Just a guess but maybe later entries [like +HIGH:+MEDIUM:+LOW] put it back.  Try switching the order so that !ECDHE and the others you're trying to exclude come after.  Sent from Samsung Mobile -------- Original message -------- From: Ilyas Keskin &lt;ilyask92(a)gmx.de&gt; Date: 11/24/2017 10:19 AM (GMT-08:00) To: miconda(a)gmail.com,&quot;Kamailio (SER) - Users Mailing List" &lt;sr-users(a)lists.kamailio.org&gt; Subject: Re: [SR-Users] Cannot disable EC Diffie Hellman cipher suite Hi Daniel, yes I am using the tls.cfg file. I tried your suggestion to add the cipher suite string (notice the !EDCHE which I also added to the httpd ssl.conf) but nothing changed.     [server:default]     method = TLSv1     cipher_list = !DH:!ECDHE:!EDH:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL     verify_certificate = no     require_certificate = no     private_key = /etc/letsencrypt/live/webrtc.ddnss.de/privkey.pem     certificate = /etc/letsencrypt/live/webrtc.ddnss.de/fullchain.pem     #ca_list = ./modules/tls/cacert.pem     #crl = ./modules/tls/crl.pem Also here is a log snippet from tls module section of kamailio initialization. Notice first two lines. Also it seems to me the module actually ignores the local openssl installation and uses its own which has been compiled with the module itself (?). Other than that it seems to be accepting the cipher_list value just fine: Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_mod.c:355]: mod_init(): With ECDH-Support! Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_mod.c:358]: mod_init(): With Diffie Hellman Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_init.c:587]: init_tls_h(): tls: _init_tls_h:  compiled  with  openssl  version "OpenSSL 1.0.1e-fips 11 Feb 2013" (0x1000105f), kerberos support: on, compression: on Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_init.c:595]: init_tls_h(): tls: init_tls_h: installed openssl library version "OpenSSL 1.0.1e-fips 11 Feb 2013" (0x1000105f), kerberos support: on,  zlib compression:                                                         compiler: gcc -I. -I.. -I../include  -fPIC -DOPENSSL_PIC -DZLIB -DOPENSSL_THREADS -D_REENTRANT -DDSO_DLFCN -DHAVE_DLFCN_H -DKRB5_MIT -m64 -DL_ENDIAN -Wall -O2 -g -pipe -Wall -Wp,-D_ Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: WARNING: tls [tls_init.c:649]: init_tls_h(): tls: openssl bug #1491 (crash/mem leaks on low memory) workaround enabled (on low memory tls operations will fail preemptively) with free Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: <core> [cfg/cfg_ctx.c:613]: cfg_set_now(): INFO: cfg_set_now(): tls.low_mem_threshold1 has been changed to 7864320 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: <core> [cfg/cfg_ctx.c:613]: cfg_set_now(): INFO: cfg_set_now(): tls.low_mem_threshold2 has been changed to 3932160 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: WARNING: tm [tm.c:594]: fixup_routes(): WARNING: t_on_branch("MANAGE_BRANCH"): empty/non existing route Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: WARNING: tm [tm.c:594]: fixup_routes(): WARNING: t_on_reply("MANAGE_REPLY"): empty/non existing route Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: WARNING: tm [tm.c:594]: fixup_routes(): WARNING: t_on_failure("MANAGE_FAILURE"): empty/non existing route Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: <core> [udp_server.c:175]: probe_max_receive_buffer(): SO_RCVBUF is initially 212992 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: <core> [udp_server.c:225]: probe_max_receive_buffer(): SO_RCVBUF is finally 425984 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:275]: fill_missing(): TLSs<default>: tls_method=12 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:287]: fill_missing(): TLSs<default>: certificate='/etc/letsencrypt/live/webrtc.ddnss.de/fullchain.pem' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:294]: fill_missing(): TLSs<default>: ca_list='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:301]: fill_missing(): TLSs<default>: crl='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:305]: fill_missing(): TLSs<default>: require_certificate=0 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:312]: fill_missing(): TLSs<default>: cipher_list='!DH:!ECDHE:!EDH:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:319]: fill_missing(): TLSs<default>: private_key='/etc/letsencrypt/live/webrtc.ddnss.de/privkey.pem' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:323]: fill_missing(): TLSs<default>: verify_certificate=0 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:326]: fill_missing(): TLSs<default>: verify_depth=9 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:670]: set_verification(): TLSs<default>: No client certificate required and no checks performed Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:275]: fill_missing(): TLSc<default>: tls_method=12 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:287]: fill_missing(): TLSc<default>: certificate='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:294]: fill_missing(): TLSc<default>: ca_list='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:301]: fill_missing(): TLSc<default>: crl='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:305]: fill_missing(): TLSc<default>: require_certificate=1 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:312]: fill_missing(): TLSc<default>: cipher_list='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:319]: fill_missing(): TLSc<default>: private_key='(null)' Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:323]: fill_missing(): TLSc<default>: verify_certificate=1 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:326]: fill_missing(): TLSc<default>: verify_depth=9 Nov 24 18:56:20 kamailio-sip /usr/sbin/kamailio[2864]: INFO: tls [tls_domain.c:655]: set_verification(): TLSc<default>: Server MUST present valid certificate Would it be possible to compile the tls module with certain openssl config switches (i.e. no-ec no-dh)? Any other ideas? Best regards, Ilyas Keskin Am 24.11.2017 um 15:45 schrieb Daniel-Constantin Mierla: Hello, On 23.11.17 22:42, Ilyas Keskin wrote: Hi there, I have set up a Kamailio 4.2.0 SIP server (centOS 7) for a university project regarding WebRTC comunication. While kamailio handles the signaling path I use the SIP.js demo phone js application (hosted on the same machine as kamaillio) for actual WebRTC stuff. For a deeper understanding and documetation purposes I have been trying to sniff the traffic with wireshark but failed due to the fact that kamailio uses Elliptic Curve Diffie Hellmann cipher suite (see wireshark snippet below) which is not decryptable. Secure Sockets Layer     TLSv1.2 Record Layer: Handshake Protocol: Server Hello         Content Type: Handshake (22)         Version: TLS 1.2 (0x0303)         Length: 89         Handshake Protocol: Server Hello             Handshake Type: Server Hello (2)             Length: 85             Version: TLS 1.2 (0x0303)             Random: b8916e4e0f7c712503a77afcf4c9228598092c166353be50...             Session ID Length: 32             Session ID: b0a31a6699a001b7991645dc61064ca4c4b073eff6913f26...             Cipher Suite: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (0xc02f)             Compression Method: null (0)             Extensions Length: 13             Extension: renegotiation_info (len=1)             Extension: ec_point_formats (len=4) I already tried importing captured SSLKEYLOG pre master secret from chrome and private key file issued by letsencrypt without success. On top of that I set this line     SSLCipherSuite !DH:!ECDH:!EDH:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL in /etc/httpd/conf.d/ssl.conf and compiled openssl with no-ec no-dh (which worked see below). [admin@kamailio-sip ~]$ openssl ciphers SRP-DSS-AES-256-CBC-SHA:SRP-RSA-AES-256-CBC-SHA:SRP-AES-256-CBC-SHA:AES256-GCM-SHA384:AES256-SHA256:AES256-SHA:CAMELLIA256-SHA:PSK-AES256-CBC-SHA:SRP-DSS-AES-128-CBC-SHA:SRP-RSA-AES-128-CBC-SHA:SRP-AES-128-CBC-SHA:AES128-GCM-SHA256:AES128-SHA256:AES128-SHA:SEED-SHA:CAMELLIA128-SHA:IDEA-CBC-SHA:PSK-AES128-CBC-SHA:RC4-SHA:RC4-MD5:PSK-RC4-SHA:SRP-DSS-3DES-EDE-CBC-SHA:SRP-RSA-3DES-EDE-CBC-SHA:SRP-3DES-EDE-CBC-SHA:DES-CBC3-SHA:PSK-3DES-EDE-CBC-SHA [admin@kamailio-sip ~]$ Setting     modparam("tls", "cipher_list", "AESCCM") (or different ciphers) in /etc/kamailio/kamailio.cfg seems to have no effect on the actual negoiated cipher suite. Am I missing something? Any help or pointers into the right direction will be much appreciated. are you also using tls.cfg? If yes, there is an attribute for chiper list in it as well, try and see if works with it. Cheers, Daniel -- Daniel-Constantin Mierla www.twitter.com/miconda -- www.linkedin.com/in/miconda Kamailio Advanced Training - www.asipto.com Kamailio World Conference - May 14-16, 2018 - www.kamailioworld.com