crypto_aes_128_cbc.c

00001 /*
00002 MiniTLS - A super trimmed down TLS/SSL Library for embedded devices
00003 Author: Donatien Garnier
00004 Copyright (C) 2013-2014 AppNearMe Ltd
00005 
00006 This program is free software; you can redistribute it and/or
00007 modify it under the terms of the GNU General Public License
00008 as published by the Free Software Foundation; either version 2
00009 of the License, or (at your option) any later version.
00010 
00011 This program is distributed in the hope that it will be useful,
00012 but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 GNU General Public License for more details.
00015 
00016 You should have received a copy of the GNU General Public License
00017 along with this program; if not, write to the Free Software
00018 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
00019 *//**
00020  * \file crypto_aes_128_cbc.c
00021  * \copyright Copyright (c) AppNearMe Ltd 2013
00022  * \author Donatien Garnier
00023  */
00024 
00025 #define __DEBUG__ 0
00026 #ifndef __MODULE__
00027 #define __MODULE__ "crypto_aes_128_cbc.c"
00028 #endif
00029 
00030 
00031 #include "core/fwk.h"
00032 #include "inc/minitls_errors.h"
00033 
00034 #include "crypto_aes_128_cbc.h"
00035 
00036 minitls_err_t crypto_aes_128_cbc_encrypt(crypto_aes_128_t* cipher, buffer_t* initialization_vector, buffer_t* buffer)
00037 {
00038   uint8_t* text = buffer_current_read_position(buffer);
00039   size_t size = buffer_length(buffer);
00040 
00041   uint8_t* previous = buffer_current_read_position(initialization_vector);
00042 
00043   if( (size % AES_128_BLOCK_SIZE) || (buffer_length(initialization_vector) != AES_128_BLOCK_SIZE) )
00044   {
00045     return MINITLS_ERR_WRONG_ALIGNMENT_FOR_CIPHER;
00046   }
00047 
00048   uint8_t xored_input[AES_128_BLOCK_SIZE]; //Xored input
00049 
00050   while(size > 0)
00051   {
00052     for(int i = 0; i < AES_128_BLOCK_SIZE / sizeof(uint32_t); i++)
00053     {
00054       ((uint32_t*)xored_input)[i] = ((uint32_t*)previous)[i] ^ ((uint32_t*)text)[i];
00055     }
00056 
00057     crypto_aes_128_encrypt(cipher, xored_input, text);
00058 
00059     previous = text; //Save previous ciphertext to use as initialization vector
00060 
00061     text += AES_128_BLOCK_SIZE;
00062     size -= AES_128_BLOCK_SIZE;
00063   }
00064 
00065   return MINITLS_OK;
00066 }
00067 
00068 minitls_err_t crypto_aes_128_cbc_decrypt(crypto_aes_128_t* cipher, buffer_t* initialization_vector, buffer_t* buffer)
00069 {
00070   uint8_t* text = buffer_current_read_position(buffer);
00071   size_t size = buffer_length(buffer);
00072 
00073   if( (size % AES_128_BLOCK_SIZE) || (buffer_length(initialization_vector) != AES_128_BLOCK_SIZE) )
00074   {
00075     return MINITLS_ERR_WRONG_ALIGNMENT_FOR_CIPHER;
00076   }
00077 
00078   uint8_t xored_output[AES_128_BLOCK_SIZE]; //Xored input
00079   uint8_t previous[AES_128_BLOCK_SIZE*2];
00080 
00081   memcpy(previous, buffer_current_read_position(initialization_vector), AES_128_BLOCK_SIZE);
00082 
00083   while(size > 0)
00084   {
00085     //Save cipher text (to use as initialization vector)
00086     memcpy(previous + AES_128_BLOCK_SIZE, text, AES_128_BLOCK_SIZE);
00087 
00088     crypto_aes_128_decrypt(cipher, text, xored_output);
00089 
00090     for(int i = 0; i < AES_128_BLOCK_SIZE / sizeof(uint32_t); i++)
00091     {
00092       ((uint32_t*)text)[i] = ((uint32_t*)previous)[i] ^ ((uint32_t*)xored_output)[i];
00093     }
00094 
00095     memmove(previous, previous + AES_128_BLOCK_SIZE, AES_128_BLOCK_SIZE);
00096 
00097     text += AES_128_BLOCK_SIZE;
00098     size -= AES_128_BLOCK_SIZE;
00099   }
00100 
00101   return MINITLS_OK;
00102 }
00103