Disable TLSv1.1 on the Proxy
Article ID: 373905
Updated On:
Products
Issue/Introduction
To disable TLSv1.1, use best practices for SSL connections.
Use more secure TLS versions to harden the SSL connection.
By default, SSLv3, TLSv1.0, TLSv1.1, TLSv1.2, and TLSv1.3 are all enabled for SSL proxy traffic. The use of SSLv3, TLSv1.0, or TLS 1.1 is not recommended due to various vulnerabilities in these protocol versions.
Environment
SG/ASG/ISG-Proxy
Resolution
For best security, use the following CPL gestures:
<ssl>
client.connection.negotiated_ssl_version=(SSLV3,TLSv1,TLSv1.1) force_exception(silent_denied)
<ssl>
server.connection.negotiated_ssl_version=(SSLV3,TLSv1,TLSv1.1) force_exception(silent_denied)
Before disabling SSLv3, TLSv1.0, and TLS 1.1, verify that all clients and servers with traffic going through the appliance support TLSv1.2 or later
Use more secure cipher suites to harden the SSL connection.
The appliance uses the first cipher suite offered by a client, even if it is a lower grade. For better security, allow only cipher suites that meet your minimum acceptable level of security. the HTTPS Management Console comes with 22 ciphers enabled. Disable all ciphers that operate in CBC mode and enabling more secure ciphers that operate in GCM, CCM, or stream mode. For example, enable the following list of ciphers:
– tls_aes_256_gcm_sha384
– tls_chacha20_poly1305_sha256
– tls_aes_128_gcm_sha256
– tls_aes_128_ccm_8_sha256
– tls_aes_128_ccm_sha256
– ecdhe-rsa-aes256-gcm-sha384
– ecdhe-rsa-aes128-gcm-sha256
– aes128-gcm-sha256
– aes256-gcm-sha384
– dhe-rsa-aes128-gcm-sha256
– dhe-rsa-aes256-gcm-sha384
In addition, four less secure ciphers are supported (ECDHE-RSA-RC4-SHA, DES-CBC3-SHA, RC4-SHA, RC4-MD5) but not enabled. Do not enable the less secure ciphers.
Use CPL such as the following to harden the list of cipher suites:
<ssl>
client.connection.negotiated_cipher.strength=(low,medium) force_exception(silent_denied)
<ssl>
server.connection.negotiated_cipher.strength=(low,medium) force_exception(silent_denied)
For the Device Profiles where you still see the box for TLS 1.1 checked, under device profile configuration and uncheck the box for TLS 1.1. Please note that with the above best practice implementation, SSLv3, TLSv1.0, and TLS 1.1 will not be applicable for device profile settings.
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