[Backport 2.19] Create a WildcardMatcher.NONE when creating a WildcardMatcher with an empty string (#5694) (#5715)

Signed-off-by: Craig Perkins <[email protected]>

Author: cwperks

CHANGELOG.md

@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ## [Unreleased 2.19.x]
 
+### Bug Fixes
+- Create a WildcardMatcher.NONE when creating a WildcardMatcher with an empty string ([#5694](https://github.com/opensearch-project/security/pull/5694))
+
 ### Maintenance
 - Bump `com.nimbusds:nimbus-jose-jwt:9.48` from 9.48 to 10.0.2 ([#5480](https://github.com/opensearch-project/security/pull/5480))
 - Bump `checkstyle` from 10.3.3 to 10.26.1 ([#5480](https://github.com/opensearch-project/security/pull/5480))

src/main/java/org/opensearch/security/support/WildcardMatcher.java

@@ -132,7 +132,7 @@ public String toString() {
     };
 
     public static WildcardMatcher from(String pattern) {
-        if (pattern == null) {
+        if (pattern == null || pattern.isBlank()) {
             return NONE;
         } else if (pattern.equals("*")) {
             return ANY;

src/test/java/org/opensearch/security/UtilTests.java

@@ -81,6 +81,9 @@ public void testWildcardMatcherClasses() {
         assertTrue(wc("abc").test("abc"));
         assertFalse(wc("ABC").test("abc"));
         assertFalse(wc(null).test("abc"));
+        assertFalse(wc("").test("abc"));
+        // Creating a WildcardMatcher with blank should create a matcher that matches nothing
+        assertFalse(wc("").test(""));
         assertTrue(WildcardMatcher.from(null, "abc").test("abc"));
     }