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package sshd
import (
"context"
"fmt"
"net"
"net/http"
"sync"
"time"
"github.com/pires/go-proxyproto"
"golang.org/x/crypto/ssh"
"gitlab.com/gitlab-org/gitlab-shell/internal/config"
"gitlab.com/gitlab-org/labkit/correlation"
"gitlab.com/gitlab-org/labkit/log"
)
type status int
const (
StatusStarting status = iota
StatusReady
StatusOnShutdown
StatusClosed
ProxyHeaderTimeout = 90 * time.Second
)
type Server struct {
Config *config.Config
status status
statusMu sync.RWMutex
wg sync.WaitGroup
listener net.Listener
serverConfig *serverConfig
}
func NewServer(cfg *config.Config) (*Server, error) {
serverConfig, err := newServerConfig(cfg)
if err != nil {
return nil, err
}
return &Server{Config: cfg, serverConfig: serverConfig}, nil
}
func (s *Server) ListenAndServe(ctx context.Context) error {
if err := s.listen(ctx); err != nil {
return err
}
defer s.listener.Close()
s.serve(ctx)
return nil
}
func (s *Server) Shutdown() error {
if s.listener == nil {
return nil
}
s.changeStatus(StatusOnShutdown)
return s.listener.Close()
}
func (s *Server) MonitoringServeMux() *http.ServeMux {
mux := http.NewServeMux()
mux.HandleFunc(s.Config.Server.ReadinessProbe, func(w http.ResponseWriter, r *http.Request) {
if s.getStatus() == StatusReady {
w.WriteHeader(http.StatusOK)
} else {
w.WriteHeader(http.StatusServiceUnavailable)
}
})
mux.HandleFunc(s.Config.Server.LivenessProbe, func(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusOK)
})
return mux
}
func (s *Server) listen(ctx context.Context) error {
sshListener, err := net.Listen("tcp", s.Config.Server.Listen)
if err != nil {
return fmt.Errorf("failed to listen for connection: %w", err)
}
if s.Config.Server.ProxyProtocol {
sshListener = &proxyproto.Listener{
Listener: sshListener,
Policy: unconditionalRequirePolicy,
ReadHeaderTimeout: ProxyHeaderTimeout,
}
log.ContextLogger(ctx).Info("Proxy protocol is enabled")
}
log.WithContextFields(ctx, log.Fields{"tcp_address": sshListener.Addr().String()}).Info("Listening for SSH connections")
s.listener = sshListener
return nil
}
func (s *Server) serve(ctx context.Context) {
s.changeStatus(StatusReady)
for {
nconn, err := s.listener.Accept()
if err != nil {
if s.getStatus() == StatusOnShutdown {
break
}
log.ContextLogger(ctx).WithError(err).Warn("Failed to accept connection")
continue
}
s.wg.Add(1)
go s.handleConn(ctx, nconn)
}
s.wg.Wait()
s.changeStatus(StatusClosed)
}
func (s *Server) changeStatus(st status) {
s.statusMu.Lock()
s.status = st
s.statusMu.Unlock()
}
func (s *Server) getStatus() status {
s.statusMu.RLock()
defer s.statusMu.RUnlock()
return s.status
}
func (s *Server) handleConn(ctx context.Context, nconn net.Conn) {
defer s.wg.Done()
defer nconn.Close()
ctx, cancel := context.WithCancel(correlation.ContextWithCorrelation(ctx, correlation.SafeRandomID()))
defer cancel()
conn := newConnection(s.Config.Server.ConcurrentSessionsLimit, nconn)
conn.handle(ctx, s.serverConfig.get(ctx), func(ctx context.Context, sconn *ssh.ServerConn, channel ssh.Channel, requests <-chan *ssh.Request) error {
session := &session{
cfg: s.Config,
channel: channel,
gitlabKeyId: sconn.Permissions.Extensions["key-id"],
remoteAddr: nconn.RemoteAddr().String(),
}
return session.handle(ctx, requests)
})
}
func unconditionalRequirePolicy(_ net.Addr) (proxyproto.Policy, error) {
return proxyproto.REQUIRE, nil
}
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