TFTPD(8) | System Manager's Manual | TFTPD(8) |
tftpd
— Internet
Trivial File Transfer Protocol server
tftpd |
[-cdCilnow ] [-F
strftime-format] [-s
directory] [-u
user] [-U
umask] [directory ...] |
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). This server should not
be started manually; instead, it should be run using
launchd(8) using the plist
/System/Library/LaunchDaemons/tftp.plist. It may be
started using the launchctl(1) load
command; refer to the documentation for that utility for more
information.
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
/System/Library/LaunchDaemons/tftp.plist. 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 tftpd
, 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
-s
option is required for
-c
and the specified
directory is used as a base.-C
-c
except it falls back to
directory specified via -s
if a directory does not exist for the client's IP.-F
-W
is specified. By default the string "%Y%m%d" is used.-d,
-d
[value]-d
which is specified.
If value is specified, then the debug
level is set to value. The debug level is a
bitmask implemented in
src/libexec/tftpd/tftp-utils.h. Valid values are
0 (DEBUG_NONE), 1 (DEBUG_PACKETS), 2, (DEBUG_SIMPLE), 4 (DEBUG_OPTIONS),
and 8 (DEBUG_ACCESS). Multiple debug values can be combined in the
bitmask by logically OR'ing the values. For example, specifying
-d
15 will enable all the
debug values.
-i
-l
LOG_FTP
.
Note:
Logging of LOG_FTP
messages must also be enabled
in the syslog configuration file,
syslog.conf(5).-n
-o
-s
directorytftpd
to change its root directory to
directory. After doing that but before accepting
commands, tftpd
will switch credentials to an
unprivileged user.-u
usernobody
”) when the
-s
option is used. The user must be specified by
name, not a numeric UID.-U
umaskS_IWGRP
|
S_IWOTH
).-w
tftpd
requires that the file specified in a write
request exist. Note that this only works in directories writable by the
user specified with -u
option-W
-w
but append a YYYYMMDD.nn sequence number to
the end of the filename. Note that the string YYYYMMDD can be changed with
the -F
option.launchctl(1), tftp(1), chroot(2), syslog(3), launchd.plist(5), services(5), syslog.conf(5), launchd(8)
The following RFC's are supported:
RFC 1350: The TFTP Protocol (Revision 2).
RFC 2347: TFTP Option Extension.
RFC 2348: TFTP Blocksize Option.
RFC 2349: TFTP Timeout Interval and Transfer Size Options.
RFC 7440: TFTP Windowsize Option.
The non-standard rollover
and
blksize2
TFTP options are mentioned here:
Extending TFTP, http://www.compuphase.com/tftp.htm.
The tftpd
utility appeared in
4.2BSD; the -s
option was
introduced in FreeBSD 2.2, the
-u
option was introduced in FreeBSD
4.2, the -c
option was introduced in
FreeBSD 4.3, and the -F
and
-W
options were introduced in
FreeBSD 7.4.
Support for Timeout Interval and Transfer Size Options (RFC2349) was introduced in FreeBSD 5.0, support for the TFTP Blocksize Option (RFC2348) and the blksize2 option was introduced in FreeBSD 7.4.
Edwin Groothuis <edwin@FreeBSD.org> performed a major
rewrite of the tftpd
and
tftp(1) code to support RFC2348.
Support for the windowsize option (RFC7440) was introduced in FreeBSD 13.0.
Files larger than 33,553,919 octets (65535 blocks, last one
<512 octets) cannot be correctly transferred without client and server
supporting blocksize negotiation (RFCs 2347 and 2348), or the non-standard
TFTP rollover option. As a kludge, tftpd
accepts a
sequence of block number which wrap to zero after 65535, even if the
rollover option is not specified.
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.
March 2, 2020 | macOS 14.6 |