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diff --git a/doc/apt-secure.8.xml b/doc/apt-secure.8.xml new file mode 100644 index 000000000..c1d46cb45 --- /dev/null +++ b/doc/apt-secure.8.xml @@ -0,0 +1,200 @@ +<?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> + |