chore: skip checksum computation if user as set checksum header field

Author: trivikr

packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.spec.ts

@@ -67,31 +67,33 @@ describe(flexibleChecksumsMiddleware.name, () => {
     });
 
     describe("request checksum", () => {
-      afterEach(() => {
-        expect(getChecksumAlgorithmForRequest).toHaveBeenCalledTimes(1);
-      });
-
       it("if checksumAlgorithm is not defined", async () => {
         vi.mocked(getChecksumAlgorithmForRequest).mockReturnValue(undefined);
         const handler = flexibleChecksumsMiddleware(mockConfig, mockMiddlewareConfig)(mockNext, {});
         await handler(mockArgs);
         expect(getChecksumLocationName).not.toHaveBeenCalled();
         expect(mockNext).toHaveBeenCalledWith(mockArgs);
         expect(selectChecksumAlgorithmFunction).not.toHaveBeenCalled();
+        expect(getChecksumAlgorithmForRequest).toHaveBeenCalledTimes(1);
       });
 
-      it("if header is already present", async () => {
+      it.each([
+        ...Object.values(ChecksumAlgorithm).map((val) => `x-amz-checksum-${val.toLowerCase()}`), // all current checksum locations
+        ...Object.values(ChecksumAlgorithm).map((val) => `X-AMZ-CHECKSUM-${val}`), // all current checksum locations in uppercase
+        `x-amz-checksum-emoji`, // any checksum post prefix
+        `X-AMZ-CHECKSUM-EMOJI`, // any checksum post prefix in uppercase
+      ])("skip if header '%s' is already present", async (headerName) => {
         const handler = flexibleChecksumsMiddleware(mockConfig, mockMiddlewareConfig)(mockNext, {});
-        const mockHeadersWithChecksumHeader = { ...mockHeaders, [mockChecksumLocationName]: "mockHeaderValue" };
+        const mockHeadersWithChecksumHeader = { ...mockHeaders, [headerName]: "mockHeaderValue" };
         const mockArgsWithChecksumHeader = {
           ...mockArgs,
           request: { ...mockRequest, headers: mockHeadersWithChecksumHeader },
         };
         await handler(mockArgsWithChecksumHeader);
-        expect(getChecksumLocationName).toHaveBeenCalledWith(ChecksumAlgorithm.CRC32);
-        expect(selectChecksumAlgorithmFunction).toHaveBeenCalledWith(ChecksumAlgorithm.CRC32, mockConfig);
+        expect(getChecksumLocationName).not.toHaveBeenCalled();
+        expect(selectChecksumAlgorithmFunction).not.toHaveBeenCalled();
+        expect(hasHeader).not.toHaveBeenCalled();
         expect(mockNext).toHaveBeenCalledWith(mockArgsWithChecksumHeader);
-        expect(hasHeader).toHaveBeenCalledWith(mockChecksumLocationName, mockHeadersWithChecksumHeader);
       });
     });
   });

packages/middleware-flexible-checksums/src/flexibleChecksumsMiddleware.ts

@@ -57,6 +57,12 @@ export const flexibleChecksumsMiddleware =
       return next(args);
     }
 
+    for (const header of Object.keys(args.request.headers)) {
+      if (header.toLowerCase().startsWith("x-amz-checksum-")) {
+        return next(args);
+      }
+    }
+
     const { request } = args;
     const { body: requestBody, headers } = request;
     const { base64Encoder, streamHasher } = config;