fix: Fix signer to allow streaming unsigned payload without checksum …

…& add integration test (#1671)

* Refactor determineSignedBodyValue logic and fix it.

* Add integration test for stremaing payload with unsigned chunks.

* Resolve PR comments

---------

Co-authored-by: Sichan Yoo <[email protected]>
Co-authored-by: Josh Elkins <[email protected]>

IntegrationTests/Services/AWSS3IntegrationTests/S3FlexibleChecksumsTests.swift

@@ -8,6 +8,7 @@
 import Smithy
 import XCTest
 import AWSS3
+import SmithyHTTPAPI
 @testable import ClientRuntime
 import class SmithyStreams.BufferedStream
 import class SmithyChecksums.ValidatingBufferedStream
@@ -81,6 +82,46 @@ final class S3FlexibleChecksumsTests: S3XCTestCase {
         XCTAssertEqual(data, originalData)
     }
 
+    // Streaming unsigned payload without checksum (chunked encoding)
+    class DisablePayloadSigning<InputType, OutputType>: HttpInterceptor {
+        func modifyBeforeRetryLoop(context: some MutableRequest<InputType, RequestType>) async throws {
+            context.getAttributes().set(key: SmithyHTTPAPIKeys.hasUnsignedPayloadTrait, value: true)
+        }
+        func modifyBeforeTransmit(context: some MutableRequest<InputType, RequestType>) async throws {
+            context.getRequest().withHeader(name: "x-amz-content-sha256", value: "STREAMING-UNSIGNED-PAYLOAD-TRAILER")
+        }
+    }
+
+    class DisablePayloadSigningProvider: HttpInterceptorProvider {
+        func create<InputType, OutputType>() -> any HttpInterceptor<InputType, OutputType> {
+            return DisablePayloadSigning()
+        }
+    }
+
+    func test_putGetObject_streamining_unsigned_chunked() async throws {
+        let config = try await S3Client.S3ClientConfiguration(region: region)
+        config.addInterceptorProvider(DisablePayloadSigningProvider())
+        let customizedClient = S3Client(config: config)
+
+        let bufferedStream = BufferedStream(data: originalData, isClosed: true)
+        let objectName = "flexible-checksums-s3-test-unsigned-chunked"
+
+        let putObjectInput = PutObjectInput(
+            body: .stream(bufferedStream),
+            bucket: bucketName,
+            key: objectName
+        )
+
+        _ = try await customizedClient.putObject(input: putObjectInput)
+
+        let getObjectInput = GetObjectInput(bucket: bucketName, key: objectName)
+        let getObjectOutput = try await client.getObject(input: getObjectInput)
+        let body = try XCTUnwrap(getObjectOutput.body)
+        let data = try await body.readData()
+        XCTAssertEqual(data, originalData)
+    }
+
+
     // MARK: - Private methods
 
     private func _testPutGetObject(

Sources/Core/AWSSDKHTTPAuth/Sources/AWSSDKHTTPAuth/AWSSigV4Signer.swift

@@ -256,13 +256,10 @@ public class AWSSigV4Signer: SmithyHTTPAuthAPI.Signer {
             }
         }
 
-        // streaming + eligible for chunked transfer
-        if !checksumIsPresent {
-            return isUnsignedBody ? .unsignedPayload : .streamingSha256Payload
-        } else {
-            // checksum is present
-            return isUnsignedBody ? .streamingUnsignedPayloadTrailer : .streamingSha256PayloadTrailer
-        }
+        // STREAMING-UNSIGNED-PAYLOAD-TRAILER
+        if isUnsignedBody { return .streamingUnsignedPayloadTrailer }
+
+        return checksumIsPresent ? .streamingSha256PayloadTrailer : .streamingSha256Payload
     }
 }