security: harden CI — pin actions to SHAs, pin deps, restrict permissions

Author: NellInc

.github/workflows/ci.yml

@@ -7,6 +7,10 @@ on:
   pull_request:
     branches: [main]
 
+# Restrict default permissions to read-only (principle of least privilege)
+permissions:
+  contents: read
+
 jobs:
   test:
     runs-on: ubuntu-latest
@@ -15,10 +19,10 @@ jobs:
         python-version: ["3.10", "3.11", "3.12"]
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: ${{ matrix.python-version }}
 
@@ -38,25 +42,25 @@ jobs:
 
       - name: Upload coverage
         if: matrix.python-version == '3.11'
-        uses: codecov/codecov-action@v4
+        uses: codecov/codecov-action@b9fd7d16f6d7d1b5d2bec1a2887e65ceed900238 # v4
         with:
           file: ./coverage.xml
           fail_ci_if_error: false
 
   lint:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: "3.11"
 
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install black ruff
+          pip install black==26.3.1 ruff==0.15.9
 
       - name: Check formatting with black
         run: black --check creed_guardian
@@ -73,22 +77,22 @@ jobs:
       id-token: write
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
       - name: Set up Python
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: "3.11"
 
       - name: Install build dependencies
         run: |
           python -m pip install --upgrade pip
-          pip install build twine
+          pip install build==1.4.2 twine==6.2.0
 
       - name: Build package
         run: python -m build
 
       - name: Publish to PyPI
-        uses: pypa/gh-action-pypi-publish@release/v1
+        uses: pypa/gh-action-pypi-publish@ed0c53931b1dc9bd32cbe73a98c7f6766f8a527e # release/v1
         with:
           password: ${{ secrets.PYPI_API_TOKEN }}