support setting empty values (sanely) & removing support for

[apt.git] / doc / apt-secure.8.xml

diff --git a/doc/apt-secure.8.xml b/doc/apt-secure.8.xml
index 01b157789f176ef10ff21eb4d1f3526e38abb41b..9b4b7378d27637397cc9a225ff77bed5d7df331a 100644 (file)
--- a/doc/apt-secure.8.xml
+++ b/doc/apt-secure.8.xml
@@ -1,18 +1,25 @@
 <?xml version="1.0" encoding="utf-8" standalone="no"?>
 <?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;
-
+<!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>
 ]>
 
 <refentry>

- &apt-docinfo;
- 
+ <refentryinfo>
+   &apt-author.jgunthorpe;
+   &apt-author.team;
+   &apt-email;
+   &apt-product;
+   <!-- The last update date -->
+   <date>2015-10-14T00:00:00Z</date>
+ </refentryinfo>
+

  <refmeta>
    <refentrytitle>apt-secure</refentrytitle>
    <manvolnum>8</manvolnum>
  <refmeta>
    <refentrytitle>apt-secure</refentrytitle>
    <manvolnum>8</manvolnum>

+   <refmiscinfo class="manual">APT</refmiscinfo>

  </refmeta>
 
 <!-- NOTE: This manpage has been written based on the
  </refmeta>
 
 <!-- NOTE: This manpage has been written based on the


@@ -38,37 +45,43 @@
 
  <refsect1><title>Description</title>
    <para>
 
  <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 doesn't have a signed Release file or no Release file at all
+   current APT versions will raise a warning in <command>update</command>
+   operations and frontends like <command>apt-get</command> will require
+   explicit confirmation if an installation request includes a package from
+   such an unauthenticated archive.

    </para>
 
    <para>
    </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>
    </para>
 
    <para>

-   The package frontends &apt-get;, &aptitude; and &synaptic; support this new
-   authentication feature.
+   Note: All APT-based package management frontends 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>
 
    </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. Its 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
    </para>
 
    <para>apt-secure does not review signatures at a


@@ -78,31 +91,31 @@
    devscripts packages respectively).</para>
 
    <para>
    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 e.g. starts 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 maintainers keyrings (available in
+   the debian-keyring package). Maintainers' keys are signed by

    other maintainers following pre-established procedures to
    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,
    </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>
    </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
    </para>
 
    <para>Notice that this is distinct from checking signatures on a


@@ -111,11 +124,11 @@
 
     <itemizedlist>
        <listitem><para><literal>Network "man in the middle"
 
     <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
        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>.
        attacks).</para></listitem>
  
        <listitem><para><literal>Mirror network compromise</literal>.


@@ -126,26 +139,29 @@
     </itemizedlist>
 
    <para>However, it does not defend against a compromise of the
     </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>
    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>
+   <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 securily
+   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
    then run <command>apt-get update</command> so that apt can download
    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.
+   and verify the <filename>InRelease</filename> or <filename>Release.gpg</filename>
+   files from the archives you have configured.

    </para>
 </refsect1>
 
    </para>
 </refsect1>
 


@@ -156,36 +172,48 @@
    </para>
 
      <itemizedlist>
    </para>
 
      <itemizedlist>

-       <listitem><para><literal>Create a toplevel Release
-       file</literal>.  if it does not exist already. You can do this
+       <listitem><para><emphasis>Create a toplevel Release
+       file</emphasis>,  if it does not exist already. You can do this

        by running <command>apt-ftparchive release</command> 
        (provided in apt-utils).</para></listitem>
    
        by running <command>apt-ftparchive release</command> 
        (provided in apt-utils).</para></listitem>
    

-      <listitem><para><literal>Sign it</literal>. You can do this by running
+      <listitem><para><emphasis>Sign it</emphasis>. You can do this by running
+      <command>gpg --clearsign -o InRelease Release</command> and

       <command>gpg -abs -o Release.gpg Release</command>.</para></listitem>
 
       <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>
+      <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. 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 securily 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 leverage the web of trust.
+      </para></listitem>

 
     </itemizedlist>
 
 
     </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
     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> 
 
 </refsect1>
 
 <refsect1><title>See Also</title> 
 <para> 

-&apt-conf;, &apt-get;, &sources-list;, &apt-key;, &apt-archive;,
-&debsign; &debsig-verify;, &gpg;
+&apt-conf;, &apt-get;, &sources-list;, &apt-key;, &apt-ftparchive;,
+&debsign;, &debsig-verify;, &gpg;

 </para>
 
 <para>For more background information you might want to review the
 <ulink
 </para>
 
 <para>For more background information you might want to review the
 <ulink

-url="http://www.debian.org/doc/manuals/securing-debian-howto/ch7.en.html">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
 <ulink url="http://www.cryptnet.net/fdp/crypto/strong_distro.html"
 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"