C_Decrypt sometimes fails to decrypt properly

[bgh34056]

The data which ai am passing for encryption is "1111111111111111" no IV , no padding used .

Code To Encrypt :
`
encryptMech = { CKM_AES_ECB, NULL, 0 };

//CK_BYTE plainText[] = "Hello, this is the plaintext to be encrypted.";

// Initialize encryption
std::vector<unsigned char> plainText(challenge.begin(), challenge.end());
CK_ULONG ulPlainTextLen = plainText.size();

CK_ULONG ulCipherTextLen;
rv = pFunctionList->C_EncryptInit(session, &encryptMech, hKey);
if (rv != CKR_OK) {
    std::cerr << "Failed to initialize encryption. Error: " << rv << std::endl;
    cleanupSessionAndFinalize(session);
    return std::vector<unsigned char>(); // Return an empty vector to indicate failure
}

// Get the required buffer size for the ciphertext
rv = pFunctionList->C_Encrypt(session, plainText.data(), ulPlainTextLen, nullptr, &ulCipherTextLen);
if (rv != CKR_OK) {
    std::cerr << "1. Encryption failed. Error: " << rv << std::endl;
    cleanupSessionAndFinalize(session);
    return std::vector<unsigned char>(); // Return an empty vector to indicate failure
}

// Resize the ciphertext vector to accommodate the encrypted data
ciphertext.resize(ulCipherTextLen);

// Perform the encryption
rv = pFunctionList->C_Encrypt(session, plainText.data(), ulPlainTextLen, ciphertext.data(), &ulCipherTextLen);
if (rv != CKR_OK) {
    std::cerr << "2. Encryption failed. Error: " << rv << std::endl;
    cleanupSessionAndFinalize(session);
    return std::vector<unsigned char>(); // Return an empty vector to indicate failure
}

Code To Decrypt : // Perform the decryption
CK_BYTE_PTR tempCipherText = const_cast<CK_BYTE_PTR>(cipherText.data());
CK_ULONG ulCipherTextLen = cipherText.size();

CK_MECHANISM decryptMech = { CKM_AES_ECB, NULL, 0 };
rv = pFunctionList->C_DecryptInit(session, &decryptMech, hKey);
if (rv != CKR_OK) {
    std::cerr << "Failed to initialize decryption. Error: " << rv << std::endl;
    cleanupSessionAndFinalize(session);
    return std::vector<CK_BYTE>(); // Return an empty vector on error
}

CK_ULONG ulPlainTextLen = 0; // Initialize to 0 to get the actual length after decryption
rv = pFunctionList->C_Decrypt(session, tempCipherText, ulCipherTextLen, nullptr, &ulPlainTextLen);
if (rv != CKR_OK && rv != CKR_DATA_LEN_RANGE) {
    std::cerr << "Failed to determine decrypted data length. Error: " << rv << std::endl;
    cleanupSessionAndFinalize(session);
    return std::vector<CK_BYTE>(); // Return an empty vector on error
}

std::vector<CK_BYTE> decryptedText(ulPlainTextLen);
//CK_BYTE_PTR tempPlainText = decryptedText.data();

//rv = pFunctionList->C_Decrypt(session, tempCipherText, ulCipherTextLen, tempPlainText, &ulPlainTextLen);
rv = pFunctionList->C_Decrypt(session, tempCipherText, ulCipherTextLen, &decryptedText.front(), &ulPlainTextLen);
if (rv != CKR_OK) {
    std::cerr << "Decryption failed. Error: " << rv << std::endl;
    cleanupSessionAndFinalize(session);
    return std::vector<CK_BYTE>(); // Return an empty vector on error
}

`
When C_Decrypt is successful but the decrypted data sometimes is not matching the original value.

Like when it is matching Output is :

Encrypted data length: 16
Encrypted plainText:
79 eb 4d cf bc b2 26 ce 54 d3 24 ec 99 b3 79 ba
Decrypted data length: 16
Decrypted decryptedText:
11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
decrypted challenge: 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
original challenge: 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
Authentication successful!

When it is matching the Output is :

Connection from: 127.0.0.1, Port: 39944
Generated challenge: 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
SSL_write: challenge 16
SSL_read: responseBuffer : 1048
responseReceived: 79 eb 4d cf bc b2 26 ce 54 d3 24 ec 99 b3 79 ba
bytes read: 16
Encrypted data length: 16
Encrypted plainText:
79 eb 4d cf bc b2 26 ce 54 d3 24 ec 99 b3 79 ba
Decrypted data length: 16
Decrypted decryptedText:
ed 7a 9f 59 52 36 88 49 98 3c 38 81 9e 37 7a 62
decrypted challenge: ed 7a 9f 59 52 36 88 49 98 3c 38 81 9e 37 7a 62
original challenge: 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
Authentication failed!

I would Like to know if the above code is correct or is there an issue with C_Decrypt itself