[PM-17424] Implement disk data source for key data

This commit introduces a new disk data source, `KeyDiskSource`, for managing key-related data.
This includes:
- Storing the alias and host of the selected mTLS key.
- Retrieving the alias and host of the selected mTLS key.

A default implementation, `KeyDiskSourceImpl`, is provided using encrypted shared preferences to securely store the key data.
The `PlatformDiskModule` is updated to provide an instance of `KeyDiskSource`.

app/src/main/java/com/x8bit/bitwarden/data/platform/datasource/disk/KeyDiskSource.kt

@@ -0,0 +1,28 @@
+package com.x8bit.bitwarden.data.platform.datasource.disk
+
+import com.x8bit.bitwarden.data.platform.datasource.disk.model.MutualTlsKeyHost
+
+/**
+ * Primary access point for disk information related to key data.
+ */
+interface KeyDiskSource {
+
+    /**
+     * Sets the alias and host of the selected mTLS key.
+     */
+    fun storeMutualTlsKey(
+        userId: String,
+        alias: String?,
+        host: MutualTlsKeyHost?,
+    )
+
+    /**
+     * Alias of the mTLS key if one is selected.
+     */
+    fun getMutualTlsKeyAlias(userId: String): String?
+
+    /**
+     * Host of the mTLS key if one is selected.
+     */
+    fun getMutualTlsKeyHost(userId: String): MutualTlsKeyHost?
+}

app/src/main/java/com/x8bit/bitwarden/data/platform/datasource/disk/KeyDiskSourceImpl.kt

@@ -0,0 +1,37 @@
+package com.x8bit.bitwarden.data.platform.datasource.disk
+
+import android.content.SharedPreferences
+import com.x8bit.bitwarden.data.platform.datasource.disk.model.MutualTlsKeyHost
+
+private const val MUTUAL_TLS_KEY_ALIAS = "mutualTlsKeyAlias"
+private const val MUTUAL_TLS_KEY_HOST = "mutualTlsKeyHost"
+
+/**
+ * Default implementation of [KeyDiskSource].
+ */
+class KeyDiskSourceImpl(
+    encryptedPreferences: SharedPreferences,
+    sharedPreferences: SharedPreferences,
+) : BaseEncryptedDiskSource(
+    sharedPreferences = sharedPreferences,
+    encryptedSharedPreferences = encryptedPreferences,
+), KeyDiskSource {
+
+    override fun storeMutualTlsKey(
+        userId: String,
+        alias: String?,
+        host: MutualTlsKeyHost?,
+    ) {
+        putEncryptedString(
+            key = MUTUAL_TLS_KEY_ALIAS.appendIdentifier(userId),
+            value = alias,
+        )
+    }
+
+    override fun getMutualTlsKeyAlias(userId: String): String? =
+        getEncryptedString(key = MUTUAL_TLS_KEY_ALIAS.appendIdentifier(userId))
+
+    override fun getMutualTlsKeyHost(userId: String): MutualTlsKeyHost? =
+        getEncryptedString(MUTUAL_TLS_KEY_HOST.appendIdentifier(userId))
+            ?.let { MutualTlsKeyHost.valueOf(it) }
+}

app/src/main/java/com/x8bit/bitwarden/data/platform/datasource/disk/di/PlatformDiskModule.kt

@@ -14,6 +14,8 @@ import com.x8bit.bitwarden.data.platform.datasource.disk.EventDiskSource
 import com.x8bit.bitwarden.data.platform.datasource.disk.EventDiskSourceImpl
 import com.x8bit.bitwarden.data.platform.datasource.disk.FeatureFlagOverrideDiskSource
 import com.x8bit.bitwarden.data.platform.datasource.disk.FeatureFlagOverrideDiskSourceImpl
+import com.x8bit.bitwarden.data.platform.datasource.disk.KeyDiskSource
+import com.x8bit.bitwarden.data.platform.datasource.disk.KeyDiskSourceImpl
 import com.x8bit.bitwarden.data.platform.datasource.disk.PushDiskSource
 import com.x8bit.bitwarden.data.platform.datasource.disk.PushDiskSourceImpl
 import com.x8bit.bitwarden.data.platform.datasource.disk.SettingsDiskSource
@@ -165,4 +167,15 @@ object PlatformDiskModule {
     ): FeatureFlagOverrideDiskSource = FeatureFlagOverrideDiskSourceImpl(
         sharedPreferences = sharedPreferences,
     )
+
+    @Provides
+    @Singleton
+    fun provideKeyDiskSource(
+        @UnencryptedPreferences sharedPreferences: SharedPreferences,
+        @EncryptedPreferences encryptedSharedPreferences: SharedPreferences,
+    ): KeyDiskSource =
+        KeyDiskSourceImpl(
+            sharedPreferences = sharedPreferences,
+            encryptedPreferences = encryptedSharedPreferences,
+        )
 }

app/src/main/java/com/x8bit/bitwarden/data/platform/datasource/disk/model/MutualTlsKeyHost.kt

@@ -0,0 +1,16 @@
+package com.x8bit.bitwarden.data.platform.datasource.disk.model
+
+/**
+ * Location of the key data.
+ */
+enum class MutualTlsKeyHost {
+    /**
+     * Key is stored in the system key chain.
+     */
+    KEY_CHAIN,
+
+    /**
+     * Key is stored in a private instance of the Android Key Store.
+     */
+    ANDROID_KEY_STORE,
+}

app/src/test/java/com/x8bit/bitwarden/data/platform/datasource/disk/KeyDiskSourceTest.kt

@@ -0,0 +1,67 @@
+package com.x8bit.bitwarden.data.platform.datasource.disk
+
+import androidx.core.content.edit
+import com.x8bit.bitwarden.data.platform.base.FakeSharedPreferences
+import com.x8bit.bitwarden.data.platform.datasource.disk.model.MutualTlsKeyHost
+import org.junit.jupiter.api.Assertions.assertEquals
+import org.junit.jupiter.api.Assertions.assertNull
+import org.junit.jupiter.api.Test
+
+class KeyDiskSourceTest {
+    private val fakeEncryptedSharedPreferences = FakeSharedPreferences()
+    private val fakeSharedPreferences = FakeSharedPreferences()
+
+    private val keyDiskSource = KeyDiskSourceImpl(
+        sharedPreferences = fakeSharedPreferences,
+        encryptedPreferences = fakeEncryptedSharedPreferences,
+    )
+
+    @Test
+    fun `storeMutualTlsKey should update encrypted SharedPreferences`() {
+        val certificateAliasBaseKey = "bwSecureStorage:mutualTlsKeyAlias"
+        val certificateHostBaseKey = "bwSecureStorage:mutualTlsKeyHost"
+        val mockUserId = "mockUserId"
+        val mockAlias = "mockCertificateAlias"
+        val mockHost = MutualTlsKeyHost.ANDROID_KEY_STORE
+
+        // Verify that the SharedPreferences are initialized empty
+        assertNull(
+            fakeEncryptedSharedPreferences
+                .getString(
+                    "${certificateAliasBaseKey}_$mockUserId",
+                    null,
+                ),
+        )
+        assertNull(
+            fakeEncryptedSharedPreferences
+                .getString(
+                    "${certificateHostBaseKey}_$mockUserId",
+                    null,
+                ),
+        )
+
+        fakeEncryptedSharedPreferences
+            .edit {
+                putString(
+                    "${certificateAliasBaseKey}_$mockUserId",
+                    mockAlias,
+                )
+                putString(
+                    "${certificateHostBaseKey}_$mockUserId",
+                    mockHost.name,
+                )
+            }
+
+        // Verify alias and host are updated in SharedPreferences
+        val alias = keyDiskSource.getMutualTlsKeyAlias(userId = mockUserId)
+        val host = keyDiskSource.getMutualTlsKeyHost(userId = mockUserId)
+        assertEquals(
+            mockAlias,
+            alias,
+        )
+        assertEquals(
+            mockHost,
+            host,
+        )
+    }
+}