Skip to content
This repository

HTTPS clone URL

Subversion checkout URL

You can clone with HTTPS or Subversion.

Download ZIP
tag: v2.6.29-rc4
Fetching contributors…

Cannot retrieve contributors at this time

file 353 lines (293 sloc) 10.045 kb
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353
/*
* CTS: Cipher Text Stealing mode
*
* COPYRIGHT (c) 2008
* The Regents of the University of Michigan
* ALL RIGHTS RESERVED
*
* Permission is granted to use, copy, create derivative works
* and redistribute this software and such derivative works
* for any purpose, so long as the name of The University of
* Michigan is not used in any advertising or publicity
* pertaining to the use of distribution of this software
* without specific, written prior authorization. If the
* above copyright notice or any other identification of the
* University of Michigan is included in any copy of any
* portion of this software, then the disclaimer below must
* also be included.
*
* THIS SOFTWARE IS PROVIDED AS IS, WITHOUT REPRESENTATION
* FROM THE UNIVERSITY OF MICHIGAN AS TO ITS FITNESS FOR ANY
* PURPOSE, AND WITHOUT WARRANTY BY THE UNIVERSITY OF
* MICHIGAN OF ANY KIND, EITHER EXPRESS OR IMPLIED, INCLUDING
* WITHOUT LIMITATION THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE
* REGENTS OF THE UNIVERSITY OF MICHIGAN SHALL NOT BE LIABLE
* FOR ANY DAMAGES, INCLUDING SPECIAL, INDIRECT, INCIDENTAL, OR
* CONSEQUENTIAL DAMAGES, WITH RESPECT TO ANY CLAIM ARISING
* OUT OF OR IN CONNECTION WITH THE USE OF THE SOFTWARE, EVEN
* IF IT HAS BEEN OR IS HEREAFTER ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGES.
*/

/* Derived from various:
* Copyright (c) 2006 Herbert Xu <herbert@gondor.apana.org.au>
*/

/*
* This is the Cipher Text Stealing mode as described by
* Section 8 of rfc2040 and referenced by rfc3962.
* rfc3962 includes errata information in its Appendix A.
*/

#include <crypto/algapi.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/log2.h>
#include <linux/module.h>
#include <linux/scatterlist.h>
#include <crypto/scatterwalk.h>
#include <linux/slab.h>

struct crypto_cts_ctx {
struct crypto_blkcipher *child;
};

static int crypto_cts_setkey(struct crypto_tfm *parent, const u8 *key,
unsigned int keylen)
{
struct crypto_cts_ctx *ctx = crypto_tfm_ctx(parent);
struct crypto_blkcipher *child = ctx->child;
int err;

crypto_blkcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
crypto_blkcipher_set_flags(child, crypto_tfm_get_flags(parent) &
CRYPTO_TFM_REQ_MASK);
err = crypto_blkcipher_setkey(child, key, keylen);
crypto_tfm_set_flags(parent, crypto_blkcipher_get_flags(child) &
CRYPTO_TFM_RES_MASK);
return err;
}

static int cts_cbc_encrypt(struct crypto_cts_ctx *ctx,
struct blkcipher_desc *desc,
struct scatterlist *dst,
struct scatterlist *src,
unsigned int offset,
unsigned int nbytes)
{
int bsize = crypto_blkcipher_blocksize(desc->tfm);
u8 tmp[bsize], tmp2[bsize];
struct blkcipher_desc lcldesc;
struct scatterlist sgsrc[1], sgdst[1];
int lastn = nbytes - bsize;
u8 iv[bsize];
u8 s[bsize * 2], d[bsize * 2];
int err;

if (lastn < 0)
return -EINVAL;

sg_init_table(sgsrc, 1);
sg_init_table(sgdst, 1);

memset(s, 0, sizeof(s));
scatterwalk_map_and_copy(s, src, offset, nbytes, 0);

memcpy(iv, desc->info, bsize);

lcldesc.tfm = ctx->child;
lcldesc.info = iv;
lcldesc.flags = desc->flags;

sg_set_buf(&sgsrc[0], s, bsize);
sg_set_buf(&sgdst[0], tmp, bsize);
err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);

memcpy(d + bsize, tmp, lastn);

lcldesc.info = tmp;

sg_set_buf(&sgsrc[0], s + bsize, bsize);
sg_set_buf(&sgdst[0], tmp2, bsize);
err = crypto_blkcipher_encrypt_iv(&lcldesc, sgdst, sgsrc, bsize);

memcpy(d, tmp2, bsize);

scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);

memcpy(desc->info, tmp2, bsize);

return err;
}

static int crypto_cts_encrypt(struct blkcipher_desc *desc,
struct scatterlist *dst, struct scatterlist *src,
unsigned int nbytes)
{
struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
int bsize = crypto_blkcipher_blocksize(desc->tfm);
int tot_blocks = (nbytes + bsize - 1) / bsize;
int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
struct blkcipher_desc lcldesc;
int err;

lcldesc.tfm = ctx->child;
lcldesc.info = desc->info;
lcldesc.flags = desc->flags;

if (tot_blocks == 1) {
err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src, bsize);
} else if (nbytes <= bsize * 2) {
err = cts_cbc_encrypt(ctx, desc, dst, src, 0, nbytes);
} else {
/* do normal function for tot_blocks - 2 */
err = crypto_blkcipher_encrypt_iv(&lcldesc, dst, src,
cbc_blocks * bsize);
if (err == 0) {
/* do cts for final two blocks */
err = cts_cbc_encrypt(ctx, desc, dst, src,
cbc_blocks * bsize,
nbytes - (cbc_blocks * bsize));
}
}

return err;
}

static int cts_cbc_decrypt(struct crypto_cts_ctx *ctx,
struct blkcipher_desc *desc,
struct scatterlist *dst,
struct scatterlist *src,
unsigned int offset,
unsigned int nbytes)
{
int bsize = crypto_blkcipher_blocksize(desc->tfm);
u8 tmp[bsize];
struct blkcipher_desc lcldesc;
struct scatterlist sgsrc[1], sgdst[1];
int lastn = nbytes - bsize;
u8 iv[bsize];
u8 s[bsize * 2], d[bsize * 2];
int err;

if (lastn < 0)
return -EINVAL;

sg_init_table(sgsrc, 1);
sg_init_table(sgdst, 1);

scatterwalk_map_and_copy(s, src, offset, nbytes, 0);

lcldesc.tfm = ctx->child;
lcldesc.info = iv;
lcldesc.flags = desc->flags;

/* 1. Decrypt Cn-1 (s) to create Dn (tmp)*/
memset(iv, 0, sizeof(iv));
sg_set_buf(&sgsrc[0], s, bsize);
sg_set_buf(&sgdst[0], tmp, bsize);
err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);
if (err)
return err;
/* 2. Pad Cn with zeros at the end to create C of length BB */
memset(iv, 0, sizeof(iv));
memcpy(iv, s + bsize, lastn);
/* 3. Exclusive-or Dn (tmp) with C (iv) to create Xn (tmp) */
crypto_xor(tmp, iv, bsize);
/* 4. Select the first Ln bytes of Xn (tmp) to create Pn */
memcpy(d + bsize, tmp, lastn);

/* 5. Append the tail (BB - Ln) bytes of Xn (tmp) to Cn to create En */
memcpy(s + bsize + lastn, tmp + lastn, bsize - lastn);
/* 6. Decrypt En to create Pn-1 */
memset(iv, 0, sizeof(iv));
sg_set_buf(&sgsrc[0], s + bsize, bsize);
sg_set_buf(&sgdst[0], d, bsize);
err = crypto_blkcipher_decrypt_iv(&lcldesc, sgdst, sgsrc, bsize);

/* XOR with previous block */
crypto_xor(d, desc->info, bsize);

scatterwalk_map_and_copy(d, dst, offset, nbytes, 1);

memcpy(desc->info, s, bsize);
return err;
}

static int crypto_cts_decrypt(struct blkcipher_desc *desc,
struct scatterlist *dst, struct scatterlist *src,
unsigned int nbytes)
{
struct crypto_cts_ctx *ctx = crypto_blkcipher_ctx(desc->tfm);
int bsize = crypto_blkcipher_blocksize(desc->tfm);
int tot_blocks = (nbytes + bsize - 1) / bsize;
int cbc_blocks = tot_blocks > 2 ? tot_blocks - 2 : 0;
struct blkcipher_desc lcldesc;
int err;

lcldesc.tfm = ctx->child;
lcldesc.info = desc->info;
lcldesc.flags = desc->flags;

if (tot_blocks == 1) {
err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src, bsize);
} else if (nbytes <= bsize * 2) {
err = cts_cbc_decrypt(ctx, desc, dst, src, 0, nbytes);
} else {
/* do normal function for tot_blocks - 2 */
err = crypto_blkcipher_decrypt_iv(&lcldesc, dst, src,
cbc_blocks * bsize);
if (err == 0) {
/* do cts for final two blocks */
err = cts_cbc_decrypt(ctx, desc, dst, src,
cbc_blocks * bsize,
nbytes - (cbc_blocks * bsize));
}
}
return err;
}

static int crypto_cts_init_tfm(struct crypto_tfm *tfm)
{
struct crypto_instance *inst = (void *)tfm->__crt_alg;
struct crypto_spawn *spawn = crypto_instance_ctx(inst);
struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
struct crypto_blkcipher *cipher;

cipher = crypto_spawn_blkcipher(spawn);
if (IS_ERR(cipher))
return PTR_ERR(cipher);

ctx->child = cipher;
return 0;
}

static void crypto_cts_exit_tfm(struct crypto_tfm *tfm)
{
struct crypto_cts_ctx *ctx = crypto_tfm_ctx(tfm);
crypto_free_blkcipher(ctx->child);
}

static struct crypto_instance *crypto_cts_alloc(struct rtattr **tb)
{
struct crypto_instance *inst;
struct crypto_alg *alg;
int err;

err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_BLKCIPHER);
if (err)
return ERR_PTR(err);

alg = crypto_attr_alg(tb[1], CRYPTO_ALG_TYPE_BLKCIPHER,
CRYPTO_ALG_TYPE_MASK);
err = PTR_ERR(alg);
if (IS_ERR(alg))
return ERR_PTR(err);

inst = ERR_PTR(-EINVAL);
if (!is_power_of_2(alg->cra_blocksize))
goto out_put_alg;

inst = crypto_alloc_instance("cts", alg);
if (IS_ERR(inst))
goto out_put_alg;

inst->alg.cra_flags = CRYPTO_ALG_TYPE_BLKCIPHER;
inst->alg.cra_priority = alg->cra_priority;
inst->alg.cra_blocksize = alg->cra_blocksize;
inst->alg.cra_alignmask = alg->cra_alignmask;
inst->alg.cra_type = &crypto_blkcipher_type;

/* We access the data as u32s when xoring. */
inst->alg.cra_alignmask |= __alignof__(u32) - 1;

inst->alg.cra_blkcipher.ivsize = alg->cra_blocksize;
inst->alg.cra_blkcipher.min_keysize = alg->cra_blkcipher.min_keysize;
inst->alg.cra_blkcipher.max_keysize = alg->cra_blkcipher.max_keysize;

inst->alg.cra_blkcipher.geniv = "seqiv";

inst->alg.cra_ctxsize = sizeof(struct crypto_cts_ctx);

inst->alg.cra_init = crypto_cts_init_tfm;
inst->alg.cra_exit = crypto_cts_exit_tfm;

inst->alg.cra_blkcipher.setkey = crypto_cts_setkey;
inst->alg.cra_blkcipher.encrypt = crypto_cts_encrypt;
inst->alg.cra_blkcipher.decrypt = crypto_cts_decrypt;

out_put_alg:
crypto_mod_put(alg);
return inst;
}

static void crypto_cts_free(struct crypto_instance *inst)
{
crypto_drop_spawn(crypto_instance_ctx(inst));
kfree(inst);
}

static struct crypto_template crypto_cts_tmpl = {
.name = "cts",
.alloc = crypto_cts_alloc,
.free = crypto_cts_free,
.module = THIS_MODULE,
};

static int __init crypto_cts_module_init(void)
{
return crypto_register_template(&crypto_cts_tmpl);
}

static void __exit crypto_cts_module_exit(void)
{
crypto_unregister_template(&crypto_cts_tmpl);
}

module_init(crypto_cts_module_init);
module_exit(crypto_cts_module_exit);

MODULE_LICENSE("Dual BSD/GPL");
MODULE_DESCRIPTION("CTS-CBC CipherText Stealing for CBC");
Something went wrong with that request. Please try again.