A SSLippery Slope: Unraveling Hidden Dangers of Certificate Misuse
Bill Demirkapi uncovers systemic validation flaws in digital signature implementations, allowing attackers to repurpose incompatible certificates to sign untrusted code.
Summary
The Critical Role of Code Signing Certificates
Digital code signing certificates undergo rigorous identity vetting to establish publisher trust, ensuring operating systems only execute authenticated binaries and firmware updates.
Discovering Systemic Signature Validation Flaws
Bill Demirkapi investigates parsing logic across major operating system loaders and signature verification APIs, discovering critical oversights in Enhanced Key Usage (EKU) checks.
Bypassing Trust Boundaries with Incompatible Certificates
Vulnerable verifiers mistakenly accept signatures generated by cheap or unrelated TLS/S-MIME certificates as valid code signing credentials, allowing adversaries to sign malicious payloads.
Hardening Cryptographic Verification Pipelines
The author outlines comprehensive remediation steps for operating system developers and software vendors to strictly enforce certificate purpose constraints and signature chain validation.
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