[Bug 1866611] Re: OpenVPN w. SHA1 signed CA broken after upgrade to 1.1.1d-2ubuntu6

[staedtler-przyborski]

As a quick addition for the QVPN app on a Qnap NAS in our network I just
installed a Raspberry 3 with PiVpn (pivpn.io) configured for OpenVPN, as
I'm in doubt Qnap will release an updated QVpn just in Time ...

Works like a charm and installation is super easy. With at least one
connection it seems even faster than QVpn on a more powerful NAS. No
test with multiple connections until now ... but there are more beefy
Rasberry 4 if it shows to slow...

With this additional VPN the transition to Ubuntu 20.04 can now be done
in my company. When its finished i'll switch off QVpn  (and remove the
corresponding portforwarding).

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Title:
  OpenVPN w. SHA1 signed CA broken after upgrade to 1.1.1d-2ubuntu6

Status in openssl package in Ubuntu:
  Confirmed

Bug description:
  After upgrading openssl on my Focal-install this morning (upgrade
  openssl:amd64 1.1.1d-2ubuntu3 1.1.1d-2ubuntu6 per /var/log/dpkg.log),
  my OpenVPN tunnel refuses to connect to our corporate VPN (from
  /var/log/syslog):

  corp-laptop nm-openvpn[4688]: VERIFY ERROR: depth=0, error=CA signature digest algorithm too weak: C=DK, ST=None, L=Copenhagen, O=XX, OU=XX, CN=XX, emailAddress=XX
  corp-laptop nm-openvpn[4688]: OpenSSL: error:1416F086:SSL routines:tls_process_server_certificate:certificate verify failed

  I'm told we're running a SHA1-signed CA, which we're guessing has been
  deprecated somewhere between -2ubuntu3 and -2ubuntu6. The changelog
  for -2ubuntu4 mentions importing some upstream changes, but isn't more
  specific than that:
  https://changelogs.ubuntu.com/changelogs/pool/main/o/openssl/openssl_1.1
  .1d-2ubuntu4/changelog

  As a work-around, the internet suggests two work-arounds (neither of
  which has worked for me):

  1) Adding the following to /etc/defaults/openssl:

      OPTARGS="--tls-cipher DEFAULT:@SECLEVEL=0"

  2) Adding the following to /etc/ssl/openssl.conf:

      CipherString    = :@SECLEVEL=1

  I also tried rolling back the package, but the old version doesn't
  seem to be available:

      $ sudo apt install openssl=1.1.1d-2ubuntu3
      ...
      E: Version '1.1.1d-2ubuntu3' for 'openssl' was not found

  
  I am no SSL-expert and would appreciate any pointers to get around this. (Our network-dept. does not have the bandwidth to roll over our CA on short notice, so I will need some other way to move ahead).

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