[StepSecurity] ci: Harden GitHub Actions

.github/workflows/gradle-wrapper-validation.yml

@@ -7,6 +7,9 @@ on:
     paths:
       - '**/gradle/wrapper/**'
 
+permissions:
+  contents: read
+
 jobs:
   validation:
     runs-on: ubuntu-latest

.github/workflows/prepare-release-branch.yml

@@ -2,6 +2,9 @@ name: Prepare release branch
 on:
   workflow_dispatch:
 
+permissions:
+  contents: read
+
 jobs:
   prereqs:
     runs-on: ubuntu-latest
@@ -21,6 +24,8 @@ jobs:
           fi
 
   create-pull-request-against-release-branch:
+    permissions:
+      contents: write  # for Git to git push
     runs-on: ubuntu-latest
     needs:
       - prereqs
@@ -74,6 +79,8 @@ jobs:
                        --base $RELEASE_BRANCH_NAME
 
   create-pull-request-against-main:
+    permissions:
+      contents: write  # for Git to git push
     runs-on: ubuntu-latest
     needs:
       - prereqs

.github/workflows/reusable-markdown-link-check.yml

@@ -3,6 +3,9 @@ name: Reusable - Markdown link check
 on:
   workflow_call:
 
+permissions:
+  contents: read
+
 jobs:
   markdown-link-check:
     runs-on: ubuntu-latest

.github/workflows/reusable-misspell-check.yml

@@ -3,6 +3,9 @@ name: Reusable - Misspell check
 on:
   workflow_call:
 
+permissions:
+  contents: read
+
 jobs:
   misspell-check:
     runs-on: ubuntu-latest