enhance: add functions for daemon servers for mTLS (#87)

Signed-off-by: Grant Linville <[email protected]>

pkg/daemon/daemon.go

@@ -0,0 +1,102 @@
+package daemon
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"net/http"
+	"os"
+)
+
+type Server struct {
+	mux       *http.ServeMux
+	tlsConfig *tls.Config
+}
+
+// CreateServer creates a new HTTP server with TLS configured for GPTScript.
+// This function should be used when creating a new server for a daemon tool.
+// The server should then be started with the StartServer function.
+func CreateServer() (*Server, error) {
+	return CreateServerWithMux(http.DefaultServeMux)
+}
+
+// CreateServerWithMux creates a new HTTP server with TLS configured for GPTScript.
+// This function should be used when creating a new server for a daemon tool with a custom ServeMux.
+// The server should then be started with the StartServer function.
+func CreateServerWithMux(mux *http.ServeMux) (*Server, error) {
+	tlsConfig, err := getTLSConfig()
+	if err != nil {
+		return nil, fmt.Errorf("failed to get TLS config: %v", err)
+	}
+
+	return &Server{
+		mux:       mux,
+		tlsConfig: tlsConfig,
+	}, nil
+}
+
+// Start starts an HTTP server created by the CreateServer function.
+// This is for use with daemon tools.
+func (s *Server) Start() error {
+	server := &http.Server{
+		Addr:      fmt.Sprintf("127.0.0.1:%s", os.Getenv("PORT")),
+		TLSConfig: s.tlsConfig,
+		Handler:   s.mux,
+	}
+
+	if err := server.ListenAndServeTLS("", ""); err != nil && !errors.Is(err, http.ErrServerClosed) {
+		return fmt.Errorf("stopped serving: %v", err)
+	}
+	return nil
+}
+
+func (s *Server) HandleFunc(pattern string, handler http.HandlerFunc) {
+	s.mux.HandleFunc(pattern, handler)
+}
+
+func getTLSConfig() (*tls.Config, error) {
+	certB64 := os.Getenv("CERT")
+	privateKeyB64 := os.Getenv("PRIVATE_KEY")
+	gptscriptCertB64 := os.Getenv("GPTSCRIPT_CERT")
+
+	if certB64 == "" {
+		return nil, fmt.Errorf("CERT not set")
+	} else if privateKeyB64 == "" {
+		return nil, fmt.Errorf("PRIVATE_KEY not set")
+	} else if gptscriptCertB64 == "" {
+		return nil, fmt.Errorf("GPTSCRIPT_CERT not set")
+	}
+
+	certBytes, err := base64.StdEncoding.DecodeString(certB64)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode cert base64: %v", err)
+	}
+
+	privateKeyBytes, err := base64.StdEncoding.DecodeString(privateKeyB64)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode private key base64: %v", err)
+	}
+
+	gptscriptCertBytes, err := base64.StdEncoding.DecodeString(gptscriptCertB64)
+	if err != nil {
+		return nil, fmt.Errorf("failed to decode gptscript cert base64: %v", err)
+	}
+
+	cert, err := tls.X509KeyPair(certBytes, privateKeyBytes)
+	if err != nil {
+		return nil, fmt.Errorf("failed to create X509 key pair: %v", err)
+	}
+
+	pool := x509.NewCertPool()
+	if !pool.AppendCertsFromPEM(gptscriptCertBytes) {
+		return nil, fmt.Errorf("failed to append gptscript cert to pool")
+	}
+
+	return &tls.Config{
+		Certificates: []tls.Certificate{cert},
+		ClientCAs:    pool,
+		ClientAuth:   tls.RequireAndVerifyClientCert,
+	}, nil
+}