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152 lines
5.0 KiB
152 lines
5.0 KiB
<refentry id="tftpd">
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<refmeta>
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<refentrytitle>tftpd</refentrytitle>
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<manvolnum>8</manvolnum>
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<refmiscinfo>iputils-&snapshot;</refmiscinfo>
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</refmeta>
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<refnamediv>
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<refname>tftpd</refname>
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<refpurpose>Trivial File Transfer Protocol server</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<cmdsynopsis>
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<command>tftpd</command>
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<arg choice="req"><replaceable/directory/</arg>
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</cmdsynopsis>
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</refsynopsisdiv>
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<refsect1><title>DESCRIPTION</title>
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<para>
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<command/tftpd/ is a server which supports the DARPA
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Trivial File Transfer Protocol
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(<ulink url="http://tools.ietf.org/rfc/rfc1350.txt">RFC1350</ulink>).
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The TFTP server is started
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by <citerefentry><refentrytitle/inetd/<manvolnum/8/</citerefentry>.
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</para>
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<para>
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<replaceable/directory/ is required argument; if it is not given
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<command/tftpd/ aborts. This path is prepended to any file name requested
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via TFTP protocol, effectively chrooting <command/tftpd/ to this directory.
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File names are validated not to escape out of this directory, however
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administrator may configure such escape using symbolic links.
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</para>
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<para>
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It is in difference of variants of <command/tftpd/ usually distributed
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with unix-like systems, which take a list of directories and match
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file names to start from one of given prefixes or to some random
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default, when no arguments were given. There are two reasons not to
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behave in this way: first, it is inconvenient, clients are not expected
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to know something about layout of filesystem on server host.
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And second, TFTP protocol is not a tool for browsing of server's filesystem,
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it is just an agent allowing to boot dumb clients.
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</para>
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<para>
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In the case when <command/tftpd/ is used together with
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<link linkend="rarpd">
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<citerefentry><refentrytitle/rarpd/<manvolnum/8/</citerefentry></link>,
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tftp directories in these services should coincide and it is expected
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that each client booted via TFTP has boot image corresponding
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its IP address with an architecture suffix following Sun Microsystems
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conventions. See
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<link linkend="rarpd">
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<citerefentry><refentrytitle/rarpd/<manvolnum/8/</citerefentry></link>
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for more details.
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</para>
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</refsect1>
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<refsect1><title>SECURITY</title>
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<para>
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TFTP protocol does not provide any authentication.
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Due to this capital flaw <command/tftpd/ is not able to restrict
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access to files and will allow only publically readable
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files to be accessed. Files may be written only if they already
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exist and are publically writable.
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</para>
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<para>
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Impact is evident, directory exported via TFTP <emphasis/must not/
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contain sensitive information of any kind, everyone is allowed
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to read it as soon as a client is allowed. Boot images do not contain
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such information as rule, however you should think twice before
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publishing f.e. Cisco IOS config files via TFTP, they contain
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<emphasis/unencrypted/ passwords and may contain some information
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about the network, which you were not going to make public.
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</para>
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<para>
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The <command/tftpd/ server should be executed by <command/inetd/
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with dropped root privileges, namely with a user ID giving minimal
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access to files published in tftp directory. If it is executed
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as superuser occasionally, <command/tftpd/ drops its UID and GID
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to 65534, which is most likely not the thing which you expect.
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However, this is not very essential; remember, only files accessible
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for everyone can be read or written via TFTP.
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</para>
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</refsect1>
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<refsect1><title>SEE ALSO</title>
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<para>
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<link linkend="rarpd">
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<citerefentry><refentrytitle/rarpd/<manvolnum/8/</citerefentry></link>,
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<citerefentry><refentrytitle/tftp/<manvolnum/1/</citerefentry>,
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<citerefentry><refentrytitle/inetd/<manvolnum/8/</citerefentry>.
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</para>
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</refsect1>
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<refsect1><title>HISTORY</title>
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<para>
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The <command/tftpd/ command appeared in 4.2BSD. The source in iputils
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is cleaned up both syntactically (ANSIized) and semantically (UDP socket IO).
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</para>
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<para>
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It is distributed with iputils mostly as good demo of an interesting feature
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(<constant/MSG_CONFIRM/) allowing to boot long images by dumb clients
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not answering ARP requests until they are finally booted.
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However, this is full functional and can be used in production.
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</para>
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</refsect1>
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<refsect1><title>AVAILABILITY</title>
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<para>
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<command/tftpd/ is part of <filename/iputils/ package
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and the latest versions are available in source form at
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<ulink url="http://www.skbuff.net/iputils/iputils-current.tar.bz2">
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http://www.skbuff.net/iputils/iputils-current.tar.bz2</ulink>.
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</para>
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</refsect1>
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<![IGNORE[
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<refsect1><title>COPYING</title>
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<para>
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<literallayout>
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This documentation is free software; you can redistribute
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it and/or modify it under the terms of the GNU General Public
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License Version 2.
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This program is distributed in the hope that it will be
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useful, but WITHOUT ANY WARRANTY; without even the implied
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warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
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See the GNU General Public License for more details.
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For more details see the file COPYING in the source
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distribution of Linux kernel of version 2.4.
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</literallayout>
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</literallayout>
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</para>
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</refsect1>
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]]>
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</refentry>
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