This is the command privbind that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator
PROGRAM:
NAME
privbind - allow an unprivileged application to bind with reserved ports.
SYNOPSIS
privbind -u user [ -g group] [ -n num] [ -l path] command [ arguments ... ]
DESCRIPTION
Normally in Linux, only a superuser process can bind an Internet domain socket with a
reserved port (port numbers less than 1024). Accordingly, server processes are typically
run with superuser privileges, which can be dropped after binding the reserved port.
privbind can execute an application as an unprivileged user with just one extra privilege:
it can bind to reserved ports.
privbind is useful in several situations. It can be used when the application is not
trusted enough; It can be used when the server is written in a language without the
setuid(2) feature (e.g., Java(TM)); It can also be used to run applications which don't
manipulate their own user id and need to be able to bind to a reserved port without
needing any other root privileges.
OPTIONS
-u The -u option is mandatory, and specifies under which user to run the given
command. The user can be specified using either a username or a numeric user id.
It should be an unprivileged (non-root) user.
-g Specifies the group to switch to when running the given command. If this option is
missing, then the given user's default group is used.
-n privbind's default behaviour is to allow the application to call bind(2) with
reserved ports an unlimited number of times. In order to do that (see "HOW IT
WORKS" below), the privbind helper process needs to wait for the application to
exit before it terminates.
The -n num option tells privbind that it can assume that only num binds need to be
given elevated privileges. After this number of bind(2) calls have been executed,
privbind's helper process will exit, leaving behind only the unprivileged
application running.
-l Mostly for internal use during build. Gives the explicit path to the LD_PRELOAD
library.
-h Shows a short help screen, and exits.
EXIT STATUS
Using technical jargon, privbind execs command as its main process, running itself in the
background (as a child of the application's process). The practical upshot of this, in
layman's terms, is that the user never sees privbind's exit status. When running privbind,
the process will exit whenever, and with whatever exit status, command does.
The above point should be particularly noted when using privbind to run daemons.
SECURITY CONSIDERATIONS
privbind has no SUID parts, and runs within the confines of a single process. This serves
to minimize the security implications of using it. It is strongly advised that privbind
not be made SUID, as this would allow any user that can run it to run any process as any
other (non-root) user. At the moment privbind detects such a situation and warns about it,
but will continue with the execution.
HOW IT WORKS
In a nutshell, privbind works by starting two processes. One drops privileges and runs
(exec(2)) the command, the other remains as root. Privbind makes sure to keep a unix
domain socket connecting the two processes.
Privbind uses LD_PRELOAD to intercept every call to bind(2) made by the program. Calls
that can be completed non-privileged are done so. Calls that require root privileges are
forwarded to the root process, that carry them out on the program's behalf.
A more detailed explanation is available in the README file.
Use privbind online using onworks.net services
