crypto/algif_aead.c

   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
  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/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          * 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_SLEEP,
 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)
 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_SLEEP |
 308                                           CRYPTO_TFM_REQ_MAY_BACKLOG,
 309                                           crypto_req_done, &ctx->wait);
 310                 err = crypto_wait_req(ctx->enc ?
 311                                 crypto_aead_encrypt(&areq->cra_u.aead_req) :
 312                                 crypto_aead_decrypt(&areq->cra_u.aead_req),
 313                                 &ctx->wait);
 314         }
 315
 316
 317 free:
 318         af_alg_free_resources(areq);
 319
 320         return err ? err : outlen;
 321 }
 322
 323 static int aead_recvmsg(struct socket *sock, struct msghdr *msg,
 324                         size_t ignored, int flags)
 325 {
 326         struct sock *sk = sock->sk;
 327         int ret = 0;
 328
 329         lock_sock(sk);
 330         while (msg_data_left(msg)) {
 331                 int err = _aead_recvmsg(sock, msg, ignored, flags);
 332
 333                 /*
 334                  * This error covers -EIOCBQUEUED which implies that we can
 335                  * only handle one AIO request. If the caller wants to have
 336                  * multiple AIO requests in parallel, he must make multiple
 337                  * separate AIO calls.
 338                  *
 339                  * Also return the error if no data has been processed so far.
 340                  */
 341                 if (err <= 0) {
 342                         if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)
 343                                 ret = err;
 344                         goto out;
 345                 }
 346
 347                 ret += err;
 348         }
 349
 350 out:
 351         af_alg_wmem_wakeup(sk);
 352         release_sock(sk);
 353         return ret;
 354 }
 355
 356 static struct proto_ops algif_aead_ops = {
 357         .family         =       PF_ALG,
 358
 359         .connect        =       sock_no_connect,
 360         .socketpair     =       sock_no_socketpair,
 361         .getname        =       sock_no_getname,
 362         .ioctl          =       sock_no_ioctl,
 363         .listen         =       sock_no_listen,
 364         .shutdown       =       sock_no_shutdown,
 365         .mmap           =       sock_no_mmap,
 366         .bind           =       sock_no_bind,
 367         .accept         =       sock_no_accept,
 368
 369         .release        =       af_alg_release,
 370         .sendmsg        =       aead_sendmsg,
 371         .sendpage       =       af_alg_sendpage,
 372         .recvmsg        =       aead_recvmsg,
 373         .poll           =       af_alg_poll,
 374 };
 375
 376 static int aead_check_key(struct socket *sock)
 377 {
 378         int err = 0;
 379         struct sock *psk;
 380         struct alg_sock *pask;
 381         struct aead_tfm *tfm;
 382         struct sock *sk = sock->sk;
 383         struct alg_sock *ask = alg_sk(sk);
 384
 385         lock_sock(sk);
 386         if (!atomic_read(&ask->nokey_refcnt))
 387                 goto unlock_child;
 388
 389         psk = ask->parent;
 390         pask = alg_sk(ask->parent);
 391         tfm = pask->private;
 392
 393         err = -ENOKEY;
 394         lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
 395         if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
 396                 goto unlock;
 397
 398         atomic_dec(&pask->nokey_refcnt);
 399         atomic_set(&ask->nokey_refcnt, 0);
 400
 401         err = 0;
 402
 403 unlock:
 404         release_sock(psk);
 405 unlock_child:
 406         release_sock(sk);
 407
 408         return err;
 409 }
 410
 411 static int aead_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
 412                                   size_t size)
 413 {
 414         int err;
 415
 416         err = aead_check_key(sock);
 417         if (err)
 418                 return err;
 419
 420         return aead_sendmsg(sock, msg, size);
 421 }
 422
 423 static ssize_t aead_sendpage_nokey(struct socket *sock, struct page *page,
 424                                        int offset, size_t size, int flags)
 425 {
 426         int err;
 427
 428         err = aead_check_key(sock);
 429         if (err)
 430                 return err;
 431
 432         return af_alg_sendpage(sock, page, offset, size, flags);
 433 }
 434
 435 static int aead_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
 436                                   size_t ignored, int flags)
 437 {
 438         int err;
 439
 440         err = aead_check_key(sock);
 441         if (err)
 442                 return err;
 443
 444         return aead_recvmsg(sock, msg, ignored, flags);
 445 }
 446
 447 static struct proto_ops algif_aead_ops_nokey = {
 448         .family         =       PF_ALG,
 449
 450         .connect        =       sock_no_connect,
 451         .socketpair     =       sock_no_socketpair,
 452         .getname        =       sock_no_getname,
 453         .ioctl          =       sock_no_ioctl,
 454         .listen         =       sock_no_listen,
 455         .shutdown       =       sock_no_shutdown,
 456         .mmap           =       sock_no_mmap,
 457         .bind           =       sock_no_bind,
 458         .accept         =       sock_no_accept,
 459
 460         .release        =       af_alg_release,
 461         .sendmsg        =       aead_sendmsg_nokey,
 462         .sendpage       =       aead_sendpage_nokey,
 463         .recvmsg        =       aead_recvmsg_nokey,
 464         .poll           =       af_alg_poll,
 465 };
 466
 467 static void *aead_bind(const char *name, u32 type, u32 mask)
 468 {
 469         struct aead_tfm *tfm;
 470         struct crypto_aead *aead;
 471         struct crypto_sync_skcipher *null_tfm;
 472
 473         tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
 474         if (!tfm)
 475                 return ERR_PTR(-ENOMEM);
 476
 477         aead = crypto_alloc_aead(name, type, mask);
 478         if (IS_ERR(aead)) {
 479                 kfree(tfm);
 480                 return ERR_CAST(aead);
 481         }
 482
 483         null_tfm = crypto_get_default_null_skcipher();
 484         if (IS_ERR(null_tfm)) {
 485                 crypto_free_aead(aead);
 486                 kfree(tfm);
 487                 return ERR_CAST(null_tfm);
 488         }
 489
 490         tfm->aead = aead;
 491         tfm->null_tfm = null_tfm;
 492
 493         return tfm;
 494 }
 495
 496 static void aead_release(void *private)
 497 {
 498         struct aead_tfm *tfm = private;
 499
 500         crypto_free_aead(tfm->aead);
 501         crypto_put_default_null_skcipher();
 502         kfree(tfm);
 503 }
 504
 505 static int aead_setauthsize(void *private, unsigned int authsize)
 506 {
 507         struct aead_tfm *tfm = private;
 508
 509         return crypto_aead_setauthsize(tfm->aead, authsize);
 510 }
 511
 512 static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
 513 {
 514         struct aead_tfm *tfm = private;
 515
 516         return crypto_aead_setkey(tfm->aead, key, keylen);
 517 }
 518
 519 static void aead_sock_destruct(struct sock *sk)
 520 {
 521         struct alg_sock *ask = alg_sk(sk);
 522         struct af_alg_ctx *ctx = ask->private;
 523         struct sock *psk = ask->parent;
 524         struct alg_sock *pask = alg_sk(psk);
 525         struct aead_tfm *aeadc = pask->private;
 526         struct crypto_aead *tfm = aeadc->aead;
 527         unsigned int ivlen = crypto_aead_ivsize(tfm);
 528
 529         af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
 530         sock_kzfree_s(sk, ctx->iv, ivlen);
 531         sock_kfree_s(sk, ctx, ctx->len);
 532         af_alg_release_parent(sk);
 533 }
 534
 535 static int aead_accept_parent_nokey(void *private, struct sock *sk)
 536 {
 537         struct af_alg_ctx *ctx;
 538         struct alg_sock *ask = alg_sk(sk);
 539         struct aead_tfm *tfm = private;
 540         struct crypto_aead *aead = tfm->aead;
 541         unsigned int len = sizeof(*ctx);
 542         unsigned int ivlen = crypto_aead_ivsize(aead);
 543
 544         ctx = sock_kmalloc(sk, len, GFP_KERNEL);
 545         if (!ctx)
 546                 return -ENOMEM;
 547         memset(ctx, 0, len);
 548
 549         ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
 550         if (!ctx->iv) {
 551                 sock_kfree_s(sk, ctx, len);
 552                 return -ENOMEM;
 553         }
 554         memset(ctx->iv, 0, ivlen);
 555
 556         INIT_LIST_HEAD(&ctx->tsgl_list);
 557         ctx->len = len;
 558         crypto_init_wait(&ctx->wait);
 559
 560         ask->private = ctx;
 561
 562         sk->sk_destruct = aead_sock_destruct;
 563
 564         return 0;
 565 }
 566
 567 static int aead_accept_parent(void *private, struct sock *sk)
 568 {
 569         struct aead_tfm *tfm = private;
 570
 571         if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
 572                 return -ENOKEY;
 573
 574         return aead_accept_parent_nokey(private, sk);
 575 }
 576
 577 static const struct af_alg_type algif_type_aead = {
 578         .bind           =       aead_bind,
 579         .release        =       aead_release,
 580         .setkey         =       aead_setkey,
 581         .setauthsize    =       aead_setauthsize,
 582         .accept         =       aead_accept_parent,
 583         .accept_nokey   =       aead_accept_parent_nokey,
 584         .ops            =       &algif_aead_ops,
 585         .ops_nokey      =       &algif_aead_ops_nokey,
 586         .name           =       "aead",
 587         .owner          =       THIS_MODULE
 588 };
 589
 590 static int __init algif_aead_init(void)
 591 {
 592         return af_alg_register_type(&algif_type_aead);
 593 }
 594
 595 static void __exit algif_aead_exit(void)
 596 {
 597         int err = af_alg_unregister_type(&algif_type_aead);
 598         BUG_ON(err);
 599 }
 600
 601 module_init(algif_aead_init);
 602 module_exit(algif_aead_exit);
 603 MODULE_LICENSE("GPL");
 604 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
 605 MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");