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Month: July 2015

Strong TLS/SSL Security on your server

SSL Report : www.linuxwebhostingsupport.in

ssllab

 

 

 

 

This is a simple guide for setting up a strong TLS/SSL configuration on your server.

If you configure a web server’s TLS configuration, you have primarily to take care of three things:

1. disable SSL 2.0 (FUBAR) and SSL 3.01 (POODLE),
2. disable TLS 1.0 compression (CRIME),
3. disable weak ciphers (DES, RC4), prefer modern ciphers (AES), modes (GCM), and protocols (TLS 1.2).

 

Your Server’s Certificate

Let’s start with your digital certificate, which is at the core of HTTPS. The certificate enables clients to verify the identity of servers, through a chain of trust from your server’s certificate through intermediate certificates and up to a root certificate trusted by users’ browsers. Your server certificate should be 2048 bits in length. Using 4096 bit certificate is more secure however it require more computation times and hence slow compared to 2048 bit certs.

 

Basic HTTPS Setup

Here are basic SSL configurations, first for Apache:

;
...
SSLEngine on
SSLCertificateFile /etc/ssl/certs/your_cert
SSLCertificateChainFile /etc/ssl/certs/chained_certs
SSLCertificateKeyFile /etc/ssl/certs/your_private_key
<;/VirtualHost>;

And then for Nginx:

server {
...
ssl on;
ssl_certificate /etc/ssl/certs/your_cert_with_chain;
ssl_certificate_key /etc/ssl/certs/your_private_key;
ssl_session_cache shared:SSL:50m;
ssl_session_timeout 10m;
}

In Nginx, the ssl_certificate parameter is confusing. It expects your certificate plus any necessary intermediate certificates, concatenated together.

Make sure all of these files are at least mode 0444, except your private key, which should be 0400.

 

Software versions

On the server side you should update your OpenSSL to 1.0.1c+ so you can support TLS 1.2, GCM, and ECDHE as soon as possible. Fortunately that’s already the case in Ubuntu 12.04 and later.

On the client side the browser vendors are starting to catch up. As of now, Chrome 30, Internet Explorer 11 on Windows 8, Safari 7 on OS X 10.9, and Firefox 26 all support TLS 1.2.

 

Cipher Suite Configuration

The recommended cipher suites for Apache are follows

SSLCipherSuite EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH
SSLHonorCipherOrder on

The recommended cipher suite for backwards compatibility (IE6/WinXP):

SSLCipherSuite EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4
SSLHonorCipherOrder on

 

And here’s the same configuration for Nginx:

ssl_ciphers 'EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH';
ssl_prefer_server_ciphers on;

The recommended cipher suite for backwards compatibility (IE6/WinXP):

ssl_ciphers "EECDH+AESGCM:EDH+AESGCM:AES256+EECDH:AES256+EDH:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256:ECDHE-RSA-AES256-SHA:ECDHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES256-GCM-SHA384:AES128-GCM-SHA256:AES256-SHA256:AES128-SHA256:AES256-SHA:AES128-SHA:DES-CBC3-SHA:HIGH:!aNULL:!eNULL:!EXPORT:!DES:!MD5:!PSK:!RC4";
ssl_prefer_server_ciphers on;

If your version of OpenSSL is old, unavailable ciphers will be discarded automatically. Always use the full ciphersuite above and let OpenSSL pick the ones it supports.

The ordering of a ciphersuite is very important because it decides which algorithms are going to be selected in priority. The recommendation above prioritizes algorithms that provide perfect forward secrecy.

 

Prioritization logic

ECDHE+AESGCM ciphers are selected first. These are TLS 1.2 ciphers and not widely supported at the moment. No known attack currently target these ciphers.
PFS ciphersuites are preferred, with ECDHE first, then DHE.
AES 128 is preferred to AES 256.  At the moment, AES128 is preferred, because it provides good security, is really fast, and seems to be more resistant to timing attacks.
In the backward compatible ciphersuite, AES is preferred to 3DES. BEAST attacks on AES are mitigated in TLS 1.1 and above, and difficult to achieve in TLS 1.0. In the non-backward compatible ciphersuite, 3DES is not present.
RC4 is removed entirely. 3DES is used for backward compatibility

 

Protocol Support: SSL or no SSL

To prevent downgrade attacks and poodle attack, we will also disable old SSL protocols

For Apache:

SSLProtocol all -SSLv2 -SSLv3

For Nginx:

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

This disables all versions of SSL, enabling only TLS 1.0 and up. All versions of Chrome and Firefox support at least TLS 1.0.

How to Disable SSLv3 for Apache,Nginx, Litespeed, cPanel

The POODLE bug is a new bug discovered by Google in the SSLv3 protocol. The fix is easy, disable support for SSLv3.

See the google security blog for more info on the bug: http://googleonlinesecurity.blogspot.nl/2014/10/this-poodle-bites-exploiting-ssl-30.html.

 

Fix POODLE

To fix the bug, disable SSLv3 and use a secure cipherlist. SSL v2 is also insecure, so we need to disable it too.

So edit the Apache config file and add following

SSLProtocol All -SSLv2 -SSLv3

All is a shortcut for +SSLv2 +SSLv3 +TLSv1 or – when using OpenSSL 1.0.1 and later – +SSLv2 +SSLv3 +TLSv1 +TLSv1.1 +TLSv1.2, respectively. The above line enables everything except SSLv2 and SSLv3

And then restart the Apache service

service httpd restart

 

cPanel/WHM

If you have a cPanel server, you should not edit Apache configurations directly, instead you can do this from WHM.

 

Apache-Configuration-WHM

 

1. Visit your server’s WHM Panel ( https://<yourserversip>:2087 )
2. Navigate to the Apache Configuration Panel of WHM.
3. Scroll down to the ‘Include Editor’ Section of the Apache Configuration.
4. Click ‘Pre Main Include’, which will jump to the corresponding section. Via the drop-down selector, choose ‘All Versions’.
5. An empty dialogue box will appear allowing you to input the needed configuration updates. In this box, copy and paste the following:

SSLProtocol All -SSLv2 -SSLv3
SSLHonorCipherOrder On

 

For Nginx

If you’re running an NGINX web server that currently uses SSLv3, you need to edit the NGINX configuration (nginx.conf). You will need to add the following line to your server directive:

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

Then restart the nginx service

service nginx restart

For LiteSpeed:

Update to LiteSpeed version 4.2.18.

For more information about Litespeed & POODLE: http://www.litespeedtech.com/support/forum/threads/lsws-4-2-18-released-%E2%80%94-addresses-poodle-sslv3-vulnerability.9948/

Note about Mail Servers:

The POODLE attack requires the client to retry connecting several times in order to downgrade to SSLv3, and typically only browsers will do this. Mail Clients are not as susceptible to POODLE. However, users who want better security should switch to Dovecot until we upgrade Courier to a newer version.

For cpsrvd:

1. Go to WHM => Service Configuration => cPanel Web Services Configuration
2. Make sure that the “TLS/SSL Protocols” field contains “SSLv23:!SSLv2:!SSLv3”.
3. Select the “Save” button at the bottom.

For cpdavd:

1. Go to WHM => Service Configuration => cPanel Web Disk Configuration
2. Make sure that the “TLS/SSL Protocols” field contains “SSLv23:!SSLv2:!SSLv3”.
3. Select the “Save” button at the bottom.

For Dovecot:

1. Go to WHM => Service Configuration => Mailserver Configuration.
2. SSL Protocols should contain “!SSLv2 !SSLv3”. If it does not, replace the text in this field.
3. Go to the bottom of the page, and select the Save button to restart the service.

For Courier:

Courier has released a new version to mitigate this as of 10/22, until we have an opportunity to review, test, and publish the new version of Courier please switch to Dovecot for enhanced security.

For Exim:

1. Go to Home » Service Configuration » Exim Configuration Manager
2. Under Advanced Editor, look for ‘openssl_options’.
3. Make sure the field contains “+no_sslv2 +no_sslv3”.
4.Go to the bottom of the page, and select the Save button to restart the service.

 

For Lighttpd:

Lighttpd releases before 1.4.28 allow you to disable SSLv2 only.

If you are running at least 1.4.29, put the following lines in your configuration file:

ssl.use-sslv2 = "disable"
ssl.use-sslv3 = "disable"

How to verify the Poodle is disabled

You can use a website like http://poodlebleed.com/ for a web based check.

 

Manual check

To make sure services on your server are not accepting SSLv3 connections, you can run the openssl client on your server against the SSL ports. This command is run as follows:

openssl s_client -connect linuxwebhostingsupport.in:443 -ssl3

If it fails (which is what you want), you should see something like this at the top of the output:

3078821612:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1257:SSL alert number 40
3078821612:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:596:

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