add 2015-02-24-znc160-ssl.md

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_posts/2015-02-24-znc160-ssl.md

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+---
+layout: post
+comments: true
+title: "ZNC 1.6.0 & SSL certificate verification"
+category: [english]
+tags: [irc, english]
+---
+
+**TL;DR: if you don't verify SSL certificates, don't use SSL!**
+
+ZNC 1.6.0 was released on 2015-02-12 21:05:48Z. It brings multiple
+improvements such as taking IP addresses from round-robins randomly instead
+of always resolving them into same IP and most notably it actually verifies
+SSL certificates.
+
+* [Changelog](http://wiki.znc.in/ChangeLog/1.6.0)
+
+ZNC 1.6.0 also doesn't have option to blindly accept certificates, which
+would be stupid, but sadly
+[Quakenet is right about most of people just accepting certificates blindly](https://www.quakenet.org/articles/99-trust-is-not-transitive-or-why-irc-over-ssl-is-pointless)
+as people are asking how to disable the SSL certificate verification on
+\#znc at freenode a lot.
+
+Some people even wrote [a patch and scripts to disable the verification.](https://gist.github.com/KindOne-/52cfade7b937ee8b4c37)
+
+And to the subject
+------------------
+
+If you don't verify SSL certificates, you only have a false sense of
+security as you let anyone between your ZNC and the IRC network. This is
+called as [Man-in the middle (or shortly MITM) attack.](https://en.wikipedia.org/wiki/Man-in-the-middle_attack)
+There are also people asking for ZNC to trust the certificate for the
+first time and then be alerted if the certificate changes. What if the
+MITM is there during your first connection attempt and then you are
+alerted when the real IRC server gives you wrong certificate?
+
+So what is the correct way?
+---------------------------
+
+* Check the website of your IRC network in case the fingerprints are
+  listed on their website.
+* Try asking the operators of your IRC network somewhere else if you know
+  them (like another network or email).
+* This might not be so recommended, but also check the fingerprints from
+  multiple locations.
+
+> But the IRC network has hundreds of servers with different certificates!
+
+In this case do what was recommened before ZNC 1.6.0, check some of the
+servers that are geographically close to you and use them.
+
+## Checking the fingerprint from multiple locations
+
+I have shell function (which you can find later on this page) which I run
+from multiple places:
+
+* my home, Kotka, Finland
+* [Kapsi (shell)](https://www.kapsi.fi/english.html), somewhere in Finland
+* my VPS, DigitalOcean, London, the UK
+
+```bash
+# Get server SSL certificate fingerprint in MD5, SHA1 and SHA256.
+# Note that OpenSSL doesn't support IPv6 at time of writing (2015-01-13).
+serversslcertfp() {
+    SSSLCFFN="/tmp/$(date -Is).pem"
+    openssl s_client -showcerts -connect $1 < /dev/null|tee $SSSLCFFN
+    cat $SSSLCFFN|openssl x509 -md5 -fingerprint -noout
+    cat $SSSLCFFN|openssl x509 -sha1 -fingerprint -noout
+    cat $SSSLCFFN|openssl x509 -sha256 -fingerprint -noout
+    rm $SSSLCFFN
+}
+```
+
+I hope this article has helped you to understand the issues with blindly
+accepting SSL certificates or at least to understand that *if you don't
+want to verify SSL certificates, don't use SSL.*