Pin actions to digests and introduce Step Security Harden Runners (#137)

Signed-off-by: Jed Salazar <jedsalazar@gmail.com>

.github/workflows/os.yml

@@ -23,17 +23,21 @@ jobs:
       TARGET_ARCH: "${{ matrix.arch }}"
     name: os build ${{ matrix.arch }}
     steps:
-    - uses: actions/checkout@v4
+    - name: Harden Runner
+      uses: step-security/harden-runner@a4aa98b93cab29d9b1101a6143fb8bce00e2eac4 # v2.7.1
+      with:
+        egress-policy: audit
+    - uses: actions/checkout@0ad4b8fadaa221de15dcec353f45205ec38ea70b # v4.1.4
       with:
         submodules: recursive
-    - uses: dtolnay/rust-toolchain@stable
+    - uses: dtolnay/rust-toolchain@d388a4836fcdbde0e50e395dc79a2670ccdef13f # stable
       with:
         targets: "${{ matrix.arch }}-unknown-linux-gnu,${{ matrix.arch }}-unknown-linux-musl"
     - run: ./hack/ci/install-linux-deps.sh
     - run: ./hack/os/build.sh
       env:
         KRATA_KERNEL_BUILD_JOBS: "5"
-    - uses: actions/upload-artifact@v4
+    - uses: actions/upload-artifact@65462800fd760344b1a7b4382951275a0abb4808 # v4.3.3
       with:
         name: krata-os-${{ matrix.arch }}
         path: "target/os/krata-${{ matrix.arch }}.qcow2"