For everyone else’s benefit, this was sorted. I’ve found that I needed something set in both vars.xml: <X-PRE-PROCESS cmd="set" data="sip_tls_ciphers=AES256-GCM-SHA384"/> and the sip_profile I wanted to restrict the ciphers for: <param name="tls-ciphers" value="$${sip_tls_ciphers}"/> Thanks From: Michael Meehan <mmeehan@djsequel.com> Date: Friday, June 24, 2022 at 9:09 AM To: freeswitch-users@lists.freeswitch.org <freeswitch-users@lists.freeswitch.org> Subject: Using Specific TLS Ciphers (1.10.7) We’ve been trying to prevent using specific ciphers, mainly Diffie-Hellman. According to the documentation I’ve seen and previous posts in this group, that should be accomplished by using something like this: <X-PRE-PROCESS cmd="set" data="sip_tls_ciphers=TLS_RSA_WITH_AES_128_CBC_SHA256"/> This doesn’t work. This specific cipher is offered in the CLIENT HELLO and shown as also supported from the SERVER HELLO response amongst others, however, we continue to see DH as being agreed upon: tport_tls.c:974 tls_connect() tls_connect(0x7ff738006e70): events CONNECTING tport_tls.c:974 tls_connect() tls_connect(0x7ff738006e70): events NEGOTIATING tport_tls.c:974 tls_connect() tls_connect(0x7ff738006e70): events NEGOTIATING tport_tls.c:617 tls_post_connection_check() tls_post_connection_check(0x7ff738006e70): TLS cipher chosen (name): ECDHE-RSA-AES128-GCM-SHA256 tport_tls.c:619 tls_post_connection_check() tls_post_connection_check(0x7ff738006e70): TLS cipher chosen (version): TLSv1/SSLv3 tport_tls.c:622 tls_post_connection_check() tls_post_connection_check(0x7ff738006e70): TLS cipher chosen (bits/alg_bits): 128/128 tport_tls.c:625 tls_post_connection_check() tls_post_connection_check(0x7ff738006e70): TLS cipher chosen (description): ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH Au=RSA Enc=AESGCM(128) Mac=AEAD Other attempts have been made using the following, which also doesn’t appear to function as expected. <X-PRE-PROCESS cmd="set" data="sip_tls_ciphers=ALL:!ADH:!DH:!ECDH:!LOW:!EXP:!MD5:@STRENGTH"/> Any help is appreciated, thanks. FreeSWITCH Version 1.10.7-release.13~64bit (-release.13 64bit) CENTOS 7 3.10.0-1160.62.1.el7.x86_64