From 1079962e4c06f88a54e50d997c1b7e84303d30b4 Mon Sep 17 00:00:00 2001 From: Bernhard Schmidt Date: Sat, 15 Aug 2020 21:29:50 +0200 Subject: New upstream version 2.5~beta1 --- doc/man-sections/renegotiation.rst | 52 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 52 insertions(+) create mode 100644 doc/man-sections/renegotiation.rst (limited to 'doc/man-sections/renegotiation.rst') diff --git a/doc/man-sections/renegotiation.rst b/doc/man-sections/renegotiation.rst new file mode 100644 index 0000000..b817cfa --- /dev/null +++ b/doc/man-sections/renegotiation.rst @@ -0,0 +1,52 @@ +Data Channel Renegotiation +-------------------------- + +When running OpenVPN in client/server mode, the data channel will use a +separate ephemeral encryption key which is rotated at regular intervals. + +--reneg-bytes n + Renegotiate data channel key after ``n`` bytes sent or received + (disabled by default with an exception, see below). OpenVPN allows the + lifetime of a key to be expressed as a number of bytes + encrypted/decrypted, a number of packets, or a number of seconds. A key + renegotiation will be forced if any of these three criteria are met by + either peer. + + If using ciphers with cipher block sizes less than 128-bits, + ``--reneg-bytes`` is set to 64MB by default, unless it is explicitly + disabled by setting the value to :code:`0`, but this is + **HIGHLY DISCOURAGED** as this is designed to add some protection against + the SWEET32 attack vector. For more information see the ``--cipher`` + option. + +--reneg-pkts n + Renegotiate data channel key after **n** packets sent and received + (disabled by default). + +--reneg-sec args + Renegotiate data channel key after at most ``max`` seconds + (default :code:`3600`) and at least ``min`` seconds (default is 90% of + ``max`` for servers, and equal to ``max`` for clients). + :: + + reneg-sec max [min] + + The effective ``--reneg-sec`` value used is per session + pseudo-uniform-randomized between ``min`` and ``max``. + + With the default value of :code:`3600` this results in an effective per + session value in the range of :code:`3240`..:code:`3600` seconds for + servers, or just 3600 for clients. + + When using dual-factor authentication, note that this default value may + cause the end user to be challenged to reauthorize once per hour. + + Also, keep in mind that this option can be used on both the client and + server, and whichever uses the lower value will be the one to trigger + the renegotiation. A common mistake is to set ``--reneg-sec`` to a + higher value on either the client or server, while the other side of the + connection is still using the default value of :code:`3600` seconds, + meaning that the renegotiation will still occur once per :code:`3600` + seconds. The solution is to increase --reneg-sec on both the client and + server, or set it to :code:`0` on one side of the connection (to + disable), and to your chosen value on the other side. -- cgit v1.2.3