X-Git-Url: https://git.distorted.org.uk/~mdw/tripe/blobdiff_plain/b147e573818624ac77eab9de38d4f05346d60f5d..HEAD:/contrib/knock.in diff --git a/contrib/knock.in b/contrib/knock.in index be55f2b9..d7e0f0ef 100755 --- a/contrib/knock.in +++ b/contrib/knock.in @@ -1,23 +1,53 @@ #! /bin/sh +### +### SSH forced-command script for establishing dynamic associations. +### +### (c) 2012 Mark Wooding +### + +###----- Licensing notice --------------------------------------------------- +### +### This file is part of Trivial IP Encryption (TrIPE). +### +### TrIPE is free software: you can redistribute it and/or modify it under +### the terms of the GNU General Public License as published by the Free +### Software Foundation; either version 3 of the License, or (at your +### option) any later version. +### +### TrIPE is distributed in the hope that it will be useful, but WITHOUT +### ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or +### FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +### for more details. +### +### You should have received a copy of the GNU General Public License +### along with TrIPE. If not, see . set -e ### This script performs the passive side of a dynamic association. It is -### intended to be set as the `tripe' user's shell, and invoked via ssh(1). -### Specifically, for each dynamic peer, add a line to `.ssh/authorized_keys' -### of the form +### intended to be set as the forced command in an `.ssh/authorized_keys' +### file. Specifically, for each dynamic peer, add a line to +### `.ssh/authorized_keys' of the form ### -### command="PEER" ssh-rsa ... +### environment="TRIPE_USER=PEER" ssh-rsa ... ### ### There's an additional wrinkle. Suppose that the passive TrIPE endpoint ### is behind a NAT, and the SSH gateway is on a different machine. The ### gateway should have its own `tripe' user, and this script should again be ### its shell. On the gateway, add a `.ssh/authorized_keys' entry ### -### command="tripe@SERVER:PEER" ssh-rsa ... +### environment="TRIPE_USER=tripe@SERVER:PEER" ssh-rsa ... ### ### for the dynamic endpoint. On the passive endpoint itself, you need an -### entry for the gateway's `tripe' user's key, with no command. +### entry for the gateway's `tripe' user's key, with `TRIPE_GATEWAY' set to +### any value, like +### +### environment="TRIPE_GATEWAY=t" ssh-rsa ... +### +### For backwards compatibility, it can also be set as the `tripe' user's +### shell, with the `[tripe@SERVER:]PEER' indicator set as the forced +### command. If there are no forced command or `TRIPE_*' environment +### variables then it is assumed that a gateway is calling. : ${prefix=@prefix@} ${exec_prefix=@exec_prefix@} : ${bindir=@bindir@} @@ -25,23 +55,47 @@ set -e : ${tripectl=$bindir/tripectl} export TRIPEDIR TRIPESOCK -case "$#,$1,$2" in - - 2,-c,*:*) - ## Proxy through to another server. - server=${2%:*} user=${2##*:} - exec ssh "$server" "$user" +## Make sure we're being called properly, and figure out the peer identity. +case "${TRIPE_USER+t},${TRIPE_GATEWAY+t},$#,$1" in + t,,0,) set -- "$TRIPE_USER" ;; + ,t,0,) set -- $SSH_ORIGINAL_COMMAND; unset SSH_ORIGINAL_COMMAND ;; + ,,2,-c) ;; + *) + echo >&2 "usage: $0 -c [SERVER:]PEER [ACTION]" + exit 1 ;; +esac - 2,-c,*) - ## Connect to the local tripe server. - exec $tripectl SVCSUBMIT connect passive "$2" - ;; +## Examine the peer identifier and work out how to proceed. +case "$#,$1" in + 0,*) echo >&2 "missing peer identifier"; exit 1 ;; + *:*) mode=proxy server=${1%:*} user=${1##*:} ;; + *) mode=local user=$1 ;; +esac +shift +## Fetch the optional command from where SSH stashed it. +case "$#" in 0) set -- $SSH_ORIGINAL_COMMAND ;; esac +case "$#,$1" in + 0, | 1,hello) act=hello ;; + 1,goodbye) act=goodbye ;; + *) echo >&2 "$0: unknown action spec \`$*'"; exit 1 ;; +esac + +## Now actually do something. +case "$mode,$act" in + proxy,*) + exec ssh "$server" "$user" "$act" + ;; + local,hello) + exec $tripectl SVCSUBMIT connect passive "$user" + ;; + local,goodbye) + peer=$($tripectl SVCSUBMIT connect userpeer "$user") + exec $tripectl KILL "$peer" + ;; *) - ## Anything else is an error. - echo >&2 "usage: $0 -c [SERVER:]PEER" + echo >&2 "$0: unknown mode/action $mode/$act" exit 1 ;; - esac