http-proxy - SKILL.md Agent Skill

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