Proxy Server Skill

Expert skill for proxy server implementation, configuration, and network traffic interception.

Capabilities

• Proxy Configuration: Configure Squid, mitmproxy, Charles, and nginx proxy
• HTTP CONNECT Tunneling: Implement HTTP CONNECT for HTTPS tunneling
• SOCKS Protocol: Configure SOCKS4/SOCKS5 proxy servers
• Transparent Proxying: Implement transparent proxying with iptables/nftables
• Traffic Analysis: Analyze proxy traffic and generate reports
• Debugging: Debug proxy connection issues and SSL/TLS interception
• PAC File Generation: Generate Proxy Auto-Configuration (PAC) files
• Caching: Configure proxy caching strategies

Tools and Dependencies

• Squid - Caching proxy server
• mitmproxy - Interactive HTTPS proxy
• nginx - HTTP and reverse proxy
• iptables/nftables - Linux firewall for transparent proxy
• Charles - HTTP proxy/monitor
• tinyproxy - Lightweight proxy

Target Processes

• http-proxy-server.js
• socks5-proxy.js
• transparent-proxy.js

Usage Examples

Squid HTTP Proxy Configuration

http_port 3128
acl localnet src 10.0.0.0/8
http_access allow localnet
cache_dir ufs /var/spool/squid 10000 16 256

Transparent Proxy with iptables

iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 80 -j REDIRECT --to-port 3128
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 3129

mitmproxy Interception

mitmproxy -p 8080 --mode transparent
mitmdump -w traffic.flow

PAC File Example

function FindProxyForURL(url, host) {
    if (isPlainHostName(host)) return "DIRECT";
    if (dnsDomainIs(host, ".internal.com")) return "DIRECT";
    return "PROXY proxy.example.com:8080";
}

Quality Gates

• Proxy functionality verified
• SSL/TLS interception working
• Transparent mode operational
• Caching efficiency validated
• Access control tested