crypto/cipher.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * Cipher operations.
   5  *
   6  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   7  *
   8  * This program is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the Free
  10  * Software Foundation; either version 2 of the License, or (at your option)
  11  * any later version.
  12  *
  13  */
  14 #include <linux/kernel.h>
  15 #include <linux/crypto.h>
  16 #include <linux/errno.h>
  17 #include <linux/mm.h>
  18 #include <linux/slab.h>
  19 #include <asm/scatterlist.h>
  20 #include "internal.h"
  21 #include "scatterwalk.h"
  22
  23 typedef void (cryptfn_t)(void *, u8 *, const u8 *);
  24 typedef void (procfn_t)(struct crypto_tfm *, u8 *,
  25                         u8*, cryptfn_t, int enc, void *, int);
  26
  27 static inline void xor_64(u8 *a, const u8 *b)
  28 {
  29         ((u32 *)a)[0] ^= ((u32 *)b)[0];
  30         ((u32 *)a)[1] ^= ((u32 *)b)[1];
  31 }
  32
  33 static inline void xor_128(u8 *a, const u8 *b)
  34 {
  35         ((u32 *)a)[0] ^= ((u32 *)b)[0];
  36         ((u32 *)a)[1] ^= ((u32 *)b)[1];
  37         ((u32 *)a)[2] ^= ((u32 *)b)[2];
  38         ((u32 *)a)[3] ^= ((u32 *)b)[3];
  39 }
  40
  41
  42 /*
  43  * Generic encrypt/decrypt wrapper for ciphers, handles operations across
  44  * multiple page boundaries by using temporary blocks.  In user context,
  45  * the kernel is given a chance to schedule us once per block.
  46  */
  47 static int crypt(struct crypto_tfm *tfm,
  48                  struct scatterlist *dst,
  49                  struct scatterlist *src,
  50                  unsigned int nbytes, cryptfn_t crfn,
  51                  procfn_t prfn, int enc, void *info)
  52 {
  53         struct scatter_walk walk_in, walk_out;
  54         const unsigned int bsize = crypto_tfm_alg_blocksize(tfm);
  55         u8 tmp_src[nbytes > src->length ? bsize : 0];
  56         u8 tmp_dst[nbytes > dst->length ? bsize : 0];
  57
  58         if (!nbytes)
  59                 return 0;
  60
  61         if (nbytes % bsize) {
  62                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
  63                 return -EINVAL;
  64         }
  65
  66         scatterwalk_start(&walk_in, src);
  67         scatterwalk_start(&walk_out, dst);
  68
  69         for(;;) {
  70                 u8 *src_p, *dst_p;
  71
  72                 scatterwalk_map(&walk_in, 0);
  73                 scatterwalk_map(&walk_out, 1);
  74                 src_p = scatterwalk_whichbuf(&walk_in, bsize, tmp_src);
  75                 dst_p = scatterwalk_whichbuf(&walk_out, bsize, tmp_dst);
  76
  77                 nbytes -= bsize;
  78
  79                 scatterwalk_copychunks(src_p, &walk_in, bsize, 0);
  80
  81                 prfn(tfm, dst_p, src_p, crfn, enc, info,
  82                      scatterwalk_samebuf(&walk_in, &walk_out,
  83                                          src_p, dst_p));
  84
  85                 scatterwalk_done(&walk_in, 0, nbytes);
  86
  87                 scatterwalk_copychunks(dst_p, &walk_out, bsize, 1);
  88                 scatterwalk_done(&walk_out, 1, nbytes);
  89
  90                 if (!nbytes)
  91                         return 0;
  92
  93                 crypto_yield(tfm);
  94         }
  95 }
  96
  97 static void cbc_process(struct crypto_tfm *tfm, u8 *dst, u8 *src,
  98                         cryptfn_t fn, int enc, void *info, int in_place)
  99 {
 100         u8 *iv = info;
 101
 102         /* Null encryption */
 103         if (!iv)
 104                 return;
 105
 106         if (enc) {
 107                 tfm->crt_u.cipher.cit_xor_block(iv, src);
 108                 fn(crypto_tfm_ctx(tfm), dst, iv);
 109                 memcpy(iv, dst, crypto_tfm_alg_blocksize(tfm));
 110         } else {
 111                 u8 stack[in_place ? crypto_tfm_alg_blocksize(tfm) : 0];
 112                 u8 *buf = in_place ? stack : dst;
 113
 114                 fn(crypto_tfm_ctx(tfm), buf, src);
 115                 tfm->crt_u.cipher.cit_xor_block(buf, iv);
 116                 memcpy(iv, src, crypto_tfm_alg_blocksize(tfm));
 117                 if (buf != dst)
 118                         memcpy(dst, buf, crypto_tfm_alg_blocksize(tfm));
 119         }
 120 }
 121
 122 static void ecb_process(struct crypto_tfm *tfm, u8 *dst, u8 *src,
 123                         cryptfn_t fn, int enc, void *info, int in_place)
 124 {
 125         fn(crypto_tfm_ctx(tfm), dst, src);
 126 }
 127
 128 static int setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen)
 129 {
 130         struct cipher_alg *cia = &tfm->__crt_alg->cra_cipher;
 131
 132         if (keylen < cia->cia_min_keysize || keylen > cia->cia_max_keysize) {
 133                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
 134                 return -EINVAL;
 135         } else
 136                 return cia->cia_setkey(crypto_tfm_ctx(tfm), key, keylen,
 137                                        &tfm->crt_flags);
 138 }
 139
 140 static int ecb_encrypt(struct crypto_tfm *tfm,
 141                        struct scatterlist *dst,
 142                        struct scatterlist *src, unsigned int nbytes)
 143 {
 144         return crypt(tfm, dst, src, nbytes,
 145                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 146                      ecb_process, 1, NULL);
 147 }
 148
 149 static int ecb_decrypt(struct crypto_tfm *tfm,
 150                        struct scatterlist *dst,
 151                        struct scatterlist *src,
 152                        unsigned int nbytes)
 153 {
 154         return crypt(tfm, dst, src, nbytes,
 155                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 156                      ecb_process, 1, NULL);
 157 }
 158
 159 static int cbc_encrypt(struct crypto_tfm *tfm,
 160                        struct scatterlist *dst,
 161                        struct scatterlist *src,
 162                        unsigned int nbytes)
 163 {
 164         return crypt(tfm, dst, src, nbytes,
 165                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 166                      cbc_process, 1, tfm->crt_cipher.cit_iv);
 167 }
 168
 169 static int cbc_encrypt_iv(struct crypto_tfm *tfm,
 170                           struct scatterlist *dst,
 171                           struct scatterlist *src,
 172                           unsigned int nbytes, u8 *iv)
 173 {
 174         return crypt(tfm, dst, src, nbytes,
 175                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 176                      cbc_process, 1, iv);
 177 }
 178
 179 static int cbc_decrypt(struct crypto_tfm *tfm,
 180                        struct scatterlist *dst,
 181                        struct scatterlist *src,
 182                        unsigned int nbytes)
 183 {
 184         return crypt(tfm, dst, src, nbytes,
 185                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 186                      cbc_process, 0, tfm->crt_cipher.cit_iv);
 187 }
 188
 189 static int cbc_decrypt_iv(struct crypto_tfm *tfm,
 190                           struct scatterlist *dst,
 191                           struct scatterlist *src,
 192                           unsigned int nbytes, u8 *iv)
 193 {
 194         return crypt(tfm, dst, src, nbytes,
 195                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 196                      cbc_process, 0, iv);
 197 }
 198
 199 static int nocrypt(struct crypto_tfm *tfm,
 200                    struct scatterlist *dst,
 201                    struct scatterlist *src,
 202                    unsigned int nbytes)
 203 {
 204         return -ENOSYS;
 205 }
 206
 207 static int nocrypt_iv(struct crypto_tfm *tfm,
 208                       struct scatterlist *dst,
 209                       struct scatterlist *src,
 210                       unsigned int nbytes, u8 *iv)
 211 {
 212         return -ENOSYS;
 213 }
 214
 215 int crypto_init_cipher_flags(struct crypto_tfm *tfm, u32 flags)
 216 {
 217         u32 mode = flags & CRYPTO_TFM_MODE_MASK;
 218
 219         tfm->crt_cipher.cit_mode = mode ? mode : CRYPTO_TFM_MODE_ECB;
 220         if (flags & CRYPTO_TFM_REQ_WEAK_KEY)
 221                 tfm->crt_flags = CRYPTO_TFM_REQ_WEAK_KEY;
 222
 223         return 0;
 224 }
 225
 226 int crypto_init_cipher_ops(struct crypto_tfm *tfm)
 227 {
 228         int ret = 0;
 229         struct cipher_tfm *ops = &tfm->crt_cipher;
 230
 231         ops->cit_setkey = setkey;
 232
 233         switch (tfm->crt_cipher.cit_mode) {
 234         case CRYPTO_TFM_MODE_ECB:
 235                 ops->cit_encrypt = ecb_encrypt;
 236                 ops->cit_decrypt = ecb_decrypt;
 237                 break;
 238
 239         case CRYPTO_TFM_MODE_CBC:
 240                 ops->cit_encrypt = cbc_encrypt;
 241                 ops->cit_decrypt = cbc_decrypt;
 242                 ops->cit_encrypt_iv = cbc_encrypt_iv;
 243                 ops->cit_decrypt_iv = cbc_decrypt_iv;
 244                 break;
 245
 246         case CRYPTO_TFM_MODE_CFB:
 247                 ops->cit_encrypt = nocrypt;
 248                 ops->cit_decrypt = nocrypt;
 249                 ops->cit_encrypt_iv = nocrypt_iv;
 250                 ops->cit_decrypt_iv = nocrypt_iv;
 251                 break;
 252
 253         case CRYPTO_TFM_MODE_CTR:
 254                 ops->cit_encrypt = nocrypt;
 255                 ops->cit_decrypt = nocrypt;
 256                 ops->cit_encrypt_iv = nocrypt_iv;
 257                 ops->cit_decrypt_iv = nocrypt_iv;
 258                 break;
 259
 260         default:
 261                 BUG();
 262         }
 263
 264         if (ops->cit_mode == CRYPTO_TFM_MODE_CBC) {
 265
 266                 switch (crypto_tfm_alg_blocksize(tfm)) {
 267                 case 8:
 268                         ops->cit_xor_block = xor_64;
 269                         break;
 270
 271                 case 16:
 272                         ops->cit_xor_block = xor_128;
 273                         break;
 274
 275                 default:
 276                         printk(KERN_WARNING "%s: block size %u not supported\n",
 277                                crypto_tfm_alg_name(tfm),
 278                                crypto_tfm_alg_blocksize(tfm));
 279                         ret = -EINVAL;
 280                         goto out;
 281                 }
 282
 283                 ops->cit_ivsize = crypto_tfm_alg_blocksize(tfm);
 284                 ops->cit_iv = kmalloc(ops->cit_ivsize, GFP_KERNEL);
 285                 if (ops->cit_iv == NULL)
 286                         ret = -ENOMEM;
 287         }
 288
 289 out:
 290         return ret;
 291 }
 292
 293 void crypto_exit_cipher_ops(struct crypto_tfm *tfm)
 294 {
 295         if (tfm->crt_cipher.cit_iv)
 296                 kfree(tfm->crt_cipher.cit_iv);
 297 }