feat: Add Support for Proxy with Interceptor (#77)

examples/proxy/.gitignore

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+ca-cert.pem
+proxy

examples/proxy/README.md

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+# Proxy Example: HTTPS Logging
+
+This example demonstrates using the PMG proxy server to intercept and log HTTPS requests to package registries.
+
+## Usage
+
+### Build and Run
+
+```bash
+cd examples/proxy
+go run .
+```
+
+### Configure Your Environment
+
+Open a new terminal and configure the proxy:
+
+```bash
+export HTTPS_PROXY=http://127.0.0.1:8888
+export NODE_EXTRA_CA_CERTS=./ca-cert.pem
+export SSL_CERT_FILE=./ca-cert.pem
+export PIP_CERT=./ca-cert.pem
+export REQUESTS_CA_BUNDLE=./ca-cert.pem
+export PIP_PROXY=http://127.0.0.1:8888
+```
+
+### Test with Package Managers
+
+Test with `npm`:
+
+```bash
+npm --no-cache --prefer-online install express
+```
+
+Test with `pip`:
+
+```bash
+pip3 --proxy http://127.0.0.1:8888 index versions requests
+```
+
+```bash
+pip3 install --proxy http://127.0.0.1:8888 --no-cache-dir requests
+```

examples/proxy/logging_interceptor.go

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+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/safedep/pmg/proxy"
+)
+
+type loggingInterceptor struct {
+	domains []string
+}
+
+func newLoggingInterceptor() *loggingInterceptor {
+	return &loggingInterceptor{
+		domains: []string{
+			"registry.npmjs.org",
+			"registry.yarnpkg.com",
+			"pypi.org",
+			"files.pythonhosted.org",
+		},
+	}
+}
+
+func (li *loggingInterceptor) Name() string {
+	return "logging-interceptor"
+}
+
+func (li *loggingInterceptor) ShouldIntercept(ctx *proxy.RequestContext) bool {
+	for _, domain := range li.domains {
+		if ctx.Hostname == domain {
+			return true
+		}
+	}
+
+	return false
+}
+
+func (li *loggingInterceptor) HandleRequest(ctx *proxy.RequestContext) (*proxy.InterceptorResponse, error) {
+	fmt.Printf("LOGGING INTERCEPTOR: [%s] %s %s %s\n",
+		ctx.StartTime.Format(time.RFC3339),
+		ctx.RequestID,
+		ctx.Method,
+		ctx.URL.String(),
+	)
+
+	return &proxy.InterceptorResponse{
+		Action: proxy.ActionAllow,
+	}, nil
+}

examples/proxy/main.go

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+package main
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
+
+	"github.com/safedep/dry/log"
+	"github.com/safedep/pmg/proxy"
+	"github.com/safedep/pmg/proxy/certmanager"
+)
+
+const (
+	listenAddr     = "127.0.0.1:8888"
+	connectTimeout = 30 * time.Second
+	requestTimeout = 5 * time.Minute
+)
+
+func main() {
+	log.InitZapLogger("proxy-example", "dev")
+
+	fmt.Println("Generating CA certificate...")
+
+	caConfig := certmanager.DefaultCertManagerConfig()
+	caCert, err := certmanager.GenerateCA(caConfig)
+	if err != nil {
+		log.Fatalf("Failed to generate CA: %v", err)
+	}
+
+	// Save CA cert for use with clients
+	if err := os.WriteFile("ca-cert.pem", caCert.Certificate, 0644); err != nil {
+		log.Fatalf("Failed to save CA cert: %v", err)
+	}
+
+	fmt.Println("✓ CA certificate saved to ca-cert.pem")
+	fmt.Println()
+	fmt.Println("To trust this CA:")
+	fmt.Println("  Node.js: export NODE_EXTRA_CA_CERTS=./ca-cert.pem")
+	fmt.Println("  Python:  export SSL_CERT_FILE=./ca-cert.pem")
+	fmt.Println("  System:  Add ca-cert.pem to your OS trust store")
+	fmt.Println()
+
+	// Create certificate manager with CA certificate for use with proxy
+	certMgr, err := certmanager.NewCertificateManagerWithCA(caCert, caConfig)
+	if err != nil {
+		log.Fatalf("Failed to create cert manager: %v", err)
+	}
+
+	// Create proxy with certificate manager and logging interceptor
+	proxyConfig := &proxy.ProxyConfig{
+		ListenAddr:     listenAddr,
+		CertManager:    certMgr,
+		EnableMITM:     true,
+		Interceptors:   []proxy.Interceptor{newLoggingInterceptor()},
+		ConnectTimeout: connectTimeout,
+		RequestTimeout: requestTimeout,
+	}
+
+	proxyServer, err := proxy.NewProxyServer(proxyConfig)
+	if err != nil {
+		log.Fatalf("Failed to create proxy server: %v", err)
+	}
+
+	// Start proxy
+	if err := proxyServer.Start(); err != nil {
+		log.Fatalf("Failed to start proxy: %v", err)
+	}
+
+	fmt.Printf("Proxy listening on %s\n", proxyServer.Address())
+	fmt.Printf("Configure clients with: export HTTPS_PROXY=http://%s\n", listenAddr)
+	fmt.Println()
+	fmt.Println("Press Ctrl+C to stop")
+	fmt.Println()
+
+	// Wait for interrupt signal to gracefully shutdown
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM)
+	<-sigChan
+
+	// Graceful shutdown
+	fmt.Println("\nShutting down proxy...")
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+
+	if err := proxyServer.Stop(ctx); err != nil {
+		log.Errorf("Error during shutdown: %v", err)
+	}
+
+	fmt.Println("Proxy stopped")
+}