How to disable SSLv3: Difference between revisions

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Restart the proxy servers with: "zmproxyctl stop ; zmproxyctl start"
Restart the proxy servers with: "zmproxyctl stop ; zmproxyctl start"
=== Jetty (mailboxd) ===
=== Verifying ===
How to verify if the changes have been done? We should run the following command (as zimbra) for every port using SSL:
openssl s_client -connect `zmhostname`:<port> -ssl3 |grep failure
Example, for port 443:
openssl s_client -connect `zmhostname`:443 -ssl3
If it shows a failure, it's good and we don't support SSLv3:
140532971947680:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1275:SSL alert number 40
140532971947680:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:598:
If you are seeing:
New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-SHA
Server public key is 2048 bit
Secure Renegotiation IS supported
SSLv3 is still enabled and you need to verify the changes.
Here is a command to verify common ports when using the Zimbra proxy (run this at the proxy):
for p in 993 995 443 ; do echo Port $p ; timeout 3 openssl s_client -connect `zmhostname`:$p -ssl3 |grep failure ; done
If you are proxying adminUI, please add port 9071, 7071 or the port you have configured. If you are proxying SSO requests, please add port 3443.
List of ports:
443 - HTTPS
993 - IMAP-SSL
995 - POP3-SSL
9071 - AdminUI SSL
For Postfix, run the following command at the MTA for the SMTP-SSL port (465):
timeout 3 openssl s_client -connect `zmhostname`:465 -ssl3

Revision as of 18:03, 15 October 2014

Admin Article

Article Information

This article applies to the following ZCS versions.

ZCS 8.0 Article ZCS 8.0 ZCS 8.5 Article ZCS 8.5

How to disable SSLv3

Due to the recent discovery of a new SSL vulnerability (CVE-2014-3566: Poodle SSLv3), this protocol has been considered unsafe. This is a protocol flaw and Zimbra might include patches or configuration changes in future releases. Please check existing Bug https://bugzilla.zimbra.com/show_bug.cgi?id=95976.

As a workaround, this guide will help you on how to disable SSLv3 with Zimbra. This has been tested on both ZCS 8.0.8 and 8.5.0 releases.

Postfix

8.5.x

zmprov mcf zimbraMtaSmtpdTlsProtocols '\!SSLv3'

8.0.x

postconf -e smtpd_tls_protocols=\!SSLv3

Run "zmmtactl stop ; zmmtactl start" to force the changes or wait for mailboxd to rewrite Postfix config from LDAP after 2 minutes.

If you are already disabling ciphers by following http://wiki.zimbra.com/wiki/Postfix_PCI_Compliance_in_ZCS, please also include SSLv3:

8.5.x

zmprov mcf zimbraMtaSmtpdTlsCiphers high zmprov mcf zimbraMtaSmtpdTlsProtocols '\!SSLv3,\!SSLv2,TLSv1,TLSv2' zmprov mcf zimbraMtaSmtpdTlsMandatoryCiphers high zmprov mcf zimbraMtaSmtpdTlsExcludeCiphers 'aNULL,MD5,DES'

8.0.x

zmlocalconfig -e smtpd_tls_ciphers=high postconf -e smtpd_tls_protocols=\!SSLv3,\!SSLv2,TLSv1,TLSv2 zmlocalconfig -e smtpd_tls_mandatory_ciphers=high postconf -e smtpd_tls_exclude_ciphers=aNULL,MD5,DES

Run "zmmtactl stop ; zmmtactl start" to apply the changes.

Note that smtpd_tls_protocols and smtpd_tls_exclude_ciphers will need to be set after every upgrade as there is no way to preserve them in ZCS 8.0 and previous.

Nginx

8.5.x

For https and Admin UI:

Please edit /opt/zimbra/conf/nginx/templates/nginx.conf.web.https.default.template

and include the following line under the servers { } configuration:

ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

Example:

  1. HTTPS Proxy Default Configuration

server {

   ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
   ${core.ipboth.enabled}listen                  [::]:${web.https.port} default;

[...]

Apply the same change at /opt/zimbra/conf/nginx/templates/nginx.conf.web.admin.default.template

If you are using SSO with Client certificates, also edit /opt/zimbra/conf/nginx/templates/nginx.conf.web.sso.default.template.

For imaps and pop3s:

Please edit /opt/zimbra/conf/nginx/templates/nginx.conf.mail.pop3s.default.template

Example:

  1. POP3S proxy default configuration

server {

   ssl_protocols TLSv1 TLSv1.1 TLSv1.2;

[...]

Apply the same change at /conf/nginx/templates/nginx.conf.mail.imaps.default.template

Restart the proxy servers with: "zmproxyctl stop ; zmproxyctl start"

Jetty (mailboxd)

Verifying

How to verify if the changes have been done? We should run the following command (as zimbra) for every port using SSL:

openssl s_client -connect `zmhostname`:<port> -ssl3 |grep failure

Example, for port 443: openssl s_client -connect `zmhostname`:443 -ssl3

If it shows a failure, it's good and we don't support SSLv3:

140532971947680:error:14094410:SSL routines:SSL3_READ_BYTES:sslv3 alert handshake failure:s3_pkt.c:1275:SSL alert number 40 140532971947680:error:1409E0E5:SSL routines:SSL3_WRITE_BYTES:ssl handshake failure:s3_pkt.c:598:

If you are seeing:

New, TLSv1/SSLv3, Cipher is ECDHE-RSA-AES128-SHA Server public key is 2048 bit Secure Renegotiation IS supported

SSLv3 is still enabled and you need to verify the changes.

Here is a command to verify common ports when using the Zimbra proxy (run this at the proxy):

for p in 993 995 443 ; do echo Port $p ; timeout 3 openssl s_client -connect `zmhostname`:$p -ssl3 |grep failure ; done

If you are proxying adminUI, please add port 9071, 7071 or the port you have configured. If you are proxying SSO requests, please add port 3443.

List of ports: 443 - HTTPS 993 - IMAP-SSL 995 - POP3-SSL 9071 - AdminUI SSL

For Postfix, run the following command at the MTA for the SMTP-SSL port (465):

timeout 3 openssl s_client -connect `zmhostname`:465 -ssl3

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