Add `KeyPair` and `KeyManager` to manage keys in the app (#1487)

Co-authored-by: Harsh Shandilya <me@msfjarvis.dev>

2 files changed, 123 insertions, 0 deletions

diff --git a/crypto-pgp/src/main/kotlin/dev/msfjarvis/aps/data/crypto/GPGKeyManager.kt b/crypto-pgp/src/main/kotlin/dev/msfjarvis/aps/data/crypto/GPGKeyManager.kt
new file mode 100644
index 00000000..478d2700
--- /dev/null
+++ b/crypto-pgp/src/main/kotlin/dev/msfjarvis/aps/data/crypto/GPGKeyManager.kt
@@ -0,0 +1,95 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package dev.msfjarvis.aps.data.crypto
+
+import androidx.annotation.VisibleForTesting
+import com.github.michaelbull.result.Result
+import com.github.michaelbull.result.runCatching
+import com.proton.Gopenpgp.crypto.Crypto
+import java.io.File
+import kotlinx.coroutines.CoroutineDispatcher
+import kotlinx.coroutines.withContext
+
+public class GPGKeyManager(filesDir: String, private val dispatcher: CoroutineDispatcher) :
+  KeyManager<GPGKeyPair> {
+
+  private val keyDir = File(filesDir, KEY_DIR_NAME)
+
+  override suspend fun addKey(key: GPGKeyPair, replace: Boolean): Result<GPGKeyPair, Throwable> =
+    withContext(dispatcher) {
+      runCatching {
+        if (!keyDirExists()) throw KeyManagerException.KeyDirectoryUnavailableException
+        val keyFile = File(keyDir, "${key.getKeyId()}.$KEY_EXTENSION")
+        if (keyFile.exists()) {
+          // Check for replace flag first and if it is false, throw an error
+          if (!replace) throw KeyManagerException.KeyAlreadyExistsException(key.getKeyId())
+          if (!keyFile.delete()) throw KeyManagerException.KeyDeletionFailedException
+        }
+
+        keyFile.writeBytes(key.getPrivateKey())
+
+        key
+      }
+    }
+
+  override suspend fun removeKey(key: GPGKeyPair): Result<GPGKeyPair, Throwable> =
+    withContext(dispatcher) {
+      runCatching {
+        if (!keyDirExists()) throw KeyManagerException.KeyDirectoryUnavailableException
+        val keyFile = File(keyDir, "${key.getKeyId()}.$KEY_EXTENSION")
+        if (keyFile.exists()) {
+          if (!keyFile.delete()) throw KeyManagerException.KeyDeletionFailedException
+        }
+
+        key
+      }
+    }
+
+  override suspend fun getKeyById(id: String): Result<GPGKeyPair, Throwable> =
+    withContext(dispatcher) {
+      runCatching {
+        if (!keyDirExists()) throw KeyManagerException.KeyDirectoryUnavailableException
+        val keys = keyDir.listFiles()
+        if (keys.isNullOrEmpty()) throw KeyManagerException.NoKeysAvailableException
+
+        for (keyFile in keys) {
+          val keyPair = GPGKeyPair(Crypto.newKeyFromArmored(keyFile.readText()))
+          if (keyPair.getKeyId() == id) return@runCatching keyPair
+        }
+
+        throw KeyManagerException.KeyNotFoundException(id)
+      }
+    }
+
+  override suspend fun getAllKeys(): Result<List<GPGKeyPair>, Throwable> =
+    withContext(dispatcher) {
+      runCatching {
+        if (!keyDirExists()) throw KeyManagerException.KeyDirectoryUnavailableException
+        val keys = keyDir.listFiles()
+        if (keys.isNullOrEmpty()) return@runCatching listOf()
+
+        keys.map { GPGKeyPair(Crypto.newKeyFromArmored(it.readText())) }.toList()
+      }
+    }
+
+  override fun canHandle(fileName: String): Boolean {
+    // TODO: This is a temp hack for now and in future it should check that the GPGKeyManager can
+    // decrypt the file
+    return fileName.endsWith(KEY_EXTENSION)
+  }
+
+  private fun keyDirExists(): Boolean {
+    return keyDir.exists() || keyDir.mkdirs()
+  }
+
+  internal companion object {
+
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    internal const val KEY_DIR_NAME: String = "keys"
+    @VisibleForTesting(otherwise = VisibleForTesting.PRIVATE)
+    internal const val KEY_EXTENSION: String = "key"
+  }
+}
diff --git a/crypto-pgp/src/main/kotlin/dev/msfjarvis/aps/data/crypto/GPGKeyPair.kt b/crypto-pgp/src/main/kotlin/dev/msfjarvis/aps/data/crypto/GPGKeyPair.kt
new file mode 100644
index 00000000..2dbe8689
--- /dev/null
+++ b/crypto-pgp/src/main/kotlin/dev/msfjarvis/aps/data/crypto/GPGKeyPair.kt
@@ -0,0 +1,28 @@
+/*
+ * Copyright © 2014-2021 The Android Password Store Authors. All Rights Reserved.
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+package dev.msfjarvis.aps.data.crypto
+
+import com.proton.Gopenpgp.crypto.Key
+
+/** Wraps a Gopenpgp [Key] to implement [KeyPair]. */
+public class GPGKeyPair(private val key: Key) : KeyPair {
+
+  init {
+    if (!key.isPrivate) throw KeyPairException.PrivateKeyUnavailableException
+  }
+
+  override fun getPrivateKey(): ByteArray {
+    return key.armor().encodeToByteArray()
+  }
+
+  override fun getPublicKey(): ByteArray {
+    return key.armoredPublicKey.encodeToByteArray()
+  }
+
+  override fun getKeyId(): String {
+    return key.hexKeyID
+  }
+}