sigv4: Trim and shrink spaces in headers values (#3162)

cmd/signature-v4-utils.go

@@ -157,3 +157,19 @@ func extractSignedHeaders(signedHeaders []string, reqHeaders http.Header) (http.
 
 	return extractedSignedHeaders, ErrNone
 }
+
+// Trim leading and trailing spaces and replace sequential spaces with one space, following Trimall()
+// in http://docs.aws.amazon.com/general/latest/gr/sigv4-create-canonical-request.html
+func signV4TrimAll(input string) string {
+	// Remove all whitespaces first
+	cleanWhiteSpaces := func(r rune) rune {
+		switch r {
+		case '\t', '\n', '\u000b', '\r', '\f':
+			return ' '
+		}
+		return r
+	}
+	input = strings.Map(cleanWhiteSpaces, input)
+	// Compress adjacent spaces to one space and return
+	return strings.Join(strings.Fields(input), " ")
+}