emissary/internal/agent/controller/app/server.go

package app

import (
	"context"
	"net"
	"net/http"
	"strings"
	"sync"
	"time"

	"forge.cadoles.com/Cadoles/emissary/internal/agent/controller/app/spec"
	appSpec "forge.cadoles.com/Cadoles/emissary/internal/agent/controller/app/spec"
	"forge.cadoles.com/Cadoles/emissary/internal/proxy/wildcard"
	edgeHTTP "forge.cadoles.com/arcad/edge/pkg/http"
	"gitlab.com/wpetit/goweb/logger"

	"forge.cadoles.com/arcad/edge/pkg/bundle"
	"github.com/go-chi/chi/middleware"
	"github.com/go-chi/chi/v5"
	"github.com/pkg/errors"

	_ "forge.cadoles.com/Cadoles/emissary/internal/imports/passwd"
)

const defaultCookieDuration time.Duration = 24 * time.Hour

type Server struct {
	bundle         bundle.Bundle
	handlerOptions []edgeHTTP.HandlerOptionFunc
	server         *http.Server
	serverMutex    sync.RWMutex
	config         *appSpec.Config
}

func (s *Server) Start(ctx context.Context, addr string) (err error) {
	if s.Running() {
		if err := s.Stop(); err != nil {
			return errors.WithStack(err)
		}
	}

	s.serverMutex.Lock()
	defer s.serverMutex.Unlock()

	router := chi.NewRouter()

	router.Use(middleware.RealIP)
	router.Use(middleware.Logger)
	router.Use(middleware.Compress(5))

	handler := edgeHTTP.NewHandler(s.handlerOptions...)
	if err := handler.Load(s.bundle); err != nil {
		return errors.Wrap(err, "could not load app bundle")
	}

	if s.config != nil {
		if s.config.UnexpectedHostRedirect != nil {
			router.Use(unexpectedHostRedirect(
				s.config.UnexpectedHostRedirect.HostTarget,
				s.config.UnexpectedHostRedirect.AcceptedHostPatterns...,
			))
		}
	}

	router.Handle("/*", handler)

	server := &http.Server{
		Addr:    addr,
		Handler: router,
	}

	go func() {
		defer func() {
			if recovered := recover(); recovered != nil {
				if err, ok := recovered.(error); ok {
					logger.Error(ctx, err.Error(), logger.E(errors.WithStack(err)))

					return
				}

				panic(recovered)
			}
		}()

		defer func() {
			if err := s.Stop(); err != nil {
				panic(errors.WithStack(err))
			}
		}()

		if err := server.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
			panic(errors.WithStack(err))
		}
	}()

	s.server = server

	return nil
}

func (s *Server) Running() bool {
	s.serverMutex.RLock()
	defer s.serverMutex.RUnlock()

	return s.server != nil
}

func (s *Server) Stop() error {
	if !s.Running() {
		return nil
	}

	s.serverMutex.Lock()
	defer s.serverMutex.Unlock()

	if s.server == nil {
		return nil
	}

	if err := s.server.Close(); err != nil {
		s.server = nil

		return errors.WithStack(err)
	}

	s.server = nil

	return nil
}

func NewServer(bundle bundle.Bundle, config *spec.Config, handlerOptions ...edgeHTTP.HandlerOptionFunc) *Server {
	return &Server{
		bundle:         bundle,
		config:         config,
		handlerOptions: handlerOptions,
	}
}

func getCookieDomain(r *http.Request) (string, error) {
	host, _, err := net.SplitHostPort(r.Host)
	if err != nil {
		host = r.Host
	}

	// If host is an IP address
	if ip := net.ParseIP(host); ip != nil {
		return "", nil
	}

	// If host is an domain, return top level domain
	domainParts := strings.Split(host, ".")
	if len(domainParts) >= 2 {
		topLevelDomain := strings.Join(domainParts[len(domainParts)-2:], ".")
		return topLevelDomain, nil
	}

	// By default, return host
	return host, nil
}

func unexpectedHostRedirect(hostTarget string, acceptedHostPatterns ...string) func(http.Handler) http.Handler {
	return func(h http.Handler) http.Handler {
		fn := func(w http.ResponseWriter, r *http.Request) {
			host, port, err := net.SplitHostPort(r.Host)
			if err != nil {
				host = r.Host
			}

			matched := wildcard.MatchAny(host, acceptedHostPatterns...)

			if !matched {
				url := r.URL

				url.Host = hostTarget
				if port != "" {
					url.Host += ":" + port
				}

				http.Redirect(w, r, url.String(), http.StatusTemporaryRedirect)

				return
			}

			h.ServeHTTP(w, r)
		}

		return http.HandlerFunc(fn)
	}
}