Episode 132

Show Notes

Overview

Extended Security Maintenance gets an extension, Linux disk encryption and authentication goes under the microscope and we cover security updates for libgcrypt, the Linux kernel, Python, and more.

This week in Ubuntu Security Updates

20 unique CVEs addressed

[USN-5078-2] Squashfs-Tools vulnerabilities [01:02]

• 2 CVEs addressed in Xenial ESM (16.04 ESM)
  • CVE-2021-41072
  • CVE-2021-40153
• Episode 131

[USN-5080-1, USN-5080-2] Libgcrypt vulnerabilities [01:43]

• 2 CVEs addressed in Xenial ESM (16.04 ESM), Bionic (18.04 LTS), Focal (20.04 LTS), Hirsute (21.04)
  • CVE-2021-40528
  • CVE-2021-33560
• Side-channel attacks against the various ElGamal implementations in OpenPGP - https://eprint.iacr.org/2021/923 - researchers from IBM Research Europe
  • Patent free public key encryption scheme - popular in OpenPGP - 1 in 6 registered OpenPGP keys have an ElGamal subkey
• Various implementations of ElGamal are used in different OpenPGP implementations - Go stdlib, Crypto++ and gcrypt
• libgcrypt has previously had other side-channel vulns found and was used in the development of FLUSH+RELOAD attack against GnuPG
• This attack exploits the different configurations used in the various implementations to use timing differences to be able to recover plaintext
• Fixed to remove support for smaller key lengths and add exponent blinding (combining the exponent with randomness to avoid it being inferred by timing analysis)

[USN-5071-2] Linux kernel (HWE) vulnerabilities [04:11]

• 5 CVEs addressed in Bionic (18.04 LTS)
  • CVE-2021-3612
  • CVE-2021-22543
  • CVE-2020-36311
  • CVE-2021-3653
  • CVE-2021-3656
• AMD nested virtualisation vulns (Episode 130, Episode 131)
• 2 other KVM vulns - UAF
• OOB write in joystick subsystem via a malicious ioctl()
  • requires a joystick device to be present
  • snaps joystick interface is not auto-connected by default

[USN-5071-3] Linux kernel (Raspberry Pi) vulnerabilities

• 2 CVEs addressed in Bionic (18.04 LTS), Focal (20.04 LTS)
  • CVE-2021-3612
  • CVE-2021-22543

[USN-5082-1] Linux kernel (OEM) vulnerabilities

• 3 CVEs addressed in Focal (20.04 LTS)
  • CVE-2021-3609
  • CVE-2021-3653
  • CVE-2021-3656
• CAN BCM UAF (Episode 121), AMD nested virtualisation

[USN-5073-2] Linux kernel (GCP) vulnerabilities

• 5 CVEs addressed in Xenial ESM (16.04 ESM), Bionic (18.04 LTS)
  • CVE-2021-38160
  • CVE-2021-3612
  • CVE-2021-34693
  • CVE-2021-3653
  • CVE-2021-3656

[USN-5073-3] Linux kernel (Raspberry Pi) vulnerabilities

• 3 CVEs addressed in Bionic (18.04 LTS)
  • CVE-2021-38160
  • CVE-2021-3612
  • CVE-2021-34693

[USN-5079-3] curl vulnerabilities [06:34]

• 3 CVEs addressed in Bionic (18.04 LTS)
  • CVE-2021-22947
  • CVE-2021-22946
  • CVE-2021-22945
• Episode 131

[USN-5081-1] Qt vulnerabilities [06:49]

• 2 CVEs addressed in Bionic (18.04 LTS)
  • CVE-2021-38593
  • CVE-2020-17507
• 2 issues in graphics / image handling
  • crafted XBM trigger OOB read -> crash
  • OOB write when rendering SVG or other crafted vector content

[USN-5083-1] Python vulnerabilities [07:22]

• 2 CVEs addressed in Trusty ESM (14.04 ESM), Xenial ESM (16.04 ESM)
  • CVE-2021-3737
  • CVE-2021-3733
• ReDOS - a malicious HTTP server which would send a crafted response for BasicAuth which would cause high CPU usage in trying to match the header value via a regex - fixed to use a simpler regex
• Malicious server could cause a client to hang even if the client had set a timeout - server sends a ‘100 Continue’ response and the client would sit there waiting to receive more input which would never arrive (since server is malicious)

[USN-5084-1] LibTIFF vulnerability [08:32]

• 1 CVEs addressed in Focal (20.04 LTS)
  • CVE-2020-19143
• Buffer overflow via crafted TIFF file

[USN-5079-4] curl regression [08:42]

• 2 CVEs addressed in Trusty ESM (14.04 ESM), Xenial ESM (16.04 ESM)
  • CVE-2021-22947
  • CVE-2021-22946
• Mistake in backporting patch would cause STARTTLS to fail when used for SMTP only - thanks for tuaris for metioning this on https://ubuntuforums.org/showthread.php?t=2467177 but next time please file a LP bug directly as you will get our attention much faster (and more reliably)

Goings on in Ubuntu Security Community

Authenticated boot and disk encryption on Linux [09:28]

• http://0pointer.net/blog/authenticated-boot-and-disk-encryption-on-linux.html
• systemd focused review of existing FDE in general purpose Linux distros with pointers to proposed mechanisms to implement authenticated FDE etc
  • Laments lack of authenticated initrd, use of TPMs etc
  • Proposal is quite different than traditional distros - immutable, authenticated /usr, encrypted, authenticated /etc, /var and per-user /home/user encryption using their own login password
• UC20 already does TPM backed FDE with authentication

Ubuntu 14.04 and 16.04 ESM extended [14:16]

• https://ubuntu.com/blog/ubuntu-14-04-and-16-04-lifecycle-extended-to-ten-years
• Total of 10 years of support (5 LTS, 5 ESM)

• Use extra time to plan upgrades

Hiring [15:48]

Linux Cryptography and Security Engineer

• https://canonical.com/careers/2612092/linux-cryptography-and-security-engineer-remote

Security Engineer - Ubuntu

• https://canonical.com/careers/2925180/security-engineer-ubuntu-remote

Security Product Manager

• https://canonical.com/careers/2278145/security-product-manager-remote

Get in contact

• security@ubuntu.com
• #ubuntu-security on the Libera.Chat IRC network
• ubuntu-hardened mailing list
• Security section on discourse.ubuntu.com
• @ubuntu_sec on twitter