/*
 * 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.annotation.NonNull;
import android.annotation.Nullable;
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.internal.annotations.VisibleForTesting;
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;

@hide
/**
 * @hide
 */
@VisibleForTesting
public 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 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 != 1 || args[0] == null) {
                    Log.e(LOGTAG, "Invalid RelroFileCreator args: " + Arrays.toString(args));
                    return;
                }
                Log.v(LOGTAG, "RelroFileCreator (64bit = " + is64Bit + "), lib: " + args[0]);
                if (!sAddressSpaceReserved) {
                    Log.e(LOGTAG, "can't create relro file; address space not reserved");
                    return;
                }
                result = nativeCreateRelroFile(args[0] /* path */,
                                               is64Bit ? CHROMIUM_WEBVIEW_NATIVE_RELRO_64 :
                                                         CHROMIUM_WEBVIEW_NATIVE_RELRO_32);
                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.getUpdateServiceUnchecked().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.
/**
     * Create a single relro file by invoking an isolated process that to do the actual work.
     */
    static void createRelroFile(final boolean is64Bit, @NonNull WebViewNativeLibrary nativeLib) {
        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 (nativeLib == null || nativeLib.path == null) {
                throw new IllegalArgumentException(
                        "Native library paths to the WebView RelRo process must not be null!");
            }
            boolean success = LocalServices.getService(ActivityManagerInternal.class)
                    .startIsolatedProcess(
                            RelroFileCreator.class.getName(), new String[] { nativeLib.path },
                            "WebViewLoader-" + abi, abi, Process.SHARED_RELRO_UID, crashHandler);
            if (!success) 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();
        }
    }

    
Perform preparations needed to allow loading WebView from an application. This method should
be called whenever we change WebView provider.
Returns:
the number of relro processes started./**
     * Perform preparations needed to allow loading WebView from an application. This method should
     * be called whenever we change WebView provider.
     * @return the number of relro processes started.
     */
    static int prepareNativeLibraries(PackageInfo webviewPackageInfo)
            throws WebViewFactory.MissingWebViewPackageException {
        WebViewNativeLibrary nativeLib32bit =
                getWebViewNativeLibrary(webviewPackageInfo, false /* is64bit */);
        WebViewNativeLibrary nativeLib64bit =
                getWebViewNativeLibrary(webviewPackageInfo, true /* is64bit */);
        updateWebViewZygoteVmSize(nativeLib32bit, nativeLib64bit);

        return createRelros(nativeLib32bit, nativeLib64bit);
    }

    
Returns:
the number of relro processes started./**
     * @return the number of relro processes started.
     */
    private static int createRelros(@Nullable WebViewNativeLibrary nativeLib32bit,
            @Nullable WebViewNativeLibrary nativeLib64bit) {
        if (DEBUG) Log.v(LOGTAG, "creating relro files");
        int numRelros = 0;

        if (Build.SUPPORTED_32_BIT_ABIS.length > 0) {
            if (nativeLib32bit == null) {
                Log.e(LOGTAG, "No 32-bit WebView library path, skipping relro creation.");
            } else {
                if (DEBUG) Log.v(LOGTAG, "Create 32 bit relro");
                createRelroFile(false /* is64Bit */, nativeLib32bit);
                numRelros++;
            }
        }

        if (Build.SUPPORTED_64_BIT_ABIS.length > 0) {
            if (nativeLib64bit == null) {
                Log.e(LOGTAG, "No 64-bit WebView library path, skipping relro creation.");
            } else {
                if (DEBUG) Log.v(LOGTAG, "Create 64 bit relro");
                createRelroFile(true /* is64Bit */, nativeLib64bit);
                numRelros++;
            }
        }
        return numRelros;
    }

    
Returns:
the native WebView libraries in the new WebView APK./**
     *
     * @return the native WebView libraries in the new WebView APK.
     */
    private static void updateWebViewZygoteVmSize(
            @Nullable WebViewNativeLibrary nativeLib32bit,
            @Nullable WebViewNativeLibrary nativeLib64bit)
            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.
        long newVmSize = 0L;

        if (nativeLib32bit != null) newVmSize = Math.max(newVmSize, nativeLib32bit.size);
        if (nativeLib64bit != null) newVmSize = Math.max(newVmSize, nativeLib64bit.size);

        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);
    }

    
Reserve space for the native library to be loaded into.
/**
     * 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.
Params:
clazzLoader – class loader used to find the linker namespace to load the library into.
libraryFileName – the filename of the library to load./**
     * Load WebView's native library into the current process.
     *
     * <p class="note"><b>Note:</b> Assumes that we have waited for relro creation.
     *
     * @param clazzLoader class loader used to find the linker namespace to load the library into.
     * @param libraryFileName the filename of the library to load.
     */
    public static int loadNativeLibrary(ClassLoader clazzLoader, String libraryFileName) {
        if (!sAddressSpaceReserved) {
            Log.e(LOGTAG, "can't load with relro file; address space not reserved");
            return WebViewFactory.LIBLOAD_ADDRESS_SPACE_NOT_RESERVED;
        }

        String relroPath = VMRuntime.getRuntime().is64Bit() ? CHROMIUM_WEBVIEW_NATIVE_RELRO_64 :
                                                              CHROMIUM_WEBVIEW_NATIVE_RELRO_32;
        int result = nativeLoadWithRelroFile(libraryFileName, relroPath, 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}.
@hide
/**
     * Fetch WebView's native library paths from {@param packageInfo}.
     * @hide
     */
    @Nullable
    @VisibleForTesting
    public static WebViewNativeLibrary getWebViewNativeLibrary(PackageInfo packageInfo,
            boolean is64bit) throws WebViewFactory.MissingWebViewPackageException {
        ApplicationInfo ai = packageInfo.applicationInfo;
        final String nativeLibFileName = WebViewFactory.getWebViewLibrary(ai);

        String dir = getWebViewNativeLibraryDirectory(ai, is64bit /* 64bit */);

        WebViewNativeLibrary lib = findNativeLibrary(ai, nativeLibFileName,
                is64bit ? Build.SUPPORTED_64_BIT_ABIS : Build.SUPPORTED_32_BIT_ABIS, dir);

        if (DEBUG) {
            Log.v(LOGTAG, String.format("Native %d-bit lib: %s", is64bit ? 64 : 32, lib.path));
        }
        return lib;
    }

    
Returns:
the directory of the native WebView library with bitness {@param is64bit}.
@hide
/**
     * @return the directory of the native WebView library with bitness {@param is64bit}.
     * @hide
     */
    @VisibleForTesting
    public static String getWebViewNativeLibraryDirectory(ApplicationInfo ai, boolean is64bit) {
        // Primary arch has the same bitness as the library we are looking for.
        if (is64bit == VMRuntime.is64BitAbi(ai.primaryCpuAbi)) return ai.nativeLibraryDir;

        // Secondary arch has the same bitness as the library we are looking for.
        if (!TextUtils.isEmpty(ai.secondaryCpuAbi)) {
            return ai.secondaryNativeLibraryDir;
        }

        return "";
    }

    
Returns:
an object describing a native WebView library given the directory path of that
library, or null if the library couldn't be found./**
     * @return an object describing a native WebView library given the directory path of that
     * library, or null if the library couldn't be found.
     */
    @Nullable
    private static WebViewNativeLibrary findNativeLibrary(ApplicationInfo ai,
            String nativeLibFileName, String[] abiList, String libDirectory)
            throws WebViewFactory.MissingWebViewPackageException {
        if (TextUtils.isEmpty(libDirectory)) return null;
        String libPath = libDirectory + "/" + nativeLibFileName;
        File f = new File(libPath);
        if (f.exists()) {
            return new WebViewNativeLibrary(libPath, f.length());
        } else {
            return getLoadFromApkPath(ai.sourceDir, abiList, nativeLibFileName);
        }
    }

    
@hide
/**
     * @hide
     */
    @VisibleForTesting
    public static class WebViewNativeLibrary {
        public final String path;
        public final long size;

        WebViewNativeLibrary(String path, long size) {
            this.path = path;
            this.size = size;
        }
    }

    private static WebViewNativeLibrary 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 new WebViewNativeLibrary(apkPath + "!/" + entry, e.getSize());
                }
            }
        } catch (IOException e) {
            throw new WebViewFactory.MissingWebViewPackageException(e);
        }
        return null;
    }

    
Sets the size of the memory area in which to store the relro section.
/**
     * 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 lib, String relro);
    static native int nativeLoadWithRelroFile(String lib, String relro, ClassLoader clazzLoader);
}