[Bug 1832370] Re: Unable to configure or disable TLS 1.3 via openssl.cnf

[Dimitri John Ledkov]

** Patch added: "cap-to-tls1.2.patch"
   https://bugs.launchpad.net/ubuntu/bionic/+source/openssl/+bug/1832370/+attachment/5270755/+files/cap-to-tls1.2.patch

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Title:
  Unable to configure or disable TLS 1.3 via openssl.cnf

Status in openssl package in Ubuntu:
  Incomplete
Status in openssl source package in Bionic:
  Incomplete
Status in openssl source package in Cosmic:
  Incomplete
Status in openssl source package in Disco:
  Incomplete
Status in openssl source package in Eoan:
  Incomplete

Bug description:
  [Description]

  Since OpenSSL 1.1.1 was backported to Bionic, some (all?) applications
  gained access to TLS 1.3 by default. The applications that were not
  rebuilt against OpenSSL 1.1.1 can't tune the TLS 1.3 settings
  (protocol, ciphersuites selection, ciphersuites order) like it's
  possible with 1.2 and below. As such, one should turn to configuring
  /etc/ssl/openssl.cnf to alter TLS 1.3 settings.

  Here is how I'd expect to be able to turn off TLS 1.3:

  # diff -Naur /etc/ssl/openssl.cnf{.orig,}
  --- /etc/ssl/openssl.cnf.orig	2019-06-11 10:33:02.330143086 -0400
  +++ /etc/ssl/openssl.cnf	2019-06-11 11:15:23.805113804 -0400
  @@ -12,6 +12,16 @@
   HOME			= .
   RANDFILE		= $ENV::HOME/.rnd
   
  +ssl_conf = ssl_sect
  +
  +[ssl_sect]
  +
  +system_default = system_default_sect
  +
  +[system_default_sect]
  +
  +MaxProtocol = TLSv1.2
  +
   # Extra OBJECT IDENTIFIER info:
   #oid_file		= $ENV::HOME/.oid
   oid_section		= new_oids

  This doesn't work as 'openssl s_client -connect
  rproxy.sdeziel.info:443' negotiates TLS 1.3 with
  TLS_AES_256_GCM_SHA384.

  
  Similarly, trying to change the 'Ciphers' or the 'Ciphersuites' list with:

  # diff -Naur /etc/ssl/openssl.cnf{.orig,}
  --- /etc/ssl/openssl.cnf.orig	2019-06-11 10:33:02.330143086 -0400
  +++ /etc/ssl/openssl.cnf	2019-06-11 11:37:23.362889367 -0400
  @@ -12,6 +12,17 @@
   HOME			= .
   RANDFILE		= $ENV::HOME/.rnd
   
  +ssl_conf = ssl_sect
  +
  +[ssl_sect]
  +
  +system_default = system_default_sect
  +
  +[system_default_sect]
  +
  +Ciphers = TLS_AES_128_GCM_SHA256
  +Ciphersuites = TLS_AES_128_GCM_SHA256
  +
   # Extra OBJECT IDENTIFIER info:
   #oid_file		= $ENV::HOME/.oid
   oid_section		= new_oids

  Doesn't work as s_client keeps negotiating TLS 1.3 with
  TLS_AES_256_GCM_SHA384 (!= 128)

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: openssl 1.1.1-1ubuntu2.1~18.04.1
  ProcVersionSignature: Ubuntu 4.15.0-51.55-generic 4.15.18
  Uname: Linux 4.15.0-51-generic x86_64
  NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
  ApportVersion: 2.20.9-0ubuntu7.6
  Architecture: amd64
  CurrentDesktop: ubuntu:GNOME
  Date: Tue Jun 11 11:22:47 2019
  InstallationDate: Installed on 2018-07-15 (331 days ago)
  InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180714)
  ProcEnviron:
   LANG=en_CA.UTF-8
   TERM=xterm-256color
   SHELL=/bin/bash
   XDG_RUNTIME_DIR=<set>
   PATH=(custom, no user)
  SourcePackage: openssl
  UpgradeStatus: No upgrade log present (probably fresh install)

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