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   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");