Get user ID from JWT (JSON web token) - json

Question

I am using the plugin to authenticate WordPress using api-rest : JWT Authentication for WP REST API
From the request to the server I get the following answer:
{
"token": "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJodHRwczpcL1wvbWlob3N0Lm9yZ1wvcHJ1ZWJhcyIsImlhdCI6MTU1MzcyNDM4MSwibmJmIjoxNTUzNzI0MzgxLCJleHAiOjE1NTQzMjkxODEsImRhdGEiOnsidXNlciI6eyJpZCI6IjIifX19.rgi5Q2c8RCoHRp-lJiJN8xQaOavn9T_q8cmf8v1-57o",
"user_email": "abc#test.com",
"user_nicename": "test",
"user_display_name": "Test"
}
So far everything works fine, but I need to know the user ID.
I have read that the token is coded in base64 and within this is the ID. Trying to decode, I see if the ID that I need is there.
In swift with this function I decode the token, but I can not get the dictionary ID.
func decode(_ token: String) -> [String: AnyObject]? {
let string = token.components(separatedBy: ".")
let toDecode = string[1] as String
var stringtoDecode: String = toDecode.replacingOccurrences(of: "-", with: "+") // 62nd char of encoding
stringtoDecode = stringtoDecode.replacingOccurrences(of: "_", with: "/") // 63rd char of encoding
switch (stringtoDecode.utf16.count % 4) {
case 2: stringtoDecode = "\(stringtoDecode)=="
case 3: stringtoDecode = "\(stringtoDecode)="
default: // nothing to do stringtoDecode can stay the same
print("")
}
let dataToDecode = Data(base64Encoded: stringtoDecode, options: [])
let base64DecodedString = NSString(data: dataToDecode!, encoding: String.Encoding.utf8.rawValue)
var values: [String: AnyObject]?
if let string = base64DecodedString {
if let data = string.data(using: String.Encoding.utf8.rawValue, allowLossyConversion: true) {
values = try! JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.allowFragments) as? [String : AnyObject]
}
}
return values
}
The dictionary that returns this function is:
["iss": https://myhost.me/test, "exp": 1554235730, "nbf": 1553630930, "iat": 1553630930, "data": {
user = {
id = 2;
};
}]
How do I get the ID from this dictionary?

Answer 1

Your code is pretty unswifty.
Basically don't use NS... classes in Swift if there is a native equivalent and a JSON dictionary is always value type ([String:Any]).
I recommend to add an Error enum, make the function can throw, decode the serialized token with Decodable and return the Token instance on success
struct Token : Decodable {
let data : UserData
struct UserData : Decodable {
let user : User
struct User : Decodable {
let id : String
}
}
}
You are encouraged to keep the parameter label in the method declaration
enum TokenError : Error {
case invalidJWTFormat, invalidBase64EncodedData
}
func decode(token: String) throws -> Token {
let components = token.components(separatedBy: ".")
guard components.count == 3 else { throw TokenError.invalidJWTFormat }
var decodedString = components[1]
.replacingOccurrences(of: "-", with: "+")
.replacingOccurrences(of: "_", with: "/")
while decodedString.utf16.count % 4 != 0 {
decodedString += "="
}
guard let decodedData = Data(base64Encoded: decodedString) else { throw TokenError.invalidBase64EncodedData }
return try JSONDecoder().decode(Token.self, from: decodedData)
}
and call it
do {
let userID = try decode(token: "eyJ0eXAi.....").data.user.id
} catch { print(error) }