ci: github actions hardening (#190)

Restrict permissions of github token. Pin action versions.

Following advice in briansmith/untrusted#50.

.github/workflows/ci.yml

@@ -1,3 +1,8 @@
+name: ci
+
+permissions:
+  contents: read
+
 on:
   push:
     branches:
@@ -6,7 +11,6 @@ on:
   schedule:
     - cron: '17 12 * * 6'
 
-name: ci
 jobs:
   test:
     strategy:
@@ -16,7 +20,7 @@ jobs:
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Install Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
       with:
         go-version: ${{ matrix.go-version }}
     - name: Configure Go Environment
@@ -26,7 +30,9 @@ jobs:
     - name: Go Environment
       run: go env
     - name: Checkout code
-      uses: actions/checkout@v1
+      uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+      with:
+        persist-credentials: false
     - name: Bootstrap
       run: ./script/bootstrap
 
@@ -38,13 +44,13 @@ jobs:
       run: ./script/coverage
 
     - name: Upload Unit Test Coverage
-      uses: codecov/codecov-action@v1.0.5
+      uses: codecov/codecov-action@967e2b38a85a62bd61be5529ada27ebc109948c2 #v1.4.1
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         file: unittests.coverprofile
         flags: unittests
     - name: Upload Integration Test Coverage
-      uses: codecov/codecov-action@v1.0.5
+      uses: codecov/codecov-action@967e2b38a85a62bd61be5529ada27ebc109948c2 #v1.4.1
       with:
         token: ${{ secrets.CODECOV_TOKEN }}
         file: integration.coverprofile
@@ -58,7 +64,7 @@ jobs:
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Install Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
       with:
         go-version: ${{ matrix.go-version }}
     - name: Configure Go Environment
@@ -68,7 +74,9 @@ jobs:
     - name: Go Environment
       run: go env
     - name: Checkout code
-      uses: actions/checkout@v1
+      uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+      with:
+        persist-credentials: false
     - name: Bootstrap
       run: ./script/bootstrap
     - name: Lint
@@ -82,11 +90,13 @@ jobs:
     runs-on: ${{ matrix.platform }}
     steps:
     - name: Install Go
-      uses: actions/setup-go@v1
+      uses: actions/setup-go@37335c7bb261b353407cff977110895fa0b4f7d8 # v2.1.3
       with:
         go-version: ${{ matrix.go-version }}
     - name: Checkout code
-      uses: actions/checkout@v1
+      uses: actions/checkout@5a4ac9002d0be2fb38bd78e4b4dbde5606d7042f # v2.3.4
+      with:
+        persist-credentials: false
     - name: Run Third-Party Tests
       working-directory: ./tests/thirdparty
       run: go test -pkgs packages.json