Root/crypto/ctr.c

1/*
2 * CTR: Counter mode
3 *
4 * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
5 *
6 * This program is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License as published by the Free
8 * Software Foundation; either version 2 of the License, or (at your option)
9 * any later version.
10 *
11 */
12
13#include <crypto/algapi.h>
14#include <crypto/ctr.h>
15#include <linux/err.h>
16#include <linux/init.h>
17#include <linux/kernel.h>
18#include <linux/module.h>
19#include <linux/random.h>
20#include <linux/scatterlist.h>
21#include <linux/slab.h>
22
23struct crypto_ctr_ctx {
24    struct crypto_cipher *child;
25};
26
27struct crypto_rfc3686_ctx {
28    struct crypto_blkcipher *child;
29    u8 nonce[CTR_RFC3686_NONCE_SIZE];
30};
31
32static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
33                 unsigned int keylen)
34{
35    struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
36    struct crypto_cipher *child = ctx->child;
37    int err;
38
39    crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
40    crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
41                CRYPTO_TFM_REQ_MASK);
42    err = crypto_cipher_setkey(child, key, keylen);
43    crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
44                 CRYPTO_TFM_RES_MASK);
45
46    return err;
47}
48
49static void crypto_ctr_crypt_final(struct blkcipher_walk *walk,
50                   struct crypto_cipher *tfm)
51{
52    unsigned int bsize = crypto_cipher_blocksize(tfm);
53    unsigned long alignmask = crypto_cipher_alignmask(tfm);
54    u8 *ctrblk = walk->iv;
55    u8 tmp[bsize + alignmask];
56    u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
57    u8 *src = walk->src.virt.addr;
58    u8 *dst = walk->dst.virt.addr;
59    unsigned int nbytes = walk->nbytes;
60
61    crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
62    crypto_xor(keystream, src, nbytes);
63    memcpy(dst, keystream, nbytes);
64
65    crypto_inc(ctrblk, bsize);
66}
67
68static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
69                    struct crypto_cipher *tfm)
70{
71    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
72           crypto_cipher_alg(tfm)->cia_encrypt;
73    unsigned int bsize = crypto_cipher_blocksize(tfm);
74    u8 *ctrblk = walk->iv;
75    u8 *src = walk->src.virt.addr;
76    u8 *dst = walk->dst.virt.addr;
77    unsigned int nbytes = walk->nbytes;
78
79    do {
80        /* create keystream */
81        fn(crypto_cipher_tfm(tfm), dst, ctrblk);
82        crypto_xor(dst, src, bsize);
83
84        /* increment counter in counterblock */
85        crypto_inc(ctrblk, bsize);
86
87        src += bsize;
88        dst += bsize;
89    } while ((nbytes -= bsize) >= bsize);
90
91    return nbytes;
92}
93
94static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
95                    struct crypto_cipher *tfm)
96{
97    void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
98           crypto_cipher_alg(tfm)->cia_encrypt;
99    unsigned int bsize = crypto_cipher_blocksize(tfm);
100    unsigned long alignmask = crypto_cipher_alignmask(tfm);
101    unsigned int nbytes = walk->nbytes;
102    u8 *ctrblk = walk->iv;
103    u8 *src = walk->src.virt.addr;
104    u8 tmp[bsize + alignmask];
105    u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
106
107    do {
108        /* create keystream */
109        fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
110        crypto_xor(src, keystream, bsize);
111
112        /* increment counter in counterblock */
113        crypto_inc(ctrblk, bsize);
114
115        src += bsize;
116    } while ((nbytes -= bsize) >= bsize);
117
118    return nbytes;
119}
120
121static int crypto_ctr_crypt(struct blkcipher_desc *desc,
122                  struct scatterlist *dst, struct scatterlist *src,
123                  unsigned int nbytes)
124{
125    struct blkcipher_walk walk;
126    struct crypto_blkcipher *tfm = desc->tfm;
127    struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
128    struct crypto_cipher *child = ctx->child;
129    unsigned int bsize = crypto_cipher_blocksize(child);
130    int err;
131
132    blkcipher_walk_init(&walk, dst, src, nbytes);
133    err = blkcipher_walk_virt_block(desc, &walk, bsize);
134
135    while (walk.nbytes >= bsize) {
136        if (walk.src.virt.addr == walk.dst.virt.addr)
137            nbytes = crypto_ctr_crypt_inplace(&walk, child);
138        else
139            nbytes = crypto_ctr_crypt_segment(&walk, child);
140
141        err = blkcipher_walk_done(desc, &walk, nbytes);
142    }
143
144    if (walk.nbytes) {
145        crypto_ctr_crypt_final(&walk, child);
146        err = blkcipher_walk_done(desc, &walk, 0);
147    }
148
149    return err;
150}
151
152static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
153{
154    struct crypto_instance *inst = (void *)tfm->__crt_alg;
155    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
156    struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
157    struct crypto_cipher *cipher;
158
159    cipher = crypto_spawn_cipher(spawn);
160    if (IS_ERR(cipher))
161        return PTR_ERR(cipher);
162
163    ctx->child = cipher;
164
165    return 0;
166}
167
168static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
169{
170    struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
171
172    crypto_free_cipher(ctx->child);
173}
174
175static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
176{
177    struct crypto_instance *inst;
178    struct crypto_alg *alg;
179    int err;
180
181    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
182    if (err)
183        return ERR_PTR(err);
184
185    alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
186                  CRYPTO_ALG_TYPE_MASK);
187    if (IS_ERR(alg))
188        return ERR_CAST(alg);
189
190    /* Block size must be >= 4 bytes. */
191    err = -EINVAL;
192    if (alg->cra_blocksize < 4)
193        goto out_put_alg;
194
195    /* If this is false we'd fail the alignment of crypto_inc. */
196    if (alg->cra_blocksize % 4)
197        goto out_put_alg;
198
199    inst = crypto_alloc_instance("ctr", alg);
200    if (IS_ERR(inst))
201        goto out;
202
203    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
204    inst->alg.cra_priority = alg->cra_priority;
205    inst->alg.cra_blocksize = 1;
206    inst->alg.cra_alignmask = alg->cra_alignmask | (__alignof__(u32) - 1);
207    inst->alg.cra_type = &crypto_blkcipher_type;
208
209    inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
210    inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize;
211    inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize;
212
213    inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
214
215    inst->alg.cra_init = crypto_ctr_init_tfm;
216    inst->alg.cra_exit = crypto_ctr_exit_tfm;
217
218    inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
219    inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
220    inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
221
222    inst->alg.cra_blkcipher.geniv = "chainiv";
223
224out:
225    crypto_mod_put(alg);
226    return inst;
227
228out_put_alg:
229    inst = ERR_PTR(err);
230    goto out;
231}
232
233static void crypto_ctr_free(struct crypto_instance *inst)
234{
235    crypto_drop_spawn(crypto_instance_ctx(inst));
236    kfree(inst);
237}
238
239static struct crypto_template crypto_ctr_tmpl = {
240    .name = "ctr",
241    .alloc = crypto_ctr_alloc,
242    .free = crypto_ctr_free,
243    .module = THIS_MODULE,
244};
245
246static int crypto_rfc3686_setkey(struct crypto_tfm *parent, const u8 *key,
247                 unsigned int keylen)
248{
249    struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(parent);
250    struct crypto_blkcipher *child = ctx->child;
251    int err;
252
253    /* the nonce is stored in bytes at end of key */
254    if (keylen < CTR_RFC3686_NONCE_SIZE)
255        return -EINVAL;
256
257    memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
258           CTR_RFC3686_NONCE_SIZE);
259
260    keylen -= CTR_RFC3686_NONCE_SIZE;
261
262    crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
263    crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
264                      CRYPTO_TFM_REQ_MASK);
265    err = crypto_blkcipher_setkey(child, key, keylen);
266    crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
267                     CRYPTO_TFM_RES_MASK);
268
269    return err;
270}
271
272static int crypto_rfc3686_crypt(struct blkcipher_desc *desc,
273                struct scatterlist *dst,
274                struct scatterlist *src, unsigned int nbytes)
275{
276    struct crypto_blkcipher *tfm = desc->tfm;
277    struct crypto_rfc3686_ctx *ctx = crypto_blkcipher_ctx(tfm);
278    struct crypto_blkcipher *child = ctx->child;
279    unsigned long alignmask = crypto_blkcipher_alignmask(tfm);
280    u8 ivblk[CTR_RFC3686_BLOCK_SIZE + alignmask];
281    u8 *iv = PTR_ALIGN(ivblk + 0, alignmask + 1);
282    u8 *info = desc->info;
283    int err;
284
285    /* set up counter block */
286    memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
287    memcpy(iv + CTR_RFC3686_NONCE_SIZE, info, CTR_RFC3686_IV_SIZE);
288
289    /* initialize counter portion of counter block */
290    *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
291        cpu_to_be32(1);
292
293    desc->tfm = child;
294    desc->info = iv;
295    err = crypto_blkcipher_encrypt_iv(desc, dst, src, nbytes);
296    desc->tfm = tfm;
297    desc->info = info;
298
299    return err;
300}
301
302static int crypto_rfc3686_init_tfm(struct crypto_tfm *tfm)
303{
304    struct crypto_instance *inst = (void *)tfm->__crt_alg;
305    struct crypto_spawn *spawn = crypto_instance_ctx(inst);
306    struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
307    struct crypto_blkcipher *cipher;
308
309    cipher = crypto_spawn_blkcipher(spawn);
310    if (IS_ERR(cipher))
311        return PTR_ERR(cipher);
312
313    ctx->child = cipher;
314
315    return 0;
316}
317
318static void crypto_rfc3686_exit_tfm(struct crypto_tfm *tfm)
319{
320    struct crypto_rfc3686_ctx *ctx = crypto_tfm_ctx(tfm);
321
322    crypto_free_blkcipher(ctx->child);
323}
324
325static struct crypto_instance *crypto_rfc3686_alloc(struct rtattr **tb)
326{
327    struct crypto_instance *inst;
328    struct crypto_alg *alg;
329    int err;
330
331    err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
332    if (err)
333        return ERR_PTR(err);
334
335    alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
336                  CRYPTO_ALG_TYPE_MASK);
337    err = PTR_ERR(alg);
338    if (IS_ERR(alg))
339        return ERR_PTR(err);
340
341    /* We only support 16-byte blocks. */
342    err = -EINVAL;
343    if (alg->cra_blkcipher.ivsize != CTR_RFC3686_BLOCK_SIZE)
344        goto out_put_alg;
345
346    /* Not a stream cipher? */
347    if (alg->cra_blocksize != 1)
348        goto out_put_alg;
349
350    inst = crypto_alloc_instance("rfc3686", alg);
351    if (IS_ERR(inst))
352        goto out;
353
354    inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
355    inst->alg.cra_priority = alg->cra_priority;
356    inst->alg.cra_blocksize = 1;
357    inst->alg.cra_alignmask = alg->cra_alignmask;
358    inst->alg.cra_type = &crypto_blkcipher_type;
359
360    inst->alg.cra_blkcipher.ivsize = CTR_RFC3686_IV_SIZE;
361    inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize
362                          + CTR_RFC3686_NONCE_SIZE;
363    inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize
364                          + CTR_RFC3686_NONCE_SIZE;
365
366    inst->alg.cra_blkcipher.geniv = "seqiv";
367
368    inst->alg.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
369
370    inst->alg.cra_init = crypto_rfc3686_init_tfm;
371    inst->alg.cra_exit = crypto_rfc3686_exit_tfm;
372
373    inst->alg.cra_blkcipher.setkey = crypto_rfc3686_setkey;
374    inst->alg.cra_blkcipher.encrypt = crypto_rfc3686_crypt;
375    inst->alg.cra_blkcipher.decrypt = crypto_rfc3686_crypt;
376
377out:
378    crypto_mod_put(alg);
379    return inst;
380
381out_put_alg:
382    inst = ERR_PTR(err);
383    goto out;
384}
385
386static struct crypto_template crypto_rfc3686_tmpl = {
387    .name = "rfc3686",
388    .alloc = crypto_rfc3686_alloc,
389    .free = crypto_ctr_free,
390    .module = THIS_MODULE,
391};
392
393static int __init crypto_ctr_module_init(void)
394{
395    int err;
396
397    err = crypto_register_template(&crypto_ctr_tmpl);
398    if (err)
399        goto out;
400
401    err = crypto_register_template(&crypto_rfc3686_tmpl);
402    if (err)
403        goto out_drop_ctr;
404
405out:
406    return err;
407
408out_drop_ctr:
409    crypto_unregister_template(&crypto_ctr_tmpl);
410    goto out;
411}
412
413static void __exit crypto_ctr_module_exit(void)
414{
415    crypto_unregister_template(&crypto_rfc3686_tmpl);
416    crypto_unregister_template(&crypto_ctr_tmpl);
417}
418
419module_init(crypto_ctr_module_init);
420module_exit(crypto_ctr_module_exit);
421
422MODULE_LICENSE("GPL");
423MODULE_DESCRIPTION("CTR Counter block mode");
424MODULE_ALIAS("rfc3686");
425

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