Episode 79

Show Notes

Overview

This week Joe discusses Intel’s CET announcement with John Johansen, plus Alex details recent security fixes including SQLite, fwupd, NSS, DBus and more.

This week in Ubuntu Security Updates

24 unique CVEs addressed

[USN-4394-1] SQLite vulnerabilities [00:56]

• 9 CVEs addressed in Xenial (16.04 LTS), Bionic (18.04 LTS), Eoan (19.10), Focal (20.04 LTS)
  • CVE-2020-13632
  • CVE-2020-13631
  • CVE-2020-13630
  • CVE-2020-13435
  • CVE-2020-13434
  • CVE-2020-11655
  • CVE-2019-19645
  • CVE-2019-19603
  • CVE-2018-8740
• NULL ptr deref via crafted query, UAF, OOB read, integer overflow when printing high precision floating point numbers, various minor issues when handling crafted databases

[USN-4385-2] Intel Microcode regression [01:43]

• 3 CVEs addressed in Trusty ESM (14.04 ESM), Xenial (16.04 LTS), Bionic (18.04 LTS), Eoan (19.10), Focal (20.04 LTS)
  • CVE-2020-0549
  • CVE-2020-0548
  • CVE-2020-0543
• Episode 78 - SRBDS etc - microcode is specific to processors, and is identified by the triplet of CPU Family, Model and Stepping - this is listed in /proc/cpuinfo - mine say is 6, 142, 10 - in hex - 06-8E-0A - would cause a specific Skylake processor type to fail to boot (06-4e-03) - we reverted this back to the previous release version from November 2019

[USN-4395-1] fwupd vulnerability [03:39]

• 1 CVEs addressed in Xenial (16.04 LTS), Bionic (18.04 LTS), Eoan (19.10), Focal (20.04 LTS)
  • CVE-2020-10759
• A crafted firmware update file could bypass signature verification - in general not an issue since would need to be able to get in the middle of firmware updates (which come from LVFS via HTTPS) - so either would need to compromise LVFS directly or the HTTPS connection to it.
  • Dangling S3 bucket… :/
• https://github.com/justinsteven/advisories/blob/master/2020_fwupd_dangling_s3_bucket_and_CVE-2020-10759_signature_verification_bypass.md

[USN-4315-2] Apport vulnerabilities [06:11]

• 2 CVEs addressed in Trusty ESM (14.04 ESM)
  • CVE-2020-8833
  • CVE-2020-8831
• Episode 70

[USN-4396-1] libexif vulnerabilities [06:24]

• 6 CVEs addressed in Precise ESM (12.04 ESM), Trusty ESM (14.04 ESM), Xenial (16.04 LTS), Bionic (18.04 LTS), Eoan (19.10), Focal (20.04 LTS)
  • CVE-2020-13114
  • CVE-2020-13113
  • CVE-2020-13112
  • CVE-2020-0198
  • CVE-2020-0182
  • CVE-2020-0093
• UAF due to uninitialised memory, various buffer over-reads, integer overflow, etc

[USN-4397-1] NSS vulnerabilities [07:24]

• 2 CVEs addressed in Xenial (16.04 LTS), Bionic (18.04 LTS), Eoan (19.10), Focal (20.04 LTS)
  • CVE-2020-12399
  • CVE-2019-17023
• Possible timing side-channel attack during DSA key generation - due to the difference in time of various operations (dependent on the contents of the private key) - the key value could be inferred by an attacker

[USN-4398-1, USN-4398-2] DBus vulnerability [08:01]

• 1 CVEs addressed in Precise ESM (12.04 ESM), Trusty ESM (14.04 ESM), Xenial (16.04 LTS), Bionic (18.04 LTS), Eoan (19.10), Focal (20.04 LTS)
  • CVE-2020-12049
• DBus can be used to send file-descriptors - client sends to server via the dbus daemon - daemon will validate that messages only contain a certain number of file-descriptors - if too may, will reject BUT fail to close those file-descriptors - eventually would accumulate too many open files itself and so the daemon would not be able to accept new connections -> DoS from a local unprivileged user

Goings on in Ubuntu Security Community

Joe discusses Intel CET with John Johansen (aka JJ) [09:28]

• Return Oriented Programming (ROP) https://en.wikipedia.org/wiki/Return-oriented_programming

• Sigreturn Oriented Programming (SROP) (https://en.wikipedia.org/wiki/Sigreturn-oriented_programming

• Jump/Call Oriented Programming (JOP) https://www.csc2.ncsu.edu/faculty/xjiang4/pubs/ASIACCS11.pdf

• Control-flow Enforcement technology (CET)

  • https://www.linuxplumbersconf.org/event/2/contributions/147/attachments/72/83/CET-LPC-2018.pdf
  • https://software.intel.com/sites/default/files/managed/4d/2a/control-flow-enforcement-technology-preview.pdf

• CFI in software

  • https://www.cse.usf.edu/~ligatti/papers/cficcs.pdf

• CET on Linux

  • Kernel

    • https://lwn.net/Articles/758245/

  • gcc

    • https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=8d286dd118a5bd16f7ae0fb9dfcdcfd020bea803
    • https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=d17cdc17c90ce77cb90c569322c1f241d3530cec
    • https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=d21486483579c2205fcabf1308b155000af86fe1
    • https://gcc.gnu.org/git/?p=gcc.git&a=search&h=HEAD&st=commit&s=CET

  • glibc

    • https://sourceware.org/legacy-ml/libc-alpha/2018-08/msg00003.html

• LLVM/Clang

  • not just CET, clang has it own CFI not dependent on CET but will support CET
  • https://clang.llvm.org/docs/ControlFlowIntegrity.html
  • https://clang.llvm.org/docs/ShadowCallStack.html

• CET on windows

  • https://windows-internals.com/cet-on-windows/

• Pre CET software based CFI on windows

  • https://docs.microsoft.com/en-us/windows/win32/secbp/control-flow-guard

• Papers/talks on attacking CET/CFI

  • https://i.blackhat.com/asia-19/Thu-March-28/bh-asia-Sun-How-to-Survive-the-Hardware-Assisted-Control-Flow-Integrity-Enforcement.pdf
  • https://windows-internals.com/cet-on-windows/

• Smashing the stack for fun and profit

  • https://www.eecs.umich.edu/courses/eecs588/static/stack_smashing.pdf

• StackClash

  • https://blog.qualys.com/securitylabs/2017/06/19/the-stack-clash

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