Intro

• My name is delet0r
• Working in IT-Security by day
• Working on the Prototype Fund Project
  SiC (Signed Containers) by night

Agenda

1. Packaging as Complexity Reduction
2. An Approach to Trust
3. Sigstore
4. Conclusion

A short and very simplified history tale
of tackling complexity by packaging and
distributing software (aka Supply Chains)

The Software Crisis

The Software Crisis

• Term coined in 1968 at the NATO Software Engineering Conference
• Referenced by Edsger Dijkstra in his Book The Humble Programmer
• Describes the problems arising with the increasing complexity of programs

Tackling Complexity

• Packaging programs is one way to reduce complexity
• Hiding intricacies of a piece of software
  • Build system
  • Transitive dependencies
• Put burden on the developer/distributor

The Escalation Evolution of Packaging

1. Distribution: Package Management
2. Deployment: Containerization
3. Operation: Cloud/Container Orchestration

The Evolution of Packaging

1. Distribution: Package Management
2. Deployment: Containerization
3. OperationCloud/Container: Orchestration

The Evolution of Packaging

1. Distribution: Package Management
2. Deployment: Containerization
3. Operation: Cloud/Container Orchestration

The Evolution of Packaging

1. Distribution: Package Management
2. Deployment: Containerization
3. Operation: Cloud/Container Orchestration

Shortcomings

• Modern iterations of packaging miss important features of good
  package management:
  1. Integrity
  2. Authenticity

Where are we?

• Lower complexity bought with increased complexity somewhere else
• Any package has potential hidden tail of dependencies
• No practical way of ensuring their authenticity or integrity
  (most of the time)
• No conscious entity (like a team maintaining a Distro)we can
  trust that does this for us

Agenda

1. Packaging as Complexity Reduction
2. An approach to Trust
3. Sigstore
4. Conclusion

What is Trust?

• Defining trust, especially in context of IT, is challenging
• Becomes mushy when mixing technology with human interaction
• Trust is the belief in the integrity of a person or a group

Proof is Not Trust

• When setting up a system there are different things can be
  done to ensure its security:
  • Cryptography
  • Formal proofs
• This is not trust but rather logical proofs

Suspension of Disbelief

• In every system there is a point were we can’t technically
  prove properties anymore
• For that we need Suspension of Disbelief … or Trust

Different ways of balancing Trust and Proofs

• a. Content Moderation (Trust first)
• b. Signatures (Proof first)

a. Content Moderation

• Trust first approach
• System were a set of people or an institution is trusted
  with moderation
• Trust in the decisions of the people/institution necessary

a. Docker Hub Trusted Content

• Docker Hub Trusted Content
• Released on May 27th 2021
• Uses different flags on images
• Flags indicate different reasons why docker deems
  them trustworthy

a. Docker Hub Trusted Content in Real Life

a. Docker Hub Trusted Content in Real Life

b. Signatures

• Proof first approach
• Signing packages to proof the integrity and authenticity
  of an package
• Trust has to be put in the handling of keys and implementation
  of processes

b. Signature

• Wasn’t initially possible with Docker Images
• Changed with Docker Image Format 1.10
• Current examples:
  • Docker Trust System
  • Sigstore

Agenda

1. Packaging as Complexity Reduction
2. An Approach to Trust
3. Sigstore
4. Conclusion

Sigstore

• Collection of tools, standards and processes
• Ensures integrity and authenticity of artifacts independent of registry
• Purpose build for use with Containers and Container Orchestration
• Uses short lived certificates and certificate transparency

How Sigstore Handles Trust?

• Uses different technologies to reduce necessary trust
  through it’s components
• Infrastructure consists of:
  • Trust Root
  • Fulcio (+ additional certificate transparency log)
  • Rekor
  • (Cosign, CLI for signing and verifying)

Sigstores Infrastructure Overview

Sigstore Infrastructure Components

Sigstore TUF

Sigstore Fulcio

Sigstore Rekor

Sigstore Signing Process

Sigstore Publishing Process

Sigstore Verification Process

Integrating Sigstore into Kubernetes

• Two ways of integrating Sigstore:
  • a. Via the Container Runtime Cri-O
  • b. Via an Admission Controller

a. Cri-O Integration

• Integration via Cri-O container runtime
• Alternative OCI (Open Container Initiative)-compatible runtime
• Uses containers/image libraries

a. Policies

• containers/image allows to define requirements for downloading images
• Configured via policy.json file on orchestrator node
• Can require:
  • Scope
  • Signatures and their formats

a. Cri-O Configuration

• Example configuration for requiring Sigstore signing [3]:

b. Admission Controller Integration

• Define custom plugins that intercept calls to the Kubernetes API
  and either validates or modifies them (since Kubernetes 1.25)
• Sigstore project provides a policy controller to
  define requirements on the download of container images
• Is still under development

b. Admission Controller Configuration

• Introduces the ClusterImagePolicy object to define polices
• Policies are defined on a per namespace basis
• Enabled by adding label policy.sigstore.dev/include=true to a namespace

b. Configuring a ClusterImagePolicy

• Example ClusterImagePolicy [4]:

Agenda

1. Packaging as Complexity Reduction
2. An Approach to Trust
3. Sigstore
4. Conclusion

Conclusion

• Provides system that ensures authenticity and integrity
• Registry independent
• Works as independent third party
• Makes Package the Management approach scalable

Caveats

• Solves a very specific problem
• Good security practices and transparent processes have to follow
• Introduces complexity as well
• In the end a corner stone to build upon