linux/crypto/lrw.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/* LRW: as defined by Cyril Guyot in
   3 *      http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
   4 *
   5 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
   6 *
   7 * Based on ecb.c
   8 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
   9 */
  10/* This implementation is checked against the test vectors in the above
  11 * document and by a test vector provided by Ken Buchanan at
  12 * https://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
  13 *
  14 * The test vectors are included in the testing module tcrypt.[ch] */
  15
  16#include <crypto/internal/skcipher.h>
  17#include <crypto/scatterwalk.h>
  18#include <linux/err.h>
  19#include <linux/init.h>
  20#include <linux/kernel.h>
  21#include <linux/module.h>
  22#include <linux/scatterlist.h>
  23#include <linux/slab.h>
  24
  25#include <crypto/b128ops.h>
  26#include <crypto/gf128mul.h>
  27
  28#define LRW_BLOCK_SIZE 16
  29
  30struct lrw_tfm_ctx {
  31        struct crypto_skcipher *child;
  32
  33        /*
  34         * optimizes multiplying a random (non incrementing, as at the
  35         * start of a new sector) value with key2, we could also have
  36         * used 4k optimization tables or no optimization at all. In the
  37         * latter case we would have to store key2 here
  38         */
  39        struct gf128mul_64k *table;
  40
  41        /*
  42         * stores:
  43         *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
  44         *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
  45         *  key2*{ 0,0,...1,1,1,1,1 }, etc
  46         * needed for optimized multiplication of incrementing values
  47         * with key2
  48         */
  49        be128 mulinc[128];
  50};
  51
  52struct lrw_request_ctx {
  53        be128 t;
  54        struct skcipher_request subreq;
  55};
  56
  57static inline void lrw_setbit128_bbe(void *b, int bit)
  58{
  59        __set_bit(bit ^ (0x80 -
  60#ifdef __BIG_ENDIAN
  61                         BITS_PER_LONG
  62#else
  63                         BITS_PER_BYTE
  64#endif
  65                        ), b);
  66}
  67
  68static int lrw_setkey(struct crypto_skcipher *parent, const u8 *key,
  69                      unsigned int keylen)
  70{
  71        struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(parent);
  72        struct crypto_skcipher *child = ctx->child;
  73        int err, bsize = LRW_BLOCK_SIZE;
  74        const u8 *tweak = key + keylen - bsize;
  75        be128 tmp = { 0 };
  76        int i;
  77
  78        crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
  79        crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
  80                                         CRYPTO_TFM_REQ_MASK);
  81        err = crypto_skcipher_setkey(child, key, keylen - bsize);
  82        if (err)
  83                return err;
  84
  85        if (ctx->table)
  86                gf128mul_free_64k(ctx->table);
  87
  88        /* initialize multiplication table for Key2 */
  89        ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
  90        if (!ctx->table)
  91                return -ENOMEM;
  92
  93        /* initialize optimization table */
  94        for (i = 0; i < 128; i++) {
  95                lrw_setbit128_bbe(&tmp, i);
  96                ctx->mulinc[i] = tmp;
  97                gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
  98        }
  99
 100        return 0;
 101}
 102
 103/*
 104 * Returns the number of trailing '1' bits in the words of the counter, which is
 105 * represented by 4 32-bit words, arranged from least to most significant.
 106 * At the same time, increments the counter by one.
 107 *
 108 * For example:
 109 *
 110 * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
 111 * int i = lrw_next_index(&counter);
 112 * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
 113 */
 114static int lrw_next_index(u32 *counter)
 115{
 116        int i, res = 0;
 117
 118        for (i = 0; i < 4; i++) {
 119                if (counter[i] + 1 != 0)
 120                        return res + ffz(counter[i]++);
 121
 122                counter[i] = 0;
 123                res += 32;
 124        }
 125
 126        /*
 127         * If we get here, then x == 128 and we are incrementing the counter
 128         * from all ones to all zeros. This means we must return index 127, i.e.
 129         * the one corresponding to key2*{ 1,...,1 }.
 130         */
 131        return 127;
 132}
 133
 134/*
 135 * We compute the tweak masks twice (both before and after the ECB encryption or
 136 * decryption) to avoid having to allocate a temporary buffer and/or make
 137 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
 138 * just doing the lrw_next_index() calls again.
 139 */
 140static int lrw_xor_tweak(struct skcipher_request *req, bool second_pass)
 141{
 142        const int bs = LRW_BLOCK_SIZE;
 143        struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 144        const struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
 145        struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
 146        be128 t = rctx->t;
 147        struct skcipher_walk w;
 148        __be32 *iv;
 149        u32 counter[4];
 150        int err;
 151
 152        if (second_pass) {
 153                req = &rctx->subreq;
 154                /* set to our TFM to enforce correct alignment: */
 155                skcipher_request_set_tfm(req, tfm);
 156        }
 157
 158        err = skcipher_walk_virt(&w, req, false);
 159        if (err)
 160                return err;
 161
 162        iv = (__be32 *)w.iv;
 163        counter[0] = be32_to_cpu(iv[3]);
 164        counter[1] = be32_to_cpu(iv[2]);
 165        counter[2] = be32_to_cpu(iv[1]);
 166        counter[3] = be32_to_cpu(iv[0]);
 167
 168        while (w.nbytes) {
 169                unsigned int avail = w.nbytes;
 170                be128 *wsrc;
 171                be128 *wdst;
 172
 173                wsrc = w.src.virt.addr;
 174                wdst = w.dst.virt.addr;
 175
 176                do {
 177                        be128_xor(wdst++, &t, wsrc++);
 178
 179                        /* T <- I*Key2, using the optimization
 180                         * discussed in the specification */
 181                        be128_xor(&t, &t,
 182                                  &ctx->mulinc[lrw_next_index(counter)]);
 183                } while ((avail -= bs) >= bs);
 184
 185                if (second_pass && w.nbytes == w.total) {
 186                        iv[0] = cpu_to_be32(counter[3]);
 187                        iv[1] = cpu_to_be32(counter[2]);
 188                        iv[2] = cpu_to_be32(counter[1]);
 189                        iv[3] = cpu_to_be32(counter[0]);
 190                }
 191
 192                err = skcipher_walk_done(&w, avail);
 193        }
 194
 195        return err;
 196}
 197
 198static int lrw_xor_tweak_pre(struct skcipher_request *req)
 199{
 200        return lrw_xor_tweak(req, false);
 201}
 202
 203static int lrw_xor_tweak_post(struct skcipher_request *req)
 204{
 205        return lrw_xor_tweak(req, true);
 206}
 207
 208static void lrw_crypt_done(struct crypto_async_request *areq, int err)
 209{
 210        struct skcipher_request *req = areq->data;
 211
 212        if (!err) {
 213                struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
 214
 215                rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
 216                err = lrw_xor_tweak_post(req);
 217        }
 218
 219        skcipher_request_complete(req, err);
 220}
 221
 222static void lrw_init_crypt(struct skcipher_request *req)
 223{
 224        const struct lrw_tfm_ctx *ctx =
 225                crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
 226        struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
 227        struct skcipher_request *subreq = &rctx->subreq;
 228
 229        skcipher_request_set_tfm(subreq, ctx->child);
 230        skcipher_request_set_callback(subreq, req->base.flags, lrw_crypt_done,
 231                                      req);
 232        /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
 233        skcipher_request_set_crypt(subreq, req->dst, req->dst,
 234                                   req->cryptlen, req->iv);
 235
 236        /* calculate first value of T */
 237        memcpy(&rctx->t, req->iv, sizeof(rctx->t));
 238
 239        /* T <- I*Key2 */
 240        gf128mul_64k_bbe(&rctx->t, ctx->table);
 241}
 242
 243static int lrw_encrypt(struct skcipher_request *req)
 244{
 245        struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
 246        struct skcipher_request *subreq = &rctx->subreq;
 247
 248        lrw_init_crypt(req);
 249        return lrw_xor_tweak_pre(req) ?:
 250                crypto_skcipher_encrypt(subreq) ?:
 251                lrw_xor_tweak_post(req);
 252}
 253
 254static int lrw_decrypt(struct skcipher_request *req)
 255{
 256        struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
 257        struct skcipher_request *subreq = &rctx->subreq;
 258
 259        lrw_init_crypt(req);
 260        return lrw_xor_tweak_pre(req) ?:
 261                crypto_skcipher_decrypt(subreq) ?:
 262                lrw_xor_tweak_post(req);
 263}
 264
 265static int lrw_init_tfm(struct crypto_skcipher *tfm)
 266{
 267        struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 268        struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 269        struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
 270        struct crypto_skcipher *cipher;
 271
 272        cipher = crypto_spawn_skcipher(spawn);
 273        if (IS_ERR(cipher))
 274                return PTR_ERR(cipher);
 275
 276        ctx->child = cipher;
 277
 278        crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
 279                                         sizeof(struct lrw_request_ctx));
 280
 281        return 0;
 282}
 283
 284static void lrw_exit_tfm(struct crypto_skcipher *tfm)
 285{
 286        struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
 287
 288        if (ctx->table)
 289                gf128mul_free_64k(ctx->table);
 290        crypto_free_skcipher(ctx->child);
 291}
 292
 293static void lrw_free_instance(struct skcipher_instance *inst)
 294{
 295        crypto_drop_skcipher(skcipher_instance_ctx(inst));
 296        kfree(inst);
 297}
 298
 299static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)
 300{
 301        struct crypto_skcipher_spawn *spawn;
 302        struct skcipher_instance *inst;
 303        struct skcipher_alg *alg;
 304        const char *cipher_name;
 305        char ecb_name[CRYPTO_MAX_ALG_NAME];
 306        u32 mask;
 307        int err;
 308
 309        err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
 310        if (err)
 311                return err;
 312
 313        cipher_name = crypto_attr_alg_name(tb[1]);
 314        if (IS_ERR(cipher_name))
 315                return PTR_ERR(cipher_name);
 316
 317        inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 318        if (!inst)
 319                return -ENOMEM;
 320
 321        spawn = skcipher_instance_ctx(inst);
 322
 323        err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
 324                                   cipher_name, 0, mask);
 325        if (err == -ENOENT) {
 326                err = -ENAMETOOLONG;
 327                if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
 328                             cipher_name) >= CRYPTO_MAX_ALG_NAME)
 329                        goto err_free_inst;
 330
 331                err = crypto_grab_skcipher(spawn,
 332                                           skcipher_crypto_instance(inst),
 333                                           ecb_name, 0, mask);
 334        }
 335
 336        if (err)
 337                goto err_free_inst;
 338
 339        alg = crypto_skcipher_spawn_alg(spawn);
 340
 341        err = -EINVAL;
 342        if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
 343                goto err_free_inst;
 344
 345        if (crypto_skcipher_alg_ivsize(alg))
 346                goto err_free_inst;
 347
 348        err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
 349                                  &alg->base);
 350        if (err)
 351                goto err_free_inst;
 352
 353        err = -EINVAL;
 354        cipher_name = alg->base.cra_name;
 355
 356        /* Alas we screwed up the naming so we have to mangle the
 357         * cipher name.
 358         */
 359        if (!strncmp(cipher_name, "ecb(", 4)) {
 360                unsigned len;
 361
 362                len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
 363                if (len < 2 || len >= sizeof(ecb_name))
 364                        goto err_free_inst;
 365
 366                if (ecb_name[len - 1] != ')')
 367                        goto err_free_inst;
 368
 369                ecb_name[len - 1] = 0;
 370
 371                if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 372                             "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
 373                        err = -ENAMETOOLONG;
 374                        goto err_free_inst;
 375                }
 376        } else
 377                goto err_free_inst;
 378
 379        inst->alg.base.cra_priority = alg->base.cra_priority;
 380        inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
 381        inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
 382                                       (__alignof__(be128) - 1);
 383
 384        inst->alg.ivsize = LRW_BLOCK_SIZE;
 385        inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 386                                LRW_BLOCK_SIZE;
 387        inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 388                                LRW_BLOCK_SIZE;
 389
 390        inst->alg.base.cra_ctxsize = sizeof(struct lrw_tfm_ctx);
 391
 392        inst->alg.init = lrw_init_tfm;
 393        inst->alg.exit = lrw_exit_tfm;
 394
 395        inst->alg.setkey = lrw_setkey;
 396        inst->alg.encrypt = lrw_encrypt;
 397        inst->alg.decrypt = lrw_decrypt;
 398
 399        inst->free = lrw_free_instance;
 400
 401        err = skcipher_register_instance(tmpl, inst);
 402        if (err) {
 403err_free_inst:
 404                lrw_free_instance(inst);
 405        }
 406        return err;
 407}
 408
 409static struct crypto_template lrw_tmpl = {
 410        .name = "lrw",
 411        .create = lrw_create,
 412        .module = THIS_MODULE,
 413};
 414
 415static int __init lrw_module_init(void)
 416{
 417        return crypto_register_template(&lrw_tmpl);
 418}
 419
 420static void __exit lrw_module_exit(void)
 421{
 422        crypto_unregister_template(&lrw_tmpl);
 423}
 424
 425subsys_initcall(lrw_module_init);
 426module_exit(lrw_module_exit);
 427
 428MODULE_LICENSE("GPL");
 429MODULE_DESCRIPTION("LRW block cipher mode");
 430MODULE_ALIAS_CRYPTO("lrw");
 431
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