LinkScanner: performance improvements

Signed-off-by: Tavi <tavi@divested.dev>

app/src/main/java/us/spotco/malwarescanner/LinkScannerService.java

@@ -18,7 +18,7 @@ public class LinkScannerService extends AccessibilityService {
 
     private static final String hostnameRegex = "^((?!-)[A-Za-z0-9-]{1,63}(?<!-)\\.)+[A-Za-z]{2,6}$"; //Credit: http://www.mkyong.com/regular-expressions/domain-name-regular-expression-example/
     private static final Pattern hostnamePattern = Pattern.compile(hostnameRegex);
-    private static final ConcurrentSkipListSet<Integer> scannedObjects = new ConcurrentSkipListSet<>();
+    private static final ConcurrentSkipListSet<Integer> scannedText = new ConcurrentSkipListSet<>();
     private static final ConcurrentSkipListSet<String> scannedDomains = new ConcurrentSkipListSet<>();
     private NotificationManager notificationManager = null;
 
@@ -50,18 +50,20 @@ public class LinkScannerService extends AccessibilityService {
                 return;
             }
 
-            //Don't scan if we already did
-            int hash = mNodeInfo.toString().hashCode();
-            if (scannedObjects.contains(hash)) {
-                return;
-            } else {
-                scannedObjects.add(hash);
-            }
-
             //Get and check the text
             String text = (String) mNodeInfo.getText();
-            if (text != null && text.contains(".")) {
+            if (text != null && text.contains(".") && text.length() < 10000) {
-                scanText(text.toLowerCase());
+                //Don't scan text if we already did
+                int hashDomain = mNodeInfo.getText().hashCode();
+                if (scannedText.contains(hashDomain)) {
+                    return;
+                } else {
+                    if (scannedText.size() > 10000) {
+                        scannedText.clear();
+                    }
+                    scannedText.add(hashDomain);
+                    scanText(text.toLowerCase());
+                }
             }
 
             //Finish if no more children
@@ -80,12 +82,7 @@ public class LinkScannerService extends AccessibilityService {
     private void scanText(String haystack) {
         Matcher matcher = hostnamePattern.matcher(haystack);
         while (matcher.find()) {
-            if (!scannedDomains.contains(matcher.group())) {
+            scanDomain(matcher.group());
-                scannedDomains.add(matcher.group());
-                if (Database.domains.mightContain(matcher.group())) {
-                    sendNotification(matcher.group());
-                }
-            }
         }
         if (haystack.contains("/")) {
             for (String split : haystack.split("/")) {
@@ -94,6 +91,19 @@ public class LinkScannerService extends AccessibilityService {
         }
     }
 
+    private void scanDomain(String domain) {
+        //Don't scan domain if we already did
+        if (!scannedDomains.contains(domain)) {
+            if (scannedDomains.size() > 1000) {
+                scannedDomains.clear();
+            }
+            scannedDomains.add(domain);
+            if (Database.domains.mightContain(domain)) {
+                sendNotification(domain);
+            }
+        }
+    }
+
     private void sendNotification(String link) {
         link = link.replaceAll("\\.", "[.]");
         Notification.Builder mBuilder =

app/src/main/res/values/strings.xml

@@ -83,5 +83,5 @@
     <string name="lblNotificationLinkDetection">Malicious Link Detected:</string>
     <string name="lblLinkScannerToggle">Link Scanner</string>
     <string name="confirm_link_scanner_title">Enable link scanner?</string>
-    <string name="confirm_link_scanner_summary">[EXPERIMENTAL]\nThis will download an additional database of domains.\nAny domains found in screen content will be checked against the database.\nThis requires granting accessibility service permission manually.</string>
+    <string name="confirm_link_scanner_summary">[EXPERIMENTAL]\nThis will download an additional database of domains.\nAny domains found in screen content will be checked against the database.\nThis requires granting accessibility service permission manually.\nThis can have a substantial performance impact on screen with large amounts of text.</string>
 </resources>

app/src/main/res/xml/accessibility_service_config.xml

@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <accessibility-service xmlns:android="http://schemas.android.com/apk/res/android"
     android:description="@string/accessibility_service_description"
-    android:accessibilityEventTypes="typeAllMask"
+    android:accessibilityEventTypes="typeWindowContentChanged|typeViewTextChanged"
     android:accessibilityFlags="flagDefault"
     android:accessibilityFeedbackType="feedbackGeneric"
     android:notificationTimeout="1"