UPDATE 17th Oct – Some browsers like Firefox and IE 6 are reporting issues when SSLv3 is disabled. Fortunately, SSLv3 fix is available from OpenSSL, and major distros would soon be putting it to their repos. SSLv3 disabling can soon be done in a phased manner. Check comments for more info.
On Oct 14th Google published details of an SSL 3.0 vulnerability, which allows an attacker to secure session through a man-in-the-middle attack. Support for SSL 3.0 is available in all popular mail, ftp and web clients, which makes all your clients vulnerable to an exploit based on this bug. Since SSL 3.0 is an 18 year old obsolete technology, we recommend it to be disabled in all Plesk servers.
Read : Top 7 SSL/TLS deployment best practices
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Pro-active Server Management service at Bobcares was notified of this vulnerability on 14th, and all servers that we maintain were secured against this vulnerability by disabling CBC ciphers.
Here is a quick script for you to check if your Plesk server is vulnerable. Execute the following as root. If you get ANY cipher output, your server can be considered vulnerable.
for port in 443 465 993 995; do echo "Scanning $port"; for cipher in $(openssl ciphers -sslv3 'ALL:eNULL' | sed -e 's/:/ /g'); do echo -n | openssl s_client -sslv3 -cipher "$cipher" -connect xxx.xxx.xxx.xxx:$port 2>&1 | grep -i "Cipher is"; done; done
Replace xxx.xxx.xxx.xxx with your server IP.
Not comfortable doing the scan yourself? We can help!
In Plesk, 4 services need to be secured; viz, HTTP, POP3, IMAP, and SMTP. Here is how we disabled SSL 3.0 in our servers:
HTTP – Apache / Nginx
To fix Apache,
Edit /etc/httpd/conf/httpd.conf and add the following among the other SSL entries:
SSLProtocol All -SSLv2 -SSLv3 SSLCipherSuite EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+ SSLHonorCipherOrder on
Reconfigure Apache and restart it.
/usr/local/psa/admin/bin/httpdmng --reconfigure-all /etc/init.d/httpd restart
To fix Nginx,
Go to Nginx configuration, and change the line ssl_protocols to the one below:
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
Additionally, change the ssl_protocols line in the files /usr/local/psa/admin/conf/templates/default/nginxWebmailPartial.php, /usr/local/psa/admin/conf/templates/default/nginxDomainVirtualHost.php and /usr/local/psa/admin/conf/templates/default/nginxVhosts.php to the one below:
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
Reconfigure and restart Nginx.
/usr/local/psa/admin/bin/httpdmng --reconfigure-all /etc/init.d/httpd restart
SMTP – Postfix
Add the following line in /etc/postfix/main.cf
smtpd_tls_mandatory_protocols=!SSLv2,!SSLv3
Restart Postfix.
POP/IMAP – Courier-IMAP / Dovecot
To fix Dovecot,
Edit the line in /etc/dovecot/dovecot.conf as shown below:
ssl_protocols = !SSLv2 !SSLv3
Restart Postfix.
To fix Courier-IMAP,
Edit the cipher text as shown below in the files /etc/courier-imap/pop3d-ssl and /etc/courier-imap/imapd-ssl
TLS_CIPHER_LIST="ALL:!SSLv2:!SSLv3:!ADH:!NULL:!EXPORT:!DES:!LOW:@STRENGTH"
Restart Courier-IMAP.
Not sure if your servers are patched? We can take a quick look, and fix your servers at just $15 / server.
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@Amal earlier reported issues with customers using IE 6 and Firefox unable to connect to web services when SSLv3 is enabled. The good news is that, you may not be required to disable SSLv3 after-all. A patch is released by OpenSSL: https://www.openssl.org/news/secadv_20141015.txt
The updated packages are yet to reach major repos. Just now checked CentOS, and its still showing older versions. I’m sure it will be available later today, and then its only a matter of doing:
In CentOS / Redhat / Cloud Linux / Fedora servers
In Ubuntu / Debian servers
In OpenSuse servers
OpenSSL 1.0.1 should be upgraded to 1.0.1j
OpenSSL 1.0.0 should be upgraded to 1.0.0o
OpenSSL 0.9.8 should be upgraded to 0.9.8zc