tftpd.tproj/tftpd.8

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  32 .\"     @(#)tftpd.8     8.1 (Berkeley) 6/4/93
  33 .\" $FreeBSD: src/libexec/tftpd/tftpd.8,v 1.16 2002/07/06 19:19:43 charnier Exp $
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  35 .Dd September 14, 2000
  36 .Dt TFTPD 8
  37 .Os
  38 .Sh NAME
  39 .Nm tftpd
  40 .Nd Internet Trivial File Transfer Protocol server
  41 .Sh SYNOPSIS
  42 .Nm /usr/libexec/tftpd
  43 .Op Fl cCln
  44 .Op Fl s Ar directory
  45 .Op Fl u Ar user
  46 .Op Ar directory ...
  47 .Sh DESCRIPTION
  48 The
  49 .Nm
  50 utility is a server which supports the
  51 Internet Trivial File Transfer
  52 Protocol
  53 .Pq Tn RFC 1350 .
  54 The
  55 .Tn TFTP
  56 server operates
  57 at the port indicated in the
  58 .Ql tftp
  59 service description;
  60 see
  61 .Xr services 5 .
  62 The server is normally started by
  63 .Xr inetd 8 .
  64 .Pp
  65 The use of
  66 .Xr tftp 1
  67 does not require an account or password on the remote system.
  68 Due to the lack of authentication information,
  69 .Nm
  70 will allow only publicly readable files to be
  71 accessed.
  72 Files containing the string ``/\|\fB.\|.\fP\|/'' or starting with
  73 ``\|\fB.\|.\fP\|/'' are not allowed.
  74 Files may be written only if they already exist and are publicly writable.
  75 Note that this extends the concept of
  76 .Dq public
  77 to include
  78 all users on all hosts that can be reached through the network;
  79 this may not be appropriate on all systems, and its implications
  80 should be considered before enabling tftp service.
  81 The server should have the user ID with the lowest possible privilege.
  82 .Pp
  83 Access to files may be restricted by invoking
  84 .Nm
  85 with a list of directories by including up to 20 pathnames
  86 as server program arguments in
  87 .Pa /etc/inetd.conf .
  88 In this case access is restricted to files whose
  89 names are prefixed by the one of the given directories.
  90 The given directories are also treated as a search path for
  91 relative filename requests.
  92 .Pp
  93 The
  94 .Fl s
  95 option provides additional security by changing
  96 .Nm Ns No 's
  97 root directory, thereby prohibiting accesses outside of the specified
  98 .Ar directory .
  99 Because
 100 .Xr chroot 2
 101 requires super-user privileges,
 102 .Nm
 103 must be run as root.
 104 However, after performing the
 105 .Fn chroot ,
 106 .Nm
 107 will set its user id to that of the specified
 108 .Ar user ,
 109 or
 110 .Dq nobody
 111 if no
 112 .Fl u
 113 option is specified.
 114 .Pp
 115 The options are:
 116 .Bl -tag -width Ds
 117 .It Fl c
 118 Changes the default root directory of a connecting host via chroot based on the
 119 connecting IP address.
 120 This prevents multiple clients from writing to the same file at the same time.
 121 If the directory does not exist, the client connection is refused.
 122 The
 123 .Fl s
 124 option is required for
 125 .Fl c
 126 and the specified
 127 .Ar directory
 128 is used as a base.
 129 .It Fl C
 130 Operates the same as
 131 .Fl c
 132 except it falls back to
 133 .Fl s Ns No 's
 134 .Ar directory
 135 if a directory does not exist for the client's IP.
 136 .It Fl l
 137 Log all requests using
 138 .Xr syslog 3
 139 with the facility of
 140 .Dv LOG_FTP .
 141 Note: Logging of
 142 .Dv LOG_FTP
 143 messages
 144 must also be enabled in the syslog configuration file,
 145 .Xr syslog.conf 5 .
 146 .It Fl n
 147 Suppress negative acknowledgement of requests for nonexistent
 148 relative filenames.
 149 .It Fl s Ar directory
 150 Cause
 151 .Nm
 152 to change its root directory to
 153 .Pa directory .
 154 After changing roots but before accepting commands,
 155 .Nm
 156 will switch credentials to an unprivileged user.
 157 .It Fl u Ar user
 158 Switch credentials to
 159 .Ar user
 160 (default
 161 .Dq nobody )
 162 when the
 163 .Fl s
 164 option is used.
 165 The user must be specified by name, not a numeric UID.
 166 .El
 167 .Sh SEE ALSO
 168 .Xr tftp 1 ,
 169 .Xr chroot 2 ,
 170 .Xr inetd 8 ,
 171 .Xr syslogd 8
 172 .Rs
 173 .%A K. R. Sollins
 174 .%T The TFTP Protocol (Revision 2)
 175 .%D July 1992
 176 .%O RFC 1350, STD 33
 177 .Re
 178 .Sh HISTORY
 179 The
 180 .Nm
 181 utility appeared in
 182 .Bx 4.2 ;
 183 the
 184 .Fl s
 185 option was introduced in
 186 .Fx 2.2 ,
 187 the
 188 .Fl u
 189 option was introduced in
 190 .Fx 4.2 ,
 191 and the
 192 .Fl c
 193 option was introduced in
 194 .Fx 4.3 .
 195 .Sh BUGS
 196 Files larger than 33488896 octets (65535 blocks) cannot be transferred
 197 without client and server supporting blocksize negotiation (RFC1783).
 198 .Pp
 199 Many tftp clients will not transfer files over 16744448 octets (32767 blocks).