Aug 232016

UnrealIRCd logoOne of the services I’ve been running on for years now has been the IRC server UnrealIRCd. It’s available for Linux, UNIX and also Windows, so it’s a pretty neat choice I think. A few days ago however, a user had notified me, that his client couldn’t connect when using SSL/TLS encryption after an update of the software. I’m pretty sure this was due to the OpenSSL developers disabling the SSL v3 protocol by default. So his client only had TLS and my old UnrealIRCd 3.x only had SSL v3 => handshake failure:

error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure

So what now? Just shoving a newer SSL library under my IRC server wouldn’t work in a stable fashion. So far, the only software I have ever seen which can be “magically” upgraded to modern protocols and ciphers this way was the Gene6 FTP server. All the way from OpenSSL 0.9.6 to 1.0.2. No idea how they did it.

Two options: Have users recompile their libraries and clients to enable SSL v3 (yeah, as if…), or try and backport a current (=2016-07-28) UnrealIRCd 4 to my server. One that supports both modern TLS v2 with modern ciphers as well as good old SSL v3, so legacy clients may connect in an encrypted fashion as well.

Why backport? Because it’s freaking Windows 2000 (and no, newer versions do *not* work), and UnrealIRCd dropped support for that, so I absolutely needed to recompile the server and several libraries it depends on. Now that was one wild ride for a user like me, I’m telling you.

Ah yes, this isn’t exactly a good step-by-step guide or anything, so in case you just wanna grab the files, scroll all the way down! If you want to know a few of the details… I don’t even remember all the things I did, but let’s see…


Here’s what you need:

  1. The Microsoft [Visual C++ 2008 runtime SP1 redistributable package] (only on the system where the server is supposed to run, not on the build system)
  2. Microsoft VisualStudio 2008 (I guess 2010 also works, as long as you have the v90 toolset available)
  3. Perl. I used [Strawberry Perl 5.24].
  4. The latest UnrealIRCd [dev package]. It’s for UnrealIRCd v3.4, but that doesn’t matter.
  5. The UnrealIRCd [source code]. I used the current/bugfixed version 4.0.5 for this build.
  6. A precompiled version of pcre2 supporting Windows 2000, I only found one eligible one [here]. (I failed to recompile/relink pcre2 properly, even with the version from the dev package :( )
  7. The stock [tre 0.8.0 library] source code, because it supports VS2008. The version shipped with the dev package doesn’t.
  8. The latest [OpenSSL library] source code, it’ll serve as a replacement for the older one shipped with the dev package.

If you cannot obtain Visual Studio 2008 via any (legal!) means, that’d probably mean you’re out of luck though. Luckily, I got all versions from Microsofts MSDNAA / DreamSpark program, but if you’re stuck on something like VS2012, 2013 or 2015, I cannot help you. Maybe this can still work out, but you’ll still need the 2008 version to get the v90 toolset (I guess, not an expert here…)


There are quite a few, but here are the ones that I still remember:

1.) Additional headers are required to link some of the software, there are free ones available. You can grab them [here]. Put them into the VC\include\ subdirectory of your Visual Studio 2008 installation folder. On top of those two, inttypes.h and stdint.h you’ll also need unistd.h, but that one’s easy: Just make a copy of io.h in that same folder and rename that copy to unistd.h and you’re done.

2.) First, cURL-SSL was built with the nmake options ENABLE_IPV6=no and ENABLE_IDN=no set. IPv6 support on Windows 2000 does exist by using an [experimental update], but it’s function calls are different than with Microsofts’ final version, so it’s unusable by most software. Also, IDN support is only available [for Windows XP and later], so internationalized domain names using non-ASCII characters don’t work. UnrealIRCd is to be linked against this version.

3.) tre replaced with latest stock tre 0.8.0 and recompiled, UnrealIRCd is to be linked against this build.

4.) Before building OpenSSL, it may need modifications to its makefile ms\ntdll.mak, which is generated by the ms\do_nasm step described in OpenSSLs INSTALL.W32, depending on your requirements. It is here where you can enable older, weaker ciphers and the older SSL v3/v2 protocols. Enable these deprecated version only if you absolutely need them!

Look for line 21 (Note, that the ^ line breaks aren’t in the file originally, it’s all in one line. I just added them here for readability purposes):

  1. CFLAG= /MD /Ox /O2 /Ob2 -DOPENSSL_THREADS  -DDSO_WIN32 -W3 -Gs0 -GF -Gy -nologo ^

You could replace this with the following, allowing weak ciphers and SSL v3, but not SSL v2 for example:

  1. #CFLAG= /MD /Ox /O2 /Ob2 -DOPENSSL_THREADS  -DDSO_WIN32 -W3 -Gs0 -GF -Gy -nologo ^
  8. CFLAG= /MD /Ox /O2 /Ob2 -DOPENSSL_THREADS  -DDSO_WIN32 -W3 -Gs0 -GF -Gy -nologo ^

Compile as shown in the documentation, and install somewhere.

5.) Before UnrealIRCd can use the new version of OpenSSL it may need modifications to match the ones patched into the OpenSSL makefile. By default, it will also block stuff like SSL v3. Enter its source tree and open ssl\ssl.c, then locate lines 245 and 321, which will look like this:

  1. SSL_CTX_set_options(ctx_server, SSL_OP_NO_SSLv3);

Just comment that out:

  1. /** SSL_CTX_set_options(ctx_server, SSL_OP_NO_SSLv3); **/

If you enabled SSLv2 as well and want the IRC server to be able to use it, do the same for lines 244 and 320, look for this…

  1. SSL_CTX_set_options(ctx_client, SSL_OP_NO_SSLv2);

…and comment it out again:

  1. /** SSL_CTX_set_options(ctx_client, SSL_OP_NO_SSLv2); **/

Now compile and link as shown in the UnrealIRCd documentation. Like the developers I’d recomment assembling a proper command line for this, as editing the makefile all the time can be cumbersome, especially if you’re running into trouble along the way.

What else?

Some of the VS project files may be preconfigured for platform toolsets you don’t have (like v100, v110, etc.) or may be set to produce a Debug build by default. Make sure you’re using only the v90 toolset and produce only Release builds. To learn how, check out the Visual Studio documentation online. It’s not that hard for the stuff you need to build with the GUI.

And here is the file:

Note that I may have done something horribly wrong along the way with this, because it really works only on Windows 2000. This is not how it should be. But launching it on a newer operating system yields something like this:

UnrealIRCd runtime error on anything greater than or equal to Windows XP

Yeah… umm… riiight…

And after pressing OK, this:

UnrealIRCd runtime error on anything greater than or equal to Windows XP #2


I searched for those errors on the web for a little, but couldn’t find anything that would’ve told me why it breaks like this on “modern” operating systems, yet still works on Windows 2000. Oh, the build system was XP x64 by the way. Well, it doesn’t really matter, the standard build of the developers works on XP+ anyway, and this works only on Windows 2000. Mission accomplished in any case.

In this incarnation, the server can support SSL v3 as well as TLS v1.2 protocols and supports the following ciphers:


The necessary tools for creating an SSL/TLS certificate and for installing a Windows service for the server are also included (openssl.exe, unrealsvc.exe).


UnrealIRCd and the software it was linked against in this case is released under the following licenses:

Any modifications to any of the software packages above as posted on this page are hereby licensed under the same license as the original software before modifications were applied. When downloading any unmodified source code, you’ll have to patch it yourself before building for a Windows 2000 platform target.

And what now?

Well, I guess my server supports IRC+TLS for all modern clients now, so yay! ;) URLs are the same as before: [irc+ssl://] with SSL v3/TLS v1.2 or [irc://] if you wish to connect without any encryption enabled, all plain text.

Sep 102013

NSA logoWith all that talk about the [National Security Agency] stealing our stuff (especially our most basic freedoms), it was time to look at a few things that Mr. Snowden and others before him have found out about how the NSA actually attempts to break certain encryption ciphers that are present in OpenSSLs and GnuTLSs cipher suites. Now that it has been clearly determined that a NSA listening post has been established in Vienna, Austria (protestors are on the scene), it may seem a good thing to look over a few details here. Especially now that the vulnerabilities are widely known and potentially exploitable by other perpetrators.

I am no cryptologist, so I won’t try to convince you that I understand this stuff. But from what I do understand, there is a side-channel attack vulnerability in certain block ciphers like for instance AES256-CBC-SHA or RSA-DES-CBC-SHA. I don’t know what it is exactly that’s vulnerable, but whoever may listen closely on one of the endpoints (client or server) of such a connection may determine crucial information by looking at the connections timing information, which is the side channel. Plus, there is another vulnerability concerning the Deflate protocol compression in TLS, which you shouldn’t confuse with stuff like mod_deflate in Apache, as this “Deflate” exists within the TLS protocol itself.

As most client systems – especially mobile operating systems like Android, iOS or Blackberry OS – are compromised and backdoored, it is quite possible that somebody is listening. I’m not saying “likely”, but possible. By hardening the server, the possibility of negotiating a vulnerable encrypted connection becomes zero – hopefully at least. :roll:

Ok, I’m not going to say “this is going to protect you from the NSA completely”, as nobody can truly know what they’re capable of. But it will make you more secure, as some vulnerable connections will no longer be allowed, and compromised/vulnerable clients are secure as long as they connect to a properly configured server. Of course you may also lock down the client by updating your browser for instance, as Firefox and Chrome have been known to be affected. But for now, the server-side.

I am going to discuss this for the Apache web server specifically, but it’s equally valid for other servers, as long as they’re appropriately configurable.Big Apache web server logoFirst, make sure your Apache is compatible with the SSL/TLS compression option SSLCompression [on|off]. Apache web servers starting from 2.2.24 or 2.4.3 should have this directive. Also, you should use [OpenSSL >=1.0] (link goes to the Win32 version, for *nix check your distributions package sources) to be able to use SSLCompression and also more modern TLSv1.1 and TLSv1.2 versions. If your server is new enough and properly SSL-enabled, please check your SSL configuration either in httpd.conf or in a separate ssl.conf included in httpd.conf, which is what some installers use as a default. You will need to change the SSLCipherSuite directive to not allow any vulnerable block ciphers, disable SSL/TLS protocol compression, and a few things more. Also make sure NOT to load mod_deflate, as this opens up similar loopholes as the default for the SSL/TLS protocols themselves do!

Edit: Please note that mixing Win32 versions of OpenSSL >=1.0 with the standard Apache version from will cause trouble, so a drop-in replacement is not recommended for several reasons, two being that that Apache version is linked against OpenSSL 0.9.8* (breaking TLS v1.1/1.2) and also built with a VC6 compiler, where OpenSSL >=1.0 is built with at least a VC9 compiler. Trying to run all VC9 binaries (Apache+PHP+SSL) only works on NT 5.1+ (Windows XP/2003 or newer), so if you’re on Win2000 you’ll be stuck with older binaries or you’ll need to accept stability and performance issues.

Edit 2: I now found out that the latest version of OpenSSL 0.9.8, namely 0.9.8y also supports switching off SSL/TLS deflate compression. That means you can somewhat safely use 0.9.8y which is bundled with the latest Apache 2.2 release too. It won’t give you TLS v1.1/1.2, but leaves you with a few safe ciphers at least!

See here:

SSLEngine On
SSLCertificateFile <path to your certificate>
SSLCertificateKeyFile <path to your private key>
ServerName <your server name:ssl port>
SSLCompression off
SSLHonorCipherOrder on
SSLProtocol All -SSLv2

This could even make you eligible for a VISA/Mastercard PCI certification if need be. This disables all known vulnerable block ciphers and said compression. On top of that, make sure that you comment out the loading of mod_deflate if not already done:

# LoadModule mod_deflate modules/

Now restart your webserver and enjoy!

The same thing can of course be done for mail servers, FTP servers, IRC servers and so on. All that is required is a proper configurability and compatibility with secure libraries like OpenSSL >=1.0 or at least 0.9.8y. If your server can do that, it can also be secured against these modern side channel attacks!

If you wish to verify the safety specifically against BEAST/CRIME attack vectors, you may want to check out [this tool right here]. It’s available as a Java program, .Net/C# program and source code. For the Java version, just run it like this:

java -jar TestSSLServer.jar <server host name> <server port>

This will tell you whether your server supports deflate, which cipher suites it supports and whether it’s BEAST or CRIME vulnerable. A nice point to start! For the client side, a similar cipher suite configuration may be possible to ensure the client won’t allow the negotiation of a vulnerable connection. Just updating your software may be an easier way in certain situations of course. A good looking output of that tool might appear somewhat like this:

Supported versions: SSLv3 TLSv1.0 TLSv1.1 TLSv1.2
Deflate compression: no
Supported cipher suites (ORDER IS NOT SIGNIFICANT):
  (TLSv1.0: idem)
  (TLSv1.1: idem)
Server certificate(s):
  2a2bf5d7cdd54df648e074343450e2942770ab6ff0:,, OU=MYSERVER,, L=My City, ST=My County, C=COM
Minimal encryption strength:     strong encryption (96-bit or more)
Achievable encryption strength:  strong encryption (96-bit or more)
BEAST status: protected
CRIME status: protected

Plus, as always: Using open source software may give you an advantage here, as you can at least reduce the chances of inviting a backdoor eavesdropping on your connections onto your system. As for smartphones: Better downgrade to Symbian or just throw them away altogether, just like your tablets (yeah, that’s not the most useful piece of advice, I know…).

Update: And here a little something for your SSL-enabled UnrealIRCD IRC server.

UnrealIRCD logoThis IRC server has a directive called server-cipher-list in the context set::ssl, so it’s set::ssl::server-cipher-list. Here an example configuration, all the non-SSL specific stuff has been removed:

set {
  ssl { 
    trusted-ca-file "your-ca-cert.crt";
    certificate "your-server-cert.pem";
    key "your-server-key.pem";
    renegotiate-bytes "64m";
    renegotiate-time "10h";

Update 2: And some more from the Gene6 FTP server, which is not open source, but still extremely configurable. Just drop in OpenSSL >=1.0 (libeay32.dll, ssleay32.dll, libssl32.dll) as a replacement, and add the following line to your settings.ini files for SSL-enabled FTP domains, you can find the files in the Accounts\yourdomainname subfolders of your G6 FTP installation:

Gene6 FTP server logo


With that and those OpenSSL >=1.0 libraries, your G6 FTP server is now fully TLSv1.2 compliant and will use only safe ciphers!

Finally: As I am not the most competent user in the field of connection-oriented encryption, please just post a comment if you find some incorrect or missing information, thank you!