--- /dev/null
+<?xml version="1.0" encoding="utf-8" standalone="no"?>
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
+ "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd" [
+
+<!ENTITY % aptent SYSTEM "apt.ent">
+%aptent;
+
+]>
+
+<refentry>
+ &apt-docinfo;
+
+ <refmeta>
+ <refentrytitle>apt-secure</refentrytitle>
+ <manvolnum>8</manvolnum>
+ </refmeta>
+
+<!-- NOTE: This manpage has been written based on the
+ Securing Debian Manual ("Debian Security
+ Infrastructure" chapter) and on documentation
+ available at the following sites:
+ http://wiki.debian.net/?apt06
+ http://www.syntaxpolice.org/apt-secure/
+ http://www.enyo.de/fw/software/apt-secure/
+-->
+<!-- TODO: write a more verbose example of how it works with
+ a sample similar to
+ http://www.debian-administration.org/articles/174
+ ?
+-->
+
+
+ <!-- Man page title -->
+ <refnamediv>
+ <refname>apt-secure</refname>
+ <refpurpose>Archive authentication support for APT</refpurpose>
+ </refnamediv>
+
+ <refsect1><title>Description</title>
+ <para>
+ Starting with version 0.6, <command>apt</command> contains code
+ that does signature checking of the Release file for all
+ archives. This ensures that packages in the archive can't be
+ modified by people who have no access to the Release file signing
+ key.
+ </para>
+
+ <para>
+ If a package comes from a archive without a signature or with a
+ signature that apt does not have a key for that package is
+ considered untrusted and installing it will result in a big
+ warning. <command>apt-get</command> will currently only warn
+ for unsigned archives, future releases might force all sources
+ to be verified before downloading packages from them.
+ </para>
+
+ <para>
+ The package frontends &apt-get;, &aptitude; and &synaptic; support this new
+ authentication feature.
+ </para>
+</refsect1>
+
+ <refsect1><title>Trusted archives</title>
+
+ <para>
+ The chain of trust from an apt archive to the end user is made up of
+ different steps. <command>apt-secure</command> is the last step in
+ this chain, trusting an archive does not mean that the packages
+ that you trust it do not contain malicious code but means that you
+ trust the archive maintainer. Its the archive maintainer
+ responsibility to ensure that the archive integrity is correct.
+ </para>
+
+ <para>apt-secure does not review signatures at a
+ package level. If you require tools to do this you should look at
+ <command>debsig-verify</command> and
+ <command>debsign</command> (provided in the debsig-verify and
+ devscripts packages respectively).</para>
+
+ <para>
+ The chain of trust in Debian starts when a maintainer uploads a new
+ package or a new version of a package to the Debian archive. This
+ upload in order to become effective needs to be signed by a key of
+ a maintainer within the Debian maintainer's keyring (available in
+ the debian-keyring package). Maintainer's keys are signed by
+ other maintainers following pre-established procedures to
+ ensure the identity of the key holder.
+ </para>
+
+ <para>
+ Once the uploaded package is verified and included in the archive,
+ the maintainer signature is stripped off, an MD5 sum of the package
+ is computed and put in the Packages file. The MD5 sum of all of the
+ packages files are then computed and put into the Release file. The
+ Release file is then signed by the archive key (which is created
+ once a year and distributed through the FTP server. This key is
+ also on the Debian keyring.
+ </para>
+
+ <para>
+ Any end user can check the signature of the Release file, extract the MD5
+ sum of a package from it and compare it with the MD5 sum of the
+ package he downloaded. Prior to version 0.6 only the MD5 sum of the
+ downloaded Debian package was checked. Now both the MD5 sum and the
+ signature of the Release file are checked.
+ </para>
+
+ <para>Notice that this is distinct from checking signatures on a
+ per package basis. It is designed to prevent two possible attacks:
+ </para>
+
+ <itemizedlist>
+ <listitem><para><literal>Network "man in the middle"
+ attacks</literal>. Without signature checking, a malicious
+ agent can introduce himself in the package download process and
+ provide malicious software either by controlling a network
+ element (router, switch, etc.) or by redirecting traffic to a
+ rogue server (through arp or DNS spoofing
+ attacks).</para></listitem>
+
+ <listitem><para><literal>Mirror network compromise</literal>.
+ Without signature checking, a malicious agent can compromise a
+ mirror host and modify the files in it to propage malicious
+ software to all users downloading packages from that
+ host.</para></listitem>
+ </itemizedlist>
+
+ <para>However, it does not defend against a compromise of the
+ Debian master server itself (which signs the packages) or against a
+ compromise of the key used to sign the Release files. In any case,
+ this mechanism can complement a per-package signature.</para>
+</refsect1>
+
+ <refsect1><title>User configuration</title>
+ <para>
+ <command>apt-key</command> is the program that manages the list
+ of keys used by apt. It can be used to add or remove keys although
+ an installation of this release will automatically provide the
+ default Debian archive signing keys used in the Debian package
+ repositories.
+ </para>
+ <para>
+ In order to add a new key you need to first download it
+ (you should make sure you are using a trusted communication channel
+ when retrieving it), add it with <command>apt-key</command> and
+ then run <command>apt-get update</command> so that apt can download
+ and verify the <filename>Release.gpg</filename> files from the archives you
+ have configured.
+ </para>
+</refsect1>
+
+<refsect1><title>Archive configuration</title>
+ <para>
+ If you want to provide archive signatures in an archive under your
+ maintenance you have to:
+ </para>
+
+ <itemizedlist>
+ <listitem><para><literal>Create a toplevel Release
+ file</literal>. if it does not exist already. You can do this
+ by running <command>apt-ftparchive release</command>
+ (provided inftp apt-utils).</para></listitem>
+
+ <listitem><para><literal>Sign it</literal>. You can do this by running
+ <command>gpg -abs -o Release.gpg Release</command>.</para></listitem>
+
+ <listitem><para><literal>Publish the key fingerprint</literal>,
+ that way your users will know what key they need to import in
+ order to authenticate the files in the
+ archive.</para></listitem>
+
+ </itemizedlist>
+
+ <para>Whenever the contents of the archive changes (new packages
+ are added or removed) the archive maintainer has to follow the
+ first two steps previously outlined.</para>
+
+</refsect1>
+
+<refsect1><title>See Also</title>
+<para>
+&apt-conf;, &apt-get;, &sources-list;, &apt-key;, &apt-archive;,
+&debsign; &debsig-verify;, &gpg;
+</para>
+
+<para>For more backgound information you might want to review the
+<ulink
+url="http://www.debian.org/doc/manuals/securing-debian-howto/ch7.en.html">Debian
+Security Infrastructure</ulink> chapter of the Securing Debian Manual
+(available also in the harden-doc package) and the
+<ulink url="http://www.cryptnet.net/fdp/crypto/strong_distro.html"
+>Strong Distribution HOWTO</ulink> by V. Alex Brennen. </para>
+
+</refsect1>
+
+ &manbugs;
+ &manauthor;
+
+</refentry>
+
</citerefentry>"
>
+<!ENTITY apt-key "<citerefentry>
+ <refentrytitle><command>apt-key</command></refentrytitle>
+ <manvolnum>8</manvolnum>
+ </citerefentry>"
+>
+
+<!ENTITY apt-secure "<citerefentry>
+ <refentrytitle>apt-secure</refentrytitle>
+ <manvolnum>8</manvolnum>
+ </citerefentry>"
+>
+
+<!ENTITY apt-archive "<citerefentry>
+ <refentrytitle><filename>apt-archive</filename></refentrytitle>
+ <manvolnum>1</manvolnum>
+ </citerefentry>"
+>
+
+
<!ENTITY sources-list "<citerefentry>
<refentrytitle><filename>sources.list</filename></refentrytitle>
<manvolnum>5</manvolnum>
<manvolnum>8</manvolnum>
</citerefentry>"
>
+
+<!ENTITY aptitude "<citerefentry>
+ <refentrytitle><command>aptitude</command></refentrytitle>
+ <manvolnum>8</manvolnum>
+ </citerefentry>"
+>
+
+<!ENTITY synaptic "<citerefentry>
+ <refentrytitle><command>synaptic</command></refentrytitle>
+ <manvolnum>8</manvolnum>
+ </citerefentry>"
+>
+
+<!ENTITY debsign "<citerefentry>
+ <refentrytitle><command>debsign</command></refentrytitle>
+ <manvolnum>1</manvolnum>
+ </citerefentry>"
+>
+
+<!ENTITY debsig-verify "<citerefentry>
+ <refentrytitle><command>debsig-verify</command></refentrytitle>
+ <manvolnum>1</manvolnum>
+ </citerefentry>"
+>
+
+<!ENTITY gpg "<citerefentry>
+ <refentrytitle><command>gpg</command></refentrytitle>
+ <manvolnum>1</manvolnum>
+ </citerefentry>"
+>
<!-- Boiler plate docinfo section -->
<!ENTITY apt-docinfo "
projects / apt.git / commitdiff
