# ArcArcGo: DuckDuckGo Proxy with Custom Branding

GitHub: 0xarchit/ArcArcGo

Live Demo: https://arcarcgo.0xarc.workers.dev

ArcArcGo demonstrates advanced Cloudflare Workers capabilities by intercepting requests, fetching content from DuckDuckGo, and modifying responses before serving them to clients with custom branding and functionality.

1. Client Request → Cloudflare Worker
2. Worker Processing → DuckDuckGo Server
3. Response Modification → Client

graph LR
    A[Client] --> B[Cloudflare Worker]
    B --> C[DuckDuckGo]
    C --> B
    B --> A
    B -.-> D[URL Rewriting + Branding]

The worker uses a fetch event listener to intercept all incoming HTTP requests and delegates processing to the main handleRequest function.

The worker extracts the pathname, search parameters, and hash from incoming requests and constructs the target DuckDuckGo URL while maintaining the original query structure.

Header Modifications:

• Removed: Host, X-Forwarded-For (prevents detection as proxy)
• Set: Standard browser Accept header
• Set: Default User-Agent if not present

Response Header Modifications:

• Removed: Content-Security-Policy (allows script injection)
• Added: CORS header for cross-origin access

Images, CSS, JavaScript, and other assets are passed through unchanged, maintaining original response body and headers.

Uses TransformStream for real-time content modification without buffering the entire response.

The worker uses comprehensive regex patterns to identify and rewrite URLs, including:

• Standard HTML attributes: href, src, action in both double and single quotes
• CSS URLs: url() declarations
• Meta refresh: URL redirects in meta tags
• JavaScript redirects: window.location, location.href, etc.
• Data attributes: Custom data URLs for navigation
• Absolute paths: Standalone paths in quotes
• Event handlers: onclick, onchange, onsubmit attributes

Only processes DuckDuckGo URLs by stripping the domain and prepending the proxy base URL.

Resolves relative URLs against the DuckDuckGo origin while maintaining query parameters.

• Fragments (#): Preserved unchanged
• Data URLs: Preserved unchanged
• JavaScript URLs: Preserved unchanged
• Event Handlers: Special processing for location changes

Real-time text replacement in HTML content using regex patterns to replace "DuckDuckGo" with "ArcArcGo" and handle possessive forms.

Regex-based logo replacement that identifies DuckDuckGo logo images and replaces them with the custom ArcArcGo logo.

Dynamic branding through injected script that:

• Text Replacement: Uses TreeWalker to traverse all text nodes
• Title Replacement: Updates document title
• Logo Replacement: Targets specific CSS selectors for logo images
• Dynamic Monitoring: Uses MutationObserver for continuously added content
• Multiple Triggers: Responds to load, DOMContentLoaded events, and periodic intervals

The worker processes content in chunks to optimize memory usage and provide real-time response modification. It uses a buffer system with:

Buffer Management:

• Size Threshold: 8192 bytes
• Content Threshold: Presence of </body> tag
• Final Processing: Script injection before response completion

The worker implements comprehensive error handling for:

• Network connectivity issues
• Invalid URL construction
• Stream processing errors
• Regex processing failures

All errors return a 500 status response with a descriptive error message.

1. Selective Processing: Only HTML content is modified
2. Chunked Streaming: Real-time processing without buffering entire response
3. Efficient Regex: Compiled patterns for fast matching
4. Header Optimization: Minimal header modifications

• Memory: Stream-based processing minimizes memory usage
• CPU: Regex operations on text chunks
• Network: Direct proxy with minimal latency

1. CSP Removal: Enables script injection
2. Header Sanitization: Removes tracking headers
3. URL Validation: Prevents open proxy attacks
4. Content Filtering: Only processes specific content types

• Open Proxy: Limited to DuckDuckGo domain
• Script Injection: Controlled injection for branding only
• Privacy: No logging or data collection

• Cloudflare account
• Workers subscription (free tier available)

1. Create Worker: In Cloudflare dashboard
2. Deploy Code: Copy worker.js content
3. Configure Routes: Set custom domain or use workers.dev subdomain
4. Test Functionality: Verify search and branding

• Custom Logo: Modify newLogoSrc variable
• Branding Text: Adjust replacement patterns
• Target Domain: Change targetHost for different proxy targets

• Cause: CSP blocking or timing issues
• Solution: Verify CSP removal, check MutationObserver

• Cause: Pattern mismatch or encoding issues
• Solution: Test regex patterns, check URL encoding

• Cause: Large content or complex patterns
• Solution: Optimize buffer size, simplify regex patterns

1. Console Logging: Add logging to worker (remove in production)
2. Network Inspection: Check headers and response codes
3. Content Validation: Verify HTML modifications

• JavaScript-Heavy Sites: May require additional pattern matching
• Dynamic Content: MutationObserver helps but may miss rapid changes
• Complex URLs: Some edge cases may not be covered

• Terms of Service: May violate target site's ToS
• Copyright: Logo and content modifications
• Educational Use: Intended for learning purposes only

ArcArcGo demonstrates advanced Cloudflare Workers capabilities including:

The implementation showcases how modern edge computing can be used to create sophisticated web proxies while maintaining the performance and functionality of the underlying service.