krfb.service

# This is a systemd user service
#
[Unit]
Description=Start krfb
After=graphical-session.target

[Service]
Type=exec
ExecStart=krfb --display $DISPLAY --nodialog
Restart=always
RestartSec=3

[Install]
WantedBy=graphical-session.target

krfbpass.py

#!/usr/bin/python
#
# krfbpass.py - set the unattended password for krfb
#
# Usage:
#  krfbpass.py newpassword -w
#
import os
import sys
import codecs
import configparser
import tempfile
import shutil
import argparse

# KStringHandler::obscure - https://api.kde.org/frameworks/kcoreaddons/html/kstringhandler_8cpp_source.html#l00164
# InvitationsRfbServer::saveSecuritySettings - https://github.com/KDE/krfb/blob/76ab4450456a94f774dd4fdc52af75942cd996ad/krfb/invitationsrfbserver.cpp#L242-L247

def obscure(x):
 r = ""
 for c in x:
  r += chr(0x1001F - ord(c))
 return r

def printsec(e):
    return """allowUnattendedAccess=true
desktopPassword=%s
unattendedPassword=%s
"""%(e, e)

def linetoken(state, line):
    if state is None:
        state = {
                "section":"",
                "seenSecurity": False,
                }
    if line.startswith("["):
        state["section"] = line.strip().strip("[]").lower()
        if state["section"] == "security":
            state["seenSecurity"] = True
        return (state, "section", state["section"])
    return (state, "entry", line.strip())

def printpass(fn, e):
    ret = ""
    state = None
    wrotePass=False
    with open(fn, "rt", encoding="utf-8") as f:
        for line in f.readlines():
            state, toktype, data = linetoken(state, line)
            if toktype == "section" and data != "security" and state["seenSecurity"]:
                # Exiting security section early
                if not wrotePass:
                    wrotePass = true
                    ret += printsec(e)
            if toktype == "entry" and state["section"] == "security":
                # Filter away things we're changing
                key, _, _ = data.partition("=")
                if key.lower() in ["desktoppassword", "unattendedpassword", "allowunattendedaccess"]:
                    continue
            # Keep this line
            ret += line
        if not wrotePass:
            if state["section"] != "security":
                ret += "\n[Security]\n"
            ret += printsec(e)
    return ret

def main(argv):
    p = argparse.ArgumentParser(description='Modify krfb passwords for unattended access.')
    p.add_argument('pwd', type=str, help='password to set')
    g = p.add_mutually_exclusive_group()
    g.add_argument('-p', '--print', dest='action', action='store_const', const='print', help='print the modified file')
    g.add_argument('-w', '--write', dest='action', action='store_const', const='write', help='write the modified configuration')

    args = p.parse_args(args=argv[1:])

    fn = os.path.expanduser("~/.config/krfbrc")
    e = obscure(args.pwd)

    if not args.action:
        print(e)
        return 0

    if args.action == "print":
        print(printpass(fn, e), end='')
        return 0

    if args.action == "write":
        new = printpass(fn, e)
        with open(fn, "wt", encoding="utf-8") as f:
            f.write(new)
        return 0

$ curl -O https://gist.githubusercontent.com/EBNull/0b84b8aedc730aa45cc50e86b715d5cb/raw/6cc778d23557240e095909a736c39e86858d89fb/krfbpass.py
$ python ./krfbpass.py foo -w
$ sudo mv krfb.service /etc/systemd/user/krfb.service
$ systemctl --user enable krfb
$ systemctl --user start krfb
$ systemctl --user status krfb