src/crypto/cbc.c

   1 /*
   2  * Copyright (C) 2009 Michael Brown <mbrown@fensystems.co.uk>.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License as
   6  * published by the Free Software Foundation; either version 2 of the
   7  * License, or any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17  */
  18
  19 #include <string.h>
  20 #include <assert.h>
  21 #include <gpxe/crypto.h>
  22 #include <gpxe/cbc.h>
  23
  24 /** @file
  25  *
  26  * Cipher-block chaining
  27  *
  28  */
  29
  30 /**
  31  * XOR data blocks
  32  *
  33  * @v src               Input data
  34  * @v dst               Second input data and output data buffer
  35  * @v len               Length of data
  36  */
  37 static void cbc_xor ( const void *src, void *dst, size_t len ) {
  38         const uint32_t *srcl = src;
  39         uint32_t *dstl = dst;
  40         unsigned int i;
  41
  42         /* Assume that block sizes will always be dword-aligned, for speed */
  43         assert ( ( len % sizeof ( *srcl ) ) == 0 );
  44
  45         for ( i = 0 ; i < ( len / sizeof ( *srcl ) ) ; i++ )
  46                 dstl[i] ^= srcl[i];
  47 }
  48
  49 /**
  50  * Encrypt data
  51  *
  52  * @v ctx               Context
  53  * @v src               Data to encrypt
  54  * @v dst               Buffer for encrypted data
  55  * @v len               Length of data
  56  * @v raw_cipher        Underlying cipher algorithm
  57  * @v cbc_ctx           CBC context
  58  */
  59 void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
  60                    struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
  61         size_t blocksize = raw_cipher->blocksize;
  62
  63         assert ( ( len % blocksize ) == 0 );
  64
  65         while ( len ) {
  66                 cbc_xor ( src, cbc_ctx, blocksize );
  67                 cipher_encrypt ( raw_cipher, ctx, cbc_ctx, dst, blocksize );
  68                 memcpy ( cbc_ctx, dst, blocksize );
  69                 dst += blocksize;
  70                 src += blocksize;
  71                 len -= blocksize;
  72         }
  73 }
  74
  75 /**
  76  * Decrypt data
  77  *
  78  * @v ctx               Context
  79  * @v src               Data to decrypt
  80  * @v dst               Buffer for decrypted data
  81  * @v len               Length of data
  82  * @v raw_cipher        Underlying cipher algorithm
  83  * @v cbc_ctx           CBC context
  84  */
  85 void cbc_decrypt ( void *ctx, const void *src, void *dst, size_t len,
  86                    struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
  87         size_t blocksize = raw_cipher->blocksize;
  88
  89         assert ( ( len % blocksize ) == 0 );
  90
  91         while ( len ) {
  92                 cipher_decrypt ( raw_cipher, ctx, src, dst, blocksize );
  93                 cbc_xor ( cbc_ctx, dst, blocksize );
  94                 memcpy ( cbc_ctx, src, blocksize );
  95                 dst += blocksize;
  96                 src += blocksize;
  97                 len -= blocksize;
  98         }
  99 }