1. Introduction to Supply-chain Levels for Software Artifacts
  2. Basic Supply-chain Components in Software Artifacts
  3. Intermediate Levels of Supply-chain for Software Artifacts
  4. Advanced Supply-chain Strategies for Software Artifacts
  5. Supply-chain Levels for Software Artifacts: Threats and Mitigations
  6. Best Practices and Optimization in Supply-chain Levels for Software Artifacts


In the digital era, the software supply-chain has emerged as a pivotal aspect, underpinning the development, deployment, and maintenance of software artifacts. With a half-decade of hands-on experience navigating this intricate domain, this article aims to elucidate the multifaceted dimensions of supply-chain levels for software artifacts, setting the stage for our subsequent deep-dive into Supply-chain Levels for Software Artifacts in this six-article series.

Definition and Overview

The software supply-chain delineates the intricate network of processes, tools, and practices orchestrating the lifecycle of software artifacts[^1^]. Unlike its tangible counterpart in manufacturing, the software supply-chain encompasses intangible elements—source code, dependencies, configurations—requiring nuanced management and governance mechanisms. This abstraction signifies a paradigm shift from linear, sequential workflows to dynamic, iterative cycles inherent to software development.

Distinguishing Features:

– Intangibility: Managing virtual assets, emphasizing metadata, provenance, and traceability.
– Interdependencies: Navigating complex relationships between artifacts, dependencies, and environments.
– Automation: Leveraging automation to ensure repeatability, consistency, and efficiency across the supply-chain.

Importance in Software Development

The software supply-chain serves as the linchpin for:

– Software Quality Assurance: Enabling robust build pipelines, automated testing, and continuous integration, fostering a culture of quality.

– Security Protocols: Instituting access controls, encryption, and vulnerability management, safeguarding against threats and breaches.

– Accelerated Delivery: Streamlining deployment workflows, optimizing release cycles, and promoting agility in software delivery.

Impact Areas:

– Collaboration: Fostering cross-functional collaboration, knowledge sharing, and collective ownership.
– Transparency: Promoting visibility into workflows, processes, and artifact lineage, enhancing accountability and trust.

Security Levels

SLSA is organized into a series of levels that provide increasing integrity guarantees. This gives you confidence that software hasn’t been tampered with and can be securely traced back to its source.

Level Zero

Description: No guarantees. SLSA 0 represents the lack of any SLSA level.

Level 1

Description: Documentation of the build process

The build process must be fully scripted/automated and generate provenance. Provenance is metadata about how an artifact was built, including the build process, top-level source, and dependencies. Knowing the provenance allows software consumers to make risk-based security decisions. Provenance at SLSA 1 does not protect against tampering, but it offers a basic level of code source identification and can aid in vulnerability management.

Example: Unsigned provenance

Level 2

Description: Tamper resistance of the build service

Requires using version control and a hosted build service that generates authenticated provenance. These additional requirements give the software consumer greater confidence in the origin of the software. At this level, the provenance prevents tampering to the extent that the build service is trusted. SLSA 2 also provides an easy upgrade path to SLSA 3.

Example: Hosted source/build, signed provenance

Level 3

Description: Extra resistance to specific threats

The source and build platforms meet specific standards to guarantee the auditability of the source and the integrity of the provenance respectively. We envision an accreditation process whereby auditors certify that platforms meet the requirements, which consumers can then rely on. SLSA 3 provides much stronger protections against tampering than earlier levels by preventing specific classes of threats, such as cross-build contamination.

Example: Security controls on host, non-falsifiable provenance

Level 4

Description: Highest levels of confidence and trust

Requires two-person review of all changes and a hermetic, reproducible build process. Two-person review is an industry best practice for catching mistakes and deterring bad behavior. Hermetic builds guarantee that the provenance’s list of dependencies is complete. Reproducible builds, though not strictly required, provide many auditability and reliability benefits. Overall, SLSA 4 gives the consumer a high degree of confidence that the software has not been tampered with.

Example: Two-party review + hermetic builds

Historical Context and Evolution

The trajectory of software development underscores a transformative evolution, influenced by:

– Open Source Revolution: Catalyzing collaborative development, fostering innovation, and democratizing access to resources.

– Cloud Paradigm Shift: Redefining infrastructure management, driving automation, scalability, and agility imperatives.

– Security Imperatives: Responding to evolving threat landscapes, amplifying the emphasis on secure coding, compliance, and governance.

Evolutionary Milestones:

– Waterfall to Agile: Transitioning from rigid, sequential methodologies to flexible, iterative frameworks.
– Monolith to Microservices: Embracing modular architectures, facilitating scalability, resilience, and maintainability.

Key Components of a Software Supply-chain

A cohesive software supply-chain comprises pivotal components:

1. Source Code Repositories: Platforms like GitHub, GitLab facilitating collaborative development, version control, and code reviews.

2. Build Automation Tools: Jenkins, Travis CI orchestrating build processes, artifact generation, and integration with other tools.

3. Artifact Repositories: JFrog Artifactory, Nexus managing software binaries, dependencies, ensuring versioning, and artifact governance.

4. Configuration Management: Ansible, Puppet automating configuration, ensuring consistency, and enforcing desired state configurations.

5. Deployment Orchestration: Kubernetes, Terraform managing deployment pipelines, infrastructure as code, and environment provisioning.

Challenges and Risks

The software supply-chain landscape presents multifarious challenges:

– Complexity Overhead: Juggling diverse tools, platforms, and environments, necessitating robust governance, standardization, and orchestration.

– Security Vulnerabilities: Exposing vulnerabilities through misconfigurations, outdated components, and insufficient security postures.

– Regulatory Compliance: Navigating regulatory landscapes, licensing intricacies, and ensuring adherence to industry standards.

Risk Mitigation Strategies:

– Governance Frameworks: Implementing governance models, policies, and controls to enforce compliance and mitigate risks.
– Continuous Monitoring: Leveraging monitoring tools, anomaly detection, and real-time insights to preemptively identify and address vulnerabilities.


As we embark on a comprehensive exploration of Supply-chain Levels for Software Artifacts, anchoring our understanding within the broader context of software supply-chain levels becomes paramount. Recognizing its historical evolution, emphasizing its pivotal role in software development, and proactively addressing inherent challenges empowers organizations to architect resilient, secure, and efficient software delivery pipelines.

[^1^]: Reference: Software Supply Chain: A Critical Aspect of Cybersecurity. U.S. Cybersecurity and Infrastructure Security Agency (CISA).

Note: This article synthesizes personal experience, industry insights, and best practices to provide a comprehensive overview of supply-chain levels for software artifacts. It serves as a foundational resource, inviting further exploration and contextual adaptation based on organizational nuances and evolving industry dynamics.

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