Add decryption callback to CryptoHandler

Author: tadfisher

app/build.gradle.kts

@@ -55,6 +55,7 @@ dependencies {
   coreLibraryDesugaring(libs.android.desugarJdkLibs)
   implementation(projects.autofillParser)
   implementation(projects.coroutineUtils)
+  implementation(projects.cryptoHwsecurity)
   implementation(projects.cryptoPgpainless)
   implementation(projects.formatCommon)
   implementation(projects.passgen.diceware)

app/src/main/java/app/passwordstore/Application.kt

@@ -12,6 +12,7 @@ import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_AUTO_BATTERY
 import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_FOLLOW_SYSTEM
 import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_NO
 import androidx.appcompat.app.AppCompatDelegate.MODE_NIGHT_YES
+import app.passwordstore.crypto.HWSecurityManager
 import app.passwordstore.injection.context.FilesDirPath
 import app.passwordstore.injection.prefs.SettingsPreferences
 import app.passwordstore.util.extensions.getString
@@ -43,14 +44,15 @@ class Application : android.app.Application(), SharedPreferences.OnSharedPrefere
   @Inject lateinit var proxyUtils: ProxyUtils
   @Inject lateinit var gitSettings: GitSettings
   @Inject lateinit var features: Features
+  @Inject lateinit var deviceManager: HWSecurityManager
 
   override fun onCreate() {
     super.onCreate()
     instance = this
-    if (
-      BuildConfig.ENABLE_DEBUG_FEATURES ||
-        prefs.getBoolean(PreferenceKeys.ENABLE_DEBUG_LOGGING, false)
-    ) {
+
+    val enableLogging = BuildConfig.ENABLE_DEBUG_FEATURES ||
+      prefs.getBoolean(PreferenceKeys.ENABLE_DEBUG_LOGGING, false)
+    if (enableLogging) {
       LogcatLogger.install(AndroidLogcatLogger(DEBUG))
       setVmPolicy()
     }
@@ -60,6 +62,7 @@ class Application : android.app.Application(), SharedPreferences.OnSharedPrefere
     runMigrations(filesDirPath, prefs, gitSettings)
     proxyUtils.setDefaultProxy()
     DynamicColors.applyToActivitiesIfAvailable(this)
+    deviceManager.init(enableLogging)
     Sentry.configureScope { scope ->
       val user = User()
       user.data =

app/src/main/java/app/passwordstore/data/crypto/CryptoRepository.kt

@@ -6,23 +6,27 @@
 package app.passwordstore.data.crypto
 
 import app.passwordstore.crypto.GpgIdentifier
+import app.passwordstore.crypto.HWSecurityDeviceHandler
 import app.passwordstore.crypto.PGPKeyManager
 import app.passwordstore.crypto.PGPainlessCryptoHandler
 import app.passwordstore.crypto.errors.CryptoHandlerException
 import com.github.michaelbull.result.Result
 import com.github.michaelbull.result.getAll
+import com.github.michaelbull.result.getOrThrow
 import com.github.michaelbull.result.unwrap
 import java.io.ByteArrayInputStream
 import java.io.ByteArrayOutputStream
 import javax.inject.Inject
 import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.runBlocking
 import kotlinx.coroutines.withContext
 
 class CryptoRepository
 @Inject
 constructor(
   private val pgpKeyManager: PGPKeyManager,
   private val pgpCryptoHandler: PGPainlessCryptoHandler,
+  private val deviceHandler: HWSecurityDeviceHandler
 ) {
 
   suspend fun decrypt(
@@ -43,7 +47,11 @@ constructor(
     out: ByteArrayOutputStream,
   ): Result<Unit, CryptoHandlerException> {
     val keys = pgpKeyManager.getAllKeys().unwrap()
-    return pgpCryptoHandler.decrypt(keys, password, message, out)
+    return pgpCryptoHandler.decrypt(keys, password, message, out) { encryptedSessionKey ->
+      runBlocking {
+        deviceHandler.decryptSessionKey(encryptedSessionKey).getOrThrow()
+      }
+    }
   }
 
   private suspend fun encryptPgp(

app/src/main/java/app/passwordstore/injection/crypto/CryptoHandlerModule.kt

@@ -5,14 +5,30 @@
 
 package app.passwordstore.injection.crypto
 
+import android.app.Activity
+import androidx.fragment.app.FragmentActivity
+import app.passwordstore.crypto.HWSecurityDeviceHandler
+import app.passwordstore.crypto.HWSecurityManager
 import app.passwordstore.crypto.PGPainlessCryptoHandler
 import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn
-import dagger.hilt.components.SingletonComponent
+import dagger.hilt.android.components.ActivityComponent
+import dagger.hilt.android.scopes.ActivityScoped
 
 @Module
-@InstallIn(SingletonComponent::class)
+@InstallIn(ActivityComponent::class)
 object CryptoHandlerModule {
+
+  @Provides
+  @ActivityScoped
+  fun provideDeviceHandler(
+    activity: Activity,
+    deviceManager: HWSecurityManager
+  ): HWSecurityDeviceHandler = HWSecurityDeviceHandler(
+    deviceManager = deviceManager,
+    fragmentManager = (activity as FragmentActivity).supportFragmentManager
+  )
+
   @Provides fun providePgpCryptoHandler() = PGPainlessCryptoHandler()
 }

crypto-common/src/main/kotlin/app/passwordstore/crypto/CryptoHandler.kt

@@ -11,7 +11,7 @@ import java.io.InputStream
 import java.io.OutputStream
 
 /** Generic interface to implement cryptographic operations on top of. */
-public interface CryptoHandler<Key> {
+public interface CryptoHandler<Key, EncryptedSessionKey, DecryptedSessionKey> {
 
   /**
    * Decrypt the given [ciphertextStream] using a set of potential [keys] and [passphrase], and
@@ -24,6 +24,7 @@ public interface CryptoHandler<Key> {
     passphrase: String,
     ciphertextStream: InputStream,
     outputStream: OutputStream,
+    onDecryptSessionKey: (EncryptedSessionKey) -> DecryptedSessionKey,
   ): Result<Unit, CryptoHandlerException>
 
   /**

crypto-pgpainless/src/main/kotlin/app/passwordstore/crypto/KeyUtils.kt

@@ -10,6 +10,11 @@ import app.passwordstore.crypto.GpgIdentifier.UserId
 import com.github.michaelbull.result.get
 import com.github.michaelbull.result.runCatching
 import org.bouncycastle.openpgp.PGPKeyRing
+import org.bouncycastle.openpgp.PGPSecretKey
+import org.bouncycastle.openpgp.PGPSecretKeyRing
+import org.pgpainless.algorithm.EncryptionPurpose
+import org.pgpainless.key.OpenPgpFingerprint
+import org.pgpainless.key.info.KeyRingInfo
 import org.pgpainless.key.parsing.KeyRingReader
 
 /** Utility methods to deal with [PGPKey]s. */
@@ -32,4 +37,25 @@ public object KeyUtils {
     val keyRing = tryParseKeyring(key) ?: return null
     return UserId(keyRing.publicKey.userIDs.next())
   }
+  public fun tryGetEncryptionKeyFingerprint(key: PGPKey): OpenPgpFingerprint? {
+    val keyRing = tryParseKeyring(key) ?: return null
+    val encryptionSubkey =
+      KeyRingInfo(keyRing).getEncryptionSubkeys(EncryptionPurpose.ANY).lastOrNull()
+    return encryptionSubkey?.let(OpenPgpFingerprint::of)
+  }
+
+  public fun tryGetEncryptionKey(key: PGPKey): PGPSecretKey? {
+    val keyRing = tryParseKeyring(key) as? PGPSecretKeyRing ?: return null
+    return tryGetEncryptionKey(keyRing)
+  }
+
+  public fun tryGetEncryptionKey(keyRing: PGPSecretKeyRing): PGPSecretKey? {
+    val info = KeyRingInfo(keyRing)
+    return tryGetEncryptionKey(info)
+  }
+
+  private fun tryGetEncryptionKey(info: KeyRingInfo): PGPSecretKey? {
+    val encryptionKey = info.getEncryptionSubkeys(EncryptionPurpose.ANY).lastOrNull() ?: return null
+    return info.getSecretKey(encryptionKey.keyID)
+  }
 }

crypto-pgpainless/src/main/kotlin/app/passwordstore/crypto/PGPainlessCryptoHandler.kt

@@ -14,26 +14,31 @@ import com.github.michaelbull.result.mapError
 import com.github.michaelbull.result.runCatching
 import java.io.InputStream
 import java.io.OutputStream
-import javax.inject.Inject
+import org.bouncycastle.CachingPublicKeyDataDecryptorFactory
 import org.bouncycastle.openpgp.PGPPublicKeyRing
 import org.bouncycastle.openpgp.PGPPublicKeyRingCollection
 import org.bouncycastle.openpgp.PGPSecretKeyRing
 import org.bouncycastle.openpgp.PGPSecretKeyRingCollection
+import org.bouncycastle.openpgp.PGPSessionKey
 import org.pgpainless.PGPainless
+import org.pgpainless.algorithm.PublicKeyAlgorithm
 import org.pgpainless.decryption_verification.ConsumerOptions
+import org.pgpainless.decryption_verification.HardwareSecurity
+import org.pgpainless.decryption_verification.HardwareSecurity.HardwareDataDecryptorFactory
 import org.pgpainless.encryption_signing.EncryptionOptions
 import org.pgpainless.encryption_signing.ProducerOptions
 import org.pgpainless.exception.WrongPassphraseException
 import org.pgpainless.key.protection.SecretKeyRingProtector
 import org.pgpainless.util.Passphrase
 
-public class PGPainlessCryptoHandler @Inject constructor() : CryptoHandler<PGPKey> {
+public class PGPainlessCryptoHandler : CryptoHandler<PGPKey, PGPEncryptedSessionKey, PGPSessionKey> {
 
   public override fun decrypt(
     keys: List<PGPKey>,
     passphrase: String,
     ciphertextStream: InputStream,
     outputStream: OutputStream,
+    onDecryptSessionKey: (PGPEncryptedSessionKey) -> PGPSessionKey
   ): Result<Unit, CryptoHandlerException> =
     runCatching {
         if (keys.isEmpty()) throw NoKeysProvided("No keys provided for encryption")
@@ -42,18 +47,41 @@ public class PGPainlessCryptoHandler @Inject constructor() : CryptoHandler<PGPKe
             .map { key -> PGPainless.readKeyRing().secretKeyRing(key.contents) }
             .run(::PGPSecretKeyRingCollection)
         val protector = SecretKeyRingProtector.unlockAnyKeyWith(Passphrase.fromPassword(passphrase))
+        val hardwareBackedKeys =
+          keyringCollection.mapNotNull { keyring ->
+            KeyUtils.tryGetEncryptionKey(keyring)
+              ?.takeIf { it.keyID in HardwareSecurity.getIdsOfHardwareBackedKeys(keyring) }
+          }
         PGPainless.decryptAndOrVerify()
           .onInputStream(ciphertextStream)
           .withOptions(
-            ConsumerOptions()
-              .addDecryptionKeys(keyringCollection, protector)
-              .addDecryptionPassphrase(Passphrase.fromPassword(passphrase))
+            ConsumerOptions().apply {
+                for (key in hardwareBackedKeys) {
+                  addCustomDecryptorFactory(
+                    setOf(key.keyID),
+                    CachingPublicKeyDataDecryptorFactory(
+                      HardwareDataDecryptorFactory { keyAlgorithm, secKeyData ->
+                        onDecryptSessionKey(
+                          PGPEncryptedSessionKey(
+                            key.publicKey,
+                            PublicKeyAlgorithm.requireFromId(keyAlgorithm),
+                            secKeyData
+                          )
+                        ).key
+                      }
+                    )
+                  )
+                }
+                addDecryptionKeys(keyringCollection, protector)
+                addDecryptionPassphrase(Passphrase.fromPassword(passphrase))
+            }
           )
           .use { decryptionStream -> decryptionStream.copyTo(outputStream) }
         return@runCatching
       }
       .mapError { error ->
         when (error) {
+          is CryptoHandlerException -> error
           is WrongPassphraseException -> IncorrectPassphraseException(error)
           else -> UnknownError(error)
         }

crypto-pgpainless/src/main/kotlin/org/bouncycastle/CachingPublicKeyDataDecryptorFactory.kt

@@ -0,0 +1,50 @@
+// SPDX-FileCopyrightText: 2022 Paul Schaub <[email protected]>
+//
+// SPDX-License-Identifier: Apache-2.0
+
+package org.bouncycastle
+
+import org.bouncycastle.openpgp.PGPException
+import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory
+import org.bouncycastle.util.encoders.Base64
+
+/**
+ * Implementation of the [PublicKeyDataDecryptorFactory] which caches decrypted session keys.
+ * That way, if a message needs to be decrypted multiple times, expensive private key operations can be omitted.
+ *
+ * This implementation changes the behavior or [.recoverSessionData] to first return any
+ * cache hits.
+ * If no hit is found, the method call is delegated to the underlying [PublicKeyDataDecryptorFactory].
+ * The result of that is then placed in the cache and returned.
+ *
+ * TODO: Do we also cache invalid session keys?
+ */
+public class CachingPublicKeyDataDecryptorFactory(
+  private val factory: PublicKeyDataDecryptorFactory
+) : PublicKeyDataDecryptorFactory by factory {
+
+  private val cachedSessionKeys: MutableMap<String, ByteArray> = mutableMapOf()
+
+  @Throws(PGPException::class)
+  override fun recoverSessionData(keyAlgorithm: Int, secKeyData: Array<ByteArray>): ByteArray {
+    return cachedSessionKeys.getOrPut(cacheKey(secKeyData)) {
+      factory.recoverSessionData(keyAlgorithm, secKeyData)
+    }.copy()
+  }
+
+  public fun clear() {
+    cachedSessionKeys.clear()
+  }
+
+  private companion object {
+    fun cacheKey(secKeyData: Array<ByteArray>): String {
+      return Base64.toBase64String(secKeyData[0])
+    }
+
+    private fun ByteArray.copy(): ByteArray {
+      val copy = ByteArray(size)
+      System.arraycopy(this, 0, copy, 0, copy.size)
+      return copy
+    }
+  }
+}