Parse APK manifest to extract version etc

Add libapkmanifest to encapsulate the parsing, with a small C++
library on top of libandroidfw.

Extract the zip-handling code from libapkverify into a separate
libapkzip, and fix up a bunch of tests tests, to keep the build happy.

We don't do anything with the manifest information except log it; more
to come in another CL.

Bug: 299591171
Test: atest libapkzip.test libapkverify.integration_test
      libapkverify.test
Test: Manual - run VM, inspect logs.
Change-Id: I56d3bb7309d43ecb598a33320705d31948710f83
diff --git a/libs/apkmanifest/src/apkmanifest.rs b/libs/apkmanifest/src/apkmanifest.rs
new file mode 100644
index 0000000..6766b21
--- /dev/null
+++ b/libs/apkmanifest/src/apkmanifest.rs
@@ -0,0 +1,70 @@
+/*
+ * Copyright 2023 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.
+ */
+
+//! Handle parsing of APK manifest files.
+//! The manifest file is written as XML text, but is stored in the APK
+//! as Android binary compressed XML. This library is a wrapper around
+//! a thin C++ wrapper around libandroidfw, which contains the same
+//! parsing code as used by package manager and aapt2 (amongst other
+//! things).
+
+use anyhow::{bail, Context, Result};
+use apkmanifest_bindgen::{extractManifestInfo, freeManifestInfo, getPackageName, getVersionCode};
+use std::ffi::CStr;
+use std::fs::File;
+use std::path::Path;
+
+/// Information extracted from the Android manifest inside an APK.
+#[derive(Debug)]
+pub struct ApkManifestInfo {
+    /// The package name of the app.
+    pub package: String,
+    /// The version code of the app.
+    pub version_code: u64,
+}
+
+const ANDROID_MANIFEST: &str = "AndroidManifest.xml";
+
+/// Find the manifest inside the given APK and return information from it.
+pub fn get_manifest_info<P: AsRef<Path>>(apk_path: P) -> Result<ApkManifestInfo> {
+    let apk = File::open(apk_path.as_ref())?;
+    let manifest = apkzip::read_file(apk, ANDROID_MANIFEST)?;
+
+    // Safety: The function only reads the memory range we specify and does not hold
+    // any reference to it.
+    let native_info = unsafe { extractManifestInfo(manifest.as_ptr() as _, manifest.len()) };
+    if native_info.is_null() {
+        bail!("Failed to parse manifest")
+    };
+
+    scopeguard::defer! {
+        // Safety: The value we pass is the result of calling extractManifestInfo as required.
+        // We must call this exactly once, after we have finished using it, which the scopeguard
+        // ensures.
+        unsafe { freeManifestInfo(native_info); }
+    }
+
+    // Safety: It is always safe to call this with a valid native_info, which we have,
+    // and it always returns a valid nul-terminated C string with the same lifetime as native_info.
+    // We immediately make a copy.
+    let package = unsafe { CStr::from_ptr(getPackageName(native_info)) };
+    let package = package.to_str().context("Invalid package name")?.to_string();
+
+    // Safety: It is always safe to call this with a valid native_info, which we have.
+    let version_code = unsafe { getVersionCode(native_info) };
+
+    Ok(ApkManifestInfo { package, version_code })
+}