Secure Build and Release Processes

A secure build and release process protects the path between your source code and the device in the field. That means a hardened build environment, signed build artifacts, and protected distribution channels. Skip any one of these and an attacker can ship malicious code under your name, to every device you make.

4.6.1 Build Environment Security

Your build environment is a critical attack target. If compromised, every device you ship is vulnerable.

Securing the Build Pipeline

Infrastructure Security

• Isolated build networks
• Access control and logging
• Regular security updates
• Malware scanning

Source Code Protection

• Version control security
• Code signing commits
• Access restrictions
• Audit trails

Build Process Integrity

flowchart LR
    A[Secure Source Repo] --> B[Authenticated Checkout]
    B --> C[Clean Build Environment]
    C --> D[Dependency Verification]
    D --> E[Build Process]
    E --> F[Output Signing]
    F --> G[Secure Storage]

4.6.2 Code Signing and Integrity

Code signing proves your software hasn't been tampered with.

Implementation Requirements

Digital Certificates

• Use code signing certificates
• Hardware security module (HSM) storage
• Regular certificate rotation
• Revocation planning

Signing Process

1. Build completes successfully
2. Calculate hash of build artifacts
3. Sign hash with private key
4. Attach signature to artifacts
5. Verify signature independently
6. Store signed artifacts securely

Verification Implementation

// Example: Boot-time verification
bool verify_firmware_signature() {
    // Load firmware image
    uint8_t* firmware = load_firmware();
    size_t size = get_firmware_size();
    
    // Extract signature
    signature_t* sig = extract_signature(firmware);
    
    // Calculate hash
    uint8_t hash[32];
    sha256(firmware, size - sizeof(signature_t), hash);
    
    // Verify signature
    return rsa_verify(sig, hash, PUBLIC_KEY);
}

4.6.3 Secure Distribution

How you deliver software to devices matters.

Update Package Security

Package Contents

• Signed firmware/software
• Version information
• Rollback data
• Installation scripts
• Integrity checksums

Secure Channels

• TLS for network delivery
• Encrypted physical media
• Authenticated endpoints
• Certificate pinning

For the full update-path architecture from root of trust to anti-rollback, see Ensuring secure software updates for medical devices.