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 FILE_LICENCE ( GPL2_OR_LATER );
  20
  21 #include <string.h>
  22 #include <assert.h>
  23 #include <gpxe/crypto.h>
  24 #include <gpxe/cbc.h>
  25
  26 /** @file
  27  *
  28  * Cipher-block chaining
  29  *
  30  */
  31
  32 /**
  33  * XOR data blocks
  34  *
  35  * @v src               Input data
  36  * @v dst               Second input data and output data buffer
  37  * @v len               Length of data
  38  */
  39 static void cbc_xor ( const void *src, void *dst, size_t len ) {
  40         const uint32_t *srcl = src;
  41         uint32_t *dstl = dst;
  42         unsigned int i;
  43
  44         /* Assume that block sizes will always be dword-aligned, for speed */
  45         assert ( ( len % sizeof ( *srcl ) ) == 0 );
  46
  47         for ( i = 0 ; i < ( len / sizeof ( *srcl ) ) ; i++ )
  48                 dstl[i] ^= srcl[i];
  49 }
  50
  51 /**
  52  * Encrypt data
  53  *
  54  * @v ctx               Context
  55  * @v src               Data to encrypt
  56  * @v dst               Buffer for encrypted data
  57  * @v len               Length of data
  58  * @v raw_cipher        Underlying cipher algorithm
  59  * @v cbc_ctx           CBC context
  60  */
  61 void cbc_encrypt ( void *ctx, const void *src, void *dst, size_t len,
  62                    struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
  63         size_t blocksize = raw_cipher->blocksize;
  64
  65         assert ( ( len % blocksize ) == 0 );
  66
  67         while ( len ) {
  68                 cbc_xor ( src, cbc_ctx, blocksize );
  69                 cipher_encrypt ( raw_cipher, ctx, cbc_ctx, dst, blocksize );
  70                 memcpy ( cbc_ctx, dst, blocksize );
  71                 dst += blocksize;
  72                 src += blocksize;
  73                 len -= blocksize;
  74         }
  75 }
  76
  77 /**
  78  * Decrypt data
  79  *
  80  * @v ctx               Context
  81  * @v src               Data to decrypt
  82  * @v dst               Buffer for decrypted data
  83  * @v len               Length of data
  84  * @v raw_cipher        Underlying cipher algorithm
  85  * @v cbc_ctx           CBC context
  86  */
  87 void cbc_decrypt ( void *ctx, const void *src, void *dst, size_t len,
  88                    struct cipher_algorithm *raw_cipher, void *cbc_ctx ) {
  89         size_t blocksize = raw_cipher->blocksize;
  90
  91         assert ( ( len % blocksize ) == 0 );
  92
  93         while ( len ) {
  94                 cipher_decrypt ( raw_cipher, ctx, src, dst, blocksize );
  95                 cbc_xor ( cbc_ctx, dst, blocksize );
  96                 memcpy ( cbc_ctx, src, blocksize );
  97                 dst += blocksize;
  98                 src += blocksize;
  99                 len -= blocksize;
 100         }
 101 }