Root/crypto/xts.c

1/* XTS: as defined in IEEE1619/D16
2 * http://grouper.ieee.org/groups/1619/email/pdf00086.pdf
3 * (sector sizes which are not a multiple of 16 bytes are,
4 * however currently unsupported)
5 *
6 * Copyright (c) 2007 Rik Snel <rsnel@cube.dyndns.org>
7 *
8 * Based om ecb.c
9 * Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
10 *
11 * This program is free software; you can redistribute it and/or modify it
12 * under the terms of the GNU General Public License as published by the Free
13 * Software Foundation; either version 2 of the License, or (at your option)
14 * any later version.
15 */
16#include <crypto/algapi.h>
17#include <linux/err.h>
18#include <linux/init.h>
19#include <linux/kernel.h>
20#include <linux/module.h>
21#include <linux/scatterlist.h>
22#include <linux/slab.h>
23
24#include <crypto/xts.h>
25#include <crypto/b128ops.h>
26#include <crypto/gf128mul.h>
27
28struct priv {
29    struct crypto_cipher *child;
30    struct crypto_cipher *tweak;
31};
32
33static int setkey(struct crypto_tfm *parent, const u8 *key,
34          unsigned int keylen)
35{
36    struct priv *ctx = crypto_tfm_ctx(parent);
37    struct crypto_cipher *child = ctx->tweak;
38    u32 *flags = &parent->crt_flags;
39    int err;
40
41    /* key consists of keys of equal size concatenated, therefore
42     * the length must be even */
43    if (keylen % 2) {
44        /* tell the user why there was an error */
45        *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
46        return -EINVAL;
47    }
48
49    /* we need two cipher instances: one to compute the initial 'tweak'
50     * by encrypting the IV (usually the 'plain' iv) and the other
51     * one to encrypt and decrypt the data */
52
53    /* tweak cipher, uses Key2 i.e. the second half of *key */
54    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
55    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
56                       CRYPTO_TFM_REQ_MASK);
57    err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
58    if (err)
59        return err;
60
61    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
62                     CRYPTO_TFM_RES_MASK);
63
64    child = ctx->child;
65
66    /* data cipher, uses Key1 i.e. the first half of *key */
67    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
68    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
69                       CRYPTO_TFM_REQ_MASK);
70    err = crypto_cipher_setkey(child, key, keylen/2);
71    if (err)
72        return err;
73
74    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
75                     CRYPTO_TFM_RES_MASK);
76
77    return 0;
78}
79
80struct sinfo {
81    be128 *t;
82    struct crypto_tfm *tfm;
83    void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
84};
85
86static inline void xts_round(struct sinfo *s, void *dst, const void *src)
87{
88    be128_xor(dst, s->t, src); /* PP <- T xor P */
89    s->fn(s->tfm, dst, dst); /* CC <- E(Key1,PP) */
90    be128_xor(dst, dst, s->t); /* C <- T xor CC */
91}
92
93static int crypt(struct blkcipher_desc *d,
94         struct blkcipher_walk *w, struct priv *ctx,
95         void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
96         void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
97{
98    int err;
99    unsigned int avail;
100    const int bs = XTS_BLOCK_SIZE;
101    struct sinfo s = {
102        .tfm = crypto_cipher_tfm(ctx->child),
103        .fn = fn
104    };
105    u8 *wsrc;
106    u8 *wdst;
107
108    err = blkcipher_walk_virt(d, w);
109    if (!w->nbytes)
110        return err;
111
112    s.t = (be128 *)w->iv;
113    avail = w->nbytes;
114
115    wsrc = w->src.virt.addr;
116    wdst = w->dst.virt.addr;
117
118    /* calculate first value of T */
119    tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv);
120
121    goto first;
122
123    for (;;) {
124        do {
125            gf128mul_x_ble(s.t, s.t);
126
127first:
128            xts_round(&s, wdst, wsrc);
129
130            wsrc += bs;
131            wdst += bs;
132        } while ((avail -= bs) >= bs);
133
134        err = blkcipher_walk_done(d, w, avail);
135        if (!w->nbytes)
136            break;
137
138        avail = w->nbytes;
139
140        wsrc = w->src.virt.addr;
141        wdst = w->dst.virt.addr;
142    }
143
144    return err;
145}
146
147static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
148           struct scatterlist *src, unsigned int nbytes)
149{
150    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
151    struct blkcipher_walk w;
152
153    blkcipher_walk_init(&w, dst, src, nbytes);
154    return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
155             crypto_cipher_alg(ctx->child)->cia_encrypt);
156}
157
158static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
159           struct scatterlist *src, unsigned int nbytes)
160{
161    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
162    struct blkcipher_walk w;
163
164    blkcipher_walk_init(&w, dst, src, nbytes);
165    return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
166             crypto_cipher_alg(ctx->child)->cia_decrypt);
167}
168
169int xts_crypt(struct blkcipher_desc *desc, struct scatterlist *sdst,
170          struct scatterlist *ssrc, unsigned int nbytes,
171          struct xts_crypt_req *req)
172{
173    const unsigned int bsize = XTS_BLOCK_SIZE;
174    const unsigned int max_blks = req->tbuflen / bsize;
175    struct blkcipher_walk walk;
176    unsigned int nblocks;
177    be128 *src, *dst, *t;
178    be128 *t_buf = req->tbuf;
179    int err, i;
180
181    BUG_ON(max_blks < 1);
182
183    blkcipher_walk_init(&walk, sdst, ssrc, nbytes);
184
185    err = blkcipher_walk_virt(desc, &walk);
186    nbytes = walk.nbytes;
187    if (!nbytes)
188        return err;
189
190    nblocks = min(nbytes / bsize, max_blks);
191    src = (be128 *)walk.src.virt.addr;
192    dst = (be128 *)walk.dst.virt.addr;
193
194    /* calculate first value of T */
195    req->tweak_fn(req->tweak_ctx, (u8 *)&t_buf[0], walk.iv);
196
197    i = 0;
198    goto first;
199
200    for (;;) {
201        do {
202            for (i = 0; i < nblocks; i++) {
203                gf128mul_x_ble(&t_buf[i], t);
204first:
205                t = &t_buf[i];
206
207                /* PP <- T xor P */
208                be128_xor(dst + i, t, src + i);
209            }
210
211            /* CC <- E(Key2,PP) */
212            req->crypt_fn(req->crypt_ctx, (u8 *)dst,
213                      nblocks * bsize);
214
215            /* C <- T xor CC */
216            for (i = 0; i < nblocks; i++)
217                be128_xor(dst + i, dst + i, &t_buf[i]);
218
219            src += nblocks;
220            dst += nblocks;
221            nbytes -= nblocks * bsize;
222            nblocks = min(nbytes / bsize, max_blks);
223        } while (nblocks > 0);
224
225        *(be128 *)walk.iv = *t;
226
227        err = blkcipher_walk_done(desc, &walk, nbytes);
228        nbytes = walk.nbytes;
229        if (!nbytes)
230            break;
231
232        nblocks = min(nbytes / bsize, max_blks);
233        src = (be128 *)walk.src.virt.addr;
234        dst = (be128 *)walk.dst.virt.addr;
235    }
236
237    return err;
238}
239EXPORT_SYMBOL_GPL(xts_crypt);
240
241static int init_tfm(struct crypto_tfm *tfm)
242{
243    struct crypto_cipher *cipher;
244    struct crypto_instance *inst = (void *)tfm->__crt_alg;
245    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
246    struct priv *ctx = crypto_tfm_ctx(tfm);
247    u32 *flags = &tfm->crt_flags;
248
249    cipher = crypto_spawn_cipher(spawn);
250    if (IS_ERR(cipher))
251        return PTR_ERR(cipher);
252
253    if (crypto_cipher_blocksize(cipher) != XTS_BLOCK_SIZE) {
254        *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
255        crypto_free_cipher(cipher);
256        return -EINVAL;
257    }
258
259    ctx->child = cipher;
260
261    cipher = crypto_spawn_cipher(spawn);
262    if (IS_ERR(cipher)) {
263        crypto_free_cipher(ctx->child);
264        return PTR_ERR(cipher);
265    }
266
267    /* this check isn't really needed, leave it here just in case */
268    if (crypto_cipher_blocksize(cipher) != XTS_BLOCK_SIZE) {
269        crypto_free_cipher(cipher);
270        crypto_free_cipher(ctx->child);
271        *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
272        return -EINVAL;
273    }
274
275    ctx->tweak = cipher;
276
277    return 0;
278}
279
280static void exit_tfm(struct crypto_tfm *tfm)
281{
282    struct priv *ctx = crypto_tfm_ctx(tfm);
283    crypto_free_cipher(ctx->child);
284    crypto_free_cipher(ctx->tweak);
285}
286
287static struct crypto_instance *alloc(struct rtattr **tb)
288{
289    struct crypto_instance *inst;
290    struct crypto_alg *alg;
291    int err;
292
293    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
294    if (err)
295        return ERR_PTR(err);
296
297    alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
298                  CRYPTO_ALG_TYPE_MASK);
299    if (IS_ERR(alg))
300        return ERR_CAST(alg);
301
302    inst = crypto_alloc_instance("xts", alg);
303    if (IS_ERR(inst))
304        goto out_put_alg;
305
306    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
307    inst->alg.cra_priority = alg->cra_priority;
308    inst->alg.cra_blocksize = alg->cra_blocksize;
309
310    if (alg->cra_alignmask < 7)
311        inst->alg.cra_alignmask = 7;
312    else
313        inst->alg.cra_alignmask = alg->cra_alignmask;
314
315    inst->alg.cra_type = &crypto_blkcipher_type;
316
317    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
318    inst->alg.cra_blkcipher.min_keysize =
319        2 * alg->cra_cipher.cia_min_keysize;
320    inst->alg.cra_blkcipher.max_keysize =
321        2 * alg->cra_cipher.cia_max_keysize;
322
323    inst->alg.cra_ctxsize = sizeof(struct priv);
324
325    inst->alg.cra_init = init_tfm;
326    inst->alg.cra_exit = exit_tfm;
327
328    inst->alg.cra_blkcipher.setkey = setkey;
329    inst->alg.cra_blkcipher.encrypt = encrypt;
330    inst->alg.cra_blkcipher.decrypt = decrypt;
331
332out_put_alg:
333    crypto_mod_put(alg);
334    return inst;
335}
336
337static void free(struct crypto_instance *inst)
338{
339    crypto_drop_spawn(crypto_instance_ctx(inst));
340    kfree(inst);
341}
342
343static struct crypto_template crypto_tmpl = {
344    .name = "xts",
345    .alloc = alloc,
346    .free = free,
347    .module = THIS_MODULE,
348};
349
350static int __init crypto_module_init(void)
351{
352    return crypto_register_template(&crypto_tmpl);
353}
354
355static void __exit crypto_module_exit(void)
356{
357    crypto_unregister_template(&crypto_tmpl);
358}
359
360module_init(crypto_module_init);
361module_exit(crypto_module_exit);
362
363MODULE_LICENSE("GPL");
364MODULE_DESCRIPTION("XTS block cipher mode");
365

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