crypto/ctr.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * CTR: Counter mode
   4  *
   5  * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
   6  */
   7
   8 #include <crypto/algapi.h>
   9 #include <crypto/ctr.h>
  10 #include <crypto/internal/cipher.h>
  11 #include <crypto/internal/skcipher.h>
  12 #include <linux/err.h>
  13 #include <linux/init.h>
  14 #include <linux/kernel.h>
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17
  18 struct crypto_rfc3686_ctx {
  19         struct crypto_skcipher *child;
  20         u8 nonce[CTR_RFC3686_NONCE_SIZE];
  21 };
  22
  23 struct crypto_rfc3686_req_ctx {
  24         u8 iv[CTR_RFC3686_BLOCK_SIZE];
  25         struct skcipher_request subreq CRYPTO_MINALIGN_ATTR;
  26 };
  27
  28 static void crypto_ctr_crypt_final(struct skcipher_walk *walk,
  29                                    struct crypto_cipher *tfm)
  30 {
  31         unsigned int bsize = crypto_cipher_blocksize(tfm);
  32         unsigned long alignmask = crypto_cipher_alignmask(tfm);
  33         u8 *ctrblk = walk->iv;
  34         u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
  35         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
  36         u8 *src = walk->src.virt.addr;
  37         u8 *dst = walk->dst.virt.addr;
  38         unsigned int nbytes = walk->nbytes;
  39
  40         crypto_cipher_encrypt_one(tfm, keystream, ctrblk);
  41         crypto_xor_cpy(dst, keystream, src, nbytes);
  42
  43         crypto_inc(ctrblk, bsize);
  44 }
  45
  46 static int crypto_ctr_crypt_segment(struct skcipher_walk *walk,
  47                                     struct crypto_cipher *tfm)
  48 {
  49         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  50                    crypto_cipher_alg(tfm)->cia_encrypt;
  51         unsigned int bsize = crypto_cipher_blocksize(tfm);
  52         u8 *ctrblk = walk->iv;
  53         u8 *src = walk->src.virt.addr;
  54         u8 *dst = walk->dst.virt.addr;
  55         unsigned int nbytes = walk->nbytes;
  56
  57         do {
  58                 /* create keystream */
  59                 fn(crypto_cipher_tfm(tfm), dst, ctrblk);
  60                 crypto_xor(dst, src, bsize);
  61
  62                 /* increment counter in counterblock */
  63                 crypto_inc(ctrblk, bsize);
  64
  65                 src += bsize;
  66                 dst += bsize;
  67         } while ((nbytes -= bsize) >= bsize);
  68
  69         return nbytes;
  70 }
  71
  72 static int crypto_ctr_crypt_inplace(struct skcipher_walk *walk,
  73                                     struct crypto_cipher *tfm)
  74 {
  75         void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
  76                    crypto_cipher_alg(tfm)->cia_encrypt;
  77         unsigned int bsize = crypto_cipher_blocksize(tfm);
  78         unsigned long alignmask = crypto_cipher_alignmask(tfm);
  79         unsigned int nbytes = walk->nbytes;
  80         u8 *ctrblk = walk->iv;
  81         u8 *src = walk->src.virt.addr;
  82         u8 tmp[MAX_CIPHER_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
  83         u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
  84
  85         do {
  86                 /* create keystream */
  87                 fn(crypto_cipher_tfm(tfm), keystream, ctrblk);
  88                 crypto_xor(src, keystream, bsize);
  89
  90                 /* increment counter in counterblock */
  91                 crypto_inc(ctrblk, bsize);
  92
  93                 src += bsize;
  94         } while ((nbytes -= bsize) >= bsize);
  95
  96         return nbytes;
  97 }
  98
  99 static int crypto_ctr_crypt(struct skcipher_request *req)
 100 {
 101         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 102         struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
 103         const unsigned int bsize = crypto_cipher_blocksize(cipher);
 104         struct skcipher_walk walk;
 105         unsigned int nbytes;
 106         int err;
 107
 108         err = skcipher_walk_virt(&walk, req, false);
 109
 110         while (walk.nbytes >= bsize) {
 111                 if (walk.src.virt.addr == walk.dst.virt.addr)
 112                         nbytes = crypto_ctr_crypt_inplace(&walk, cipher);
 113                 else
 114                         nbytes = crypto_ctr_crypt_segment(&walk, cipher);
 115
 116                 err = skcipher_walk_done(&walk, nbytes);
 117         }
 118
 119         if (walk.nbytes) {
 120                 crypto_ctr_crypt_final(&walk, cipher);
 121                 err = skcipher_walk_done(&walk, 0);
 122         }
 123
 124         return err;
 125 }
 126
 127 static int crypto_ctr_create(struct crypto_template *tmpl, struct rtattr **tb)
 128 {
 129         struct skcipher_instance *inst;
 130         struct crypto_alg *alg;
 131         int err;
 132
 133         inst = skcipher_alloc_instance_simple(tmpl, tb);
 134         if (IS_ERR(inst))
 135                 return PTR_ERR(inst);
 136
 137         alg = skcipher_ialg_simple(inst);
 138
 139         /* Block size must be >= 4 bytes. */
 140         err = -EINVAL;
 141         if (alg->cra_blocksize < 4)
 142                 goto out_free_inst;
 143
 144         /* If this is false we'd fail the alignment of crypto_inc. */
 145         if (alg->cra_blocksize % 4)
 146                 goto out_free_inst;
 147
 148         /* CTR mode is a stream cipher. */
 149         inst->alg.base.cra_blocksize = 1;
 150
 151         /*
 152          * To simplify the implementation, configure the skcipher walk to only
 153          * give a partial block at the very end, never earlier.
 154          */
 155         inst->alg.chunksize = alg->cra_blocksize;
 156
 157         inst->alg.encrypt = crypto_ctr_crypt;
 158         inst->alg.decrypt = crypto_ctr_crypt;
 159
 160         err = skcipher_register_instance(tmpl, inst);
 161         if (err) {
 162 out_free_inst:
 163                 inst->free(inst);
 164         }
 165
 166         return err;
 167 }
 168
 169 static int crypto_rfc3686_setkey(struct crypto_skcipher *parent,
 170                                  const u8 *key, unsigned int keylen)
 171 {
 172         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(parent);
 173         struct crypto_skcipher *child = ctx->child;
 174
 175         /* the nonce is stored in bytes at end of key */
 176         if (keylen < CTR_RFC3686_NONCE_SIZE)
 177                 return -EINVAL;
 178
 179         memcpy(ctx->nonce, key + (keylen - CTR_RFC3686_NONCE_SIZE),
 180                CTR_RFC3686_NONCE_SIZE);
 181
 182         keylen -= CTR_RFC3686_NONCE_SIZE;
 183
 184         crypto_skcipher_clear_flags(child, CRYPTO_TFM_REQ_MASK);
 185         crypto_skcipher_set_flags(child, crypto_skcipher_get_flags(parent) &
 186                                          CRYPTO_TFM_REQ_MASK);
 187         return crypto_skcipher_setkey(child, key, keylen);
 188 }
 189
 190 static int crypto_rfc3686_crypt(struct skcipher_request *req)
 191 {
 192         struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
 193         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 194         struct crypto_skcipher *child = ctx->child;
 195         unsigned long align = crypto_skcipher_alignmask(tfm);
 196         struct crypto_rfc3686_req_ctx *rctx =
 197                 (void *)PTR_ALIGN((u8 *)skcipher_request_ctx(req), align + 1);
 198         struct skcipher_request *subreq = &rctx->subreq;
 199         u8 *iv = rctx->iv;
 200
 201         /* set up counter block */
 202         memcpy(iv, ctx->nonce, CTR_RFC3686_NONCE_SIZE);
 203         memcpy(iv + CTR_RFC3686_NONCE_SIZE, req->iv, CTR_RFC3686_IV_SIZE);
 204
 205         /* initialize counter portion of counter block */
 206         *(__be32 *)(iv + CTR_RFC3686_NONCE_SIZE + CTR_RFC3686_IV_SIZE) =
 207                 cpu_to_be32(1);
 208
 209         skcipher_request_set_tfm(subreq, child);
 210         skcipher_request_set_callback(subreq, req->base.flags,
 211                                       req->base.complete, req->base.data);
 212         skcipher_request_set_crypt(subreq, req->src, req->dst,
 213                                    req->cryptlen, iv);
 214
 215         return crypto_skcipher_encrypt(subreq);
 216 }
 217
 218 static int crypto_rfc3686_init_tfm(struct crypto_skcipher *tfm)
 219 {
 220         struct skcipher_instance *inst = skcipher_alg_instance(tfm);
 221         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 222         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 223         struct crypto_skcipher *cipher;
 224         unsigned long align;
 225         unsigned int reqsize;
 226
 227         cipher = crypto_spawn_skcipher(spawn);
 228         if (IS_ERR(cipher))
 229                 return PTR_ERR(cipher);
 230
 231         ctx->child = cipher;
 232
 233         align = crypto_skcipher_alignmask(tfm);
 234         align &= ~(crypto_tfm_ctx_alignment() - 1);
 235         reqsize = align + sizeof(struct crypto_rfc3686_req_ctx) +
 236                   crypto_skcipher_reqsize(cipher);
 237         crypto_skcipher_set_reqsize(tfm, reqsize);
 238
 239         return 0;
 240 }
 241
 242 static void crypto_rfc3686_exit_tfm(struct crypto_skcipher *tfm)
 243 {
 244         struct crypto_rfc3686_ctx *ctx = crypto_skcipher_ctx(tfm);
 245
 246         crypto_free_skcipher(ctx->child);
 247 }
 248
 249 static void crypto_rfc3686_free(struct skcipher_instance *inst)
 250 {
 251         struct crypto_skcipher_spawn *spawn = skcipher_instance_ctx(inst);
 252
 253         crypto_drop_skcipher(spawn);
 254         kfree(inst);
 255 }
 256
 257 static int crypto_rfc3686_create(struct crypto_template *tmpl,
 258                                  struct rtattr **tb)
 259 {
 260         struct skcipher_instance *inst;
 261         struct skcipher_alg *alg;
 262         struct crypto_skcipher_spawn *spawn;
 263         u32 mask;
 264         int err;
 265
 266         err = crypto_check_attr_type(tb, CRYPTO_ALG_TYPE_SKCIPHER, &mask);
 267         if (err)
 268                 return err;
 269
 270         inst = kzalloc(sizeof(*inst) + sizeof(*spawn), GFP_KERNEL);
 271         if (!inst)
 272                 return -ENOMEM;
 273
 274         spawn = skcipher_instance_ctx(inst);
 275
 276         err = crypto_grab_skcipher(spawn, skcipher_crypto_instance(inst),
 277                                    crypto_attr_alg_name(tb[1]), 0, mask);
 278         if (err)
 279                 goto err_free_inst;
 280
 281         alg = crypto_spawn_skcipher_alg(spawn);
 282
 283         /* We only support 16-byte blocks. */
 284         err = -EINVAL;
 285         if (crypto_skcipher_alg_ivsize(alg) != CTR_RFC3686_BLOCK_SIZE)
 286                 goto err_free_inst;
 287
 288         /* Not a stream cipher? */
 289         if (alg->base.cra_blocksize != 1)
 290                 goto err_free_inst;
 291
 292         err = -ENAMETOOLONG;
 293         if (snprintf(inst->alg.base.cra_name, CRYPTO_MAX_ALG_NAME,
 294                      "rfc3686(%s)", alg->base.cra_name) >= CRYPTO_MAX_ALG_NAME)
 295                 goto err_free_inst;
 296         if (snprintf(inst->alg.base.cra_driver_name, CRYPTO_MAX_ALG_NAME,
 297                      "rfc3686(%s)", alg->base.cra_driver_name) >=
 298             CRYPTO_MAX_ALG_NAME)
 299                 goto err_free_inst;
 300
 301         inst->alg.base.cra_priority = alg->base.cra_priority;
 302         inst->alg.base.cra_blocksize = 1;
 303         inst->alg.base.cra_alignmask = alg->base.cra_alignmask;
 304
 305         inst->alg.ivsize = CTR_RFC3686_IV_SIZE;
 306         inst->alg.chunksize = crypto_skcipher_alg_chunksize(alg);
 307         inst->alg.min_keysize = crypto_skcipher_alg_min_keysize(alg) +
 308                                 CTR_RFC3686_NONCE_SIZE;
 309         inst->alg.max_keysize = crypto_skcipher_alg_max_keysize(alg) +
 310                                 CTR_RFC3686_NONCE_SIZE;
 311
 312         inst->alg.setkey = crypto_rfc3686_setkey;
 313         inst->alg.encrypt = crypto_rfc3686_crypt;
 314         inst->alg.decrypt = crypto_rfc3686_crypt;
 315
 316         inst->alg.base.cra_ctxsize = sizeof(struct crypto_rfc3686_ctx);
 317
 318         inst->alg.init = crypto_rfc3686_init_tfm;
 319         inst->alg.exit = crypto_rfc3686_exit_tfm;
 320
 321         inst->free = crypto_rfc3686_free;
 322
 323         err = skcipher_register_instance(tmpl, inst);
 324         if (err) {
 325 err_free_inst:
 326                 crypto_rfc3686_free(inst);
 327         }
 328         return err;
 329 }
 330
 331 static struct crypto_template crypto_ctr_tmpls[] = {
 332         {
 333                 .name = "ctr",
 334                 .create = crypto_ctr_create,
 335                 .module = THIS_MODULE,
 336         }, {
 337                 .name = "rfc3686",
 338                 .create = crypto_rfc3686_create,
 339                 .module = THIS_MODULE,
 340         },
 341 };
 342
 343 static int __init crypto_ctr_module_init(void)
 344 {
 345         return crypto_register_templates(crypto_ctr_tmpls,
 346                                          ARRAY_SIZE(crypto_ctr_tmpls));
 347 }
 348
 349 static void __exit crypto_ctr_module_exit(void)
 350 {
 351         crypto_unregister_templates(crypto_ctr_tmpls,
 352                                     ARRAY_SIZE(crypto_ctr_tmpls));
 353 }
 354
 355 subsys_initcall(crypto_ctr_module_init);
 356 module_exit(crypto_ctr_module_exit);
 357
 358 MODULE_LICENSE("GPL");
 359 MODULE_DESCRIPTION("CTR block cipher mode of operation");
 360 MODULE_ALIAS_CRYPTO("rfc3686");
 361 MODULE_ALIAS_CRYPTO("ctr");
 362 MODULE_IMPORT_NS(CRYPTO_INTERNAL);