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service_connector.go
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service_connector.go
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package ssh
import (
"fmt"
"io"
"reflect"
"strings"
"time"
validation "github.com/go-ozzo/ozzo-validation"
"golang.org/x/crypto/ssh"
"github.com/cyberark/secretless-broker/pkg/secretless/log"
"github.com/cyberark/secretless-broker/pkg/secretless/plugin/connector"
)
// ServerConfig is the configuration info for the target server
type ServerConfig struct {
Network string
Address string
ClientConfig ssh.ClientConfig
}
// ServiceConnector contains the configuration and channels
type ServiceConnector struct {
channels <-chan ssh.NewChannel
logger log.Logger
}
func (h *ServiceConnector) serverConfig(values map[string][]byte) (config ServerConfig, err error) {
keys := reflect.ValueOf(values).MapKeys()
h.logger.Debugf("SSH backend connection parameters: %s", keys)
config.Network = "tcp"
if address, ok := values["address"]; ok {
config.Address = string(address)
if !strings.Contains(config.Address, ":") {
config.Address = config.Address + ":22"
}
}
// XXX: Should this be the user that the client was trying to connect as?
config.ClientConfig.User = "root"
if user, ok := values["user"]; ok {
config.ClientConfig.User = string(user)
}
h.logger.Debugf("Trying to connect with user: %s", config.ClientConfig.User)
if hostKeyStr, ok := values["hostKey"]; ok {
var hostKey ssh.PublicKey
if hostKey, err = ssh.ParsePublicKey([]byte(hostKeyStr)); err != nil {
h.logger.Debugf("Unable to parse public key: %v", err)
return
}
config.ClientConfig.HostKeyCallback = ssh.FixedHostKey(hostKey)
} else {
h.logger.Warnf("No SSH hostKey specified. Secretless will accept any backend host key!")
config.ClientConfig.HostKeyCallback = ssh.InsecureIgnoreHostKey()
}
if privateKeyStr, ok := values["privateKey"]; ok {
var signer ssh.Signer
if signer, err = ssh.ParsePrivateKey([]byte(privateKeyStr)); err != nil {
h.logger.Debugf("Unable to parse private key: %v", err)
return
}
config.ClientConfig.Auth = []ssh.AuthMethod{
ssh.PublicKeys(signer),
}
}
return
}
// Connect opens the connection to the target server and proxies requests
func (h *ServiceConnector) Connect(
credentialValuesByID connector.CredentialValuesByID,
) error {
var err error
var serverConfig ServerConfig
var server ssh.Conn
errors := validation.Errors{}
for _, credential := range [...]string{"address", "privateKey"} {
if _, hasCredential := credentialValuesByID[credential]; !hasCredential {
errors[credential] = fmt.Errorf("must have credential '%s'", credential)
}
}
if err := errors.Filter(); err != nil {
return err
}
if serverConfig, err = h.serverConfig(credentialValuesByID); err != nil {
return fmt.Errorf("could not resolve server config: '%s'", err)
}
if server, err = ssh.Dial(serverConfig.Network, serverConfig.Address, &serverConfig.ClientConfig); err != nil {
return fmt.Errorf("failed to dial SSH backend '%s': %s", serverConfig.Address, err)
}
// Service the incoming Channel channel.
for newChannel := range h.channels {
serverChannel, serverRequests, err := server.OpenChannel(newChannel.ChannelType(), newChannel.ExtraData())
if err != nil {
sshError := err.(*ssh.OpenChannelError)
if err := newChannel.Reject(sshError.Reason, sshError.Message); err != nil {
h.logger.Errorf("Failed to send new channel rejection : %s", err)
}
return err
}
clientChannel, clientRequests, err := newChannel.Accept()
if err != nil {
h.logger.Errorf("Failed to accept client channel : %s", err)
serverChannel.Close()
return err
}
go func() {
for clientRequest := range clientRequests {
h.logger.Debugf("Client request : %s", clientRequest.Type)
ok, err := serverChannel.SendRequest(clientRequest.Type, clientRequest.WantReply, clientRequest.Payload)
if err != nil {
h.logger.Warnf("Failed to send client request to server channel : %s", err)
}
if clientRequest.WantReply {
h.logger.Debugf("Server reply is %v", ok)
}
}
}()
go func() {
for serverRequest := range serverRequests {
h.logger.Debugf("Server request : %s", serverRequest.Type)
ok, err := clientChannel.SendRequest(serverRequest.Type, serverRequest.WantReply, serverRequest.Payload)
if err != nil {
h.logger.Debugf("WARN: Failed to send server request to client channel : %s", err)
}
if serverRequest.WantReply {
h.logger.Debugf("Client reply is %v", ok)
}
}
}()
// This delay is to prevent closing of channels on the other side
// too early when we receive an EOF but have not had the chance to
// pass that on to the client/server.
// TODO: Maybe use a better logic for handling EOF conditions
softDelay := time.Second * 2
go func() {
for {
data := make([]byte, 1024)
len, err := clientChannel.Read(data)
if err == io.EOF {
h.logger.Debugf("Client channel is closed")
time.Sleep(softDelay)
serverChannel.Close()
return
}
_, err = serverChannel.Write(data[0:len])
if err != nil {
h.logger.Debugf("Error writing %d bytes to server channel : %s", len, err)
}
}
}()
go func() {
for {
data := make([]byte, 1024)
len, err := serverChannel.Read(data)
if err == io.EOF {
h.logger.Debugf("Server channel is closed")
time.Sleep(softDelay)
clientChannel.Close()
return
}
_, err = clientChannel.Write(data[0:len])
if err != nil {
h.logger.Debugf("Error writing %d bytes to client channel : %s", len, err)
}
}
}()
}
return nil
}