crypto/cipher.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * Cipher operations.
   5  *
   6  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   7  * Copyright (c) 2005 Herbert Xu <herbert@gondor.apana.org.au>
   8  *
   9  * This program is free software; you can redistribute it and/or modify it
  10  * under the terms of the GNU General Public License as published by the Free
  11  * Software Foundation; either version 2 of the License, or (at your option)
  12  * any later version.
  13  *
  14  */
  15 #include <linux/compiler.h>
  16 #include <linux/kernel.h>
  17 #include <linux/crypto.h>
  18 #include <linux/errno.h>
  19 #include <linux/mm.h>
  20 #include <linux/slab.h>
  21 #include <linux/string.h>
  22 #include <asm/scatterlist.h>
  23 #include "internal.h"
  24 #include "scatterwalk.h"
  25
  26 struct cipher_desc {
  27         struct crypto_tfm *tfm;
  28         void (*crfn)(void *ctx, u8 *dst, const u8 *src);
  29         unsigned int (*prfn)(const struct cipher_desc *desc, u8 *dst,
  30                              const u8 *src, unsigned int nbytes);
  31         void *info;
  32 };
  33
  34 static inline void xor_64(u8 *a, const u8 *b)
  35 {
  36         ((u32 *)a)[0] ^= ((u32 *)b)[0];
  37         ((u32 *)a)[1] ^= ((u32 *)b)[1];
  38 }
  39
  40 static inline void xor_128(u8 *a, const u8 *b)
  41 {
  42         ((u32 *)a)[0] ^= ((u32 *)b)[0];
  43         ((u32 *)a)[1] ^= ((u32 *)b)[1];
  44         ((u32 *)a)[2] ^= ((u32 *)b)[2];
  45         ((u32 *)a)[3] ^= ((u32 *)b)[3];
  46 }
  47
  48 static unsigned int crypt_slow(const struct cipher_desc *desc,
  49                                struct scatter_walk *in,
  50                                struct scatter_walk *out, unsigned int bsize)
  51 {
  52         u8 src[bsize];
  53         u8 dst[bsize];
  54         unsigned int n;
  55
  56         n = scatterwalk_copychunks(src, in, bsize, 0);
  57         scatterwalk_advance(in, n);
  58
  59         desc->prfn(desc, dst, src, bsize);
  60
  61         n = scatterwalk_copychunks(dst, out, bsize, 1);
  62         scatterwalk_advance(out, n);
  63
  64         return bsize;
  65 }
  66
  67 static inline unsigned int crypt_fast(const struct cipher_desc *desc,
  68                                       struct scatter_walk *in,
  69                                       struct scatter_walk *out,
  70                                       unsigned int nbytes)
  71 {
  72         u8 *src, *dst;
  73
  74         src = in->data;
  75         dst = scatterwalk_samebuf(in, out) ? src : out->data;
  76
  77         nbytes = desc->prfn(desc, dst, src, nbytes);
  78
  79         scatterwalk_advance(in, nbytes);
  80         scatterwalk_advance(out, nbytes);
  81
  82         return nbytes;
  83 }
  84
  85 /*
  86  * Generic encrypt/decrypt wrapper for ciphers, handles operations across
  87  * multiple page boundaries by using temporary blocks.  In user context,
  88  * the kernel is given a chance to schedule us once per page.
  89  */
  90 static int crypt(const struct cipher_desc *desc,
  91                  struct scatterlist *dst,
  92                  struct scatterlist *src,
  93                  unsigned int nbytes)
  94 {
  95         struct scatter_walk walk_in, walk_out;
  96         struct crypto_tfm *tfm = desc->tfm;
  97         const unsigned int bsize = crypto_tfm_alg_blocksize(tfm);
  98
  99         if (!nbytes)
 100                 return 0;
 101
 102         if (nbytes % bsize) {
 103                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 104                 return -EINVAL;
 105         }
 106
 107         scatterwalk_start(&walk_in, src);
 108         scatterwalk_start(&walk_out, dst);
 109
 110         for(;;) {
 111                 unsigned int n;
 112
 113                 scatterwalk_map(&walk_in, 0);
 114                 scatterwalk_map(&walk_out, 1);
 115
 116                 n = scatterwalk_clamp(&walk_in, nbytes);
 117                 n = scatterwalk_clamp(&walk_out, n);
 118
 119                 if (likely(n >= bsize))
 120                         n = crypt_fast(desc, &walk_in, &walk_out, n);
 121                 else
 122                         n = crypt_slow(desc, &walk_in, &walk_out, bsize);
 123
 124                 nbytes -= n;
 125
 126                 scatterwalk_done(&walk_in, 0, nbytes);
 127                 scatterwalk_done(&walk_out, 1, nbytes);
 128
 129                 if (!nbytes)
 130                         return 0;
 131
 132                 crypto_yield(tfm);
 133         }
 134 }
 135
 136 static unsigned int cbc_process_encrypt(const struct cipher_desc *desc,
 137                                         u8 *dst, const u8 *src,
 138                                         unsigned int nbytes)
 139 {
 140         struct crypto_tfm *tfm = desc->tfm;
 141         void (*xor)(u8 *, const u8 *) = tfm->crt_u.cipher.cit_xor_block;
 142         int bsize = crypto_tfm_alg_blocksize(tfm);
 143
 144         void (*fn)(void *, u8 *, const u8 *) = desc->crfn;
 145         u8 *iv = desc->info;
 146         unsigned int done = 0;
 147
 148         do {
 149                 xor(iv, src);
 150                 fn(crypto_tfm_ctx(tfm), dst, iv);
 151                 memcpy(iv, dst, bsize);
 152
 153                 src += bsize;
 154                 dst += bsize;
 155         } while ((done += bsize) < nbytes);
 156
 157         return done;
 158 }
 159
 160 static unsigned int cbc_process_decrypt(const struct cipher_desc *desc,
 161                                         u8 *dst, const u8 *src,
 162                                         unsigned int nbytes)
 163 {
 164         struct crypto_tfm *tfm = desc->tfm;
 165         void (*xor)(u8 *, const u8 *) = tfm->crt_u.cipher.cit_xor_block;
 166         int bsize = crypto_tfm_alg_blocksize(tfm);
 167
 168         u8 stack[src == dst ? bsize : 0];
 169         u8 *buf = stack;
 170         u8 **dst_p = src == dst ? &buf : &dst;
 171
 172         void (*fn)(void *, u8 *, const u8 *) = desc->crfn;
 173         u8 *iv = desc->info;
 174         unsigned int done = 0;
 175
 176         do {
 177                 u8 *tmp_dst = *dst_p;
 178
 179                 fn(crypto_tfm_ctx(tfm), tmp_dst, src);
 180                 xor(tmp_dst, iv);
 181                 memcpy(iv, src, bsize);
 182                 if (tmp_dst != dst)
 183                         memcpy(dst, tmp_dst, bsize);
 184
 185                 src += bsize;
 186                 dst += bsize;
 187         } while ((done += bsize) < nbytes);
 188
 189         return done;
 190 }
 191
 192 static unsigned int ecb_process(const struct cipher_desc *desc, u8 *dst,
 193                                 const u8 *src, unsigned int nbytes)
 194 {
 195         struct crypto_tfm *tfm = desc->tfm;
 196         int bsize = crypto_tfm_alg_blocksize(tfm);
 197         void (*fn)(void *, u8 *, const u8 *) = desc->crfn;
 198         unsigned int done = 0;
 199
 200         do {
 201                 fn(crypto_tfm_ctx(tfm), dst, src);
 202
 203                 src += bsize;
 204                 dst += bsize;
 205         } while ((done += bsize) < nbytes);
 206
 207         return done;
 208 }
 209
 210 static int setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen)
 211 {
 212         struct cipher_alg *cia = &tfm->__crt_alg->cra_cipher;
 213
 214         if (keylen < cia->cia_min_keysize || keylen > cia->cia_max_keysize) {
 215                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
 216                 return -EINVAL;
 217         } else
 218                 return cia->cia_setkey(crypto_tfm_ctx(tfm), key, keylen,
 219                                        &tfm->crt_flags);
 220 }
 221
 222 static int ecb_encrypt(struct crypto_tfm *tfm,
 223                        struct scatterlist *dst,
 224                        struct scatterlist *src, unsigned int nbytes)
 225 {
 226         struct cipher_desc desc;
 227
 228         desc.tfm = tfm;
 229         desc.crfn = tfm->__crt_alg->cra_cipher.cia_encrypt;
 230         desc.prfn = ecb_process;
 231
 232         return crypt(&desc, dst, src, nbytes);
 233 }
 234
 235 static int ecb_decrypt(struct crypto_tfm *tfm,
 236                        struct scatterlist *dst,
 237                        struct scatterlist *src,
 238                        unsigned int nbytes)
 239 {
 240         struct cipher_desc desc;
 241
 242         desc.tfm = tfm;
 243         desc.crfn = tfm->__crt_alg->cra_cipher.cia_decrypt;
 244         desc.prfn = ecb_process;
 245
 246         return crypt(&desc, dst, src, nbytes);
 247 }
 248
 249 static int cbc_encrypt(struct crypto_tfm *tfm,
 250                        struct scatterlist *dst,
 251                        struct scatterlist *src,
 252                        unsigned int nbytes)
 253 {
 254         struct cipher_desc desc;
 255
 256         desc.tfm = tfm;
 257         desc.crfn = tfm->__crt_alg->cra_cipher.cia_encrypt;
 258         desc.prfn = cbc_process_encrypt;
 259         desc.info = tfm->crt_cipher.cit_iv;
 260
 261         return crypt(&desc, dst, src, nbytes);
 262 }
 263
 264 static int cbc_encrypt_iv(struct crypto_tfm *tfm,
 265                           struct scatterlist *dst,
 266                           struct scatterlist *src,
 267                           unsigned int nbytes, u8 *iv)
 268 {
 269         struct cipher_desc desc;
 270
 271         desc.tfm = tfm;
 272         desc.crfn = tfm->__crt_alg->cra_cipher.cia_encrypt;
 273         desc.prfn = cbc_process_encrypt;
 274         desc.info = iv;
 275
 276         return crypt(&desc, dst, src, nbytes);
 277 }
 278
 279 static int cbc_decrypt(struct crypto_tfm *tfm,
 280                        struct scatterlist *dst,
 281                        struct scatterlist *src,
 282                        unsigned int nbytes)
 283 {
 284         struct cipher_desc desc;
 285
 286         desc.tfm = tfm;
 287         desc.crfn = tfm->__crt_alg->cra_cipher.cia_decrypt;
 288         desc.prfn = cbc_process_decrypt;
 289         desc.info = tfm->crt_cipher.cit_iv;
 290
 291         return crypt(&desc, dst, src, nbytes);
 292 }
 293
 294 static int cbc_decrypt_iv(struct crypto_tfm *tfm,
 295                           struct scatterlist *dst,
 296                           struct scatterlist *src,
 297                           unsigned int nbytes, u8 *iv)
 298 {
 299         struct cipher_desc desc;
 300
 301         desc.tfm = tfm;
 302         desc.crfn = tfm->__crt_alg->cra_cipher.cia_decrypt;
 303         desc.prfn = cbc_process_decrypt;
 304         desc.info = iv;
 305
 306         return crypt(&desc, dst, src, nbytes);
 307 }
 308
 309 static int nocrypt(struct crypto_tfm *tfm,
 310                    struct scatterlist *dst,
 311                    struct scatterlist *src,
 312                    unsigned int nbytes)
 313 {
 314         return -ENOSYS;
 315 }
 316
 317 static int nocrypt_iv(struct crypto_tfm *tfm,
 318                       struct scatterlist *dst,
 319                       struct scatterlist *src,
 320                       unsigned int nbytes, u8 *iv)
 321 {
 322         return -ENOSYS;
 323 }
 324
 325 int crypto_init_cipher_flags(struct crypto_tfm *tfm, u32 flags)
 326 {
 327         u32 mode = flags & CRYPTO_TFM_MODE_MASK;
 328
 329         tfm->crt_cipher.cit_mode = mode ? mode : CRYPTO_TFM_MODE_ECB;
 330         if (flags & CRYPTO_TFM_REQ_WEAK_KEY)
 331                 tfm->crt_flags = CRYPTO_TFM_REQ_WEAK_KEY;
 332
 333         return 0;
 334 }
 335
 336 int crypto_init_cipher_ops(struct crypto_tfm *tfm)
 337 {
 338         int ret = 0;
 339         struct cipher_tfm *ops = &tfm->crt_cipher;
 340
 341         ops->cit_setkey = setkey;
 342
 343         switch (tfm->crt_cipher.cit_mode) {
 344         case CRYPTO_TFM_MODE_ECB:
 345                 ops->cit_encrypt = ecb_encrypt;
 346                 ops->cit_decrypt = ecb_decrypt;
 347                 break;
 348
 349         case CRYPTO_TFM_MODE_CBC:
 350                 ops->cit_encrypt = cbc_encrypt;
 351                 ops->cit_decrypt = cbc_decrypt;
 352                 ops->cit_encrypt_iv = cbc_encrypt_iv;
 353                 ops->cit_decrypt_iv = cbc_decrypt_iv;
 354                 break;
 355
 356         case CRYPTO_TFM_MODE_CFB:
 357                 ops->cit_encrypt = nocrypt;
 358                 ops->cit_decrypt = nocrypt;
 359                 ops->cit_encrypt_iv = nocrypt_iv;
 360                 ops->cit_decrypt_iv = nocrypt_iv;
 361                 break;
 362
 363         case CRYPTO_TFM_MODE_CTR:
 364                 ops->cit_encrypt = nocrypt;
 365                 ops->cit_decrypt = nocrypt;
 366                 ops->cit_encrypt_iv = nocrypt_iv;
 367                 ops->cit_decrypt_iv = nocrypt_iv;
 368                 break;
 369
 370         default:
 371                 BUG();
 372         }
 373
 374         if (ops->cit_mode == CRYPTO_TFM_MODE_CBC) {
 375
 376                 switch (crypto_tfm_alg_blocksize(tfm)) {
 377                 case 8:
 378                         ops->cit_xor_block = xor_64;
 379                         break;
 380
 381                 case 16:
 382                         ops->cit_xor_block = xor_128;
 383                         break;
 384
 385                 default:
 386                         printk(KERN_WARNING "%s: block size %u not supported\n",
 387                                crypto_tfm_alg_name(tfm),
 388                                crypto_tfm_alg_blocksize(tfm));
 389                         ret = -EINVAL;
 390                         goto out;
 391                 }
 392
 393                 ops->cit_ivsize = crypto_tfm_alg_blocksize(tfm);
 394                 ops->cit_iv = kmalloc(ops->cit_ivsize, GFP_KERNEL);
 395                 if (ops->cit_iv == NULL)
 396                         ret = -ENOMEM;
 397         }
 398
 399 out:
 400         return ret;
 401 }
 402
 403 void crypto_exit_cipher_ops(struct crypto_tfm *tfm)
 404 {
 405         kfree(tfm->crt_cipher.cit_iv);
 406 }