hex2bin issue

[Phantom139]

Hello, I have a faulty hex2bin function here, and I'm wondering if anyone has suggestions to fix it.

std::string hex2Bin(std::string &input) {
	std::ostringstream output;
	int len = input.length();
	char tmp[5], *ptr;
	tmp[0] = '0';
	tmp[1] = 'x';
	tmp[4] = '\0';
	for (int i = 0; i < len; i += 2) {
		if (i + 1 >= len)
			return output.str();
		tmp[2] = input[i];
		tmp[3] = input[i+1];
		//std::cout << tmp << "\n";
		output << (char)strtol(tmp, &ptr, 16);
	}
	return output.str();
}

Here are two sample generated outputs over this hex:

Hex: 96d013fa9cfe343952a952b671ada6867116948912726c890a732864198a1c3a861e994854796dce89da9a6d6e7f4b6220a8491d37ff113616c9a7812b0deb2d

The php script I have is returning the correct value

PHP: Ç_Èo<ë…9§q?bì=O—"d�ð%sM0²ÑøäÈÁ"ü»¸½¹&èÏø÷_œÌ2P¨¹PM‹(¯¡¢Ç[ToÊiÊ]æÍ\è!
Ú<V‚ø+?¬ñu!ܨÔX'Ø*‡ÒUE¨^&´àgùmOŸë[¯ôÉ¢ô 󃩼ÏQ

C++: Ç_Èo<ë…9§q?bì=O—"d ð%sM0²ÑøäÈÁ"ü»¸½¹&èÏø÷_œÌ2P¨¹PM‹(¯¡¢Ç[ToÊiÊ]æÍ\è!
Ú<V‚ø+?¬ñu!ܨÔX'Ø*‡ÒUE¨^&´àgùmOŸë[¯ôÉ¢ô
󃩼ÏQ

Any help would be great, Thanks.

[PanGalactic]

What character set is that supposed to be? The output looks like garbage to me.

[Phantom139]

not sure how much PHP you know, but I'm using the Hex2Bin function for OpenSSL's RSA functioning, more specifically RSA_Verify which requests a binary form of the signature.

This is the PHP version of the hex2bin function that I have, and what is generating the correct output

   function hex2bin($data) {
      $len = strlen($data);
      for($i=0;$i<$len;$i+=2) {
         $newdata .= pack("C",hexdec(substr($data,$i,2)));
      }
      return $newdata;
   }

[Phantom139]

Ok, got a better description from another website. I'm dealing with x509 certificates, and during the verification process of the certificate's signature for openSSL, the hexadecimal signature needs to be converted to a byte array, that's what the hex2bin function does.

[Phantom139]

I have another update, maybe it can be solvable this time. It appears that the issue lies in the way that the string is stored when it hits an 0x00/0x20 case. apparently the 0x00 is being treated as a white space 0x20, as well as the 0x20, when I need it to come out as the pure ASCII form, which has it in some weird looking vertical rectangle, which is throwing off the binary signature. I want to try to avoid using a Replace on 0x20 to 0x00 because if the case does come along where 0x20 is valid, it would invalidate it.

So, my question apparently has now switched to how can I keep 0x00 in my string using the above code, or would it just be better to try to use a "table" swap method IE:

const char * table[256] = {"0x00", "0x01" .... "0xff"};

If anyone knows, that would be great, I do however need to keep the data in either std::string, const char *, or unsigned char * format, or be able to convert to it keeping the 0x00 intact.