the-tree/crypto/lrw.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /* LRW: as defined by Cyril Guyot in
0003  *  http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
0004  *
0005  * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
0006  *
0007  * Based on ecb.c
0008  * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
0009  */
0010 /* This implementation is checked against the test vectors in the above
0011  * document and by a test vector provided by Ken Buchanan at
0012  * https://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
0013  *
0014  * The test vectors are included in the testing module tcrypt.[ch] */
0015
0016 #include <crypto/internal/skcipher.h>
0017 #include <crypto/scatterwalk.h>
0018 #include <linux/err.h>
0019 #include <linux/init.h>
0020 #include <linux/kernel.h>
0021 #include <linux/module.h>
0022 #include <linux/scatterlist.h>
0023 #include <linux/slab.h>
0024
0025 #include <crypto/b128ops.h>
0026 #include <crypto/gf128mul.h>
0027
0028 #define LRW_BLOCK_SIZE 16
0029
0030 struct lrw_tfm_ctx {
0031     struct crypto_skcipher *child;
0032
0033     /*
0034      * optimizes multiplying a random (non incrementing, as at the
0035      * start of a new sector) value with key2, we could also have
0036      * used 4k optimization tables or no optimization at all. In the
0037      * latter case we would have to store key2 here
0038      */
0039     struct gf128mul_64k *table;
0040
0041     /*
0042      * stores:
0043      *  key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
0044      *  key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
0045      *  key2*{ 0,0,...1,1,1,1,1 }, etc
0046      * needed for optimized multiplication of incrementing values
0047      * with key2
0048      */
0049     be128 mulinc[128];
0050 };
0051
0052 struct lrw_request_ctx {
0053     be128 t;
0054     struct skcipher_request subreq;
0055 };
0056
0057 static inline void lrw_setbit128_bbe(void *b, int bit)
0058 {
0059     __set_bit(bit ^ (0x80 -
0060 #ifdef __BIG_ENDIAN
0061              BITS_PER_LONG
0062 #else
0063              BITS_PER_BYTE
0064 #endif
0065             ), b);
0066 }
0067
0068 static int lrw_setkey(struct crypto_skcipher *parent, const u8 *key,
0069               unsigned int keylen)
0070 {
0071     struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(parent);
0072     struct crypto_skcipher *child = ctx->child;
0073     int err, bsize = LRW_BLOCK_SIZE;
0074     const u8 *tweak = key + keylen - bsize;
0075     be128 tmp = { 0 };
0076     int i;
0077
0078     crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
0079     crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
0080                      CRYPTO_TFM_REQ_MASK);
0081     err = crypto_skcipher_setkey(child, key, keylen - bsize);
0082     if (err)
0083         return err;
0084
0085     if (ctx->table)
0086         gf128mul_free_64k(ctx->table);
0087
0088     /* initialize multiplication table for Key2 */
0089     ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
0090     if (!ctx->table)
0091         return -ENOMEM;
0092
0093     /* initialize optimization table */
0094     for (i = 0; i < 128; i++) {
0095         lrw_setbit128_bbe(&tmp, i);
0096         ctx->mulinc[i] = tmp;
0097         gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
0098     }
0099
0100     return 0;
0101 }
0102
0103 /*
0104  * Returns the number of trailing '1' bits in the words of the counter, which is
0105  * represented by 4 32-bit words, arranged from least to most significant.
0106  * At the same time, increments the counter by one.
0107  *
0108  * For example:
0109  *
0110  * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
0111  * int i = lrw_next_index(&counter);
0112  * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
0113  */
0114 static int lrw_next_index(u32 *counter)
0115 {
0116     int i, res = 0;
0117
0118     for (i = 0; i < 4; i++) {
0119         if (counter[i] + 1 != 0)
0120             return res + ffz(counter[i]++);
0121
0122         counter[i] = 0;
0123         res += 32;
0124     }
0125
0126     /*
0127      * If we get here, then x == 128 and we are incrementing the counter
0128      * from all ones to all zeros. This means we must return index 127, i.e.
0129      * the one corresponding to key2*{ 1,...,1 }.
0130      */
0131     return 127;
0132 }
0133
0134 /*
0135  * We compute the tweak masks twice (both before and after the ECB encryption or
0136  * decryption) to avoid having to allocate a temporary buffer and/or make
0137  * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
0138  * just doing the lrw_next_index() calls again.
0139  */
0140 static int lrw_xor_tweak(struct skcipher_request *req, bool second_pass)
0141 {
0142     const int bs = LRW_BLOCK_SIZE;
0143     struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
0144     const struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
0145     struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
0146     be128 t = rctx->t;
0147     struct skcipher_walk w;
0148     __be32 *iv;
0149     u32 counter[4];
0150     int err;
0151
0152     if (second_pass) {
0153         req = &rctx->subreq;
0154         /* set to our TFM to enforce correct alignment: */
0155         skcipher_request_set_tfm(req, tfm);
0156     }
0157
0158     err = skcipher_walk_virt(&w, req, false);
0159     if (err)
0160         return err;
0161
0162     iv = (__be32 *)w.iv;
0163     counter[0] = be32_to_cpu(iv[3]);
0164     counter[1] = be32_to_cpu(iv[2]);
0165     counter[2] = be32_to_cpu(iv[1]);
0166     counter[3] = be32_to_cpu(iv[0]);
0167
0168     while (w.nbytes) {
0169         unsigned int avail = w.nbytes;
0170         be128 *wsrc;
0171         be128 *wdst;
0172
0173         wsrc = w.src.virt.addr;
0174         wdst = w.dst.virt.addr;
0175
0176         do {
0177             be128_xor(wdst++, &t, wsrc++);
0178
0179             /* T <- I*Key2, using the optimization
0180              * discussed in the specification */
0181             be128_xor(&t, &t,
0182                   &ctx->mulinc[lrw_next_index(counter)]);
0183         } while ((avail -= bs) >= bs);
0184
0185         if (second_pass && w.nbytes == w.total) {
0186             iv[0] = cpu_to_be32(counter[3]);
0187             iv[1] = cpu_to_be32(counter[2]);
0188             iv[2] = cpu_to_be32(counter[1]);
0189             iv[3] = cpu_to_be32(counter[0]);
0190         }
0191
0192         err = skcipher_walk_done(&w, avail);
0193     }
0194
0195     return err;
0196 }
0197
0198 static int lrw_xor_tweak_pre(struct skcipher_request *req)
0199 {
0200     return lrw_xor_tweak(req, false);
0201 }
0202
0203 static int lrw_xor_tweak_post(struct skcipher_request *req)
0204 {
0205     return lrw_xor_tweak(req, true);
0206 }
0207
0208 static void lrw_crypt_done(struct crypto_async_request *areq, int err)
0209 {
0210     struct skcipher_request *req = areq->data;
0211
0212     if (!err) {
0213         struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
0214
0215         rctx->subreq.base.flags &= ~CRYPTO_TFM_REQ_MAY_SLEEP;
0216         err = lrw_xor_tweak_post(req);
0217     }
0218
0219     skcipher_request_complete(req, err);
0220 }
0221
0222 static void lrw_init_crypt(struct skcipher_request *req)
0223 {
0224     const struct lrw_tfm_ctx *ctx =
0225         crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
0226     struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
0227     struct skcipher_request *subreq = &rctx->subreq;
0228
0229     skcipher_request_set_tfm(subreq, ctx->child);
0230     skcipher_request_set_callback(subreq, req->base.flags, lrw_crypt_done,
0231                       req);
0232     /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
0233     skcipher_request_set_crypt(subreq, req->dst, req->dst,
0234                    req->cryptlen, req->iv);
0235
0236     /* calculate first value of T */
0237     memcpy(&rctx->t, req->iv, sizeof(rctx->t));
0238
0239     /* T <- I*Key2 */
0240     gf128mul_64k_bbe(&rctx->t, ctx->table);
0241 }
0242
0243 static int lrw_encrypt(struct skcipher_request *req)
0244 {
0245     struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
0246     struct skcipher_request *subreq = &rctx->subreq;
0247
0248     lrw_init_crypt(req);
0249     return lrw_xor_tweak_pre(req) ?:
0250         crypto_skcipher_encrypt(subreq) ?:
0251         lrw_xor_tweak_post(req);
0252 }
0253
0254 static int lrw_decrypt(struct skcipher_request *req)
0255 {
0256     struct lrw_request_ctx *rctx = skcipher_request_ctx(req);
0257     struct skcipher_request *subreq = &rctx->subreq;
0258
0259     lrw_init_crypt(req);
0260     return lrw_xor_tweak_pre(req) ?:
0261         crypto_skcipher_decrypt(subreq) ?:
0262         lrw_xor_tweak_post(req);
0263 }
0264
0265 static int lrw_init_tfm(struct crypto_skcipher *tfm)
0266 {
0267     struct skcipher_instance *inst = skcipher_alg_instance(tfm);
0268     struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
0269     struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
0270     struct crypto_skcipher *cipher;
0271
0272     cipher = crypto_spawn_skcipher(spawn);
0273     if (IS_ERR(cipher))
0274         return PTR_ERR(cipher);
0275
0276     ctx->child = cipher;
0277
0278     crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
0279                      sizeof(struct lrw_request_ctx));
0280
0281     return 0;
0282 }
0283
0284 static void lrw_exit_tfm(struct crypto_skcipher *tfm)
0285 {
0286     struct lrw_tfm_ctx *ctx = crypto_skcipher_ctx(tfm);
0287
0288     if (ctx->table)
0289         gf128mul_free_64k(ctx->table);
0290     crypto_free_skcipher(ctx->child);
0291 }
0292
0293 static void lrw_free_instance(struct skcipher_instance *inst)
0294 {
0295     crypto_drop_skcipher(skcipher_instance_ctx(inst));
0296     kfree(inst);
0297 }
0298
0299 static int lrw_create(struct crypto_template *tmpl, struct rtattr **tb)
0300 {
0301     struct crypto_skcipher_spawn *spawn;
0302     struct skcipher_instance *inst;
0303     struct skcipher_alg *alg;
0304     const char *cipher_name;
0305     char ecb_name[CRYPTO_MAX_ALG_NAME];
0306     u32 mask;
0307     int err;
0308
0309     err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
0310     if (err)
0311         return err;
0312
0313     cipher_name = crypto_attr_alg_name(tb[1]);
0314     if (IS_ERR(cipher_name))
0315         return PTR_ERR(cipher_name);
0316
0317     inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
0318     if (!inst)
0319         return -ENOMEM;
0320
0321     spawn = skcipher_instance_ctx(inst);
0322
0323     err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
0324                    cipher_name, 0, mask);
0325     if (err == -ENOENT) {
0326         err = -ENAMETOOLONG;
0327         if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
0328                  cipher_name) >= CRYPTO_MAX_ALG_NAME)
0329             goto err_free_inst;
0330
0331         err = crypto_grab_skcipher(spawn,
0332                        skcipher_crypto_instance(inst),
0333                        ecb_name, 0, mask);
0334     }
0335
0336     if (err)
0337         goto err_free_inst;
0338
0339     alg = crypto_skcipher_spawn_alg(spawn);
0340
0341     err = -EINVAL;
0342     if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
0343         goto err_free_inst;
0344
0345     if (crypto_skcipher_alg_ivsize(alg))
0346         goto err_free_inst;
0347
0348     err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
0349                   &alg->base);
0350     if (err)
0351         goto err_free_inst;
0352
0353     err = -EINVAL;
0354     cipher_name = alg->base.cra_name;
0355
0356     /* Alas we screwed up the naming so we have to mangle the
0357      * cipher name.
0358      */
0359     if (!strncmp(cipher_name, "ecb(", 4)) {
0360         unsigned len;
0361
0362         len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
0363         if (len < 2 || len >= sizeof(ecb_name))
0364             goto err_free_inst;
0365
0366         if (ecb_name[len - 1] != ')')
0367             goto err_free_inst;
0368
0369         ecb_name[len - 1] = 0;
0370
0371         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
0372                  "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
0373             err = -ENAMETOOLONG;
0374             goto err_free_inst;
0375         }
0376     } else
0377         goto err_free_inst;
0378
0379     inst->alg.base.cra_priority = alg->base.cra_priority;
0380     inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
0381     inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
0382                        (__alignof__(be128) - 1);
0383
0384     inst->alg.ivsize = LRW_BLOCK_SIZE;
0385     inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
0386                 LRW_BLOCK_SIZE;
0387     inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
0388                 LRW_BLOCK_SIZE;
0389
0390     inst->alg.base.cra_ctxsize = sizeof(struct lrw_tfm_ctx);
0391
0392     inst->alg.init = lrw_init_tfm;
0393     inst->alg.exit = lrw_exit_tfm;
0394
0395     inst->alg.setkey = lrw_setkey;
0396     inst->alg.encrypt = lrw_encrypt;
0397     inst->alg.decrypt = lrw_decrypt;
0398
0399     inst->free = lrw_free_instance;
0400
0401     err = skcipher_register_instance(tmpl, inst);
0402     if (err) {
0403 err_free_inst:
0404         lrw_free_instance(inst);
0405     }
0406     return err;
0407 }
0408
0409 static struct crypto_template lrw_tmpl = {
0410     .name = "lrw",
0411     .create = lrw_create,
0412     .module = THIS_MODULE,
0413 };
0414
0415 static int __init lrw_module_init(void)
0416 {
0417     return crypto_register_template(&lrw_tmpl);
0418 }
0419
0420 static void __exit lrw_module_exit(void)
0421 {
0422     crypto_unregister_template(&lrw_tmpl);
0423 }
0424
0425 subsys_initcall(lrw_module_init);
0426 module_exit(lrw_module_exit);
0427
0428 MODULE_LICENSE("GPL");
0429 MODULE_DESCRIPTION("LRW block cipher mode");
0430 MODULE_ALIAS_CRYPTO("lrw");
0431 MODULE_SOFTDEP("pre: ecb");