HttpRecorder.DevProxy

HttpRecorder Dev Proxy Extension

This directory contains a Microsoft Dev Proxy plugin that integrates HttpRecorder to capture HTTP traffic and save it as HAR (HTTP Archive) files.

Overview

The HttpRecorder Dev Proxy plugin allows you to:

• Intercept HTTP requests and responses passing through Dev Proxy
• Record them using the HttpRecorder library
• Save interactions as HAR files for later replay or analysis
• Anonymize sensitive data like authorization headers
• Filter which URLs to record

Project Structure

DevProxyExtension/
├── HttpRecorder.DevProxy/
│   ├── HttpRecorderPlugin.cs              # Main plugin implementation
│   ├── HttpRecorderPluginConfiguration.cs # Plugin configuration class
│   ├── BasePlugin.cs                      # Base class stub (replace with DevProxy.Abstractions)
│   └── HttpRecorder.DevProxy.csproj       # Project file
├── README.md                               # This file
└── devproxyrc.example.json                # Example Dev Proxy configuration

Prerequisites

• Microsoft Dev Proxy - Install using winget (recommended):

  # Stable version
  winget install DevProxy.DevProxy --silent
  
  # OR Beta version (for latest preview features)
  winget install DevProxy.DevProxy.Beta --silent
  

  Important: After installation, restart your command prompt to refresh the PATH environment variable.

  Alternative: Manual installation from Microsoft Dev Proxy Documentation

• .NET 9.0 SDK - Required for building the plugin

First Time Setup

When you start Dev Proxy for the first time:

• Trust the certificate: Dev Proxy installs a certificate named "Dev Proxy CA". Select Yes to confirm installation.
• Allow firewall access: Windows Firewall will show a warning. Select Allow access to permit traffic through the firewall.

Dev Proxy will display:

 info    Dev Proxy API listening on http://localhost:8897...
 info    Dev Proxy Listening on 127.0.0.1:8000...

Hotkeys: issue (w)eb request, (r)ecord, (s)top recording, (c)lear screen
Press CTRL+C to stop Dev Proxy

Important: Always stop Dev Proxy using Ctrl+C to safely unregister it as the system proxy. Closing the terminal without stopping Dev Proxy may cause connection issues.

Building the Plugin

# From the DevProxyExtension directory
cd HttpRecorder.DevProxy
dotnet build

# The plugin DLL will be at:
# bin/Debug/net9.0/HttpRecorder.DevProxy.dll

Configuration

Dev Proxy Configuration

Create or update your devproxyrc.json file:

{
  "plugins": [
    {
      "name": "HttpRecorderPlugin",
      "enabled": true,
      "pluginPath": "./DevProxyExtension/HttpRecorder.DevProxy/bin/Debug/net9.0/HttpRecorder.DevProxy.dll",
      "configSection": "httpRecorder"
    }
  ],
  "urlsToWatch": [
    "https://api.example.com/*",
    "https://graph.microsoft.com/*"
  ],
  "httpRecorder": {
    "outputDirectory": "./recordings",
    "mode": "Record",
    "includeBodies": true,
    "anonymizeSensitiveData": true,
    "sensitiveHeaders": [
      "Authorization",
      "Cookie",
      "Set-Cookie",
      "X-API-Key",
      "X-Auth-Token"
    ]
  }
}

Configuration Options

• outputDirectory: Directory where HAR files will be saved (default: ./recordings)
• mode: Recording mode - currently supports "Record" (default)
• includeBodies: Whether to include request/response bodies (default: true)
• anonymizeSensitiveData: Redact sensitive headers (default: true)
• sensitiveHeaders: Array of header names to anonymize

Running Dev Proxy with the Plugin

# Start Dev Proxy with your configuration
devproxy --config-file devproxyrc.json

# Or if devproxyrc.json is in the current directory
devproxy

# For beta version
devproxy-beta --config-file devproxyrc.json

Verifying Dev Proxy is Working

Before using the plugin, confirm Dev Proxy is intercepting requests:

# Test with Invoke-WebRequest (PowerShell)
Invoke-WebRequest -Uri https://jsonplaceholder.typicode.com/posts

# Or with curl
curl -ikx http://localhost:8000 https://jsonplaceholder.typicode.com/posts

You should see output in the Dev Proxy terminal like:

 req   ╭ GET https://jsonplaceholder.typicode.com/posts
 time  │ 1/31/2025 12:12:14 PM +00:00
 api   ╰ Passed through

How It Works

• Request Interception: When Dev Proxy intercepts an HTTP request matching urlsToWatch, the BeforeRequestAsync method is called
• Request Recording: The plugin creates an Interaction object and stores request details (URL, method, headers, body)
• Response Interception: When the response arrives, AfterResponseAsync is called
• Response Recording: The plugin updates the interaction with response details (status code, headers, body, timing)
• HAR Export: The complete interaction is saved as a HAR file using HttpArchiveInteractionRepository

HAR File Output

Each recorded interaction is saved as a separate HAR file:

recordings/
├── 20251104_143022_1_api_example_com_users.har
├── 20251104_143023_2_api_example_com_orders.har
└── ...

Filenames include:

• Timestamp (yyyyMMdd_HHmmss)
• Interaction ID
• Sanitized URL path

Integration with Dev Proxy Abstractions

Note: The current implementation includes a stub BasePlugin.cs class. For production use:

• Install Dev Proxy and locate DevProxy.Abstractions.dll
• Add it as a reference in the .csproj file:

<ItemGroup>
  <Reference Include="DevProxy.Abstractions">
    <HintPath>path/to/DevProxy.Abstractions.dll</HintPath>
  </Reference>
</ItemGroup>

• Remove the stub BasePlugin.cs file
• Update imports to use DevProxy.Abstractions namespace

Use Cases

• API Testing: Record API interactions for test fixtures
• Documentation: Generate HAR files to document API behavior
• Debugging: Capture full request/response cycles for troubleshooting
• Replay: Save production traffic for replay in test environments
• Analysis: Analyze API performance and payloads

Example Workflow

# 1. Build the plugin
cd DevProxyExtension/HttpRecorder.DevProxy
dotnet build

# 2. Configure Dev Proxy (edit devproxyrc.json)

# 3. Start Dev Proxy
devproxy

# 4. Configure your application to use the proxy
$env:HTTP_PROXY = "http://localhost:8000"
$env:HTTPS_PROXY = "http://localhost:8000"

# 5. Run your application
# HTTP traffic will be recorded to ./recordings/

# 6. Stop Dev Proxy (Ctrl+C)

# 7. Review HAR files
ls ./recordings/*.har

Viewing HAR Files

HAR files can be viewed in:

• Chrome DevTools (Network tab → Import HAR)
• Firefox DevTools (Network tab → Import HAR)
• HAR Viewer
• Charles Proxy
• Fiddler

Advanced Usage

Custom Anonymization Rules

Extend the plugin to add custom anonymization logic:

private void AnonymizeSensitiveHeaders(Dictionary<string, string> headers)
{
    // Existing logic...
    
    // Custom: Anonymize API keys in query strings
    if (headers.ContainsKey("X-Custom-Header"))
    {
        headers["X-Custom-Header"] = MaskApiKey(headers["X-Custom-Header"]);
    }
}

Filtering Requests

Modify BeforeRequestAsync to add custom filtering:

public override Task BeforeRequestAsync(ProxyRequestArgs e)
{
    // Only record POST/PUT requests
    if (e.Session.HttpClient.Request.Method != "POST" && 
        e.Session.HttpClient.Request.Method != "PUT")
    {
        return Task.CompletedTask;
    }
    
    // Continue with recording...
}

Troubleshooting

Plugin Not Loading

• Verify the pluginPath in devproxyrc.json is correct
• Check that the DLL was built successfully
• Ensure .NET 9.0 runtime is installed

No HAR Files Generated

• Check the outputDirectory has write permissions
• Verify urlsToWatch patterns match your requests
• Check Dev Proxy console for error messages

Missing Request/Response Bodies

• Set includeBodies: true in configuration
• Some content types may not be captured (binary, streaming)

Contributing

This plugin is part of the HttpRecorder.Next project. See the main README for contribution guidelines.

License

MIT License - see LICENSE file in the project root.

References

• Microsoft Dev Proxy Documentation
• Creating Custom Dev Proxy Plugins
• HAR Specification
• HttpRecorder.Next Repository