Unexpectedly nil hashing a password - swift

Question

I'm trying to hash a password with SHA256 method:
class CryptoHandler {
static func sha256(_ str: String) -> String? {
let data = str.data(using: String.Encoding.utf8)
let shaData = sha256(data!)
let rc = String(data: shaData, encoding: String.Encoding.utf8) as String?
return rc
}
static func sha256(_ data: Data) -> Data { var res = [UInt8](repeating: 0, count: Int(CC_SHA256_DIGEST_LENGTH)); data.withUnsafeBytes { _ = CC_SHA256($0, CC_LONG(data.count), &res) }; return Data(bytes: res) }
static func getHashedPassword (pwd: String) -> String{
let hash = sha256(pwd)
return hash!
}
}
When I try to execute getHashedPassword ("0123456789") I have the following error in return hash! line:
Thread 1: Fatal error: Unexpectedly found nil while unwrapping an
Optional value
Why this happens? How I can solve it?

Answer 1

The crash occurs because you cannot create a String from encrypted Data. You have to use base64 or hex representation.
This code creates a hex encoded string and doesn't use optionals at all.
class CryptoHandler {
static func sha256(_ str: String) -> String {
let data = Data(str.utf8)
let shaData = sha256(data)
return shaData.hexString
}
static func sha256(_ data: Data) -> Data {
var res = [UInt8](repeating: 0, count: Int(CC_SHA256_DIGEST_LENGTH));
data.withUnsafeBytes { _ = CC_SHA256($0, CC_LONG(data.count), &res) };
return Data(bytes: res)
}
static func getHashedPassword (pwd: String) -> String{
let hash = sha256(pwd)
return hash
}
}
extension Data {
var hexString : String {
return self.map{ String(format:"%02x", $0) }.joined()
}
}
CryptoHandler.getHashedPassword(pwd:"0123456789")

Answer 2

let rc = String(data: shaData, encoding: String.Encoding.utf8) as String?
will return nil value and you are forcing to compiler a value using return hash! Exclamation mark at the end of hash constant in getHashedPassword method.
You can fix it by modifying getHashedPassword method by accepting an optional value
ex:
static func getHashedPassword (pwd: String) -> String?
{
let hash = sha256(pwd)
return hash
}