Migrate existing Objective-C code to Swift [SDK-2905]

Auth0.podspec

@@ -1,10 +1,4 @@
 web_auth_files = [
-  'Auth0/ObjectiveC/A0ChallengeGenerator.h',
-  'Auth0/ObjectiveC/A0ChallengeGenerator.m',
-  'Auth0/ObjectiveC/A0RSA.h',
-  'Auth0/ObjectiveC/A0RSA.m',
-  'Auth0/ObjectiveC/A0SHA.h',
-  'Auth0/ObjectiveC/A0SHA.m',
   'Auth0/Array+Encode.swift',
   'Auth0/ASCallbackTransaction.swift',
   'Auth0/ASTransaction.swift',
@@ -14,6 +8,7 @@ web_auth_files = [
   'Auth0/BaseCallbackTransaction.swift',
   'Auth0/BaseTransaction.swift',
   'Auth0/BioAuthentication.swift',
+  'Auth0/ChallengeGenerator.swift',
   'Auth0/ClaimValidators.swift',
   'Auth0/IDTokenSignatureValidator.swift',
   'Auth0/IDTokenValidator.swift',
@@ -61,24 +56,22 @@ Pod::Spec.new do |s|
   s.tvos.deployment_target = '12.0'
   s.requires_arc = true
 
-  s.ios.source_files = 'Auth0/*.{swift,h,m}', 'Auth0/ObjectiveC/*.{h,m}'
+  s.ios.source_files = 'Auth0/*.swift'
   s.ios.exclude_files = macos_files
   s.ios.frameworks = 'UIKit', 'LocalAuthentication', 'AuthenticationServices'
   s.ios.dependency 'SimpleKeychain'
   s.ios.dependency 'JWTDecode', '~> 2.0'
   s.ios.pod_target_xcconfig = {
-    'SWIFT_ACTIVE_COMPILATION_CONDITIONS' => 'WEB_AUTH_PLATFORM',
-    'GCC_PREPROCESSOR_DEFINITIONS' => '$(inherited) WEB_AUTH_PLATFORM=1'
+    'SWIFT_ACTIVE_COMPILATION_CONDITIONS' => 'WEB_AUTH_PLATFORM'
   }
 
-  s.osx.source_files = 'Auth0/*.{swift,h,m}', 'Auth0/ObjectiveC/*.{h,m}'
+  s.osx.source_files = 'Auth0/*.swift'
   s.osx.exclude_files = ios_files
   s.osx.frameworks = 'AppKit', 'LocalAuthentication', 'AuthenticationServices'
   s.osx.dependency 'SimpleKeychain'
   s.osx.dependency 'JWTDecode', '~> 2.0'
   s.osx.pod_target_xcconfig = {
-    'SWIFT_ACTIVE_COMPILATION_CONDITIONS' => 'WEB_AUTH_PLATFORM',
-    'GCC_PREPROCESSOR_DEFINITIONS' => '$(inherited) WEB_AUTH_PLATFORM=1'
+    'SWIFT_ACTIVE_COMPILATION_CONDITIONS' => 'WEB_AUTH_PLATFORM'
   }
 
   s.watchos.source_files = 'Auth0/*.swift'

Auth0/ChallengeGenerator.swift

@@ -0,0 +1,31 @@
+import Foundation
+import CommonCrypto
+
+private func getVerifier() -> String? {
+    let data = Data(count: 32)
+    var tempData = data
+    _ = tempData.withUnsafeMutableBytes {
+        SecRandomCopyBytes(kSecRandomDefault, data.count, $0.baseAddress!)
+    }
+    return tempData.a0_encodeBase64URLSafe()
+}
+
+private func getChallenge(for verifier: String) -> String? {
+    guard let data = verifier.data(using: .utf8) else { return nil }
+    var buffer = [UInt8](repeating: 0, count: Int(CC_SHA256_DIGEST_LENGTH))
+    _ = data.withUnsafeBytes {
+        CC_SHA256($0.baseAddress, CC_LONG(data.count), &buffer)
+    }
+    return Data(buffer).a0_encodeBase64URLSafe()
+}
+
+struct ChallengeGenerator {
+    let verifier: String
+    let challenge: String
+    let method = "S256"
+
+    init(verifier: String? = nil) {
+        self.verifier = verifier ?? getVerifier()!
+        self.challenge = getChallenge(for: self.verifier)!
+    }
+}

Auth0/JWTAlgorithm.swift

@@ -1,9 +1,5 @@
-#if WEB_AUTH_PLATFORM
 import Foundation
 import JWTDecode
-#if SWIFT_PACKAGE
-import Auth0ObjectiveC
-#endif
 
 enum JWTAlgorithm: String {
     case rs256 = "RS256"
@@ -22,10 +18,9 @@ enum JWTAlgorithm: String {
             !signature.isEmpty else { return false }
         switch self {
         case .rs256:
-            guard let publicKey = jwk.rsaPublicKey, let rsa = A0RSA(key: publicKey) else { return false }
-            let sha256 = A0SHA()
-            return rsa.verify(sha256.hash(data), signature: signature)
+            return SecKeyVerifySignature(
+                jwk.rsaPublicKey!, .rsaSignatureMessagePKCS1v15SHA256, data as CFData, signature as CFData, nil
+            )
         }
     }
 }
-#endif

Auth0/OAuth2Grant.swift

@@ -1,9 +1,5 @@
-#if WEB_AUTH_PLATFORM
 import Foundation
 import JWTDecode
-#if SWIFT_PACKAGE
-import Auth0ObjectiveC
-#endif
 
 protocol OAuth2Grant {
     var defaults: [String: String] { get }
@@ -23,7 +19,7 @@ struct PKCE: OAuth2Grant {
     let organization: String?
 
     init(authentication: Authentication,
-         generator: A0SHA256ChallengeGenerator = A0SHA256ChallengeGenerator(),
+         generator: ChallengeGenerator = ChallengeGenerator(),
          redirectURL: URL,
          issuer: String,
          leeway: Int,
@@ -109,4 +105,3 @@ struct PKCE: OAuth2Grant {
     }
 
 }
-#endif