[CRYPTO] ctr: Use crypto_inc and crypto_xor
[linux-2.6.git] / 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 <linux/err.h>
15 #include <linux/init.h>
16 #include <linux/kernel.h>
17 #include <linux/module.h>
18 #include <linux/random.h>
19 #include <linux/scatterlist.h>
20 #include <linux/slab.h>
21
22 struct ctr_instance_ctx {
23         struct crypto_spawn alg;
24         unsigned int noncesize;
25         unsigned int ivsize;
26         unsigned int countersize;
27 };
28
29 struct crypto_ctr_ctx {
30         struct crypto_cipher *child;
31         u8 *nonce;
32 };
33
34 static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
35                              unsigned int keylen)
36 {
37         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
38         struct crypto_cipher *child = ctx->child;
39         struct ctr_instance_ctx *ictx =
40                 crypto_instance_ctx(crypto_tfm_alg_instance(parent));
41         unsigned int noncelen = ictx->noncesize;
42         int err = 0;
43
44         /* the nonce is stored in bytes at end of key */
45         if (keylen < noncelen)
46                 return  -EINVAL;
47
48         memcpy(ctx->nonce, key + (keylen - noncelen), noncelen);
49
50         keylen -=  noncelen;
51
52         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
53         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
54                                 CRYPTO_TFM_REQ_MASK);
55         err = crypto_cipher_setkey(child, key, keylen);
56         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
57                              CRYPTO_TFM_RES_MASK);
58
59         return err;
60 }
61
62 static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
63                                     struct crypto_cipher *tfm, u8 *ctrblk,
64                                     unsigned int countersize)
65 {
66         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
67                    crypto_cipher_alg(tfm)->cia_encrypt;
68         unsigned int bsize = crypto_cipher_blocksize(tfm);
69         unsigned long alignmask = crypto_cipher_alignmask(tfm) |
70                                   (__alignof__(u32) - 1);
71         u8 ks[bsize + alignmask];
72         u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
73         u8 *src = walk->src.virt.addr;
74         u8 *dst = walk->dst.virt.addr;
75         unsigned int nbytes = walk->nbytes;
76
77         do {
78                 /* create keystream */
79                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
80                 crypto_xor(keystream, src, min(nbytes, bsize));
81
82                 /* copy result into dst */
83                 memcpy(dst, keystream, min(nbytes, bsize));
84
85                 /* increment counter in counterblock */
86                 crypto_inc(ctrblk + bsize - countersize, countersize);
87
88                 if (nbytes < bsize)
89                         break;
90
91                 src += bsize;
92                 dst += bsize;
93                 nbytes -= bsize;
94
95         } while (nbytes);
96
97         return 0;
98 }
99
100 static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
101                                     struct crypto_cipher *tfm, u8 *ctrblk,
102                                     unsigned int countersize)
103 {
104         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
105                    crypto_cipher_alg(tfm)->cia_encrypt;
106         unsigned int bsize = crypto_cipher_blocksize(tfm);
107         unsigned long alignmask = crypto_cipher_alignmask(tfm) |
108                                   (__alignof__(u32) - 1);
109         unsigned int nbytes = walk->nbytes;
110         u8 *src = walk->src.virt.addr;
111         u8 ks[bsize + alignmask];
112         u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
113
114         do {
115                 /* create keystream */
116                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
117                 crypto_xor(src, keystream, min(nbytes, bsize));
118
119                 /* increment counter in counterblock */
120                 crypto_inc(ctrblk + bsize - countersize, countersize);
121
122                 if (nbytes < bsize)
123                         break;
124
125                 src += bsize;
126                 nbytes -= bsize;
127
128         } while (nbytes);
129
130         return 0;
131 }
132
133 static int crypto_ctr_crypt(struct blkcipher_desc *desc,
134                               struct scatterlist *dst, struct scatterlist *src,
135                               unsigned int nbytes)
136 {
137         struct blkcipher_walk walk;
138         struct crypto_blkcipher *tfm = desc->tfm;
139         struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
140         struct crypto_cipher *child = ctx->child;
141         unsigned int bsize = crypto_cipher_blocksize(child);
142         struct ctr_instance_ctx *ictx =
143                 crypto_instance_ctx(crypto_tfm_alg_instance(&tfm->base));
144         unsigned long alignmask = crypto_cipher_alignmask(child) |
145                                   (__alignof__(u32) - 1);
146         u8 cblk[bsize + alignmask];
147         u8 *counterblk = (u8 *)ALIGN((unsigned long)cblk, alignmask + 1);
148         int err;
149
150         blkcipher_walk_init(&walk, dst, src, nbytes);
151         err = blkcipher_walk_virt_block(desc, &walk, bsize);
152
153         /* set up counter block */
154         memset(counterblk, 0 , bsize);
155         memcpy(counterblk, ctx->nonce, ictx->noncesize);
156         memcpy(counterblk + ictx->noncesize, walk.iv, ictx->ivsize);
157
158         /* initialize counter portion of counter block */
159         crypto_inc(counterblk + bsize - ictx->countersize, ictx->countersize);
160
161         while (walk.nbytes) {
162                 if (walk.src.virt.addr == walk.dst.virt.addr)
163                         nbytes = crypto_ctr_crypt_inplace(&walk, child,
164                                                           counterblk,
165                                                           ictx->countersize);
166                 else
167                         nbytes = crypto_ctr_crypt_segment(&walk, child,
168                                                           counterblk,
169                                                           ictx->countersize);
170
171                 err = blkcipher_walk_done(desc, &walk, nbytes);
172         }
173         return err;
174 }
175
176 static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
177 {
178         struct crypto_instance *inst = (void *)tfm->__crt_alg;
179         struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
180         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
181         struct crypto_cipher *cipher;
182
183         ctx->nonce = kzalloc(ictx->noncesize, GFP_KERNEL);
184         if (!ctx->nonce)
185                 return -ENOMEM;
186
187         cipher = crypto_spawn_cipher(&ictx->alg);
188         if (IS_ERR(cipher))
189                 return PTR_ERR(cipher);
190
191         ctx->child = cipher;
192
193         return 0;
194 }
195
196 static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
197 {
198         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
199
200         kfree(ctx->nonce);
201         crypto_free_cipher(ctx->child);
202 }
203
204 static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
205 {
206         struct crypto_instance *inst;
207         struct crypto_alg *alg;
208         struct ctr_instance_ctx *ictx;
209         unsigned int noncesize;
210         unsigned int ivsize;
211         unsigned int countersize;
212         int err;
213
214         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
215         if (err)
216                 return ERR_PTR(err);
217
218         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
219                                   CRYPTO_ALG_TYPE_MASK);
220         if (IS_ERR(alg))
221                 return ERR_PTR(PTR_ERR(alg));
222
223         err = crypto_attr_u32(tb[2], &noncesize);
224         if (err)
225                 goto out_put_alg;
226
227         err = crypto_attr_u32(tb[3], &ivsize);
228         if (err)
229                 goto out_put_alg;
230
231         err = crypto_attr_u32(tb[4], &countersize);
232         if (err)
233                 goto out_put_alg;
234
235         /* verify size of nonce + iv + counter
236          * counter must be >= 4 bytes.
237          */
238         err = -EINVAL;
239         if (((noncesize + ivsize + countersize) < alg->cra_blocksize) ||
240             ((noncesize + ivsize) > alg->cra_blocksize) ||
241             (countersize > alg->cra_blocksize) || (countersize < 4))
242                 goto out_put_alg;
243
244         /* If this is false we'd fail the alignment of crypto_inc. */
245         if ((alg->cra_blocksize - countersize) % 4)
246                 goto out_put_alg;
247
248         inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
249         err = -ENOMEM;
250         if (!inst)
251                 goto out_put_alg;
252
253         err = -ENAMETOOLONG;
254         if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
255                      "ctr(%s,%u,%u,%u)", alg->cra_name, noncesize,
256                      ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
257                 goto err_free_inst;
258         }
259
260         if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
261                      "ctr(%s,%u,%u,%u)", alg->cra_driver_name, noncesize,
262                      ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
263                 goto err_free_inst;
264         }
265
266         ictx = crypto_instance_ctx(inst);
267         ictx->noncesize = noncesize;
268         ictx->ivsize = ivsize;
269         ictx->countersize = countersize;
270
271         err = crypto_init_spawn(&ictx->alg, alg, inst,
272                 CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
273         if (err)
274                 goto err_free_inst;
275
276         err = 0;
277         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
278         inst->alg.cra_priority = alg->cra_priority;
279         inst->alg.cra_blocksize = 1;
280         inst->alg.cra_alignmask = __alignof__(u32) - 1;
281         inst->alg.cra_type = &crypto_blkcipher_type;
282
283         inst->alg.cra_blkcipher.ivsize = ivsize;
284         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize
285                                               + noncesize;
286         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize
287                                               + noncesize;
288
289         inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
290
291         inst->alg.cra_init = crypto_ctr_init_tfm;
292         inst->alg.cra_exit = crypto_ctr_exit_tfm;
293
294         inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
295         inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
296         inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
297
298 err_free_inst:
299         if (err)
300                 kfree(inst);
301
302 out_put_alg:
303         crypto_mod_put(alg);
304
305         if (err)
306                 inst = ERR_PTR(err);
307
308         return inst;
309 }
310
311 static void crypto_ctr_free(struct crypto_instance *inst)
312 {
313         struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
314
315         crypto_drop_spawn(&ictx->alg);
316         kfree(inst);
317 }
318
319 static struct crypto_template crypto_ctr_tmpl = {
320         .name = "ctr",
321         .alloc = crypto_ctr_alloc,
322         .free = crypto_ctr_free,
323         .module = THIS_MODULE,
324 };
325
326 static int __init crypto_ctr_module_init(void)
327 {
328         return crypto_register_template(&crypto_ctr_tmpl);
329 }
330
331 static void __exit crypto_ctr_module_exit(void)
332 {
333         crypto_unregister_template(&crypto_ctr_tmpl);
334 }
335
336 module_init(crypto_ctr_module_init);
337 module_exit(crypto_ctr_module_exit);
338
339 MODULE_LICENSE("GPL");
340 MODULE_DESCRIPTION("CTR Counter block mode");