> if you have two servers behind a load-balancer, you have to make sure
> that once a client starts an HTTPS conversation with one server, all
> subsequent requests are served by the same server. 

True. AFAIK there are no versions of MSIE that correctly support the
keepalive setting, to unless you are willing to put up with the 
mysterious-1-page-in-5-is-just-blank problem you have to turn keepalive
off, and every request gets renegotiated.


-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]] On Behalf Of Owen Boyle
Sent: 10 May 2002 09:02
To: [EMAIL PROTECTED]
Subject: Re: Certificates and Apache/modssl


Greg Jones wrote:
> 
> All-
> 
> We are planning on using commercial load balancing software for two
servers
> running apache with modssl. Does Apache with modssl require that each
server
> have its own certificate or can I use the same certificate on both
servers
> since they'll be answering to the same virtual ip? Also, will my
certificate
> be based on the virtual ip or the ip of the server. Users will always
get to
> the web servers via virtual IP.

The certificate is assigned to a fully-qualified domain name, not to an
IP address. The idea is that when the browser goes to www.acme.com, it
expects to see a certificate containing "www.acme.com" - thus proving
that the site is really www.acme.com. This is authentication which is
the second but equally important aspect of SSL that everyone forgets
about... (the first aspect is encryption).

Therefore, as long as both your servers are serving the same site, they
can have the same certificate (indeed, they *should* have the same
cert).

There is one other problem, however. Remember that the
public-key/private-key encryption is used only to negotiate the
session-key. Once that has been established, the client and server
communicate using the session-key and the certificate is forgotten. Now,
if you have two servers behind a load-balancer, you have to make sure
that once a client starts an HTTPS conversation with one server, all
subsequent requests are served by the same server. In other words, if
the session-key negotiation takes place on one server but the next
request comes in to the second server, it will be encrypted with a key
known only to the first server. I guess the solution would be to ensure
requests are split on a client basis rather than request basis in the
load balancer.

Rgds,

Owen Boyle
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Apache Interface to OpenSSL (mod_ssl)                   www.modssl.org
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