I have created my SSL certificate using Selssl7.exe on server1 but used Cn as Server2 and hosted the certificate on server2. I started to get a certificate error when browsing from linux firefox saying:
This certificate is invalid, the certificate is not trusted and is self signed, the certificate is only valid for server1
But when I browse the URL from Windows IE I just get the regular error saying that it’s not trusted and I can easily add it to exceptions.
Can we use self-signed certificates generated on server1 on a different servers?
You can and you may but you are pretty much undermining each and every aspect of authenticity by doing so.
A self-signed certificate is generally a problem because other users will not know this certificate in advance. So their browser dutifully issues a warning. That’s why you have to pay for TLS certificates that will be recognized – they are issued by CAs whose certificates are contained in the default trust store of your browser. CAs had to pay to “be part of the club”, but otherwise, anyone can create certificates. It’s just the matter of being recognized by default settings.
But you open another hole by reusing a certificate that was issued for a dedicated server on a different server. TLS certificates’ subject distinguished names must match the host name of the server they are deployed on. This is mandated by the TLS spec because this is the only effective measure to prevent man-in-the-middle attacks when using TLS. After you open a TLS connection to a server, your code will check whether the host name that you are connected to matches the subject DN of the server’s certificate that was sent. Only if it does you can be sure to be talking to the right server.
So, in conclusion, if you reuse a server certificate on a different host, then you are severely impacting the security of TLS. It’s still possible, sure, but if you cripple security to this extent, then you are probably better off using plain HTTP in the first place.