Handle older S3 packages for operations that require MD5 or checksums

generator/.DevConfigs/43745a80-c082-4df4-a73e-413191e5b816.json

@@ -0,0 +1,9 @@
+{
+    "core": {
+        "updateMinimum": true,
+        "type": "Patch",
+        "changeLogMessages": [
+            "Update data integrity component to handle older versions of the `AWSSDK.S3` package when operations require a `Content-MD5` header"
+        ]
+    }
+}

sdk/src/Core/Amazon.Runtime/Internal/Util/ChecksumUtils.cs

@@ -347,7 +347,13 @@ public static void SetChecksumData(IRequest request, string checksumAlgorithm, b
             // S3 does not support).
 
             // TODO: Similar to "SetRequestChecksum", this method should be removed in V4.
-            if (!string.IsNullOrEmpty(checksumAlgorithm))
+            if (fallbackToMD5)
+            {
+                // Reported in https://github.com/aws/aws-sdk-net/issues/3641
+                // Some operations will fail if the Content-MD5 header is not set, so we need to set it to maintain backwards compatibility.
+                SetChecksumData(request);
+            }
+            else if (!string.IsNullOrEmpty(checksumAlgorithm))
             {
                 SetChecksumData(request, checksumAlgorithm, fallbackToMD5, isRequestChecksumRequired: true);
             }

sdk/src/Core/Amazon.Runtime/Pipeline/HttpHandler/_netstandard/HttpRequestMessageFactory.cs

@@ -625,7 +625,20 @@ public void WriteToRequestBody(HttpContent requestContent, Stream contentStream,
             if ((isChunkedUploadWrapperStreamWithLength || isTrailingHeadersWrapperStreamWithLength || isCompressionWrapperStreamWithLength)
                 || (chunkedUploadWrapperStream == null && trailingHeadersWrapperStream == null && compressionWrapperStream == null))
             {
-                _request.Content.Headers.ContentLength = contentStream.Length - contentStream.Position;
+                long position;
+                try
+                {
+                    position = contentStream.Position;
+                }
+                catch (NotSupportedException)
+                {
+                    // If this method is invoked from an older service package, the content stream may not support getting the
+                    // current position (for example, "MD5Stream" doesn't).
+                    // In this case, we'll assume the position is 0 to maintain the previous behavior.
+                    position = 0;
+                }
+
+                _request.Content.Headers.ContentLength = contentStream.Length - position;
             }
 
             WriteContentHeaders(contentHeaders);