TFTPD(8) | System Manager's Manual | TFTPD(8) |
tftpd
— DARPA
Internet Trivial File Transfer Protocol server
tftpd |
[-bcdln ] [-g
group] [-p
pathsep] [-s
directory] [-u
user] [directory ...] |
tftpd
is a server which supports the DARPA
Trivial File Transfer Protocol. The TFTP server operates at the port
indicated in the ‘tftp
’ service
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 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.
Access to files may be restricted by invoking
tftpd
with a list of directories 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
-c
-d
-g
group-u
.-l
-n
-p
pathsep-s
directorytftpd
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-u
isn't given, user
defaults to “nobody”. If -g
isn't
also given, change the gid to that of user as
well.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.
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.
Files larger than 33,553,919 octets (65535 blocks, last one less
than 512 octets) cannot be correctly transferred without client and server
supporting 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.
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 difficult 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 manner if this is used in an
insecure environment.
May 5, 2015 | NetBSD 10.99 |