tftpd.tproj/tftpd.8

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  30 .\"     from: @(#)tftpd.8       8.1 (Berkeley) 6/4/93
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  32 .Dd June 11, 2003
  33 .Dt TFTPD 8
  34 .Os
  35 .Sh NAME
  36 .Nm tftpd
  37 .Nd
  38 .Tn DARPA
  39 Internet Trivial File Transfer Protocol server
  40 .Sh SYNOPSIS
  41 .Nm
  42 .Op Fl d
  43 .Op Fl g Ar group
  44 .Op Fl i
  45 .Op Fl l
  46 .Op Fl n
  47 .Op Fl s Ar directory
  48 .Op Fl u Ar user
  49 .Op Ar directory ...
  50 .Sh DESCRIPTION
  51 .Nm
  52 is a server which supports the
  53 .Tn DARPA
  54 Trivial File Transfer Protocol.
  55 The
  56 .Tn TFTP
  57 server operates at the port indicated in the
  58 .Ql tftp
  59 service description; see
  60 .Xr services 5 .
  61 The server is normally started by
  62 .Xr inetd 8 .
  63 .Pp
  64 The use of
  65 .Xr tftp 1
  66 does not require an account or password on the remote system.
  67 Due to the lack of authentication information,
  68 .Nm
  69 will allow only publicly readable files to be accessed.
  70 Filenames beginning in ``\|\fB.\|.\fP\|/'' or
  71 containing ``/\|\fB.\|.\fP\|/'' are not allowed.
  72 Files may be written to only if they already exist and are publicly writable.
  73 .Pp
  74 Note that this extends the concept of
  75 .Qq public
  76 to include
  77 all users on all hosts that can be reached through the network;
  78 this may not be appropriate on all systems, and its implications
  79 should be considered before enabling tftp service.
  80 The server should have the user ID with the lowest possible privilege.
  81 .Pp
  82 Access to files may be restricted by invoking
  83 .Nm
  84 with a list of directories by including up to 20 pathnames
  85 as server program arguments in
  86 .Pa /etc/inetd.conf .
  87 In this case access is restricted to files whose
  88 names are prefixed by the one of the given directories.
  89 The given directories are also treated as a search path for
  90 relative filename requests.
  91 .Pp
  92 The options are:
  93 .Bl -tag -width "directory"
  94 .It Fl d
  95 Enable verbose debugging messages to
  96 .Xr syslogd 8 .
  97 .It Fl g Ar group
  98 Change gid to that of
  99 .Ar group
 100 on startup.
 101 If this isn't specified, the gid is set to that of the
 102 .Ar user
 103 specified with
 104 .Fl u .
 105 .It Fl i
 106 Enable insecure mode, no
 107 .Xr realpath 3 .
 108 .It Fl l
 109 Logs all requests using
 110 .Xr syslog 3 .
 111 .It Fl n
 112 Suppresses negative acknowledgement of requests for nonexistent
 113 relative filenames.
 114 .It Fl s Ar directory
 115 .Nm
 116 will
 117 .Xr chroot 2
 118 to
 119 .Ar directory
 120 on startup.
 121 This is recommended for security reasons (so that files other than
 122 those in the
 123 .Pa /tftpboot
 124 directory aren't accessible).
 125 If the remote host passes the directory name as part of the
 126 file name to transfer, you may have to create a symbolic link
 127 from
 128 .Sq tftpboot
 129 to
 130 .Sq \&.
 131 under
 132 .Pa /tftpboot .
 133 .It Fl u Ar user
 134 Change uid to that of
 135 .Ar user
 136 on startup.
 137 If
 138 .Fl u
 139 isn't given,
 140 .Ar user
 141 defaults to
 142 .Dq nobody .
 143 If
 144 .Fl g
 145 isn't also given, change the gid to that of
 146 .Ar user
 147 as well.
 148 .El
 149 .Sh SEE ALSO
 150 .Xr tftp 1 ,
 151 .Xr inetd 8
 152 .Rs
 153 .%R RFC
 154 .%N 1350
 155 .%D July 1992
 156 .%T "The TFTP Protocol (Revision 2)"
 157 .Re
 158 .Rs
 159 .%R RFC
 160 .%N 2347
 161 .%D May 1998
 162 .%T "TFTP Option Extension"
 163 .Re
 164 .Rs
 165 .%R RFC
 166 .%N 2348
 167 .%D May 1998
 168 .%T "TFTP Blocksize Option"
 169 .Re
 170 .Rs
 171 .%R RFC
 172 .%N 2349
 173 .%D May 1998
 174 .%T "TFTP Timeout Interval and Transfer Size Options"
 175 .Re
 176 .Sh HISTORY
 177 The
 178 .Nm
 179 command appeared in
 180 .Bx 4.2 .
 181 .Pp
 182 The
 183 .Fl s
 184 flag appeared in
 185 .Nx 1.0 .
 186 .Pp
 187 The
 188 .Fl g
 189 and
 190 .Fl u
 191 flags appeared in
 192 .Nx 1.4 .
 193 .Pp
 194 IPv6 support was implemented by WIDE/KAME project in 1999.
 195 .Pp
 196 TFTP options were implemented by Wasabi Systems, Inc., in 2003,
 197 and first appeared in
 198 NetBSD 2.0 .
 199 .Sh BUGS
 200 Files larger than 33488896 octets (65535 blocks) cannot be transferred
 201 without client and server supporting blocksize negotiation (RFCs
 202 2347 and 2348).
 203 .Pp
 204 Many tftp clients will not transfer files over 16744448 octets (32767 blocks).
 205 .Sh SECURITY CONSIDERATIONS
 206 You are
 207 .Em strongly
 208 advised to set up
 209 .Nm
 210 using the
 211 .Fl s
 212 flag in conjunction with the name of the directory that
 213 contains the files that
 214 .Nm
 215 will serve to remote hosts (e.g.,
 216 .Pa /tftpboot ) .
 217 This ensures that only the files that should be served
 218 to remote hosts can be accessed by them.
 219 .Pp
 220 Because there is no user-login or validation within
 221 the
 222 .Tn TFTP
 223 protocol, the remote site will probably have some
 224 sort of file-access restrictions in place.
 225 The exact methods are specific to each site and therefore
 226 difficult to document here.