feat(security): harden gateway boundaries and usage policies

Consolidate subscription usage policy enforcement, privacy-safe persistence, and gateway security hardening into one reviewable change.

Includes bounded HTTP and execution envelopes, header and protocol guards, DNS and relay validation, authentication and secret projection hardening, secure backup/install paths, and regression coverage.

.github/workflows/build-tunnel.yml

@@ -6,7 +6,8 @@ on:
   workflow_dispatch:
 
 permissions:
-  contents: write
+  actions: read
+  contents: read
 
 concurrency:
   group: build-tunnel-${{ github.ref }}
@@ -17,7 +18,7 @@ jobs:
     runs-on: ubuntu-latest
     if: startsWith(github.ref, 'refs/tags/')
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
 
       - name: Ensure tunnel tag matches Cargo version
         shell: bash
@@ -78,10 +79,10 @@ jobs:
             use_cross: false
 
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
 
       - name: Install Rust toolchain
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/rust-toolchain@4360b52568e2003a75bf9bc1d59f33a8e3fc893c # stable
         with:
           targets: ${{ matrix.target }}
 
@@ -89,14 +90,14 @@ jobs:
         run: rustup target add ${{ matrix.target }}
 
       - name: Rust cache
-        uses: Swatinem/rust-cache@v2
+        uses: Swatinem/rust-cache@49a0bdc70d2e1b713ca9e2869b211fcce03d3c1c # v2
         with:
           workspaces: apps/aether-tunnel -> target
           key: ${{ matrix.target }}
 
       - name: Install cross
         if: matrix.use_cross
-        uses: taiki-e/install-action@cross
+        uses: taiki-e/install-action@1ae7257be536a92d9218a6b343dc6e6ba650f7e1 # cross
 
       - name: Build
         working-directory: apps/aether-tunnel
@@ -122,9 +123,10 @@ jobs:
         run: |
           cd target/${{ matrix.target }}/release
           7z a ../../../aether-tunnel-${{ matrix.name }}.zip aether-tunnel.exe
+          tar czf ../../../aether-tunnel-${{ matrix.name }}.tar.gz aether-tunnel.exe
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v5
+        uses: actions/upload-artifact@330a01c490aca151604b8cf639adc76d48f6c5d4 # v5
         with:
           name: aether-tunnel-${{ matrix.name }}
           path: |
@@ -137,9 +139,14 @@ jobs:
     needs: build
     runs-on: ubuntu-latest
     if: startsWith(github.ref, 'refs/tags/')
+    permissions:
+      actions: read
+      attestations: write
+      contents: write
+      id-token: write
     steps:
       - name: Download all artifacts
-        uses: actions/download-artifact@v5
+        uses: actions/download-artifact@634f93cb2916e3fdff6788551b99b062d0335ce0 # v5
         with:
           merge-multiple: true
           path: artifacts
@@ -148,6 +155,20 @@ jobs:
         working-directory: artifacts
         run: sha256sum aether-tunnel-* > SHA256SUMS.txt
 
+      - name: Attest tunnel release provenance
+        id: attest-release
+        uses: actions/attest@1e69f48acb82d1966a394da916b4c1698aa569d6 # v4.2.2
+        with:
+          subject-path: |
+            artifacts/aether-tunnel-*.tar.gz
+            artifacts/aether-tunnel-*.zip
+            artifacts/SHA256SUMS.txt
+
+      - name: Bundle tunnel release provenance
+        env:
+          ATTESTATION_BUNDLE: ${{ steps.attest-release.outputs.bundle-path }}
+        run: install -m 0644 "${ATTESTATION_BUNDLE}" artifacts/AETHER_TUNNEL_RELEASE_PROVENANCE.sigstore.json
+
       - name: Delete stale draft releases for tag
         env:
           GH_TOKEN: ${{ github.token }}
@@ -170,12 +191,13 @@ jobs:
           done <<< "${draft_ids}"
 
       - name: Create GitHub Release
-        uses: softprops/action-gh-release@v2
+        uses: softprops/action-gh-release@3bb12739c298aeb8a4eeaf626c5b8d85266b0e65 # v2
         with:
           name: "${{ github.ref_name }}"
           generate_release_notes: true
           files: |
             artifacts/aether-tunnel-*
+            artifacts/AETHER_TUNNEL_RELEASE_PROVENANCE.sigstore.json
             artifacts/SHA256SUMS.txt
           fail_on_unmatched_files: true
 
@@ -183,8 +205,10 @@ jobs:
     needs: release
     runs-on: ubuntu-latest
     if: startsWith(github.ref, 'refs/tags/')
+    permissions:
+      contents: write
     steps:
-      - uses: actions/checkout@v5
+      - uses: actions/checkout@fbc6f3992d24b796d5a048ff273f7fcc4a7b6c09 # v5
         with:
           ref: main