Add tests for Rust VM Payload

Make sure we exercise the Rust wrapper by having a test payload using
it.

API tweaks in the process:
- Add a module for restricted functions to make them more obvious.
- Remove a bogus generic parameter.

Test tweaks in the process:
- Test retrieving VM secrets in more places, it's not a restricted
  operation unlike CDIs etc.

Note that attestation-related APIs are exercised by
VmAttestationTestApp, so aren't covered here.

Bug: 340857915
Test: atest MicrodroidTests
Change-Id: I8f4166ffea5db17381875c83119c592d6be48296
diff --git a/tests/testapk/src/native/testbinary.rs b/tests/testapk/src/native/testbinary.rs
new file mode 100644
index 0000000..85b411e
--- /dev/null
+++ b/tests/testapk/src/native/testbinary.rs
@@ -0,0 +1,138 @@
+/*
+ * Copyright 2024 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+//! A VM payload that exists to allow testing of the Rust wrapper for the VM payload APIs.
+
+use anyhow::Result;
+use com_android_microdroid_testservice::{
+    aidl::com::android::microdroid::testservice::{
+        IAppCallback::IAppCallback,
+        ITestService::{BnTestService, ITestService, PORT},
+    },
+    binder::{BinderFeatures, ExceptionCode, Interface, Result as BinderResult, Status, Strong},
+};
+use cstr::cstr;
+use log::{error, info};
+use std::panic;
+use std::process::exit;
+use std::string::String;
+use std::vec::Vec;
+
+vm_payload::main!(main);
+
+// Entry point of the Service VM client.
+fn main() {
+    android_logger::init_once(
+        android_logger::Config::default()
+            .with_tag("microdroid_testlib_rust")
+            .with_max_level(log::LevelFilter::Debug),
+    );
+    // Redirect panic messages to logcat.
+    panic::set_hook(Box::new(|panic_info| {
+        error!("{panic_info}");
+    }));
+    if let Err(e) = try_main() {
+        error!("failed with {:?}", e);
+        exit(1);
+    }
+}
+
+fn try_main() -> Result<()> {
+    info!("Welcome to the Rust test binary");
+
+    vm_payload::run_single_vsock_service(TestService::new_binder(), PORT.try_into()?)
+}
+
+struct TestService {}
+
+impl Interface for TestService {}
+
+impl TestService {
+    fn new_binder() -> Strong<dyn ITestService> {
+        BnTestService::new_binder(TestService {}, BinderFeatures::default())
+    }
+}
+
+impl ITestService for TestService {
+    fn quit(&self) -> BinderResult<()> {
+        exit(0)
+    }
+
+    fn addInteger(&self, a: i32, b: i32) -> BinderResult<i32> {
+        a.checked_add(b).ok_or_else(|| Status::new_exception(ExceptionCode::ILLEGAL_ARGUMENT, None))
+    }
+
+    fn getApkContentsPath(&self) -> BinderResult<String> {
+        Ok(vm_payload::apk_contents_path().to_string_lossy().to_string())
+    }
+
+    fn getEncryptedStoragePath(&self) -> BinderResult<String> {
+        Ok(vm_payload::encrypted_storage_path()
+            .map(|p| p.to_string_lossy().to_string())
+            .unwrap_or("".to_string()))
+    }
+
+    fn insecurelyExposeVmInstanceSecret(&self) -> BinderResult<Vec<u8>> {
+        let mut secret = vec![0u8; 32];
+        vm_payload::get_vm_instance_secret(b"identifier", secret.as_mut_slice());
+        Ok(secret)
+    }
+
+    // Everything below here is unimplemented. Implementations may be added as needed.
+
+    fn readProperty(&self, _: &str) -> BinderResult<String> {
+        unimplemented()
+    }
+    fn insecurelyExposeAttestationCdi(&self) -> BinderResult<Vec<u8>> {
+        unimplemented()
+    }
+    fn getBcc(&self) -> BinderResult<Vec<u8>> {
+        unimplemented()
+    }
+    fn runEchoReverseServer(&self) -> BinderResult<()> {
+        unimplemented()
+    }
+    fn getEffectiveCapabilities(&self) -> BinderResult<Vec<String>> {
+        unimplemented()
+    }
+    fn getUid(&self) -> BinderResult<i32> {
+        unimplemented()
+    }
+    fn writeToFile(&self, _: &str, _: &str) -> BinderResult<()> {
+        unimplemented()
+    }
+    fn readFromFile(&self, _: &str) -> BinderResult<String> {
+        unimplemented()
+    }
+    fn getFilePermissions(&self, _: &str) -> BinderResult<i32> {
+        unimplemented()
+    }
+    fn getMountFlags(&self, _: &str) -> BinderResult<i32> {
+        unimplemented()
+    }
+    fn requestCallback(&self, _: &Strong<dyn IAppCallback + 'static>) -> BinderResult<()> {
+        unimplemented()
+    }
+    fn readLineFromConsole(&self) -> BinderResult<String> {
+        unimplemented()
+    }
+}
+
+fn unimplemented<T>() -> BinderResult<T> {
+    let message = cstr!("Got a call to an unimplemented ITestService method in testbinary.rs");
+    error!("{message:?}");
+    Err(Status::new_exception(ExceptionCode::UNSUPPORTED_OPERATION, Some(message)))
+}