When parsing a truncated clearsigned message (one that includes the opening header but no armored data), the existing implementation of clearsign.Decode() hangs in an infinite loop. This commit changes Decode() to detect the end of the buffer and return as if no clearsigned message was found. Change-Id: Ibc85b29a08d22868470f48fe300bf8fcb4749768 Reviewed-on: https://go-review.googlesource.com/17693 Reviewed-by: Adam Langley <agl@golang.org>