fix(util-endpoints): return null in parseArn for some empty elements (#3935)

Author: trivikr

packages/util-endpoints/src/lib/aws/parseArn.spec.ts

@@ -70,10 +70,13 @@ describe(parseArn.name, () => {
     expect(parseArn(input)).toEqual(outout);
   });
 
-  it.each(["some:random:string:separated:by:colons", "arn:aws:too:short"])(
-    "returns null for invalid arn %s",
-    (input: string) => {
-      expect(parseArn(input)).toBeNull();
-    }
-  );
+  it.each([
+    "arn::s3:us-west-2:123456789012:accesspoint:myendpoint", // partition not present
+    "arn:aws::us-west-2:123456789012:accesspoint:myendpoint", // service not present
+    "arn:aws:s3:us-west-2:123456789012:", // resource ID not present
+    "some:random:string:separated:by:colons",
+    "arn:aws:too:short",
+  ])("returns null for invalid arn %s", (input: string) => {
+    expect(parseArn(input)).toBeNull();
+  });
 });

packages/util-endpoints/src/lib/aws/parseArn.ts

@@ -8,17 +8,11 @@ import { EndpointARN } from "@aws-sdk/types";
 export const parseArn = (value: string): EndpointARN | null => {
   const segments = value.split(":");
 
-  if (segments.length < 6 || segments[0] !== "arn") return null;
+  if (segments.length < 6) return null;
 
-  const [
-    ,
-    //Skip "arn" literal
-    partition,
-    service,
-    region,
-    accountId,
-    ...resourceId
-  ] = segments;
+  const [arn, partition, service, region, accountId, ...resourceId] = segments;
+
+  if (arn !== "arn" || partition === "" || service === "" || resourceId[0] === "") return null;
 
   return {
     partition,