1 /* LRW: as defined by Cyril Guyot in
2 * http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
4 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
7 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
9 * This program is free software; you can redistribute it and/or modify it
10 * under the terms of the GNU General Public License as published by the Free
11 * Software Foundation; either version 2 of the License, or (at your option)
14 /* This implementation is checked against the test vectors in the above
15 * document and by a test vector provided by Ken Buchanan at
16 * http://www.mail-archive.com/stds-p1619@listserv.ieee.org/msg00173.html
18 * The test vectors are included in the testing module tcrypt.[ch] */
20 #include <crypto/internal/skcipher.h>
21 #include <crypto/scatterwalk.h>
22 #include <linux/err.h>
23 #include <linux/init.h>
24 #include <linux/kernel.h>
25 #include <linux/module.h>
26 #include <linux/scatterlist.h>
27 #include <linux/slab.h>
29 #include <crypto/b128ops.h>
30 #include <crypto/gf128mul.h>
32 #define LRW_BLOCK_SIZE 16
35 struct crypto_skcipher *child;
38 * optimizes multiplying a random (non incrementing, as at the
39 * start of a new sector) value with key2, we could also have
40 * used 4k optimization tables or no optimization at all. In the
41 * latter case we would have to store key2 here
43 struct gf128mul_64k *table;
47 * key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
48 * key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
49 * key2*{ 0,0,...1,1,1,1,1 }, etc
50 * needed for optimized multiplication of incrementing values
58 struct skcipher_request subreq;
61 static inline void setbit128_bbe(void *b, int bit)
63 __set_bit(bit ^ (0x80 -
72 static int setkey(struct crypto_skcipher *parent, const u8 *key,
75 struct priv *ctx = crypto_skcipher_ctx(parent);
76 struct crypto_skcipher *child = ctx->child;
77 int err, bsize = LRW_BLOCK_SIZE;
78 const u8 *tweak = key + keylen - bsize;
82 crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
83 crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
85 err = crypto_skcipher_setkey(child, key, keylen - bsize);
86 crypto_skcipher_set_flags(parent, crypto_skcipher_get_flags(child) &
92 gf128mul_free_64k(ctx->table);
94 /* initialize multiplication table for Key2 */
95 ctx->table = gf128mul_init_64k_bbe((be128 *)tweak);
99 /* initialize optimization table */
100 for (i = 0; i < 128; i++) {
101 setbit128_bbe(&tmp, i);
102 ctx->mulinc[i] = tmp;
103 gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
110 * Returns the number of trailing '1' bits in the words of the counter, which is
111 * represented by 4 32-bit words, arranged from least to most significant.
112 * At the same time, increments the counter by one.
116 * u32 counter[4] = { 0xFFFFFFFF, 0x1, 0x0, 0x0 };
117 * int i = next_index(&counter);
118 * // i == 33, counter == { 0x0, 0x2, 0x0, 0x0 }
120 static int next_index(u32 *counter)
124 for (i = 0; i < 4; i++) {
125 if (counter[i] + 1 != 0) {
126 res += ffz(counter[i]++);
134 * If we get here, then x == 128 and we are incrementing the counter
135 * from all ones to all zeros. This means we must return index 127, i.e.
136 * the one corresponding to key2*{ 1,...,1 }.
142 * We compute the tweak masks twice (both before and after the ECB encryption or
143 * decryption) to avoid having to allocate a temporary buffer and/or make
144 * mutliple calls to the 'ecb(..)' instance, which usually would be slower than
145 * just doing the next_index() calls again.
147 static int xor_tweak(struct skcipher_request *req, bool second_pass)
149 const int bs = LRW_BLOCK_SIZE;
150 struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
151 struct priv *ctx = crypto_skcipher_ctx(tfm);
152 struct rctx *rctx = skcipher_request_ctx(req);
154 struct skcipher_walk w;
161 /* set to our TFM to enforce correct alignment: */
162 skcipher_request_set_tfm(req, tfm);
165 err = skcipher_walk_virt(&w, req, false);
168 counter[0] = be32_to_cpu(iv[3]);
169 counter[1] = be32_to_cpu(iv[2]);
170 counter[2] = be32_to_cpu(iv[1]);
171 counter[3] = be32_to_cpu(iv[0]);
174 unsigned int avail = w.nbytes;
178 wsrc = w.src.virt.addr;
179 wdst = w.dst.virt.addr;
182 be128_xor(wdst++, &t, wsrc++);
184 /* T <- I*Key2, using the optimization
185 * discussed in the specification */
186 be128_xor(&t, &t, &ctx->mulinc[next_index(counter)]);
187 } while ((avail -= bs) >= bs);
189 if (second_pass && w.nbytes == w.total) {
190 iv[0] = cpu_to_be32(counter[3]);
191 iv[1] = cpu_to_be32(counter[2]);
192 iv[2] = cpu_to_be32(counter[1]);
193 iv[3] = cpu_to_be32(counter[0]);
196 err = skcipher_walk_done(&w, avail);
202 static int xor_tweak_pre(struct skcipher_request *req)
204 return xor_tweak(req, false);
207 static int xor_tweak_post(struct skcipher_request *req)
209 return xor_tweak(req, true);
212 static void crypt_done(struct crypto_async_request *areq, int err)
214 struct skcipher_request *req = areq->data;
217 err = xor_tweak_post(req);
219 skcipher_request_complete(req, err);
222 static void init_crypt(struct skcipher_request *req)
224 struct priv *ctx = crypto_skcipher_ctx(crypto_skcipher_reqtfm(req));
225 struct rctx *rctx = skcipher_request_ctx(req);
226 struct skcipher_request *subreq = &rctx->subreq;
228 skcipher_request_set_tfm(subreq, ctx->child);
229 skcipher_request_set_callback(subreq, req->base.flags, crypt_done, req);
230 /* pass req->iv as IV (will be used by xor_tweak, ECB will ignore it) */
231 skcipher_request_set_crypt(subreq, req->dst, req->dst,
232 req->cryptlen, req->iv);
234 /* calculate first value of T */
235 memcpy(&rctx->t, req->iv, sizeof(rctx->t));
238 gf128mul_64k_bbe(&rctx->t, ctx->table);
241 static int encrypt(struct skcipher_request *req)
243 struct rctx *rctx = skcipher_request_ctx(req);
244 struct skcipher_request *subreq = &rctx->subreq;
247 return xor_tweak_pre(req) ?:
248 crypto_skcipher_encrypt(subreq) ?:
252 static int decrypt(struct skcipher_request *req)
254 struct rctx *rctx = skcipher_request_ctx(req);
255 struct skcipher_request *subreq = &rctx->subreq;
258 return xor_tweak_pre(req) ?:
259 crypto_skcipher_decrypt(subreq) ?:
263 static int init_tfm(struct crypto_skcipher *tfm)
265 struct skcipher_instance *inst = skcipher_alg_instance(tfm);
266 struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
267 struct priv *ctx = crypto_skcipher_ctx(tfm);
268 struct crypto_skcipher *cipher;
270 cipher = crypto_spawn_skcipher(spawn);
272 return PTR_ERR(cipher);
276 crypto_skcipher_set_reqsize(tfm, crypto_skcipher_reqsize(cipher) +
277 sizeof(struct rctx));
282 static void exit_tfm(struct crypto_skcipher *tfm)
284 struct priv *ctx = crypto_skcipher_ctx(tfm);
287 gf128mul_free_64k(ctx->table);
288 crypto_free_skcipher(ctx->child);
291 static void free(struct skcipher_instance *inst)
293 crypto_drop_skcipher(skcipher_instance_ctx(inst));
297 static int create(struct crypto_template *tmpl, struct rtattr **tb)
299 struct crypto_skcipher_spawn *spawn;
300 struct skcipher_instance *inst;
301 struct crypto_attr_type *algt;
302 struct skcipher_alg *alg;
303 const char *cipher_name;
304 char ecb_name[CRYPTO_MAX_ALG_NAME];
307 algt = crypto_get_attr_type(tb);
309 return PTR_ERR(algt);
311 if ((algt->type ^ CRYPTO_ALG_TYPE_SKCIPHER) & algt->mask)
314 cipher_name = crypto_attr_alg_name(tb[1]);
315 if (IS_ERR(cipher_name))
316 return PTR_ERR(cipher_name);
318 inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
322 spawn = skcipher_instance_ctx(inst);
324 crypto_set_skcipher_spawn(spawn, skcipher_crypto_instance(inst));
325 err = crypto_grab_skcipher(spawn, cipher_name, 0,
326 crypto_requires_sync(algt->type,
328 if (err == -ENOENT) {
330 if (snprintf(ecb_name, CRYPTO_MAX_ALG_NAME, "ecb(%s)",
331 cipher_name) >= CRYPTO_MAX_ALG_NAME)
334 err = crypto_grab_skcipher(spawn, ecb_name, 0,
335 crypto_requires_sync(algt->type,
342 alg = crypto_skcipher_spawn_alg(spawn);
345 if (alg->base.cra_blocksize != LRW_BLOCK_SIZE)
348 if (crypto_skcipher_alg_ivsize(alg))
351 err = crypto_inst_setname(skcipher_crypto_instance(inst), "lrw",
357 cipher_name = alg->base.cra_name;
359 /* Alas we screwed up the naming so we have to mangle the
362 if (!strncmp(cipher_name, "ecb(", 4)) {
365 len = strlcpy(ecb_name, cipher_name + 4, sizeof(ecb_name));
366 if (len < 2 || len >= sizeof(ecb_name))
369 if (ecb_name[len - 1] != ')')
372 ecb_name[len - 1] = 0;
374 if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
375 "lrw(%s)", ecb_name) >= CRYPTO_MAX_ALG_NAME) {
382 inst->alg.base.cra_flags = alg->base.cra_flags & CRYPTO_ALG_ASYNC;
383 inst->alg.base.cra_priority = alg->base.cra_priority;
384 inst->alg.base.cra_blocksize = LRW_BLOCK_SIZE;
385 inst->alg.base.cra_alignmask = alg->base.cra_alignmask |
386 (__alignof__(__be32) - 1);
388 inst->alg.ivsize = LRW_BLOCK_SIZE;
389 inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
391 inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
394 inst->alg.base.cra_ctxsize = sizeof(struct priv);
396 inst->alg.init = init_tfm;
397 inst->alg.exit = exit_tfm;
399 inst->alg.setkey = setkey;
400 inst->alg.encrypt = encrypt;
401 inst->alg.decrypt = decrypt;
405 err = skcipher_register_instance(tmpl, inst);
413 crypto_drop_skcipher(spawn);
419 static struct crypto_template crypto_tmpl = {
422 .module = THIS_MODULE,
425 static int __init crypto_module_init(void)
427 return crypto_register_template(&crypto_tmpl);
430 static void __exit crypto_module_exit(void)
432 crypto_unregister_template(&crypto_tmpl);
435 module_init(crypto_module_init);
436 module_exit(crypto_module_exit);
438 MODULE_LICENSE("GPL");
439 MODULE_DESCRIPTION("LRW block cipher mode");
440 MODULE_ALIAS_CRYPTO("lrw");