From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Pavel Grafov <pgrafov@google.com>
Date: Wed, 5 Apr 2023 15:15:41 +0000
Subject: [PATCH] Ensure policy has no absurdly long strings

The following APIs now enforce limits and throw IllegalArgumentException
when limits are violated:
* DPM.setTrustAgentConfiguration() limits agent packgage name,
  component name, and strings within configuration bundle.
* DPM.setPermittedAccessibilityServices() limits package names.
* DPM.setPermittedInputMethods() limits package names.
* DPM.setAccountManagementDisabled() limits account name.
* DPM.setLockTaskPackages() limits package names.
* DPM.setAffiliationIds() limits id.
* DPM.transferOwnership() limits strings inside the bundle.

Package names are limited at 223, because they become directory names
and it is a filesystem restriction, see FrameworkParsingPackageUtils.

All other strings are limited at 65535, because longer ones break binary
XML serializer.

The following APIs silently truncate strings that are long beyond reason:
* DPM.setShortSupportMessage() truncates message at 200.
* DPM.setLongSupportMessage() truncates message at 20000.
* DPM.setOrganizationName() truncates org name at 200.

Bug: 260729089
Test: atest com.android.server.devicepolicy
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:bb7e82ceaa6d16267e7b0e14563161b506d26be8)
Merged-In: Idcf54e408722f164d16bf2f24a00cd1f5b626d23
Change-Id: Idcf54e408722f164d16bf2f24a00cd1f5b626d23
---
 .../app/admin/DevicePolicyManager.java        |  3 +-
 .../DevicePolicyManagerService.java           | 87 +++++++++++++++++++
 2 files changed, 89 insertions(+), 1 deletion(-)

diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index 592026cda79b..a718b3e520dc 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -6046,7 +6046,8 @@ public class DevicePolicyManager {
 
     /**
      * Called by a device admin to set the long support message. This will be displayed to the user
-     * in the device administators settings screen.
+     * in the device administrators settings screen. If the message is longer than 20000 characters
+     * it may be truncated.
      * <p>
      * If the long support message needs to be localized, it is the responsibility of the
      * {@link DeviceAdminReceiver} to listen to the {@link Intent#ACTION_LOCALE_CHANGED} broadcast
diff --git a/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java b/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
index fe0ee096d303..af982a1a0724 100644
--- a/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
+++ b/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
@@ -171,12 +171,14 @@ import java.security.cert.CertificateException;
 import java.security.cert.CertificateFactory;
 import java.security.cert.X509Certificate;
 import java.text.DateFormat;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.Date;
 import java.util.List;
 import java.util.Map.Entry;
+import java.util.Queue;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 
@@ -214,6 +216,15 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
 
     private static final int REQUEST_EXPIRE_PASSWORD = 5571;
 
+    // Binary XML serializer doesn't support longer strings
+    private static final int MAX_POLICY_STRING_LENGTH = 65535;
+    // FrameworkParsingPackageUtils#MAX_FILE_NAME_SIZE, Android packages are used in dir names.
+    private static final int MAX_PACKAGE_NAME_LENGTH = 223;
+
+    private static final int MAX_LONG_SUPPORT_MESSAGE_LENGTH = 20000;
+    private static final int MAX_SHORT_SUPPORT_MESSAGE_LENGTH = 200;
+    private static final int MAX_ORG_NAME_LENGTH = 200;
+
     private static final long MS_PER_DAY = 86400 * 1000;
 
     private static final long EXPIRATION_GRACE_PERIOD_MS = 5 * MS_PER_DAY; // 5 days, in ms
@@ -6890,6 +6901,12 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
         }
         Preconditions.checkNotNull(admin, "admin is null");
         Preconditions.checkNotNull(agent, "agent is null");
+        enforceMaxPackageNameLength(agent.getPackageName());
+        final String agentAsString = agent.flattenToString();
+        enforceMaxStringLength(agentAsString, "agent name");
+        if (args != null) {
+            enforceMaxStringLength(args, "args");
+        }
         final int userHandle = UserHandle.getCallingUserId();
         synchronized (this) {
             ActiveAdmin ap = getActiveAdminForCallerLocked(admin,
@@ -7091,6 +7108,10 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
         Preconditions.checkNotNull(who, "ComponentName is null");
 
         if (packageList != null) {
+            for (String pkg : (List<String>) packageList) {
+                enforceMaxPackageNameLength(pkg);
+            }
+
             int userId = UserHandle.getCallingUserId();
             List<AccessibilityServiceInfo> enabledServices = null;
             long id = mInjector.binderClearCallingIdentity();
@@ -7272,6 +7293,10 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
         }
 
         if (packageList != null) {
+            for (String pkg : (List<String>) packageList) {
+                enforceMaxPackageNameLength(pkg);
+            }
+
             // InputMethodManager fetches input methods for current user.
             // So this can only be set when calling user is the current user
             // or parent is current user in case of managed profiles.
@@ -7820,6 +7845,7 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
             return;
         }
         Preconditions.checkNotNull(who, "ComponentName is null");
+        enforceMaxStringLength(accountType, "account type");
         synchronized (this) {
             ActiveAdmin ap = getActiveAdminForCallerLocked(who,
                     DeviceAdminInfo.USES_POLICY_PROFILE_OWNER);
@@ -8089,6 +8115,10 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
     public void setLockTaskPackages(ComponentName who, String[] packages)
             throws SecurityException {
         Preconditions.checkNotNull(who, "ComponentName is null");
+        for (String pkg : packages) {
+            enforceMaxPackageNameLength(pkg);
+        }
+
         synchronized (this) {
             ActiveAdmin deviceOwner = getActiveAdminWithPolicyForUidLocked(
                 who, DeviceAdminInfo.USES_POLICY_DEVICE_OWNER, mInjector.binderGetCallingUid());
@@ -8956,6 +8986,9 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
         if (!mHasFeature) {
             return;
         }
+
+        message = truncateIfLonger(message, MAX_LONG_SUPPORT_MESSAGE_LENGTH);
+
         Preconditions.checkNotNull(who, "ComponentName is null");
         final int userHandle = mInjector.userHandleGetCallingUserId();
         synchronized (this) {
@@ -8987,6 +9020,8 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
             return;
         }
         Preconditions.checkNotNull(who, "ComponentName is null");
+        message = truncateIfLonger(message, MAX_SHORT_SUPPORT_MESSAGE_LENGTH);
+
         final int userHandle = mInjector.userHandleGetCallingUserId();
         synchronized (this) {
             ActiveAdmin admin = getActiveAdminForUidLocked(who,
@@ -9004,6 +9039,7 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
             return null;
         }
         Preconditions.checkNotNull(who, "ComponentName is null");
+
         synchronized (this) {
             ActiveAdmin admin = getActiveAdminForUidLocked(who,
                     mInjector.binderGetCallingUid());
@@ -9114,6 +9150,9 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
         }
         Preconditions.checkNotNull(who, "ComponentName is null");
         final int userHandle = mInjector.userHandleGetCallingUserId();
+
+        text = truncateIfLonger(text, MAX_ORG_NAME_LENGTH);
+
         enforceManagedProfile(userHandle, "set organization name");
         synchronized (this) {
             ActiveAdmin admin = getActiveAdminForCallerLocked(who,
@@ -9697,4 +9736,52 @@ public class DevicePolicyManagerService extends IDevicePolicyManager.Stub {
         mInjector.getNotificationManager().notify(NETWORK_LOGGING_NOTIFICATION_ID, notification);
         saveSettingsLocked(mOwners.getDeviceOwnerUserId());
     }
+
+
+    /**
+     * Truncates char sequence to maximum length, nulls are ignored.
+     */
+    private static CharSequence truncateIfLonger(CharSequence input, int maxLength) {
+        return input == null || input.length() <= maxLength
+                ? input
+                : input.subSequence(0, maxLength);
+    }
+
+    /**
+     * Throw if string argument is too long to be serialized.
+     */
+    private static void enforceMaxStringLength(String str, String argName) {
+        Preconditions.checkArgument(
+                str.length() <= MAX_POLICY_STRING_LENGTH, argName + " loo long");
+    }
+
+    private static void enforceMaxPackageNameLength(String pkg) {
+        Preconditions.checkArgument(
+                pkg.length() <= MAX_PACKAGE_NAME_LENGTH, "Package name too long");
+    }
+
+    /**
+     * Throw if persistable bundle contains any string that we can't serialize.
+     */
+    private static void enforceMaxStringLength(PersistableBundle bundle, String argName) {
+        // Persistable bundles can have other persistable bundles as values, traverse with a queue.
+        Queue<PersistableBundle> queue = new ArrayDeque<>();
+        queue.add(bundle);
+        while (!queue.isEmpty()) {
+            PersistableBundle current = queue.remove();
+            for (String key : current.keySet()) {
+                enforceMaxStringLength(key, "key in " + argName);
+                Object value = current.get(key);
+                if (value instanceof String) {
+                    enforceMaxStringLength((String) value, "string value in " + argName);
+                } else if (value instanceof String[]) {
+                    for (String str : (String[]) value) {
+                        enforceMaxStringLength(str, "string value in " + argName);
+                    }
+                } else if (value instanceof PersistableBundle) {
+                    queue.add((PersistableBundle) value);
+                }
+            }
+        }
+    }
 }
