[CRYPTO] ctr: Add countersize
[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 inline void __ctr_inc_byte(u8 *a, unsigned int size)
35 {
36         u8 *b = (a + size);
37         u8 c;
38
39         for (; size; size--) {
40                 c = *--b + 1;
41                 *b = c;
42                 if (c)
43                         break;
44         }
45 }
46
47 static void ctr_inc_quad(u8 *a, unsigned int size)
48 {
49         __be32 *b = (__be32 *)(a + size);
50         u32 c;
51
52         for (; size >= 4; size -=4) {
53                 c = be32_to_cpu(*--b) + 1;
54                 *b = cpu_to_be32(c);
55                 if (c)
56                         return;
57         }
58
59         __ctr_inc_byte(a, size);
60 }
61
62 static void xor_byte(u8 *a, const u8 *b, unsigned int bs)
63 {
64         for (; bs; bs--)
65                 *a++ ^= *b++;
66 }
67
68 static void xor_quad(u8 *dst, const u8 *src, unsigned int bs)
69 {
70         u32 *a = (u32 *)dst;
71         u32 *b = (u32 *)src;
72
73         for (; bs >= 4; bs -= 4)
74                 *a++ ^= *b++;
75
76         xor_byte((u8 *)a, (u8 *)b, bs);
77 }
78
79 static int crypto_ctr_setkey(struct crypto_tfm *parent, const u8 *key,
80                              unsigned int keylen)
81 {
82         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(parent);
83         struct crypto_cipher *child = ctx->child;
84         struct ctr_instance_ctx *ictx =
85                 crypto_instance_ctx(crypto_tfm_alg_instance(parent));
86         unsigned int noncelen = ictx->noncesize;
87         int err = 0;
88
89         /* the nonce is stored in bytes at end of key */
90         if (keylen < noncelen)
91                 return  -EINVAL;
92
93         memcpy(ctx->nonce, key + (keylen - noncelen), noncelen);
94
95         keylen -=  noncelen;
96
97         crypto_cipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
98         crypto_cipher_set_flags(child, crypto_tfm_get_flags(parent) &
99                                 CRYPTO_TFM_REQ_MASK);
100         err = crypto_cipher_setkey(child, key, keylen);
101         crypto_tfm_set_flags(parent, crypto_cipher_get_flags(child) &
102                              CRYPTO_TFM_RES_MASK);
103
104         return err;
105 }
106
107 static int crypto_ctr_crypt_segment(struct blkcipher_walk *walk,
108                                     struct crypto_cipher *tfm, u8 *ctrblk,
109                                     unsigned int countersize)
110 {
111         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
112                    crypto_cipher_alg(tfm)->cia_encrypt;
113         unsigned int bsize = crypto_cipher_blocksize(tfm);
114         unsigned long alignmask = crypto_cipher_alignmask(tfm);
115         u8 ks[bsize + alignmask];
116         u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
117         u8 *src = walk->src.virt.addr;
118         u8 *dst = walk->dst.virt.addr;
119         unsigned int nbytes = walk->nbytes;
120
121         do {
122                 /* create keystream */
123                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
124                 xor_quad(keystream, src, min(nbytes, bsize));
125
126                 /* copy result into dst */
127                 memcpy(dst, keystream, min(nbytes, bsize));
128
129                 /* increment counter in counterblock */
130                 ctr_inc_quad(ctrblk + (bsize - countersize), countersize);
131
132                 if (nbytes < bsize)
133                         break;
134
135                 src += bsize;
136                 dst += bsize;
137                 nbytes -= bsize;
138
139         } while (nbytes);
140
141         return 0;
142 }
143
144 static int crypto_ctr_crypt_inplace(struct blkcipher_walk *walk,
145                                     struct crypto_cipher *tfm, u8 *ctrblk,
146                                     unsigned int countersize)
147 {
148         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
149                    crypto_cipher_alg(tfm)->cia_encrypt;
150         unsigned int bsize = crypto_cipher_blocksize(tfm);
151         unsigned long alignmask = crypto_cipher_alignmask(tfm);
152         unsigned int nbytes = walk->nbytes;
153         u8 *src = walk->src.virt.addr;
154         u8 ks[bsize + alignmask];
155         u8 *keystream = (u8 *)ALIGN((unsigned long)ks, alignmask + 1);
156
157         do {
158                 /* create keystream */
159                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
160                 xor_quad(src, keystream, min(nbytes, bsize));
161
162                 /* increment counter in counterblock */
163                 ctr_inc_quad(ctrblk + (bsize - countersize), countersize);
164
165                 if (nbytes < bsize)
166                         break;
167
168                 src += bsize;
169                 nbytes -= bsize;
170
171         } while (nbytes);
172
173         return 0;
174 }
175
176 static int crypto_ctr_crypt(struct blkcipher_desc *desc,
177                               struct scatterlist *dst, struct scatterlist *src,
178                               unsigned int nbytes)
179 {
180         struct blkcipher_walk walk;
181         struct crypto_blkcipher *tfm = desc->tfm;
182         struct crypto_ctr_ctx *ctx = crypto_blkcipher_ctx(tfm);
183         struct crypto_cipher *child = ctx->child;
184         unsigned int bsize = crypto_cipher_blocksize(child);
185         struct ctr_instance_ctx *ictx =
186                 crypto_instance_ctx(crypto_tfm_alg_instance(&tfm->base));
187         unsigned long alignmask = crypto_cipher_alignmask(child);
188         u8 cblk[bsize + alignmask];
189         u8 *counterblk = (u8 *)ALIGN((unsigned long)cblk, alignmask + 1);
190         int err;
191
192         blkcipher_walk_init(&walk, dst, src, nbytes);
193         err = blkcipher_walk_virt_block(desc, &walk, bsize);
194
195         /* set up counter block */
196         memset(counterblk, 0 , bsize);
197         memcpy(counterblk, ctx->nonce, ictx->noncesize);
198         memcpy(counterblk + ictx->noncesize, walk.iv, ictx->ivsize);
199
200         /* initialize counter portion of counter block */
201         ctr_inc_quad(counterblk + (bsize - ictx->countersize),
202                      ictx->countersize);
203
204         while (walk.nbytes) {
205                 if (walk.src.virt.addr == walk.dst.virt.addr)
206                         nbytes = crypto_ctr_crypt_inplace(&walk, child,
207                                                           counterblk,
208                                                           ictx->countersize);
209                 else
210                         nbytes = crypto_ctr_crypt_segment(&walk, child,
211                                                           counterblk,
212                                                           ictx->countersize);
213
214                 err = blkcipher_walk_done(desc, &walk, nbytes);
215         }
216         return err;
217 }
218
219 static int crypto_ctr_init_tfm(struct crypto_tfm *tfm)
220 {
221         struct crypto_instance *inst = (void *)tfm->__crt_alg;
222         struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
223         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
224         struct crypto_cipher *cipher;
225
226         ctx->nonce = kzalloc(ictx->noncesize, GFP_KERNEL);
227         if (!ctx->nonce)
228                 return -ENOMEM;
229
230         cipher = crypto_spawn_cipher(&ictx->alg);
231         if (IS_ERR(cipher))
232                 return PTR_ERR(cipher);
233
234         ctx->child = cipher;
235
236         return 0;
237 }
238
239 static void crypto_ctr_exit_tfm(struct crypto_tfm *tfm)
240 {
241         struct crypto_ctr_ctx *ctx = crypto_tfm_ctx(tfm);
242
243         kfree(ctx->nonce);
244         crypto_free_cipher(ctx->child);
245 }
246
247 static struct crypto_instance *crypto_ctr_alloc(struct rtattr **tb)
248 {
249         struct crypto_instance *inst;
250         struct crypto_alg *alg;
251         struct ctr_instance_ctx *ictx;
252         unsigned int noncesize;
253         unsigned int ivsize;
254         unsigned int countersize;
255         int err;
256
257         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
258         if (err)
259                 return ERR_PTR(err);
260
261         alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_CIPHER,
262                                   CRYPTO_ALG_TYPE_MASK);
263         if (IS_ERR(alg))
264                 return ERR_PTR(PTR_ERR(alg));
265
266         err = crypto_attr_u32(tb[2], &noncesize);
267         if (err)
268                 goto out_put_alg;
269
270         err = crypto_attr_u32(tb[3], &ivsize);
271         if (err)
272                 goto out_put_alg;
273
274         err = crypto_attr_u32(tb[4], &countersize);
275         if (err)
276                 goto out_put_alg;
277
278         /* verify size of nonce + iv + counter
279          * counter must be >= 4 bytes.
280          */
281         err = -EINVAL;
282         if (((noncesize + ivsize + countersize) < alg->cra_blocksize) ||
283             ((noncesize + ivsize) > alg->cra_blocksize) ||
284             (countersize > alg->cra_blocksize) || (countersize < 4))
285                 goto out_put_alg;
286
287         inst = kzalloc(sizeof(*inst) + sizeof(*ictx), GFP_KERNEL);
288         err = -ENOMEM;
289         if (!inst)
290                 goto out_put_alg;
291
292         err = -ENAMETOOLONG;
293         if (snprintf(inst->alg.cra_name, CRYPTO_MAX_ALG_NAME,
294                      "ctr(%s,%u,%u,%u)", alg->cra_name, noncesize,
295                      ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
296                 goto err_free_inst;
297         }
298
299         if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME,
300                      "ctr(%s,%u,%u,%u)", alg->cra_driver_name, noncesize,
301                      ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) {
302                 goto err_free_inst;
303         }
304
305         ictx = crypto_instance_ctx(inst);
306         ictx->noncesize = noncesize;
307         ictx->ivsize = ivsize;
308         ictx->countersize = countersize;
309
310         err = crypto_init_spawn(&ictx->alg, alg, inst,
311                 CRYPTO_ALG_TYPE_MASK | CRYPTO_ALG_ASYNC);
312         if (err)
313                 goto err_free_inst;
314
315         err = 0;
316         inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
317         inst->alg.cra_priority = alg->cra_priority;
318         inst->alg.cra_blocksize = 1;
319         inst->alg.cra_alignmask = 3;
320         inst->alg.cra_type = &crypto_blkcipher_type;
321
322         inst->alg.cra_blkcipher.ivsize = ivsize;
323         inst->alg.cra_blkcipher.min_keysize = alg->cra_cipher.cia_min_keysize
324                                               + noncesize;
325         inst->alg.cra_blkcipher.max_keysize = alg->cra_cipher.cia_max_keysize
326                                               + noncesize;
327
328         inst->alg.cra_ctxsize = sizeof(struct crypto_ctr_ctx);
329
330         inst->alg.cra_init = crypto_ctr_init_tfm;
331         inst->alg.cra_exit = crypto_ctr_exit_tfm;
332
333         inst->alg.cra_blkcipher.setkey = crypto_ctr_setkey;
334         inst->alg.cra_blkcipher.encrypt = crypto_ctr_crypt;
335         inst->alg.cra_blkcipher.decrypt = crypto_ctr_crypt;
336
337 err_free_inst:
338         if (err)
339                 kfree(inst);
340
341 out_put_alg:
342         crypto_mod_put(alg);
343
344         if (err)
345                 inst = ERR_PTR(err);
346
347         return inst;
348 }
349
350 static void crypto_ctr_free(struct crypto_instance *inst)
351 {
352         struct ctr_instance_ctx *ictx = crypto_instance_ctx(inst);
353
354         crypto_drop_spawn(&ictx->alg);
355         kfree(inst);
356 }
357
358 static struct crypto_template crypto_ctr_tmpl = {
359         .name = "ctr",
360         .alloc = crypto_ctr_alloc,
361         .free = crypto_ctr_free,
362         .module = THIS_MODULE,
363 };
364
365 static int __init crypto_ctr_module_init(void)
366 {
367         return crypto_register_template(&crypto_ctr_tmpl);
368 }
369
370 static void __exit crypto_ctr_module_exit(void)
371 {
372         crypto_unregister_template(&crypto_ctr_tmpl);
373 }
374
375 module_init(crypto_ctr_module_init);
376 module_exit(crypto_ctr_module_exit);
377
378 MODULE_LICENSE("GPL");
379 MODULE_DESCRIPTION("CTR Counter block mode");