Move WebView relro related functionality to its own file.

WebViewFactory contains a mix of functionality related to preparing and
loading WebView.
This CL breaks out the functionality related to relro-creation and
native library loading into its own class/file to make WebViewFactory
easier to interpret.

Some variables/methods must stay in WebViewFactory since they are
SystemApis.

Bug: 28736099
Test: start WebView-using app, ensure libwebviewchromium64.relro is
loaded into the app process.

Change-Id: I956e1536f23d47f1de1b6c23fc6abeb2768b58ae

1 files changed, 323 insertions, 0 deletions

diff --git a/core/java/android/webkit/WebViewLibraryLoader.java b/core/java/android/webkit/WebViewLibraryLoader.java
new file mode 100644
index 000000000000..e385a4832a0c
--- /dev/null
+++ b/core/java/android/webkit/WebViewLibraryLoader.java
@@ -0,0 +1,323 @@
+/*
+ * Copyright (C) 2017 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.
+ */
+
+package android.webkit;
+
+import android.app.ActivityManagerInternal;
+import android.content.pm.ApplicationInfo;
+import android.content.pm.PackageInfo;
+import android.os.Build;
+import android.os.Process;
+import android.os.RemoteException;
+import android.os.SystemProperties;
+import android.text.TextUtils;
+import android.util.Log;
+
+import com.android.server.LocalServices;
+
+import dalvik.system.VMRuntime;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.zip.ZipEntry;
+import java.util.zip.ZipFile;
+
+class WebViewLibraryLoader {
+    private static final String LOGTAG = WebViewLibraryLoader.class.getSimpleName();
+
+    private static final String CHROMIUM_WEBVIEW_NATIVE_RELRO_32 =
+            "/data/misc/shared_relro/libwebviewchromium32.relro";
+    private static final String CHROMIUM_WEBVIEW_NATIVE_RELRO_64 =
+            "/data/misc/shared_relro/libwebviewchromium64.relro";
+    private static final long CHROMIUM_WEBVIEW_DEFAULT_VMSIZE_BYTES = 100 * 1024 * 1024;
+
+    private static final boolean DEBUG = false;
+
+    private static boolean sAddressSpaceReserved = false;
+
+    /**
+     * Private class for running the actual relro creation in an unprivileged child process.
+     * RelroFileCreator is a static class (without access to the outer class) to avoid accidentally
+     * using any static members from the outer class. Those members will in reality differ between
+     * the child process in which RelroFileCreator operates, and the app process in which the static
+     * members of this class are used.
+     */
+    private static class RelroFileCreator {
+        // Called in an unprivileged child process to create the relro file.
+        public static void main(String[] args) {
+            boolean result = false;
+            boolean is64Bit = VMRuntime.getRuntime().is64Bit();
+            try {
+                if (args.length != 2 || args[0] == null || args[1] == null) {
+                    Log.e(LOGTAG, "Invalid RelroFileCreator args: " + Arrays.toString(args));
+                    return;
+                }
+                Log.v(LOGTAG, "RelroFileCreator (64bit = " + is64Bit + "), "
+                        + " 32-bit lib: " + args[0] + ", 64-bit lib: " + args[1]);
+                if (!sAddressSpaceReserved) {
+                    Log.e(LOGTAG, "can't create relro file; address space not reserved");
+                    return;
+                }
+                result = nativeCreateRelroFile(args[0] /* path32 */,
+                                               args[1] /* path64 */,
+                                               CHROMIUM_WEBVIEW_NATIVE_RELRO_32,
+                                               CHROMIUM_WEBVIEW_NATIVE_RELRO_64);
+                if (result && DEBUG) Log.v(LOGTAG, "created relro file");
+            } finally {
+                // We must do our best to always notify the update service, even if something fails.
+                try {
+                    WebViewFactory.getUpdateService().notifyRelroCreationCompleted();
+                } catch (RemoteException e) {
+                    Log.e(LOGTAG, "error notifying update service", e);
+                }
+
+                if (!result) Log.e(LOGTAG, "failed to create relro file");
+
+                // Must explicitly exit or else this process will just sit around after we return.
+                System.exit(0);
+            }
+        }
+    }
+
+    /**
+     * Create a single relro file by invoking an isolated process that to do the actual work.
+     */
+    static void createRelroFile(final boolean is64Bit, String[] nativeLibraryPaths) {
+        final String abi =
+                is64Bit ? Build.SUPPORTED_64_BIT_ABIS[0] : Build.SUPPORTED_32_BIT_ABIS[0];
+
+        // crashHandler is invoked by the ActivityManagerService when the isolated process crashes.
+        Runnable crashHandler = new Runnable() {
+            @Override
+            public void run() {
+                try {
+                    Log.e(LOGTAG, "relro file creator for " + abi + " crashed. Proceeding without");
+                    WebViewFactory.getUpdateService().notifyRelroCreationCompleted();
+                } catch (RemoteException e) {
+                    Log.e(LOGTAG, "Cannot reach WebViewUpdateService. " + e.getMessage());
+                }
+            }
+        };
+
+        try {
+            if (nativeLibraryPaths == null
+                    || nativeLibraryPaths[0] == null || nativeLibraryPaths[1] == null) {
+                throw new IllegalArgumentException(
+                        "Native library paths to the WebView RelRo process must not be null!");
+            }
+            int pid = LocalServices.getService(ActivityManagerInternal.class).startIsolatedProcess(
+                    RelroFileCreator.class.getName(), nativeLibraryPaths,
+                    "WebViewLoader-" + abi, abi, Process.SHARED_RELRO_UID, crashHandler);
+            if (pid <= 0) throw new Exception("Failed to start the relro file creator process");
+        } catch (Throwable t) {
+            // Log and discard errors as we must not crash the system server.
+            Log.e(LOGTAG, "error starting relro file creator for abi " + abi, t);
+            crashHandler.run();
+        }
+    }
+
+    /**
+     *
+     * @return the native WebView libraries in the new WebView APK.
+     */
+    static String[] updateWebViewZygoteVmSize(PackageInfo packageInfo)
+            throws WebViewFactory.MissingWebViewPackageException {
+        // Find the native libraries of the new WebView package, to change the size of the
+        // memory region in the Zygote reserved for the library.
+        String[] nativeLibs = getWebViewNativeLibraryPaths(packageInfo);
+        if (nativeLibs != null) {
+            long newVmSize = 0L;
+
+            for (String path : nativeLibs) {
+                if (path == null || TextUtils.isEmpty(path)) continue;
+                if (DEBUG) Log.d(LOGTAG, "Checking file size of " + path);
+                File f = new File(path);
+                if (f.exists()) {
+                    newVmSize = Math.max(newVmSize, f.length());
+                    continue;
+                }
+                if (path.contains("!/")) {
+                    String[] split = TextUtils.split(path, "!/");
+                    if (split.length == 2) {
+                        try (ZipFile z = new ZipFile(split[0])) {
+                            ZipEntry e = z.getEntry(split[1]);
+                            if (e != null && e.getMethod() == ZipEntry.STORED) {
+                                newVmSize = Math.max(newVmSize, e.getSize());
+                                continue;
+                            }
+                        }
+                        catch (IOException e) {
+                            Log.e(LOGTAG, "error reading APK file " + split[0] + ", ", e);
+                        }
+                    }
+                }
+                Log.e(LOGTAG, "error sizing load for " + path);
+            }
+
+            if (DEBUG) {
+                Log.v(LOGTAG, "Based on library size, need " + newVmSize
+                        + " bytes of address space.");
+            }
+            // The required memory can be larger than the file on disk (due to .bss), and an
+            // upgraded version of the library will likely be larger, so always attempt to
+            // reserve twice as much as we think to allow for the library to grow during this
+            // boot cycle.
+            newVmSize = Math.max(2 * newVmSize, CHROMIUM_WEBVIEW_DEFAULT_VMSIZE_BYTES);
+            Log.d(LOGTAG, "Setting new address space to " + newVmSize);
+            setWebViewZygoteVmSize(newVmSize);
+        }
+        return nativeLibs;
+    }
+
+    /**
+     * Reserve space for the native library to be loaded into.
+     */
+    static void reserveAddressSpaceInZygote() {
+        System.loadLibrary("webviewchromium_loader");
+        long addressSpaceToReserve =
+                SystemProperties.getLong(WebViewFactory.CHROMIUM_WEBVIEW_VMSIZE_SIZE_PROPERTY,
+                CHROMIUM_WEBVIEW_DEFAULT_VMSIZE_BYTES);
+        sAddressSpaceReserved = nativeReserveAddressSpace(addressSpaceToReserve);
+
+        if (sAddressSpaceReserved) {
+            if (DEBUG) {
+                Log.v(LOGTAG, "address space reserved: " + addressSpaceToReserve + " bytes");
+            }
+        } else {
+            Log.e(LOGTAG, "reserving " + addressSpaceToReserve + " bytes of address space failed");
+        }
+    }
+
+    /**
+     * Load WebView's native library into the current process.
+     * Note: assumes that we have waited for relro creation.
+     * @param clazzLoader class loader used to find the linker namespace to load the library into.
+     * @param packageInfo the package from which WebView is loaded.
+     */
+    static int loadNativeLibrary(ClassLoader clazzLoader, PackageInfo packageInfo)
+            throws WebViewFactory.MissingWebViewPackageException {
+        if (!sAddressSpaceReserved) {
+            Log.e(LOGTAG, "can't load with relro file; address space not reserved");
+            return WebViewFactory.LIBLOAD_ADDRESS_SPACE_NOT_RESERVED;
+        }
+
+        String[] args = getWebViewNativeLibraryPaths(packageInfo);
+        int result = nativeLoadWithRelroFile(args[0] /* path32 */,
+                                             args[1] /* path64 */,
+                                             CHROMIUM_WEBVIEW_NATIVE_RELRO_32,
+                                             CHROMIUM_WEBVIEW_NATIVE_RELRO_64,
+                                             clazzLoader);
+        if (result != WebViewFactory.LIBLOAD_SUCCESS) {
+            Log.w(LOGTAG, "failed to load with relro file, proceeding without");
+        } else if (DEBUG) {
+            Log.v(LOGTAG, "loaded with relro file");
+        }
+        return result;
+    }
+
+    /**
+     * Fetch WebView's native library paths from {@param packageInfo}.
+     */
+    static String[] getWebViewNativeLibraryPaths(PackageInfo packageInfo)
+            throws WebViewFactory.MissingWebViewPackageException {
+        ApplicationInfo ai = packageInfo.applicationInfo;
+        final String nativeLibFileName = WebViewFactory.getWebViewLibrary(ai);
+
+        String path32;
+        String path64;
+        boolean primaryArchIs64bit = VMRuntime.is64BitAbi(ai.primaryCpuAbi);
+        if (!TextUtils.isEmpty(ai.secondaryCpuAbi)) {
+            // Multi-arch case.
+            if (primaryArchIs64bit) {
+                // Primary arch: 64-bit, secondary: 32-bit.
+                path64 = ai.nativeLibraryDir;
+                path32 = ai.secondaryNativeLibraryDir;
+            } else {
+                // Primary arch: 32-bit, secondary: 64-bit.
+                path64 = ai.secondaryNativeLibraryDir;
+                path32 = ai.nativeLibraryDir;
+            }
+        } else if (primaryArchIs64bit) {
+            // Single-arch 64-bit.
+            path64 = ai.nativeLibraryDir;
+            path32 = "";
+        } else {
+            // Single-arch 32-bit.
+            path32 = ai.nativeLibraryDir;
+            path64 = "";
+        }
+
+        // Form the full paths to the extracted native libraries.
+        // If libraries were not extracted, try load from APK paths instead.
+        if (!TextUtils.isEmpty(path32)) {
+            path32 += "/" + nativeLibFileName;
+            File f = new File(path32);
+            if (!f.exists()) {
+                path32 = getLoadFromApkPath(ai.sourceDir,
+                                            Build.SUPPORTED_32_BIT_ABIS,
+                                            nativeLibFileName);
+            }
+        }
+        if (!TextUtils.isEmpty(path64)) {
+            path64 += "/" + nativeLibFileName;
+            File f = new File(path64);
+            if (!f.exists()) {
+                path64 = getLoadFromApkPath(ai.sourceDir,
+                                            Build.SUPPORTED_64_BIT_ABIS,
+                                            nativeLibFileName);
+            }
+        }
+
+        if (DEBUG) Log.v(LOGTAG, "Native 32-bit lib: " + path32 + ", 64-bit lib: " + path64);
+        return new String[] { path32, path64 };
+    }
+
+    private static String getLoadFromApkPath(String apkPath,
+                                             String[] abiList,
+                                             String nativeLibFileName)
+            throws WebViewFactory.MissingWebViewPackageException {
+        // Search the APK for a native library conforming to a listed ABI.
+        try (ZipFile z = new ZipFile(apkPath)) {
+            for (String abi : abiList) {
+                final String entry = "lib/" + abi + "/" + nativeLibFileName;
+                ZipEntry e = z.getEntry(entry);
+                if (e != null && e.getMethod() == ZipEntry.STORED) {
+                    // Return a path formatted for dlopen() load from APK.
+                    return apkPath + "!/" + entry;
+                }
+            }
+        } catch (IOException e) {
+            throw new WebViewFactory.MissingWebViewPackageException(e);
+        }
+        return "";
+    }
+
+    /**
+     * Sets the size of the memory area in which to store the relro section.
+     */
+    private static void setWebViewZygoteVmSize(long vmSize) {
+        SystemProperties.set(WebViewFactory.CHROMIUM_WEBVIEW_VMSIZE_SIZE_PROPERTY,
+                Long.toString(vmSize));
+    }
+
+    static native boolean nativeReserveAddressSpace(long addressSpaceToReserve);
+    static native boolean nativeCreateRelroFile(String lib32, String lib64,
+                                                        String relro32, String relro64);
+    static native int nativeLoadWithRelroFile(String lib32, String lib64,
+                                                      String relro32, String relro64,
+                                                      ClassLoader clazzLoader);
+}