107 lines
3.9 KiB
ReStructuredText
107 lines
3.9 KiB
ReStructuredText
TLS in poezio
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=============
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.. _security settings:
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Security of the connection
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~~~~~~~~~~~~~~~~~~~~~~~~~~
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Enabling or disabling TLS
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-------------------------
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Starting from version 0.8, poezio is configured to reject unencrypted connections
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by default, in accordance to the `TLS manifesto`_. Users can still allow
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unencrypted connections by setting the :term:`force_encryption` option to false.
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If you cannot connect to your server, maybe it does not allow encrypted connections,
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in which case you should reconfigure it if it is yours, or contact your admin
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to let him know he should try to protect your privacy and credentials, at least
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a little.
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.. _ciphers:
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Ciphers
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-------
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From the version 0.8, poezio offers the possibility to define your own set of
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ciphers.
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You can set this with the :term:`ciphers` option, the default for poezio being
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``HIGH+kEDH:HIGH+kEECDH:HIGH:!PSK:!SRP:!3DES:!aNULL``.
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You can check what ciphers are enabled by that list by running the command
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``openssl ciphers -v 'cipher list'``. The default list prioritizes `Forward Secrecy`_
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and does not have any cipher suite providing less than 128 bits of security.
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You should change this if you either cannot connect to your server (but in this
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case, you should notify the administrator that his XMPP server configuration
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is probably not great), or if you want to be even more restrictive (only allowing
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256 bits of security *and* forward secrecy, for example).
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For example, gmail.com (and subsequent XMPP services) only support RC4-MD5 and RC4-SHA,
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so you will want to set the option to ``RC4`` (or the default with ``:RC4`` appended,
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just in case they upgrade their service, though that is very unlikely). Please consider
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moving to a better XMPP service provider.
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Certificate validation
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~~~~~~~~~~~~~~~~~~~~~~
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Starting from version 0.7.5, poezio offers some options to check the validity
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of a X.509 certificate.
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TOFU
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----
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The default handling method is the `TOFU/TUFU`_
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method. At your first connection, poezio will save the hash of the certificate
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received, and will compare the received one and the first one for the next
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connections.
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If you are paranoid (or run poezio for the first time in an unsafe
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environment), you can set the :term:`certificate` value of your config file yourself
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(the hash, not colon-separated).
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If the certificate is not the same, poezio will show an error message and wait
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for confirmation:
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.. figure:: ../images/ssl_warning.png
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:alt: Warning message
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If you press y, the change is validated an poezio will match the next certs
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with the accepted one.
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If you press n, you will get the confirmation that the change has been
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refused, and you will be disconnected.
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CA-Based
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--------
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If you are connecting to a large server that has several front-facing
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endpoints, you might be bothered by having to validate the change each time,
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and you may want to check only if it the same authority delivered the
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certificate.
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You can then set the :term:`ca_cert_path` option to the path of a file
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containing the validation chain in `PEM format`_ ; those certificates are
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usually in /usr/share/ca-certificates/ but it may vary depending of your
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distribution.
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If the authority does not match when connecting, you should be disconnected.
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None
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----
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If you do not want to bother with certificate validation at all (which can be
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the case when you run poezio on the same computer as your jabber server), you
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can set the :term:`ignore_certificate` value to true, and let the
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:term:`ca_cert_path` option empty (or even remove it).
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.. warning:: Only do this if you know what you are doing, or you will be open
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to Man in The Middle attacks!
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.. _Forward Secrecy: https://en.wikipedia.org/wiki/Forward_secrecy
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.. _TOFU/TUFU: https://en.wikipedia.org/wiki/User:Dotdotike/Trust_Upon_First_Use
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.. _PEM format: https://tools.ietf.org/html/rfc1422.html
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.. _TLS manifesto: https://github.com/stpeter/manifesto/blob/master/manifesto.txt
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