Add PostObject Checksum (#17244)

internal/hash/reader.go

@@ -170,7 +170,7 @@ func (r *Reader) SetExpectedMax(expectedMax int64) {
 // https://docs.aws.amazon.com/AmazonS3/latest/userguide/checking-object-integrity.html
 // Returns ErrInvalidChecksum if a problem with the checksum is found.
 func (r *Reader) AddChecksum(req *http.Request, ignoreValue bool) error {
-	cs, err := GetContentChecksum(req)
+	cs, err := GetContentChecksum(req.Header)
 	if err != nil {
 		return ErrInvalidChecksum
 	}
@@ -181,6 +181,16 @@ func (r *Reader) AddChecksum(req *http.Request, ignoreValue bool) error {
 	if cs.Type.Trailing() {
 		r.trailer = req.Trailer
 	}
+	return r.AddNonTrailingChecksum(cs, ignoreValue)
+}
+
+// AddNonTrailingChecksum will add a checksum to the reader.
+// The checksum cannot be trailing.
+func (r *Reader) AddNonTrailingChecksum(cs *Checksum, ignoreValue bool) error {
+	if cs == nil {
+		return nil
+	}
+	r.contentHash = *cs
 	if ignoreValue {
 		// Do not validate, but allow for transfer
 		return nil