LXR linux/crypto/cts.c

   1/*
   2 * CTS: Cipher Text Stealing mode
   3 *
   4 * COPYRIGHT (c) 2008
   5 * The Regents of the University of Michigan
   6 * ALL RIGHTS RESERVED
   7 *
   8 * Permission is granted to use, copy, create derivative works
   9 * and redistribute this software and such derivative works
  10 * for any purpose, so long as the name of The University of
  11 * Michigan is not used in any advertising or publicity
  12 * pertaining to the use of distribution of this software
  13 * without specific, written prior authorization.  If the
  14 * above copyright notice or any other identification of the
  15 * University of Michigan is included in any copy of any
  16 * portion of this software, then the disclaimer below must
  17 * also be included.
  18 *
  19 * THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
  20 * FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
  21 * PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
  22 * MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
  23 * WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
  24 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
  25 * REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
  26 * FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
  27 * CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
  28 * OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
  29 * IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
  30 * SUCH DAMAGES.
  31 */
  32
  33/* Derived from various:
  34 *      Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
  35 */
  36
  37/*
  38 * This is the Cipher Text Stealing mode as described by
  39 * Section 8 of rfc2040 and referenced by rfc3962.
  40 * rfc3962 includes errata information in its Appendix A.
  41 */
  42
  43#include <crypto/internal/skcipher.h>
  44#include <linux/err.h>
  45#include <linux/init.h>
  46#include <linux/kernel.h>
  47#include <linux/log2.h>
  48#include <linux/module.h>
  49#include <linux/scatterlist.h>
  50#include <crypto/scatterwalk.h>
  51#include <linux/slab.h>
  52#include <linux/compiler.h>
  53
  54struct crypto_cts_ctx {
  55        struct crypto_skcipher *child;
  56};
  57
  58struct crypto_cts_reqctx {
  59        struct scatterlist sg[2];
  60        unsigned offset;
  61        struct skcipher_request subreq;
  62};
  63
  64static inline u8 *crypto_cts_reqctx_space(struct skcipher_request *req)
  65{
  66        struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
  67        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
  68        struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
  69        struct crypto_skcipher *child = ctx->child;
  70
  71        return PTR_ALIGN((u8 *)(rctx + 1) + crypto_skcipher_reqsize(child),
  72                         crypto_skcipher_alignmask(tfm) + 1);
  73}
  74
  75static int crypto_cts_setkey(struct crypto_skcipher *parent, const u8 *key,
  76                             unsigned int keylen)
  77{
  78        struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(parent);
  79        struct crypto_skcipher *child = ctx->child;
  80        int err;
  81
  82        crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  83        crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  84                                         CRYPTO_TFM_REQ_MASK);
  85        err = crypto_skcipher_setkey(child, key, keylen);
  86        crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
  87                                          CRYPTO_TFM_RES_MASK);
  88        return err;
  89}
  90
  91static void cts_cbc_crypt_done(struct crypto_async_request *areq, int err)
  92{
  93        struct skcipher_request *req = areq->data;
  94
  95        if (err == -EINPROGRESS)
  96                return;
  97
  98        skcipher_request_complete(req, err);
  99}
 100
 101static int cts_cbc_encrypt(struct skcipher_request *req)
 102{
 103        struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
 104        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 105        struct skcipher_request *subreq = &rctx->subreq;
 106        int bsize = crypto_skcipher_blocksize(tfm);
 107        u8 d[bsize * 2] __aligned(__alignof__(u32));
 108        struct scatterlist *sg;
 109        unsigned int offset;
 110        int lastn;
 111
 112        offset = rctx->offset;
 113        lastn = req->cryptlen - offset;
 114
 115        sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
 116        scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
 117
 118        memset(d, 0, bsize);
 119        scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
 120
 121        scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
 122        memzero_explicit(d, sizeof(d));
 123
 124        skcipher_request_set_callback(subreq, req->base.flags &
 125                                              CRYPTO_TFM_REQ_MAY_BACKLOG,
 126                                      cts_cbc_crypt_done, req);
 127        skcipher_request_set_crypt(subreq, sg, sg, bsize, req->iv);
 128        return crypto_skcipher_encrypt(subreq);
 129}
 130
 131static void crypto_cts_encrypt_done(struct crypto_async_request *areq, int err)
 132{
 133        struct skcipher_request *req = areq->data;
 134
 135        if (err)
 136                goto out;
 137
 138        err = cts_cbc_encrypt(req);
 139        if (err == -EINPROGRESS ||
 140            (err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
 141                return;
 142
 143out:
 144        skcipher_request_complete(req, err);
 145}
 146
 147static int crypto_cts_encrypt(struct skcipher_request *req)
 148{
 149        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 150        struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
 151        struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
 152        struct skcipher_request *subreq = &rctx->subreq;
 153        int bsize = crypto_skcipher_blocksize(tfm);
 154        unsigned int nbytes = req->cryptlen;
 155        int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
 156        unsigned int offset;
 157
 158        skcipher_request_set_tfm(subreq, ctx->child);
 159
 160        if (cbc_blocks <= 0) {
 161                skcipher_request_set_callback(subreq, req->base.flags,
 162                                              req->base.complete,
 163                                              req->base.data);
 164                skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
 165                                           req->iv);
 166                return crypto_skcipher_encrypt(subreq);
 167        }
 168
 169        offset = cbc_blocks * bsize;
 170        rctx->offset = offset;
 171
 172        skcipher_request_set_callback(subreq, req->base.flags,
 173                                      crypto_cts_encrypt_done, req);
 174        skcipher_request_set_crypt(subreq, req->src, req->dst,
 175                                   offset, req->iv);
 176
 177        return crypto_skcipher_encrypt(subreq) ?:
 178               cts_cbc_encrypt(req);
 179}
 180
 181static int cts_cbc_decrypt(struct skcipher_request *req)
 182{
 183        struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
 184        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 185        struct skcipher_request *subreq = &rctx->subreq;
 186        int bsize = crypto_skcipher_blocksize(tfm);
 187        u8 d[bsize * 2] __aligned(__alignof__(u32));
 188        struct scatterlist *sg;
 189        unsigned int offset;
 190        u8 *space;
 191        int lastn;
 192
 193        offset = rctx->offset;
 194        lastn = req->cryptlen - offset;
 195
 196        sg = scatterwalk_ffwd(rctx->sg, req->dst, offset - bsize);
 197
 198        /* 1. Decrypt Cn-1 (s) to create Dn */
 199        scatterwalk_map_and_copy(d + bsize, sg, 0, bsize, 0);
 200        space = crypto_cts_reqctx_space(req);
 201        crypto_xor(d + bsize, space, bsize);
 202        /* 2. Pad Cn with zeros at the end to create C of length BB */
 203        memset(d, 0, bsize);
 204        scatterwalk_map_and_copy(d, req->src, offset, lastn, 0);
 205        /* 3. Exclusive-or Dn with C to create Xn */
 206        /* 4. Select the first Ln bytes of Xn to create Pn */
 207        crypto_xor(d + bsize, d, lastn);
 208
 209        /* 5. Append the tail (BB - Ln) bytes of Xn to Cn to create En */
 210        memcpy(d + lastn, d + bsize + lastn, bsize - lastn);
 211        /* 6. Decrypt En to create Pn-1 */
 212
 213        scatterwalk_map_and_copy(d, sg, 0, bsize + lastn, 1);
 214        memzero_explicit(d, sizeof(d));
 215
 216        skcipher_request_set_callback(subreq, req->base.flags &
 217                                              CRYPTO_TFM_REQ_MAY_BACKLOG,
 218                                      cts_cbc_crypt_done, req);
 219
 220        skcipher_request_set_crypt(subreq, sg, sg, bsize, space);
 221        return crypto_skcipher_decrypt(subreq);
 222}
 223
 224static void crypto_cts_decrypt_done(struct crypto_async_request *areq, int err)
 225{
 226        struct skcipher_request *req = areq->data;
 227
 228        if (err)
 229                goto out;
 230
 231        err = cts_cbc_decrypt(req);
 232        if (err == -EINPROGRESS ||
 233            (err == -EBUSY && req->base.flags & CRYPTO_TFM_REQ_MAY_BACKLOG))
 234                return;
 235
 236out:
 237        skcipher_request_complete(req, err);
 238}
 239
 240static int crypto_cts_decrypt(struct skcipher_request *req)
 241{
 242        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 243        struct crypto_cts_reqctx *rctx = skcipher_request_ctx(req);
 244        struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
 245        struct skcipher_request *subreq = &rctx->subreq;
 246        int bsize = crypto_skcipher_blocksize(tfm);
 247        unsigned int nbytes = req->cryptlen;
 248        int cbc_blocks = (nbytes + bsize - 1) / bsize - 1;
 249        unsigned int offset;
 250        u8 *space;
 251
 252        skcipher_request_set_tfm(subreq, ctx->child);
 253
 254        if (cbc_blocks <= 0) {
 255                skcipher_request_set_callback(subreq, req->base.flags,
 256                                              req->base.complete,
 257                                              req->base.data);
 258                skcipher_request_set_crypt(subreq, req->src, req->dst, nbytes,
 259                                           req->iv);
 260                return crypto_skcipher_decrypt(subreq);
 261        }
 262
 263        skcipher_request_set_callback(subreq, req->base.flags,
 264                                      crypto_cts_decrypt_done, req);
 265
 266        space = crypto_cts_reqctx_space(req);
 267
 268        offset = cbc_blocks * bsize;
 269        rctx->offset = offset;
 270
 271        if (cbc_blocks <= 1)
 272                memcpy(space, req->iv, bsize);
 273        else
 274                scatterwalk_map_and_copy(space, req->src, offset - 2 * bsize,
 275                                         bsize, 0);
 276
 277        skcipher_request_set_crypt(subreq, req->src, req->dst,
 278                                   offset, req->iv);
 279
 280        return crypto_skcipher_decrypt(subreq) ?:
 281               cts_cbc_decrypt(req);
 282}
 283
 284static int crypto_cts_init_tfm(struct crypto_skcipher *tfm)
 285{
 286        struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 287        struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 288        struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
 289        struct crypto_skcipher *cipher;
 290        unsigned reqsize;
 291        unsigned bsize;
 292        unsigned align;
 293
 294        cipher = crypto_spawn_skcipher(spawn);
 295        if (IS_ERR(cipher))
 296                return PTR_ERR(cipher);
 297
 298        ctx->child = cipher;
 299
 300        align = crypto_skcipher_alignmask(tfm);
 301        bsize = crypto_skcipher_blocksize(cipher);
 302        reqsize = ALIGN(sizeof(struct crypto_cts_reqctx) +
 303                        crypto_skcipher_reqsize(cipher),
 304                        crypto_tfm_ctx_alignment()) +
 305                  (align & ~(crypto_tfm_ctx_alignment() - 1)) + bsize;
 306
 307        crypto_skcipher_set_reqsize(tfm, reqsize);
 308
 309        return 0;
 310}
 311
 312static void crypto_cts_exit_tfm(struct crypto_skcipher *tfm)
 313{
 314        struct crypto_cts_ctx *ctx = crypto_skcipher_ctx(tfm);
 315
 316        crypto_free_skcipher(ctx->child);
 317}
 318
 319static void crypto_cts_free(struct skcipher_instance *inst)
 320{
 321        crypto_drop_skcipher(skcipher_instance_ctx(inst));
 322        kfree(inst);
 323}
 324
 325static int crypto_cts_create(struct crypto_template *tmpl, struct rtattr **tb)
 326{
 327        struct crypto_skcipher_spawn *spawn;
 328        struct skcipher_instance *inst;
 329        struct crypto_attr_type *algt;
 330        struct skcipher_alg *alg;
 331        const char *cipher_name;
 332        int err;
 333
 334        algt = crypto_get_attr_type(tb);
 335        if (IS_ERR(algt))
 336                return PTR_ERR(algt);
 337
 338        if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
 339                return -EINVAL;
 340
 341        cipher_name = crypto_attr_alg_name(tb[1]);
 342        if (IS_ERR(cipher_name))
 343                return PTR_ERR(cipher_name);
 344
 345        inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 346        if (!inst)
 347                return -ENOMEM;
 348
 349        spawn = skcipher_instance_ctx(inst);
 350
 351        crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
 352        err = crypto_grab_skcipher(spawn, cipher_name, 0,
 353                                   crypto_requires_sync(algt->type,
 354                                                        algt->mask));
 355        if (err)
 356                goto err_free_inst;
 357
 358        alg = crypto_spawn_skcipher_alg(spawn);
 359
 360        err = -EINVAL;
 361        if (crypto_skcipher_alg_ivsize(alg) != alg->base.cra_blocksize)
 362                goto err_drop_spawn;
 363
 364        if (strncmp(alg->base.cra_name, "cbc(", 4))
 365                goto err_drop_spawn;
 366
 367        err = crypto_inst_setname(skcipher_crypto_instance(inst), "cts",
 368                                  &alg->base);
 369        if (err)
 370                goto err_drop_spawn;
 371
 372        inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
 373        inst->alg.base.cra_priority = alg->base.cra_priority;
 374        inst->alg.base.cra_blocksize = alg->base.cra_blocksize;
 375        inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
 376
 377        inst->alg.ivsize = alg->base.cra_blocksize;
 378        inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
 379        inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg);
 380        inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg);
 381
 382        inst->alg.base.cra_ctxsize = sizeof(struct crypto_cts_ctx);
 383
 384        inst->alg.init = crypto_cts_init_tfm;
 385        inst->alg.exit = crypto_cts_exit_tfm;
 386
 387        inst->alg.setkey = crypto_cts_setkey;
 388        inst->alg.encrypt = crypto_cts_encrypt;
 389        inst->alg.decrypt = crypto_cts_decrypt;
 390
 391        inst->free = crypto_cts_free;
 392
 393        err = skcipher_register_instance(tmpl, inst);
 394        if (err)
 395                goto err_drop_spawn;
 396
 397out:
 398        return err;
 399
 400err_drop_spawn:
 401        crypto_drop_skcipher(spawn);
 402err_free_inst:
 403        kfree(inst);
 404        goto out;
 405}
 406
 407static struct crypto_template crypto_cts_tmpl = {
 408        .name = "cts",
 409        .create = crypto_cts_create,
 410        .module = THIS_MODULE,
 411};
 412
 413static int __init crypto_cts_module_init(void)
 414{
 415        return crypto_register_template(&crypto_cts_tmpl);
 416}
 417
 418static void __exit crypto_cts_module_exit(void)
 419{
 420        crypto_unregister_template(&crypto_cts_tmpl);
 421}
 422
 423module_init(crypto_cts_module_init);
 424module_exit(crypto_cts_module_exit);
 425
 426MODULE_LICENSE("Dual BSD/GPL");
 427MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
 428MODULE_ALIAS_CRYPTO("cts");
 429