Root/crypto/lrw.c

1/* LRW: as defined by Cyril Guyot in
2 * http://grouper.ieee.org/groups/1619/email/pdf00017.pdf
3 *
4 * Copyright (c) 2006 Rik Snel <rsnel@cube.dyndns.org>
5 *
6 * Based om ecb.c
7 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
8 *
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)
12 * any later version.
13 */
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
17 *
18 * The test vectors are included in the testing module tcrypt.[ch] */
19#include <crypto/algapi.h>
20#include <linux/err.h>
21#include <linux/init.h>
22#include <linux/kernel.h>
23#include <linux/module.h>
24#include <linux/scatterlist.h>
25#include <linux/slab.h>
26
27#include <crypto/b128ops.h>
28#include <crypto/gf128mul.h>
29
30struct priv {
31    struct crypto_cipher *child;
32    /* optimizes multiplying a random (non incrementing, as at the
33     * start of a new sector) value with key2, we could also have
34     * used 4k optimization tables or no optimization at all. In the
35     * latter case we would have to store key2 here */
36    struct gf128mul_64k *table;
37    /* stores:
38     * key2*{ 0,0,...0,0,0,0,1 }, key2*{ 0,0,...0,0,0,1,1 },
39     * key2*{ 0,0,...0,0,1,1,1 }, key2*{ 0,0,...0,1,1,1,1 }
40     * key2*{ 0,0,...1,1,1,1,1 }, etc
41     * needed for optimized multiplication of incrementing values
42     * with key2 */
43    be128 mulinc[128];
44};
45
46static inline void setbit128_bbe(void *b, int bit)
47{
48    __set_bit(bit ^ (0x80 -
49#ifdef __BIG_ENDIAN
50             BITS_PER_LONG
51#else
52             BITS_PER_BYTE
53#endif
54            ), b);
55}
56
57static int setkey(struct crypto_tfm *parent, const u8 *key,
58          unsigned int keylen)
59{
60    struct priv *ctx = crypto_tfm_ctx(parent);
61    struct crypto_cipher *child = ctx->child;
62    int err, i;
63    be128 tmp = { 0 };
64    int bsize = crypto_cipher_blocksize(child);
65
66    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
67    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
68                       CRYPTO_TFM_REQ_MASK);
69    if ((err = crypto_cipher_setkey(child, key, keylen - bsize)))
70        return err;
71    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
72                     CRYPTO_TFM_RES_MASK);
73
74    if (ctx->table)
75        gf128mul_free_64k(ctx->table);
76
77    /* initialize multiplication table for Key2 */
78    ctx->table = gf128mul_init_64k_bbe((be128 *)(key + keylen - bsize));
79    if (!ctx->table)
80        return -ENOMEM;
81
82    /* initialize optimization table */
83    for (i = 0; i < 128; i++) {
84        setbit128_bbe(&tmp, i);
85        ctx->mulinc[i] = tmp;
86        gf128mul_64k_bbe(&ctx->mulinc[i], ctx->table);
87    }
88
89    return 0;
90}
91
92struct sinfo {
93    be128 t;
94    struct crypto_tfm *tfm;
95    void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
96};
97
98static inline void inc(be128 *iv)
99{
100    be64_add_cpu(&iv->b, 1);
101    if (!iv->b)
102        be64_add_cpu(&iv->a, 1);
103}
104
105static inline void lrw_round(struct sinfo *s, void *dst, const void *src)
106{
107    be128_xor(dst, &s->t, src); /* PP <- T xor P */
108    s->fn(s->tfm, dst, dst); /* CC <- E(Key2,PP) */
109    be128_xor(dst, dst, &s->t); /* C <- T xor CC */
110}
111
112/* this returns the number of consequative 1 bits starting
113 * from the right, get_index128(00 00 00 00 00 00 ... 00 00 10 FB) = 2 */
114static inline int get_index128(be128 *block)
115{
116    int x;
117    __be32 *p = (__be32 *) block;
118
119    for (p += 3, x = 0; x < 128; p--, x += 32) {
120        u32 val = be32_to_cpup(p);
121
122        if (!~val)
123            continue;
124
125        return x + ffz(val);
126    }
127
128    return x;
129}
130
131static int crypt(struct blkcipher_desc *d,
132         struct blkcipher_walk *w, struct priv *ctx,
133         void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
134{
135    int err;
136    unsigned int avail;
137    const int bs = crypto_cipher_blocksize(ctx->child);
138    struct sinfo s = {
139        .tfm = crypto_cipher_tfm(ctx->child),
140        .fn = fn
141    };
142    be128 *iv;
143    u8 *wsrc;
144    u8 *wdst;
145
146    err = blkcipher_walk_virt(d, w);
147    if (!(avail = w->nbytes))
148        return err;
149
150    wsrc = w->src.virt.addr;
151    wdst = w->dst.virt.addr;
152
153    /* calculate first value of T */
154    iv = (be128 *)w->iv;
155    s.t = *iv;
156
157    /* T <- I*Key2 */
158    gf128mul_64k_bbe(&s.t, ctx->table);
159
160    goto first;
161
162    for (;;) {
163        do {
164            /* T <- I*Key2, using the optimization
165             * discussed in the specification */
166            be128_xor(&s.t, &s.t, &ctx->mulinc[get_index128(iv)]);
167            inc(iv);
168
169first:
170            lrw_round(&s, wdst, wsrc);
171
172            wsrc += bs;
173            wdst += bs;
174        } while ((avail -= bs) >= bs);
175
176        err = blkcipher_walk_done(d, w, avail);
177        if (!(avail = w->nbytes))
178            break;
179
180        wsrc = w->src.virt.addr;
181        wdst = w->dst.virt.addr;
182    }
183
184    return err;
185}
186
187static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
188           struct scatterlist *src, unsigned int nbytes)
189{
190    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
191    struct blkcipher_walk w;
192
193    blkcipher_walk_init(&w, dst, src, nbytes);
194    return crypt(desc, &w, ctx,
195             crypto_cipher_alg(ctx->child)->cia_encrypt);
196}
197
198static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
199           struct scatterlist *src, unsigned int nbytes)
200{
201    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
202    struct blkcipher_walk w;
203
204    blkcipher_walk_init(&w, dst, src, nbytes);
205    return crypt(desc, &w, ctx,
206             crypto_cipher_alg(ctx->child)->cia_decrypt);
207}
208
209static int init_tfm(struct crypto_tfm *tfm)
210{
211    struct crypto_cipher *cipher;
212    struct crypto_instance *inst = (void *)tfm->__crt_alg;
213    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
214    struct priv *ctx = crypto_tfm_ctx(tfm);
215    u32 *flags = &tfm->crt_flags;
216
217    cipher = crypto_spawn_cipher(spawn);
218    if (IS_ERR(cipher))
219        return PTR_ERR(cipher);
220
221    if (crypto_cipher_blocksize(cipher) != 16) {
222        *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
223        return -EINVAL;
224    }
225
226    ctx->child = cipher;
227    return 0;
228}
229
230static void exit_tfm(struct crypto_tfm *tfm)
231{
232    struct priv *ctx = crypto_tfm_ctx(tfm);
233    if (ctx->table)
234        gf128mul_free_64k(ctx->table);
235    crypto_free_cipher(ctx->child);
236}
237
238static struct crypto_instance *alloc(struct rtattr **tb)
239{
240    struct crypto_instance *inst;
241    struct crypto_alg *alg;
242    int err;
243
244    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
245    if (err)
246        return ERR_PTR(err);
247
248    alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
249                  CRYPTO_ALG_TYPE_MASK);
250    if (IS_ERR(alg))
251        return ERR_CAST(alg);
252
253    inst = crypto_alloc_instance("lrw", alg);
254    if (IS_ERR(inst))
255        goto out_put_alg;
256
257    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
258    inst->alg.cra_priority = alg->cra_priority;
259    inst->alg.cra_blocksize = alg->cra_blocksize;
260
261    if (alg->cra_alignmask < 7) inst->alg.cra_alignmask = 7;
262    else inst->alg.cra_alignmask = alg->cra_alignmask;
263    inst->alg.cra_type = &crypto_blkcipher_type;
264
265    if (!(alg->cra_blocksize % 4))
266        inst->alg.cra_alignmask |= 3;
267    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
268    inst->alg.cra_blkcipher.min_keysize =
269        alg->cra_cipher.cia_min_keysize + alg->cra_blocksize;
270    inst->alg.cra_blkcipher.max_keysize =
271        alg->cra_cipher.cia_max_keysize + alg->cra_blocksize;
272
273    inst->alg.cra_ctxsize = sizeof(struct priv);
274
275    inst->alg.cra_init = init_tfm;
276    inst->alg.cra_exit = exit_tfm;
277
278    inst->alg.cra_blkcipher.setkey = setkey;
279    inst->alg.cra_blkcipher.encrypt = encrypt;
280    inst->alg.cra_blkcipher.decrypt = decrypt;
281
282out_put_alg:
283    crypto_mod_put(alg);
284    return inst;
285}
286
287static void free(struct crypto_instance *inst)
288{
289    crypto_drop_spawn(crypto_instance_ctx(inst));
290    kfree(inst);
291}
292
293static struct crypto_template crypto_tmpl = {
294    .name = "lrw",
295    .alloc = alloc,
296    .free = free,
297    .module = THIS_MODULE,
298};
299
300static int __init crypto_module_init(void)
301{
302    return crypto_register_template(&crypto_tmpl);
303}
304
305static void __exit crypto_module_exit(void)
306{
307    crypto_unregister_template(&crypto_tmpl);
308}
309
310module_init(crypto_module_init);
311module_exit(crypto_module_exit);
312
313MODULE_LICENSE("GPL");
314MODULE_DESCRIPTION("LRW block cipher mode");
315

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