forked from owenthereal/upterm
/
reversetunnel.go
191 lines (161 loc) · 4.41 KB
/
reversetunnel.go
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package internal
import (
"context"
"fmt"
"net"
"net/url"
"os/user"
"strings"
"time"
"github.com/owenthereal/upterm/host/api"
"github.com/owenthereal/upterm/server"
"github.com/owenthereal/upterm/upterm"
"github.com/owenthereal/upterm/ws"
log "github.com/sirupsen/logrus"
"golang.org/x/crypto/ssh"
"google.golang.org/protobuf/proto"
)
const (
publickeyAuthError = "ssh: unable to authenticate, attempted methods [none]"
)
type ReverseTunnel struct {
*ssh.Client
Host *url.URL
Signers []ssh.Signer
AuthorizedKeys []ssh.PublicKey
KeepAliveDuration time.Duration
HostKeyCallback ssh.HostKeyCallback
Logger log.FieldLogger
ln net.Listener
}
func (c *ReverseTunnel) Close() {
c.ln.Close()
c.Client.Close()
}
func (c *ReverseTunnel) Listener() net.Listener {
return c.ln
}
func (c *ReverseTunnel) Establish(ctx context.Context) (*server.CreateSessionResponse, error) {
user, err := user.Current()
if err != nil {
return nil, err
}
var (
auths []ssh.AuthMethod
publicKeys [][]byte
authorizedKeys [][]byte
)
for _, signer := range c.Signers {
auths = append(auths, ssh.PublicKeys(signer))
publicKeys = append(publicKeys, ssh.MarshalAuthorizedKey(signer.PublicKey()))
}
for _, ak := range c.AuthorizedKeys {
authorizedKeys = append(authorizedKeys, ssh.MarshalAuthorizedKey(ak))
}
id := &api.Identifier{
Id: user.Username,
Type: api.Identifier_HOST,
}
encodedID, err := api.EncodeIdentifier(id)
if err != nil {
return nil, err
}
config := &ssh.ClientConfig{
User: encodedID,
Auth: auths,
ClientVersion: upterm.HostSSHClientVersion,
// Enforce a restricted set of algorithms for security
// TODO: make this configurable if necessary
HostKeyAlgorithms: []string{
ssh.CertAlgoED25519v01,
ssh.CertAlgoRSASHA512v01,
ssh.CertAlgoRSASHA256v01,
ssh.KeyAlgoED25519,
ssh.KeyAlgoRSASHA512,
ssh.KeyAlgoRSASHA256,
},
HostKeyCallback: c.HostKeyCallback,
}
if isWSScheme(c.Host.Scheme) {
u, _ := url.Parse(c.Host.String()) // clone
u.User = url.UserPassword(encodedID, "")
c.Client, err = ws.NewSSHClient(u, config, false)
} else {
c.Client, err = ssh.Dial("tcp", c.Host.Host, config)
}
if err != nil {
return nil, sshDialError(c.Host.String(), err)
}
sessResp, err := c.createSession(user.Username, publicKeys, authorizedKeys)
if err != nil {
return nil, fmt.Errorf("error creating session: %w", err)
}
c.ln, err = c.Client.Listen("unix", sessResp.SessionID)
if err != nil {
return nil, fmt.Errorf("unable to create reverse tunnel: %w", err)
}
// make sure connection is alive
go keepAlive(ctx, c.KeepAliveDuration, func() {
// TODO: ping with session ID
_, _, err := c.Client.SendRequest(upterm.OpenSSHKeepAliveRequestType, true, nil)
if err != nil {
c.Logger.WithError(err).Error("error pinging server")
}
})
return sessResp, nil
}
func (c *ReverseTunnel) createSession(user string, hostPublicKeys [][]byte, clientAuthorizedKeys [][]byte) (*server.CreateSessionResponse, error) {
req := &server.CreateSessionRequest{
HostUser: user,
HostPublicKeys: hostPublicKeys,
ClientAuthorizedKeys: clientAuthorizedKeys,
}
b, err := proto.Marshal(req)
if err != nil {
return nil, err
}
ok, body, err := c.Client.SendRequest(upterm.ServerCreateSessionRequestType, true, b)
if err != nil {
return nil, fmt.Errorf("error initializing session: %w", err)
}
if !ok {
return nil, fmt.Errorf("could not initialize session: %s", body)
}
var resp server.CreateSessionResponse
if err := proto.Unmarshal(body, &resp); err != nil {
return nil, fmt.Errorf("error unmarshaling created session: %w", err)
}
return &resp, nil
}
func keepAlive(ctx context.Context, d time.Duration, fn func()) {
ticker := time.NewTicker(d)
defer ticker.Stop()
for {
select {
case <-ctx.Done():
return
case <-ticker.C:
fn()
}
}
}
func isWSScheme(scheme string) bool {
return scheme == "ws" || scheme == "wss"
}
type PermissionDeniedError struct {
host string
err error
}
func (e *PermissionDeniedError) Error() string {
return fmt.Sprintf("%s: Permission denied (publickey).", e.host)
}
func (e *PermissionDeniedError) Unwrap() error { return e.err }
func sshDialError(host string, err error) error {
if strings.Contains(err.Error(), publickeyAuthError) {
return &PermissionDeniedError{
host: host,
err: err,
}
}
return fmt.Errorf("ssh dial error: %w", err)
}