_t aead_sendpage_nokey(struct socket *sock, struct page *page,
428 int offset, size_t size, int flags)
429 {
430 int err;
431
432 err = aead_check_key(sock);
433 if (err)
434 return err;
435
436 return af_alg_sendpage(sock, page, offset, size, flags);
437 }
438
aead_recvmsg_nokey(struct socket * sock,struct msghdr * msg,size_t ignored,int flags)439 static int aead_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
440 size_t ignored, int flags)
441 {
442 int err;
443
444 err = aead_check_key(sock);
445 if (err)
446 return err;
447
448 return aead_recvmsg(sock, msg, ignored, flags);
449 }
450
451 static struct proto_ops algif_aead_ops_nokey = {
452 .family = PF_ALG,
453
454 .connect = sock_no_connect,
455 .socketpair = sock_no_socketpair,
456 .getname = sock_no_getname,
457 .ioctl = sock_no_ioctl,
458 .listen = sock_no_listen,
459 .shutdown = sock_no_shutdown,
460 .getsockopt = sock_no_getsockopt,
461 .mmap = sock_no_mmap,
462 .bind = sock_no_bind,
463 .accept = sock_no_accept,
464 .setsockopt = sock_no_setsockopt,
465
466 .release = af_alg_release,
467 .sendmsg = aead_sendmsg_nokey,
468 .sendpage = aead_sendpage_nokey,
469 .recvmsg = aead_recvmsg_nokey,
470 .poll = af_alg_poll,
471 };
472
aead_bind(const char * name,u32 type,u32 mask)473 static void *aead_bind(const char *name, u32 type, u32 mask)
474 {
475 struct aead_tfm *tfm;
476 struct crypto_aead *aead;
477 struct crypto_sync_skcipher *null_tfm;
478
479 tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
480 if (!tfm)
481 return ERR_PTR(-ENOMEM);
482
483 aead = crypto_alloc_aead(name, type, mask);
484 if (IS_ERR(aead)) {
485 kfree(tfm);
486 return ERR_CAST(aead);
487 }
488
489 null_tfm = crypto_get_default_null_skcipher();
490 if (IS_ERR(null_tfm)) {
491 crypto_free_aead(aead);
492 kfree(tfm);
493 return ERR_CAST(null_tfm);
494 }
495
496 tfm->aead = aead;
497 tfm->null_tfm = null_tfm;
498
499 return tfm;
500 }
501
aead_release(void * private)502 static void aead_release(void *private)
503 {
504 struct aead_tfm *tfm = private;
505
506 crypto_free_aead(tfm->aead);
507 crypto_put_default_null_skcipher();
508 kfree(tfm);
509 }
510
aead_setauthsize(void * private,unsigned int authsize)511 static int aead_setauthsize(void *private, unsigned int authsize)
512 {
513 struct aead_tfm *tfm = private;
514
515 return crypto_aead_setauthsize(tfm->aead, authsize);
516 }
517
aead_setkey(void * private,const u8 * key,unsigned int keylen)518 static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
519 {
520 struct aead_tfm *tfm = private;
521
522 return crypto_aead_setkey(tfm->aead, key, keylen);
523 }
524
aead_sock_destruct(struct sock * sk)525 static void aead_sock_destruct(struct sock *sk)
526 {
527 struct alg_sock *ask = alg_sk(sk);
528 struct af_alg_ctx *ctx = ask->private;
529 struct sock *psk = ask->parent;
530 struct alg_sock *pask = alg_sk(psk);
531 struct aead_tfm *aeadc = pask->private;
532 struct crypto_aead *tfm = aeadc->aead;
533 unsigned int ivlen = crypto_aead_ivsize(tfm);
534
535 af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
536 sock_kzfree_s(sk, ctx->iv, ivlen);
537 sock_kfree_s(sk, ctx, ctx->len);
538 af_alg_release_parent(sk);
539 }
540
aead_accept_parent_nokey(void * private,struct sock * sk)541 static int aead_accept_parent_nokey(void *private, struct sock *sk)
542 {
543 struct af_alg_ctx *ctx;
544 struct alg_sock *ask = alg_sk(sk);
545 struct aead_tfm *tfm = private;
546 struct crypto_aead *aead = tfm->aead;
547 unsigned int len = sizeof(*ctx);
548 unsigned int ivlen = crypto_aead_ivsize(aead);
549
550 ctx = sock_kmalloc(sk, len, GFP_KERNEL);
551 if (!ctx)
552 return -ENOMEM;
553 memset(ctx, 0, len);
554
555 ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
556 if (!ctx->iv) {
557 sock_kfree_s(sk, ctx, len);
558 return -ENOMEM;
559 }
560 memset(ctx->iv, 0, ivlen);
561
562 INIT_LIST_HEAD(&ctx->tsgl_list);
563 ctx->len = len;
564 ctx->used = 0;
565 atomic_set(&ctx->rcvused, 0);
566 ctx->more = 0;
567 ctx->merge = 0;
568 ctx->enc = 0;
569 ctx->aead_assoclen = 0;
570 crypto_init_wait(&ctx->wait);
571
572 ask->private = ctx;
573
574 sk->sk_destruct = aead_sock_destruct;
575
576 return 0;
577 }
578
aead_accept_parent(void * private,struct sock * sk)579 static int aead_accept_parent(void *private, struct sock *sk)
580 {
581 struct aead_tfm *tfm = private;
582
583 if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
584 return -ENOKEY;
585
586 return aead_accept_parent_nokey(private, sk);
587 }
588
589 static const struct af_alg_type algif_type_aead = {
590 .bind = aead_bind,
591 .release = aead_release,
592 .setkey = aead_setkey,
593 .setauthsize = aead_setauthsize,
594 .accept = aead_accept_parent,
595 .accept_nokey = aead_accept_parent_nokey,
596 .ops = &algif_aead_ops,
597 .ops_nokey = &algif_aead_ops_nokey,
598 .name = "aead",
599 .owner = THIS_MODULE
600 };
601
algif_aead_init(void)602 static int __init algif_aead_init(void)
603 {
604 return af_alg_register_type(&algif_type_aead);
605 }
606
algif_aead_exit(void)607 static void __exit algif_aead_exit(void)
608 {
609 int err = af_alg_unregister_type(&algif_type_aead);
610 BUG_ON(err);
611 }
612
613 module_init(algif_aead_init);
614 module_exit(algif_aead_exit);
615 MODULE_LICENSE("GPL");
616 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
617 MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");
618