[Entitlements] Add a check for filesystem mismatch (elastic#123744)

Author: ldematte

libs/entitlement/src/main/java/org/elasticsearch/entitlement/runtime/policy/FileAccessTree.java

@@ -9,6 +9,7 @@
 
 package org.elasticsearch.entitlement.runtime.policy;
 
+import org.elasticsearch.core.Strings;
 import org.elasticsearch.entitlement.runtime.policy.entitlements.FilesEntitlement;
 import org.elasticsearch.entitlement.runtime.policy.entitlements.FilesEntitlement.Mode;
 import org.elasticsearch.logging.LogManager;
@@ -202,6 +203,7 @@ static String normalizePath(Path path) {
     }
 
     private boolean checkPath(String path, String[] paths) {
+        logger.trace(() -> Strings.format("checking [%s] against [%s]", path, String.join(",", paths)));
         if (paths.length == 0) {
             return false;
         }
@@ -219,6 +221,7 @@ private boolean checkPath(String path, String[] paths) {
     }
 
     private static boolean isParent(String maybeParent, String path) {
+        logger.trace(() -> Strings.format("checking isParent [%s] for [%s]", maybeParent, path));
         return path.startsWith(maybeParent) && path.startsWith(FILE_SEPARATOR, maybeParent.length());
     }
 

libs/entitlement/src/main/java/org/elasticsearch/entitlement/runtime/policy/PolicyManager.java

@@ -9,6 +9,7 @@
 
 package org.elasticsearch.entitlement.runtime.policy;
 
+import org.elasticsearch.core.PathUtils;
 import org.elasticsearch.core.Strings;
 import org.elasticsearch.core.SuppressForbidden;
 import org.elasticsearch.entitlement.instrumentation.InstrumentationService;
@@ -61,6 +62,8 @@ public class PolicyManager {
     static final String SERVER_COMPONENT_NAME = "(server)";
     static final String APM_AGENT_COMPONENT_NAME = "(APM agent)";
 
+    static final Class<?> DEFAULT_FILESYSTEM_CLASS = PathUtils.getDefaultFileSystem().getClass();
+
     /**
      * @param componentName the plugin name; or else one of the special component names
      *                      like {@link #SERVER_COMPONENT_NAME} or {@link #APM_AGENT_COMPONENT_NAME}.
@@ -305,7 +308,26 @@ public void checkFileRead(Class<?> callerClass, File file) {
         checkFileRead(callerClass, file.toPath());
     }
 
+    private static boolean isPathOnDefaultFilesystem(Path path) {
+        var pathFileSystemClass = path.getFileSystem().getClass();
+        if (path.getFileSystem().getClass() != DEFAULT_FILESYSTEM_CLASS) {
+            logger.trace(
+                () -> Strings.format(
+                    "File entitlement trivially allowed: path [%s] is for a different FileSystem class [%s], default is [%s]",
+                    path.toString(),
+                    pathFileSystemClass.getName(),
+                    DEFAULT_FILESYSTEM_CLASS.getName()
+                )
+            );
+            return false;
+        }
+        return true;
+    }
+
     public void checkFileRead(Class<?> callerClass, Path path) {
+        if (isPathOnDefaultFilesystem(path) == false) {
+            return;
+        }
         var requestingClass = requestingClass(callerClass);
         if (isTriviallyAllowed(requestingClass)) {
             return;
@@ -332,6 +354,9 @@ public void checkFileWrite(Class<?> callerClass, File file) {
     }
 
     public void checkFileWrite(Class<?> callerClass, Path path) {
+        if (isPathOnDefaultFilesystem(path) == false) {
+            return;
+        }
         var requestingClass = requestingClass(callerClass);
         if (isTriviallyAllowed(requestingClass)) {
             return;

libs/entitlement/src/main/java/org/elasticsearch/entitlement/runtime/policy/entitlements/FilesEntitlement.java

@@ -108,7 +108,6 @@ static boolean isAbsolutePath(String path) {
                 // Unix/BSD absolute
                 return true;
             }
-
             return isWindowsAbsolutePath(path);
         }