xmppipe: stdio over XMPP

xmppipe redirects stdin/stdout in a shell pipeline to an XMPP MUC (XEP-0045). xmppipe supports flow control using stream management (XEP-0198) and can optionally deal with overload by acting as a circuit breaker or by discarding messages.

xmppipe works with line oriented tools like grep, sed and awk by outputting each message as a newline terminated, percent-encoded string.

xmppipe can be used in shell scripts to quickly write interactive bots for monitoring systems or for sending alerts.

Usage

xmppipe [*options*]

XMPPIPE_USERNAME=me@example.com
XMPPIPE_PASSWORD="password"
xmppipe -o muc

Requirements

• libstrophe

• Linux: libuuid

apt-get install uuid-dev

Build

$ make

Tests

# Install bats:
# apt-get install bats
# git clone https://github.com/sstephenson/bats.git # or from git
make test

Sandboxing

xmppipe restricts itself to the operations necessary for interacting with stdio. The restrictions are enforced after the XMPP connection is established so the TLS handshake and initial XMPP handshake are not sandboxed.

The limitations depend on the platform. By default:

• Linux: seccomp(2)

• OpenBSD: pledge(2)

• FreeBSD: capsicum(4)

• other: setrlimit(2)

Selecting the sandbox can be done at compile time. For example, to use the "rlimit" sandbox:

XMPPIPE_SANDBOX=XMPPIPE_SANDBOX_RLIMIT make

If a sandbox is interfering with normal operation, please open an issue. To disable the sandbox, compile using the "null" sandbox:

XMPPIPE_SANDBOX=XMPPIPE_SANDBOX_NULL make

Options

-u JID

XMPP username: takes precedence over environment variable

-p password

XMPP password: takes precedence over environment variable

-r resource

XMPP resource, used as the nickname in the MUC

-o output

XMPP MUC name

Default: stdout-hostname-uid

-S subject

XMPP MUC subject

-a address:port

Specify the IP address and port of the XMPP server

-d

Discard stdin when MUC is empty

-D

Discard stdin and print to local stdout

-e

Ignore stdin EOF

-s

Exit when MUC is empty

-x

Base64 encode/decode data

-b size

Size of read buffer

-I interval

Request stream management status every interval messages

-k seconds

Periodically send a keepalive

-K count

Number of keepalive failures before exiting

-P ms

Poll delay

-v

Increase verbosity

Decoding Percent-Encoded Strings

Using bash:

decode() {
    printf '%b' "${1//%/\\x}"
}

Examples

Shell Bot

An interactive XMPP bot written in the shell:

#!/bin/bash

set -e
set -u
set -o pipefail

trap cleanup 0

TMPDIR=$(mktemp -d)

in="$TMPDIR/stdin"
out="$TMPDIR/stdout"

mkfifo $in
mkfifo $out

cleanup() {
    rm -rf $TMPDIR
}

decode() {
    printf '%b' "${1//%/\\x}"
}

bot() {
    while read line; do
        IFS=:
        set -- $line
        if [ "$1" = "p" ]; then
            decode "$line" 1>&2
            echo 1>&2
        elif [ "$1" = "m" ]; then
            USER="$(decode ${3#*%2F})"
            IFS=$OFS
            MSG="$(decode ${!#})"
            case $MSG in
                *"has set the subject to:"*) ;;
                "sudo make me a sandwich")
                    echo "$USER: you're a sandwich"
                    ;;
                sudo*)
                    echo "I'm sorry, $USER. I'm afraid I can't do that."
                    ;;
                uptime)
                    uptime
                    ;;
                exit)
                    echo "exiting ..."
                    exit 0
                    ;;
                *)
                    echo "$@"
                    ;;
            esac
        fi
    done < $out
}

bot > $in &
xmppipe "$@" <$in >$out

SSH over XMPP

See examples/ssh-over-xmpp:

# Server: has access to the destination SSH server
# ssh-over-xmpp server <conference> <IP address> <port>
ssh-over-xmpp server sshxmpp 1.2.3.4 22

## Client: has access to the XMPP server
ssh -o ProxyCommand="ssh-over-xmpp client sshxmpp" 127.0.0.1

Stream Events from Riemann

This example will stream events from a query to an XMPP MUC using Riemann's SSE interface. The events are written to a named pipe to avoid buffering.

mkfifo riemann
curl -s --get --data subscribe=true \
    --data-urlencode 'query=(service ~= "^example")' \
    http://example.com:80/index < /dev/null > riemann &
xmppipe -o "muc" -d -vv -S "riemann events" < riemann

Mirror a terminal session using script(1)

• user

#!/bin/bash

MUC=console

TMPDIR=$(mktemp -d)
FIFO=$TMPDIR/console
mkfifo $FIFO

stty cols 80 rows 24
(cat $FIFO | xmppipe -r user -o $MUC -x) > /dev/null 2> $TMPDIR/stderr &
script -q -f $FIFO

• viewers

#!/bin/bash

decode() {
    printf '%b' "${1//%/\\x}"
}

stty cols 80 rows 24
xmppipe -r viewer -o console -x | while read l; do
    IFS=:
    set -- $l
    if [ "$1" = "m" ]; then
        decode $5
    fi
done

Mirror a terminal session to a web page

Environment Variables

• XMPPIPE_USERNAME: XMPP jid

• XMPPIPE_PASSWORD: XMPP password

Format

Each message is terminated by a new line. Message fields are separated by ":" and percent encoded.

Presence

p:<available|unavailable>:<to jid>:<from jid>

Example:

p:available:test@muc.example.com/xmppipe:occupant@example.com/1234

Message

m:<chat|groupchat>:<from jid>:<to jid>:<message body>

Example:

m:groupchat:test@muc.example.com/mobile:user1@example.com/1234:Hello
m:chat:user1@example.com/mobile:user2@example.com:Message%20goes%20here

Compatibility

Tested with ejabberd and mongooseim.

Security Considerations

libstrophe does not verify the TLS server certificates. Sessions can be MITM'ed.

libstrophe has support for TLS certificate verification on a branch.

libmesode supports TLS certificate verification.

License

Copyright (c) 2015-2017, Michael Santos michael.santos@gmail.com

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

TODO

• Support TLS certificate verification

  Switch to using libmesode

• support XEP-0384: OMEMO Encryption

• sandbox

  Strengthen the sandbox restrictions:

  • policy for TLS handshake
  • policy for initial XMPP handshake