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.\" Authors: Ian Jackson
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.\" authbind is Copyright (C) 1998 Ian Jackson
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.TH AUTHBIND\-HELPER 8 "30th August 1998" "Debian Project" "Debian Linux manual"
.br
.SH NAME 
authbind\-helper \- helper program to bind sockets to privileged ports without root
.SH SYNOPSIS
.BI /usr/lib/authbind/helper " addr\-hex port\-hex " < socket
.SH DESCRIPTION
.B helper
is the program used by
.BR libauthbind ,
which is in turn used by
.B authbind
to allow programs which do not or should not run as root to bind to
low-numbered ports in a controlled way.  See
.BR authbind (1).
.PP
It may also be used standalone, i.e. without assistance from
.BR authbind .
Its standard input should be a TCP/IP socket, and it should be passed
two arguments.
.PP
The arguments are the address and port number, respectively, to which
the caller desires that the socket be bound.  They should be hex
strings,
.I without
leading
.BR 0x ,
of exactly the right length (8 and 4 digits, respectively), being
a pairs of hex digits for each byte in the address or port number when
expressed in host byte order.  For example, the port argument is the
result of something like
.B sprintf(arg,
.B """%04X"",
.BR sin.sin_port) .
.PP
.B helper
will not bind to ports 512 and onwards, because programs like
.B rshd
expect these to be used for outgoing connections, so allowing a user
to bind to one of these would open up security hole(s).
.SH EXIT STATUS
.B helper
will exit with code 0 on success.
.PP
If possible,
.B helper
will return an appropriate
.B errno
value as its exit status.  If this is not possible it may exit with
status 255 or with an exit status corresponding to
.B ENOSYS
.RI ( "Function not implemented" ).
.SH ACCESS CONTROL
See
.BR authbind (1)
for details of the access control regime implemented by
.BR helper .
.SH SEE ALSO
.BR authbind (1),
.BR bind (2)
.SH AUTHOR
.B authbind
and this manpage were written by Ian Jackson.  They are
Copyright (C)1998
by him and released under the GNU General Public Licence; there is NO
WARRANTY.  See
.B /usr/doc/authbind/copyright
and
.B /usr/doc/copyright/GPL
for details.