Exploring the Code Signing Software Development Life Cycle
The process of Software Development Life Cycle (SDLC) is essential to maintain the quality and security of software applications. Integrating code signing, into the SDLC adds a level of security and trust for software products. Code signing plays a role, in confirming the legitimacy of the software developer and upholding the integrity of the code.
This article aims to discuss the concept of code signing and its advantages along, with providing guidance on integrating it into your software development life cycle (SDLC). Additionally it will delve into the recommended strategies, for handling code signing certificates and keys as part of the SDLC process to enhance software security and user confidence.
Key Takeaways
- Code signing applies digital signatures to software to verify publisher identity and code integrity.
- Integrating code signing improves SDLC security and trust by preventing tampering and proving authenticity.
- Code signing certificates from a trusted certificate authority prove identity to users and systems.
- By automating signing and managing keys properly, the overhead of code signing is minimized.
- Best practices include securing private keys, planning for certificate renewals, and automating where possible.
An Introduction to Code Signing Essentials
Digital signatures are used in code signing to confirm the identity of the creator and guarantee that the software code remains unchanged establishing trust through authentication of the code source and its integrity.
When using signatures, in encryption processes like private key pairs are essential components, for ensuring security. The code gets signed with the key to generate a signature which is later attached to the code. To verify the authenticity of the signature users need to employ the corresponding key.
Confirming the signature validates the identity of the publisher. Shows that the code has not been altered since it was signed. If there have been any modifications made the signature would no longer be valid.
The software can be signed at any point during its development process. Usually the signing of the software occurs just before it is distributed to end users. Code signing guarantees that users are receiving software from the developer that has not been altered in any way.
What are the Benefits of Code Signing in SDLC
Integrating code signing into the software development life cycle offers numerous benefits:
- Trust: Validation, through signed code enhances trust in software by assuring users that they are downloading an application, from the developers source.
- Security: Software security is enhanced through code signing, which acts as a safeguard, against alterations to programs by verifying signatures to thwart changes, to installed software.
- Compliance: In sectors, like healthcare and finance or public services industries often need signed codes to adhere to standards and regulations, for specific applications.
- Reputation: Brand reputation is enhanced through code signing as it assures users that the software they are installing is genuine instilling trust, in the publishers commitment, to integrity and security.
- Compatibility: Certain operating systems and software require signed code, for installation to maintain compatibility, with them and their applications.
How to Implement Code Signing into SDLC
To gain these benefits, code signing should be incorporated early in the SDLC.
Here are the best practices for adding code signing:
- Obtain Certificates: Buy code signing certificates from a reputable certificate authority like DigiCert, Comodo, or GlobalSign. Most systems and browsers trust these certificates.
- Secure Keys: Store private keys securely using a hardware security module or secure cloud key storage. This prevents unauthorized access for signing fraudulent code.
- Integrate Signing: Automate code signing into the build process through tools like Signtool, SignCode, or Eclipse. This ensures all new builds get signed.
- Validate Signatures: Before release, validate signatures to verify signed code has not been altered. This confirms the signing process worked properly.
- Document Procedures: Document code signing procedures like certificate issuance, private key access, and signature validation. This codifies the process for consistency.
- Plan Renewals: Establish procedures to track expiration dates and renew code signing certificates in a timely manner. This will prevent any business disruption.
Best Practices for Code Signing SDLC
Follow these best practices when implementing code signing into your SDLC to maximize security and avoid issues:
Secure Private Keys
Restrict access to private keys used for code signing only to authorized persons through key management systems. Store signing keys offline in secure hardware, such as a FIPS 140-2 certified HSM or USB device.
Automate Signing and Validation
Integrate signing tools into the build automation process to sign code consistently without manual intervention. Validate signatures on all builds before release to catch errors.
Assign Dedicated Signing Certificates
Use a unique code signing certificate for each signing authority, purpose, and expiration date. Do not reuse or dual-purpose certificates since compromised keys would require mass revocation.
Renew Expiring Certificates
Set calendar reminders to renew code signing certificates at least 30 days before expiration. Obtain new certificates from the same trusted CA and reuse previous keys to avoid business disruption.
Manage Trusted Root Stores
Distribute renewed certificate public keys to developer and user systems to update trusted root stores. This maintains trust in renewed certificates for validating signed codes.
Plan for Compromised Keys
Have a plan to quickly revoke compromised certificates and issue new certificates with new keys. Notify operating system vendors to revoke trust in compromised certificates present in root stores.
Use Multiple Signature Formats
Sign code using Authenticode, Java, and other platform-specific formats to ensure signature validation on all target systems, such as Windows, Mac, Linux, mobile, etc.
Sign Third-Party Libraries
When integrating third-party libraries, either obtain signed libraries or sign them yourself after validation. Otherwise, unsigned code will trigger trust warnings.
By following these best practices for your code signing SDLC process, you can release trusted software efficiently.
Code Signing Certificate Types
There are several different classes and types of code-signing certificates to choose from:
Code Signing Certificates
Standard code signing certificates validate normal software code, such as applications, installers, scripts, and other executables. They provide the highest level of trust for most use cases.
EV Code Signing Certificates
Extended Validation code signing offers enhanced validation of the publisher identity with green address bar indicators. EV provides maximal assurance for critical software like financial applications.
Kernel Mode Signing Certificates
Specialized kernel mode certificates, which require additional vetting, are required to sign device drivers and low-level system code that runs in kernel mode.
Timestamp Certificates
Timestamp certificates embed the signing time into signatures. This extends the validity of signatures past the certificate expiration since the timestamp proves it wasn’t signed after expiration.
Document Signing Certificates
Used to sign documents and macros within documents like Microsoft Office files. This ensures authenticity and prevents tampering with records.
Choose certificates suitable for the code type, risk level, and signing requirements. Use EV certificates for high-value software and kernel mode certificates for device drivers.
Code Signing Certificate Authorities
The certificate authority (CA) issues and guarantees the validity of code signing certificates:
GlobalSign
GlobalSign is one of the largest public CAs offering all types of code signing certificates, including EV and kernel mode certificates. It’s trusted in all major root stores.
DigiCert
DigiCert offers rapid certificate issuance and management through its CertCentral portal. It also offers code signing certificates that are compliant with all major signature platforms.
Comodo
Comodo is known for low-cost certificates. It offers basic code signing certificates along with EV options. However, it requires stringent vetting for high-assurance certificates.
Sectigo
Sectigo combines rapid issuance with compliance tools, such as its Certificate Inventory Tool, to manage large numbers of certificates across an organization.
The CA you choose should be widely trusted across operating systems and browsers. DigiCert, GlobalSign, Comodo, and Sectigo are among the most universally trusted.
Self-Signed vs. CA-Signed Certificates
Code signing certificates can either be self-signed or obtained from a CA:
- Self-Signed: The publisher generates their certificate and private key used to sign the code. Provides no external validation.
- CA-Signed: The certificate is issued by a trusted external CA that verifies the publisher’s identity. Provides robust external validation.
How to Implement Authenticode Signing
Authenticode signing should be implemented to sign Windows executable code like .exe, .dll, .ocx, .msi, .cab, and .ps1 files. Authenticode provides these benefits:
- Publisher Identity Validation: Authenticode certificates verify the identity of the publisher through the issuing CA.
- Code Integrity Checks: Authenticode ensures the code has not been altered since the publisher signed it.
- Trusted Publisher Alerts: Windows SmartScreen warns users about running applications from unknown publishers.
To enable Authenticode:
- Acquire a code signing certificate from a trusted CA like DigiCert or Comodo.
- Secure private keys in hardware like an HSM to prevent unauthorized access.
- Use Signtool or SignCode build tools to sign Windows executables automatically.
- Verify Authenticode signatures on all builds prior to release.
- Renew Authenticode certificates prior to expiration to maintain trust.
Properly implementing Authenticode signing hardens Windows applications against tampering and malicious software. It gives users confidence in installing and running Windows software protected by Authenticode.
How to Implement Java Code Signing
For Java applications and JAR files, Oracle provides a code signing framework to validate identities and code integrity:
- Java Canonicalized Signing: Signs JAR files using PKCS #7 signature files (SIG). Verifies with the jarsigner tool.
- crypto Code Signing: Uses private keys and certificates to sign class files digitally. Validated with keytool.
- JAR Manifest Signing: Embeds signatures in MANIFEST.MF to protect the entire JAR archive.
To enable Java code signing:
- Obtain a Java code signing certificate from a CA like DigiCert.
- Use keytool to generate public-private key pairs for signing class files.
- Sign JARs using Eclipse JDT, jarsigner, or Maven plugin.
- Validate signed JARs using jarsigner or keytool verification.
- Distribute public key to Java keystores to establish trust.
Code signing ensures that Java applications and JARs have not been compromised and can be trusted. It also verifies the software publisher’s identity.
How to Implement Mac Developer ID Signing
For macOS software, Apple provides Developer ID signing to the gatekeeper for verifying authenticity:
- Developer ID Certificates: Obtained from the Apple Developer Program used to sign Mac software digitally.
- Gatekeeper: Checks Developer ID signature before allowing macOS apps from the App Store or Internet to run.
- Stapled to Apps: Signatures embedded in binaries inform Gatekeeper the app is signed.
To enable Mac Developer ID signing:
- Enroll in the Apple Developer Program to access signing certificates.
- Use Xcode to sign compiled macOS applications and installers.
- Validate signatures embedded in apps using spctl or codesign command line tools.
- Submit signed apps to Apple for notarization to confirm security.
Developer ID signing allows macOS Gatekeeper to block potentially malicious unsigned apps and provides integrity assurances for end users.
How to Improve SDLC Security with Code Signing
Integrating code signing improves SDLC security by:
- Preventing Tampering: Unsigned code can be easily modified, which compromises integrity. Code signing blocks malicious tampering.
- Verification of Authenticity: Code signatures prove to users the software came from a legitimate publisher unchanged.
- Compliance with Industry Standards: Code signing meets security compliance requirements for medical, finance, retail, and other regulated industries.
- Enhancing Reputation: Consistently signed software instills trust and confidence in users that the publisher values integrity and security.
Start applying code signing early in development and integrate signing into build automation. Validate all signatures prior to release. This bakes security into each stage of the SDLC.
Carefully manage private keys and plan for certificate renewals. By following code signing best practices, organizations can optimize security while minimizing overhead.
Final Thoughts
In summary, code signing is a critical component of the software development life cycle (SDLC). By signing code at each stage, developers can ensure the integrity and authenticity of their software, protecting users from malware and unauthorized modifications. Integrating code signing into the SDLC helps organizations maintain a secure and trusted software development process from initial planning through deployment and updates.
As software threats continue to evolve, adhering to best practices for code signing will remain essential for safeguarding applications and building user confidence. Developers who prioritize code signing throughout the SDLC are better positioned to deliver secure, reliable software.
Frequently Asked Questions About Code Signing SDLC
What is code signing used for in software development?
Code signing applies digital signatures to compiled software to verify the publisher’s identity and ensure that the code has not been altered or corrupted since it was signed. This protects software integrity.
When should code signing be implemented in SDLC?
Code signing should be added early in development. Signing should be automated as part of the build process to sign all code prior to release. Certificates and keys should be provisioned in the design phase.
Does code signing guarantee the software is safe and secure?
No. Code signing verifies the integrity of the code and the publisher’s identity only. To ensure security, the software still needs to be developed using secure coding practices and tested for vulnerabilities.
What are the most common code-signing certificate authorities?
The most commonly trusted certificate authorities for code signing certificates are DigiCert, Comodo, GlobalSign, Sectigo, and Symantec. Microsoft also provides trusted code signing certificates.
How long are code signing certificates valid?
Code signing certificates usually have a validity of 1-3 years. Certificate expiration dates should be tracked to renew proactively and avoid disruptions.
What happens if code signing private keys are compromised?
If a code signing key is lost or stolen, notify the issuing certificate authority immediately to revoke the certificate. Once revoked, signatures from the certificate will fail validation. New certificates with new keys need to be issued.
Can unsigned code be distributed and installed?
Some operating systems, like Windows and macOS, block the installation of unsigned code. Even if allowed, unsigned code will trigger warnings and lack the integrity assurances of signed code.
What are the risks of not implementing code signing?
Without code signing, software lacks trust because there is no proof the code is legitimate and unaltered. Malicious unsigned code can be substituted, putting users at risk for malware or tampering.
What tools automate code signing?
Tools like Signtool, SignCode, jarsigner, and Eclipse plug-ins can automatically apply signatures during build automation. ANT, Maven, Gradle, make, and other build tools also support automated signing.
Priya Mervana
Verified Web Security Experts
Priya Mervana is working at SSLInsights.com as a web security expert with over 10 years of experience writing about encryption, SSL certificates, and online privacy. She aims to make complex security topics easily understandable for everyday internet users.
