xref: /freebsd/libexec/tftpd/tftpd.8 (revision 67c31d5008f5d1275cc3f629b02bb786b77c4f58)

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.\"	@(#)tftpd.8	8.1 (Berkeley) 6/4/93
.\" $FreeBSD$
.\"
.Dd September 14, 2000
.Dt TFTPD 8
.Os BSD 4.2
.Sh NAME
.Nm tftpd
.Nd
Internet Trivial File Transfer Protocol server
.Sh SYNOPSIS
.Nm /usr/libexec/tftpd
.Op Fl ln
.Op Fl s Ar directory
.Op Fl u Ar user
.Op Ar directory ...
.Sh DESCRIPTION
.Nm Tftpd
is a server which supports the
Internet Trivial File Transfer
Protocol
.Pq Tn RFC 1350 .
The
.Tn TFTP
server operates
at the port indicated in the
.Ql tftp
service description;
see
.Xr services 5 .
The server is normally started by
.Xr inetd 8 .
.Pp
The use of
.Xr tftp 1
does not require an account or password on the remote system.
Due to the lack of authentication information,
.Nm
will allow only publicly readable files to be
accessed.
Files containing the string ``/\|\fB.\|.\fP\|/'' or starting with
``\|\fB.\|.\fP\|/'' are not allowed.
Files may be written only if they already exist and are publicly writable.
Note that this extends the concept of
.Dq public
to include
all users on all hosts that can be reached through the network;
this may not be appropriate on all systems, and its implications
should be considered before enabling tftp service.
The server should have the user ID with the lowest possible privilege.
.Pp
Access to files may be restricted by invoking
.Nm
with a list of directories by including up to 20 pathnames
as server program arguments in
.Pa /etc/inetd.conf .
In this case access is restricted to files whose
names are prefixed by the one of the given directories.
The given directories are also treated as a search path for
relative filename requests.
.Pp
The
.Fl s
option provides additional security by changing
.Nm tftpd Ns No 's
root directory, thereby prohibiting accesses outside of the specified
.Ar directory .
Because
.Xr chroot 2
requires super-user privileges,
.Nm
must be run as root.
However, after performing the
.Fn chroot ,
.Nm
will set its user id to that of the specified
.Ar user ,
or
.Dq nobody
if no
.Fl u
option is specified.
.Pp
The options are:
.Bl -tag -width Ds
.It Fl l
Log all requests using
.Xr syslog 3
with the facility of
.Dv LOG_FTP .
Note: Logging of
.Dv LOG_FTP
messages
must also be enabled in the syslog configuration file,
.Xr syslog.conf 5 .
.It Fl n
Suppress negative acknowledgement of requests for nonexistent
relative filenames.
.It Fl s Ar directory
Cause
.Nm
to change its root directory to
.Pa directory .
After changing roots but before accepting commands,
.Nm
will switch credentials to an unprivileged user.
.It Fl u Ar user
Switch credentials to
.Ar user
(default
.Dq nobody )
when the
.Fl s
option is used.
The user must be specified by name, not a numeric UID.
.El
.Sh SEE ALSO
.Xr tftp 1 ,
.Xr chroot 2 ,
.Xr inetd 8 ,
.Xr syslogd 8
.Rs
.%A K. R. Sollins
.%T The TFTP Protocol (Revision 2)
.%D July 1992
.%O RFC 1350, STD 33
.Re
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 ;
the
.Fl s
option was introduced in
.Fx 2.2 ,
and the
.Fl u
option was introduced in
.Fx 4.2 .