SHA-1 deprecation deadline

Have you recently noticed that some of the secure websites that you frequent might have stopped working when you attempt to access them with older browsers?

December 31, 2015 was the last day that older SHA-1 certificates were accepted by many browsers, notably they must use SHA-2 for the following, older versions will see a rather unfriendly error indicating that they cannot connect to the website.

  • Microsoft Edge
  • Firefox 37+
  • Chrome 39+

You might wonder why this has occurred… it primarily comes down to risk, there were known weaknesses in the SHA-1 algorithm that can now be exploited rather cheaply on readily available hardware.


HTTP Strict Transport Security (HSTS)

The HTTP Strict Transport Security feature lets a web site inform the browser that it should never load the site using HTTP, and should automatically convert all attempts to access the site using HTTP to HTTPS requests instead.

Example Use case:
If a web site accepts a connection through HTTP and redirects to HTTPS, the user in this case may initially talk to the non-encrypted version of the site before being redirected, if, for example, the user types or even just

This opens up the potential for a man-in-the-middle attack, where the redirect could be exploited to direct a user to a malicious site instead of the secure version of the original page.

For HTTP sites on the same domain it is not recommended to add a HSTS header but to do a permanent redirect (301 status code) to the HTTPS site.

Google is always “tweaking” their search algorithms, and, at least at present time, gives greater weight to secure websites.

# Optionally load the headers module:
LoadModule headers_module modules/

<VirtualHost *:443>
# Guarantee HTTPS for 1 Year including Sub Domains
Header always set Strict-Transport-Security "max-age=31536000; includeSubdomains; preload"

Then you might (optionally, but recommended) force ALL HTTP users to HTTPS:

# Redirect HTTP connections to HTTPS
<VirtualHost *:80>
ServerAlias *
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteCond %{HTTPS} off
#RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R=301,L]
RewriteRule ^(.*)$ https://%{HTTP_HOST}$1 [redirect=301]

That’s it…


Poodle.. or rather, what’s all the fuss with SSLv3

The “Poodle” attack on websites and browsers was all over the media a few weeks ago, following in the shadow of Heartbleed.

Here’s what most users need to know… This is an vulnerability that exists in secure internet communication because…

  1. While most newer systems rely on TLS security, they still support older protocols (SSLv3 in particular for this issue)
  2. As secure communications generally attempt to find a “common” method, they will often “drop down” to older supported versions (even if they are now often considered insecure!)
  3. Most browser and server software (unless recently patched) will allow for this “drop down” in security.
  4. Most software provides a mechanism to disable this by the user or in configuration.
  5. Upgrading your software will usually remove these “problematic” vulnerabilities.

Simply put… for a consumer, it’s best to upgrade to a newer browser or find the appropriate configuration to disable SSLv3 if you are unable to upgrade. Server administrators generally should update their sofware on a regular basis for security items such as this one!

NOTE: Many CDN’s such as CloudFlare are proactive and block this vulnerability.

Technical details on the Poodle vulnerability (if you’re into that sort of thing!):

Instructions here are for Apache HTTPd 2.2.23 and newer, other servers will require a similar change:

  1. sudo vi /etc/apache2/mods-enabled/ssl.conf
  2. Change the following line from:
    SSLProtocol All -SSLv2
    SSLProtocol All -SSLv2 -SSLv3
  3. sudo service apache2 reload
  4. sudo service apache2 restart

Can be tested at the following websites:


Install free “recognized” SSL certificates for Apache2

Once you have your server running with a self-signed certificate you might find it useful to have a “real” certificate that does not warn users.

Many of the CA’s provide test certificates that are generally valid for 30-60 days, I’ve recently discovered StartSSL, that generates free certificates that are valid for a full year.

  1. Generating keys and certificates….

    NOTE: this process is rather involved and is documented better elsewhere, here’s what I needed to remember to get the keys and certificates.

    • save ssl.key (private)
    • save ssl.crt (pem encoded)
    • get file from control panel:
  2. Make sure that you move all three files to the /etc/apache2/ssl/ folder on the server.
  3. Edit the config file…
    sudo vi /etc/apache2/sites-available/default-ssl.conf

    Modify the values related to the keys and certs…

    SSLCertificateFile /etc/apache2/ssl/ssl.crt
    SSLCertificateKeyFile /etc/apache2/ssl/ssl.key
    SSLCertificateChainFile /etc/apache2/ssl/

  4. Reload the config and restart…

    sudo service apache2 reload
    sudo service apache2 restart
  5. Test it out…


Create self-signed SSL certificates for Apache on Ubuntu

To increase the security of your web applications, it is a standard process to enable HTTPS/SSL/TLS. Unfortunately, purchasing certificates can often be very expensive. Luckily, you can create a self-signed certificate for free for casual use or testing.

These steps are for Ubuntu, I wrote similar documentation for the Windows platform that you can find way back in my blog archives!

NOTE: As certificates generated in this manner are not verified by any recognized authority, many browsers will warn users (often in frightening language) about their insecurity. As stated above, these are best used only for internal use.

  1. First you will need to have apache2 installed, at a minimum you need to run:
    sudo apt-get install apache2
  2. Enable the SSL module:
    sudo a2enmod ssl

  3. Create the folder to store the keys and certificates:
    sudo mkdir /etc/apache2/ssl

  4. Generate a private key and certificate:

    sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/apache2/ssl/apache.key -out /etc/apache2/ssl/apache.crt

    Enter reasonable values for the fields in question.
    For FQDN Common Name enter * for wildcard support!

  5. Edit the config file:

    sudo vi /etc/apache2/sites-available/default-ssl.conf

  6. Un-comment or update the following lines:

    SSLCertificateFile /etc/apache2/ssl/apache.crt
    SSLCertificateKeyFile /etc/apache2/ssl/apache.key

  7. Enable to SSL website and restart:

    sudo a2ensite default-ssl.conf
    sudo service apache2 reload
    sudo service apache2 restart

  8. Test it out… provided your firewall routes port 443 to your server.


Device Fingerprinting

Often it can be beneficial to ‘more’ uniquely identify your users. For applications this is trivial, but in a web browser this can be accomplished via only a few attributes.

  • HTTP – User-Agent, IP Address, Content types and languages accepted.
  • HTTPS/SSL – the keys and encryption methods available to a specific user may vary for each client configuration.
  • HTML5 – local storage and capabilities supported.
  • Geolocation – this is included in HTML5, but also supported in many clients without full HTML5 support, or via browser extensions.
  • JavaScript – Installed version – and many DOM attributes/capabilities such as timezone, installed plugins, screen sizes and fonts from the browser can be detected.
  • Java (Applet) – Installed version – this can often be used to get additional information regarding the client system directly from the VM or Operating System itself. (* Persistent Cookies possible)
  • Flash – Installed version – this can often be used to get additional information regarding the client system directly from the Operating System itself. (* Persistent Cookies possible)
  • Silverlight (for Microsoft Windows) – – Installed version and additional information from Operating System?
  • GoogleGEARS (deprecated) – Installed version and additional information from Operating System such as Geolocation


Accessing VirtualBox client from host

Assuming that you are a developer on Windows that run a VirtualBox instance for a server, you might find it difficult to browse/access the “virtual” server that are running as a client. Here’s an example of the config required for standard HTTP, HTTPS and SSH, you can easily expand for other services as needed. Example assumes that your client is named “Ubuntu64”, you need to change appropriately for each client.

NOTE: if you are using a Linux host, the commands are similar.

cd C:\Program Files\Oracle\VirtualBox
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/ApacheHTTP/HostPort 80
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/ApacheHTTP/GuestPort 80
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/ApacheHTTP/Protocol TCP
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/ApacheHTTPS/HostPort 443
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/ApacheHTTPS/GuestPort 443
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/ApacheHTTPS/Protocol TCP
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/Tomcat/HostPort 8080
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/Tomcat/GuestPort 8080
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/Tomcat/Protocol TCP
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/SSH/HostPort 22
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/SSH/GuestPort 22
VBoxManage.exe setextradata "Ubuntu64" VBoxInternal/Devices/pcnet/0/LUN#0/Config/SSH/Protocol TCP
VBoxManage.exe getextradata "Ubuntu64" enumerate

Sniff for SSL capability of browser

If you run a secure server, you often have some non-secure content prior to authentication of a secure session. To provide a mechanism to show a page prior to authentication, you can “sniff” for the clients capability with a small bit of JavaScript.

First establish a global variable on the page:
<script type="text/javascript">
var sslok = 0;

Then, include a JavaScript file that is ONLY available via a secure
<script type="text/javascript" src=""></script>

The ‘sniff.js’ file should contain (at a minimum):
sslok = 1;

Finally, check and act on the value:
<script type="text/javascript">
if (sslok === 1) {
window.location.href = '';


MSIE’s flawed SSL implementation

This has been quite frustrating. It seems that Microsoft has again ventured from complying with the industry web standards in this space too!

The comments from the Apache HTTP 2.x ‘http-ssl.conf’ files say it all:

#   SSL Protocol Adjustments:
#   The safe and default but still SSL/TLS standard compliant shutdown
#   approach is that mod_ssl sends the close notify alert but doesn't wait for
#   the close notify alert from client. When you need a different shutdown
#   approach you can use one of the following variables:
#   o ssl-unclean-shutdown:
#     This forces an unclean shutdown when the connection is closed, i.e. no
#     SSL close notify alert is send or allowed to received.  This violates
#     the SSL/TLS standard but is needed for some brain-dead browsers. Use
#     this when you receive I/O errors because of the standard approach where
#     mod_ssl sends the close notify alert.
#   o ssl-accurate-shutdown:
#     This forces an accurate shutdown when the connection is closed, i.e. a
#     SSL close notify alert is send and mod_ssl waits for the close notify
#     alert of the client. This is 100% SSL/TLS standard compliant, but in
#     practice often causes hanging connections with brain-dead browsers. Use
#     this only for browsers where you know that their SSL implementation
#     works correctly.
#   Notice: Most problems of broken clients are also related to the HTTP
#   keep-alive facility, so you usually additionally want to disable
#   keep-alive for those clients, too. Use variable "nokeepalive" for this.
#   Similarly, one has to force some clients to use HTTP/1.0 to workaround
#   their broken HTTP/1.1 implementation. Use variables "downgrade-1.0" and
#   "force-response-1.0" for this.

SetEnvIf User-Agent ".*MSIE.*" \
nokeepalive ssl-unclean-shutdown \
downgrade-1.0 force-response-1.0

A little further research indicates that MSIE6 has (probably) partially fixed this (the HTTP/1.0 & KeepAlive issues), so the updated config should use a Regular Expression to look like…

SetEnvIf User-Agent ".*MSIE [1-5].*"
 nokeepalive ssl-unclean-shutdown
 downgrade-1.0 force-response-1.0
SetEnvIf User-Agent ".*MSIE [6-9].*"

Related Information:


Detecting browser SSL capability with JavaScript

If you run a secured website using HTTPS (aka SSL) it’s often wise to stop or notify users that are using a browser or client that doesn’t support the proper encryption level required.

Here’s a short method to “sniff” the capabilities prior to forwarding users to the secure area. You could add logic to inform the user of the problem.

As usual I’ve stripped a lot of the XHTML markup for readability.

<!– set ‘sslok’ global variable for testing SSL capability –>
<script type=”text/javascript”>
var sslok = 0;
<!– try including source javascript from secure server, this will set “sslok” to 1 if it works –>
<!– note that the /secure directory is protected so that only 128+bit SSL is allowed –>
<script type=”text/javascript” src=””></script>
<!– if ssl is 1, our javascript include worked, so SSL is successful – redirect to SSL –>
<script type=”text/javascript”>
if (sslok == ‘1’) {
window.location = ‘’;

Contents of the ‘ssl-test.js’ file:

<!– set sslok to 1, so we know this include succeeded –>
sslok = ‘1’;

NOTE: If you use the same ‘filesystem’ for HTTP & HTTPS you might want to use a server-side program (PHP or Java for example) to generate the JavaScript.  Benefit of that process would be that you could also interrogate and return other SSL attributes such as cypher strength.