Picture of Jürgen Kreileder

Archive for the ‘Debian’ Category

Debian Testing Gets Security Support

The Debian Testing Security Team just announced the beginning of full security support for Debian’s “testing” distribution!

The lack of security support was one of the main problems with “testing”. You had to pull security fixes from “unstable” or even build your own packages to keep it secure.

I hope they have the manpower to keep up with security issues. Debian’s main security team, which only provides updates for the “stable” distribution, had some problems over the last months.

Debian Installer With Kernel 2.6.11

As mentioned recently, Debian Sarge’s installer doesn’t work on my Dell Inspiron 9300. I like Debian but I think it’s a shame that the sarge installer was already outdated on the day of its release.

The official sarge installer still uses a 2.4 kernel by default but includes a 2.6 kernel that can be used by booting with "install26" or "expert26". But even that kernel, 2.6.8, is too old for the Inspiron 9300. It still doesn’t recognize the hard disk.

Ubuntu’s installer, which uses a 2.6.11 kernel, works fine on the machine. Although Ubuntu is a nice distribution, I like pure Debian better. Unfortunately I wasn’t able to find any 2.6.11 based Debian installer on the net, even a question on debian-boot yielded nothing.

Anyhow, I finally had the time to build one myself:
debian-2.6.11-i386-businesscard.iso (GPG signature)

The image is basically a sarge businesscard ISO with a 2.6.11 kernel from Debian testing instead of the original 2.6.8 kernel.

Unlike with Ubuntu, installation on the Inspiron 9300 still doesn’t work out of the box but with a few tricks I was able to install Debian sarge:

  • Boot with expert26
  • When the installer starts up, switch to the second console (Alt-F2) and enter these commands:
    ~ # modprobe ide_generic
    ~ # modprobe ata_piix

    Without this the installer won’t find the CD-ROM.

  • If network configuration via DHCP fails, just retry — worked for me
  • When asked what version of Debian you would like to install, choose stable. Installing testing or unstable directly doesn’t work.
  • It doesn’t matter which kernel you choose to install, we have to replace it with a 2.6.11 kernel later anyway
  • Just before the first reboot, that means right after the installer ejects the CD-ROM, switch back to console two. Now download and install the latest available Debian kernel. I’ve used 2.6.11-1-686:
    ~ # mount -t proc proc /target/proc
    ~ # chroot /target
    sh-2.05b# cd /root
    sh-2.05b# wget http://blog.blackdown.de/static/debian/kernel-image-2.6.11-1-686_2.6.11-7_i386.deb
    sh-2.05b# dpkg -i kernel-image-2.6.11-1-686_2.6.11-7_i386.deb
    …
    sh-2.05b# exit
    ~ # umount /target/proc
  • Reboot (using the kernel just installed) and complete the installation
  • Upgrade to testing or unstable
  • Build a custom kernel (2.6.12 or newer). It’s probably a good idea to include some additional libata patches. To get the DVD drive working you have to apply this patch.

Debian Packages for J2SE 1.4.2-02

Thanks to Matthias Klose, Debian packages for Blackdown J2SE-1.4.2-02 are available now. Just add something like

deb ftp://ftp.tux.org/java/debian/ sarge non-free

to your /etc/apt/sources.list.

Upgrading is recommended as 1.4.2-02 contains an important security fix.

The Sky Is Falling

  • Debian Sarge is released (unfortunately the installer doesn’t like my Inspiron 9300)
  • Apple is switching to Intel CPUs

Securing WordPress Admin Access With SSL

January 22nd, 2006: There’s an updated version of this guide for WordPress 2 now: Securing WordPress 2 Admin Access With SSL

As one can guess from the look of this site, I’m using as my blog engine. At this time WordPress does not support HTTPS access to the admin area when the rest of the blog is served via normal HTTP. This is a bit unfortunate. I do not like logging in to my server over unencrypted connections, especially not when using public WLANs. Getting around this WordPress limitation requires quite a few steps:

The Goal

All communication involving passwords or authentication cookies should be done over HTTPS connections. wp-login.php and the wp-admin directory should only be accessible over HTTPS.
Normal reading access, as well as comments, tracebacks, and pingbacks still should go over ordinary HTTP.

The Plan

  • Add an HTTPS virtual host that forwards requests to the HTTP virtual host
  • Modify WordPress to send secure authentication cookies, so cookies never get sent over insecure connections accidentally
  • Require a valid certificate on HTTPS clients. That means to log in to WordPress you need both a valid certificate and a valid password. If someone manages to get your password, he still can not login because he does not have a valid certificate.

The Implementation

Note: This documentation assumes a Debian sarge installation with 2. Some things, in particular Apache module related ones, will be different on other systems.
The server used throughout the instructions is example.org/192.0.34.166. The server’s DocumentRoot is /blog and WordPress resides in /blog/wp. The value of WordPress’ home option is ‘http://example.org’ and the value of its site_url option is ‘http://example.org/wp’.

  • Prepare the SSL certificates:
    • Generate your own certificate authority (CA) if you don’t have one already (I’m using the makefile from OpenSSL Certificate Authority Setup for managing mine) and import it into your browser.
    • Generate a certificate for the SSL server and certify it with your private CA.
    • Generate a certificate for your browser and certify it with your private CA. Most browsers expect a PKCS#12 file, so generate one with
      $ openssl pkcs12 -export -clcerts \
          -in blogclient.cert \
          -inkey blogclient.key \
          -out blogclient.p12

      Then import blogclient.p12 into your browser.

  • Make WordPress SSL-ready:
    Apply this patch to the WordPress code. It makes the following changes:

    • Use secure authentication cookies in wp_setcookie()
    • Make check_admin_referer() working with HTTPS URLs
    • Disable login over XML-RPC
  • Enable the necessary Apache modules:
    • Install mod_proxy_html. It will be used to replace absolute ‘http://example.org’ HTTP URLs in the WordPress output with ‘https://example.org’ HTTPS URLs:
      $ aptitude install libapache2-mod-proxy-html

      The module gets enabled automatically after installation.

    • Enable mod_proxy and mod_ssl
      $ a2enmod proxy
      $ a2enmod ssl

      Debian provides sane default configurations for both modules. You might want to take a look at the configuration files (ssl.conf and proxy.conf) nevertheless.

    • If you are compressing WordPress output (that is if you enabled the ‘WordPress should compress articles (gzip) if browsers ask for them’ option) then also enable mod_headers:
      $ a2enmod headers
  • Configure Apache to listen on the HTTPS port
    $ cat > /etc/apache2/conf.d/ssl.conf << EOF
    <IfModule mod_ssl.c>
    	Listen 443
    </IfModule>
    EOF
  • Modify the blog virtual host to limit access to wp-login.php and wp-admin to the local host. Also completely deny access to files which should never be accessed directly. Here is an example: 10-example.org
  • Now setup the HTTPS virtual server: 20-example.org-ssl
    If you are compressing WordPress output you have to enable the RequestHeader line.
  • Enable the site and restart Apache
    $ a2ensite 20-blog-ssl
    $ /etc/init.d/apache2 restart
  • Remove the old WP cookies from your browser
  • Test the new setup!