Contributing to Linux Kernel security by pperego

Description

A couple of weeks ago, I found this blog post by Gustavo Silva, a Linux Kernel contributor.

I always strived to start again into hacking the Linux Kernel, so I asked Coverity scan dashboard access and I want to contribute to Linux Kernel by fixing some minor issues.

I want also to create a Linux Kernel fuzzing lab using qemu and syzkaller

Goals

1. Fix at least 2 security bugs
2. Create the fuzzing lab and having it running

The story so far

• Day 1: setting up a virtual machine for kernel development using Tumbleweed. Reading a lot of documentation, taking confidence with Coverity dashboard and with procedures to submit a kernel patch
• Day 2: I read really a lot of documentation and I triaged some findings on Coverity SAST dashboard. I have to confirm that SAST tool are great false positives generator, even for low hanging fruits.
• Day 3: Working on trivial changes after I read this blog post: https://www.toblux.com/posts/2024/02/linux-kernel-patches.html. I have to take confidence with the patch preparation and submit process yet.
  • First trivial patch sent: using strtruefalse() macro instead of hard-coded strings in a staging driver for a lcd display
  • Fix for a dereference before null check issue discovered by Coverity (CID 1601566) https://scan7.scan.coverity.com/#/project-view/52110/11354?selectedIssue=1601566
• Day 4: Triaging more issues found by Coverity.
  • The patch for CID 1601566 was refused. The check against the NULL pointer was pointless so I prepared a version 2 of the patch removing the check.
  • Fixed another dereference before NULL check in iwlmvmparsewowlaninfo_notif() routine (CID 1601547). This one was already submitted by another kernel hacker :(
• Day 5: Wrapping up. I had to do some minor rework on patch for CID 1601566. I found a stalker bothering me in private emails and people I interacted with me, advised he is a well known bothering person. Markus Elfring for the record.

• Wrapping up: being back doing kernel hacking is amazing and I don't want to stop it. My battery pack is completely drained but changing the scope gave me a great twist and I really want to feel this energy not doing a single task for months.

  I failed in setting up a fuzzing lab but I was too optimistic for the patch submission process.

The patches

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OIDC Loginproxy by toe

Description

Reverse proxies can be a useful option to separate authentication logic from application logic. SUSE and openSUSE use "loginproxies" as an authentication layer in front of several services.

Currently, loginproxies exist which support LDAP authentication or SAML authentication.

Goals

The goal of this Hack Week project is, to create another loginproxy which supports OpenID Connect authentication which can then act as a drop-in replacement for the existing LDAP or SAML loginproxies.

Testing is intended to focus on the integration with OIDC IDPs from Okta, KanIDM and Authentik.

Resources

• #122254: Migrate away from login proxies to SSO

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Kanidm: A safe and modern IDM system by firstyear

Kanidm is an IDM system written in Rust for modern systems authentication. The github repo has a detailed "getting started" on the readme.

Kanidm Github

In addition Kanidm has spawn a number of adjacent projects in the Rust ecosystem such as LDAP, Kerberos, Webauthn, and cryptography libraries.

In this hack week, we'll be working on Quokca, a certificate authority that supports PKCS11/TPM storage of keys, issuance of PIV certificates, and ACME without the feature gatekeeping implemented by other CA's like smallstep.

For anyone who wants to participate in Kanidm, we have documentation and developer guides which can help.

I'm happy to help and share more, so please get in touch!

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VulnHeap by r1chard-lyu

Description

The VulnHeap project is dedicated to the in-depth analysis and exploitation of vulnerabilities within heap memory management. It focuses on understanding the intricate workflow of heap allocation, chunk structures, and bin management, which are essential to identifying and mitigating security risks.

Goals

• Familiarize with heap
  • Heap workflow
  • Chunk and bin structure
  • Vulnerabilities
• Vulnerability
  • Use after free (UAF)
  • Heap overflow
  • Double free
• Use Docker to create a vulnerable environment and apply techniques to exploit it

Resources

• https://heap-exploitation.dhavalkapil.com/divingintoglibc_heap
• https://raw.githubusercontent.com/cloudburst/libheap/master/heap.png
• https://github.com/shellphish/how2heap?tab=readme-ov-file

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Model checking the BPF verifier by shunghsiyu

Project Description

BPF verifier plays a crucial role in securing the system (though less so now that unprivileged BPF is disabled by default in both upstream and SLES), and bugs in the verifier has lead to privilege escalation vulnerabilities in the past (e.g. CVE-2021-3490).

One way to check whether the verifer has bugs to use model checking (a formal verification technique), in other words, build a abstract model of how the verifier operates, and then see if certain condition can occur (e.g. incorrect calculation during value tracking of registers) by giving both the model and condition to a solver.

For the solver I will be using the Z3 SMT solver to do the checking since it provide a Python binding that's relatively easy to use.

Goal for this Hackweek

Learn how to use the Z3 Python binding (i.e. Z3Py) to build a model of (part of) the BPF verifier, probably the part that's related to value tracking using tristate numbers (aka tnum), and then check that the algorithm work as intended.

Resources

• Formal Methods for the Informal Engineer: Tutorial #1 - The Z3 Theorem Prover and its accompanying notebook is a great introduction into Z3
  • Has a section specifically on model checking
• Software Verification and Analysis Using Z3 a great example of using Z3 for model checking
• Sound, Precise, and Fast Abstract Interpretation with Tristate Numbers - existing work that use formal verification to prove that the multiplication helper used for value tracking work as intended
• [PATCH v5 net-next 00/12] bpf: rewrite value tracking in verifier - initial patch set that adds tristate number to the verifier

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