[Mono-list] Private key failure SslStream based authentication on Mono/UbuntuLinux

[Sebastien Pouliot]

On Fri, 2011-05-27 at 09:49 -0700, Chirag Patel wrote:
> Hello Sebastien,
> 
> I see some progress. The progress came out of using X509Certificate2
> on my linux server.
> So, private key exception is gone.

Great :-)

> Now I face another problem on client side (on the code that has run
> fine on windows for 1 year).

Still on Windows / .NET ?
or running Mono ? 

If the later, windows or linux ? version ? ...

>                 _sslstream = new SslStream(_tcpclient.GetStream(), false,
>                     callback, null);
>                 _sslstream.AuthenticateAsClient("", _certs, SslProtocols.Ssl3,
>                     false);
> The application stalls at AuthenticateAsClient. Never goes forward.
> And based on Debug output, I see that it has server's Remote
> Certificate name mismatch issue.
> (I think it has problem identifying server as what the server says it is)

If you're using client certificates then you'll need to make sure they
(the client certs) are signed by a certificate root that is trusted by
the server.

> Here's what I tried after that.
> I ran my server on windows and linux both to get the Subject of the
> certificate on both sides. They were exactly the same.

Subject name must match the server name, e.g. DNS lookup, so the client
can be sure its talking to the right host (e.g. avoid MitM)

> 
> Could you think of anything else?

iirc old Mono releases had some limitations when subject names had
wildcards, e.g. CN=*.mysite.com

> I have also included some inline messages out of curiosity.
> 
> Thanks
> 
> On Thu, May 26, 2011 at 1:31 PM, Sebastien Pouliot
> <sebastien.pouliot at gmail.com> wrote:
> > Hello Chirag,
> >
> > On Thu, 2011-05-26 at 13:17 -0700, Chirag Patel wrote:
> >> Hi All,
> >>
> >> I am working on migrating my .NET based windows service to mono and linux.
> >>
> >> I am using SslStream and its BeginAuthenticateServer method.
> >>
> >> Exception: The authentication or decryption has failed.
> >> Inner Exception: Server certificate Private Key unavailable.
> >> at Mono.Security.Protocol.Tls.Handshake.Server.TlsClientKeyExchange.ProcessAsSsl3
> >> () [0x00000] in <filename unknown>:0
> >>   at Mono.Security.Protocol.Tls.Handshake.HandshakeMessage.Process ()
> >> [0x00000] in <filename unknown>:0
> >>   at (wrapper remoting-invoke-with-check)
> >> Mono.Security.Protocol.Tls.Handshake.HandshakeMessage:Process ()
> >>   at Mono.Security.Protocol.Tls.ServerRecordProtocol.ProcessHandshakeMessage
> >> (Mono.Security.Protocol.Tls.TlsStream handMsg) [0x00000] in <filename
> >> unknown>:0
> >>   at Mono.Security.Protocol.Tls.RecordProtocol.InternalReceiveRecordCallback
> >> (IAsyncResult asyncResult) [0x00000] in <filename unknown>:0
> >>
> >> [http://lists.ximian.com/pipermail/mono-list/2007-February/034278.html]
> >>
> >> I see that Sebastien has pointed out using alternate
> >> Mono.Security.Protocol.Tls.SslServerStream class,
> >> and its delegate to fetch private key. (because of difference between
> >> linux vs. windows handling of certs.)
> >
> > That's an alternative, not the best, but it has quite a bit of source
> > code using it (e.g. xsp) and is easy to adapt (to whatever source you're
> > loading the private key from).
> >
> >> What is next? Just use the server certificate from SslServerStream
> >> property, and dispose the stream?
> >
> > No, if you start using SslServerStream then you'll need to use it
> > completely (forget SslStream).
> >
> >> And continue using original Microsoft SslStream?
> >
> > That's another choice and needs a different solution :)
> >
> >> Or
> >> I just have to use Mono's SslServerStream and manually write read
> >> "any/irrelevant" data to proceed with authentication?
> >
> > No
> If I were to use SslServerStream, what Logic would replace
> SslStream::BeginAuthenticateAsServer?

I don't recall. Best to look at Mono's source code for SslStream :-)

> 
> >
> >> I am using PFX file. I did include private key. So, Do I even need to
> >> use the delegate to load private key separately??
> >> (How can I debug whether the loaded X509Certificate instance has the
> >> private key loaded.)
> >>
> >> I have also tried this with a Verisign issued real certificate. But
> >> since that entire thing including export was done on Windows, I tried
> >> my code with self-signed (linux - openssl) cert.
> >
> > Two things comes to mind:
> >
> > 1. make sure Mono can read your PKCS12 file (e.g. load it using
> > X509Certificate2 and dump its properties). This is important because
> > Mono's ASN.1 implementation does not support "indefinite length" and
> > some tools generates them.
> >
> > 2. When using SslStream + PKCS12 also make sure you're using
> > X509Certificate2 (***2*** not X509Certificate). This will ensure the
> > private key, if present, will be loaded in memory and will let SslStream
> > use it.
> >
> I think (2) did solve the problem: Private key unavailable.
> I mentioned I load cert from PFX file. I wonder what's the ideal way
> to handle certificates in mono+linux?

Yes, it helps for self-contained applications...

> I see /etc/ssl...but that doesn't provide exact facilities like
> microsoft certificate store. I used a tool called XCA on ubuntu, but
> it creates its own database file.

... since there's no single standard as you found out ;-)

Sebastien