Problem - Kevin Tafuro

Chapter CHAPTER 9 9
Networking
Today, most applications perform some type of network activity. Unfortunately,
many programmers don’t know how to access a network securely. The recipes in this
chapter aim to help you use a network in your application. To many developers, network
security from the application standpoint means using the Secure Sockets Layer
(SSL), but SSL isn’t a magic solution. SSL can be difficult to use properly; in many
cases, it is overkill, and in a few cases, it is insufficient. This chapter presents recipes
for using OpenSSLto build SSL-enabled clients and servers and recipes for network
and interprocess communication without SSL.
On the Windows platform, with the exception of SSLover HTTP (which we cover in
Recipe 9.4), we’ve chosen to limit the SSL-specific recipes to OpenSSL, which is
freely available and portable to a wide range of platforms, Windows included.
On Windows systems, Microsoft provides access to its SSLimplementation through
the Security Support Provider Interface (SSPI). SSPI is well documented, but unfortunately,
the use of SSLis not. What’s more unfortunate is that implementing an SSLenabled
client or server with SSPI on Windows is considerably more complex than
using OpenSSL(which is saying quite a lot). The SSPI interface to SSLis surprisingly
low-level, requiring programs that use it to do much of the work of exchanging protocol
messages themselves. Because SSLis difficult to use properly, it is desirable to
mask protocol details with a high-level implementation (such as OpenSSL). We
therefore avoid the SSPI interface to SSL altogether.
If you are interested in finding out more about SSPI and the SSLinterface, we recommend
that you consult the Microsoft Developer’s Network (MSDN) and the samples
that are included with the Microsoft Windows Platform SDK, which is available
from Microsoft on the Internet at http://www.microsoft.com/msdownload/platformsdk/sdkupdate/.
The relevant example code can be found in the directory
Microsoft SDK\Samples\Security\SSPI\SSL from wherever you install it on your system
(normally in \Program Files on your boot drive).
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