A network syslog listener to Bunyan proxy

usage: lumberjack [-d] [-l listener] [-u user] [/path/to/logfile]

lumberjack is a priv revoking daemon. This means it starts as root, opens the log file, opens it's listening sockets, and then chroots and drops privs. The user it drops privs to by default is _lumberjack, but an alternate user can be specified with -u.

By default lumberjack listens to tcp connections on localhost port 514 unless listeners are specified with -l arguments. A listener is as a hostname with an optional port and protocol in a URI format (like the one used in OpenBSDs syslog.conf), ie, [proto://]hostname[:port]. Using * for a hostname will cause the listener to bind to wildcard addresses. Currently supported protocols are tcp, tcp4, tcp6, udp, udp4 and udp6.

If a logfile is not specified lumberjack will log to standard out.

-d causes lumberjack to not daemonise and write errors to stderr.

lumberjack has been written on OpenBSD so that's what the Makefile is for. It's probably not hard to port elsewhere.

An example of a log message in the format specified by Bunyan is:

  {
    "v": 0,
    "level": 35,
    "name": "syslog",
    "hostname": "ozone.eait.uq.edu.au",
    "pid": 0,
    "time": "2016-02-23T01:42:18Z",
    "msg": "sudo:     xdlg : TTY=ttyp2 ; PWD=/server/home/xdlg/lumberjack ; USER=root ; COMMAND=./lumberjack -d -p 514 /var/log/bunyan/test",
    "facility": "authpriv",
    "_": [
      {
        "src": "127.0.0.1",
        "dst": "ozone.eait.uq.edu.au",
        "time": "2016-02-23T01:42:18.568Z"
      }
    ]
  }

Bunyan turns that into:

[2016-02-23T01:42:18Z] LVL35: syslog/0 on ozone.eait.uq.edu.au: sudo:     xdlg : TTY=ttyp2 ; PWD=/server/home/xdlg/lumberjack ; USER=root ; COMMAND=./lumberjack -d -p 514 /var/log/bunyan/test (facility=authpriv)
    _: [
      {
        "src": "127.0.0.1",
        "dst": "ozone.eait.uq.edu.au",
        "time": "2016-02-23T01:42:18.568Z"
      }
    ]