crypto/algif_aead.c

   1 /*
   2  * algif_aead: User-space interface for AEAD algorithms
   3  *
   4  * Copyright (C) 2014, Stephan Mueller <smueller@chronox.de>
   5  *
   6  * This file provides the user-space API for AEAD ciphers.
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the Free
  10  * Software Foundation; either version 2 of the License, or (at your option)
  11  * any later version.
  12  *
  13  * The following concept of the memory management is used:
  14  *
  15  * The kernel maintains two SGLs, the TX SGL and the RX SGL. The TX SGL is
  16  * filled by user space with the data submitted via sendpage/sendmsg. Filling
  17  * up the TX SGL does not cause a crypto operation -- the data will only be
  18  * tracked by the kernel. Upon receipt of one recvmsg call, the caller must
  19  * provide a buffer which is tracked with the RX SGL.
  20  *
  21  * During the processing of the recvmsg operation, the cipher request is
  22  * allocated and prepared. As part of the recvmsg operation, the processed
  23  * TX buffers are extracted from the TX SGL into a separate SGL.
  24  *
  25  * After the completion of the crypto operation, the RX SGL and the cipher
  26  * request is released. The extracted TX SGL parts are released together with
  27  * the RX SGL release.
  28  */
  29
  30 #include <crypto/internal/aead.h>
  31 #include <crypto/scatterwalk.h>
  32 #include <crypto/if_alg.h>
  33 #include <crypto/skcipher.h>
  34 #include <crypto/null.h>
  35 #include <linux/init.h>
  36 #include <linux/list.h>
  37 #include <linux/kernel.h>
  38 #include <linux/mm.h>
  39 #include <linux/module.h>
  40 #include <linux/net.h>
  41 #include <net/sock.h>
  42
  43 struct aead_tfm {
  44         struct crypto_aead *aead;
  45         bool has_key;
  46         struct crypto_skcipher *null_tfm;
  47 };
  48
  49 static inline bool aead_sufficient_data(struct sock *sk)
  50 {
  51         struct alg_sock *ask = alg_sk(sk);
  52         struct sock *psk = ask->parent;
  53         struct alg_sock *pask = alg_sk(psk);
  54         struct af_alg_ctx *ctx = ask->private;
  55         struct aead_tfm *aeadc = pask->private;
  56         struct crypto_aead *tfm = aeadc->aead;
  57         unsigned int as = crypto_aead_authsize(tfm);
  58
  59         /*
  60          * The minimum amount of memory needed for an AEAD cipher is
  61          * the AAD and in case of decryption the tag.
  62          */
  63         return ctx->used >= ctx->aead_assoclen + (ctx->enc ? 0 : as);
  64 }
  65
  66 static int aead_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
  67 {
  68         struct sock *sk = sock->sk;
  69         struct alg_sock *ask = alg_sk(sk);
  70         struct sock *psk = ask->parent;
  71         struct alg_sock *pask = alg_sk(psk);
  72         struct aead_tfm *aeadc = pask->private;
  73         struct crypto_aead *tfm = aeadc->aead;
  74         unsigned int ivsize = crypto_aead_ivsize(tfm);
  75
  76         return af_alg_sendmsg(sock, msg, size, ivsize);
  77 }
  78
  79 static int crypto_aead_copy_sgl(struct crypto_skcipher *null_tfm,
  80                                 struct scatterlist *src,
  81                                 struct scatterlist *dst, unsigned int len)
  82 {
  83         SKCIPHER_REQUEST_ON_STACK(skreq, null_tfm);
  84
  85         skcipher_request_set_tfm(skreq, null_tfm);
  86         skcipher_request_set_callback(skreq, CRYPTO_TFM_REQ_MAY_BACKLOG,
  87                                       NULL, NULL);
  88         skcipher_request_set_crypt(skreq, src, dst, len, NULL);
  89
  90         return crypto_skcipher_encrypt(skreq);
  91 }
  92
  93 static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
  94                          size_t ignored, int flags)
  95 {
  96         struct sock *sk = sock->sk;
  97         struct alg_sock *ask = alg_sk(sk);
  98         struct sock *psk = ask->parent;
  99         struct alg_sock *pask = alg_sk(psk);
 100         struct af_alg_ctx *ctx = ask->private;
 101         struct aead_tfm *aeadc = pask->private;
 102         struct crypto_aead *tfm = aeadc->aead;
 103         struct crypto_skcipher *null_tfm = aeadc->null_tfm;
 104         unsigned int i, as = crypto_aead_authsize(tfm);
 105         struct af_alg_async_req *areq;
 106         struct af_alg_tsgl *tsgl, *tmp;
 107         struct scatterlist *rsgl_src, *tsgl_src = NULL;
 108         int err = 0;
 109         size_t used = 0;                /* [in]  TX bufs to be en/decrypted */
 110         size_t outlen = 0;              /* [out] RX bufs produced by kernel */
 111         size_t usedpages = 0;           /* [in]  RX bufs to be used from user */
 112         size_t processed = 0;           /* [in]  TX bufs to be consumed */
 113
 114         /*
 115          * Data length provided by caller via sendmsg/sendpage that has not
 116          * yet been processed.
 117          */
 118         used = ctx->used;
 119
 120         /*
 121          * Make sure sufficient data is present -- note, the same check is
 122          * is also present in sendmsg/sendpage. The checks in sendpage/sendmsg
 123          * shall provide an information to the data sender that something is
 124          * wrong, but they are irrelevant to maintain the kernel integrity.
 125          * We need this check here too in case user space decides to not honor
 126          * the error message in sendmsg/sendpage and still call recvmsg. This
 127          * check here protects the kernel integrity.
 128          */
 129         if (!aead_sufficient_data(sk))
 130                 return -EINVAL;
 131
 132         /*
 133          * Calculate the minimum output buffer size holding the result of the
 134          * cipher operation. When encrypting data, the receiving buffer is
 135          * larger by the tag length compared to the input buffer as the
 136          * encryption operation generates the tag. For decryption, the input
 137          * buffer provides the tag which is consumed resulting in only the
 138          * plaintext without a buffer for the tag returned to the caller.
 139          */
 140         if (ctx->enc)
 141                 outlen = used + as;
 142         else
 143                 outlen = used - as;
 144
 145         /*
 146          * The cipher operation input data is reduced by the associated data
 147          * length as this data is processed separately later on.
 148          */
 149         used -= ctx->aead_assoclen;
 150
 151         /* Allocate cipher request for current operation. */
 152         areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
 153                                      crypto_aead_reqsize(tfm));
 154         if (IS_ERR(areq))
 155                 return PTR_ERR(areq);
 156
 157         /* convert iovecs of output buffers into RX SGL */
 158         err = af_alg_get_rsgl(sk, msg, flags, areq, outlen, &usedpages);
 159         if (err)
 160                 goto free;
 161
 162         /*
 163          * Ensure output buffer is sufficiently large. If the caller provides
 164          * less buffer space, only use the relative required input size. This
 165          * allows AIO operation where the caller sent all data to be processed
 166          * and the AIO operation performs the operation on the different chunks
 167          * of the input data.
 168          */
 169         if (usedpages < outlen) {
 170                 size_t less = outlen - usedpages;
 171
 172                 if (used < less) {
 173                         err = -EINVAL;
 174                         goto free;
 175                 }
 176                 used -= less;
 177                 outlen -= less;
 178         }
 179
 180         processed = used + ctx->aead_assoclen;
 181         list_for_each_entry_safe(tsgl, tmp, &ctx->tsgl_list, list) {
 182                 for (i = 0; i < tsgl->cur; i++) {
 183                         struct scatterlist *process_sg = tsgl->sg + i;
 184
 185                         if (!(process_sg->length) || !sg_page(process_sg))
 186                                 continue;
 187                         tsgl_src = process_sg;
 188                         break;
 189                 }
 190                 if (tsgl_src)
 191                         break;
 192         }
 193         if (processed && !tsgl_src) {
 194                 err = -EFAULT;
 195                 goto free;
 196         }
 197
 198         /*
 199          * Copy of AAD from source to destination
 200          *
 201          * The AAD is copied to the destination buffer without change. Even
 202          * when user space uses an in-place cipher operation, the kernel
 203          * will copy the data as it does not see whether such in-place operation
 204          * is initiated.
 205          *
 206          * To ensure efficiency, the following implementation ensure that the
 207          * ciphers are invoked to perform a crypto operation in-place. This
 208          * is achieved by memory management specified as follows.
 209          */
 210
 211         /* Use the RX SGL as source (and destination) for crypto op. */
 212         rsgl_src = areq->first_rsgl.sgl.sg;
 213
 214         if (ctx->enc) {
 215                 /*
 216                  * Encryption operation - The in-place cipher operation is
 217                  * achieved by the following operation:
 218                  *
 219                  * TX SGL: AAD || PT
 220                  *          |      |
 221                  *          | copy |
 222                  *          v      v
 223                  * RX SGL: AAD || PT || Tag
 224                  */
 225                 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
 226                                            areq->first_rsgl.sgl.sg, processed);
 227                 if (err)
 228                         goto free;
 229                 af_alg_pull_tsgl(sk, processed, NULL, 0);
 230         } else {
 231                 /*
 232                  * Decryption operation - To achieve an in-place cipher
 233                  * operation, the following  SGL structure is used:
 234                  *
 235                  * TX SGL: AAD || CT || Tag
 236                  *          |      |     ^
 237                  *          | copy |     | Create SGL link.
 238                  *          v      v     |
 239                  * RX SGL: AAD || CT ----+
 240                  */
 241
 242                  /* Copy AAD || CT to RX SGL buffer for in-place operation. */
 243                 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
 244                                            areq->first_rsgl.sgl.sg, outlen);
 245                 if (err)
 246                         goto free;
 247
 248                 /* Create TX SGL for tag and chain it to RX SGL. */
 249                 areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
 250                                                        processed - as);
 251                 if (!areq->tsgl_entries)
 252                         areq->tsgl_entries = 1;
 253                 areq->tsgl = sock_kmalloc(sk, sizeof(*areq->tsgl) *
 254                                               areq->tsgl_entries,
 255                                           GFP_KERNEL);
 256                 if (!areq->tsgl) {
 257                         err = -ENOMEM;
 258                         goto free;
 259                 }
 260                 sg_init_table(areq->tsgl, areq->tsgl_entries);
 261
 262                 /* Release TX SGL, except for tag data and reassign tag data. */
 263                 af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);
 264
 265                 /* chain the areq TX SGL holding the tag with RX SGL */
 266                 if (usedpages) {
 267                         /* RX SGL present */
 268                         struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;
 269
 270                         sg_unmark_end(sgl_prev->sg + sgl_prev->npages - 1);
 271                         sg_chain(sgl_prev->sg, sgl_prev->npages + 1,
 272                                  areq->tsgl);
 273                 } else
 274                         /* no RX SGL present (e.g. authentication only) */
 275                         rsgl_src = areq->tsgl;
 276         }
 277
 278         /* Initialize the crypto operation */
 279         aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,
 280                                areq->first_rsgl.sgl.sg, used, ctx->iv);
 281         aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
 282         aead_request_set_tfm(&areq->cra_u.aead_req, tfm);
 283
 284         if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
 285                 /* AIO operation */
 286                 sock_hold(sk);
 287                 areq->iocb = msg->msg_iocb;
 288                 aead_request_set_callback(&areq->cra_u.aead_req,
 289                                           CRYPTO_TFM_REQ_MAY_BACKLOG,
 290                                           af_alg_async_cb, areq);
 291                 err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
 292                                  crypto_aead_decrypt(&areq->cra_u.aead_req);
 293
 294                 /* AIO operation in progress */
 295                 if (err == -EINPROGRESS || err == -EBUSY) {
 296                         /* Remember output size that will be generated. */
 297                         areq->outlen = outlen;
 298
 299                         return -EIOCBQUEUED;
 300                 }
 301
 302                 sock_put(sk);
 303         } else {
 304                 /* Synchronous operation */
 305                 aead_request_set_callback(&areq->cra_u.aead_req,
 306                                           CRYPTO_TFM_REQ_MAY_BACKLOG,
 307                                           crypto_req_done, &ctx->wait);
 308                 err = crypto_wait_req(ctx->enc ?
 309                                 crypto_aead_encrypt(&areq->cra_u.aead_req) :
 310                                 crypto_aead_decrypt(&areq->cra_u.aead_req),
 311                                 &ctx->wait);
 312         }
 313
 314
 315 free:
 316         af_alg_free_resources(areq);
 317
 318         return err ? err : outlen;
 319 }
 320
 321 static int aead_recvmsg(struct socket *sock, struct msghdr *msg,
 322                         size_t ignored, int flags)
 323 {
 324         struct sock *sk = sock->sk;
 325         int ret = 0;
 326
 327         lock_sock(sk);
 328         while (msg_data_left(msg)) {
 329                 int err = _aead_recvmsg(sock, msg, ignored, flags);
 330
 331                 /*
 332                  * This error covers -EIOCBQUEUED which implies that we can
 333                  * only handle one AIO request. If the caller wants to have
 334                  * multiple AIO requests in parallel, he must make multiple
 335                  * separate AIO calls.
 336                  *
 337                  * Also return the error if no data has been processed so far.
 338                  */
 339                 if (err <= 0) {
 340                         if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)
 341                                 ret = err;
 342                         goto out;
 343                 }
 344
 345                 ret += err;
 346         }
 347
 348 out:
 349         af_alg_wmem_wakeup(sk);
 350         release_sock(sk);
 351         return ret;
 352 }
 353
 354 static struct proto_ops algif_aead_ops = {
 355         .family         =       PF_ALG,
 356
 357         .connect        =       sock_no_connect,
 358         .socketpair     =       sock_no_socketpair,
 359         .getname        =       sock_no_getname,
 360         .ioctl          =       sock_no_ioctl,
 361         .listen         =       sock_no_listen,
 362         .shutdown       =       sock_no_shutdown,
 363         .getsockopt     =       sock_no_getsockopt,
 364         .mmap           =       sock_no_mmap,
 365         .bind           =       sock_no_bind,
 366         .accept         =       sock_no_accept,
 367         .setsockopt     =       sock_no_setsockopt,
 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 (ask->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 (!tfm->has_key)
 396                 goto unlock;
 397
 398         if (!pask->refcnt++)
 399                 sock_hold(psk);
 400
 401         ask->refcnt = 1;
 402         sock_put(psk);
 403
 404         err = 0;
 405
 406 unlock:
 407         release_sock(psk);
 408 unlock_child:
 409         release_sock(sk);
 410
 411         return err;
 412 }
 413
 414 static int aead_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
 415                                   size_t size)
 416 {
 417         int err;
 418
 419         err = aead_check_key(sock);
 420         if (err)
 421                 return err;
 422
 423         return aead_sendmsg(sock, msg, size);
 424 }
 425
 426 static ssize_t aead_sendpage_nokey(struct socket *sock, struct page *page,
 427                                        int offset, size_t size, int flags)
 428 {
 429         int err;
 430
 431         err = aead_check_key(sock);
 432         if (err)
 433                 return err;
 434
 435         return af_alg_sendpage(sock, page, offset, size, flags);
 436 }
 437
 438 static int aead_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
 439                                   size_t ignored, int flags)
 440 {
 441         int err;
 442
 443         err = aead_check_key(sock);
 444         if (err)
 445                 return err;
 446
 447         return aead_recvmsg(sock, msg, ignored, flags);
 448 }
 449
 450 static struct proto_ops algif_aead_ops_nokey = {
 451         .family         =       PF_ALG,
 452
 453         .connect        =       sock_no_connect,
 454         .socketpair     =       sock_no_socketpair,
 455         .getname        =       sock_no_getname,
 456         .ioctl          =       sock_no_ioctl,
 457         .listen         =       sock_no_listen,
 458         .shutdown       =       sock_no_shutdown,
 459         .getsockopt     =       sock_no_getsockopt,
 460         .mmap           =       sock_no_mmap,
 461         .bind           =       sock_no_bind,
 462         .accept         =       sock_no_accept,
 463         .setsockopt     =       sock_no_setsockopt,
 464
 465         .release        =       af_alg_release,
 466         .sendmsg        =       aead_sendmsg_nokey,
 467         .sendpage       =       aead_sendpage_nokey,
 468         .recvmsg        =       aead_recvmsg_nokey,
 469         .poll           =       af_alg_poll,
 470 };
 471
 472 static void *aead_bind(const char *name, u32 type, u32 mask)
 473 {
 474         struct aead_tfm *tfm;
 475         struct crypto_aead *aead;
 476         struct crypto_skcipher *null_tfm;
 477
 478         tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
 479         if (!tfm)
 480                 return ERR_PTR(-ENOMEM);
 481
 482         aead = crypto_alloc_aead(name, type, mask);
 483         if (IS_ERR(aead)) {
 484                 kfree(tfm);
 485                 return ERR_CAST(aead);
 486         }
 487
 488         null_tfm = crypto_get_default_null_skcipher2();
 489         if (IS_ERR(null_tfm)) {
 490                 crypto_free_aead(aead);
 491                 kfree(tfm);
 492                 return ERR_CAST(null_tfm);
 493         }
 494
 495         tfm->aead = aead;
 496         tfm->null_tfm = null_tfm;
 497
 498         return tfm;
 499 }
 500
 501 static void aead_release(void *private)
 502 {
 503         struct aead_tfm *tfm = private;
 504
 505         crypto_free_aead(tfm->aead);
 506         crypto_put_default_null_skcipher2();
 507         kfree(tfm);
 508 }
 509
 510 static int aead_setauthsize(void *private, unsigned int authsize)
 511 {
 512         struct aead_tfm *tfm = private;
 513
 514         return crypto_aead_setauthsize(tfm->aead, authsize);
 515 }
 516
 517 static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
 518 {
 519         struct aead_tfm *tfm = private;
 520         int err;
 521
 522         err = crypto_aead_setkey(tfm->aead, key, keylen);
 523         tfm->has_key = !err;
 524
 525         return err;
 526 }
 527
 528 static void aead_sock_destruct(struct sock *sk)
 529 {
 530         struct alg_sock *ask = alg_sk(sk);
 531         struct af_alg_ctx *ctx = ask->private;
 532         struct sock *psk = ask->parent;
 533         struct alg_sock *pask = alg_sk(psk);
 534         struct aead_tfm *aeadc = pask->private;
 535         struct crypto_aead *tfm = aeadc->aead;
 536         unsigned int ivlen = crypto_aead_ivsize(tfm);
 537
 538         af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
 539         sock_kzfree_s(sk, ctx->iv, ivlen);
 540         sock_kfree_s(sk, ctx, ctx->len);
 541         af_alg_release_parent(sk);
 542 }
 543
 544 static int aead_accept_parent_nokey(void *private, struct sock *sk)
 545 {
 546         struct af_alg_ctx *ctx;
 547         struct alg_sock *ask = alg_sk(sk);
 548         struct aead_tfm *tfm = private;
 549         struct crypto_aead *aead = tfm->aead;
 550         unsigned int len = sizeof(*ctx);
 551         unsigned int ivlen = crypto_aead_ivsize(aead);
 552
 553         ctx = sock_kmalloc(sk, len, GFP_KERNEL);
 554         if (!ctx)
 555                 return -ENOMEM;
 556         memset(ctx, 0, len);
 557
 558         ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
 559         if (!ctx->iv) {
 560                 sock_kfree_s(sk, ctx, len);
 561                 return -ENOMEM;
 562         }
 563         memset(ctx->iv, 0, ivlen);
 564
 565         INIT_LIST_HEAD(&ctx->tsgl_list);
 566         ctx->len = len;
 567         ctx->used = 0;
 568         ctx->rcvused = 0;
 569         ctx->more = 0;
 570         ctx->merge = 0;
 571         ctx->enc = 0;
 572         ctx->aead_assoclen = 0;
 573         crypto_init_wait(&ctx->wait);
 574
 575         ask->private = ctx;
 576
 577         sk->sk_destruct = aead_sock_destruct;
 578
 579         return 0;
 580 }
 581
 582 static int aead_accept_parent(void *private, struct sock *sk)
 583 {
 584         struct aead_tfm *tfm = private;
 585
 586         if (!tfm->has_key)
 587                 return -ENOKEY;
 588
 589         return aead_accept_parent_nokey(private, sk);
 590 }
 591
 592 static const struct af_alg_type algif_type_aead = {
 593         .bind           =       aead_bind,
 594         .release        =       aead_release,
 595         .setkey         =       aead_setkey,
 596         .setauthsize    =       aead_setauthsize,
 597         .accept         =       aead_accept_parent,
 598         .accept_nokey   =       aead_accept_parent_nokey,
 599         .ops            =       &algif_aead_ops,
 600         .ops_nokey      =       &algif_aead_ops_nokey,
 601         .name           =       "aead",
 602         .owner          =       THIS_MODULE
 603 };
 604
 605 static int __init algif_aead_init(void)
 606 {
 607         return af_alg_register_type(&algif_type_aead);
 608 }
 609
 610 static void __exit algif_aead_exit(void)
 611 {
 612         int err = af_alg_unregister_type(&algif_type_aead);
 613         BUG_ON(err);
 614 }
 615
 616 module_init(algif_aead_init);
 617 module_exit(algif_aead_exit);
 618 MODULE_LICENSE("GPL");
 619 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
 620 MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");