Category Archives: Linux

How to use OpenVPN over an IP over ICMP tunnel (Hans)

Introduction The very first question may is why to tunnel IP over ICMP at all? Sometimes you may find yourself in a situation where you have network, but no access to the Internet because of annoying restrictions. That f.ex. could be a proxy which requires authentication, a captive portal like in hotels or the ports you need simply are not … Continue reading

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Setup an OpenVPN server with certificate and two-factor authentication on CentOS 7

Introduction My goal was to have an OpenVPN server running, to which i can connect using different ports and by pipping it over an IP over ICMP tunnel (the latter will follow in another post). Ports i want to use: 1194/udp – The default OpenVPN port 53/udp – If im lucky and the network has DNS open by default… 1195/udp … Continue reading

Posted in CentOS, Firewalls, Linux, OpenVPN, Security, VPN | Tagged , , | 1 Comment

Check if the certificate of a domain was revoked

Just had the need to quickly check if the certificate of a domain was revoked or not, and found this tutorial: ¬†OpenSSL: Manually verify a certificate against a CRL Well done, but two problems: If the server doesn’t send all certificates (including the root CA), the verify process will fail Too much to type… So i quickly created a bash … Continue reading

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CentOS – Set machines IPv6 source address

If you have configured multiple IPv6 addresses within a CentOS machine, it shows the strange behavior that it sets the last IPv6 address in IPV6ADDR_SECONDARIES as its default source address for outgoing connections, which can end up in quite annoying¬†problems. For example, firewalls may expects the main IPv6 address and not a secondary, which changes if you add another one … Continue reading

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Quick tip: Download all pdf files on a website

After RedHat Enterprise Linux 7 was released this week, which has a bunch of very cool features by the way, I wanted to download all the new documentations as PDF to put them on my iPad. But right-click each of the 30 links and click “save as” definitely wasn’t the way to go. Administrators are lazy guys… URL of the … Continue reading

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