Things I Learned While Debugging an SSL Issue

• SSL is sometimes actually TLS. SSL is apparently on the way out, though TLS is only supported in a subset of common browsers. Fortunately, both use the same kind of certificate, so it's mostly transparent.
• Java 1.6u17 removed SSL client support for MD2-signed root certificates. Except it sometimes didn't. Some u17 installs worked for me, some failed. 1.6u19 failed every time. If you have a Java client connecting to a SSL server, make sure that the server certificate was generated against a SHA1-signed root certificate.
• WireShark will analyze both SSL and TLS. If there's any confusion about what is coming from the server, WireShark can help you figure it out.
• The server sends the whole certificate chain to the client. I had thought that this was the case, but I had a hard time finding the documentation that spells it out. In the end, I used WireShark to find out.
• Web browsers sometimes lie. When I would ask the web browser for the certificate chain, it would tell me something different from what the server actually sent. The root certificate from the server was signed with SHA1, but the browser would tell me that it was signed with MD2. This occurred in Internet Explorer, Firefox, and Safari. This was also a red herring that caused me to waste a lot of time.
• Make sure you are looking at the right server. I had made an assumption about how the Java client software talked to the server, and that assumption was incorrect. In the end, the problematic certificate was on a different server altogether. Go figure.

Arduino librxtxserial.jnilib on MacOS

After re-installing MacOS from scratch, I found that I was having problems launching Arduino. I got the following error:

In order to solve this, I followed the instructions at rancidbacon.com. The solution was to use Finder to configure the application to launch in 32-bit mode. I quickly looked to see if I could modify the Info.plist file to enforce this behavior, but I don't see any way to do that.

Another solution from technobabble is to replace the library inside the Arduino app bundle with a 1.6 compatible version.

JTextArea and javax.swing.text.Document

I was playing with a JTextArea in my Swing project today. My underlying data is actually quite simple (a list of names and quotes), and my JTextArea is read-only. Therefore, I decided to try to make my own class that implements javax.swing.text.Document, but whose internal structure more closely models my real... model.

I had a hard time getting started. From poking around in Document's Javadocs and in related Java source code, it appears that Document is a very general concept. It seems to have originally been intended to model an SGML document's structure - or something like that. The Document interface lets you navigate a tree structure that represents the document. However, when it comes to modeling data for a JTextArea, things are much simpler. Instead, it appears that JTextComponent (the base class of JTextArea) assumes that the Document models a list of lines of text. That is to say, it seems to expect that the Document has one root element which contains a separate element for each line. This is most obvious from JTextArea's getLineCount() method:

public int getLineCount() {
    Element map = getDocument().getDefaultRootElement();
    return map.getElementCount();
}

Now, the problem with all of this is that Document is a pretty complicated interface. On top of that, since SGML is a tree-oriented structure, it is not quite intuitive to map the concepts of "stream of text" to "tree-shaped structure". More problematically, I didn't see anything in the documentation to even begin to shed some light on this unspoken relationship. I stumbled upon it while examining stack traces from my first cut. I vaguely recall this being much easier in the little bit of Cocoa that I dabbled in, but I can't be sure. Maybe I'm just crazy - there are certainly a number of other concrete, Document-derived classes out there.

So remember, if you want to implement Document, make sure to model your document as a list of lines of text.