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/b128ops.h>
25#include <crypto/gf128mul.h>
26
27struct priv {
28    struct crypto_cipher *child;
29    struct crypto_cipher *tweak;
30};
31
32static int setkey(struct crypto_tfm *parent, const u8 *key,
33          unsigned int keylen)
34{
35    struct priv *ctx = crypto_tfm_ctx(parent);
36    struct crypto_cipher *child = ctx->tweak;
37    u32 *flags = &parent->crt_flags;
38    int err;
39
40    /* key consists of keys of equal size concatenated, therefore
41     * the length must be even */
42    if (keylen % 2) {
43        /* tell the user why there was an error */
44        *flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
45        return -EINVAL;
46    }
47
48    /* we need two cipher instances: one to compute the inital 'tweak'
49     * by encrypting the IV (usually the 'plain' iv) and the other
50     * one to encrypt and decrypt the data */
51
52    /* tweak cipher, uses Key2 i.e. the second half of *key */
53    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
54    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
55                       CRYPTO_TFM_REQ_MASK);
56    err = crypto_cipher_setkey(child, key + keylen/2, keylen/2);
57    if (err)
58        return err;
59
60    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
61                     CRYPTO_TFM_RES_MASK);
62
63    child = ctx->child;
64
65    /* data cipher, uses Key1 i.e. the first half of *key */
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    err = crypto_cipher_setkey(child, key, keylen/2);
70    if (err)
71        return err;
72
73    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
74                     CRYPTO_TFM_RES_MASK);
75
76    return 0;
77}
78
79struct sinfo {
80    be128 *t;
81    struct crypto_tfm *tfm;
82    void (*fn)(struct crypto_tfm *, u8 *, const u8 *);
83};
84
85static inline void xts_round(struct sinfo *s, void *dst, const void *src)
86{
87    be128_xor(dst, s->t, src); /* PP <- T xor P */
88    s->fn(s->tfm, dst, dst); /* CC <- E(Key1,PP) */
89    be128_xor(dst, dst, s->t); /* C <- T xor CC */
90}
91
92static int crypt(struct blkcipher_desc *d,
93         struct blkcipher_walk *w, struct priv *ctx,
94         void (*tw)(struct crypto_tfm *, u8 *, const u8 *),
95         void (*fn)(struct crypto_tfm *, u8 *, const u8 *))
96{
97    int err;
98    unsigned int avail;
99    const int bs = crypto_cipher_blocksize(ctx->child);
100    struct sinfo s = {
101        .tfm = crypto_cipher_tfm(ctx->child),
102        .fn = fn
103    };
104    u8 *wsrc;
105    u8 *wdst;
106
107    err = blkcipher_walk_virt(d, w);
108    if (!w->nbytes)
109        return err;
110
111    s.t = (be128 *)w->iv;
112    avail = w->nbytes;
113
114    wsrc = w->src.virt.addr;
115    wdst = w->dst.virt.addr;
116
117    /* calculate first value of T */
118    tw(crypto_cipher_tfm(ctx->tweak), w->iv, w->iv);
119
120    goto first;
121
122    for (;;) {
123        do {
124            gf128mul_x_ble(s.t, s.t);
125
126first:
127            xts_round(&s, wdst, wsrc);
128
129            wsrc += bs;
130            wdst += bs;
131        } while ((avail -= bs) >= bs);
132
133        err = blkcipher_walk_done(d, w, avail);
134        if (!w->nbytes)
135            break;
136
137        avail = w->nbytes;
138
139        wsrc = w->src.virt.addr;
140        wdst = w->dst.virt.addr;
141    }
142
143    return err;
144}
145
146static int encrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
147           struct scatterlist *src, unsigned int nbytes)
148{
149    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
150    struct blkcipher_walk w;
151
152    blkcipher_walk_init(&w, dst, src, nbytes);
153    return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
154             crypto_cipher_alg(ctx->child)->cia_encrypt);
155}
156
157static int decrypt(struct blkcipher_desc *desc, struct scatterlist *dst,
158           struct scatterlist *src, unsigned int nbytes)
159{
160    struct priv *ctx = crypto_blkcipher_ctx(desc->tfm);
161    struct blkcipher_walk w;
162
163    blkcipher_walk_init(&w, dst, src, nbytes);
164    return crypt(desc, &w, ctx, crypto_cipher_alg(ctx->tweak)->cia_encrypt,
165             crypto_cipher_alg(ctx->child)->cia_decrypt);
166}
167
168static int init_tfm(struct crypto_tfm *tfm)
169{
170    struct crypto_cipher *cipher;
171    struct crypto_instance *inst = (void *)tfm->__crt_alg;
172    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
173    struct priv *ctx = crypto_tfm_ctx(tfm);
174    u32 *flags = &tfm->crt_flags;
175
176    cipher = crypto_spawn_cipher(spawn);
177    if (IS_ERR(cipher))
178        return PTR_ERR(cipher);
179
180    if (crypto_cipher_blocksize(cipher) != 16) {
181        *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
182        crypto_free_cipher(cipher);
183        return -EINVAL;
184    }
185
186    ctx->child = cipher;
187
188    cipher = crypto_spawn_cipher(spawn);
189    if (IS_ERR(cipher)) {
190        crypto_free_cipher(ctx->child);
191        return PTR_ERR(cipher);
192    }
193
194    /* this check isn't really needed, leave it here just in case */
195    if (crypto_cipher_blocksize(cipher) != 16) {
196        crypto_free_cipher(cipher);
197        crypto_free_cipher(ctx->child);
198        *flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
199        return -EINVAL;
200    }
201
202    ctx->tweak = cipher;
203
204    return 0;
205}
206
207static void exit_tfm(struct crypto_tfm *tfm)
208{
209    struct priv *ctx = crypto_tfm_ctx(tfm);
210    crypto_free_cipher(ctx->child);
211    crypto_free_cipher(ctx->tweak);
212}
213
214static struct crypto_instance *alloc(struct rtattr **tb)
215{
216    struct crypto_instance *inst;
217    struct crypto_alg *alg;
218    int err;
219
220    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
221    if (err)
222        return ERR_PTR(err);
223
224    alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
225                  CRYPTO_ALG_TYPE_MASK);
226    if (IS_ERR(alg))
227        return ERR_PTR(PTR_ERR(alg));
228
229    inst = crypto_alloc_instance("xts", alg);
230    if (IS_ERR(inst))
231        goto out_put_alg;
232
233    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
234    inst->alg.cra_priority = alg->cra_priority;
235    inst->alg.cra_blocksize = alg->cra_blocksize;
236
237    if (alg->cra_alignmask < 7)
238        inst->alg.cra_alignmask = 7;
239    else
240        inst->alg.cra_alignmask = alg->cra_alignmask;
241
242    inst->alg.cra_type = &crypto_blkcipher_type;
243
244    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
245    inst->alg.cra_blkcipher.min_keysize =
246        2 * alg->cra_cipher.cia_min_keysize;
247    inst->alg.cra_blkcipher.max_keysize =
248        2 * alg->cra_cipher.cia_max_keysize;
249
250    inst->alg.cra_ctxsize = sizeof(struct priv);
251
252    inst->alg.cra_init = init_tfm;
253    inst->alg.cra_exit = exit_tfm;
254
255    inst->alg.cra_blkcipher.setkey = setkey;
256    inst->alg.cra_blkcipher.encrypt = encrypt;
257    inst->alg.cra_blkcipher.decrypt = decrypt;
258
259out_put_alg:
260    crypto_mod_put(alg);
261    return inst;
262}
263
264static void free(struct crypto_instance *inst)
265{
266    crypto_drop_spawn(crypto_instance_ctx(inst));
267    kfree(inst);
268}
269
270static struct crypto_template crypto_tmpl = {
271    .name = "xts",
272    .alloc = alloc,
273    .free = free,
274    .module = THIS_MODULE,
275};
276
277static int __init crypto_module_init(void)
278{
279    return crypto_register_template(&crypto_tmpl);
280}
281
282static void __exit crypto_module_exit(void)
283{
284    crypto_unregister_template(&crypto_tmpl);
285}
286
287module_init(crypto_module_init);
288module_exit(crypto_module_exit);
289
290MODULE_LICENSE("GPL");
291MODULE_DESCRIPTION("XTS block cipher mode");
292

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