bad decrypt Error OpenSSL C++ & QT AES 256 CBC - c++

Question

I'm trying to add plaintext encryption/decryption (AES 256 CBC) functionality to a personal project built using QT and C++. I'm using OpenSSL v1.1.1. I followed few guides and build a class to handle encryption and decryption. Encryption seems to work fine. But decryption function sometimes throws error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt
This works:
sample text here....
These does not ( . = newline ):
i.
sample text here...
.
.
.
.
.
ii.
sample text here... sample text here...
I'm new to QT, C++ and OpenSSL so I have no idea how to fix this.
My Class:
#define KEYSIZE 32
#define IVSIZE 32
#define BLOCKSIZE 256
#define SALTSIZE 8
QByteArray Encryptor::randBytes(int size) {
unsigned char array[size];
RAND_bytes(array, size);
QByteArray output = QByteArray(reinterpret_cast<char*> (array), size);
return output;
}
QByteArray Encryptor::encrypt(QByteArray passphrase, QByteArray &content) {
QByteArray msalt = randBytes(SALTSIZE);
int rounds = 1;
unsigned char key[KEYSIZE];
unsigned char iv[IVSIZE];
const unsigned char *password = (const unsigned char*) passphrase.constData();
const unsigned char *salt = (const unsigned char*) msalt.constData();
int i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt, password, passphrase.length(), rounds, key, iv);
if (i != KEYSIZE) {
qCritical() << "EVP_BytesToKey() -- " << ERR_error_string(ERR_get_error(), NULL);
return QByteArray();
}
EVP_CIPHER_CTX *en = EVP_CIPHER_CTX_new();
EVP_CIPHER_CTX_init(en);
if (!EVP_EncryptInit_ex(en, EVP_aes_256_cbc(), NULL, key, iv)) {
qCritical() << "EVP_EncryptInit_ex() -- " << ERR_error_string(ERR_get_error(), NULL);
return QByteArray();
}
char *input = content.data();
char *out;
int length = content.size();
int cLength = length + AES_BLOCK_SIZE;
int fLength = 0;
unsigned char *cipherText = (unsigned char*) malloc(cLength);
if (!EVP_EncryptInit_ex(en, NULL, NULL, NULL, NULL)) {
qCritical() << "EVP_EncryptInit_ex() -- " << ERR_error_string(ERR_get_error(), NULL);
return QByteArray();
}
if (!EVP_EncryptUpdate(en, cipherText, &cLength, (unsigned char*) input, length)) {
qCritical() << "EVP_EncryptUpdate() -- " << ERR_error_string(ERR_get_error(), NULL);
free(cipherText);
return QByteArray();
}
if (!EVP_EncryptFinal(en, cipherText + cLength, &fLength)) {
qCritical() << "EVP_EncryptFinal() -- " << ERR_error_string(ERR_get_error(), NULL);
free(cipherText);
return QByteArray();
}
length = cLength + fLength;
out = (char*) cipherText;
EVP_CIPHER_CTX_cipher(en);
free(cipherText);
QByteArray output;
output.append("Salted__");
output.append(msalt);
output.append(out, length);
return output;
}
QByteArray Encryptor::decrypt(QByteArray passphrase, QByteArray &content) {
QByteArray msalt;
if (QString(content.mid(0, 8)) != "Salted__") {
qCritical() << "can not extrect the salt...";
return QByteArray();
}
msalt = content.mid(8, 8);
content = content.mid(16);
int rounds = 1;
unsigned char key[KEYSIZE];
unsigned char iv[IVSIZE];
const unsigned char *password = (const unsigned char*) passphrase.constData();
const unsigned char *salt = (const unsigned char*) msalt.constData();
int i = EVP_BytesToKey(EVP_aes_256_cbc(), EVP_sha1(), salt, password, passphrase.length(), rounds, key, iv);
if (i != KEYSIZE) {
qCritical() << "EVP_BytesToKey() -- " << ERR_error_string(ERR_get_error(), NULL);
return QByteArray();
}
EVP_CIPHER_CTX *de = EVP_CIPHER_CTX_new();
EVP_CIPHER_CTX_init(de);
if (!EVP_DecryptInit_ex(de, EVP_aes_256_cbc(), NULL, key, iv)) {
qCritical() << "EVP_DecryptInit_ex() -- " << ERR_error_string(ERR_get_error(), NULL);
return QByteArray();
}
char *input = content.data();
int length = content.size();
int pLength = length;
int fLength = 0;
unsigned char *plainText = (unsigned char*) malloc(pLength + AES_BLOCK_SIZE);
if (!EVP_DecryptUpdate(de, plainText, &pLength, (unsigned char*) input, length)) {
qCritical() << "EVP_DecryptUpdate() -- " << ERR_error_string(ERR_get_error(), NULL);
free(plainText);
return QByteArray();
}
if (!EVP_DecryptFinal_ex(de, plainText + pLength, &fLength)) {
qCritical() << "EVP_DecryptFinal_ex() -- " << ERR_error_string(ERR_get_error(), NULL);
free(plainText);
return QByteArray();
}
length = pLength + fLength;
EVP_CIPHER_CTX_cleanup(de);
QByteArray output = QByteArray(reinterpret_cast<char*> (plainText), length);
free(plainText);
return output;
}