Implement Android Credential Manager and Autofill providers (#109)

android/provider-client/src/main/AndroidManifest.xml

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+<manifest xmlns:android="http://schemas.android.com/apk/res/android" xmlns:tools="http://schemas.android.com/tools">
+    <!-- This password-only fixture invokes Credential Manager on API 34+ and declares no website association. -->
+    <application android:allowBackup="false" android:fullBackupContent="@xml/backup_rules"
+        android:dataExtractionRules="@xml/data_extraction_rules" android:icon="@android:drawable/ic_lock_lock" android:label="Credential provider fixture"
+        android:theme="@android:style/Theme.Material.Light.NoActionBar"
+        android:usesCleartextTraffic="false" tools:ignore="CredentialDependency,CredManMissingDal">
+        <activity android:name=".ProviderClientActivity" android:exported="true">
+            <intent-filter><action android:name="android.intent.action.MAIN" /><category android:name="android.intent.category.LAUNCHER" /></intent-filter>
+        </activity>
+        <provider android:name=".BrowserFixtureProvider"
+            android:authorities="de.rfc1437.ironstorage.providerclient.fixture"
+            android:exported="false" android:grantUriPermissions="true" />
+    </application>
+</manifest>

android/provider-client/src/main/assets/provider_form.html

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+<!doctype html>
+<html lang="en"><meta name="viewport" content="width=device-width, initial-scale=1">
+<title>IronStorage browser fixture</title>
+<style>body{font:20px sans-serif;padding:24px}input,button{display:block;font:inherit;margin:16px 0;padding:12px;max-width:100%;box-sizing:border-box}</style>
+<h1>Browser credential fixture</h1>
+<p>This local page uses public synthetic credentials. It sends no network requests.</p>
+<form autocomplete="on" onsubmit="return false">
+<label for="username">Username</label>
+<input id="username" name="username" type="text" autocomplete="username">
+<label for="password">Password</label>
+<input id="password" name="password" type="password" autocomplete="current-password">
+<button type="button" onclick="document.getElementById('status').textContent=document.getElementById('username').value==='fixture-alice'&&document.getElementById('password').value==='public-provider-fixture-password'?'Chrome received the expected synthetic credential':'The fixture has not been filled'">Verify filled fixture</button>
+</form><p id="status">Waiting for an explicit fill.</p>
+</html>

android/provider-client/src/main/kotlin/de/rfc1437/ironstorage/providerclient/BrowserFixtureProvider.kt

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+package de.rfc1437.ironstorage.providerclient
+
+import android.content.ContentProvider
+import android.content.ContentValues
+import android.content.res.AssetFileDescriptor
+import android.database.Cursor
+import android.database.MatrixCursor
+import android.net.Uri
+import android.os.ParcelFileDescriptor
+import android.provider.OpenableColumns
+import java.io.File
+
+/** A single public, read-only fixture asset; there is no application-data access. */
+class BrowserFixtureProvider : ContentProvider() {
+    private lateinit var page: File
+    override fun onCreate(): Boolean {
+        val app = requireNotNull(context)
+        page = File(app.cacheDir, "public_provider_form.html")
+        app.assets.open("provider_form.html").use { source ->
+            page.outputStream().use { target -> source.copyTo(target) }
+        }
+        return true
+    }
+    private fun checkPage(uri: Uri) {
+        require(uri.path == "/credential_form.html")
+    }
+    override fun getType(uri: Uri): String {
+        checkPage(uri)
+        return "text/html"
+    }
+    override fun query(
+        uri: Uri,
+        projection: Array<out String>?,
+        selection: String?,
+        selectionArgs: Array<out String>?,
+        sortOrder: String?
+    ): Cursor {
+        checkPage(uri)
+        return MatrixCursor(arrayOf(OpenableColumns.DISPLAY_NAME, OpenableColumns.SIZE)).apply {
+            addRow(
+                arrayOf<Any>(
+                    "credential_form.html",
+                    page.length()
+                )
+            )
+        }
+    }
+    override fun openAssetFile(uri: Uri, mode: String): AssetFileDescriptor {
+        checkPage(uri)
+        require(mode == "r")
+        return AssetFileDescriptor(openFile(uri, mode), 0, page.length())
+    }
+    override fun openFile(uri: Uri, mode: String): ParcelFileDescriptor {
+        checkPage(uri)
+        require(mode == "r")
+        return ParcelFileDescriptor.open(page, ParcelFileDescriptor.MODE_READ_ONLY)
+    }
+    override fun insert(uri: Uri, values: ContentValues?): Uri =
+        throw UnsupportedOperationException("Read-only fixture")
+    override fun delete(uri: Uri, selection: String?, selectionArgs: Array<out String>?): Int =
+        throw UnsupportedOperationException("Read-only fixture")
+    override fun update(
+        uri: Uri,
+        values: ContentValues?,
+        selection: String?,
+        selectionArgs: Array<out String>?
+    ): Int = throw UnsupportedOperationException("Read-only fixture")
+}

android/provider-client/src/main/kotlin/de/rfc1437/ironstorage/providerclient/ProviderClientActivity.kt

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+package de.rfc1437.ironstorage.providerclient
+
+import android.annotation.SuppressLint
+import android.content.Intent
+import android.os.Build
+import android.os.Bundle
+import android.text.InputType
+import android.view.View
+import android.view.autofill.AutofillManager
+import android.widget.Button
+import android.widget.EditText
+import android.widget.LinearLayout
+import android.widget.TextView
+import androidx.core.net.toUri
+import androidx.credentials.CreatePasswordRequest
+import androidx.credentials.CredentialManager
+import androidx.credentials.GetCredentialRequest
+import androidx.credentials.GetPasswordOption
+import androidx.credentials.PasswordCredential
+import androidx.credentials.exceptions.NoCredentialException
+import androidx.fragment.app.FragmentActivity
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.cancel
+import kotlinx.coroutines.launch
+
+/** A separate test APK represents an ordinary requesting application. Secrets are synthetic. */
+@SuppressLint("SetTextI18n")
+class ProviderClientActivity : FragmentActivity() {
+    private val scope = CoroutineScope(SupervisorJob() + Dispatchers.Main.immediate)
+    override fun onCreate(savedInstanceState: Bundle?) {
+        super.onCreate(savedInstanceState)
+        val form = LinearLayout(this).apply {
+            orientation = LinearLayout.VERTICAL
+            setPadding(32, 60, 32, 32)
+        }
+        val status = TextView(this).apply { text = "Provider client: synthetic credentials only" }
+        val username = EditText(this).apply {
+            id = View.generateViewId()
+            hint = "Username"
+            inputType = InputType.TYPE_CLASS_TEXT
+            setAutofillHints(View.AUTOFILL_HINT_USERNAME)
+        }
+        val password = EditText(this).apply {
+            id = View.generateViewId()
+            hint = "Password"
+            inputType = InputType.TYPE_CLASS_TEXT or InputType.TYPE_TEXT_VARIATION_PASSWORD
+            setAutofillHints(View.AUTOFILL_HINT_PASSWORD)
+        }
+        form.addView(status)
+        form.addView(username)
+        form.addView(password)
+        fun button(title: String, action: () -> Unit) {
+            form.addView(
+                Button(this).apply {
+                    text =
+                        title
+                    setOnClickListener { action() }
+                }
+            )
+        }
+        button("Open local Chrome fixture") {
+            val uri = "content://$packageName.fixture/credential_form.html".toUri()
+            startActivity(
+                Intent(
+                    Intent.ACTION_VIEW
+                ).setDataAndType(
+                    uri,
+                    "text/html"
+                ).setPackage("com.android.chrome").addFlags(Intent.FLAG_GRANT_READ_URI_PERMISSION)
+            )
+        }
+        button("Request Autofill") {
+            val manager = getSystemService(AutofillManager::class.java)
+            manager.cancel()
+            username.text.clear()
+            password.text.clear()
+            manager.requestAutofill(username)
+        }
+        button("Open loopback Chrome fixture") {
+            startActivity(
+                Intent(Intent.ACTION_VIEW, "http://localhost:8765/provider_form.html".toUri())
+                    .setPackage("com.android.chrome")
+            )
+        }
+        button("Verify filled form") {
+            status.text =
+                if (username.text.toString() == "fixture-alice" &&
+                    password.text.toString() == "public-provider-fixture-password"
+                ) {
+                    "Autofill returned the expected synthetic credential"
+                } else {
+                    "Autofill has not returned the expected fixture"
+                }
+        }
+        button("Request Credential Manager") {
+            if (Build.VERSION.SDK_INT <
+                34
+            ) {
+                status.text = "Credential Manager provider requires API 34"
+                return@button
+            }
+            scope.launch {
+                try {
+                    val response = CredentialManager.create(
+                        this@ProviderClientActivity
+                    ).getCredential(
+                        this@ProviderClientActivity,
+                        GetCredentialRequest(listOf(GetPasswordOption()))
+                    )
+                    val value = response.credential as PasswordCredential
+                    status.text =
+                        if (value.id == "fixture-alice" &&
+                            value.password == "public-provider-fixture-password"
+                        ) {
+                            "Credential Manager returned the expected synthetic credential"
+                        } else {
+                            "Credential Manager returned an unexpected fixture"
+                        }
+                } catch (_: NoCredentialException) {
+                    status.text = "No enabled provider offered a password credential"
+                } catch (_: Exception) {
+                    status.text =
+                        "Credential Manager request cancelled or rejected"
+                }
+            }
+        }
+        button("Commit form for save offer") {
+            getSystemService(AutofillManager::class.java).commit()
+        }
+        button("Populate synthetic save fields") {
+            username.setText("fixture-bob")
+            password.setText("public-provider-new-password")
+        }
+        button("Request Credential Manager save") {
+            if (Build.VERSION.SDK_INT < 34) {
+                status.text = "Credential Manager provider requires API 34"
+                return@button
+            }
+            scope.launch {
+                try {
+                    CredentialManager.create(
+                        this@ProviderClientActivity
+                    ).createCredential(
+                        this@ProviderClientActivity,
+                        CreatePasswordRequest("fixture-bob", "public-provider-new-password")
+                    )
+                    status.text = "Credential Manager save confirmed"
+                } catch (_: Exception) {
+                    status.text =
+                        "Credential Manager save cancelled or rejected"
+                }
+            }
+        }
+        setContentView(form)
+    }
+    override fun onDestroy() {
+        scope.cancel()
+        super.onDestroy()
+    }
+}

android/provider-client/src/main/res/xml/backup_rules.xml

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+<full-backup-content>
+    <exclude domain="root" path="." />
+    <exclude domain="file" path="." />
+    <exclude domain="database" path="." />
+    <exclude domain="sharedpref" path="." />
+    <exclude domain="external" path="." />
+    <exclude domain="device_root" path="." />
+    <exclude domain="device_file" path="." />
+    <exclude domain="device_database" path="." />
+    <exclude domain="device_sharedpref" path="." />
+</full-backup-content>

android/provider-client/src/main/res/xml/data_extraction_rules.xml

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+<data-extraction-rules>
+    <cloud-backup>
+        <exclude domain="root" path="." />
+        <exclude domain="file" path="." />
+        <exclude domain="database" path="." />
+        <exclude domain="sharedpref" path="." />
+        <exclude domain="external" path="." />
+        <exclude domain="device_root" path="." />
+        <exclude domain="device_file" path="." />
+        <exclude domain="device_database" path="." />
+        <exclude domain="device_sharedpref" path="." />
+    </cloud-backup>
+    <device-transfer>
+        <exclude domain="root" path="." />
+        <exclude domain="file" path="." />
+        <exclude domain="database" path="." />
+        <exclude domain="sharedpref" path="." />
+        <exclude domain="external" path="." />
+        <exclude domain="device_root" path="." />
+        <exclude domain="device_file" path="." />
+        <exclude domain="device_database" path="." />
+        <exclude domain="device_sharedpref" path="." />
+    </device-transfer>
+</data-extraction-rules>