TLS in poezio

Security of the connection

Enabling or disabling TLS

Starting from version 0.8, poezio is configured to reject unencrypted connections by default, in accordance to the TLS manifesto. Users can still allow unencrypted connections by setting the force_encryption option to false.

If you cannot connect to your server, maybe it does not allow encrypted connections, in which case you should reconfigure it if it is yours, or contact your admin to let him know he should try to protect your privacy and credentials, at least a little.

Ciphers

From the version 0.8, poezio offers the possibility to define your own set of ciphers.

You can set this with the ciphers option, the default for poezio being HIGH+kEDH:HIGH+kEECDH:HIGH:!PSK:!SRP:!3DES:!aNULL. You can check what ciphers are enabled by that list by running the command openssl ciphers -v 'cipher list'. The default list prioritizes Forward Secrecy and does not have any cipher suite providing less than 128 bits of security.

You should change this if you either cannot connect to your server (but in this case, you should notify the administrator that his XMPP server configuration is probably not great), or if you want to be even more restrictive (only allowing 256 bits of security and forward secrecy, for example).

For example, gmail.com (and subsequent XMPP services) only support RC4-MD5 and RC4-SHA, so you will want to set the option to RC4 (or the default with :RC4 appended, just in case they upgrade their service, though that is very unlikely). Please consider moving to a better XMPP service provider.

Certificate validation

Starting from version 0.7.5, poezio offers some options to check the validity of a X.509 certificate.

TOFU

The default handling method is the TOFU/TUFU method. At your first connection, poezio will save the hash of the certificate received, and will compare the received one and the first one for the next connections.

If you are paranoid (or run poezio for the first time in an unsafe environment), you can set the certificate value of your config file yourself (the hash, not colon-separated).

If the certificate is not the same, poezio will show an error message and wait for confirmation:

Warning message

If you press y, the change is validated an poezio will match the next certs with the accepted one.

If you press n, you will get the confirmation that the change has been refused, and you will be disconnected.

CA-Based

If you are connecting to a large server that has several front-facing endpoints, you might be bothered by having to validate the change each time, and you may want to check only if it the same authority delivered the certificate.

You can then set the ca_cert_path option to the path of a file containing the validation chain in PEM format ; those certificates are usually in /usr/share/ca-certificates/ but it may vary depending of your distribution.

If the authority does not match when connecting, you should be disconnected.

None

If you do not want to bother with certificate validation at all (which can be the case when you run poezio on the same computer as your jabber server), you can set the ignore_certificate value to true, and let the ca_cert_path option empty (or even remove it).

Warning

Only do this if you know what you are doing, or you will be open to Man in The Middle attacks!

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