Presign-v4: Allow requests that were signed slightly ahead of the current time. (#3435)

cmd/signature-v4.go

@@ -250,7 +250,9 @@ func doesPresignedSignatureMatch(hashedPayload string, r *http.Request, region s
 
 	query.Set("X-Amz-Algorithm", signV4Algorithm)
 
-	if pSignValues.Date.After(time.Now().UTC()) {
+	// If the host which signed the request is slightly ahead in time (by less than globalMaxSkewTime) the
+	// request should still be allowed.
+	if pSignValues.Date.After(time.Now().UTC().Add(globalMaxSkewTime)) {
 		return ErrRequestNotReadyYet
 	}