http-proxy

name	http-proxy
description	Use when working on the HTTP/HTTPS proxy in pkg/httpproxy — request forwarding, HTTPS CONNECT tunneling, hop-by-hop header stripping, Proxy-Authorization handling, or proxy forwarding tests.

HTTP Proxy Implementation

Expertise in implementing HTTP and HTTPS proxy functionality: request forwarding, CONNECT tunneling, header manipulation, and response handling.

When to use this skill

• Implementing HTTP proxy request forwarding
• Adding HTTPS CONNECT tunnel support
• Debugging proxy forwarding issues
• Optimizing header handling
• Testing HTTP proxy functionality

Expertise areas

• HTTP request parsing and validation
• HTTPS CONNECT tunnel establishment
• Header manipulation and preservation
• Request/response forwarding
• Keep-alive connection management
• Chunked transfer encoding handling
• Proxy authentication
• Performance optimization

Key files

• pkg/httpproxy/httpproxy.go - HTTP proxy implementation
• pkg/httpproxy/httpproxy_test.go - HTTP proxy tests

Common tasks

Implementing HTTP request forwarding

Parse incoming HTTP request, validate target host/port, establish connection to destination, forward request headers and body, relay response back.

Handling HTTPS CONNECT

Parse CONNECT method, establish tunnel to destination, relay encrypted data bidirectionally between client and server.

Managing headers

Preserve important headers (Host, User-Agent, etc.), remove connection-specific headers, handle hop-by-hop headers correctly.

Example patterns

Forward HTTP request

// Parse incoming request
req, err := http.ReadRequest(reader)
if err != nil {
    return err
}

// Validate target
host := req.Header.Get("Host")
if host == "" {
    host = req.URL.Host
}

// Connect to destination
client := &http.Client{
    Timeout: 30 * time.Second,
}
resp, err := client.Do(req)
if err != nil {
    return err
}

// Forward response
resp.Write(writer)

Handle CONNECT method

// Extract target host:port
parts := strings.Split(host, ":")
if len(parts) != 2 {
    return fmt.Errorf("invalid CONNECT target")
}

// Connect to destination
destConn, err := net.Dial("tcp", host)
if err != nil {
    return err
}

// Send 200 response
fmt.Fprintf(writer, "HTTP/1.1 200 Connection Established\r\n\r\n")

// Relay data bidirectionally
go io.Copy(destConn, clientConn)
io.Copy(clientConn, destConn)

Testing approach

• Test HTTP GET, POST, PUT, DELETE methods
• Test HTTPS CONNECT tunnel establishment
• Test header preservation and filtering
• Test response code forwarding
• Test large request/response bodies
• Test chunked transfer encoding
• Test proxy authentication
• Test timeout and error handling

Performance considerations

• Use io.Copy for efficient data transfer
• Implement appropriate timeouts
• Handle keep-alive connections
• Minimize memory allocations
• Consider connection pooling
• Monitor goroutine usage

Security considerations

• Validate target host/port
• Check for SSRF vulnerabilities
• Implement proxy authentication
• Use TLS for sensitive data
• Validate HTTP headers
• Prevent header injection
• Rate limiting for connections
• Log proxy activity appropriately

References

• RFC 7230: HTTP/1.1 Message Syntax and Routing
• RFC 7231: HTTP/1.1 Semantics and Content
• RFC 7232: HTTP/1.1 Conditional Requests
• HTTP CONNECT tunneling documentation

Related skills

• socks5-protocol - Alternative proxy protocol
• credential-management - For proxy authentication
• go-concurrency - For connection handling