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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
static const unsigned char base64_encode[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
static const unsigned char hex_encode[] =
"0123456789abcdef";
/*
* This functions accepts a string and returns it base64 encoded
*/
void three_bytes_to_base64(char * encode, int bytes_to_print, char *result)
{
unsigned char one, two, three, four;
unsigned char tmp;
char ret[4];
// first six bits
one = encode[0] >> 2;
ret[0] = base64_encode[one];
if(bytes_to_print-- > 0)
result[0] = ret[0];
// second six bits
// two last bits of first byte
tmp = encode[0] & 0x03;
two = encode[1] >> 4;
tmp = tmp << 4;
two = tmp | two;
ret[1] = base64_encode[two];
if(bytes_to_print-- > 0)
result[1] = ret[1];
// second six bits
// two last bits of first byte
// third six bits
tmp = encode[1] & 0x0F;
tmp = tmp << 2;
three = encode[2] & 0xC0;
three = three >> 6;
three = tmp | three;
ret[2] = base64_encode[three];
if(bytes_to_print-- > 0)
result[2] = ret[2];
// last six bit11s
four = encode[2] & 0x3F;
ret[3] = base64_encode[four];
ret[4] = '\0';
if(bytes_to_print-- > 0)
result[3] = ret[3];
}
static char string_to_hex_map[] = {0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
0x07, 0x08, 0x09, 0x0A, 0x0B, 0x0C, 0x0D,
0x0E, 0x0F};
/*
* This function converts the first char of a string into its corresponding
* hex value
*
* @return On Sucess return 0, if char is no valid hex value returns -1
*/
int hex_char_to_bit(char toEncode)
{
char encode;
switch(toEncode) {
case '0':
encode = string_to_hex_map[0];
break;
case '1':
encode = string_to_hex_map[1];
break;
case '2':
encode = string_to_hex_map[2];
break;
case '3':
encode = string_to_hex_map[3];
break;
case '4':
encode = string_to_hex_map[4];
break;
case '5':
encode = string_to_hex_map[5];
break;
case '6':
encode = string_to_hex_map[6];
break;
case '7':
encode = string_to_hex_map[7];
break;
case '8':
encode = string_to_hex_map[8];
break;
case '9':
encode = string_to_hex_map[9];
break;
case 'a':
encode = string_to_hex_map[10];
break;
case 'b':
encode = string_to_hex_map[11];
break;
case 'c':
encode = string_to_hex_map[12];
break;
case 'd':
encode = string_to_hex_map[13];
break;
case 'e':
encode = string_to_hex_map[14];
break;
case 'f':
encode = string_to_hex_map[15];
break;
default:
return -1;
}
return encode;
}
void two_char_hex(char *start, char *result)
{
char first = hex_char_to_bit(start[0]);
char second = hex_char_to_bit(start[1]);
*result = first;
*result = *result << 4;
*result = *result | second;
}
int convert_hex_string_to_binary(char *encode, char* result)
{
int i;
int length = strlen(encode);
for(i = 0;i< length/2;i++)
two_char_hex(&encode[i*2], &result[i]);
return i;
}
int convert_to_base64(char *encode, char *result)
{
int length = strlen(encode);
int rounds = length / 3;
int bytes_last_round = length % 3;
int i;
for (i=0;i<rounds;i++) {
three_bytes_to_base64(encode + i*3,4, &result[i*4]);
}
// in der letzen runde nicht mehr alle ausgeben
// nur noch 3-leftover
if (bytes_last_round > 0) {
three_bytes_to_base64(encode + i*3, 1+bytes_last_round, &result[i*4]);
for(i=0;i<(3-bytes_last_round);i++)
result[i*4+(1+bytes_last_round)] = '=';
}
}
void xor_string(char *str1, char* str2, char *result, int length) {
int i;
for(i=0;i<length;i++)
result[i] = str1[i] ^ str2[i];
return;
}
/**
* results must be to times bigger than str1
*/
void hex_binary_to_string(char *str1, char *result, int length)
{
int i;
int tmp = 0;
for(i=0;i<length/2;i++) {
tmp = str1[i] & 0xF0;
tmp = tmp >> 4;
result[i*2] = hex_encode[tmp];
tmp = str1[i] & 0x0F;
result[(i*2)+1] = hex_encode[tmp];
}
result[i*2] = '\0';
}
int main(int argc, char **argv)
{
if (argc == 3 ) {
int length = strlen(argv[1]);
char *tmp = malloc(length);
char *tmp2 = malloc(length);
char *base64= malloc(length);
char *__xor_string = malloc(length);
char *back_hex = malloc(length);
int i = convert_hex_string_to_binary(argv[1], tmp);
int j = convert_hex_string_to_binary(argv[2], tmp2);
xor_string(tmp, tmp2, __xor_string, strlen(argv[2]));
// convert the __xor_string to printable charaters
hex_binary_to_string(tmp2, back_hex, strlen(argv[2]));
printf("input string 1:\n");
printf("%s\n", argv[1]);
printf("input string 2:\n");
printf("%s\n", argv[2]);
/*
printf("char string of arg 1:\n");
printf("%s\n", tmp);
printf("char string of arg 2:\n");
printf("%s\n", tmp2);
*/
printf("string 2 from hex back to printable charaters:\n");
printf("%s\n", back_hex);
printf("xor string:\n");
hex_binary_to_string(__xor_string, back_hex, strlen(argv[2]));
printf("%s\n", back_hex);
}
}
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