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                 int in_place;
  72
  73                 scatterwalk_map(&walk_in, 0);
  74                 scatterwalk_map(&walk_out, 1);
  75                 src_p = scatterwalk_whichbuf(&walk_in, bsize, tmp_src);
  76                 dst_p = scatterwalk_whichbuf(&walk_out, bsize, tmp_dst);
  77                 in_place = scatterwalk_samebuf(&walk_in, &walk_out,
  78                                                src_p, dst_p);
  79
  80                 nbytes -= bsize;
  81
  82                 scatterwalk_copychunks(src_p, &walk_in, bsize, 0);
  83
  84                 prfn(tfm, dst_p, src_p, crfn, enc, info, in_place);
  85
  86                 scatterwalk_done(&walk_in, 0, nbytes);
  87
  88                 scatterwalk_copychunks(dst_p, &walk_out, bsize, 1);
  89                 scatterwalk_done(&walk_out, 1, nbytes);
  90
  91                 if (!nbytes)
  92                         return 0;
  93
  94                 crypto_yield(tfm);
  95         }
  96 }
  97
  98 static void cbc_process(struct crypto_tfm *tfm, u8 *dst, u8 *src,
  99                         cryptfn_t fn, int enc, void *info, int in_place)
 100 {
 101         u8 *iv = info;
 102
 103         /* Null encryption */
 104         if (!iv)
 105                 return;
 106
 107         if (enc) {
 108                 tfm->crt_u.cipher.cit_xor_block(iv, src);
 109                 fn(crypto_tfm_ctx(tfm), dst, iv);
 110                 memcpy(iv, dst, crypto_tfm_alg_blocksize(tfm));
 111         } else {
 112                 u8 stack[in_place ? crypto_tfm_alg_blocksize(tfm) : 0];
 113                 u8 *buf = in_place ? stack : dst;
 114
 115                 fn(crypto_tfm_ctx(tfm), buf, src);
 116                 tfm->crt_u.cipher.cit_xor_block(buf, iv);
 117                 memcpy(iv, src, crypto_tfm_alg_blocksize(tfm));
 118                 if (buf != dst)
 119                         memcpy(dst, buf, crypto_tfm_alg_blocksize(tfm));
 120         }
 121 }
 122
 123 static void ecb_process(struct crypto_tfm *tfm, u8 *dst, u8 *src,
 124                         cryptfn_t fn, int enc, void *info, int in_place)
 125 {
 126         fn(crypto_tfm_ctx(tfm), dst, src);
 127 }
 128
 129 static int setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen)
 130 {
 131         struct cipher_alg *cia = &tfm->__crt_alg->cra_cipher;
 132
 133         if (keylen < cia->cia_min_keysize || keylen > cia->cia_max_keysize) {
 134                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
 135                 return -EINVAL;
 136         } else
 137                 return cia->cia_setkey(crypto_tfm_ctx(tfm), key, keylen,
 138                                        &tfm->crt_flags);
 139 }
 140
 141 static int ecb_encrypt(struct crypto_tfm *tfm,
 142                        struct scatterlist *dst,
 143                        struct scatterlist *src, unsigned int nbytes)
 144 {
 145         return crypt(tfm, dst, src, nbytes,
 146                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 147                      ecb_process, 1, NULL);
 148 }
 149
 150 static int ecb_decrypt(struct crypto_tfm *tfm,
 151                        struct scatterlist *dst,
 152                        struct scatterlist *src,
 153                        unsigned int nbytes)
 154 {
 155         return crypt(tfm, dst, src, nbytes,
 156                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 157                      ecb_process, 1, NULL);
 158 }
 159
 160 static int cbc_encrypt(struct crypto_tfm *tfm,
 161                        struct scatterlist *dst,
 162                        struct scatterlist *src,
 163                        unsigned int nbytes)
 164 {
 165         return crypt(tfm, dst, src, nbytes,
 166                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 167                      cbc_process, 1, tfm->crt_cipher.cit_iv);
 168 }
 169
 170 static int cbc_encrypt_iv(struct crypto_tfm *tfm,
 171                           struct scatterlist *dst,
 172                           struct scatterlist *src,
 173                           unsigned int nbytes, u8 *iv)
 174 {
 175         return crypt(tfm, dst, src, nbytes,
 176                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 177                      cbc_process, 1, iv);
 178 }
 179
 180 static int cbc_decrypt(struct crypto_tfm *tfm,
 181                        struct scatterlist *dst,
 182                        struct scatterlist *src,
 183                        unsigned int nbytes)
 184 {
 185         return crypt(tfm, dst, src, nbytes,
 186                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 187                      cbc_process, 0, tfm->crt_cipher.cit_iv);
 188 }
 189
 190 static int cbc_decrypt_iv(struct crypto_tfm *tfm,
 191                           struct scatterlist *dst,
 192                           struct scatterlist *src,
 193                           unsigned int nbytes, u8 *iv)
 194 {
 195         return crypt(tfm, dst, src, nbytes,
 196                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 197                      cbc_process, 0, iv);
 198 }
 199
 200 static int nocrypt(struct crypto_tfm *tfm,
 201                    struct scatterlist *dst,
 202                    struct scatterlist *src,
 203                    unsigned int nbytes)
 204 {
 205         return -ENOSYS;
 206 }
 207
 208 static int nocrypt_iv(struct crypto_tfm *tfm,
 209                       struct scatterlist *dst,
 210                       struct scatterlist *src,
 211                       unsigned int nbytes, u8 *iv)
 212 {
 213         return -ENOSYS;
 214 }
 215
 216 int crypto_init_cipher_flags(struct crypto_tfm *tfm, u32 flags)
 217 {
 218         u32 mode = flags & CRYPTO_TFM_MODE_MASK;
 219
 220         tfm->crt_cipher.cit_mode = mode ? mode : CRYPTO_TFM_MODE_ECB;
 221         if (flags & CRYPTO_TFM_REQ_WEAK_KEY)
 222                 tfm->crt_flags = CRYPTO_TFM_REQ_WEAK_KEY;
 223
 224         return 0;
 225 }
 226
 227 int crypto_init_cipher_ops(struct crypto_tfm *tfm)
 228 {
 229         int ret = 0;
 230         struct cipher_tfm *ops = &tfm->crt_cipher;
 231
 232         ops->cit_setkey = setkey;
 233
 234         switch (tfm->crt_cipher.cit_mode) {
 235         case CRYPTO_TFM_MODE_ECB:
 236                 ops->cit_encrypt = ecb_encrypt;
 237                 ops->cit_decrypt = ecb_decrypt;
 238                 break;
 239
 240         case CRYPTO_TFM_MODE_CBC:
 241                 ops->cit_encrypt = cbc_encrypt;
 242                 ops->cit_decrypt = cbc_decrypt;
 243                 ops->cit_encrypt_iv = cbc_encrypt_iv;
 244                 ops->cit_decrypt_iv = cbc_decrypt_iv;
 245                 break;
 246
 247         case CRYPTO_TFM_MODE_CFB:
 248                 ops->cit_encrypt = nocrypt;
 249                 ops->cit_decrypt = nocrypt;
 250                 ops->cit_encrypt_iv = nocrypt_iv;
 251                 ops->cit_decrypt_iv = nocrypt_iv;
 252                 break;
 253
 254         case CRYPTO_TFM_MODE_CTR:
 255                 ops->cit_encrypt = nocrypt;
 256                 ops->cit_decrypt = nocrypt;
 257                 ops->cit_encrypt_iv = nocrypt_iv;
 258                 ops->cit_decrypt_iv = nocrypt_iv;
 259                 break;
 260
 261         default:
 262                 BUG();
 263         }
 264
 265         if (ops->cit_mode == CRYPTO_TFM_MODE_CBC) {
 266
 267                 switch (crypto_tfm_alg_blocksize(tfm)) {
 268                 case 8:
 269                         ops->cit_xor_block = xor_64;
 270                         break;
 271
 272                 case 16:
 273                         ops->cit_xor_block = xor_128;
 274                         break;
 275
 276                 default:
 277                         printk(KERN_WARNING "%s: block size %u not supported\n",
 278                                crypto_tfm_alg_name(tfm),
 279                                crypto_tfm_alg_blocksize(tfm));
 280                         ret = -EINVAL;
 281                         goto out;
 282                 }
 283
 284                 ops->cit_ivsize = crypto_tfm_alg_blocksize(tfm);
 285                 ops->cit_iv = kmalloc(ops->cit_ivsize, GFP_KERNEL);
 286                 if (ops->cit_iv == NULL)
 287                         ret = -ENOMEM;
 288         }
 289
 290 out:
 291         return ret;
 292 }
 293
 294 void crypto_exit_cipher_ops(struct crypto_tfm *tfm)
 295 {
 296         if (tfm->crt_cipher.cit_iv)
 297                 kfree(tfm->crt_cipher.cit_iv);
 298 }