The Portuguese Bar Association (Ordem dos Advogados – OA) offers free e-mail addresses to its associates. OA's IT department opted to support this service in the Unix platform (historically more reliable) which was outside the scope of experience of the company that was developing their Web site.
We were therefore contacted to develop part of OA's portal (Web site) where it concerned e-mail management, and the respective integration with other authentication systems already performed in Windows.
The platform of choice was obviously PHP even though there was the need to create some C code for privilege escalation. Part of this code was installed in Windows servers for remote user validation. More recently validation was based on single-sign-on by sharing cookies and XML messages between servers.
The security of lawyers' e-mails is absolutely crucial. The suits that each lawyer may be working on are confidential by law and should be treated as such.
We took great care with the code that runs with special permissions. This is the part of the project that could not be compromised in any way.
For that effect, we wrote this code in the C language, with special care to avoid buffer overflows which frequently cause security problems. This C code is also very demanding on its inputs, making sure it only does what is intended to do, and nothing more (for instance, it can only change lawyers' e-mails and can never change system e-mails). This code is so demanding in this issue that we've been forced to update it twice due to the increase of the allowed ranges for e-mail addresses.
This code further makes hackers' work more difficult by not providing any usage help or problem diagnostic. Should there be any processing errors or hacking attempts, the code shows the same vague error message and OA's portal informs the user.
The security of the Unix servers themselves was not in our charge.