1.\" Copyright (c) 1983, 1991, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 3. Neither the name of the University nor the names of its contributors 13.\" may be used to endorse or promote products derived from this software 14.\" without specific prior written permission. 15.\" 16.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 17.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 20.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26.\" SUCH DAMAGE. 27.\" 28.Dd May 8, 2024 29.Dt TFTPD 8 30.Os 31.Sh NAME 32.Nm tftpd 33.Nd Internet Trivial File Transfer Protocol server 34.Sh SYNOPSIS 35.Nm tftpd 36.Op Fl CcdlnoSw 37.Op Fl F Ar strftime-format 38.Op Fl s Ar directory 39.Op Fl U Ar umask 40.Op Fl u Ar user 41.Op Ar directory ... 42.Sh DESCRIPTION 43The 44.Nm 45utility is a server which supports the 46Internet Trivial File Transfer 47Protocol 48.Pq Tn RFC 1350 . 49The 50.Tn TFTP 51server operates 52at the port indicated in the 53.Ql tftp 54service description; 55see 56.Xr services 5 . 57The server is normally started by 58.Xr inetd 8 . 59.Pp 60The use of 61.Xr tftp 1 62does not require an account or password on the remote system. 63Due to the lack of authentication information, 64.Nm 65will allow only publicly readable files to be 66accessed. 67Files containing the string 68.Dq Li "/../" 69or starting with 70.Dq Li "../" 71are not allowed. 72Files may be written only if they already exist (unless the 73.Fl w 74option is used) and are publicly writable (unless chrooted and the 75.Fl S 76option is used). 77Note that this extends the concept of 78.Dq public 79to include 80all users on all hosts that can be reached through the network; 81this may not be appropriate on all systems, and its implications 82should be considered before enabling tftp service. 83The server should have the user ID with the lowest possible privilege. 84.Pp 85Access to files may be restricted by invoking 86.Nm 87with a list of directories by including up to 20 pathnames 88as server program arguments in 89.Xr inetd.conf 5 . 90In this case access is restricted to files whose 91names are prefixed by the one of the given directories. 92The given directories are also treated as a search path for 93relative filename requests. 94.Pp 95The 96.Fl s 97option provides additional security by changing 98the root directory of 99.Nm , 100thereby prohibiting accesses to outside of the specified 101.Ar directory . 102Because 103.Xr chroot 2 104requires super-user privileges, 105.Nm 106must be run as 107.Li root . 108However, after performing the 109.Xr chroot 2 110call, 111.Nm 112will set its user ID to that of the specified 113.Ar user , 114or 115.Dq Li nobody 116if no 117.Fl u 118option is specified. 119.Pp 120The options are: 121.Bl -tag -width Ds 122.It Fl c 123Changes the default root directory of a connecting host via 124.Xr chroot 2 125based on the connecting IP address. 126This prevents multiple clients from writing to the same file at the same time. 127If the directory does not exist, the client connection is refused. 128The 129.Fl s 130option is required for 131.Fl c 132and the specified 133.Ar directory 134is used as a base. 135.It Fl C 136Operates the same as 137.Fl c 138except it falls back to 139.Ar directory 140specified via 141.Fl s 142if a directory does not exist for the client's IP. 143.It Fl F 144Use this 145.Xr strftime 3 146compatible format string for the creation of the suffix if 147.Fl W 148is specified. 149By default the string "%Y%m%d" is used. 150.It Fl d, d Ar [value] 151Enables debug output. 152If 153.Ar value 154is not specified, then the debug level is increased by one 155for each instance of 156.Fl d 157which is specified. 158.Pp 159If 160.Ar value 161is specified, then the debug level is set to 162.Ar value . 163The debug level is a bitmask implemented in 164.Pa src/libexec/tftpd/tftp-utils.h . 165Valid values are 0 (DEBUG_NONE), 1 (DEBUG_PACKETS), 2, (DEBUG_SIMPLE), 1664 (DEBUG_OPTIONS), and 8 (DEBUG_ACCESS). Multiple debug values can be combined 167in the bitmask by logically OR'ing the values. For example, specifying 168.Fl d 169.Ar 15 170will enable all the debug values. 171.It Fl l 172Log all requests using 173.Xr syslog 3 174with the facility of 175.Dv LOG_FTP . 176.Sy Note : 177Logging of 178.Dv LOG_FTP 179messages 180must also be enabled in the syslog configuration file, 181.Xr syslog.conf 5 . 182.It Fl n 183Suppress negative acknowledgement of requests for nonexistent 184relative filenames. 185.It Fl o 186Disable support for RFC2347 style TFTP Options. 187.It Fl s Ar directory 188Cause 189.Nm 190to change its root directory to 191.Ar directory . 192After doing that but before accepting commands, 193.Nm 194will switch credentials to an unprivileged user. 195.It Fl S 196If 197.Nm 198runs chrooted, the option allows write requests according to generic 199file permissions, skipping requirement for files to be publicly writable. 200The option is ignored for non-chrooted run. 201.It Fl u Ar user 202Switch credentials to 203.Ar user 204(default 205.Dq Li nobody ) 206when the 207.Fl s 208option is used. 209The user must be specified by name, not a numeric UID. 210.It Fl U Ar umask 211Set the 212.Ar umask 213for newly created files. 214The default is 022 215.Pq Dv S_IWGRP | S_IWOTH . 216.It Fl w 217Allow write requests to create new files. 218By default 219.Nm 220requires that the file specified in a write request exist. 221Note that this only works in directories writable by the user 222specified with 223.Fl u 224option 225.It Fl W 226As 227.Fl w 228but append a YYYYMMDD.nn sequence number to the end of the filename. 229Note that the string YYYYMMDD can be changed with the 230.Fl F 231option. 232.El 233.Sh SEE ALSO 234.Xr tftp 1 , 235.Xr chroot 2 , 236.Xr syslog 3 , 237.Xr inetd.conf 5 , 238.Xr services 5 , 239.Xr syslog.conf 5 , 240.Xr inetd 8 241.Pp 242The following RFC's are supported: 243.Rs 244.%T RFC 1350: The TFTP Protocol (Revision 2) 245.Re 246.Rs 247.%T RFC 2347: TFTP Option Extension 248.Re 249.Rs 250.%T RFC 2348: TFTP Blocksize Option 251.Re 252.Rs 253.%T RFC 2349: TFTP Timeout Interval and Transfer Size Options 254.Re 255.Rs 256.%T RFC 7440: TFTP Windowsize Option 257.Re 258.Pp 259The non-standard 260.Cm rollover 261and 262.Cm blksize2 263TFTP options are mentioned here: 264.Rs 265.%T Extending TFTP 266.%U http://www.compuphase.com/tftp.htm 267.Re 268.Sh HISTORY 269The 270.Nm 271utility appeared in 272.Bx 4.2 ; 273the 274.Fl s 275option was introduced in 276.Fx 2.2 , 277the 278.Fl u 279option was introduced in 280.Fx 4.2 , 281the 282.Fl c 283option was introduced in 284.Fx 4.3 , 285the 286.Fl F 287and 288.Fl W 289options were introduced in 290.Fx 7.4 , 291and the 292.Fl S 293option was introduced in 294.Fx 13.3 . 295.Pp 296Support for Timeout Interval and Transfer Size Options (RFC2349) 297was introduced in 298.Fx 5.0 , 299support for the TFTP Blocksize Option (RFC2348) and the blksize2 option 300was introduced in 301.Fx 7.4 . 302.Pp 303Edwin Groothuis <edwin@FreeBSD.org> performed a major rewrite of the 304.Nm 305and 306.Xr tftp 1 307code to support RFC2348. 308.Pp 309Support for the windowsize option (RFC7440) was introduced in 310.Fx 13.0 . 311.Sh NOTES 312Files larger than 33,553,919 octets (65535 blocks, last one <512 313octets) cannot be correctly transferred without client and server 314supporting blocksize negotiation (RFCs 2347 and 2348), 315or the non-standard TFTP rollover option. 316As a kludge, 317.Nm 318accepts a sequence of block number which wrap to zero after 65535, 319even if the rollover option is not specified. 320.Pp 321Many tftp clients will not transfer files over 16,776,703 octets 322(32767 blocks), as they incorrectly count the block number using 323a signed rather than unsigned 16-bit integer. 324