1 /*
2  * Copyright (C) 2012 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.internal.util;
18 
19 import android.app.AppOpsManager;
20 import android.content.Context;
21 import android.content.pm.PackageManager;
22 import android.os.Binder;
23 import android.os.Handler;
24 import android.util.Slog;
25 
26 import java.io.PrintWriter;
27 import java.io.StringWriter;
28 
29 /**
30  * Helper functions for dumping the state of system services.
31  */
32 public final class DumpUtils {
33     private static final String TAG = "DumpUtils";
34     private static final boolean DEBUG = false;
35 
DumpUtils()36     private DumpUtils() {
37     }
38 
39     /**
40      * Helper for dumping state owned by a handler thread.
41      *
42      * Because the caller might be holding an important lock that the handler is
43      * trying to acquire, we use a short timeout to avoid deadlocks.  The process
44      * is inelegant but this function is only used for debugging purposes.
45      */
dumpAsync(Handler handler, final Dump dump, PrintWriter pw, final String prefix, long timeout)46     public static void dumpAsync(Handler handler, final Dump dump, PrintWriter pw,
47             final String prefix, long timeout) {
48         final StringWriter sw = new StringWriter();
49         if (handler.runWithScissors(new Runnable() {
50             @Override
51             public void run() {
52                 PrintWriter lpw = new FastPrintWriter(sw);
53                 dump.dump(lpw, prefix);
54                 lpw.close();
55             }
56         }, timeout)) {
57             pw.print(sw.toString());
58         } else {
59             pw.println("... timed out");
60         }
61     }
62 
63     public interface Dump {
dump(PrintWriter pw, String prefix)64         void dump(PrintWriter pw, String prefix);
65     }
66 
logMessage(PrintWriter pw, String msg)67     private static void logMessage(PrintWriter pw, String msg) {
68         if (DEBUG) Slog.v(TAG, msg);
69         pw.println(msg);
70     }
71 
72     /**
73      * Verify that caller holds {@link android.Manifest.permission#DUMP}.
74      *
75      * @return true if access should be granted.
76      * @hide
77      */
checkDumpPermission(Context context, String tag, PrintWriter pw)78     public static boolean checkDumpPermission(Context context, String tag, PrintWriter pw) {
79         if (context.checkCallingOrSelfPermission(android.Manifest.permission.DUMP)
80                 != PackageManager.PERMISSION_GRANTED) {
81             logMessage(pw, "Permission Denial: can't dump " + tag + " from from pid="
82                     + Binder.getCallingPid() + ", uid=" + Binder.getCallingUid()
83                     + " due to missing android.permission.DUMP permission");
84             return false;
85         } else {
86             return true;
87         }
88     }
89 
90     /**
91      * Verify that caller holds
92      * {@link android.Manifest.permission#PACKAGE_USAGE_STATS} and that they
93      * have {@link AppOpsManager#OP_GET_USAGE_STATS} access.
94      *
95      * @return true if access should be granted.
96      * @hide
97      */
checkUsageStatsPermission(Context context, String tag, PrintWriter pw)98     public static boolean checkUsageStatsPermission(Context context, String tag, PrintWriter pw) {
99         // System internals always get access
100         final int uid = Binder.getCallingUid();
101         switch (uid) {
102             case android.os.Process.ROOT_UID:
103             case android.os.Process.SYSTEM_UID:
104             case android.os.Process.SHELL_UID:
105                 return true;
106         }
107 
108         // Caller always needs to hold permission
109         if (context.checkCallingOrSelfPermission(android.Manifest.permission.PACKAGE_USAGE_STATS)
110                 != PackageManager.PERMISSION_GRANTED) {
111             logMessage(pw, "Permission Denial: can't dump " + tag + " from from pid="
112                     + Binder.getCallingPid() + ", uid=" + Binder.getCallingUid()
113                     + " due to missing android.permission.PACKAGE_USAGE_STATS permission");
114             return false;
115         }
116 
117         // And finally, caller needs to have appops access; this is totally
118         // hacky, but it's the easiest way to wire this up without retrofitting
119         // Binder.dump() to pass through package names.
120         final AppOpsManager appOps = context.getSystemService(AppOpsManager.class);
121         final String[] pkgs = context.getPackageManager().getPackagesForUid(uid);
122         if (pkgs != null) {
123             for (String pkg : pkgs) {
124                 switch (appOps.checkOpNoThrow(AppOpsManager.OP_GET_USAGE_STATS, uid, pkg)) {
125                     case AppOpsManager.MODE_ALLOWED:
126                         if (DEBUG) Slog.v(TAG, "Found package " + pkg + " with "
127                                 + "android:get_usage_stats allowed");
128                         return true;
129                     case AppOpsManager.MODE_DEFAULT:
130                         if (DEBUG) Slog.v(TAG, "Found package " + pkg + " with "
131                                 + "android:get_usage_stats default");
132                         return true;
133                 }
134             }
135         }
136 
137         logMessage(pw, "Permission Denial: can't dump " + tag + " from from pid="
138                 + Binder.getCallingPid() + ", uid=" + Binder.getCallingUid()
139                 + " due to android:get_usage_stats app-op not allowed");
140         return false;
141     }
142 
143     /**
144      * Verify that caller holds both {@link android.Manifest.permission#DUMP}
145      * and {@link android.Manifest.permission#PACKAGE_USAGE_STATS}, and that
146      * they have {@link AppOpsManager#OP_GET_USAGE_STATS} access.
147      *
148      * @return true if access should be granted.
149      * @hide
150      */
checkDumpAndUsageStatsPermission(Context context, String tag, PrintWriter pw)151     public static boolean checkDumpAndUsageStatsPermission(Context context, String tag,
152             PrintWriter pw) {
153         return checkDumpPermission(context, tag, pw) && checkUsageStatsPermission(context, tag, pw);
154     }
155 }
156