content: /*
   * 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 whitelist 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();
          }
      }
  }
  