Contrib: Add process for security responses.

src/doc/contrib/src/SUMMARY.md

@@ -7,6 +7,7 @@
     - [Working on Cargo](./process/working-on-cargo.md)
     - [Release process](./process/release.md)
     - [Unstable features](./process/unstable.md)
+    - [Security issues](./process/security.md)
 - [Design Principles](./design.md)
 - [Implementing a Change](./implementation/index.md)
     - [Architecture](./implementation/architecture.md)

src/doc/contrib/src/process/security.md

@@ -0,0 +1,136 @@
+# Security issues
+
+Issues involving reporting a security vulnerability in cargo usually start by following the [Rust security policy].
+The Security Response Working Group ("the WG") is responsible for running the process of handling the response to a security issue.
+Their process is documented at [Handling Reports].
+This document gives an overview of the process from a Cargo team member's perspective.
+
+The general order of events happens as follows:
+
+1. The "reporter" (even if it is a Cargo team member) reports an issue to <[email protected]>.
+1. The WG will evaluate if the report is credible, and manages responses to the reporter.
+1. The WG will start a private Zulip stream to coordinate discussion and plans for a fix.
+1. The WG will pull in one or more team members into the Zulip stream ("responders").
+    - Security vulnerabilities are **embargoed** until they are released publicly.
+      People who are brought into these discussions should **not** discuss the issue with *anyone* outside of the group, or with your employer, without first consulting The WG.
+1. A discussion then starts to evaluate the severity of the issue and what possible solutions should be considered.
+   This includes figuring out who will volunteer to actually develop the patches to resolve the issue, and who will review it.
+1. The WG will create a temporary private fork of the `rust-lang/cargo` repo using GitHub's [repository security advisory][github-advisory] system.
+   This provides a space where changes can be securely posted, and the security advisory can be drafted.
+   See ["Collaborating in a temporary private fork"][private-fork] for some screenshots of what this looks like.
+   GitHub includes instructions on how to work with the fork.
+
+   Beware that the private fork has some limitations, such as not supporting CI, or (for some weird reason) not supporting syntax highlighting.
+1. Someone will need to review the patches and make sure everyone agrees on the solution.
+   This may also involve the WG conferring with the reporter to validate the fix.
+1. Create a rollout plan.
+   This includes deciding if there will be a new patch release of Rust, or if it should wait for the next stable release, or whether to remove the embargo on the fix.
+1. The WG will handle drafting a Security Advisory using GitHub's Security Advisory ("GHSA") system.
+   [GHSA-r5w3-xm58-jv6j] is an example of what this looks like.
+   This process also involves reserving a [CVE](https://www.cve.org/) number, where the report will eventually be posted.
+
+   The responders should carefully review the report to make sure it is correct.
+
+   This process may also involve deciding on the CVSS score.
+   There are a bunch of calculators on the web where you can see how this works (such as the [FIRST CVSS Calculator][calc], or you can view GitHub's calculator by drafting a security advisory in one of your personal repos).
+   FIRST has a [user guide][first-guide] for deciding how to score each characteristic.
+1. If it is decided to do a patch release of Rust, the general overview of steps is:
+    1. Finalizing the patches.
+       This includes all the little details like updating changelogs, version numbers, and such.
+    1. Preparing PRs in the private fork against the stable, beta, and nightly (master) branches.
+    1. The WG handles creating a private fork of `rust-lang/rust` to prepare the point release.
+       This usually includes changes for stable, beta, and nightly.
+    1. The WG handles posting patches in various places (such as mailing lists), possibly several days in advance.
+    1. The WG handles posting public PRs to `rust-lang/rust` to incorporate the fix and prepare a new release.
+    1. The WG handles announcing everything, including publishing the GHSA, publishing a blog post, and several other places.
+
+## External dependency patches
+
+Sometimes it may be necessary to make changes to external dependencies to support a fix.
+This can make things complicated.
+If the change is by itself benign and not directly related to the security issue,
+then it may be safe to publicly propose the change (but not giving context) and try to get a new release of the dependency made (though confer with the WG first!).
+However, if the issue is directly related to the dependency, then it becomes significantly more awkward.
+
+The general process for [GHSA-r5w3-xm58-jv6j] which involved a fix in `git2-rs` was handled by the responders because it is a dependency owned by the rust-lang org.
+The general outline of how we managed this is:
+
+- Pre-release:
+    1. Created a private fork of `rust-lang/git2-rs` just like we did for `rust-lang/cargo`.
+       git2-rs also had its own Security Advisory just like cargo did.
+    1. Created and reviewed PRs in the private fork for the fixes.
+        - The PRs in the `rust-lang/cargo` private fork had to have a temporary `[patch]` git dependency on the `git2-rs` private fork.
+    1. Before the release, the PRs were changed to remove the `[patch]`, and pretend as-if git2-rs had already been published.
+- Showtime:
+    1. The git2-rs changes were publicly merged, and a new release was published to crates.io.
+    1. The cargo PR was merged to cargo's stable branch.
+    1. The private rust-lang/rust PR updated the cargo submodule and updated `Cargo.lock` to pick up the new git2 dependencies.
+    1. Release proceeds as normal (publish both GHSA, create release, etc.).
+- Post-release:
+    1. Various forward ports were created in git2-rs, and new releases were made.
+
+If the change is in a crate not managed by any responder, then confer with the WG on a strategy.
+One option is to create a temporary fork used for the security response that will be removed as soon as the security advisory is released and a new public release of the dependency is made with the fix.
+
+## Checklist
+
+There are a lot of details to handle, and it can be a bit of a challenge under time pressure.
+The following is a checklist of some items to pay attention to during the process.
+
+Pre-release:
+- [ ] Check for any SemVer-incompatible changes in the public API of any crates that are modified.
+  - Try to avoid these if at all possible.
+    Although not a severe problem, making Cargo's version number drift farther from Rust's can contribute to confusion.
+  - If a SemVer-breaking release is made to a dependency, make sure this is coordinated correctly between the stable, beta, and master branches.
+- [ ] With a checkout of the proposed fixes, run as much of cargo's CI testsuite locally as you can.
+  Since private forks don't support CI, the responders will be responsible for making sure all tests pass.
+  Enlist other responders if you don't have the necessary systems like Windows.
+- [ ] Manually exercise the fix locally.
+  Since we will essentially have *no* nightly testing, the responders are responsible for making sure things work.
+  Try to consider all the different environments users may be using.
+- [ ] Make sure any comments or docs that need updating get updated.
+- [ ] Review the git commit messages of the patch.
+  Make sure they clearly and accurately reflect what is being changed and why.
+  Clean up the commit history if it goes through several revisions during review.
+- [ ] Make sure that the *public* cargo repo's stable and beta branches are in a state where they are passing CI.
+  This may require backporting changes that fix problems that have already been fixed in master.
+  This can be done publicly at any time, and helps with ensuring a smooth process once the security issue is released.
+  (The WG may disable branch protections to push directly to the stable branch, but this step is still useful to assist with local testing and the beta branch.)
+- [ ] After the fix is approved, create backports to the stable and beta master branches and post PRs to the private fork.
+- [ ] If any internal dependencies are changed, make sure their versions are bumped appropriately, and dependency specifications are updated (stable, beta, and master branches).
+- [ ] Thoroughly test the stable and beta PRs locally, too. We want to make sure everything goes smoothly, and we can't assume that just because a patch applied cleanly that there won't be issues.
+- [ ] Make sure cargo's version in [`Cargo.toml`] is updated correctly on the stable branch private PR.
+- [ ] Make sure cargo's `Cargo.lock` is updated (stable, beta, master branches).
+- [ ] Update [`CHANGELOG.md`] on cargo's master branch private PR.
+- [ ] Update [`RELEASES.md`] on rust's master branch private PR (and stable and beta?).
+- [ ] Remove any temporary things in the patch, like a temporary `[patch]` table.
+
+Showtime:
+- [ ] Publish any embargoed external dependencies to crates.io.
+- [ ] (WG) Merge the cargo stable change.
+- [ ] (WG) Update the cargo submodule in the rust-lang/rust private PR to point to the new stable commit.
+    - [ ] Also update `Cargo.lock`.
+- [ ] (WG) Make a new stable release.
+- [ ] (WG) Publish the GHSA.
+- [ ] (WG) Send announcements.
+- [ ] Make sure stable, beta, and master branches of `rust-lang/cargo` get updated.
+- [ ] Make sure stable, beta, and master branches of `rust-lang/rust` get updated, pointing to the correct submodule versions.
+- [ ] If any external dependencies are updated, make sure their back or forward ports are handled.
+
+Post release:
+- [ ] Verify that the appropriate crates are published on crates.io.
+- [ ] Verify that `rust-lang/cargo` got a new tag.
+- [ ] Verify that the patches were backported to the correct branches in the `rust-lang/cargo` repository (stable, beta, and master).
+- [ ] Verify that the cargo submodule is updated on the correct branches in the `rust-lang/rust` repository (stable, beta, and master).
+- [ ] Follow up on any non-critical tasks that were identified during review.
+
+[Rust security policy]: https://www.rust-lang.org/policies/security
+[github-advisory]: https://docs.github.com/en/code-security/security-advisories/repository-security-advisories
+[private-fork]: https://docs.github.com/en/code-security/security-advisories/repository-security-advisories/collaborating-in-a-temporary-private-fork-to-resolve-a-repository-security-vulnerability
+[calc]: https://www.first.org/cvss/calculator
+[GHSA-r5w3-xm58-jv6j]: https://github.com/rust-lang/cargo/security/advisories/GHSA-r5w3-xm58-jv6j
+[handling reports]: https://github.com/rust-lang/wg-security-response/blob/main/docs/handling-reports.md
+[first-guide]: https://www.first.org/cvss/user-guide
+[`CHANGELOG.md`]: https://github.com/rust-lang/cargo/blob/master/CHANGELOG.md
+[`Cargo.toml`]: https://github.com/rust-lang/cargo/blob/master/Cargo.toml
+[`RELEASES.md`]: https://github.com/rust-lang/rust/blob/master/RELEASES.md