[security-dev 00228]: Re: X509KeyManager alias choice based on temporary socket

[Andrew Fan]

Bruno Harbulot,

The issue has been reported as a bug. If you cannot wait for a fix, 
please try a workaround as described bellow.

The SSLServerSocketImpl.checkEnabledSuites() is called before a socket 
connection accept(i.e, no socket created at the call time), so a 
temporary socket generated in order to build a context to check enabled 
cipher suites. However, for your requirements, the solution runs into 
the corner, and broke to find a proper cipher suite.

The SunJSSE current implementation will generated the socket on in a 
wildcard address. As a workaround, the customized chooseServerAlias() 
could regarded the wildcard address as one of your actual address, (by 
checking socket.getLocalAddress().isAnyLocalAddress).

Once the SSLServerSocketImpl.checkEnabledSuites() passed, the following 
accepted socket will use the actual socket, the behavior is just as your 
expect.

Regards,
Andrew

Bruno Harbulot wrote:
> Hello,
>
> I'm trying to use an X509KeyManager to choose which certificate a 
> server presents depending on which IP address the socket is listening on.
>
> Let's suppose I have two certificates (+private keys) for 
> host1.example.org (10.0.0.1) and host2.example.com (10.0.0.2), and 
> that the clients are going to check the name of the hostname against 
> the name in the certificate. This should work fine since there are two 
> distinct IP addresses, one for each certificate.
>
> The Java server I'm running is configured with a single SSLContext, 
> which is set up with a KeyStore that contains two pairs of private 
> keys and certificates. This SSLContext is also set up to use a custom 
> X509KeyManager, which I was planning to use to choose which of the two 
> aliases (and therefore certificates) should be used depending on the 
> socket.
> This server starts up two SSLServerSockets, one with local address 
> 10.0.0.1 and the other one with local address 10.0.0.2 (same port, but 
> this shouldn't really matter).
>
> I initially thought that "chooseServerAlias(String keyType, 
> Principal[] issuers, Socket socket)" would give me the server socket 
> used and thus I would be able to pick the alias based on 
> "socket.getLocalAddress()".
>
> Unfortunately, it turns out that the socket passed to 
> chooseServerAlias is not the socket that is actually used. Its address 
> is always 0.0.0.0, regardless of the IP address the actual listening 
> socket has been bound to.
>
> I've traced the call to chooseServerAlias to:
> com.sun.net.ssl.internal.ssl.ServerHandshaker.setupPrivateKeyAndChain(ServerHandshaker.java:843) 
>
>     at 
> com.sun.net.ssl.internal.ssl.ServerHandshaker.trySetCipherSuite(ServerHandshaker.java:686) 
>
>     at 
> com.sun.net.ssl.internal.ssl.SSLServerSocketImpl.checkEnabledSuites(SSLServerSocketImpl.java:292) 
>
>     at 
> com.sun.net.ssl.internal.ssl.SSLServerSocketImpl.accept(SSLServerSocketImpl.java:253) 
>
>
>
>
> Looking at com.sun.net.ssl.internal.ssl.SSLServerSocketImpl (in 
> openjdk-6-src-b10_30_may_2008.tar.gz and 
> openjdk-7-ea-src-b30-03_jul_2008.zip), it turns out that the choice of 
> the certificate is based on a temporary socket, which is initialised 
> with settings based on the actual socket (cipher suites, etc.), but 
> not the local address or port. (Code fragment at the end of this e-mail.)
>
>
> It is done by design? Any idea how it would be possible to choose a 
> certificate based on which IP address is used otherwise?
>
>
> Best wishes,
>
> Bruno.
>
>
>
>
> ====== This is a short extract of 
> com.sun.net.ssl.internal.ssl.SSLServerSocketImpl (line count will 
> differ depending on the version, but it's towards the end of the file) 
> =====
>
>     /*
>      * This is a sometimes helpful diagnostic check that is performed
>      * once for each ServerSocket to verify that the initial set of
>      * enabled suites are capable of supporting a successful handshake.
>      */
>     private void checkEnabledSuites() throws IOException {
>         //
>         // We want to report an error if no cipher suites were actually
>         // enabled, since this is an error users are known to make.  Then
>         // they get vastly confused by having clients report an error!
>         //
>         synchronized (this) {
>             if (checkedEnabled) {
>                 return;
>             }
>             if (useServerMode == false) {
>                 return;
>             }
>
>             SSLSocketImpl tmp = new SSLSocketImpl(sslContext, 
> useServerMode,
>                          enabledCipherSuites, doClientAuth,
>                          enableSessionCreation, enabledProtocols);
>
>             ServerHandshaker handshaker = tmp.getServerHandshaker();
>
>             for (Iterator t = enabledCipherSuites.iterator(); 
> t.hasNext(); ) {
>                 CipherSuite suite = (CipherSuite)t.next();
>                 if (handshaker.trySetCipherSuite(suite)) {
>                     checkedEnabled = true;
>                     return;
>                 }
>             }
>