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control_persist.go
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323 lines (276 loc) · 8 KB
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package sshlib
import (
"context"
"encoding/base64"
"encoding/json"
"errors"
"fmt"
"os"
"os/exec"
"sync/atomic"
"time"
)
const controlPersistEnv = "GO_SSHLIB_CONTROL_PERSIST_PAYLOAD"
type controlPersistPayload struct {
Host string
Port string
User string
ControlPath string
ControlPersistNanos int64
CheckKnownHosts bool
OverwriteKnownHosts bool
KnownHostsFiles []string
Auth []controlPersistAuthMethodDefinition
ProxyRoute []controlPersistProxyRoute
}
type detachedControlMaster struct {
*controlMaster
persist time.Duration
lastUsed atomic.Int64
closeFlag atomic.Bool
}
func init() {
payload := os.Getenv(controlPersistEnv)
if payload == "" {
return
}
debugln("sshlib: control persist helper starting")
err := runDetachedControlMaster(payload)
if err != nil {
debugln("sshlib: control persist helper failed:", err)
fmt.Fprintln(os.Stderr, err)
os.Exit(1)
}
debugln("sshlib: control persist helper exited cleanly")
os.Exit(0)
}
func (c *Connect) startDetachedControlMaster(host, port, user string) error {
debugf("sshlib: startDetachedControlMaster host=%s port=%s user=%s control_path=%s\n", host, port, user, c.ControlPath)
if c.ControlPersistAuth == nil {
return errors.New("sshlib: ControlPersistAuth is required when ControlPersist is enabled")
}
if c.ProxyDialer != nil {
return errors.New("sshlib: detached ControlPersist does not support ProxyDialer yet")
}
if c.HostKeyCallback != nil && !c.CheckKnownHosts {
return errors.New("sshlib: detached ControlPersist supports CheckKnownHosts or default insecure host key validation only")
}
resolvedAuths, err := c.ControlPersistAuth.resolved()
if err != nil {
return err
}
serializedProxyRoute, err := serializeControlPersistProxyRoutes(c.ProxyRoute)
if err != nil {
return err
}
payload := controlPersistPayload{
Host: host,
Port: port,
User: user,
ControlPath: c.ControlPath,
ControlPersistNanos: int64(c.ControlPersist),
CheckKnownHosts: c.CheckKnownHosts,
OverwriteKnownHosts: c.OverwriteKnownHosts,
KnownHostsFiles: append([]string(nil), c.KnownHostsFiles...),
Auth: resolvedAuths,
ProxyRoute: serializedProxyRoute,
}
encoded, err := encodeControlPersistPayload(payload)
if err != nil {
return err
}
debugf("sshlib: detached helper payload encoded bytes=%d proxy_hops=%d\n", len(encoded), len(payload.ProxyRoute))
exe, err := os.Executable()
if err != nil {
return err
}
cmd := exec.Command(exe, os.Args[1:]...)
cmd.Env = append(os.Environ(), controlPersistEnv+"="+encoded)
devNull, err := os.OpenFile(os.DevNull, os.O_RDWR, 0)
if err != nil {
return err
}
defer devNull.Close()
cmd.Stdin = devNull
cmd.Stdout = devNull
cmd.Stderr = devNull
promptBridge, cleanupPromptIPC, err := setupControlPersistPromptIPC(cmd)
if err != nil {
return err
}
setDetachedSysProcAttr(cmd)
if err := cmd.Start(); err != nil {
cleanupPromptIPC()
debugln("sshlib: failed to start detached control master:", err)
return err
}
debugf("sshlib: detached control master started pid=%d\n", cmd.Process.Pid)
startControlPersistPromptIPC(promptBridge)
return nil
}
func encodeControlPersistPayload(payload controlPersistPayload) (string, error) {
data, err := json.Marshal(payload)
if err != nil {
return "", err
}
return base64.StdEncoding.EncodeToString(data), nil
}
func decodeControlPersistPayload(encoded string) (controlPersistPayload, error) {
data, err := base64.StdEncoding.DecodeString(encoded)
if err != nil {
return controlPersistPayload{}, err
}
var payload controlPersistPayload
if err := json.Unmarshal(data, &payload); err != nil {
return controlPersistPayload{}, err
}
return payload, nil
}
func runDetachedControlMaster(encoded string) error {
debugln("sshlib: decoding control persist payload")
payload, err := decodeControlPersistPayload(encoded)
if err != nil {
return err
}
debugln("sshlib: loading control persist prompt bridge")
prompt, cleanupPrompt, err := loadControlPersistPrompt()
if err != nil {
return err
}
defer cleanupPrompt()
debugln("sshlib: rebuilding auth methods")
authMethods, err := createControlPersistAuthMethodsWithPrompt(payload.Auth, prompt)
if err != nil {
return err
}
con := &Connect{
CheckKnownHosts: payload.CheckKnownHosts,
OverwriteKnownHosts: payload.OverwriteKnownHosts,
KnownHostsFiles: append([]string(nil), payload.KnownHostsFiles...),
ControlPath: payload.ControlPath,
ControlPersist: time.Duration(payload.ControlPersistNanos),
}
if len(payload.ProxyRoute) > 0 {
debugf("sshlib: rebuilding proxy route hops=%d\n", len(payload.ProxyRoute))
dialer, proxyConnects, err := buildControlPersistProxyRouteDialer(payload.ProxyRoute, prompt)
if err != nil {
return err
}
con.ProxyDialer = dialer
con.proxyConnects = proxyConnects
}
debugf("sshlib: connecting target %s:%s as %s\n", payload.Host, payload.Port, payload.User)
if err := con.createDirectClient(payload.Host, payload.Port, payload.User, authMethods); err != nil {
_ = con.closeProxyConnects()
return err
}
debugln("sshlib: starting detached control master listener")
master, err := newDetachedControlMaster(con, payload.ControlPath, time.Duration(payload.ControlPersistNanos))
if err != nil {
_ = con.Client.Close()
return err
}
con.controlMaster = master.controlMaster
return master.serve(context.Background())
}
func newDetachedControlMaster(c *Connect, path string, persist time.Duration) (*detachedControlMaster, error) {
base, err := newControlMaster(c, path)
if err != nil {
return nil, err
}
d := &detachedControlMaster{
controlMaster: base,
persist: persist,
}
base.onActivity = d.touch
d.touch()
return d, nil
}
func (m *detachedControlMaster) serve(ctx context.Context) error {
if m.persist <= 0 {
<-ctx.Done()
return nil
}
ticker := time.NewTicker(500 * time.Millisecond)
defer ticker.Stop()
for {
select {
case <-ctx.Done():
return nil
case <-ticker.C:
if m.isIdleExpired() {
m.connect.ControlPersist = 0
return m.Close()
}
}
}
}
func (m *detachedControlMaster) isIdleExpired() bool {
m.sessionMu.Lock()
active := m.activeSessions
m.sessionMu.Unlock()
if active > 0 {
return false
}
last := time.Unix(0, m.lastUsed.Load())
return time.Since(last) >= m.persist
}
func (m *detachedControlMaster) touch() {
m.lastUsed.Store(time.Now().UnixNano())
}
func waitForControlClient(path string, timeout time.Duration) (*controlClient, error) {
deadline := time.Now().Add(timeout)
for {
client, err := dialControlClient(path)
if err == nil {
return client, nil
}
if time.Now().After(deadline) {
return nil, err
}
time.Sleep(100 * time.Millisecond)
}
}
func (c *Connect) ensureControlClient() error {
if c.controlClient == nil {
return errors.New("sshlib: control client is not initialized")
}
if err := c.controlClient.Ping(); err == nil {
return nil
}
if c.ControlPersist <= 0 {
return errors.New("sshlib: control master is unavailable")
}
if err := c.startDetachedControlMaster(c.controlHost, c.controlPort, c.controlUser); err != nil {
return err
}
c.controlSpawned = true
client, err := waitForControlClient(c.ControlPath, 5*time.Second)
if err != nil {
return err
}
c.controlClient = client
return nil
}
func (c *Connect) requestControl(req controlRequest) (controlResponse, error) {
if err := c.ensureControlClient(); err != nil {
return controlResponse{}, err
}
resp, err := c.controlClient.request(req)
if err == nil {
return resp, nil
}
if c.ControlPersist <= 0 {
return controlResponse{}, err
}
if err := c.startDetachedControlMaster(c.controlHost, c.controlPort, c.controlUser); err != nil {
return controlResponse{}, err
}
c.controlSpawned = true
client, reacquireErr := waitForControlClient(c.ControlPath, 5*time.Second)
if reacquireErr != nil {
return controlResponse{}, reacquireErr
}
c.controlClient = client
return c.controlClient.request(req)
}