The initial draft version (v0.1) of SLSA had a larger scope including protections against tampering with source code and a higher level of build integrity (Build L4). This page collects some early thoughts on how SLSA might evolve in future versions to re-introduce those notions and add other additional aspects of automatable supply chain security.
A build L4 could include further hardening of the build platform and enabling corraboration of the provenance, for example by providing complete knowledge of the build inputs.
The initial draft version (v0.1) of SLSA defined a “SLSA 4” that included the following requirements, which may or may not be part of a future Build L4:
- 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.
A Source track could provide protection against tampering of the source code prior to the build.
The initial draft version (v0.1) of SLSA included the following source requirements, which may or may not form the basis for a future Source track:
- Strong authentication of author and reviewer identities, such as 2-factor authentication using a hardware security key, to resist account and credential compromise.
- Retention of the source code to allow for after-the-fact inspection and future rebuilds.
- Mandatory two-person review of all changes to the source to prevent a single compromised actor or account from introducing malicious changes.
Build Platform Operations track
A Build Platform Operations track could provide assurances around the hardening of build platforms as they are operated.
The initial draft version (v0.1) of SLSA included a section on common requirements that formed the foundation of the guidance for verifying build systems, which may or may not form the basis for a future Build Platform Operations track:
- Controls for approval, logging, and auditing of all physical and remote access to platform infrastructure, cryptographic secrets, and privileged debugging interfaces.
- Conformance to security best practices to minimize the risk of compromise.
- Protection of cryptographic secrets used by the build platform.