CertificateException: No name matching ssl.someUrl.de found

In Java 8 you can skip server name checking with the following code:

HttpsURLConnection.setDefaultHostnameVerifier ((hostname, session) -> true);

However this should be used only in development!

It looks like the certificate of the server you are trying to connect to doesn't match its hostname.

When an HTTPS client connects to a server, it verifies that the hostname in the certificate matches the hostname of the server. It's not enough for a certificate to be trusted, it has to match the server you want to talk to too. (As an analogy, even if you trust a passport to be legitimate, you still have to check that it's the one for the person you want to talk to, not just any passport you would trust to be legitimate.)

In HTTP, this is done by checking that:

• the certificate contains a DNS subject alternative name (this is a standard extension) entry matching the hostname;

• failing that, the last CN of your subject distinguished name (this is the main name if you want) matches the hostname. (See RFC 2818.)

It's hard to tell what the subject alternative name is without having the certificate (although, if you connect with your browser and check its content in more details, you should be able to see it.) The subject distinguished name seems to be:

[email protected], CN=plesk, OU=Plesk, O=Parallels, L=Herndon, ST=Virginia, C=US

(It would thus need to be CN=ssl.someUrl.de instead of CN=plesk, if you don't have a subject alternative name with DNS:ssl.someUrl.de already; my guess is that you don't.)

You may be able to bypass the hostname verification using HttpsURLConnection.setHostnameVerifier(..). It shouldn't be too hard to write a custom HostnameVerifier that bybasses the verification, although I would suggest doing it only when the certificate its the one concerned here specifically. You should be able to get that using the SSLSession argument and its getPeerCertificates() method.

(In addition, you don't need to set the javax.net.ssl.* properties the way you've done it, since you're using the default values anyway.)

Alternatively, if you have control over the server you're connecting to and its certificate, you can create a certificate of it that matches the naming rules above (CN should be sufficient, although subject alternative name is an improvement). If a self-signed certificate is good enough for what you name, make sure its common name (CN) is the host name you're trying to talk to (no the full URL, just the hostname).