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07.RPKI.RP.rpki-rtr.md

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rpki-rtr

rpki-rtr is an implementation of the "RPKI-router" protocol (RFC-6810).

rpki-rtr depends on rcynic to collect and validate the RPKI data. rpki-rtr's's job is to serve up that data in a lightweight format suitable for routers that want to do prefix origin authentication.

To use rpki-rtr, you need to do two things beyond just running rcynic:

  1. You need to post-process rcynic's output into the data files used by rpki-rtr. The rcynic-cron script handles this automatically, so the default installation should already be taking care of this for you.
  2. You need to set up a listener for the rpki-rtr server, using the generated data files. The platform-specific packages for FreeBSD, Debian, and Ubuntu automatically set up a plain TCP listener, but you will have to do something on other platforms, or if you're using a transport protocol other than plain TCP.

Post-processing rcynic's output

rpki-rtr is designed to do the translation from raw RPKI data into the rpki- rtr protocol only once. It does this by pre-computing the answers to all the queries it is willing to answer for a given data set, and storing them on disk. rpki-rtr's cronjob command handles this computation.

To set this up, add an invocation of rpki-rtr cronjob to the cron job you're already running to run rcynic. As mentioned above, if you're running the rcynic-cron script, this is already being done for you automatically, so you don't need to do anything. If you've written your own cron script, you'll need to add something like this to your script:

/usr/local/bin/rpki-rtr cronjob /var/rcynic/data/authenticated /var/rcynic/rpki-rtr

rpki-rtr cronjob needs write access to a directory where it can store pre- digested versions of the data it pulls from rcynic. In the example above, the directory /var/rcynic/rpki-rtr should be writable by the user ID that is executing the cron script.

rpki-rtr creates a collection of data files, as well as a subdirectory in which each instance of rpki-rtr server can place a PF_UNIX socket file. By default, rpki-rtr creates these files under the directory in which you run it, but you can change that by specifying the target directory as a second command line argument, as shown above.

You should make sure that rpki-rtr cronjob runs at least once before attempting to configure rpki-rtr server. Nothing terrible will happen if you don't do this, but rpki-rtr server invocations started before the first rpki-rtr cronjob run may behave oddly.

Setting up the rpki-rtr server

You need to to set up a server listener that invokes rpki-rtr server. What kind of server listener you set up depends on which network protocol you're using to transport this protocol. rpki-rtr is happy to run under inetd, xinetd, sshd, or pretty much anything -- rpki-rtr doesn't really care, it just reads from stdin and writes to stdout.

rpki-rtr server should be run as a non-privileged user (it is read-only for a reason). You may want to set up a separate UNIX userid for this purpose.

rpki-rtr server takes an optional argument specifying the path to its data directory; if you omit this argument, it uses the directory in in which you run it.

The details of how you set up a listener for this vary depending on the network protocol and the operating system on which you run it. Here are three examples, for running under inetd on FreeBSD, under sshd, or as a free- standing server using rpki-rtr listener.

Running rpki-rtr server under inetd

Running under inetd with plain TCP is insecure and should only be done for testing, but you can also run it with TCP-MD5 or TCP-AO, or over IPsec. The inetd configuration is generally the same, the details of how you set up TCP- MD5, TCP-AO, or IPsec are platform specific.

To run under inetd, you need to:

  1. Add an entry to /etc/services defining a symbolic name for the port, if one doesn't exist already. At present there is no well-known port defined for this protocol, for this example we'll use port 42420 and the symbolic name rpki-rtr.

Add to /etc/services:

rpki-rtr          42420/tcp
  1. Add the service line to /etc/inetd.conf:
rpki-rtr stream tcp nowait nobody /usr/local/bin/rpki-rtr rpki-rtr server /var/rcynic/rpki-rtr

This assumes that you want the server to run as user "nobody", which is generally a safe choice, or you could create a new non-priviledged user for this purpose. DO NOT run the server as root; it shouldn't do anything bad, but it's a network server that doesn't need root access, therefore it shouldn't have root access.

Running rpki-rtr server under sshd

To run rpki-rtr server under sshd, you need to:

  1. Decide whether to run a new instance of sshd on a separate port or use the standard port. rpki-rtr doesn't care, but some people seem to think that it's somehow more secure to run this service on a different port. Setting up sshd in general is beyond the scope of this documention, but most likely you can copy the bulk of your configuration from the standard config.
  2. Configure sshd to know about the rpki-rtr subsystem. Add something like this to your sshd.conf:
Subsystem rpki-rtr /usr/local/bin/rpki-rtr
  1. Configure the userid(s) you expect SSH clients to use to connect to the server. For operational use you almost certainly do NOT want this user to have a normal shell, instead you should configure its shell to be the server (/usr/local/bin/rpki-rtr or wherever you've installed it on your system) and its home directory to be the rpki-rtr data directory (/var/rcynic/rpki-rtr or whatever you're using). If you're using passwords to authenticate instead of ssh keys (not recommended) you will always need to set the password(s) here when configuring the userid(s).
  2. Configure the .ssh/authorized_keys file for your clients; if you're using the example values given above, this would be /var/rcynic/rpki-rtr/.ssh/authorized_keys. You can have multiple SSH clients using different keys all logging in as the same SSH user, you just have to list all of the SSH keys here. You may want to consider using a command= parameter in the key line (see the sshd(8) man page) to lock down the SSH keys listed here so that they can only be used to run the rpki-rtr service.

If you're running a separate sshd for this purpose, you might also want to add an !AuthorizedKeysFile entry pointing at this authorized_keys file so that the server will only use this authorized_keys file regardless of what other user accounts might exist on the machine:

AuthorizedKeysFile /var/rcynic/rpki-rtr/.ssh/authorized_keys

There's a sample sshd.conf in the source directory. You will have to modify it to suit your environment. The most important part is the Subsystem line, which runs the server.sh script as the "rpki-rtr" service, as required by the protocol specification.

Running rpki-rtr listener

rpki-rtr listener is a free-standing plain TCP server which just listens on a TCP socket then forks a child process running rpki-rtr server.

All of the caveats regarding plain TCP apply to rpki-rtr listener.

rpki-rtr listener takes one required argument, the TCP port number on which to listen; it also accepts a second argument which specifies the rcynic output directory, like rpki-rtr server.

/usr/local/bin/rpki-rtr listener 42420 /var/rcynic/rpki-rtr

Other transports

You can also run this code under xinetd, or the netpipes "faucet" program, or stunnel...other than a few lines that might need hacking to log the connection peer properly, the program really doesn't care.

You should, however, care whether the channel you have chosen is secure; it doesn't make a lot of sense to go to all the trouble of checking RPKI data then let the bad guys feed bad data into your routers anyway because you were running the rpki-rtr link over an unsecured TCP connection.

Other commands

rpki-rtr has two other commands which might be useful for debugging:

  1. rpki-rtr client implements a dumb client program for this protocol, over SSH, raw TCP, or by invoking rpki-rtr server directly in a subprocess. The output is not expected to be useful except for debugging. Either run it locally where you run the cron job, or run it anywhere on the net, as in

    $ rpki-rtr client tcp

  2. rpki-rtr show will display a text dump of pre-digested data files in the current directory.