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"

# default name: stdout-*hostname*-*uid*
xmpipe
xmppipe muc
xmppipe muc@example.com

Requirements

• libstrophe

  libstrophe 0.9.2 or later is required for TLS certificate verification.

Build

$ make

Tests

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

Sandboxing

xmppipe applies 2 sandboxes:

• a permissive "init" sandbox allowing network connections to the XMPP server

• once the connection is established, a stricter "stdio" sandbox limits the process to stdio

The effectiveness of the sandbox depends on which mechanism is used. By default:

• Linux:

  • init: seccomp(2)
  • stdio: seccomp(2)

• OpenBSD:

  • init: pledge(2)
  • stdio: pledge(2)

• FreeBSD:

  • init: setrlimit(2)
  • stdio: setrlimit(2)/capsicum(4)

• other: setrlimit(2)

  • init: setrlimit(2)
  • stdio: setrlimit(2)

Selecting the sandbox is done at compile time. For example, to use the "rlimit" 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=null make

Options

-u, --username JID

XMPP username: takes precedence over environment variable

-p, --password password

XMPP password: takes precedence over environment variable

-r, --resource resource

XMPP resource, used as the nickname in the MUC

-S, --subject subject

XMPP MUC subject

-a, --address address:port

Specify the IP address and port of the XMPP server

-F, --format text:csv

stdin is text (default) or colon separated values

-d, --discard

Discard stdin when MUC is empty

-D, --discard-to-stdout

Discard stdin and print to local stdout

-e, --ignore-eof

Ignore stdin EOF

-s, --exit-when-empty

Exit when MUC is empty

-x, --base64

Base64 encode/decode data

-b, --buffer-size size

Size of read buffer

-I, --interval interval

Request stream management status every interval messages

-k, --keepalive seconds

Periodically send a keepalive

-K, --keepalive-failures count

Number of keepalive failures before exiting

-P, --poll-delay ms

Poll delay

-v, --verbose

Increase verbosity

--chat

Use one to one chat

--no-tls-verify

Disable TLS certificate verification

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 -o errexit
set -o nounset
set -o pipefail

trap cleanup EXIT

TMPDIR=$(mktemp -d)

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

mkfifo $in
mkfifo $out

cleanup() {
    rm -rf $TMPDIR
}

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

bot() {
    while IFS=: read -r stanza type from to body; do
        case "$stanza" in
            m) ;;

            p) decode "$stanza:$type:$from:$to" 1>&2
               echo 1>&2
               continue
               ;;

            *) continue ;;
        esac

        USER="$(decode ${from#*/})"
        MSG="$(decode ${body})"

        case $MSG in
            *"has set the subject to:"*) ;;
            "sudo make me a sandwich")
                echo "$USER: you're a sandwich"
                ;;
            sudo*)
                echo "I'm sorry, $USER. I'm afraid I can't do that."
                ;;
            uptime)
                uptime
                ;;
            exit)
                echo "exiting ..."
                exit 0
                ;;
            *)
                echo "$MSG"
                ;;
        esac
    done < $out
}

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

Sending Notifications/Alerts

Start xmppipe attached to a pipe:

mkfifo /tmp/xmpp

xmppipe -o groupchat <> /tmp/xmpp

Any data written to the pipe will be sent to the groupchat:

echo "test" > /tmp/xmpp

df -h > /tmp/mpp

git diff > /tmp/xmpp

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 --verbose --verbose \
        --discard --subject "riemann events" muc < riemann

Desktop Notifications

#!/bin/bash

set -o errexit
set -o nounset
set -o pipefail

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

MUC=""

while getopts ":o:" opt; do
  case $opt in
    o) MUC="$OPTARG" ;;
    *) ;;
  esac
done

xmppipe "$@" | while IFS=: read stanza type from to body; do
  case "$stanza" in
    m) notify-send "$MUC" "$(decode $body)" ;;
    *) continue ;;
  esac
done

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 --resource user -x $MUC) > /dev/null 2> $TMPDIR/stderr &
script -q -f $FIFO

• viewers

#!/bin/bash

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

stty cols 80 rows 24
xmppipe --resource viewer --base64 console | \
  while IFS=: read -r x s f t m; do
    [ "$m" = "m" ] && decode "$m"
  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.

Colon separated valued are accepted as input if the input format type is set to csv (--format=csv).

Presence

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

Input/Output:

Both

Example:

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

Message

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

Input/Output:

Both

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

Inline Image

Inline images will add a hint so clients (notably Conversations will display the image instead of a URL.

• type, from and to are optional

• message body: the percent escaped URL

  I:<chat|groupchat|normal|headline>:::

Input/Output:

Input only

Example:

I::::https%3A%2F%2Fhttpstatusdogs.com%2Fimg%2F500.jpg

XEP-0363: HTTP Upload

HTTP uploads create an upload slot. The XMPP server will respond with get and put URLs. The put URL can be used to upload the file using, e.g., curl. The get URL is used by clients for downloading the file.

Note: currently xmppipe creates the slot but does not upload the file.

The input format is:

• type, from and to are optional

• message body: percent escaped, pipe separated value

  • filename
  • size
  • optional: MIME type

  u:<chat|groupchat|normal|headline>:::|<size (bytes)>[|]

The output format is:

• type, from and to are optional

• message body: percent escaped, pipe separated value

  • get URL
  • put URL

  U:<chat|groupchat|normal|headline>:::|

Example:

# $ stat --format="%s" example.png
# 16698
u::::example.png%7C16698

# also specify content type
u::::example.png%7C16698%7Cimage%2Fpng

# server response: slot created
U:groupchat:upload.example.com:user@example.com/123:https%3A//example.com/upload/0b9da82fea20a78778cbeddeab0472286cc35ed1/xyEaWFVZv3sv5ay9AGH5qBU02gglZRyUeGbjQg3k/example.png%7chttps%3A//example.com/upload/0b9da82fea20a78778cbeddeab0472286cc35ed1/xyEaWFVZv3sv5ay9AGH5qBU02gglZRyUeGbjQg3k/example.png

# to upload the file
curl https://example.com/upload/0b9da82fea20a78778cbeddeab0472286cc35ed1/xyEaWFVZv3sv5ay9AGH5qBU02gglZRyUeGbjQg3k/example.png --upload-file example.png

Compatibility

Testing is done with ejabberd.

Also confirmed to work with:

• ejabberd (creep.im)
• prosody (dismail.de)
• openfire (jab.im)
• tigase (tigase.im)
• mongooseim

License

Copyright (c) 2015-2020, 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 XEP-0384: OMEMO Encryption

• support alternative input modes

  • "raw" mode: XML input/output

• HTTP Upload

  • support PUT header elements
  • handle error conditions

  Questions:

  • save the maximum file size returned by the server and disallow uploads larger than the value?

  • xmppipe is "pinned" to the upload server returned in the IQ reply (the "to" field is ignored)

  • allow other upload servers?

  • error if different upload server is specified in "u::"?