Use environments to protect CI (#796)

Author: Murderlon

.github/workflows/ci.yml

@@ -1,49 +1,81 @@
 name: CI
-# SECURITY NOTE: This workflow uses pull_request_target which has access to secrets.
-# This is needed because tests require access to external services with credentials.
-# `pull_request_target` will always run without manual approval, even if "Require approval for all external contributors" is enabled in the repo settings.
-# Therefore we implement a "safe to test" label that must be manually added once we have checked that the diff is safe.
-# For PRs from forks, secrets are only provided when the "safe to test" label is present.
-# This allows maintainers to safely test external contributions while preventing
-# malicious actors from accessing secrets.
+# SECURITY: Uses environment protection for external PRs instead of unsafe "safe to test" labels.
+# Environment protection provides secure manual approval tied to specific commits,
+# eliminating race conditions and ensuring maintainer review before secrets access.
 on:
   push:
     branches: [main]
     paths-ignore:
       - "**.md"
       - ".changeset/**"
   pull_request_target:
-    types: [opened, synchronize, reopened, labeled]
+    types: [opened, synchronize, reopened]
     paths-ignore:
       - "**.md"
       - ".changeset/**"
   pull_request:
     types: [opened, synchronize, reopened]
-    paths:
-      - .github/workflows/ci.yml
+    paths-ignore:
+      - "**.md"
+      - ".changeset/**"
 
-concurrency: ${{ github.workflow }}--${{ github.ref }}
+concurrency:
+  group: ${{ github.workflow }}--${{ github.event_name == 'pull_request_target' && format('pr#{0}', github.event.pull_request.number) || github.ref }}
+  cancel-in-progress: true
 
 permissions:
-  pull-requests: write
+  contents: read
+  pull-requests: read
 
 jobs:
-  main:
-    name: Node.js 20
+  # Basic validation job - runs for all PRs without secrets
+  basic-validation:
+    name: Build and lint
     runs-on: ubuntu-latest
-    # Only run tests with secrets if:
-    # 1. This is a push to main, OR
-    # 2. PR is from the same repository (trusted), OR
-    # 3. PR has the "safe to test" label (maintainer approved)
+    if: github.event_name == 'pull_request'
+
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+
+      - name: Install Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 20.x
+          cache: npm
+          cache-dependency-path: package-lock.json
+
+      - name: Install dependencies
+        run: npm ci --no-fund --no-audit
+
+      - name: Build
+        run: npm run build
+
+      - name: Check formatting
+        run: npm run format:check
+
+      - name: Run linters
+        run: npm run lint
+
+  # Integration tests with secrets - requires approval for external PRs
+  tests:
+    name: Tests
+    runs-on: ubuntu-latest
+    # SECURITY: Use environment protection for external contributors
+    environment: ${{ github.event.pull_request.head.repo.full_name != github.repository && 'external-testing' || '' }}
+    # Run tests with secrets for:
+    # 1. Push to main (trusted), OR
+    # 2. PR from same repository (trusted)
+    # For external PRs: environment protection requires manual approval
     if: |
-      github.event_name == 'push' || 
-      github.event.pull_request.head.repo.full_name == github.repository ||
-      contains(github.event.pull_request.labels.*.name, 'safe to test')
+      github.event_name == 'push' ||
+      (github.event.pull_request.head.repo.full_name == github.repository)
 
     steps:
       - name: Checkout sources
         uses: actions/checkout@v4
         with:
+          # Environment protection provides security - we can safely checkout PR code
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
 
       - name: Decrypt keyfile
@@ -52,22 +84,18 @@ jobs:
           KEYFILE_PASSPHRASE: ${{secrets.KEYFILE_PASSPHRASE}}
 
       - name: Install Node.js
-        uses: actions/setup-node@v3
+        uses: actions/setup-node@v4
         with:
-          node-version: 20.19
+          node-version: 20.x
+          cache: npm
+          cache-dependency-path: package-lock.json
 
       - name: Install dependencies
         run: npm ci --no-fund --no-audit
 
       - name: Build
         run: npm run build
 
-      - name: Check formatting
-        run: npm run format:check
-
-      - name: Run linters
-        run: npm run lint
-
       - name: Run tests
         run: npm run test
         env: