Phase 6: Supply Chain Security & Slopsquatting · 50 min · pip-compile · npm ci · hashlib

Lockfile Enforcement & Hash Verification

Pin versions. Verify hashes. Block substitution. Enforce in CI.

Hiring signal: Engineers who can enforce lockfile pinning and hash verification in CI demonstrate production-grade supply chain security skills and prevent package substitution attacks.

What you will learn

Enforce lockfile pinning to prevent version drift in AI-generated code
Implement hash verification to detect package substitution attacks
Prevent package substitution by regenerating dependency trees from approved lockfiles
Apply the agent-cicd pattern for dependency gates in CI

The Problem

Even with allowlists (Lesson 3) and SBOMs (Lesson 4), there's one more attack vector: package substitution. An attacker compromises a legitimate package on the registry, replacing version 1.2.3 with malicious code while keeping the same version number. Without lockfile pinning and hash verification, your CI/CD will install the compromised version. This lesson covers lockfile enforcement and hash verification to prevent substitution attacks.

The Package Substitution Attack

1. Your lockfile says: requests==2.28.0
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2. Attacker compromises PyPI account of requests maintainer
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3. Attacker uploads malicious code as requests 2.28.0 (same version)
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4. Your CI runs: pip install -r requirements.txt
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5. pip downloads "requests 2.28.0" -- but it's the attacker's version
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6. Malicious code executes in CI
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7. Attacker steals CI/CD tokens, source code, secrets

Defense: Lockfile Pinning + Hash Verification

1. Your lockfile says: requests==2.28.0 --hash=sha256:abc123...
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2. Attacker uploads malicious code as requests 2.28.0
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3. Your CI runs: pip install --require-hashes -r requirements.txt
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4. pip downloads "requests 2.28.0"
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5. pip calculates SHA-256 hash of downloaded package
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6. Hash doesn't match abc123... (attacker's code has different hash)
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7. pip REFUSES to install -- ERROR: Hash mismatch
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8. CI fails, merge blocked, attack prevented

Unlock the full lesson

You've read the first 2 sections. The rest of this lesson covers Lockfile Pinning, The Agent-CICD Pattern for Dependency Gates, Build It — plus a hands-on lab, quiz, and project artifact.

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Key terms in this lesson

Agent