tftpd(8)tftpd(8)NAMEtftpd - Trivial File Transfer Protocol server
SYNOPSIStftpd {directory}
DESCRIPTIONtftpd is a server which supports the DARPA Trivial File Transfer Proto‐
col ( RFC1350 ⟨http://tools.ietf.org/rfc/rfc1350.txt⟩ ). The TFTP
server is started by inetd(8).
directory is required argument; if it is not given tftpd aborts. This
path is prepended to any file name requested via TFTP protocol, effec‐
tively chrooting tftpd to this directory. File names are validated not
to escape out of this directory, however administrator may configure
such escape using symbolic links.
It is in difference of variants of tftpd usually distributed with unix-
like systems, which take a list of directories and match file names to
start from one of given prefixes or to some random default, when no ar‐
guments were given. There are two reasons not to behave in this way:
first, it is inconvenient, clients are not expected to know something
about layout of filesystem on server host. And second, TFTP protocol
is not a tool for browsing of server's filesystem, it is just an agent
allowing to boot dumb clients.
In the case when tftpd is used together with rarpd(8)[Cross reference
to non-existant ID “rarpd”], tftp directories in these services should
coincide and it is expected that each client booted via TFTP has boot
image corresponding its IP address with an architecture suffix follow‐
ing Sun Microsystems conventions. See rarpd(8)[Cross reference to non-
existant ID “rarpd”] for more details.
SECURITY
TFTP protocol does not provide any authentication. Due to this capital
flaw tftpd is not able to restrict access to files and will allow only
publically readable files to be accessed. Files may be written only if
they already exist and are publically writable.
Impact is evident, directory exported via TFTP must not contain sensi‐
tive information of any kind, everyone is allowed to read it as soon as
a client is allowed. Boot images do not contain such information as
rule, however you should think twice before publishing f.e. Cisco IOS
config files via TFTP, they contain unencrypted passwords and may con‐
tain some information about the network, which you were not going to
make public.
The tftpd server should be executed by inetd with dropped root privi‐
leges, namely with a user ID giving minimal access to files published
in tftp directory. If it is executed as superuser occasionally, tftpd
drops its UID and GID to 65534, which is most likely not the thing
which you expect. However, this is not very essential; remember, only
files accessible for everyone can be read or written via TFTP.
SEE ALSOrarpd(8)[Cross reference to non-existant ID “rarpd”], tftp(1), in‐
etd(8).
HISTORY
The tftpd command appeared in 4.2BSD. The source in iputils is cleaned
up both syntactically (ANSIized) and semantically (UDP socket IO).
It is distributed with iputils mostly as good demo of an interesting
feature (MSG_CONFIRM) allowing to boot long images by dumb clients not
answering ARP requests until they are finally booted. However, this is
full functional and can be used in production.
AVAILABILITYtftpd is part of iputils package and the latest versions are available
in source form at ⟨http://www.skbuff.net/iputils/iputils-cur‐
rent.tar.bz2⟩.
iputils- 13 August 2013 tftpd(8)
