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/*
* Copyright (C) 2018 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 com.android.internal.os;
import android.os.Process;
import android.system.ErrnoException;
import android.system.Os;
import android.system.OsConstants;
import android.util.Log;
/**
* ChildZygoteInit is shared by both the Application and WebView zygote to initialize
* and run a (child) Zygote server.
*
* @hide
*/
public class ChildZygoteInit {
private static final String TAG = "ChildZygoteInit";
static String parseSocketNameFromArgs(String[] argv) {
for (String arg : argv) {
if (arg.startsWith(Zygote.CHILD_ZYGOTE_SOCKET_NAME_ARG)) {
return arg.substring(Zygote.CHILD_ZYGOTE_SOCKET_NAME_ARG.length());
}
}
return null;
}
static String parseAbiListFromArgs(String[] argv) {
for (String arg : argv) {
if (arg.startsWith(Zygote.CHILD_ZYGOTE_ABI_LIST_ARG)) {
return arg.substring(Zygote.CHILD_ZYGOTE_ABI_LIST_ARG.length());
}
}
return null;
}
static int parseIntFromArg(String[] argv, String desiredArg) {
int value = -1;
for (String arg : argv) {
if (arg.startsWith(desiredArg)) {
String valueStr = arg.substring(arg.indexOf('=') + 1);
try {
value = Integer.parseInt(valueStr);
} catch (NumberFormatException e) {
throw new IllegalArgumentException("Invalid int argument: "
+ valueStr, e);
}
}
}
return value;
}
/**
* Starts a ZygoteServer and listens for requests
*
* @param server An instance of a ZygoteServer to listen on
* @param args Passed in arguments for this ZygoteServer
*/
static void runZygoteServer(ZygoteServer server, String[] args) {
String socketName = parseSocketNameFromArgs(args);
if (socketName == null) {
throw new NullPointerException("No socketName specified");
}
String abiList = parseAbiListFromArgs(args);
if (abiList == null) {
throw new NullPointerException("No abiList specified");
}
try {
Os.prctl(OsConstants.PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0);
} catch (ErrnoException ex) {
throw new RuntimeException("Failed to set PR_SET_NO_NEW_PRIVS", ex);
}
int uidGidMin = parseIntFromArg(args, Zygote.CHILD_ZYGOTE_UID_RANGE_START);
int uidGidMax = parseIntFromArg(args, Zygote.CHILD_ZYGOTE_UID_RANGE_END);
if (uidGidMin == -1 || uidGidMax == -1) {
throw new RuntimeException("Couldn't parse UID range start/end");
}
if (uidGidMin > uidGidMax) {
throw new RuntimeException("Passed in UID range is invalid, min > max.");
}
// Verify the UIDs at least do not include system UIDs; we can't easily verify there
// are just isolated UIDs in the range, because for the webview zygote, there is no
// single range that captures all possible isolated UIDs.
// TODO(b/123615476) narrow this down
if (uidGidMin < Process.FIRST_APP_ZYGOTE_ISOLATED_UID) {
throw new RuntimeException("Passed in UID range does not map to isolated processes.");
}
/**
* Install a seccomp filter that ensure this Zygote can only setuid()/setgid()
* to the passed in range.
*/
Zygote.nativeInstallSeccompUidGidFilter(uidGidMin, uidGidMax);
final Runnable caller;
try {
server.registerServerSocketAtAbstractName(socketName);
// Add the abstract socket to the FD allow list so that the native zygote code
// can properly detach it after forking.
Zygote.nativeAllowFileAcrossFork("ABSTRACT/" + socketName);
// The select loop returns early in the child process after a fork and
// loops forever in the zygote.
caller = server.runSelectLoop(abiList);
} catch (RuntimeException e) {
Log.e(TAG, "Fatal exception:", e);
throw e;
} finally {
server.closeServerSocket();
}
// We're in the child process and have exited the select loop. Proceed to execute the
// command.
if (caller != null) {
caller.run();
}
}
}
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