Parse JWT Header

Jot.xcodeproj/project.pbxproj

@@ -7,18 +7,15 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		821E160721D7ED3F00E2D71A /* TokenDeserializer.swift in Sources */ = {isa = PBXBuildFile; fileRef = 821E160621D7ED3F00E2D71A /* TokenDeserializer.swift */; };
 		82CAF46A21D7D41800FED241 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF46921D7D41800FED241 /* AppDelegate.swift */; };
 		82CAF46C21D7D41C00FED241 /* Assets.xcassets in Resources */ = {isa = PBXBuildFile; fileRef = 82CAF46B21D7D41C00FED241 /* Assets.xcassets */; };
 		82CAF46F21D7D41C00FED241 /* MainMenu.xib in Resources */ = {isa = PBXBuildFile; fileRef = 82CAF46D21D7D41C00FED241 /* MainMenu.xib */; };
 		82CAF47B21D7D41C00FED241 /* JotTests.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF47A21D7D41C00FED241 /* JotTests.swift */; };
 		82CAF48821D7D56D00FED241 /* JWT.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48721D7D56D00FED241 /* JWT.swift */; };
-		82CAF48921D7D57700FED241 /* JWT.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48721D7D56D00FED241 /* JWT.swift */; };
 		82CAF48B21D7D5B700FED241 /* Payload.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48A21D7D5B700FED241 /* Payload.swift */; };
 		82CAF48D21D7D60100FED241 /* Header.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48C21D7D60000FED241 /* Header.swift */; };
 		82CAF48F21D7D81800FED241 /* Signature.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48E21D7D81800FED241 /* Signature.swift */; };
-		82CAF49021D7DC5100FED241 /* Payload.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48A21D7D5B700FED241 /* Payload.swift */; };
-		82CAF49121D7DC5300FED241 /* Header.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48C21D7D60000FED241 /* Header.swift */; };
-		82CAF49221D7DC5600FED241 /* Signature.swift in Sources */ = {isa = PBXBuildFile; fileRef = 82CAF48E21D7D81800FED241 /* Signature.swift */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -32,6 +29,7 @@
 /* End PBXContainerItemProxy section */
 
 /* Begin PBXFileReference section */
+		821E160621D7ED3F00E2D71A /* TokenDeserializer.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = TokenDeserializer.swift; sourceTree = "<group>"; };
 		82CAF46621D7D41800FED241 /* Jot.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Jot.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		82CAF46921D7D41800FED241 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		82CAF46B21D7D41C00FED241 /* Assets.xcassets */ = {isa = PBXFileReference; lastKnownFileType = folder.assetcatalog; path = Assets.xcassets; sourceTree = "<group>"; };
@@ -113,6 +111,7 @@
 				82CAF48A21D7D5B700FED241 /* Payload.swift */,
 				82CAF48C21D7D60000FED241 /* Header.swift */,
 				82CAF48E21D7D81800FED241 /* Signature.swift */,
+				821E160621D7ED3F00E2D71A /* TokenDeserializer.swift */,
 			);
 			path = Token;
 			sourceTree = "<group>";
@@ -224,6 +223,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
+				821E160721D7ED3F00E2D71A /* TokenDeserializer.swift in Sources */,
 				82CAF48D21D7D60100FED241 /* Header.swift in Sources */,
 				82CAF48B21D7D5B700FED241 /* Payload.swift in Sources */,
 				82CAF46A21D7D41800FED241 /* AppDelegate.swift in Sources */,
@@ -236,11 +236,7 @@
 			isa = PBXSourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				82CAF49121D7DC5300FED241 /* Header.swift in Sources */,
-				82CAF49021D7DC5100FED241 /* Payload.swift in Sources */,
 				82CAF47B21D7D41C00FED241 /* JotTests.swift in Sources */,
-				82CAF49221D7DC5600FED241 /* Signature.swift in Sources */,
-				82CAF48921D7D57700FED241 /* JWT.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};

Jot/Token/Header.swift

@@ -23,7 +23,9 @@ enum JwtType: String, Codable {
 }
 
 enum SigningAlgorithm: String, Codable {
-    case rsa = "RSA"
+    case rsa256 = "RS256"
-    case hmac = "HMAC"
+    case rsa384 = "RS384"
-    case ecdsa = "ECDSA"
+    case rsa512 = "RS512"
+    case hmac256 = "HM256"
+    case ecdsa256 = "ES256"
 }

Jot/Token/JWT.swift

@@ -9,19 +9,13 @@
 import Foundation
 
 class JWT {
-    private let header: Header
+    let header: Header
-    private let payload: Payload
+    let payload: Payload
-    private let signature: Signature
+    let signature: Signature
     
     init(header: Header, payload: Payload, signature: Signature) {
         self.header = header
         self.payload = payload
         self.signature = signature
     }
-    
-    init?(token: String) {
-        return nil
-    }
 }
-
-

Jot/Token/TokenDeserializer.swift

@@ -0,0 +1,62 @@
+//
+//  TokenDeserializer.swift
+//  Jot
+//
+//  Created by James Griffin-Allwood on 2018-12-29.
+//  Copyright © 2018 James Griffin-Allwood. All rights reserved.
+//
+
+import Foundation
+import os.log
+
+extension JWT {
+    convenience init?(token: String) {
+        let decoder = JSONDecoder()
+        let jwtParts = token.split(separator: ".")
+        guard jwtParts.count == 3 else {
+            os_log("Invalid JWT format. Requires 3 parts", log: OSLog.default, type: .error)
+            return nil
+        }
+        
+        let base64Header = String(jwtParts[0])
+        guard let headerData = Data(base64Encoded: base64Header.base64Pad()) else {
+            os_log("Header must be Base64 Encoded", log: OSLog.default, type: .error)
+            return nil
+        }
+        
+        
+        let base64Payload = String(jwtParts[1])
+        guard let payloadData = Data(base64Encoded: base64Payload.base64Pad()) else {
+            os_log("Payload must be Base64 Encoded", log: OSLog.default, type: .error)
+            return nil
+        }
+        
+        // TODO: Base64 Decoding the signature fails. Leave alone until adding Token Validation
+        // let base64Signature = String(jwtParts[2])
+        // guard let signatureData = Data(base64Encoded: base64Signature.base64Pad()) else {
+        //     os_log("Signature must be Base64 Encoded", log: OSLog.default, type: .error)
+        //     return nil
+        // }
+        
+        do {
+            let header = try decoder.decode(Header.self, from: headerData)
+            let payload = try decoder.decode(Payload.self, from: payloadData)
+            let signature = Signature()
+            self.init(header: header, payload: payload, signature: signature)
+        } catch {
+            os_log("Unable to deserialize JWT: %@", log: OSLog.default, type: .error, error.localizedDescription)
+            return nil
+        }
+    }
+}
+
+extension String {
+    func base64Pad() -> String {
+        var paddedString = self
+        if self.count % 4 != 0 {
+            let charactersToAdd = 4 - self.count % 4
+            paddedString.append(contentsOf: repeatElement("=", count: charactersToAdd))
+        }
+        return paddedString
+    }
+}

JotTests/JotTests.swift

@@ -10,13 +10,15 @@ import XCTest
 @testable import Jot
 
 class JotTests: XCTestCase {
-    var jwt: JWT?
-
-    override func setUp() {
-        self.jwt = JWT(token: "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJqZ3JpZmZpbiIsIm5hbWUiOiJKYW1lcyBHcmlmZmluIiwiYWRtaW4iOnRydWUsImlhdCI6MTUxNjIzOTAyMn0.DXfNW7Gzvie7LIl5-HSG9clm3sjeglYG2uNmsPvcNerBQbzLI06vys4YqqCMtrWKEFij_y2hKGP9YFdHSRMdtyVcGEXmYP6H6E62uGhASmGFzEHeSa6B1X1-v8lRt_YpIGEXhkUnxfhdcQ90HJlNfajv0ndnRFk8YJxRkmr99OI")
-    }
 
     func testJWTInit() {
-        XCTAssertNotNil(self.jwt)
+        guard let jwt = JWT(token:  "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJzdWIiOiJqZ3JpZmZpbiIsIm5hbWUiOiJKYW1lcyBHcmlmZmluIiwiYWRtaW4iOnRydWUsImlhdCI6MTUxNjIzOTAyMn0.DXfNW7Gzvie7LIl5-HSG9clm3sjeglYG2uNmsPvcNerBQbzLI06vys4YqqCMtrWKEFij_y2hKGP9YFdHSRMdtyVcGEXmYP6H6E62uGhASmGFzEHeSa6B1X1-v8lRt_YpIGEXhkUnxfhdcQ90HJlNfajv0ndnRFk8YJxRkmr99OI") else {
+            XCTFail()
+            return
+        }
+        
+        XCTAssertEqual(jwt.header.alg, SigningAlgorithm.rsa256)
+        XCTAssertEqual(jwt.header.typ, JwtType.jwt)
     }
+    
 }