FreeBSD/Linux Kernel Cross Reference
sys/opencrypto/xform_aes_xts.c

     /*      $OpenBSD: xform.c,v 1.16 2001/08/28 12:20:43 ben Exp $  */
     /*-
      * The authors of this code are John Ioannidis (ji@tla.org),
      * Angelos D. Keromytis (kermit@csd.uch.gr),
      * Niels Provos (provos@physnet.uni-hamburg.de) and
      * Damien Miller (djm@mindrot.org).
      *
      * This code was written by John Ioannidis for BSD/OS in Athens, Greece,
      * in November 1995.
     *
     * Ported to OpenBSD and NetBSD, with additional transforms, in December 1996,
     * by Angelos D. Keromytis.
     *
     * Additional transforms and features in 1997 and 1998 by Angelos D. Keromytis
     * and Niels Provos.
     *
     * Additional features in 1999 by Angelos D. Keromytis.
     *
     * AES XTS implementation in 2008 by Damien Miller
     *
     * Copyright (C) 1995, 1996, 1997, 1998, 1999 by John Ioannidis,
     * Angelos D. Keromytis and Niels Provos.
     *
     * Copyright (C) 2001, Angelos D. Keromytis.
     *
     * Copyright (C) 2008, Damien Miller
     * Copyright (c) 2014 The FreeBSD Foundation
     * All rights reserved.
     *
     * Portions of this software were developed by John-Mark Gurney
     * under sponsorship of the FreeBSD Foundation and
     * Rubicon Communications, LLC (Netgate).
     *
     * Permission to use, copy, and modify this software with or without fee
     * is hereby granted, provided that this entire notice is included in
     * all copies of any software which is or includes a copy or
     * modification of this software.
     * You may use this code under the GNU public license if you so wish. Please
     * contribute changes back to the authors under this freer than GPL license
     * so that we may further the use of strong encryption without limitations to
     * all.
     *
     * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR
     * IMPLIED WARRANTY. IN PARTICULAR, NONE OF THE AUTHORS MAKES ANY
     * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE
     * MERCHANTABILITY OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR
     * PURPOSE.
     */
    
    #include <sys/cdefs.h>
    __FBSDID("$FreeBSD$");
    
    #include <sys/types.h>
    #include <opencrypto/xform_enc.h>
    
    static  int aes_xts_setkey(void *, const uint8_t *, int);
    static  void aes_xts_encrypt(void *, const uint8_t *, uint8_t *);
    static  void aes_xts_decrypt(void *, const uint8_t *, uint8_t *);
    static  void aes_xts_reinit(void *, const uint8_t *);
    
    /* Encryption instances */
    struct enc_xform enc_xform_aes_xts = {
            .type = CRYPTO_AES_XTS,
            .name = "AES-XTS",
            .ctxsize = sizeof(struct aes_xts_ctx),
            .blocksize = AES_BLOCK_LEN,
            .ivsize = AES_XTS_IV_LEN,
            .minkey = AES_XTS_MIN_KEY,
            .maxkey = AES_XTS_MAX_KEY,
            .encrypt = aes_xts_encrypt,
            .decrypt = aes_xts_decrypt,
            .setkey = aes_xts_setkey,
            .reinit = aes_xts_reinit
    };
    
    /*
     * Encryption wrapper routines.
     */
    static void
    aes_xts_reinit(void *key, const uint8_t *iv)
    {
            struct aes_xts_ctx *ctx = key;
            uint64_t blocknum;
            u_int i;
    
            /*
             * Prepare tweak as E_k2(IV). IV is specified as LE representation
             * of a 64-bit block number which we allow to be passed in directly.
             */
            bcopy(iv, &blocknum, AES_XTS_IVSIZE);
            for (i = 0; i < AES_XTS_IVSIZE; i++) {
                    ctx->tweak[i] = blocknum & 0xff;
                    blocknum >>= 8;
            }
            /* Last 64 bits of IV are always zero */
            bzero(ctx->tweak + AES_XTS_IVSIZE, AES_XTS_IVSIZE);
    
            rijndael_encrypt(&ctx->key2, ctx->tweak, ctx->tweak);
    }
   
   static void
   aes_xts_crypt(struct aes_xts_ctx *ctx, const uint8_t *in, uint8_t *out,
       u_int do_encrypt)
   {
           uint8_t block[AES_XTS_BLOCKSIZE];
           u_int i, carry_in, carry_out;
   
           for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
                   block[i] = in[i] ^ ctx->tweak[i];
   
           if (do_encrypt)
                   rijndael_encrypt(&ctx->key1, block, out);
           else
                   rijndael_decrypt(&ctx->key1, block, out);
   
           for (i = 0; i < AES_XTS_BLOCKSIZE; i++)
                   out[i] ^= ctx->tweak[i];
   
           /* Exponentiate tweak */
           carry_in = 0;
           for (i = 0; i < AES_XTS_BLOCKSIZE; i++) {
                   carry_out = ctx->tweak[i] & 0x80;
                   ctx->tweak[i] = (ctx->tweak[i] << 1) | (carry_in ? 1 : 0);
                   carry_in = carry_out;
           }
           if (carry_in)
                   ctx->tweak[0] ^= AES_XTS_ALPHA;
           explicit_bzero(block, sizeof(block));
   }
   
   static void
   aes_xts_encrypt(void *key, const uint8_t *in, uint8_t *out)
   {
           aes_xts_crypt(key, in, out, 1);
   }
   
   static void
   aes_xts_decrypt(void *key, const uint8_t *in, uint8_t *out)
   {
           aes_xts_crypt(key, in, out, 0);
   }
   
   static int
   aes_xts_setkey(void *sched, const uint8_t *key, int len)
   {
           struct aes_xts_ctx *ctx;
   
           if (len != 32 && len != 64)
                   return (EINVAL);
   
           ctx = sched;
   
           rijndael_set_key(&ctx->key1, key, len * 4);
           rijndael_set_key(&ctx->key2, key + (len / 2), len * 4);
   
           return (0);
   }

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