An Introduction to OpenSSL Programming, Part I of II
In this article, we've only scratched the surface of the issues involved with using OpenSSL. Here's a (nonexhaustive) list of additional issues.
A more sophisticated approach to checking server certificates against the server hostname is to use the X.509 subjectAltName extension. In order to make this check, you would need to extract this extension from the certificate and then check it against the hostname. Additionally, it would be nice to be able to check hostnames against wild-carded names in certificates.
Note that these applications handle errors simply by exiting with an error. A real application would, of course, be able to recognize errors and signal them to the user or some audit log rather than just exiting.
In the next article, we'll be discussing a number of advanced OpenSSL features, including session resumption, multiplexed and nonblocking I/O and client authentication.
Thanks to Lisa Dusseault, Steve Henson, Lutz Jaenicke and Ben Laurie for help with OpenSSL and review of this article.