The
tftpd
utility is a server which supports the
Internet Trivial File Transfer
Protocol
(RFC 1350
)
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.
Files containing the string
``/../
''
or starting with
``../
''
are not allowed.
Files may be written 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
inetd.conf5.
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
-s
option provides additional security by changing
the root directory of
,
thereby prohibiting accesses to outside of the specified
directory
Because
chroot(2)
requires super-user privileges,
tftpd
must be run as
root
However, after performing the
chroot(2)
call,
tftpd
will set its user ID to that of the specified
user
or
``nobody
''
if no
-u
option is specified.
The options are:
-c
Changes the default root directory of a connecting host via
chroot(2)
based on the connecting IP address.
This prevents multiple clients from writing to the same file at the same time.
If the directory does not exist, the client connection is refused.
The
-s
option is required for
-c
and the specified
directory
is used as a base.
-C
Operates the same as
-c
except it falls back to
directory
specified via
-s
if a directory does not exist for the client's IP.
-l
Log all requests using
syslog(3)
with the facility of
LOG_FTPNote
Logging of
LOG_FTP
messages
must also be enabled in the syslog configuration file,
syslog.conf5.
-n
Suppress negative acknowledgement of requests for nonexistent
relative filenames.
-s directory
Cause
tftpd
to change its root directory to
directory
After doing that but before accepting commands,
tftpd
will switch credentials to an unprivileged user.
-u user
Switch credentials to
user
(default
``nobody
''
when the
-s
option is used.
The user must be specified by name, not a numeric UID.
-U umask
Set the
umask
for newly created files.
The default is 022
(S_IWGRP | S_IWOTH
)
-w
Allow write requests to create new files.
By default
tftpd
requires that the file specified in a write request exist.
K. R. Sollins
The TFTP Protocol (Revision 2)
July 1992
RFC 1350, STD 33
HISTORY
The
tftpd
utility appeared in
BSD 4.2
the
-s
option was introduced in
Fx 2.2 ,
the
-u
option was introduced in
Fx 4.2 ,
and the
-c
option was introduced in
Fx 4.3 .
BUGS
Files larger than 33488896 octets (65535 blocks) cannot be transferred
without client and server supporting blocksize negotiation (RFC1783).
Many tftp clients will not transfer files over 16744448 octets (32767 blocks).
