ci: add minimum GitHub token permissions for workflows

.github/workflows/check_diff.yml

@@ -15,6 +15,9 @@ on:
         description: 'Optional comma separated list of rustfmt config options to pass when running the feature branch'
         required: false
 
+permissions:
+  contents: read
+
 jobs:
   diff_check:
     runs-on: ubuntu-latest

.github/workflows/integration.yml

@@ -5,6 +5,9 @@ on:
       - master
   pull_request:
 
+permissions:
+  contents: read
+
 jobs:
   integration-tests:
     runs-on: ubuntu-latest

.github/workflows/linux.yml

@@ -5,6 +5,9 @@ on:
       - master
   pull_request:
 
+permissions:
+  contents: read
+
 jobs:
   test:
     runs-on: ubuntu-latest

.github/workflows/mac.yml

@@ -5,6 +5,9 @@ on:
       - master
   pull_request:
 
+permissions:
+  contents: read
+
 jobs:
   test:
     # https://help.github.com/en/actions/automating-your-workflow-with-github-actions/virtual-environments-for-github-hosted-runners#supported-runners-and-hardware-resources

.github/workflows/rustdoc_check.yml

@@ -5,6 +5,9 @@ on:
       - master
   pull_request:
 
+permissions:
+  contents: read
+
 jobs:
   rustdoc_check:
     runs-on: ubuntu-latest

.github/workflows/upload-assets.yml

@@ -6,8 +6,13 @@ on:
     types: [created]
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   build-release:
+    permissions:
+      contents: write  # for actions/upload-release-asset to upload release asset
     name: build-release
     strategy:
       matrix:

.github/workflows/windows.yml

@@ -5,6 +5,9 @@ on:
       - master
   pull_request:
 
+permissions:
+  contents: read
+
 jobs:
   test:
     runs-on: windows-latest