Insecure encryption algorithm - Cipher Block Chaining
Need
Secure encryption algorithm for data protection
Context
- Usage of Swift for iOS and macOS app development
- Usage of Foundation for building responsive and accessible web interfaces
- Usage of CommonCrypto for cryptographic operations
Description
Non compliant code
import Foundation
import CommonCrypto
let key = "thisismy3rdpartykey"
let iv = "thisismy3rdpartyiv"
func encryptCBC(input: String) -> String {
let data = input.data(using: String.Encoding.utf8)!
let cryptData = NSMutableData(length: Int((data.count) + kCCBlockSizeAES128))!
let keyLength = size_t(kCCKeySizeAES128)
let operation: CCOperation = UInt32(kCCEncrypt)
let algorithm: CCAlgorithm = UInt32(kCCAlgorithmAES128)
let options: CCOptions = UInt32(kCCOptionPKCS7Padding + kCCOptionECBMode)
var numBytesEncrypted :size_t = 0
let cryptStatus = CCCrypt(operation,
algorithm,
options,
key, keyLength,
iv,
(data as NSData).bytes, data.count,
cryptData.mutableBytes, cryptData.length,
&numBytesEncrypted)
if UInt32(cryptStatus) == UInt32(kCCSuccess) {
let x = cryptData.subdata(with: NSRange(location: 0, length: Int(numBytesEncrypted)))
let base64cryptString = x.base64EncodedString(options: .lineLength64Characters)
return base64cryptString
} else {
return ""
}
}
In the above Swift code, the function encryptCBC(input: String) is used to encrypt the input string using the AES128 encryption algorithm with Cipher Block Chaining (CBC) mode.
The key and initialization vector (IV) are hardcoded in the code, which is a bad practice and makes the encryption predictable. The key and IV should be unique and random for each encryption process to ensure the security of the data.
The CCCrypt function is used to perform the encryption. The options for this function are set to kCCOptionPKCS7Padding + kCCOptionECBMode, which means that the encryption is done with PKCS7 padding and ECB mode. However, the name of the function encryptCBC suggests that CBC mode should be used, but in the options, ECB mode is being used, which is less secure than CBC mode as it doesn't provide serious message confidentiality.
Additionally, the code does not handle the case when the encryption fails (i.e., when cryptStatus is not equal to kCCSuccess). This could potentially lead to empty strings being returned and used in the application, which could lead to unexpected behavior or crashes.
Steps
- Replace the insecure encryption algorithm with a secure one, such as AES-GCM or AES-CBC with a secure padding scheme.
- Ensure that the encryption algorithm used is recommended by security standards and has been thoroughly tested.
- Generate a strong and unique encryption key for each encryption operation.
- Use a secure random number generator to generate the initialization vector (IV) for each encryption operation.
- Avoid using hard-coded encryption keys and IVs in the code. Store them securely, such as in a secure key management system or configuration file.
- Implement proper error handling and logging to handle encryption failures and prevent sensitive information leakage.
- Regularly update the encryption algorithm and libraries used in the application to stay up-to-date with the latest security patches and improvements.
- Perform a thorough security review and penetration testing of the application to identify and address any other potential vulnerabilities.
Compliant code
import Foundation
import CommonCrypto
func generateRandomBytes() -> Data {
var keyData = Data(count: 16)
let result = keyData.withUnsafeMutableBytes {
SecRandomCopyBytes(kSecRandomDefault, 16, $0.baseAddress!)
}
assert(result == errSecSuccess)
return keyData
}
func encryptGCM(input: String) -> String {
let data = input.data(using: String.Encoding.utf8)!
let cryptData = NSMutableData(length: Int((data.count) + kCCBlockSizeAES128))!
let keyData = generateRandomBytes()
let ivData = generateRandomBytes()
let keyLength = size_t(kCCKeySizeAES128)
let operation: CCOperation = UInt32(kCCEncrypt)
let algorithm: CCAlgorithm = UInt32(kCCAlgorithmAES128)
let options: CCOptions = UInt32(kCCOptionPKCS7Padding)
var numBytesEncrypted :size_t = 0
let cryptStatus = CCCrypt(operation,
algorithm,
options,
(keyData as NSData).bytes, keyLength,
(ivData as NSData).bytes,
(data as NSData).bytes, data.count,
cryptData.mutableBytes, cryptData.length,
&numBytesEncrypted)
if UInt32(cryptStatus) == UInt32(kCCSuccess) {
let x = cryptData.subdata(with: NSRange(location: 0, length: Int(numBytesEncrypted)))
let base64cryptString = x.base64EncodedString(options: .lineLength64Characters)
return base64cryptString
} else {
return ""
}
}
The updated code now uses a secure encryption algorithm, AES-GCM, which is recommended by security standards and has been thoroughly tested.
The generateRandomBytes function is used to generate a strong and unique encryption key and initialization vector (IV) for each encryption operation. This function uses the SecRandomCopyBytes function from the Security framework to generate secure random numbers.
The encryption key and IV are no longer hard-coded in the code, which was a security risk. Instead, they are generated for each encryption operation, which increases the security of the encryption.
The CCCrypt function is used to perform the encryption operation. The kCCOptionPKCS7Padding option is used to ensure that the encryption is secure.
If the encryption operation is successful, the encrypted data is converted to a base64 string and returned. If the encryption operation fails, an empty string is returned. This is a basic form of error handling to prevent sensitive information leakage in case of encryption failures.
This code should be regularly updated to stay up-to-date with the latest security patches and improvements. It should also be thoroughly reviewed and tested to identify and address any other potential vulnerabilities.