fix(ci): gate secret-bearing Claude workflows by author association (fixes #218) (#547)

The Claude automation workflows (claude-issues.yml, claude-review.yml)
trigger on public, attacker-controllable events (issues, issue_comment,
pull_request_review_comment) and grant the job secrets.ANTHROPIC_API_KEY
plus a write-scoped GITHUB_TOKEN with NO author-association gate.

Because issues / issue_comment / pull_request_review_comment always run in
the base-repo context with full secret access (unlike fork pull_request,
from which GitHub withholds secrets), any external GitHub user could fire
these jobs — draining the API budget and, via contents:write +
pull-requests:write, creating branches/PRs.

Fix:
- Add an author-association gate to every human-triggered, secret-bearing
  if: clause, restricting to OWNER / MEMBER / COLLABORATOR. Uses the correct
  event payload field per trigger: github.event.issue.author_association for
  the `issues` event, github.event.comment.author_association for
  issue_comment and pull_request_review_comment. workflow_dispatch stays
  trusted (requires repo write to invoke).
- Drop unused id-token: write from both workflows (claude-code-action@v1 is
  passed github_token directly, so OIDC is unused).
- Reduce claude-issues.yml timeout-minutes 60 -> 15.

desktop.yml and take-assign.yml are intentionally NOT touched: independently
verified as not exploitable for ANTHROPIC_API_KEY (desktop.yml's only
pull_request job uses no secrets and the trigger is plain pull_request, not
pull_request_target; take-assign.yml uses only GITHUB_TOKEN with issues:write
and no checkout/no Anthropic key). claude-review.yml's stale pull_request
auto-trigger was already removed in 3f2f46e4.

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/claude-issues.yml

@@ -11,22 +11,33 @@ concurrency:
   group: claude-issues-${{ github.event.issue.number || github.run_id }}
   cancel-in-progress: true
 
+# Least-privilege: only what the issue-fixer job actually needs.
+# id-token (OIDC) is intentionally omitted — claude-code-action@v1 is passed
+# github_token directly, so OIDC is unused here.
 permissions:
   contents: write
   pull-requests: write
   issues: write
-  id-token: write
 
 jobs:
   fix:
     runs-on: ubuntu-latest
-    timeout-minutes: 60
+    timeout-minutes: 15
+    # Security gate: this job reaches secrets.ANTHROPIC_API_KEY and holds a
+    # write-scoped GITHUB_TOKEN. `issues` / `issue_comment` are public,
+    # attacker-controllable events that run in the base-repo context with full
+    # secret access, so the human-triggered paths are restricted to actors with
+    # write-level association (OWNER / MEMBER / COLLABORATOR). This blocks
+    # external / first-time contributors from draining the API budget or
+    # creating branches/PRs, while leaving maintainer use unaffected.
     if: |
       github.event_name == 'workflow_dispatch' ||
       (github.event_name == 'issues' &&
+       contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'), github.event.issue.author_association) &&
        (contains(github.event.issue.labels.*.name, 'bug') ||
         contains(github.event.issue.labels.*.name, 'autofix'))) ||
       (github.event_name == 'issue_comment' &&
+       contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'), github.event.comment.author_association) &&
        !github.event.issue.pull_request &&
        contains(github.event.comment.body, '@claude') &&
        github.actor != 'claude[bot]')

.github/workflows/claude-review.yml

@@ -11,23 +11,33 @@ concurrency:
   group: claude-review-${{ github.event.pull_request.number || github.event.issue.number || github.run_id }}
   cancel-in-progress: true
 
+# Least-privilege: PR review only needs to post comments on the PR.
+# id-token (OIDC) is omitted — claude-code-action@v1 is passed github_token
+# directly, so OIDC is unused here.
 permissions:
   contents: read
   pull-requests: write
   issues: write
-  id-token: write
 
 jobs:
   review:
     runs-on: ubuntu-latest
     timeout-minutes: 30
+    # Security gate: this job reaches secrets.ANTHROPIC_API_KEY. Both
+    # issue_comment and pull_request_review_comment are public,
+    # attacker-controllable events that run in the base-repo context with full
+    # secret access, so the @claude paths are restricted to actors with
+    # write-level association (OWNER / MEMBER / COLLABORATOR). External /
+    # first-time contributors cannot trigger the key; maintainers are unaffected.
     if: |
       github.event_name == 'workflow_dispatch' ||
       (github.event_name == 'issue_comment' &&
+       contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'), github.event.comment.author_association) &&
        github.event.issue.pull_request &&
        contains(github.event.comment.body, '@claude') &&
        github.actor != 'claude[bot]') ||
       (github.event_name == 'pull_request_review_comment' &&
+       contains(fromJSON('["OWNER", "MEMBER", "COLLABORATOR"]'), github.event.comment.author_association) &&
        contains(github.event.comment.body, '@claude') &&
        github.actor != 'claude[bot]')
     steps: