add pairing tests

Sources/Keycard/APDUResponse.swift

@@ -19,6 +19,12 @@ struct APDUResponse {
         self.data = rawData.count > 2 ? Array(rawData[0..<(rawData.count - 3)]) : []
     }
     
+    init(sw1: UInt8, sw2: UInt8, data: [UInt8]) {
+        self.sw1 = sw1
+        self.sw2 = sw2
+        self.data = data
+    }
+
     func checkOK() throws -> APDUResponse {
         try checkSW(StatusWord.ok)
     }

Sources/Keycard/CardError.swift

@@ -6,4 +6,5 @@ enum CardError: Error {
     case pinBlocked
     case invalidAuthData
     case invalidMac
+    case communicationError
 }

Tests/KeycardTests/KeycardTests.swift

@@ -108,6 +108,30 @@ final class KeycardTests: XCTestCase {
         let secureChannel = SecureChannel()
         secureChannel.generateSecret(pubKey: pub)
         XCTAssertEqual(secureChannel.secret!, Crypto.shared.secp256k1ECDH(privKey: priv, pubKey: secureChannel.publicKey!))
+        
+        var clientChallenge: [UInt8]? = nil
+        var pairing: [UInt8] = []
+        let sharedSecret = Crypto.shared.random(count: 32)
+        
+        let testChannel = TestCardChannel()
+        testChannel.callback = { (cmd) in
+            if clientChallenge == nil {
+                XCTAssertEqual(cmd.ins, SecureChannelINS.pair.rawValue)
+                XCTAssertEqual(cmd.p1, PairP1.firstStep.rawValue)
+                let cryptogram = Crypto.shared.sha256(sharedSecret + cmd.data)
+                clientChallenge = Crypto.shared.random(count: 32)
+                return APDUResponse(sw1: 0x90, sw2: 0x00, data: cryptogram + clientChallenge!)
+            } else {
+                XCTAssertEqual(Crypto.shared.sha256(sharedSecret + clientChallenge!), cmd.data)
+                let salt = Crypto.shared.random(count: 32)
+                pairing = Crypto.shared.sha256(sharedSecret + salt)
+                return APDUResponse(sw1: 0x90, sw2: 0x00, data: [0x03] + salt)
+            }
+        }
+        
+        XCTAssertNoThrow(try secureChannel.autoPair(channel: testChannel, sharedSecret: sharedSecret))
+        XCTAssertEqual(secureChannel.pairing!.pairingIndex, 3)
+        XCTAssertEqual(secureChannel.pairing!.pairingKey, pairing)
     }
 
     static var allTests = [

Tests/KeycardTests/TestCardChannel.swift

@@ -0,0 +1,14 @@
+@testable import Keycard
+
+class TestCardChannel: CardChannel {
+    var callback: ((APDUCommand) throws -> APDUResponse)?
+    var connected: Bool { get { true } }
+    
+    func send(_ cmd: APDUCommand) throws -> APDUResponse {
+        if callback != nil {
+            return try callback!(cmd)
+        } else {
+            throw CardError.communicationError
+        }
+    }
+}