C++ Decrypting Base64 string in ASCII using OpenSSL AES_128_CBC - c++

Question

I have a encrypted string in base64 as ASCII string (std::string) and a key as ASCII string. The iv will just be empty. The key will be variable length and will use padding (and I still don't know how to do this yet). I would like to use OpenSSL AES 128 CBC to decrypt that to the original text. I'm using the source code from the wiki. However the result I got are just random character when I cout or print with %s. Here is the source code:
int main(void)
{
unsigned char* key = (unsigned char*)"okamura";
unsigned char* iv = (unsigned char*)"";
unsigned char* base64 = (unsigned char*)"BPaHjjva7bBjrDQrJyekPA==";
/*
* Buffer for ciphertext. Ensure the buffer is long enough for the
* ciphertext which may be longer than the plaintext, depending on the
* algorithm and mode.
*/
unsigned char ciphertext[128];
/* Buffer for the decrypted text */
unsigned char decryptedtext[128];
int decryptedtext_len, ciphertext_len;
/* Decrypt the ciphertext */
decryptedtext_len = decrypt(base64, sizeof(base64), key, iv,
decryptedtext);
/* Add a NULL terminator. We are expecting printable text */
decryptedtext[decryptedtext_len] = '\0';
/* Show the decrypted text */
printf("Decrypted text is:\n");
printf("%s", decryptedtext);
return 0;
}
Decrypt function
int decrypt(unsigned char* ciphertext, int ciphertext_len, unsigned char* key,
unsigned char* iv, unsigned char* plaintext)
{
EVP_CIPHER_CTX* ctx;
int len;
int plaintext_len;
/* Create and initialise the context */
if (!(ctx = EVP_CIPHER_CTX_new()))
{
}
//handleErrors();
/*
* Initialise the decryption operation. IMPORTANT - ensure you use a key
* and IV size appropriate for your cipher
* In this example we are using 256 bit AES (i.e. a 256 bit key). The
* IV size for *most* modes is the same as the block size. For AES this
* is 128 bits
*/
if (1 != EVP_DecryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
{
}
//handleErrors();
/*
* Provide the message to be decrypted, and obtain the plaintext output.
* EVP_DecryptUpdate can be called multiple times if necessary.
*/
if (1 != EVP_DecryptUpdate(ctx, plaintext, &len, ciphertext, ciphertext_len))
{
}
//handleErrors();
plaintext_len = len;
/*
* Finalise the decryption. Further plaintext bytes may be written at
* this stage.
*/
if (1 != EVP_DecryptFinal_ex(ctx, plaintext + len, &len))
{
}
//handleErrors();
plaintext_len += len;
/* Clean up */
EVP_CIPHER_CTX_free(ctx);
return plaintext_len;
}
Encrypt function
int encrypt(unsigned char* plaintext, int plaintext_len, unsigned char* key,
unsigned char* iv, unsigned char* ciphertext)
{
EVP_CIPHER_CTX* ctx;
int len;
int ciphertext_len;
/* Create and initialise the context */
if (!(ctx = EVP_CIPHER_CTX_new()))
handleErrors();
/*
* Initialise the encryption operation. IMPORTANT - ensure you use a key
* and IV size appropriate for your cipher
* In this example we are using 256 bit AES (i.e. a 256 bit key). The
* IV size for *most* modes is the same as the block size. For AES this
* is 128 bits
*/
if (1 != EVP_EncryptInit_ex(ctx, EVP_aes_128_cbc(), NULL, key, iv))
handleErrors();
/*
* Provide the message to be encrypted, and obtain the encrypted output.
* EVP_EncryptUpdate can be called multiple times if necessary
*/
if (1 != EVP_EncryptUpdate(ctx, ciphertext, &len, plaintext, plaintext_len))
handleErrors();
ciphertext_len = len;
/*
* Finalise the encryption. Further ciphertext bytes may be written at
* this stage.
*/
if (1 != EVP_EncryptFinal_ex(ctx, ciphertext + len, &len))
handleErrors();
ciphertext_len += len;
/* Clean up */
EVP_CIPHER_CTX_free(ctx);
return ciphertext_len;
}