AES128 in libgcrypt not encrypting - c++

Question

I've been trying to the libgcrypt for a small cryptography project of mine, but I can't seem to be able to implement the en/decryption correctly. The following the class and the usage of it.
#include <iostream>
#include <string>
#include <cstdlib>
#include <gcrypt.h>
#include "aes.h"
#define GCRY_CIPHER GCRY_CIPHER_AES128
#define GCRY_MODE GCRY_CIPHER_MODE_ECB
using namespace std;
aes::aes(string a) {
key = a;
keyLength = gcry_cipher_get_algo_keylen(GCRY_CIPHER);
gcry_control (GCRYCTL_DISABLE_SECMEM, 0);
gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
gcry_cipher_open(&handle, GCRY_CIPHER, GCRY_MODE, 0);
gcry_cipher_setkey(handle, key.c_str(), keyLength);
}
string aes::encrypt(string text) {
size_t textLength = text.size() + 1;
char * encBuffer = (char *)malloc(textLength);
gcry_cipher_encrypt(handle, encBuffer, textLength, text.c_str(), textLength);
string ret (encBuffer);
return ret;
}
string aes::decrypt(string text) {
size_t textLength = text.size() + 1;
char * decBuffer = (char * )malloc(textLength);
gcry_cipher_decrypt(handle, decBuffer, textLength, text.c_str(), textLength);
string ret (decBuffer);
return ret;
}
And I use it in a main function like so:
...
aes bb = aes("one test AES key");
string test = "Some Message";
string enc = bb.encrypt(test);
string dec = bb.decrypt(enc);
for (size_t index = 0; index<enc.size(); index++)
printf("%c", enc[index]);
printf("\n");
cout << dec << endl;
...
And the output is
BBBBBBBBBBBBB
�n�S[
The odd thing is, I made a test program with almost the exact same statements that works perfectly. It started falling apart when I tried to package it into a class. The following is the code for this program, if anyone wants to see it.
#include <cstdlib>
#include <iostream>
#include <string>
#include <gcrypt.h>
using namespace std;
#define GCRY_CIPHER GCRY_CIPHER_AES128 // Pick the cipher here
#define GCRY_MODE GCRY_CIPHER_MODE_ECB // Pick the cipher mode here
void aesTest(void)
{
gcry_cipher_hd_t handle;
size_t keyLength = gcry_cipher_get_algo_keylen(GCRY_CIPHER);
string txtBuffer ("123456789 abcdefghijklmnopqrstuvwzyz ABCDEFGHIJKLMNOPQRSTUVWZYZ");
size_t txtLength = txtBuffer.size() +1; // string plus termination
char * encBuffer = (char *)malloc(txtLength);
char * outBuffer = (char *)malloc(txtLength);
char * key = "one test AES key"; // 16 bytes
gcry_control (GCRYCTL_DISABLE_SECMEM, 0);
gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
gcry_cipher_open(&handle, GCRY_CIPHER, GCRY_MODE, 0);
gcry_cipher_setkey(handle, key, keyLength);
gcry_cipher_encrypt(handle, encBuffer, txtLength, txtBuffer.c_str(), txtLength);
gcry_cipher_decrypt(handle, outBuffer, txtLength, encBuffer, txtLength);
size_t index;
printf("encBuffer = ");
for (index = 0; index<txtLength; index++)
printf("%c", encBuffer[index]);
printf("\n");
printf("outBuffer = %s\n", outBuffer);
gcry_cipher_close(handle);
free(encBuffer);
free(outBuffer);
}
int main() {
aesTest();
return 0;
}

Answer 1

When you use a std::string to capture the encrypted data, you are possibly losing some data due to the presence of '\0' in the encrypted string.
Try using std::vector<char> instead.
void aes::encrypt(string text, std::vector<char>& ret) {
size_t textLength = text.size() + 1;
ret.resize(textLength);
gcry_cipher_encrypt(handle, ret.data(), textLength, text.c_str(), textLength);
}
string aes::decrypt(std::vector<char> const& text) {
size_t textLength = text.size() + 1;
// Since you are in C++ land, use new and delete
// instead of malloc and free.
char * decBuffer = new char[textLength];
gcry_cipher_decrypt(handle, decBuffer, textLength, text.data(), textLength);
string ret (decBuffer);
delete [] decBuffer;
return ret;
}