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         struct crypto_skcipher *null_tfm;
  46 };
  47
  48 static inline bool aead_sufficient_data(struct sock *sk)
  49 {
  50         struct alg_sock *ask = alg_sk(sk);
  51         struct sock *psk = ask->parent;
  52         struct alg_sock *pask = alg_sk(psk);
  53         struct af_alg_ctx *ctx = ask->private;
  54         struct aead_tfm *aeadc = pask->private;
  55         struct crypto_aead *tfm = aeadc->aead;
  56         unsigned int as = crypto_aead_authsize(tfm);
  57
  58         /*
  59          * The minimum amount of memory needed for an AEAD cipher is
  60          * the AAD and in case of decryption the tag.
  61          */
  62         return ctx->used >= ctx->aead_assoclen + (ctx->enc ? 0 : as);
  63 }
  64
  65 static int aead_sendmsg(struct socket *sock, struct msghdr *msg, size_t size)
  66 {
  67         struct sock *sk = sock->sk;
  68         struct alg_sock *ask = alg_sk(sk);
  69         struct sock *psk = ask->parent;
  70         struct alg_sock *pask = alg_sk(psk);
  71         struct aead_tfm *aeadc = pask->private;
  72         struct crypto_aead *tfm = aeadc->aead;
  73         unsigned int ivsize = crypto_aead_ivsize(tfm);
  74
  75         return af_alg_sendmsg(sock, msg, size, ivsize);
  76 }
  77
  78 static int crypto_aead_copy_sgl(struct crypto_skcipher *null_tfm,
  79                                 struct scatterlist *src,
  80                                 struct scatterlist *dst, unsigned int len)
  81 {
  82         SKCIPHER_REQUEST_ON_STACK(skreq, null_tfm);
  83
  84         skcipher_request_set_tfm(skreq, null_tfm);
  85         skcipher_request_set_callback(skreq, CRYPTO_TFM_REQ_MAY_BACKLOG,
  86                                       NULL, NULL);
  87         skcipher_request_set_crypt(skreq, src, dst, len, NULL);
  88
  89         return crypto_skcipher_encrypt(skreq);
  90 }
  91
  92 static int _aead_recvmsg(struct socket *sock, struct msghdr *msg,
  93                          size_t ignored, int flags)
  94 {
  95         struct sock *sk = sock->sk;
  96         struct alg_sock *ask = alg_sk(sk);
  97         struct sock *psk = ask->parent;
  98         struct alg_sock *pask = alg_sk(psk);
  99         struct af_alg_ctx *ctx = ask->private;
 100         struct aead_tfm *aeadc = pask->private;
 101         struct crypto_aead *tfm = aeadc->aead;
 102         struct crypto_skcipher *null_tfm = aeadc->null_tfm;
 103         unsigned int i, as = crypto_aead_authsize(tfm);
 104         struct af_alg_async_req *areq;
 105         struct af_alg_tsgl *tsgl, *tmp;
 106         struct scatterlist *rsgl_src, *tsgl_src = NULL;
 107         int err = 0;
 108         size_t used = 0;                /* [in]  TX bufs to be en/decrypted */
 109         size_t outlen = 0;              /* [out] RX bufs produced by kernel */
 110         size_t usedpages = 0;           /* [in]  RX bufs to be used from user */
 111         size_t processed = 0;           /* [in]  TX bufs to be consumed */
 112
 113         if (!ctx->used) {
 114                 err = af_alg_wait_for_data(sk, flags);
 115                 if (err)
 116                         return err;
 117         }
 118
 119         /*
 120          * Data length provided by caller via sendmsg/sendpage that has not
 121          * yet been processed.
 122          */
 123         used = ctx->used;
 124
 125         /*
 126          * Make sure sufficient data is present -- note, the same check is
 127          * is also present in sendmsg/sendpage. The checks in sendpage/sendmsg
 128          * shall provide an information to the data sender that something is
 129          * wrong, but they are irrelevant to maintain the kernel integrity.
 130          * We need this check here too in case user space decides to not honor
 131          * the error message in sendmsg/sendpage and still call recvmsg. This
 132          * check here protects the kernel integrity.
 133          */
 134         if (!aead_sufficient_data(sk))
 135                 return -EINVAL;
 136
 137         /*
 138          * Calculate the minimum output buffer size holding the result of the
 139          * cipher operation. When encrypting data, the receiving buffer is
 140          * larger by the tag length compared to the input buffer as the
 141          * encryption operation generates the tag. For decryption, the input
 142          * buffer provides the tag which is consumed resulting in only the
 143          * plaintext without a buffer for the tag returned to the caller.
 144          */
 145         if (ctx->enc)
 146                 outlen = used + as;
 147         else
 148                 outlen = used - as;
 149
 150         /*
 151          * The cipher operation input data is reduced by the associated data
 152          * length as this data is processed separately later on.
 153          */
 154         used -= ctx->aead_assoclen;
 155
 156         /* Allocate cipher request for current operation. */
 157         areq = af_alg_alloc_areq(sk, sizeof(struct af_alg_async_req) +
 158                                      crypto_aead_reqsize(tfm));
 159         if (IS_ERR(areq))
 160                 return PTR_ERR(areq);
 161
 162         /* convert iovecs of output buffers into RX SGL */
 163         err = af_alg_get_rsgl(sk, msg, flags, areq, outlen, &usedpages);
 164         if (err)
 165                 goto free;
 166
 167         /*
 168          * Ensure output buffer is sufficiently large. If the caller provides
 169          * less buffer space, only use the relative required input size. This
 170          * allows AIO operation where the caller sent all data to be processed
 171          * and the AIO operation performs the operation on the different chunks
 172          * of the input data.
 173          */
 174         if (usedpages < outlen) {
 175                 size_t less = outlen - usedpages;
 176
 177                 if (used < less) {
 178                         err = -EINVAL;
 179                         goto free;
 180                 }
 181                 used -= less;
 182                 outlen -= less;
 183         }
 184
 185         processed = used + ctx->aead_assoclen;
 186         list_for_each_entry_safe(tsgl, tmp, &ctx->tsgl_list, list) {
 187                 for (i = 0; i < tsgl->cur; i++) {
 188                         struct scatterlist *process_sg = tsgl->sg + i;
 189
 190                         if (!(process_sg->length) || !sg_page(process_sg))
 191                                 continue;
 192                         tsgl_src = process_sg;
 193                         break;
 194                 }
 195                 if (tsgl_src)
 196                         break;
 197         }
 198         if (processed && !tsgl_src) {
 199                 err = -EFAULT;
 200                 goto free;
 201         }
 202
 203         /*
 204          * Copy of AAD from source to destination
 205          *
 206          * The AAD is copied to the destination buffer without change. Even
 207          * when user space uses an in-place cipher operation, the kernel
 208          * will copy the data as it does not see whether such in-place operation
 209          * is initiated.
 210          *
 211          * To ensure efficiency, the following implementation ensure that the
 212          * ciphers are invoked to perform a crypto operation in-place. This
 213          * is achieved by memory management specified as follows.
 214          */
 215
 216         /* Use the RX SGL as source (and destination) for crypto op. */
 217         rsgl_src = areq->first_rsgl.sgl.sg;
 218
 219         if (ctx->enc) {
 220                 /*
 221                  * Encryption operation - The in-place cipher operation is
 222                  * achieved by the following operation:
 223                  *
 224                  * TX SGL: AAD || PT
 225                  *          |      |
 226                  *          | copy |
 227                  *          v      v
 228                  * RX SGL: AAD || PT || Tag
 229                  */
 230                 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
 231                                            areq->first_rsgl.sgl.sg, processed);
 232                 if (err)
 233                         goto free;
 234                 af_alg_pull_tsgl(sk, processed, NULL, 0);
 235         } else {
 236                 /*
 237                  * Decryption operation - To achieve an in-place cipher
 238                  * operation, the following  SGL structure is used:
 239                  *
 240                  * TX SGL: AAD || CT || Tag
 241                  *          |      |     ^
 242                  *          | copy |     | Create SGL link.
 243                  *          v      v     |
 244                  * RX SGL: AAD || CT ----+
 245                  */
 246
 247                  /* Copy AAD || CT to RX SGL buffer for in-place operation. */
 248                 err = crypto_aead_copy_sgl(null_tfm, tsgl_src,
 249                                            areq->first_rsgl.sgl.sg, outlen);
 250                 if (err)
 251                         goto free;
 252
 253                 /* Create TX SGL for tag and chain it to RX SGL. */
 254                 areq->tsgl_entries = af_alg_count_tsgl(sk, processed,
 255                                                        processed - as);
 256                 if (!areq->tsgl_entries)
 257                         areq->tsgl_entries = 1;
 258                 areq->tsgl = sock_kmalloc(sk, array_size(sizeof(*areq->tsgl),
 259                                                          areq->tsgl_entries),
 260                                           GFP_KERNEL);
 261                 if (!areq->tsgl) {
 262                         err = -ENOMEM;
 263                         goto free;
 264                 }
 265                 sg_init_table(areq->tsgl, areq->tsgl_entries);
 266
 267                 /* Release TX SGL, except for tag data and reassign tag data. */
 268                 af_alg_pull_tsgl(sk, processed, areq->tsgl, processed - as);
 269
 270                 /* chain the areq TX SGL holding the tag with RX SGL */
 271                 if (usedpages) {
 272                         /* RX SGL present */
 273                         struct af_alg_sgl *sgl_prev = &areq->last_rsgl->sgl;
 274
 275                         sg_unmark_end(sgl_prev->sg + sgl_prev->npages - 1);
 276                         sg_chain(sgl_prev->sg, sgl_prev->npages + 1,
 277                                  areq->tsgl);
 278                 } else
 279                         /* no RX SGL present (e.g. authentication only) */
 280                         rsgl_src = areq->tsgl;
 281         }
 282
 283         /* Initialize the crypto operation */
 284         aead_request_set_crypt(&areq->cra_u.aead_req, rsgl_src,
 285                                areq->first_rsgl.sgl.sg, used, ctx->iv);
 286         aead_request_set_ad(&areq->cra_u.aead_req, ctx->aead_assoclen);
 287         aead_request_set_tfm(&areq->cra_u.aead_req, tfm);
 288
 289         if (msg->msg_iocb && !is_sync_kiocb(msg->msg_iocb)) {
 290                 /* AIO operation */
 291                 sock_hold(sk);
 292                 areq->iocb = msg->msg_iocb;
 293
 294                 /* Remember output size that will be generated. */
 295                 areq->outlen = outlen;
 296
 297                 aead_request_set_callback(&areq->cra_u.aead_req,
 298                                           CRYPTO_TFM_REQ_MAY_BACKLOG,
 299                                           af_alg_async_cb, areq);
 300                 err = ctx->enc ? crypto_aead_encrypt(&areq->cra_u.aead_req) :
 301                                  crypto_aead_decrypt(&areq->cra_u.aead_req);
 302
 303                 /* AIO operation in progress */
 304                 if (err == -EINPROGRESS || err == -EBUSY)
 305                         return -EIOCBQUEUED;
 306
 307                 sock_put(sk);
 308         } else {
 309                 /* Synchronous operation */
 310                 aead_request_set_callback(&areq->cra_u.aead_req,
 311                                           CRYPTO_TFM_REQ_MAY_BACKLOG,
 312                                           crypto_req_done, &ctx->wait);
 313                 err = crypto_wait_req(ctx->enc ?
 314                                 crypto_aead_encrypt(&areq->cra_u.aead_req) :
 315                                 crypto_aead_decrypt(&areq->cra_u.aead_req),
 316                                 &ctx->wait);
 317         }
 318
 319
 320 free:
 321         af_alg_free_resources(areq);
 322
 323         return err ? err : outlen;
 324 }
 325
 326 static int aead_recvmsg(struct socket *sock, struct msghdr *msg,
 327                         size_t ignored, int flags)
 328 {
 329         struct sock *sk = sock->sk;
 330         int ret = 0;
 331
 332         lock_sock(sk);
 333         while (msg_data_left(msg)) {
 334                 int err = _aead_recvmsg(sock, msg, ignored, flags);
 335
 336                 /*
 337                  * This error covers -EIOCBQUEUED which implies that we can
 338                  * only handle one AIO request. If the caller wants to have
 339                  * multiple AIO requests in parallel, he must make multiple
 340                  * separate AIO calls.
 341                  *
 342                  * Also return the error if no data has been processed so far.
 343                  */
 344                 if (err <= 0) {
 345                         if (err == -EIOCBQUEUED || err == -EBADMSG || !ret)
 346                                 ret = err;
 347                         goto out;
 348                 }
 349
 350                 ret += err;
 351         }
 352
 353 out:
 354         af_alg_wmem_wakeup(sk);
 355         release_sock(sk);
 356         return ret;
 357 }
 358
 359 static struct proto_ops algif_aead_ops = {
 360         .family         =       PF_ALG,
 361
 362         .connect        =       sock_no_connect,
 363         .socketpair     =       sock_no_socketpair,
 364         .getname        =       sock_no_getname,
 365         .ioctl          =       sock_no_ioctl,
 366         .listen         =       sock_no_listen,
 367         .shutdown       =       sock_no_shutdown,
 368         .getsockopt     =       sock_no_getsockopt,
 369         .mmap           =       sock_no_mmap,
 370         .bind           =       sock_no_bind,
 371         .accept         =       sock_no_accept,
 372         .setsockopt     =       sock_no_setsockopt,
 373
 374         .release        =       af_alg_release,
 375         .sendmsg        =       aead_sendmsg,
 376         .sendpage       =       af_alg_sendpage,
 377         .recvmsg        =       aead_recvmsg,
 378         .poll           =       af_alg_poll,
 379 };
 380
 381 static int aead_check_key(struct socket *sock)
 382 {
 383         int err = 0;
 384         struct sock *psk;
 385         struct alg_sock *pask;
 386         struct aead_tfm *tfm;
 387         struct sock *sk = sock->sk;
 388         struct alg_sock *ask = alg_sk(sk);
 389
 390         lock_sock(sk);
 391         if (!atomic_read(&ask->nokey_refcnt))
 392                 goto unlock_child;
 393
 394         psk = ask->parent;
 395         pask = alg_sk(ask->parent);
 396         tfm = pask->private;
 397
 398         err = -ENOKEY;
 399         lock_sock_nested(psk, SINGLE_DEPTH_NESTING);
 400         if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
 401                 goto unlock;
 402
 403         atomic_dec(&pask->nokey_refcnt);
 404         atomic_set(&ask->nokey_refcnt, 0);
 405
 406         err = 0;
 407
 408 unlock:
 409         release_sock(psk);
 410 unlock_child:
 411         release_sock(sk);
 412
 413         return err;
 414 }
 415
 416 static int aead_sendmsg_nokey(struct socket *sock, struct msghdr *msg,
 417                                   size_t size)
 418 {
 419         int err;
 420
 421         err = aead_check_key(sock);
 422         if (err)
 423                 return err;
 424
 425         return aead_sendmsg(sock, msg, size);
 426 }
 427
 428 static ssize_t aead_sendpage_nokey(struct socket *sock, struct page *page,
 429                                        int offset, size_t size, int flags)
 430 {
 431         int err;
 432
 433         err = aead_check_key(sock);
 434         if (err)
 435                 return err;
 436
 437         return af_alg_sendpage(sock, page, offset, size, flags);
 438 }
 439
 440 static int aead_recvmsg_nokey(struct socket *sock, struct msghdr *msg,
 441                                   size_t ignored, int flags)
 442 {
 443         int err;
 444
 445         err = aead_check_key(sock);
 446         if (err)
 447                 return err;
 448
 449         return aead_recvmsg(sock, msg, ignored, flags);
 450 }
 451
 452 static struct proto_ops algif_aead_ops_nokey = {
 453         .family         =       PF_ALG,
 454
 455         .connect        =       sock_no_connect,
 456         .socketpair     =       sock_no_socketpair,
 457         .getname        =       sock_no_getname,
 458         .ioctl          =       sock_no_ioctl,
 459         .listen         =       sock_no_listen,
 460         .shutdown       =       sock_no_shutdown,
 461         .getsockopt     =       sock_no_getsockopt,
 462         .mmap           =       sock_no_mmap,
 463         .bind           =       sock_no_bind,
 464         .accept         =       sock_no_accept,
 465         .setsockopt     =       sock_no_setsockopt,
 466
 467         .release        =       af_alg_release,
 468         .sendmsg        =       aead_sendmsg_nokey,
 469         .sendpage       =       aead_sendpage_nokey,
 470         .recvmsg        =       aead_recvmsg_nokey,
 471         .poll           =       af_alg_poll,
 472 };
 473
 474 static void *aead_bind(const char *name, u32 type, u32 mask)
 475 {
 476         struct aead_tfm *tfm;
 477         struct crypto_aead *aead;
 478         struct crypto_skcipher *null_tfm;
 479
 480         tfm = kzalloc(sizeof(*tfm), GFP_KERNEL);
 481         if (!tfm)
 482                 return ERR_PTR(-ENOMEM);
 483
 484         aead = crypto_alloc_aead(name, type, mask);
 485         if (IS_ERR(aead)) {
 486                 kfree(tfm);
 487                 return ERR_CAST(aead);
 488         }
 489
 490         null_tfm = crypto_get_default_null_skcipher();
 491         if (IS_ERR(null_tfm)) {
 492                 crypto_free_aead(aead);
 493                 kfree(tfm);
 494                 return ERR_CAST(null_tfm);
 495         }
 496
 497         tfm->aead = aead;
 498         tfm->null_tfm = null_tfm;
 499
 500         return tfm;
 501 }
 502
 503 static void aead_release(void *private)
 504 {
 505         struct aead_tfm *tfm = private;
 506
 507         crypto_free_aead(tfm->aead);
 508         crypto_put_default_null_skcipher();
 509         kfree(tfm);
 510 }
 511
 512 static int aead_setauthsize(void *private, unsigned int authsize)
 513 {
 514         struct aead_tfm *tfm = private;
 515
 516         return crypto_aead_setauthsize(tfm->aead, authsize);
 517 }
 518
 519 static int aead_setkey(void *private, const u8 *key, unsigned int keylen)
 520 {
 521         struct aead_tfm *tfm = private;
 522
 523         return crypto_aead_setkey(tfm->aead, key, keylen);
 524 }
 525
 526 static void aead_sock_destruct(struct sock *sk)
 527 {
 528         struct alg_sock *ask = alg_sk(sk);
 529         struct af_alg_ctx *ctx = ask->private;
 530         struct sock *psk = ask->parent;
 531         struct alg_sock *pask = alg_sk(psk);
 532         struct aead_tfm *aeadc = pask->private;
 533         struct crypto_aead *tfm = aeadc->aead;
 534         unsigned int ivlen = crypto_aead_ivsize(tfm);
 535
 536         af_alg_pull_tsgl(sk, ctx->used, NULL, 0);
 537         sock_kzfree_s(sk, ctx->iv, ivlen);
 538         sock_kfree_s(sk, ctx, ctx->len);
 539         af_alg_release_parent(sk);
 540 }
 541
 542 static int aead_accept_parent_nokey(void *private, struct sock *sk)
 543 {
 544         struct af_alg_ctx *ctx;
 545         struct alg_sock *ask = alg_sk(sk);
 546         struct aead_tfm *tfm = private;
 547         struct crypto_aead *aead = tfm->aead;
 548         unsigned int len = sizeof(*ctx);
 549         unsigned int ivlen = crypto_aead_ivsize(aead);
 550
 551         ctx = sock_kmalloc(sk, len, GFP_KERNEL);
 552         if (!ctx)
 553                 return -ENOMEM;
 554         memset(ctx, 0, len);
 555
 556         ctx->iv = sock_kmalloc(sk, ivlen, GFP_KERNEL);
 557         if (!ctx->iv) {
 558                 sock_kfree_s(sk, ctx, len);
 559                 return -ENOMEM;
 560         }
 561         memset(ctx->iv, 0, ivlen);
 562
 563         INIT_LIST_HEAD(&ctx->tsgl_list);
 564         ctx->len = len;
 565         ctx->used = 0;
 566         atomic_set(&ctx->rcvused, 0);
 567         ctx->more = 0;
 568         ctx->merge = 0;
 569         ctx->enc = 0;
 570         ctx->aead_assoclen = 0;
 571         crypto_init_wait(&ctx->wait);
 572
 573         ask->private = ctx;
 574
 575         sk->sk_destruct = aead_sock_destruct;
 576
 577         return 0;
 578 }
 579
 580 static int aead_accept_parent(void *private, struct sock *sk)
 581 {
 582         struct aead_tfm *tfm = private;
 583
 584         if (crypto_aead_get_flags(tfm->aead) & CRYPTO_TFM_NEED_KEY)
 585                 return -ENOKEY;
 586
 587         return aead_accept_parent_nokey(private, sk);
 588 }
 589
 590 static const struct af_alg_type algif_type_aead = {
 591         .bind           =       aead_bind,
 592         .release        =       aead_release,
 593         .setkey         =       aead_setkey,
 594         .setauthsize    =       aead_setauthsize,
 595         .accept         =       aead_accept_parent,
 596         .accept_nokey   =       aead_accept_parent_nokey,
 597         .ops            =       &algif_aead_ops,
 598         .ops_nokey      =       &algif_aead_ops_nokey,
 599         .name           =       "aead",
 600         .owner          =       THIS_MODULE
 601 };
 602
 603 static int __init algif_aead_init(void)
 604 {
 605         return af_alg_register_type(&algif_type_aead);
 606 }
 607
 608 static void __exit algif_aead_exit(void)
 609 {
 610         int err = af_alg_unregister_type(&algif_type_aead);
 611         BUG_ON(err);
 612 }
 613
 614 module_init(algif_aead_init);
 615 module_exit(algif_aead_exit);
 616 MODULE_LICENSE("GPL");
 617 MODULE_AUTHOR("Stephan Mueller <smueller@chronox.de>");
 618 MODULE_DESCRIPTION("AEAD kernel crypto API user space interface");