Add Squid proxy network restrictions for claude-code-action (#259)

* feat: add Squid proxy network restrictions to Claude workflow

Implements URL whitelisting for GitHub Actions to prevent unauthorized network access.
Only allows connections to:
- Claude API (anthropic.com)
- GitHub services
- Package registries (npm, bun)
- Azure blob storage for caching

Uses NO_PROXY for package registries to avoid integrity check issues.

* test: add network restrictions verification test

* test: simplify network restrictions test output

* refactor: make network restrictions opt-in and move to examples

- Removed network restrictions from .github/workflows/claude.yml
- Added network restrictions to examples/claude.yml as opt-in feature
- Changed from DISABLE_NETWORK_RESTRICTIONS to ENABLE_NETWORK_RESTRICTIONS
- Added support for CUSTOM_ALLOWED_DOMAINS repository variable
- Organized whitelist by provider (Anthropic, Bedrock, Vertex AI)
- Removed package registries from whitelist (already in NO_PROXY)

Users can now enable network restrictions by setting ENABLE_NETWORK_RESTRICTIONS=true
and configure additional domains via CUSTOM_ALLOWED_DOMAINS.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Minor bun format

* test: simplify network restrictions test

- Reduce to one allowed and one blocked domain
- Remove slow google.com test
- Fix TypeScript errors with AbortController
- Match test formatting conventions

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

* Move network restrictions to actions.yml + show custom domains in the examples folder

* Simplify network restrictions -- Move it to actions, remove extended examples in claude.yml and move them to readme

* Remove unnecessary network restrictions test and update readme + action.yml with no default domains and respective instructions in the readme

* Update README with common domains

* Give an example of network restriction in claude.yml

* Remove unnecesssary NO_PROXY as packages are installed beforehand

* Remove proxy example -- it's intuitive for users to figure it out

* Update potential EOF not being treated as a string issue

* update claude.yml to test

* Update example allowed_domains with tested domains for network restrictions

* change to experimental allowed domains and add `.blob.core.windows.net` to use cached bun isntall

* Update remaining allowed_domains references to experimental_allowed_domains

* Reset claude.yml to match origin/main

Remove network restrictions test changes from claude.yml

* Format README.md table alignment

Run bun format to fix table column alignment

---------

Co-authored-by: km-anthropic <km-anthropic@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>

README.md

@@ -166,7 +166,7 @@ jobs:
 ## Inputs
 
 | Input                          | Description                                                                                                          | Required | Default   |
-| ------------------------- | -------------------------------------------------------------------------------------------------------------------- | -------- | --------- |
+| ------------------------------ | -------------------------------------------------------------------------------------------------------------------- | -------- | --------- |
 | `anthropic_api_key`            | Anthropic API key (required for direct API, not needed for Bedrock/Vertex)                                           | No\*     | -         |
 | `claude_code_oauth_token`      | Claude Code OAuth token (alternative to anthropic_api_key)                                                           | No\*     | -         |
 | `direct_prompt`                | Direct prompt for Claude to execute automatically without needing a trigger (for automated workflows)                | No       | -         |
@@ -191,6 +191,7 @@ jobs:
 | `claude_env`                   | Custom environment variables to pass to Claude Code execution (YAML format)                                          | No       | ""        |
 | `settings`                     | Claude Code settings as JSON string or path to settings JSON file                                                    | No       | ""        |
 | `additional_permissions`       | Additional permissions to enable. Currently supports 'actions: read' for viewing workflow results                    | No       | ""        |
+| `experimental_allowed_domains` | Restrict network access to these domains only (newline-separated).                                                   | No       | ""        |
 | `use_commit_signing`           | Enable commit signing using GitHub's commit signature verification. When false, Claude uses standard git commands    | No       | `false`   |
 
 \*Required when using direct Anthropic API (default and when not using Bedrock or Vertex)
@@ -573,6 +574,71 @@ Use a specific Claude model:
     # ... other inputs
 ```
 
+### Network Restrictions
+
+For enhanced security, you can restrict Claude's network access to specific domains only. This feature is particularly useful for:
+
+- Enterprise environments with strict security policies
+- Preventing access to external services
+- Limiting Claude to only your internal APIs and services
+
+When `experimental_allowed_domains` is set, Claude can only access the domains you explicitly list. You'll need to include the appropriate provider domains based on your authentication method.
+
+#### Provider-Specific Examples
+
+##### If using Anthropic API or subscription
+
+```yaml
+- uses: anthropics/claude-code-action@beta
+  with:
+    anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+    # Or: claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}
+    experimental_allowed_domains: |
+      .anthropic.com
+```
+
+##### If using AWS Bedrock
+
+```yaml
+- uses: anthropics/claude-code-action@beta
+  with:
+    use_bedrock: "true"
+    experimental_allowed_domains: |
+      bedrock.*.amazonaws.com
+      bedrock-runtime.*.amazonaws.com
+```
+
+##### If using Google Vertex AI
+
+```yaml
+- uses: anthropics/claude-code-action@beta
+  with:
+    use_vertex: "true"
+    experimental_allowed_domains: |
+      *.googleapis.com
+      vertexai.googleapis.com
+```
+
+#### Common GitHub Domains
+
+In addition to your provider domains, you may need to include GitHub-related domains. For GitHub.com users, common domains include:
+
+```yaml
+- uses: anthropics/claude-code-action@beta
+  with:
+    anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
+    experimental_allowed_domains: |
+      .anthropic.com  # For Anthropic API
+      .github.com
+      .githubusercontent.com
+      ghcr.io
+      .blob.core.windows.net
+```
+
+For GitHub Enterprise users, replace the GitHub.com domains above with your enterprise domains (e.g., `.github.company.com`, `packages.company.com`, etc.).
+
+To determine which domains your workflow needs, you can temporarily run without restrictions and monitor the network requests, or check your GitHub Enterprise configuration for the specific services you use.
+
 ### Claude Code Settings
 
 You can provide Claude Code settings to customize behavior such as model selection, environment variables, permissions, and hooks. Settings can be provided either as a JSON string or a path to a settings file.

action.yml

@@ -100,6 +100,10 @@ inputs:
     description: "Enable commit signing using GitHub's commit signature verification. When false, Claude uses standard git commands"
     required: false
     default: "false"
+  experimental_allowed_domains:
+    description: "Restrict network access to these domains only (newline-separated). If not set, no restrictions are applied. Provider domains are auto-detected."
+    required: false
+    default: ""
 
 outputs:
   execution_file:
@@ -146,6 +150,38 @@ runs:
         ADDITIONAL_PERMISSIONS: ${{ inputs.additional_permissions }}
         USE_COMMIT_SIGNING: ${{ inputs.use_commit_signing }}
 
+    - name: Setup Network Restrictions
+      if: steps.prepare.outputs.contains_trigger == 'true' && inputs.experimental_allowed_domains != ''
+      shell: bash
+      run: |
+        # Install and configure Squid proxy
+        sudo apt-get update && sudo apt-get install -y squid
+
+        echo "${{ inputs.experimental_allowed_domains }}" > $RUNNER_TEMP/whitelist.txt
+
+        # Configure Squid
+        sudo tee /etc/squid/squid.conf << EOF
+        http_port 127.0.0.1:3128
+        acl whitelist dstdomain "$RUNNER_TEMP/whitelist.txt"
+        acl localhost src 127.0.0.1/32
+        http_access allow localhost whitelist
+        http_access deny all
+        cache deny all
+        EOF
+
+        # Stop any existing squid instance and start with our config
+        sudo squid -k shutdown || true
+        sleep 2
+        sudo rm -f /run/squid.pid
+        sudo squid -N -d 1 &
+        sleep 5
+
+        # Set proxy environment variables
+        echo "http_proxy=http://127.0.0.1:3128" >> $GITHUB_ENV
+        echo "https_proxy=http://127.0.0.1:3128" >> $GITHUB_ENV
+        echo "HTTP_PROXY=http://127.0.0.1:3128" >> $GITHUB_ENV
+        echo "HTTPS_PROXY=http://127.0.0.1:3128" >> $GITHUB_ENV
+
     - name: Run Claude Code
       id: claude-code
       if: steps.prepare.outputs.contains_trigger == 'true'

examples/claude.yml

@@ -36,3 +36,12 @@ jobs:
           # Or use OAuth token instead:
           # claude_code_oauth_token: ${{ secrets.CLAUDE_CODE_OAUTH_TOKEN }}
           timeout_minutes: "60"
+          # Optional: Restrict network access to specific domains only
+          # experimental_allowed_domains: |
+          #   .anthropic.com
+          #   .github.com
+          #   api.github.com
+          #   .githubusercontent.com
+          #   bun.sh
+          #   registry.npmjs.org
+          #   .blob.core.windows.net