blog: supply chain robots, electric sheep, and SLSA

docs/_posts/2025-12-03-supply-chain-robots-slsa.md

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+---
+title: "Supply Chain Robots, Electric Sheep, and SLSA"
+author: "Brett Smith"
+is_guest_post: true
+---
+
+# Supply Chain Robots, Electric Sheep, and SLSA
+
+By Brett Smith, Distinguished Software Developer at SAS Institute
+
+## Why is securing the supply chain important?
+
+In my mind's eye, the "electric sheep" are the products we build and sell to
+generate revenue. To create "electric sheep", we build "supply chain robots"
+that dream of "electric sheep". The robots are our automated pipelines, our
+CI/CD systems, and our infrastructure. They construct the sheep, herd them along
+the software development lifecycle (SDLC), and shepherd them to market.
+
+That all sounds great but, there are wolves at the door. Smart digital wolves.
+And they are not just trying to eat the electric sheep, they mean to reprogram
+the robots, poison the assembly line, and turn our own infrastructure against
+us. The reality of software supply chain security today is that we need supply
+chain robots to protect everything from the digital wolves.
+
+## Why This Matters
+
+After a few major attacks, the government decided to protect itself as
+governments should. On May 12, 2021, the White House dropped Executive Order
+14028 on Cybersecurity. And with that, if you wanted to sell to the federal
+government, you had a whole new set of regulations to meet.
+
+So you skim the Executive Order. It reads like an android interpretation of
+lawyers and lawmakers notes on engineering security documentation. Excellent
+vague bits like the following:
+
+-   **PO.5.1**: Separate and protect each environment involved in software
+  development
+-   **PO.5.2**: Secure and harden development endpoints
+-   **PW.6.1**: Use compiler, interpreter, and build tools that offer security
+  features
+-   **PW.6.2**: Determine which tool features should be used and implement
+  approved configurations
+-   **PS.1.1**: Store all forms of code based on least privilege principles
+-   **PS.3.2**: Collect, safeguard, maintain, and share provenance data for all
+  software components
+
+For reference it sends you down the rabbit hole of NIST standards, which are
+just as vague. The next step is to leverage your company's ISO subscription to
+start digging into ISO 27001. ISO 27002 guidelines give you a glimmer of hope
+but still no real answers.
+
+How do you turn this mountain of abstract policy into concrete action?
+
+## SLSA: From Confusion to Clarity
+
+SLSA (pronounced "salsa") is a comprehensive security framework for software
+supply chains. Think of it as a maturity model - organizations can progressively
+improve their security posture by advancing through levels. Each track focuses
+on different aspects of the supply chain: Build focuses on artifact creation
+integrity, while Source focuses on code trustworthiness. The framework is
+designed to be practical and incrementally adoptable, allowing organizations to
+start where they are and improve over time. Version 1.2-rc1 introduces the
+reintegrated Source Track after focusing solely on Build in v1.0.
+
+SLSA provides us with:
+
+-   A common vocabulary to talk about software supply chain security
+-   A way to secure your incoming supply chain by evaluating the trustworthiness
+  of the artifacts you consume
+-   An actionable checklist to improve your own software’s security
+-   A way to measure your efforts toward compliance with the Secure Software
+  Development Framework (SSDF)
+
+The framework establishes three trust boundaries encouraging the right
+standards, attestation, and technical controls, so we can harden the system from
+these threats and risks. SLSA is a check-list of standards and controls to
+prevent tampering, improve integrity, secure packages and infrastructure in your
+projects, platform, and enterprises. It is about identifying and closing attack
+vectors in the Supply Chain and proper governance of artifacts throughout the
+chain.
+
+Validating Artifact Integrity through verification is a key component of SLSA
+which helps to:
+
+-   Prevent Integrity Attacks
+-   Prevent Unauthorized Modifications
+-   Validate Artifact Integrity
+-   Close Attack Vectors
+
+Most importantly for our EO 14028 journey: SLSA translated policy requirements
+into technical implementation steps.
+
+## The Two Tracks: Build and Source
+
+The two tracks are complementary but independent. Build Track has levels L0-L3,
+while Source Track has levels L1-L4. Organizations can advance on one track
+without necessarily being at the same level on the other, though both are
+important for comprehensive supply chain security. The Build Track addresses
+threats during the compilation and packaging phase, while Source Track addresses
+threats in code creation and management. Together, they provide end-to-end
+visibility and protection from source code to deployed artifact.
+
+### Build Track: The Provenance Receipt
+
+The Build Track uses provenance as a receipt for your software build. It answers
+three critical questions:
+
+1.  **Identity of the builder** - Who or what built this?
+2.  **The build process used** - How was it built?
+3.  **What inputs went into the build** - What materials were used?
+
+This matters because many supply chain attacks happen during the build phase:
+attackers compromise build systems, inject malicious code, or substitute
+artifacts. Provenance creates an auditable trail.
+
+**Build L0**: No guarantees; you're not doing SLSA yet
+
+**Build L1**: Provenance exists
+
+-   Basic provenance generated and distributed
+-   Prevents mistakes, but easy to bypass
+-   Quick to implement with minimal workflow changes
+-   _This got us started on EO requirements for provenance data_
+
+**Build L2**: Hosted build platform
+
+-   Provenance signed by the build platform itself
+-   Requires explicit attack to forge
+-   Move to platforms like GitHub Actions, GitLab CI, or Google Cloud Build
+-   _This addressed PW.6.1 and PW.6.2: using hardened build tools_
+
+**Build L3**: Hardened builds
+
+-   Strong tamper protection during the build
+-   Isolated build environments
+-   Prevents insider threats and credential compromise
+-   _This satisfied PO.5.1 and PO.5.2: environment separation and hardening_
+
+Build L3 became our target for most releases. It requires significant platform
+investment but provides strong protection against sophisticated attacks.
+
+**Future Build Track Level 4** (in development) aims to add even stronger
+guarantees, including:
+
+-   Pinned dependencies, which guarantee that each build runs on exactly the same
+  set of inputs.
+-   Hermetic builds, which guarantee that no extraneous dependencies are used.
+-   All dependencies listed in the provenance, which enables downstream verifiers
+  to recursively apply SLSA to dependencies.
+-   Reproducible builds, which enable other build platforms to corroborate the
+  provenance.
+
+### Source Track: Trust from Code to Commit
+
+The Source Track addresses "How do we know this source code is what the
+organization intended?" It focuses on the change management process: how code
+gets into the repository and onto protected branches.
+
+**Source L1**: Version controlled
+
+-   Code in a modern version control system like Git
+-   Foundation for operational maturity
+-   _This covered PS.1.1: proper storage of all code forms_
+
+**Source L2**: Controls enforced
+
+-   Protected branches and tags identified
+-   All changes recorded and tracked
+-   Technical controls enforced
+-   _This ensured proper access control and change tracking_
+
+**Source L3**: Signed and auditable provenance
+
+-   Source Control System generates tamper-resistant evidence
+-   Contemporaneous documentation of revision creation
+-   Strong guarantees for change management
+-   _This delivered the PS.3.2 requirement: collecting and safeguarding
+  provenance_
+
+**Source L4**: Two-party review
+
+-   Requires two trusted persons to review all changes
+-   Makes unilateral malicious changes much harder
+-   _This became our gold standard for production code_
+
+## Conclusion: From Chaos to Compliance
+
+SLSA isn't just a checklist, it is a comprehensive framework that addresses
+supply chain security systematically. The two tracks, source code security and
+build integrity, complement each other. No need to achieve the highest levels
+immediately, start where you are and progress incrementally. The attestation
+model is powerful. It creates verifiable evidence that can be validated by any
+consumer without requiring trust in just one party.
+
+Implementation details vary by ecosystem because what works for Python is
+different from what works for Rust, but the principles remain consistent. Start
+with Build L1 or Source L2 and progress from there. Both tracks are important
+for comprehensive security, though you may prioritize one based on your specific
+threats.
+
+If you have a lot of electric sheep, you need a fleet of supply chain robots to
+tend them. Build a platform to manage the chaos, herd the cats, eliminate the
+unicorns, and eradicate the chaos from your Software Supply Chain.
+
+SLSA is how we get from safe enough to being as resilient as possible, at any
+link in the chain.
+
+When we started this journey, Executive Order 14028 was nothing more than pages
+of requirements with no clear implementation path. SLSA translated those
+abstract requirements into concrete, measurable levels. Build Track mapped to
+build tool requirements and environment hardening. Source Track mapped to access
+control and provenance collection.
+
+The incremental nature of SLSA levels meant we could show progress, justify
+investment, and continuously improve rather than attempting a massive
+all-at-once transformation.
+
+You now have an EO 14028 compliant pipeline. Use it for everything.
+
+The pipeline builds the pipeline. Use SLSA as your roadmap. Build a platform to
+manage the chaos.
+
+And remember: compliance doesn't equal security, but SLSA helps you achieve
+both.
+
+---
+
+_Brett Smith is a Distinguished Software Developer at SAS Institute, where he
+helps architect and secure supply chain pipelines for an Analytics,
+AI, and Data Management company._