FAQ

Revision 45 as of 2009-09-13 17:38:28

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Official Support

  • What does official security support mean?
    • Members of the Ubuntu Security team are Canonical employees who provide security updates for supported software in the Ubuntu distribution. Security updates are in part prioritized based on severity of impact, exploitability and number of affected users.

  • What software is officially supported by the Ubuntu Security team?
    • Ubuntu is currently divided into four components: main, restricted, universe and multiverse. Packages in main and restricted are supported by the Ubuntu Security team for the life of an Ubuntu release, while packages in universe and multiverse are supported by the Ubuntu community.

  • Who can receive official support?

Repositories

  • How are the "-updates" and "-security" pockets different?
    • -updates includes things that have gone through the StableReleaseUpdates process, and contain various important bug fixes.

    • -security includes only updated packages that contain security-related fixes, and are built to not require anything from "-updates".

  • How are components and pockets used in the builds, and how do they affect security updates?
    • When packages are built, only certain components are available during the build:
      • main: built with only the main component enabled

      • restricted: built with main and restricted components enabled

      • universe: built with main and universe components enabled

      • multiverse: built with main, restricted, universe and multiverse components enabled

    • Ubuntu also has several pockets that further divide the archive: release, security, updates, proposed and backports. The pocket can be found by looking at the Distribution entry of a source package. The release pocket is simply the name of the release, and the other pockets are denoted by <release name>-<pocket>. For example, the release pocket for Ubuntu 8.04 LTS, the Hardy Heron, is simply hardy, while the security pocket for Ubuntu 8.04 LTS is hardy-security. Packages in release, security and updates are supported by the Ubuntu Security team, while packages in backports are supported by the community and packages in proposed are the responsibility of the uploader. When packages are built, only certain pockets are available during the build:

      • release: during the development cycle, this is the only pocket that is used. Once the development version is released, the release pocket is frozen and does not change.

      • security: built with release and security. UpdateProcedures gives the process used for creating security updates.

      • proposed: built with release, security, and updates

      • updates: packages in updates are not directly built, but rather copied from proposed after they have been tested. See StableReleaseUpdates for details.

      • backports: built with release, security, and updates. See UbuntuBackports for details.

  • How do I automatically install security updates?

Packages

Versions

Ubuntu releases security updates by patching specific issues rather than updating whole versions of software. This is to keep the packages in a stable release as close to their original version as possible to avoid introducing unintended regressions. For more details, see Stable Release Updates.

Architectures

Ubuntu is built for many architectures. Officially supported architectures for a particular release of Ubuntu can be found in http://archive.ubuntu.com/ubuntu/dists/<release>/main/ and ported architectures (where maintenance is best-effort) are in http://ports.ubuntu.com/dists/<release>/main/.

Release

amd64

armel

hppa

i386

ia64

lpia

powerpc

sparc

Dapper

yes

--

ports

yes

ports

--

yes

yes

Edgy1

yes

--

ports

yes

ports

--

yes

yes

Feisty1

yes

--

ports

yes

ports

--

ports

yes

Gutsy1

yes

--

ports

yes

ports

--

ports

yes

Hardy

yes

--

ports

yes

ports

yes2

ports

ports

Intrepid

yes

--

ports

yes

ports

yes2

ports

ports

Jaunty

yes

ports

ports

yes

ports

ports

ports

ports

Karmic

yes

ports

--

yes

ports

ports

ports

ports

  1. Release has reached end of life and is no longer officially maintained
  2. While LPIA is listed in ports.ubuntu.com for this release, it should be considered a supported architecture

Endianness

Sometimes a security vulnerability affects a particular architecture or endianness. Most architectures in Ubuntu are little-endian, some are so-called bi-endian and some big-endian. In Ubuntu, the endianness of a particular architecture can be see in the following table:

Architecture (hardware name)

Little Endian

Big Endian

amd64 (x86_64)

yes

--

armel (armv5tel)

yes

--

hppa (parisc)

--

yes

i386 (i686)

yes

--

ia64

yes

--

lpia

yes

--

powerpc (ppc64)

--

yes

sparc (sparc64)

--

yes

Software

SSH

  • When I run ssh HOST sudo CMD..., I can see the password as I type it. How do I fix that?

    • There is no "tty" allocated when running commands directly via ssh, please add the "-t" flag.

  • When I connect to my ssh server port, I can see a banner with the exact version I'm running. Can we include a patch to disable the version number?
    • There is an upstream bug that gets into detail about this feature, but Ubuntu does not want to carry the patches unless upstream approves.

    • Hiding the version number is Security through obscurity, which is not real security.

    • SSH clients, including OpenSSH, usually parse the version string in order to identify known bugs/features with a particular version of the server. Changing the values could introduce communication problems with certain clients. See compat.c in the OpenSSH source code.

Sudo

  • Why does Ubuntu disable the root account and use sudo instead?
    • See RootSudo for a thorough discussion, but simply put, sudo offers many benefits including (but not limited to):

      • protecting the user from accidentally damaging parts of the system
      • providing a log audit trail
      • preventing brute-force login and ssh attacks to a well known account
      • authentication timeouts
      • fine-grained granting of privileges
  • I am not prompted for my password when I run "sudo" for a second time!
    • sudo is design to keep a "ticket" valid for 15 minutes after you use your password the first time. This is configurable. Please read man sudoers:

      timestamp_timeout
          Number of minutes that can elapse before sudo will ask
          for a passwd again.  The default is 15.  Set this to 0
          to always prompt for a password.  If set to a value
          less than 0 the user’s timestamp will never expire.
          This can be used to allow users to create or delete
          their own timestamps via sudo -v and sudo -k respec‐
          tively.
  • If sudo authentication does not immediately expire, doesn't that allow for privilege escalation for malware and local users?
    • Giving untrusted users access to your account or running untrusted code can allow privilege escalation via sudo, but Ubuntu does not (and by default cannot) provide protections against users running code as themselves. Some protections against these sort of attacks are:
      • do not open files or run/install programs from untrusted sources
      • enable locking of your screensaver
      • using 'sudo -k' or 'sudo -K' to remove the timestamps (see 'man sudo' for details)
      • adjusting timestamp_timeout in /etc/sudoers (using visudo) (see above, and 'man sudoers' for details)
      • using a virus scanner such as clamav on your files
      • protecting specific applications with Apparmor or SELinux

Rescue Mode

  • I am not prompted for a password when going into rescue mode!
    • This is related to 'sudo', above. Because in Ubuntu there is no root password, there is nothing to prompt for. In general, not prompting for a password in single user mode does not decrease security because it requires physical access to the machine. An attacker with physical access can bypass this restriction easily (eg with bootable media or removing the hard drive). If you decide to set a root password, you will be prompted for it in rescue mode.

UFW

  • Why is the ufw firewall not enabled by default?

    • ufw is available in all new installations of Ubuntu since 8.04 LTS, but is disabled by default. The standard Ubuntu installation has a no open service ports policy, so enabling the firewall by default doesn't gain any extra security in the default installation, but could provide confusion for people new to Ubuntu when new software that is installed does not work because of restrictive firewall rules. As a result, when first adding ufw to Ubuntu it was decided that users must 'opt-in' to using the firewall. In Ubuntu 9.04 and later, you can enable ufw during installation using preseeding. See /usr/share/doc/ufw/README.Debian for details.

Design

Many common issues come up that may seem to be security design problems, but are actually done intentionally. Please review the Ubuntu Security Policies.


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