Episode 39

Posted on Tuesday, Jul 9, 2019
A look at security updates for Django, Thunderbird, ZNC, Irssi and more, plus news on the CanonicalLtd GitHub account credentials compromise, SKS PGP keyservers under attack and Ubuntu 18.10 Cosmic Cuttlefish reaches EOL.

Show Notes

Overview

A look at security updates for Django, Thunderbird, ZNC, Irssi and more, plus news on the CanonicalLtd GitHub account credentials compromise, SKS PGP keyservers under attack and Ubuntu 18.10 Cosmic Cuttlefish reaches EOL.

This week in Ubuntu Security Updates

7 unique CVEs addressed

[USN-4043-1] Django vulnerabilities

  • 2 CVEs addressed in Xenial, Bionic, Cosmic, Disco
  • If using django via a reverse proxy, which itself would connect to django over HTTPS, if accessing HTTP resources they would not be redirected to HTTPS even if configured to do so on the django server.
  • XSS via the ‘Current URL’ link as this was not validated as a safe URL before display - so possible to inject javascript etc via a URL query payload parameter etc - such that when the user clicks the link it would be executed (RCE bug with user interaction)

[USN-4045-1] Thunderbird vulnerabilities

  • 2 CVEs addressed in Xenial, Bionic, Cosmic, Disco
  • Latest upstream 60.7.2 release
  • Mentioned in the context of Firefox in Episode 37 and Episode 38 (sandbox escape and RCE)
  • By default scripting is disabled in TB so not as high an impact

[USN-4044-1] ZNC vulnerability

  • 1 CVEs addressed in Xenial, Bionic, Cosmic, Disco
  • ZNC provides support for plugin modules
  • These can be loaded by autenticated, non-admin users

i - The name of this is checked in various places to ensure control characters and other means of code execution are blocked, but not on all code-paths using modules

  • Would allow to execute code as the ZNC server via an authenticated user
  • Fixed to validate module name on all code paths which use it

[USN-4038-3, USN-4038-4] bzip2 regression

  • Affecting Precise ESM, Trusty ESM, Xenial, Bionic, Cosmic, Disco
  • Episode 38 mentioned bzip2 update - we also mentioned this breaks decompression of some archives built by lbzip2 etc - this regression fixes that by introducing a new patch proposed by upstream to accept as many selectors as specified by to then discard them later

[USN-4046-1] Irssi vulnerabilities

  • 2 CVEs addressed in Xenial, Bionic, Cosmic, Disco
  • 2 different UAF’s due to mismanagement of data structures:
    • One on SASL code-paths - so only affected if using SASL authentication - would reuse provided username and password fields after they had been freed
    • Another in code to handle netsplits (used to handle when servers get disconnected from the wider network)
      • This was due to an incomplete fix for previous CVE-2017-7191

Goings on in Ubuntu Security Community

Ubuntu 18.10 (Cosmic Cuttlefish) reaches End of Life on July 18 2019

CanonicalLtd GitHub organisation account compromise

  • A single account which was part of the CanonicalLtd GitHub organisation was compromised 6th July
  • Used to create proof-of-concept repositories and issues to demonstrate the hack was possible
  • Investigation is still on-going but at this stage it only appears to be these actions, not malicious but attention seeking in nature
    • No code has been altered or PII accessed (nor is any PII stored there)
  • Account has been removed from the CanonicaLtd organisation, investigation is still on-going, we will release more details as they become available
  • https://twitter.com/ubuntu%5Fsec/status/1147675201632473088

SKS keyserver certificate spamming

  • https://gist.github.com/rjhansen/67ab921ffb4084c865b3618d6955275f
  • WoT aspect of PGP allows users to sign one-anothers public keys (certificates) and upload these signatures to the keyservers
  • SKS keyservers were designed to never delete anything and instead to append
  • So when downloading a key (certificate) you get it plus all the signatures
  • SKS supports up to 150k sigs - GnuPG is logarithmic in order of signatures
  • So can DoS local GnuPG once have downloaded someones key (cert)
  • Re Ubuntu:
    • We use GPG for signing the hashes of packages in the repo
    • This public key is distributed directly inside Ubuntu on install media and in the archive and does not depend on the SKS keyserver network
    • Keys for PPAs are fetched from Launchpad, not SKS as well in general
    • So only exposure for Ubuntu users is if manually fetching keys from SKS keyservers or if using Enigmail in ThunderBird or other software which automatically fetches certs from SKS
  • Mitigation

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