Root/crypto/pcbc.c

1/*
2 * PCBC: Propagating Cipher Block Chaining mode
3 *
4 * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells (dhowells@redhat.com)
6 *
7 * Derived from cbc.c
8 * - Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
9 *
10 * This program is free software; you can redistribute it and/or modify it
11 * under the terms of the GNU General Public License as published by the Free
12 * Software Foundation; either version 2 of the License, or (at your option)
13 * any later version.
14 *
15 */
16
17#include <crypto/algapi.h>
18#include <linux/err.h>
19#include <linux/init.h>
20#include <linux/kernel.h>
21#include <linux/module.h>
22#include <linux/scatterlist.h>
23#include <linux/slab.h>
24
25struct crypto_pcbc_ctx {
26    struct crypto_cipher *child;
27};
28
29static int crypto_pcbc_setkey(struct crypto_tfm *parent, const u8 *key,
30                  unsigned int keylen)
31{
32    struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(parent);
33    struct crypto_cipher *child = ctx->child;
34    int err;
35
36    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
37    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
38                CRYPTO_TFM_REQ_MASK);
39    err = crypto_cipher_setkey(child, key, keylen);
40    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
41                 CRYPTO_TFM_RES_MASK);
42    return err;
43}
44
45static int crypto_pcbc_encrypt_segment(struct blkcipher_desc *desc,
46                       struct blkcipher_walk *walk,
47                       struct crypto_cipher *tfm)
48{
49    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
50        crypto_cipher_alg(tfm)->cia_encrypt;
51    int bsize = crypto_cipher_blocksize(tfm);
52    unsigned int nbytes = walk->nbytes;
53    u8 *src = walk->src.virt.addr;
54    u8 *dst = walk->dst.virt.addr;
55    u8 *iv = walk->iv;
56
57    do {
58        crypto_xor(iv, src, bsize);
59        fn(crypto_cipher_tfm(tfm), dst, iv);
60        memcpy(iv, dst, bsize);
61        crypto_xor(iv, src, bsize);
62
63        src += bsize;
64        dst += bsize;
65    } while ((nbytes -= bsize) >= bsize);
66
67    return nbytes;
68}
69
70static int crypto_pcbc_encrypt_inplace(struct blkcipher_desc *desc,
71                       struct blkcipher_walk *walk,
72                       struct crypto_cipher *tfm)
73{
74    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
75        crypto_cipher_alg(tfm)->cia_encrypt;
76    int bsize = crypto_cipher_blocksize(tfm);
77    unsigned int nbytes = walk->nbytes;
78    u8 *src = walk->src.virt.addr;
79    u8 *iv = walk->iv;
80    u8 tmpbuf[bsize];
81
82    do {
83        memcpy(tmpbuf, src, bsize);
84        crypto_xor(iv, src, bsize);
85        fn(crypto_cipher_tfm(tfm), src, iv);
86        memcpy(iv, tmpbuf, bsize);
87        crypto_xor(iv, src, bsize);
88
89        src += bsize;
90    } while ((nbytes -= bsize) >= bsize);
91
92    memcpy(walk->iv, iv, bsize);
93
94    return nbytes;
95}
96
97static int crypto_pcbc_encrypt(struct blkcipher_desc *desc,
98                   struct scatterlist *dst, struct scatterlist *src,
99                   unsigned int nbytes)
100{
101    struct blkcipher_walk walk;
102    struct crypto_blkcipher *tfm = desc->tfm;
103    struct crypto_pcbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
104    struct crypto_cipher *child = ctx->child;
105    int err;
106
107    blkcipher_walk_init(&walk, dst, src, nbytes);
108    err = blkcipher_walk_virt(desc, &walk);
109
110    while ((nbytes = walk.nbytes)) {
111        if (walk.src.virt.addr == walk.dst.virt.addr)
112            nbytes = crypto_pcbc_encrypt_inplace(desc, &walk,
113                                 child);
114        else
115            nbytes = crypto_pcbc_encrypt_segment(desc, &walk,
116                                 child);
117        err = blkcipher_walk_done(desc, &walk, nbytes);
118    }
119
120    return err;
121}
122
123static int crypto_pcbc_decrypt_segment(struct blkcipher_desc *desc,
124                       struct blkcipher_walk *walk,
125                       struct crypto_cipher *tfm)
126{
127    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
128        crypto_cipher_alg(tfm)->cia_decrypt;
129    int bsize = crypto_cipher_blocksize(tfm);
130    unsigned int nbytes = walk->nbytes;
131    u8 *src = walk->src.virt.addr;
132    u8 *dst = walk->dst.virt.addr;
133    u8 *iv = walk->iv;
134
135    do {
136        fn(crypto_cipher_tfm(tfm), dst, src);
137        crypto_xor(dst, iv, bsize);
138        memcpy(iv, src, bsize);
139        crypto_xor(iv, dst, bsize);
140
141        src += bsize;
142        dst += bsize;
143    } while ((nbytes -= bsize) >= bsize);
144
145    memcpy(walk->iv, iv, bsize);
146
147    return nbytes;
148}
149
150static int crypto_pcbc_decrypt_inplace(struct blkcipher_desc *desc,
151                       struct blkcipher_walk *walk,
152                       struct crypto_cipher *tfm)
153{
154    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
155        crypto_cipher_alg(tfm)->cia_decrypt;
156    int bsize = crypto_cipher_blocksize(tfm);
157    unsigned int nbytes = walk->nbytes;
158    u8 *src = walk->src.virt.addr;
159    u8 *iv = walk->iv;
160    u8 tmpbuf[bsize];
161
162    do {
163        memcpy(tmpbuf, src, bsize);
164        fn(crypto_cipher_tfm(tfm), src, src);
165        crypto_xor(src, iv, bsize);
166        memcpy(iv, tmpbuf, bsize);
167        crypto_xor(iv, src, bsize);
168
169        src += bsize;
170    } while ((nbytes -= bsize) >= bsize);
171
172    memcpy(walk->iv, iv, bsize);
173
174    return nbytes;
175}
176
177static int crypto_pcbc_decrypt(struct blkcipher_desc *desc,
178                   struct scatterlist *dst, struct scatterlist *src,
179                   unsigned int nbytes)
180{
181    struct blkcipher_walk walk;
182    struct crypto_blkcipher *tfm = desc->tfm;
183    struct crypto_pcbc_ctx *ctx = crypto_blkcipher_ctx(tfm);
184    struct crypto_cipher *child = ctx->child;
185    int err;
186
187    blkcipher_walk_init(&walk, dst, src, nbytes);
188    err = blkcipher_walk_virt(desc, &walk);
189
190    while ((nbytes = walk.nbytes)) {
191        if (walk.src.virt.addr == walk.dst.virt.addr)
192            nbytes = crypto_pcbc_decrypt_inplace(desc, &walk,
193                                 child);
194        else
195            nbytes = crypto_pcbc_decrypt_segment(desc, &walk,
196                                 child);
197        err = blkcipher_walk_done(desc, &walk, nbytes);
198    }
199
200    return err;
201}
202
203static int crypto_pcbc_init_tfm(struct crypto_tfm *tfm)
204{
205    struct crypto_instance *inst = (void *)tfm->__crt_alg;
206    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
207    struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(tfm);
208    struct crypto_cipher *cipher;
209
210    cipher = crypto_spawn_cipher(spawn);
211    if (IS_ERR(cipher))
212        return PTR_ERR(cipher);
213
214    ctx->child = cipher;
215    return 0;
216}
217
218static void crypto_pcbc_exit_tfm(struct crypto_tfm *tfm)
219{
220    struct crypto_pcbc_ctx *ctx = crypto_tfm_ctx(tfm);
221    crypto_free_cipher(ctx->child);
222}
223
224static struct crypto_instance *crypto_pcbc_alloc(struct rtattr **tb)
225{
226    struct crypto_instance *inst;
227    struct crypto_alg *alg;
228    int err;
229
230    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
231    if (err)
232        return ERR_PTR(err);
233
234    alg = crypto_get_attr_alg(tb, CRYPTO_ALG_TYPE_CIPHER,
235                  CRYPTO_ALG_TYPE_MASK);
236    if (IS_ERR(alg))
237        return ERR_CAST(alg);
238
239    inst = crypto_alloc_instance("pcbc", alg);
240    if (IS_ERR(inst))
241        goto out_put_alg;
242
243    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
244    inst->alg.cra_priority = alg->cra_priority;
245    inst->alg.cra_blocksize = alg->cra_blocksize;
246    inst->alg.cra_alignmask = alg->cra_alignmask;
247    inst->alg.cra_type = &crypto_blkcipher_type;
248
249    /* We access the data as u32s when xoring. */
250    inst->alg.cra_alignmask |= __alignof__(u32) - 1;
251
252    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
253    inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
254    inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
255
256    inst->alg.cra_ctxsize = sizeof(struct crypto_pcbc_ctx);
257
258    inst->alg.cra_init = crypto_pcbc_init_tfm;
259    inst->alg.cra_exit = crypto_pcbc_exit_tfm;
260
261    inst->alg.cra_blkcipher.setkey = crypto_pcbc_setkey;
262    inst->alg.cra_blkcipher.encrypt = crypto_pcbc_encrypt;
263    inst->alg.cra_blkcipher.decrypt = crypto_pcbc_decrypt;
264
265out_put_alg:
266    crypto_mod_put(alg);
267    return inst;
268}
269
270static void crypto_pcbc_free(struct crypto_instance *inst)
271{
272    crypto_drop_spawn(crypto_instance_ctx(inst));
273    kfree(inst);
274}
275
276static struct crypto_template crypto_pcbc_tmpl = {
277    .name = "pcbc",
278    .alloc = crypto_pcbc_alloc,
279    .free = crypto_pcbc_free,
280    .module = THIS_MODULE,
281};
282
283static int __init crypto_pcbc_module_init(void)
284{
285    return crypto_register_template(&crypto_pcbc_tmpl);
286}
287
288static void __exit crypto_pcbc_module_exit(void)
289{
290    crypto_unregister_template(&crypto_pcbc_tmpl);
291}
292
293module_init(crypto_pcbc_module_init);
294module_exit(crypto_pcbc_module_exit);
295
296MODULE_LICENSE("GPL");
297MODULE_DESCRIPTION("PCBC block cipher algorithm");
298

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