TFTPD(8) NetBSD System Manager's Manual TFTPD(8)
NAME
tftpd -- DARPA Internet Trivial File Transfer Protocol server
SYNOPSIS
tftpd [-bcdln] [-g group] [-p pathsep] [-s directory] [-u user] [directory ...]
DESCRIPTION
tftpd is a server which supports the DARPA Trivial File Transfer Proto- col. The TFTP server operates at the port indicated in the `tftp' ser- vice 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 appro- priate on all systems, and its implications should be considered before enabling tftp service. The server should have the user ID with the low- est possible privilege. Access to files may be restricted by invoking tftpd with a list of direc- tories 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 Allow clients which return acknowledgements to the broad- cast address to communicate with the tftp server. Some tftp clients, notably ones resident in the ROMs of older Cisco equipment, return their acknowledgements to the broadcast address rather than the server's unicast address. -c Allow unrestricted creation of new files. Without this flag, only existing publicly writable files can be over- written. -d Enable verbose debugging messages to syslogd(8). -g group Change gid to that of group on startup. If this isn't specified, the gid is set to that of the user specified with -u. -l Logs all requests using syslog(3). -n Suppresses negative acknowledgement of requests for nonex- istent relative filenames. -p pathsep All occurrences of the single character pathsep (path sep- arator) in the requested filename are replaced with `/'. -s directory tftpd 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 Change uid to that of user on startup. If -u isn't given, user defaults to ``nobody''. If -g isn't also given, change the gid to that of user as well.
SEE ALSO
tftp(1), inetd(8) 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.
HISTORY
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.
BUGS
Files larger than 33,553,919 octets (65535 blocks, last one less than 512 octets) cannot be correctly transferred without client and server sup- porting 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.
SECURITY CONSIDERATIONS
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 dif- ficult 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 man- ner if this is used in an insecure environment. NetBSD 10.1 May 5, 2015 NetBSD 10.1
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