Added skip in HeaderTransformsHelper too , to be consistent

Author: joviegas

core/auth/src/main/java/software/amazon/awssdk/auth/signer/internal/util/HeaderTransformsHelper.java

@@ -32,7 +32,7 @@
 public final class HeaderTransformsHelper {
 
     private static final List<String> LIST_OF_HEADERS_TO_IGNORE_IN_LOWER_CASE =
-            Arrays.asList("connection", "x-amzn-trace-id", "user-agent", "expect");
+        Arrays.asList("connection", "x-amzn-trace-id", "user-agent", "expect", "transfer-encoding");
 
     private HeaderTransformsHelper() {
     }

core/auth/src/test/java/software/amazon/awssdk/auth/signer/internal/util/HeaderTransformsHelperTest.java

@@ -0,0 +1,61 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License").
+ * You may not use this file except in compliance with the License.
+ * A copy of the License is located at
+ *
+ *  http://aws.amazon.com/apache2.0
+ *
+ * or in the "license" file accompanying this file. This file is distributed
+ * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
+ * express or implied. See the License for the specific language governing
+ * permissions and limitations under the License.
+ */
+
+
+package software.amazon.awssdk.auth.signer.internal.util;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.TreeMap;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class HeaderTransformsHelperTest {
+
+    @Test
+    void shouldExcludeIgnoredHeadersWhenCanonicalizing() {
+        Map<String, List<String>> headers = new HashMap<>();
+
+        // Ignored headers that should be excluded from signing
+        headers.put("connection", Collections.singletonList("keep-alive"));
+        headers.put("x-amzn-trace-id", Collections.singletonList("Root=1-234567890"));
+        headers.put("user-agent", Collections.singletonList("md/user"));
+        headers.put("expect", Collections.singletonList("100-continue"));
+        headers.put("transfer-encoding", Collections.singletonList("chunked"));
+
+        // Headers that should be included in signing
+        headers.put("Content-Type", Collections.singletonList("application/json"));
+        headers.put("Host", Collections.singletonList("example.com"));
+
+        Map<String, List<String>> canonicalizedHeaders = HeaderTransformsHelper.canonicalizeSigningHeaders(headers);
+
+        assertEquals(2, canonicalizedHeaders.size(), "Should only contain non-ignored headers");
+
+        // Verify included headers
+        assertTrue(canonicalizedHeaders.containsKey("content-type"), "Should contain content-type header");
+        assertTrue(canonicalizedHeaders.containsKey("host"), "Should contain host header");
+
+        // Verify excluded headers
+        assertFalse(canonicalizedHeaders.containsKey("connection"), "Should not contain connection header");
+        assertFalse(canonicalizedHeaders.containsKey("x-amzn-trace-id"), "Should not contain x-amzn-trace-id header");
+        assertFalse(canonicalizedHeaders.containsKey("user-agent"), "Should not contain user-agent header");
+        assertFalse(canonicalizedHeaders.containsKey("expect"), "Should not contain expect header");
+        assertFalse(canonicalizedHeaders.containsKey("transfer-encoding"), "Should not contain transfer-encoding header");
+    }
+
+}