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RFC-0133: Software Delivery Goals

RFC-0133: Software Delivery Goals
StatusAccepted
Areas
  • Software Delivery
Description

A set of long-term goals for the Software Delivery area.

Gerrit change
Authors
Reviewers
Date submitted (year-month-day)2021-09-08
Date reviewed (year-month-day)2021-10-04

Summary

A set of long-term goals for the Software Delivery area.

Motivation

The Fuchsia Software Delivery system needs to prioritize the requirements of our customers and will continue to do so, but we also need to set long-term direction to keep in mind as we do design. Even though we don't have explicit customer requirements for many of these goals, they are nonetheless goals that we should design for and keep in mind as we evolve the system. This list may change over time, and that's fine. However, this represents the desired state of the world today.

Stakeholders

Facilitator:

hjfreyer@google.com

Reviewers:

  • abarth@google.com - FEC
  • amathes@google.com - Product
  • computerdruid@google.com - SWD
  • ampearce@google.com - Security

Consulted:

  • kitlane@google.com
  • mckillop@google.com
  • hjfreyer@google.com
  • Software Delivery team

Socialization:

This RFC went through a review in doc form with the Software Delivery team, as well as with the contributors.

Design

Goals

  1. Prioritize customer requirements: We shouldn't be afraid to revisit existing implementations or change strategy if we have a compelling customer need, as long as we don't preclude long-term goals.
  2. One update protocol in production: All devices in production use the same update stack and protocol for platform OTA s as we recommend to our customers for updating other software.
  3. Platform and non-platform updates have the same features: Platform OTAs and updates for independent modules have the same capabilities (channels, staged rollouts, stepping stones, etc.), and it should be possible for OSS users to use these capabilities.
  4. Minimize monoliths: Over time, we intend most parts of the platform to be independently updatable.
  5. Provide recovery options for attacks which can modify persistent state: The SWD stack should be able to perform an update automatically at boot with minimum dependence on mutable data and other software in order to maximize recovery potential from serious vulnerabilities, including ones which give an attacker the ability to modify persistent state.
  6. Update reliability is paramount: We should prefer updating software as long as we can prove that it doesn't compromise security requirements. We should prioritize simple and reliable code, even at the cost of reasonable performance impact; we aim to create the simplest system that can perform updates correctly, securely, and that meets other performance requirements. We should bias towards designs that fail safely, and allow another chance at an update, rather than possibly corrupting state for another attempt.
  7. Product owners decide policy for their products : The platform defines what software update policies are expressible and recommends initial policy. The product owner can choose their configuration of policies, and change their policy choices at any time, even when devices are in the field.
  8. All software is verified against an intentional policy: All software is checked against a policy defined for that type of software. These policies could include provenance checking for executable code, integrity checking, sandboxing, etc. No software can be run without a predefined policy regime under which to run it.
  9. Software source policy is a product concern
    1. The platform does not restrict who can publish software, or what approvals are required. Centralized vs. decentralized software sources are a product policy, not a platform policy. As long as software is published with appropriate metadata like a publisher signature, the platform should be capable of running it.
    2. The platform will create mechanisms for enforcing software policy, but the decision of what software sources are available is up to product owners. Product owners can restrict available software sources through policy, but the platform will not.
    3. The platform should be capable of producing products that can install arbitrary software, including the ability for a user to allow software from arbitrary publishers to run on their device.

Implementation

We'll link to this RFC from the Software Delivery documentation, and keep it in mind during design processes for the Software Delivery area.

Performance

No performance impact.

Security considerations

The implementation of this RFC has no immediate security impact. Long term, we expect substantial collaboration with the security team as we execute on these goals, as the SWD update mechanism is our primary method to secure vulnerabilities in the field.

Privacy considerations

The implementation of this RFC has no privacy impact. Long term, we expect substantial collaboration with the privacy team as we execute on these goals.

Testing

The implementation of this RFC has no testing impact.

Documentation

We'll link to this RFC from Software Delivery README.

Drawbacks, alternatives, and unknowns

There are nearly limitless goals we could set for the Software Delivery area. These are the goals we feel represent both the current state of the stack and our desired state most accurately.

There are many unknowns, for instance how we'll integrate with any possible third party publishers of software. Once we have customer requirements for possible features, we'll be better able to reason about those unknowns.

Prior art and references

Very little has previously been published about the SWD roadmap. However, many previous iterations of package management and software supply chain security exist. Here is a selection of prior art: