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:456dbcae5ae4bc0d8f73f8cb97b57c8de6958f9c)
Merged-In: Idcf54e408722f164d16bf2f24a00cd1f5b626d23
Change-Id: Idcf54e408722f164d16bf2f24a00cd1f5b626d23

2 files changed, 91 insertions, 4 deletions

diff --git a/core/java/android/app/admin/DevicePolicyManager.java b/core/java/android/app/admin/DevicePolicyManager.java
index 3ef89b8ca0ad..d98edaa2b7e5 100644
--- a/core/java/android/app/admin/DevicePolicyManager.java
+++ b/core/java/android/app/admin/DevicePolicyManager.java
@@ -12402,7 +12402,8 @@ 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 27d5eb4541e5..c07b058bb2ca 100644
--- a/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
+++ b/services/devicepolicy/java/com/android/server/devicepolicy/DevicePolicyManagerService.java
@@ -397,6 +397,7 @@ import java.security.cert.CertificateFactory;
 import java.security.cert.X509Certificate;
 import java.text.DateFormat;
 import java.time.LocalDate;
+import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collection;
@@ -408,6 +409,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Queue;
 import java.util.Set;
 import java.util.concurrent.Executor;
 import java.util.concurrent.TimeUnit;
@@ -439,7 +441,15 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
 
     private static final int REQUEST_PROFILE_OFF_DEADLINE = 5572;
 
+    // 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_PROFILE_NAME_LENGTH = 200;
+    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 = TimeUnit.DAYS.toMillis(1);
 
@@ -10053,6 +10063,12 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
         }
         Objects.requireNonNull(admin, "admin is null");
         Objects.requireNonNull(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 (getLockObject()) {
             ActiveAdmin ap = getActiveAdminForCallerLocked(admin,
@@ -10294,6 +10310,10 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
         final CallerIdentity caller = getCallerIdentity(who);
 
         if (packageList != null) {
+            for (String pkg : packageList) {
+                enforceMaxPackageNameLength(pkg);
+            }
+
             int userId = caller.getUserId();
             final List<AccessibilityServiceInfo> enabledServices;
             long id = mInjector.binderClearCallingIdentity();
@@ -10463,6 +10483,10 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
         }
 
         if (packageList != null) {
+            for (String pkg : packageList) {
+                enforceMaxPackageNameLength(pkg);
+            }
+
             List<InputMethodInfo> enabledImes = mInjector.binderWithCleanCallingIdentity(() ->
                     InputMethodManagerInternal.get().getEnabledInputMethodListAsUser(userId));
             if (enabledImes != null) {
@@ -11793,6 +11817,8 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
             return;
         }
         Objects.requireNonNull(who, "ComponentName is null");
+        enforceMaxStringLength(accountType, "account type");
+
         final CallerIdentity caller = getCallerIdentity(who);
         synchronized (getLockObject()) {
             /*
@@ -12214,6 +12240,10 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
             throws SecurityException {
         Objects.requireNonNull(who, "ComponentName is null");
         Objects.requireNonNull(packages, "packages is null");
+        for (String pkg : packages) {
+            enforceMaxPackageNameLength(pkg);
+        }
+
         final CallerIdentity caller = getCallerIdentity(who);
 
         synchronized (getLockObject()) {
@@ -14333,6 +14363,8 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
             return;
         }
         Objects.requireNonNull(who, "ComponentName is null");
+        message = truncateIfLonger(message, MAX_SHORT_SUPPORT_MESSAGE_LENGTH);
+
         final CallerIdentity caller = getCallerIdentity(who);
         synchronized (getLockObject()) {
             ActiveAdmin admin = getActiveAdminForUidLocked(who, caller.getUid());
@@ -14365,6 +14397,9 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
         if (!mHasFeature) {
             return;
         }
+
+        message = truncateIfLonger(message, MAX_LONG_SUPPORT_MESSAGE_LENGTH);
+
         Objects.requireNonNull(who, "ComponentName is null");
         final CallerIdentity caller = getCallerIdentity(who);
         synchronized (getLockObject()) {
@@ -14514,6 +14549,8 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
         Objects.requireNonNull(who, "ComponentName is null");
         final CallerIdentity caller = getCallerIdentity(who);
 
+        text = truncateIfLonger(text, MAX_ORG_NAME_LENGTH);
+
         synchronized (getLockObject()) {
             ActiveAdmin admin = getProfileOwnerOrDeviceOwnerLocked(caller);
             if (!TextUtils.equals(admin.organizationName, text)) {
@@ -14786,9 +14823,8 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
             throw new IllegalArgumentException("ids must not be null");
         }
         for (String id : ids) {
-            if (TextUtils.isEmpty(id)) {
-                throw new IllegalArgumentException("ids must not contain empty string");
-            }
+            Preconditions.checkArgument(!TextUtils.isEmpty(id), "ids must not have empty string");
+            enforceMaxStringLength(id, "affiliation id");
         }
 
         final Set<String> affiliationIds = new ArraySet<>(ids);
@@ -16099,6 +16135,9 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
                 "Provided administrator and target are the same object.");
         Preconditions.checkArgument(!admin.getPackageName().equals(target.getPackageName()),
                 "Provided administrator and target have the same package name.");
+        if (bundle != null) {
+            enforceMaxStringLength(bundle, "bundle");
+        }
 
         final CallerIdentity caller = getCallerIdentity(admin);
         Preconditions.checkCallAuthorization(
@@ -18900,4 +18939,51 @@ public class DevicePolicyManagerService extends BaseIDevicePolicyManager {
             return result;
         });
     }
+
+    /**
+     * 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);
+                }
+            }
+        }
+    }
 }