Implement DPoP

ref DEV-1446

sdk/src/main/java/com/oursky/authgear/AuthenticateOptions.kt

@@ -76,7 +76,8 @@ data class AuthenticateOptions @JvmOverloads constructor(
 
 internal fun AuthenticateOptions.toRequest(
     isSsoEnabled: Boolean,
-    preAuthenticatedURLEnabled: Boolean
+    preAuthenticatedURLEnabled: Boolean,
+    dpopJKT: String?
 ): OidcAuthenticationRequest {
     return OidcAuthenticationRequest(
         redirectUri = this.redirectUri,
@@ -93,6 +94,7 @@ internal fun AuthenticateOptions.toRequest(
         colorScheme = this.colorScheme,
         wechatRedirectURI = this.wechatRedirectURI,
         page = this.page,
-        authenticationFlowGroup = this.authenticationFlowGroup
+        authenticationFlowGroup = this.authenticationFlowGroup,
+        dpopJKT = dpopJKT
     )
 }

sdk/src/main/java/com/oursky/authgear/Authgear.kt

@@ -15,6 +15,7 @@ import com.oursky.authgear.app2app.App2AppOptions
 import com.oursky.authgear.data.assetlink.AssetLinkRepoHttp
 import com.oursky.authgear.data.key.KeyRepoKeystore
 import com.oursky.authgear.data.oauth.OAuthRepoHttp
+import com.oursky.authgear.dpop.DefaultDPoPProvider
 import kotlinx.coroutines.*
 import java.util.*
 
@@ -38,6 +39,14 @@ constructor(
     internal val core: AuthgearCore
 
     init {
+        val name = name ?: "default"
+        val keyRepo = KeyRepoKeystore()
+        val sharedStorage = PersistentInterAppSharedStorage(application)
+        val dpopProvider = DefaultDPoPProvider(
+            namespace = name,
+            keyRepo = keyRepo,
+            sharedStorage = sharedStorage,
+        )
         this.core = AuthgearCore(
             this,
             application,
@@ -46,12 +55,13 @@ constructor(
             isSsoEnabled,
             preAuthenticatedURLEnabled,
             app2AppOptions,
+            dpopProvider,
             tokenStorage,
             uiImplementation,
             PersistentContainerStorage(application),
-            PersistentInterAppSharedStorage(application),
-            OAuthRepoHttp(),
-            KeyRepoKeystore(),
+            sharedStorage,
+            OAuthRepoHttp(dPoPProvider = dpopProvider),
+            keyRepo,
             AssetLinkRepoHttp(),
             name
         )

sdk/src/main/java/com/oursky/authgear/AuthgearCore.kt

@@ -20,6 +20,7 @@ import com.oursky.authgear.app2app.App2AppOptions
 import com.oursky.authgear.data.assetlink.AssetLinkRepo
 import com.oursky.authgear.data.key.KeyRepo
 import com.oursky.authgear.data.oauth.OAuthRepo
+import com.oursky.authgear.dpop.DPoPProvider
 import com.oursky.authgear.net.toQueryParameter
 import com.oursky.authgear.oauth.OidcAuthenticationRequest
 import com.oursky.authgear.oauth.OidcTokenRequest
@@ -58,14 +59,15 @@ internal class AuthgearCore(
     private val isSsoEnabled: Boolean,
     private val preAuthenticatedURLEnabled: Boolean,
     private val app2AppOptions: App2AppOptions,
+    private val dPoPProvider: DPoPProvider,
     private val tokenStorage: TokenStorage,
     private val uiImplementation: UIImplementation,
     private val storage: ContainerStorage,
     private val sharedStorage: InterAppSharedStorage,
     private val oauthRepo: OAuthRepo,
     private val keyRepo: KeyRepo,
     private val assetLinkRepo: AssetLinkRepo,
-    name: String? = null
+    private val name: String
 ) {
     companion object {
         @Suppress("unused")
@@ -145,7 +147,6 @@ internal class AuthgearCore(
         val challenge: String
     )
 
-    private val name = name ?: "default"
     private var isInitialized = false
     private var refreshToken: String? = null
     var accessToken: String? = null
@@ -285,7 +286,10 @@ internal class AuthgearCore(
         verifier: Verifier = generateCodeVerifier()
     ): AuthenticationRequest {
         requireIsInitialized()
-        val request = options.toRequest(this.isSsoEnabled, this.preAuthenticatedURLEnabled)
+        val request = options.toRequest(
+            this.isSsoEnabled,
+            this.preAuthenticatedURLEnabled,
+            dpopJKT = dPoPProvider.computeJKT())
         val authorizeUri = authorizeEndpoint(this.clientId, request, verifier)
         return AuthenticationRequest(authorizeUri, request.redirectUri, verifier)
     }

sdk/src/main/java/com/oursky/authgear/InterAppSharedStorage.kt

@@ -9,5 +9,9 @@ internal interface InterAppSharedStorage {
     fun getDeviceSecret(namespace: String): String?
     fun deleteDeviceSecret(namespace: String)
 
+    fun setDPoPKeyId(namespace: String, keyId: String)
+    fun getDPoPKeyId(namespace: String): String?
+    fun deleteDPoPKeyId(namespace: String)
+
     fun onLogout(namespace: String)
-}
+}

sdk/src/main/java/com/oursky/authgear/JWK.kt

@@ -1,10 +1,17 @@
 package com.oursky.authgear
 
+import kotlinx.serialization.encodeToString
+import kotlinx.serialization.json.Json
 import kotlinx.serialization.json.JsonElement
 import kotlinx.serialization.json.JsonObject
 import kotlinx.serialization.json.JsonPrimitive
+import java.math.BigInteger
+import java.security.MessageDigest
 import java.security.PublicKey
 import java.security.interfaces.RSAPublicKey
+import kotlin.io.encoding.Base64
+import kotlin.io.encoding.ExperimentalEncodingApi
+import kotlin.math.ceil
 
 internal data class JWK(
     val kid: String,
@@ -24,11 +31,44 @@ internal fun JWK.toJsonObject(): JsonObject {
     return JsonObject(m)
 }
 
+@OptIn(ExperimentalEncodingApi::class)
+internal fun JWK.toSHA256Thumbprint(): String {
+    val p = mutableMapOf<String, String>()
+    when (kty) {
+        "RSA" -> {
+            // required members for an RSA public key are e, kty, n
+            // in lexicographic order
+            p["e"] = e
+            p["kty"] = kty
+            p["n"] = n
+        }
+        else -> {
+            throw NotImplementedError("unknown kty")
+        }
+    }
+    val jsonBytes = Json.encodeToString(p).toByteArray()
+    val digest: MessageDigest = MessageDigest.getInstance("SHA-256")
+    val hashBytes = digest.digest(jsonBytes)
+
+    return Base64.UrlSafe.encode(hashBytes).removeSuffix("=")
+}
+
+internal fun BigInteger.toUnsignedByteArray(): ByteArray {
+    // BigInteger always include a bit to represent the sign
+    // So the array length is ceil((this.bitLength() + 1)/8)
+    // This sign bit causes an extra byte to be added to the ByteArray when bitLength is just divisible by 8
+    // We want to exclude that extra byte in some cases, such as sending the bytes in a JWK as Base64urlUInt
+    val expectedLength = ceil(this.bitLength() / 8.0).toInt()
+    val bytes = this.toByteArray()
+    val startIdx = bytes.size - expectedLength
+    return bytes.sliceArray(IntRange(startIdx, bytes.size - 1))
+}
+
 internal fun publicKeyToJWK(kid: String, publicKey: PublicKey): JWK {
     val rsaPublicKey = publicKey as RSAPublicKey
     return JWK(
         kid = kid,
-        n = base64UrlEncode(rsaPublicKey.modulus.toByteArray()),
-        e = base64UrlEncode(rsaPublicKey.publicExponent.toByteArray())
+        n = base64UrlEncode(rsaPublicKey.modulus.toUnsignedByteArray()),
+        e = base64UrlEncode(rsaPublicKey.publicExponent.toUnsignedByteArray())
     )
 }

sdk/src/main/java/com/oursky/authgear/JWT.kt

@@ -9,7 +9,8 @@ import java.time.Instant
 internal enum class JWTHeaderType(val value: String) {
     ANONYMOUS("vnd.authgear.anonymous-request"),
     BIOMETRIC("vnd.authgear.biometric-request"),
-    APP2APP("vnd.authgear.app2app-request")
+    APP2APP("vnd.authgear.app2app-request"),
+    DPOPJWT("dpop+jwt")
 }
 
 internal data class JWTHeader(
@@ -33,9 +34,12 @@ internal fun JWTHeader.toJsonObject(): JsonObject {
 internal data class JWTPayload(
     val iat: Long,
     val exp: Long,
-    val challenge: String,
-    val action: String,
-    val deviceInfo: DeviceInfoRoot?
+    val jti: String? = null,
+    val htm: String? = null,
+    val htu: String? = null,
+    val challenge: String? = null,
+    val action: String? = null,
+    val deviceInfo: DeviceInfoRoot? = null
 ) {
     constructor(now: Instant, challenge: String, action: String, deviceInfo: DeviceInfoRoot? = null) : this(
         iat = now.epochSecond,
@@ -44,17 +48,38 @@ internal data class JWTPayload(
         action = action,
         deviceInfo = deviceInfo
     )
+
+    constructor(now: Instant, jti: String, htu: String, htm: String) : this(
+        iat = now.epochSecond,
+        exp = now.epochSecond + 60,
+        jti = jti,
+        htu = htu,
+        htm = htm
+    )
 }
 
 internal fun JWTPayload.toJsonObject(): JsonObject {
     val m = mutableMapOf<String, JsonElement>()
     m["iat"] = JsonPrimitive(iat)
     m["exp"] = JsonPrimitive(exp)
-    m["challenge"] = JsonPrimitive(challenge)
-    m["action"] = JsonPrimitive(action)
-    if (deviceInfo != null) {
+    challenge?.let {
+        m["challenge"] = JsonPrimitive(challenge)
+    }
+    action?.let {
+        m["action"] = JsonPrimitive(action)
+    }
+    deviceInfo?.let {
         m["device_info"] = deviceInfo.toJsonObject()
     }
+    jti?.let {
+        m["jti"] = JsonPrimitive(jti)
+    }
+    htu?.let {
+        m["htu"] = JsonPrimitive(htu)
+    }
+    htm?.let {
+        m["htm"] = JsonPrimitive(htm)
+    }
     return JsonObject(m)
 }
 

sdk/src/main/java/com/oursky/authgear/PersistentInterAppSharedStorage.kt

@@ -16,6 +16,7 @@ internal class PersistentInterAppSharedStorage(val context: Context) : InterAppS
         private const val LOGTAG = "Authgear"
         private const val IDToken = "idToken"
         private const val DeviceSecret = "deviceSecret"
+        private const val DPoPKeyID = "dpopKeyId"
     }
 
     private val masterKey = MasterKey.Builder(context)
@@ -84,9 +85,22 @@ internal class PersistentInterAppSharedStorage(val context: Context) : InterAppS
         deleteItem(namespace, DeviceSecret)
     }
 
+    override fun setDPoPKeyId(namespace: String, keyId: String) {
+        setItem(namespace, DPoPKeyID, keyId)
+    }
+
+    override fun getDPoPKeyId(namespace: String): String? {
+        return getItem(namespace, DPoPKeyID)
+    }
+
+    override fun deleteDPoPKeyId(namespace: String) {
+        deleteItem(namespace, DPoPKeyID)
+    }
+
     override fun onLogout(namespace: String) {
         deleteDeviceSecret(namespace)
         deleteIDToken(namespace)
+        deleteDPoPKeyId(namespace)
     }
 
     private fun handleBackupProblem(e: Exception, namespace: String): Boolean {
@@ -139,4 +153,4 @@ internal class PersistentInterAppSharedStorage(val context: Context) : InterAppS
             EncryptedSharedPreferences.PrefValueEncryptionScheme.AES256_GCM
         )
     }
-}
+}

sdk/src/main/java/com/oursky/authgear/data/key/KeyRepo.kt

@@ -8,4 +8,7 @@ internal interface KeyRepo {
 
     fun generateApp2AppDeviceKey(kid: String): KeyPair
     fun getApp2AppDeviceKey(kid: String): KeyPair?
+
+    fun generateDPoPKey(kid: String): KeyPair
+    fun getDPoPKey(kid: String): KeyPair?
 }

sdk/src/main/java/com/oursky/authgear/data/key/KeyRepoKeystore.kt

@@ -77,4 +77,40 @@ internal class KeyRepoKeystore : KeyRepo {
 
         return KeyPair(entry.certificate.publicKey, entry.privateKey)
     }
+
+    @RequiresApi(api = Build.VERSION_CODES.M)
+    override fun generateDPoPKey(kid: String): KeyPair {
+        val alias = formatApp2AppDeviceKeyAlias(kid)
+        val builder = KeyGenParameterSpec.Builder(
+            alias,
+            KeyProperties.PURPOSE_SIGN or KeyProperties.PURPOSE_VERIFY
+        )
+            .setDigests(KeyProperties.DIGEST_SHA256)
+            .setSignaturePaddings(KeyProperties.SIGNATURE_PADDING_RSA_PKCS1)
+            .setUserAuthenticationRequired(false)
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.N) {
+            builder.setInvalidatedByBiometricEnrollment(false)
+        }
+        val spec = builder.build()
+        val kpg =
+            KeyPairGenerator.getInstance(KeyProperties.KEY_ALGORITHM_RSA, "AndroidKeyStore")
+        kpg.initialize(spec)
+        return kpg.generateKeyPair()
+    }
+
+    @RequiresApi(api = Build.VERSION_CODES.M)
+    override fun getDPoPKey(kid: String): KeyPair? {
+        val alias = formatApp2AppDeviceKeyAlias(kid)
+
+        val ks = KeyStore.getInstance("AndroidKeyStore")
+        ks.load(null)
+
+        val entry = ks.getEntry(alias, null)
+        if (entry !is KeyStore.PrivateKeyEntry) {
+            return null
+        }
+
+        return KeyPair(entry.certificate.publicKey, entry.privateKey)
+    }
 }