tftpd(8) - NetBSD Manual Pages

TFTPD(8)                NetBSD System Manager's Manual                TFTPD(8)


NAME

     tftpd -- DARPA Internet Trivial File Transfer Protocol server


SYNOPSIS

     tftpd [-bcdln] [-g group] [-p pathsep] [-s directory] [-u user]
           [directory ...]


DESCRIPTION

     tftpd is a server which supports the DARPA Trivial File Transfer Proto-
     col.  The TFTP server operates at the port indicated in the `tftp' ser-
     vice description; see services(5).  The server is normally started by
     inetd(8).

     The use of tftp(1) does not require an account or password on the remote
     system.  Due to the lack of authentication information, tftpd will allow
     only publicly readable files to be accessed.  Filenames beginning in
     ``../'' or containing ``/../'' are not allowed.  Unless -c is used, files
     may be written to only if they already exist and are publicly writable.

     Note that this extends the concept of "public" to include all users on
     all hosts that can be reached through the network; this may not be appro-
     priate on all systems, and its implications should be considered before
     enabling tftp service.  The server should have the user ID with the low-
     est possible privilege.

     Access to files may be restricted by invoking tftpd with a list of direc-
     tories by including up to 20 pathnames as server program arguments in
     /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.

     The options are:

     -b             Allow clients which return acknowledgements to the broad-
                    cast address to communicate with the tftp server.  Some
                    tftp clients, notably ones resident in the ROMs of older
                    Cisco equipment, return their acknowledgements to the
                    broadcast address rather than the server's unicast
                    address.

     -c             Allow unrestricted creation of new files.  Without this
                    flag, only existing publicly writable files can be over-
                    written.

     -d             Enable verbose debugging messages to syslogd(8).

     -g group       Change gid to that of group on startup.  If this isn't
                    specified, the gid is set to that of the user specified
                    with -u.

     -l             Logs all requests using syslog(3).

     -n             Suppresses negative acknowledgement of requests for nonex-
                    istent relative filenames.

     -p pathsep     All occurrences of the single character pathsep (path sep-
                    arator) in the requested filename are replaced with `/'.

     -s directory   tftpd will chroot(2) to directory on startup.  This is
                    recommended for security reasons (so that files other than
                    those in the /tftpboot directory aren't accessible).  If
                    the remote host passes the directory name as part of the
                    file name to transfer, you may have to create a symbolic
                    link from `tftpboot' to `.' under /tftpboot.

     -u user        Change uid to that of user on startup.  If -u isn't given,
                    user defaults to ``nobody''.  If -g isn't also given,
                    change the gid to that of user as well.


SEE ALSO

     tftp(1), inetd(8)

     The TFTP Protocol (Revision 2), RFC, 1350, July 1992.

     TFTP Option Extension, RFC, 2347, May 1998.

     TFTP Blocksize Option, RFC, 2348, May 1998.

     TFTP Timeout Interval and Transfer Size Options, RFC, 2349, May 1998.


HISTORY

     The tftpd command appeared in 4.2BSD.

     The -s flag appeared in NetBSD 1.0.

     The -g and -u flags appeared in NetBSD 1.4.

     IPv6 support was implemented by WIDE/KAME project in 1999.

     TFTP options were implemented by Wasabi Systems, Inc., in 2003, and first
     appeared in NetBSD 2.0.


BUGS

     Files larger than 33,553,919 octets (65535 blocks, last one less than 512
     octets) cannot be correctly transferred without client and server sup-
     porting blocksize negotiation (RFCs 2347 and 2348).  As a kludge, tftpd
     accepts a sequence of block numbers which wrap to zero after 65535.

     Many tftp clients will not transfer files over 16,776,703 octets (32767
     blocks), as they incorrectly count the block number using a signed rather
     than unsigned 16-bit integer.


SECURITY CONSIDERATIONS

     You are strongly advised to set up tftpd using the -s flag in conjunction
     with the name of the directory that contains the files that tftpd will
     serve to remote hosts (e.g., /tftpboot).  This ensures that only the
     files that should be served to remote hosts can be accessed by them.

     Because there is no user-login or validation within the TFTP protocol,
     the remote site will probably have some sort of file-access restrictions
     in place.  The exact methods are specific to each site and therefore dif-
     ficult to document here.

     If unrestricted file upload is enabled via the -c option, care should be
     taken that this can be used to fill up disk space in an uncontrolled man-
     ner if this is used in an insecure environment.

NetBSD 10.99                      May 5, 2015                     NetBSD 10.99