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23e353c8 JL |
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; | |
41fdab3d | 26 | unsigned int countersize; |
23e353c8 JL |
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); | |
23e353c8 JL |
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 */ | |
41fdab3d JL |
201 | ctr_inc_quad(counterblk + (bsize - ictx->countersize), |
202 | ictx->countersize); | |
23e353c8 JL |
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, | |
41fdab3d | 208 | ictx->countersize); |
23e353c8 JL |
209 | else |
210 | nbytes = crypto_ctr_crypt_segment(&walk, child, | |
211 | counterblk, | |
41fdab3d | 212 | ictx->countersize); |
23e353c8 JL |
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; | |
41fdab3d | 254 | unsigned int countersize; |
23e353c8 JL |
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 | ||
41fdab3d JL |
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 | */ | |
23e353c8 | 281 | err = -EINVAL; |
41fdab3d JL |
282 | if (((noncesize + ivsize + countersize) < alg->cra_blocksize) || |
283 | ((noncesize + ivsize) > alg->cra_blocksize) || | |
284 | (countersize > alg->cra_blocksize) || (countersize < 4)) | |
23e353c8 JL |
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, | |
41fdab3d JL |
294 | "ctr(%s,%u,%u,%u)", alg->cra_name, noncesize, |
295 | ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) { | |
23e353c8 JL |
296 | goto err_free_inst; |
297 | } | |
298 | ||
299 | if (snprintf(inst->alg.cra_driver_name, CRYPTO_MAX_ALG_NAME, | |
41fdab3d JL |
300 | "ctr(%s,%u,%u,%u)", alg->cra_driver_name, noncesize, |
301 | ivsize, countersize) >= CRYPTO_MAX_ALG_NAME) { | |
23e353c8 JL |
302 | goto err_free_inst; |
303 | } | |
304 | ||
305 | ictx = crypto_instance_ctx(inst); | |
306 | ictx->noncesize = noncesize; | |
307 | ictx->ivsize = ivsize; | |
41fdab3d | 308 | ictx->countersize = countersize; |
23e353c8 JL |
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"); |