GitHub Workflows security hardening (#2923)

.github/workflows/bench.yml

@@ -5,6 +5,9 @@ on:
     branches:
       - master
 
+permissions:
+  contents: read  #  to fetch code (actions/checkout)
+
 jobs:
   check_benchmark:
     runs-on: ubuntu-latest

.github/workflows/ci-post-merge.yml

@@ -4,6 +4,9 @@ on:
   push:
     branches: [master]
 
+permissions:
+  contents: read  #  to fetch code (actions/checkout)
+
 jobs:
   build_and_test_nightly:
     strategy:

.github/workflows/ci.yml

@@ -6,6 +6,9 @@ on:
   push:
     branches: [master]
 
+permissions:
+  contents: read  #  to fetch code (actions/checkout)
+
 jobs:
   build_and_test:
     strategy:

.github/workflows/upload-doc.yml

@@ -4,8 +4,12 @@ on:
   push:
     branches: [master]
 
+permissions: {}
 jobs:
   build:
+    permissions:
+      contents: write  #  to push changes in repo (jamesives/github-pages-deploy-action)
+
     runs-on: ubuntu-latest
 
     steps: