crypto/cipher.c

   1 /*
   2  * Cryptographic API.
   3  *
   4  * Cipher operations.
   5  *
   6  * Copyright (c) 2002 James Morris <jmorris@intercode.com.au>
   7  * Generic scatterwalk code by Adam J. Richter <adam@yggdrasil.com>.
   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/kernel.h>
  16 #include <linux/crypto.h>
  17 #include <linux/errno.h>
  18 #include <linux/mm.h>
  19 #include <linux/slab.h>
  20 #include <linux/pagemap.h>
  21 #include <linux/highmem.h>
  22 #include <asm/scatterlist.h>
  23 #include "internal.h"
  24
  25 typedef void (cryptfn_t)(void *, u8 *, const u8 *);
  26 typedef void (procfn_t)(struct crypto_tfm *, u8 *,
  27                         u8*, cryptfn_t, int enc, void *);
  28
  29 struct scatter_walk {
  30         struct scatterlist      *sg;
  31         struct page             *page;
  32         void                    *data;
  33         unsigned int            len_this_page;
  34         unsigned int            len_this_segment;
  35         unsigned int            offset;
  36 };
  37
  38 enum km_type crypto_km_types[] = {
  39         KM_USER0,
  40         KM_USER1,
  41         KM_SOFTIRQ0,
  42         KM_SOFTIRQ1,
  43 };
  44
  45 static inline void xor_64(u8 *a, const u8 *b)
  46 {
  47         ((u32 *)a)[0] ^= ((u32 *)b)[0];
  48         ((u32 *)a)[1] ^= ((u32 *)b)[1];
  49 }
  50
  51 static inline void xor_128(u8 *a, const u8 *b)
  52 {
  53         ((u32 *)a)[0] ^= ((u32 *)b)[0];
  54         ((u32 *)a)[1] ^= ((u32 *)b)[1];
  55         ((u32 *)a)[2] ^= ((u32 *)b)[2];
  56         ((u32 *)a)[3] ^= ((u32 *)b)[3];
  57 }
  58
  59
  60 /* Define sg_next is an inline routine now in case we want to change
  61    scatterlist to a linked list later. */
  62 static inline struct scatterlist *sg_next(struct scatterlist *sg)
  63 {
  64         return sg + 1;
  65 }
  66
  67 void *which_buf(struct scatter_walk *walk, unsigned int nbytes, void *scratch)
  68 {
  69         if (nbytes <= walk->len_this_page &&
  70             (((unsigned long)walk->data) & (PAGE_CACHE_SIZE - 1)) + nbytes <=
  71             PAGE_CACHE_SIZE)
  72                 return walk->data;
  73         else
  74                 return scratch;
  75 }
  76
  77 static void memcpy_dir(void *buf, void *sgdata, size_t nbytes, int out)
  78 {
  79         if (out)
  80                 memcpy(sgdata, buf, nbytes);
  81         else
  82                 memcpy(buf, sgdata, nbytes);
  83 }
  84
  85 static void scatterwalk_start(struct scatter_walk *walk, struct scatterlist *sg)
  86 {
  87         unsigned int rest_of_page;
  88
  89         walk->sg = sg;
  90
  91         walk->page = sg->page;
  92         walk->len_this_segment = sg->length;
  93
  94         rest_of_page = PAGE_CACHE_SIZE - (sg->offset & (PAGE_CACHE_SIZE - 1));
  95         walk->len_this_page = min(sg->length, rest_of_page);
  96         walk->offset = sg->offset;
  97 }
  98
  99 static void scatterwalk_map(struct scatter_walk *walk, int out)
 100 {
 101         walk->data = crypto_kmap(walk->page, out) + walk->offset;
 102 }
 103
 104 static void scatter_page_done(struct scatter_walk *walk, int out,
 105                               unsigned int more)
 106 {
 107         /* walk->data may be pointing the first byte of the next page;
 108            however, we know we transfered at least one byte.  So,
 109            walk->data - 1 will be a virutual address in the mapped page. */
 110
 111         if (out)
 112                 flush_dcache_page(walk->page);
 113
 114         if (more) {
 115                 walk->len_this_segment -= walk->len_this_page;
 116
 117                 if (walk->len_this_segment) {
 118                         walk->page++;
 119                         walk->len_this_page = min(walk->len_this_segment,
 120                                                   (unsigned)PAGE_CACHE_SIZE);
 121                         walk->offset = 0;
 122                 }
 123                 else
 124                         scatterwalk_start(walk, sg_next(walk->sg));
 125         }
 126 }
 127
 128 static void scatter_done(struct scatter_walk *walk, int out, int more)
 129 {
 130         crypto_kunmap(walk->data, out);
 131         if (walk->len_this_page == 0 || !more)
 132                 scatter_page_done(walk, out, more);
 133 }
 134
 135 /*
 136  * Do not call this unless the total length of all of the fragments
 137  * has been verified as multiple of the block size.
 138  */
 139 static int copy_chunks(void *buf, struct scatter_walk *walk,
 140                         size_t nbytes, int out)
 141 {
 142         if (buf != walk->data) {
 143                 while (nbytes > walk->len_this_page) {
 144                         memcpy_dir(buf, walk->data, walk->len_this_page, out);
 145                         buf += walk->len_this_page;
 146                         nbytes -= walk->len_this_page;
 147
 148                         crypto_kunmap(walk->data, out);
 149                         scatter_page_done(walk, out, 1);
 150                         scatterwalk_map(walk, out);
 151                 }
 152
 153                 memcpy_dir(buf, walk->data, nbytes, out);
 154         }
 155
 156         walk->offset += nbytes;
 157         walk->len_this_page -= nbytes;
 158         walk->len_this_segment -= nbytes;
 159         return 0;
 160 }
 161
 162 /*
 163  * Generic encrypt/decrypt wrapper for ciphers, handles operations across
 164  * multiple page boundaries by using temporary blocks.  In user context,
 165  * the kernel is given a chance to schedule us once per block.
 166  */
 167 static int crypt(struct crypto_tfm *tfm,
 168                  struct scatterlist *dst,
 169                  struct scatterlist *src,
 170                  unsigned int nbytes, cryptfn_t crfn,
 171                  procfn_t prfn, int enc, void *info)
 172 {
 173         struct scatter_walk walk_in, walk_out;
 174         const unsigned int bsize = crypto_tfm_alg_blocksize(tfm);
 175         u8 tmp_src[nbytes > src->length ? bsize : 0];
 176         u8 tmp_dst[nbytes > dst->length ? bsize : 0];
 177
 178         if (!nbytes)
 179                 return 0;
 180
 181         if (nbytes % bsize) {
 182                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_BLOCK_LEN;
 183                 return -EINVAL;
 184         }
 185
 186         scatterwalk_start(&walk_in, src);
 187         scatterwalk_start(&walk_out, dst);
 188
 189         for(;;) {
 190                 u8 *src_p, *dst_p;
 191
 192                 scatterwalk_map(&walk_in, 0);
 193                 scatterwalk_map(&walk_out, 1);
 194                 src_p = which_buf(&walk_in, bsize, tmp_src);
 195                 dst_p = which_buf(&walk_out, bsize, tmp_dst);
 196
 197                 nbytes -= bsize;
 198
 199                 copy_chunks(src_p, &walk_in, bsize, 0);
 200
 201                 prfn(tfm, dst_p, src_p, crfn, enc, info);
 202
 203                 scatter_done(&walk_in, 0, nbytes);
 204
 205                 copy_chunks(dst_p, &walk_out, bsize, 1);
 206                 scatter_done(&walk_out, 1, nbytes);
 207
 208                 if (!nbytes)
 209                         return 0;
 210
 211                 crypto_yield(tfm);
 212         }
 213 }
 214
 215 static void cbc_process(struct crypto_tfm *tfm,
 216                         u8 *dst, u8 *src, cryptfn_t fn, int enc, void *info)
 217 {
 218         u8 *iv = info;
 219
 220         /* Null encryption */
 221         if (!iv)
 222                 return;
 223
 224         if (enc) {
 225                 tfm->crt_u.cipher.cit_xor_block(iv, src);
 226                 fn(crypto_tfm_ctx(tfm), dst, iv);
 227                 memcpy(iv, dst, crypto_tfm_alg_blocksize(tfm));
 228         } else {
 229                 const int need_stack = (src == dst);
 230                 u8 stack[need_stack ? crypto_tfm_alg_blocksize(tfm) : 0];
 231                 u8 *buf = need_stack ? stack : dst;
 232
 233                 fn(crypto_tfm_ctx(tfm), buf, src);
 234                 tfm->crt_u.cipher.cit_xor_block(buf, iv);
 235                 memcpy(iv, src, crypto_tfm_alg_blocksize(tfm));
 236                 if (buf != dst)
 237                         memcpy(dst, buf, crypto_tfm_alg_blocksize(tfm));
 238         }
 239 }
 240
 241 static void ecb_process(struct crypto_tfm *tfm, u8 *dst, u8 *src,
 242                         cryptfn_t fn, int enc, void *info)
 243 {
 244         fn(crypto_tfm_ctx(tfm), dst, src);
 245 }
 246
 247 static int setkey(struct crypto_tfm *tfm, const u8 *key, unsigned int keylen)
 248 {
 249         struct cipher_alg *cia = &tfm->__crt_alg->cra_cipher;
 250
 251         if (keylen < cia->cia_min_keysize || keylen > cia->cia_max_keysize) {
 252                 tfm->crt_flags |= CRYPTO_TFM_RES_BAD_KEY_LEN;
 253                 return -EINVAL;
 254         } else
 255                 return cia->cia_setkey(crypto_tfm_ctx(tfm), key, keylen,
 256                                        &tfm->crt_flags);
 257 }
 258
 259 static int ecb_encrypt(struct crypto_tfm *tfm,
 260                        struct scatterlist *dst,
 261                        struct scatterlist *src, unsigned int nbytes)
 262 {
 263         return crypt(tfm, dst, src, nbytes,
 264                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 265                      ecb_process, 1, NULL);
 266 }
 267
 268 static int ecb_decrypt(struct crypto_tfm *tfm,
 269                        struct scatterlist *dst,
 270                        struct scatterlist *src,
 271                        unsigned int nbytes)
 272 {
 273         return crypt(tfm, dst, src, nbytes,
 274                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 275                      ecb_process, 1, NULL);
 276 }
 277
 278 static int cbc_encrypt(struct crypto_tfm *tfm,
 279                        struct scatterlist *dst,
 280                        struct scatterlist *src,
 281                        unsigned int nbytes)
 282 {
 283         return crypt(tfm, dst, src, nbytes,
 284                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 285                      cbc_process, 1, tfm->crt_cipher.cit_iv);
 286 }
 287
 288 static int cbc_encrypt_iv(struct crypto_tfm *tfm,
 289                           struct scatterlist *dst,
 290                           struct scatterlist *src,
 291                           unsigned int nbytes, u8 *iv)
 292 {
 293         return crypt(tfm, dst, src, nbytes,
 294                      tfm->__crt_alg->cra_cipher.cia_encrypt,
 295                      cbc_process, 1, iv);
 296 }
 297
 298 static int cbc_decrypt(struct crypto_tfm *tfm,
 299                        struct scatterlist *dst,
 300                        struct scatterlist *src,
 301                        unsigned int nbytes)
 302 {
 303         return crypt(tfm, dst, src, nbytes,
 304                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 305                      cbc_process, 0, tfm->crt_cipher.cit_iv);
 306 }
 307
 308 static int cbc_decrypt_iv(struct crypto_tfm *tfm,
 309                           struct scatterlist *dst,
 310                           struct scatterlist *src,
 311                           unsigned int nbytes, u8 *iv)
 312 {
 313         return crypt(tfm, dst, src, nbytes,
 314                      tfm->__crt_alg->cra_cipher.cia_decrypt,
 315                      cbc_process, 0, iv);
 316 }
 317
 318 static int nocrypt(struct crypto_tfm *tfm,
 319                    struct scatterlist *dst,
 320                    struct scatterlist *src,
 321                    unsigned int nbytes)
 322 {
 323         return -ENOSYS;
 324 }
 325
 326 static int nocrypt_iv(struct crypto_tfm *tfm,
 327                       struct scatterlist *dst,
 328                       struct scatterlist *src,
 329                       unsigned int nbytes, u8 *iv)
 330 {
 331         return -ENOSYS;
 332 }
 333
 334 int crypto_init_cipher_flags(struct crypto_tfm *tfm, u32 flags)
 335 {
 336         u32 mode = flags & CRYPTO_TFM_MODE_MASK;
 337
 338         tfm->crt_cipher.cit_mode = mode ? mode : CRYPTO_TFM_MODE_ECB;
 339         if (flags & CRYPTO_TFM_REQ_WEAK_KEY)
 340                 tfm->crt_flags = CRYPTO_TFM_REQ_WEAK_KEY;
 341
 342         return 0;
 343 }
 344
 345 int crypto_init_cipher_ops(struct crypto_tfm *tfm)
 346 {
 347         int ret = 0;
 348         struct cipher_tfm *ops = &tfm->crt_cipher;
 349
 350         ops->cit_setkey = setkey;
 351
 352         switch (tfm->crt_cipher.cit_mode) {
 353         case CRYPTO_TFM_MODE_ECB:
 354                 ops->cit_encrypt = ecb_encrypt;
 355                 ops->cit_decrypt = ecb_decrypt;
 356                 break;
 357
 358         case CRYPTO_TFM_MODE_CBC:
 359                 ops->cit_encrypt = cbc_encrypt;
 360                 ops->cit_decrypt = cbc_decrypt;
 361                 ops->cit_encrypt_iv = cbc_encrypt_iv;
 362                 ops->cit_decrypt_iv = cbc_decrypt_iv;
 363                 break;
 364
 365         case CRYPTO_TFM_MODE_CFB:
 366                 ops->cit_encrypt = nocrypt;
 367                 ops->cit_decrypt = nocrypt;
 368                 ops->cit_encrypt_iv = nocrypt_iv;
 369                 ops->cit_decrypt_iv = nocrypt_iv;
 370                 break;
 371
 372         case CRYPTO_TFM_MODE_CTR:
 373                 ops->cit_encrypt = nocrypt;
 374                 ops->cit_decrypt = nocrypt;
 375                 ops->cit_encrypt_iv = nocrypt_iv;
 376                 ops->cit_decrypt_iv = nocrypt_iv;
 377                 break;
 378
 379         default:
 380                 BUG();
 381         }
 382
 383         if (ops->cit_mode == CRYPTO_TFM_MODE_CBC) {
 384
 385                 switch (crypto_tfm_alg_blocksize(tfm)) {
 386                 case 8:
 387                         ops->cit_xor_block = xor_64;
 388                         break;
 389
 390                 case 16:
 391                         ops->cit_xor_block = xor_128;
 392                         break;
 393
 394                 default:
 395                         printk(KERN_WARNING "%s: block size %u not supported\n",
 396                                crypto_tfm_alg_name(tfm),
 397                                crypto_tfm_alg_blocksize(tfm));
 398                         ret = -EINVAL;
 399                         goto out;
 400                 }
 401
 402                 ops->cit_ivsize = crypto_tfm_alg_blocksize(tfm);
 403                 ops->cit_iv = kmalloc(ops->cit_ivsize, GFP_KERNEL);
 404                 if (ops->cit_iv == NULL)
 405                         ret = -ENOMEM;
 406         }
 407
 408 out:
 409         return ret;
 410 }
 411
 412 void crypto_exit_cipher_ops(struct crypto_tfm *tfm)
 413 {
 414         if (tfm->crt_cipher.cit_iv)
 415                 kfree(tfm->crt_cipher.cit_iv);
 416 }