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