AUTH-2004: Adds static host key support

This commit is contained in:
Michael Borkenstein 2019-08-19 13:51:59 -05:00
parent 30c9e2af9b
commit 188f4667cb
2 changed files with 121 additions and 4 deletions

110
sshserver/host_keys.go Normal file
View File

@ -0,0 +1,110 @@
//+build !windows
package sshserver
import (
"crypto/ecdsa"
"crypto/elliptic"
"crypto/rand"
"crypto/rsa"
"crypto/x509"
"encoding/pem"
"fmt"
"io/ioutil"
"os"
"path/filepath"
"github.com/gliderlabs/ssh"
"github.com/pkg/errors"
)
const (
rsaFilename = "ssh_host_rsa_key"
ecdsaFilename = "ssh_host_ecdsa_key"
)
func (s *SSHServer) configureHostKeys() error {
if _, err := os.Stat(configDir); os.IsNotExist(err) {
if err := os.MkdirAll(configDir, 0755); err != nil {
return errors.Wrap(err, fmt.Sprintf("Error creating %s directory", configDir))
}
}
if err := s.configureHostKey(s.ensureECDSAKeyExists); err != nil {
return err
}
if err := s.configureHostKey(s.ensureRSAKeyExists); err != nil {
return err
}
return nil
}
func (s *SSHServer) configureHostKey(keyFunc func() (string, error)) error {
path, err := keyFunc()
if err != nil {
return err
}
if err := s.SetOption(ssh.HostKeyFile(path)); err != nil {
return errors.Wrap(err, "Could not set SSH host key")
}
return nil
}
func (s *SSHServer) ensureRSAKeyExists() (string, error) {
keyPath := filepath.Join(configDir, rsaFilename)
if _, err := os.Stat(keyPath); os.IsNotExist(err) {
key, err := rsa.GenerateKey(rand.Reader, 2048)
if err != nil {
return "", errors.Wrap(err, "Error generating RSA host key")
}
privateKey := &pem.Block{
Type: "RSA PRIVATE KEY",
Bytes: x509.MarshalPKCS1PrivateKey(key),
}
if err = writePrivateKey(keyPath, privateKey); err != nil {
return "", err
}
s.logger.Debug("Created new RSA SSH host key: ", keyPath)
}
return keyPath, nil
}
func (s *SSHServer) ensureECDSAKeyExists() (string, error) {
keyPath := filepath.Join(configDir, ecdsaFilename)
if _, err := os.Stat(keyPath); os.IsNotExist(err) {
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
if err != nil {
return "", errors.Wrap(err, "Error generating ECDSA host key")
}
keyBytes, err := x509.MarshalECPrivateKey(key)
if err != nil {
return "", errors.Wrap(err, "Error marshalling ECDSA key")
}
privateKey := &pem.Block{
Type: "EC PRIVATE KEY",
Bytes: keyBytes,
}
if err = writePrivateKey(keyPath, privateKey); err != nil {
return "", err
}
s.logger.Debug("Created new ECDSA SSH host key: ", keyPath)
}
return keyPath, nil
}
func writePrivateKey(keyPath string, privateKey *pem.Block) error {
if err := ioutil.WriteFile(keyPath, pem.EncodeToMemory(privateKey), 0600); err != nil {
return errors.Wrap(err, fmt.Sprintf("Error writing host key to %s", keyPath))
}
return nil
}

View File

@ -19,24 +19,31 @@ import (
"github.com/sirupsen/logrus" "github.com/sirupsen/logrus"
) )
const (
defaultShellPrompt = `\e[0;31m[\u@\h \W]\$ \e[m `
configDir = "/etc/cloudflared/"
)
type SSHServer struct { type SSHServer struct {
ssh.Server ssh.Server
logger *logrus.Logger logger *logrus.Logger
shutdownC chan struct{} shutdownC chan struct{}
} }
const DefaultShellPrompt = `\e[0;31m[\u@\h \W]\$ \e[m `
func New(logger *logrus.Logger, address string, shutdownC chan struct{}) (*SSHServer, error) { func New(logger *logrus.Logger, address string, shutdownC chan struct{}) (*SSHServer, error) {
currentUser, err := user.Current() currentUser, err := user.Current()
if err != nil { if err != nil {
return nil, err return nil, err
} }
if currentUser.Uid != "0" { if currentUser.Uid != "0" {
return nil, errors.New("cloudflared ssh server needs to run as root") return nil, errors.New("cloudflared SSH server needs to run as root")
} }
sshServer := SSHServer{ssh.Server{Addr: address}, logger, shutdownC} sshServer := SSHServer{ssh.Server{Addr: address}, logger, shutdownC}
if err := sshServer.configureHostKeys(); err != nil {
return nil, err
}
return &sshServer, nil return &sshServer, nil
} }
@ -85,7 +92,7 @@ func (s *SSHServer) connectionHandler(session ssh.Session) {
} }
cmd.Env = append(cmd.Env, fmt.Sprintf("TERM=%s", ptyReq.Term)) cmd.Env = append(cmd.Env, fmt.Sprintf("TERM=%s", ptyReq.Term))
cmd.Env = append(cmd.Env, fmt.Sprintf("PS1=%s", DefaultShellPrompt)) cmd.Env = append(cmd.Env, fmt.Sprintf("PS1=%s", defaultShellPrompt))
psuedoTTY, err := pty.Start(cmd) psuedoTTY, err := pty.Start(cmd)
if err != nil { if err != nil {
s.logger.WithError(err).Error("Failed to start pty session") s.logger.WithError(err).Error("Failed to start pty session")