remove duplicate paths in FileAccessTree

Author: jdconrad

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

@@ -153,14 +153,15 @@ private FileAccessTree(
         this.writePaths = pruneSortedPaths(writePaths).toArray(new String[0]);
     }
 
-    private static List<String> pruneSortedPaths(List<String> paths) {
+    // package private for testing
+    static List<String> pruneSortedPaths(List<String> paths) {
         List<String> prunedReadPaths = new ArrayList<>();
         if (paths.isEmpty() == false) {
             String currentPath = paths.get(0);
             prunedReadPaths.add(currentPath);
             for (int i = 1; i < paths.size(); ++i) {
                 String nextPath = paths.get(i);
-                if (isParent(currentPath, nextPath) == false) {
+                if (currentPath.equals(nextPath) == false && isParent(currentPath, nextPath) == false) {
                     prunedReadPaths.add(nextPath);
                     currentPath = nextPath;
                 }

libs/entitlement/src/test/java/org/elasticsearch/entitlement/runtime/policy/FileAccessTreeTests.java

@@ -316,6 +316,12 @@ public void testInvalidExclusiveAccess() {
         assertThat(tree.canWrite(path("a")), is(false));
     }
 
+    public void testDuplicatePrunedPaths() {
+        List<String> paths = List.of("/a", "/a", "/a/b", "/a/b", "/b/c", "b/c/d", "b/c/d", "b/c/d", "e/f", "e/f");
+        paths = FileAccessTree.pruneSortedPaths(paths);
+        assertEquals(List.of("/a", "/b/c", "b/c/d", "e/f"), paths);
+    }
+
     FileAccessTree accessTree(FilesEntitlement entitlement, List<ExclusivePath> exclusivePaths) {
         return FileAccessTree.of("test-component", "test-module", entitlement, TEST_PATH_LOOKUP, exclusivePaths);
     }