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 DirectAdmin 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 DirectAdmin server is vulnerable. Execute the following as root. If you get ANY cipher output, your server can be considered vulnerable.
for port in 21 443 465 993 995 2223; 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:$port 2>&1 | grep -i "Cipher is"; done; done
Replace xxx.xxx.xxx.xxx with your server IP.
Not comfortable doing the scan yourself? We can help!
In DirectAdmin, 4 services need to be secured; viz, HTTP, POP3, IMAP, SMTP and DirectAdmin Web. Here is how we disabled SSL 3.0 in our servers:
HTTP – Apache / Nginx
To fix Apache,
Edit /etc/httpd/conf/extra/httpd-ssl.conf and add the following among the other SSL entries:
SSLProtocol All -SSLv2 -SSLv3 SSLCipherSuite EECDH+AES128:RSA+AES128:EECDH+AES256:RSA+AES256:EECDH+ SSLHonorCipherOrder on
Reconfigure Apache.
To fix Nginx,
Change the below directive as shown in the files /usr/local/directadmin/data/templates/nginx_ips.conf, /usr/local/directadmin/data/templates/nginx_server_secure.conf, /usr/local/directadmin/data/templates/nginx_server_secure_sub.conf, /etc/nginx/directadmin-ips.conf and /etc/nginx/nginx-vhosts.conf
ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
Reconfigure Nginx.
SMTP – Exim
Add the following line in /etc/exim.conf
openssl_options = +no_sslv3 tls_require_ciphers = ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:-LOW:-SSLv2:-EXP
Restart Exim.
POP/IMAP – Dovecot
Edit the line in /etc/dovecot/dovecot.conf as shown below:
ssl_protocols = !SSLv2 !SSLv3 ssl_cipher_list = ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:-LOW:-SSLv2:-EXP
Restart Dovecot.
FTP – Pure-FTPd / ProFTPd
To fix Pure-FTPd,
Edit the files /etc/init.d/pure-ftpd and /usr/libexec/pureftpd_startscript, and modify the start options as shown below:
OPTIONS="${OPTIONS} -Y 1 -J HIGH:MEDIUM:+TLSv1:!SSLv2:!SSLv3"
To fix ProFTPd,
Edit /etc/proftpd.conf and modify the lines below:
TLSProtocol TLSv1 TLSCipherSuite HIGH:MEDIUM:+TLSv1:!SSLv2:!SSLv3
DirectAdmin Panel
Edit the file /usr/local/directadmin/conf/directadmin.conf, and add the options as below:
ssl_cipher=ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:-LOW:-SSLv2:-SSLv3:-EXP
Not sure if your servers are patched? We can take a quick look, and fix your servers at just $15 / server.
Sign up for Proactive Server Management today, and get your servers automatically secured against zero-day exploits.
@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