<?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;
-
-<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent">
-%aptverbatiment;
-
+<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+ "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+<!ENTITY % aptent SYSTEM "apt.ent"> %aptent;
+<!ENTITY % aptverbatiment SYSTEM "apt-verbatim.ent"> %aptverbatiment;
+<!ENTITY % aptvendor SYSTEM "apt-vendor.ent"> %aptvendor;
]>
<refentry>
&apt-email;
&apt-product;
<!-- The last update date -->
- <date>2012-05-21T00:00:00Z</date>
+ <date>2015-10-15T00:00:00Z</date>
</refentryinfo>
<refmeta>
<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.
+ Starting with version 0.6, <command>APT</command> contains code that does
+ signature checking of the Release file for all repositories. This ensures
+ that data like packages in the archive can't be modified by people who
+ have no access to the Release file signing key.
+ </para>
+
+ <para>
+ If an archive has an unsigned Release file or no Release file at all
+ current APT versions will raise a warning in <command>update</command>
+ operations and front-ends like <command>apt-get</command> will require
+ explicit confirmation if an installation request includes a package from
+ such an unauthenticated archive.
</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.
+ In the future APT will refuse to work with unauthenticated repositories by
+ default until support for them is removed entirely. Users have the option to
+ opt-in to this behavior already by setting the configuration option
+ <option>Acquire::AllowInsecureRepositories</option> to <literal>false</literal>.
</para>
<para>
- The package frontends &apt-get;, &aptitude; and &synaptic; support this new
- authentication feature.
+ Note: All APT-based package management front-ends like &apt-get;, &aptitude;
+ and &synaptic; support this authentication feature, so this manpage uses
+ <literal>APT</literal> to refer to them all for simplicity only.
</para>
</refsect1>
- <refsect1><title>Trusted archives</title>
+ <refsect1><title>Trusted Repositories</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. It's the archive maintainer
- responsibility to ensure that the archive integrity is correct.
+ <para>
+ The chain of trust from an APT archive to the end user is made up of
+ several steps. <command>apt-secure</command> is the last step in
+ this chain; trusting an archive does not mean that you trust its
+ packages not to contain malicious code, but means that you
+ trust the archive maintainer. It's the archive maintainer's
+ responsibility to ensure that the archive's integrity is preserved.
</para>
<para>apt-secure does not review signatures at a
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
+ The chain of trust in Debian starts (e.g.) when a maintainer uploads a new
+ package or a new version of a package to the Debian archive. In
+ order to become effective, this upload needs to be signed by a key
+ contained in one of the Debian package maintainer keyrings (available in
+ the debian-keyring package). Maintainers' keys are signed by
other maintainers following pre-established procedures to
- ensure the identity of the key holder.
+ ensure the identity of the key holder. Similar procedures exist in all
+ Debian-based distributions.
</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.
+ the maintainer signature is stripped off, and checksums of the package
+ are computed and put in the Packages file. The checksums 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 for this &keyring-distro; release,
+ and distributed alongside the packages and the Packages files on
+ &keyring-distro; mirrors. The keys are in the &keyring-distro; archive keyring
+ available in the &keyring-package; package.
</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.
+ End users can check the signature of the Release file, extract a checksum
+ of a package from it and compare it with the checksum of the package
+ they downloaded by hand - or rely on APT doing this automatically.
</para>
<para>Notice that this is distinct from checking signatures on a
<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
+ attacks</literal>. Without signature checking, malicious
+ agents can introduce themselves into 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
+ rogue server (through ARP or DNS spoofing
attacks).</para></listitem>
<listitem><para><literal>Mirror network compromise</literal>.
</itemizedlist>
<para>However, it does not defend against a compromise of the
- Debian master server itself (which signs the packages) or against a
+ 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>
+ <refsect1><title>User Configuration</title>
<para>
+ <command>apt-key</command> is the program that manages the list of keys used
+ by APT to trust repositories. It can be used to add or remove keys as well
+ as list the trusted keys. Limiting which key(s) are able to sign which archive
+ is possible via the <option>Signed-By</option> in &sources-list;.
+ </para><para>
+ Note that a default installation already contains all keys to securely
+ acquire packages from the default repositories, so fiddling with
+ <command>apt-key</command> is only needed if third-party repositories are
+ added.
+ </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
</para>
</refsect1>
-<refsect1><title>Archive configuration</title>
+<refsect1><title>Archive Configuration</title>
<para>
If you want to provide archive signatures in an archive under your
maintenance you have to:
<command>gpg --clearsign -o InRelease Release</command> and
<command>gpg -abs -o Release.gpg Release</command>.</para></listitem>
- <listitem><para><emphasis>Publish the key fingerprint</emphasis>,
- that way your users will know what key they need to import in
- order to authenticate the files in the
- archive.</para></listitem>
+ <listitem><para>
+ <emphasis>Publish the key fingerprint</emphasis>, so that your users
+ will know what key they need to import in order to authenticate the files
+ in the archive. It is best to ship your key in its own keyring package
+ like &keyring-distro; does with &keyring-package; to be able to
+ distribute updates and key transitions automatically later.
+ </para></listitem>
+
+ <listitem><para>
+ <emphasis>Provide instructions on how to add your archive and key</emphasis>.
+ If your users can't acquire your key securely the chain of trust described above is broken.
+ How you can help users add your key depends on your archive and target audience ranging
+ from having your keyring package included in another archive users already have configured
+ (like the default repositories of their distribution) to leveraging the web of trust.
+ </para></listitem>
</itemizedlist>
- <para>Whenever the contents of the archive changes (new packages
+ <para>Whenever the contents of the archive change (new packages
are added or removed) the archive maintainer has to follow the
- first two steps previously outlined.</para>
+ first two steps outlined above.</para>
</refsect1>
<refsect1><title>See Also</title>
<para>
&apt-conf;, &apt-get;, &sources-list;, &apt-key;, &apt-ftparchive;,
-&debsign; &debsig-verify;, &gpg;
+&debsign;, &debsig-verify;, &gpg;
</para>
<para>For more background information you might want to review the
<ulink
-url="http://www.debian.org/doc/manuals/securing-debian-howto/ch7">Debian
+url="https://www.debian.org/doc/manuals/securing-debian-howto/ch7">Debian
Security Infrastructure</ulink> chapter of the Securing Debian Manual
-(available also in the harden-doc package) and the
+(also available 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>
</refentry>
-
projects / apt.git / blobdiff