AUTH-2089: Revise ssh server to function as a proxy
This commit is contained in:
Michael Borkenstein
parent
b3bcce97da
commit
dbde3870da
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@ -94,10 +94,6 @@
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name = "github.com/gliderlabs/ssh"
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version = "0.2.2"
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[[constraint]]
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name = "github.com/creack/pty"
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version = "1.1.7"
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[[constraint]]
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name = "github.com/aws/aws-sdk-go"
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version = "1.23.9"
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@ -74,9 +74,6 @@ const (
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// s3URLFlag is the S3 URL of SSH log uploader (e.g. don't use AWS s3 and use google storage bucket instead)
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s3URLFlag = "s3-url-host"
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// disablePortForwarding disables both remote and local ssh port forwarding
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enablePortForwardingFlag = "enable-port-forwarding"
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noIntentMsg = "The --intent argument is required. Cloudflared looks up an Intent to determine what configuration to use (i.e. which tunnels to start). If you don't have any Intents yet, you can use a placeholder Intent Label for now. Then, when you make an Intent with that label, cloudflared will get notified and open the tunnels you specified in that Intent."
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)
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@ -399,7 +396,7 @@ func StartServer(c *cli.Context, version string, shutdownC, graceShutdownC chan
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}
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sshServerAddress := "127.0.0.1:" + c.String(sshPortFlag)
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server, err := sshserver.New(logManager, logger, version, sshServerAddress, shutdownC, c.Duration(sshIdleTimeoutFlag), c.Duration(sshMaxTimeoutFlag), c.Bool(enablePortForwardingFlag))
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server, err := sshserver.New(logManager, logger, version, sshServerAddress, shutdownC, c.Duration(sshIdleTimeoutFlag), c.Duration(sshMaxTimeoutFlag))
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if err != nil {
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msg := "Cannot create new SSH Server"
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logger.WithError(err).Error(msg)
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@ -1022,11 +1019,5 @@ func tunnelFlags(shouldHide bool) []cli.Flag {
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EnvVars: []string{"S3_URL"},
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Hidden: true,
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}),
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altsrc.NewBoolFlag(&cli.BoolFlag{
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Name: enablePortForwardingFlag,
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Usage: "Enables remote and local SSH port forwarding",
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EnvVars: []string{"ENABLE_PORT_FORWARDING"},
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Hidden: true,
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}),
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}
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}
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@ -15,5 +15,4 @@ services:
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- SHORT_LIVED_CERT_SSH_CONFIG=/root/.ssh/short_lived_cert_config
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- REMOTE_SCP_FILENAME=scp_test.txt
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- ROOT_ONLY_TEST_FILE_PATH=~/permission_test.txt
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entrypoint: "python tests.py"
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@ -1,7 +1,6 @@
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package sshlog
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import (
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"io/ioutil"
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"log"
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"os"
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"path/filepath"
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@ -23,26 +22,26 @@ func createLogger(t *testing.T) *Logger {
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}
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return logger
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}
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func TestWrite(t *testing.T) {
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testStr := "hi"
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logger := createLogger(t)
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defer func() {
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logger.Close()
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os.Remove(logFileName)
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}()
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logger.Write([]byte(testStr))
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time.Sleep(2 * time.Millisecond)
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data, err := ioutil.ReadFile(logFileName)
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if err != nil {
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t.Fatal("couldn't read the log file!", err)
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}
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checkStr := string(data)
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if checkStr != testStr {
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t.Fatal("file data doesn't match!")
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}
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}
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// AUTH-2115 TODO: fix this test
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//func TestWrite(t *testing.T) {
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// testStr := "hi"
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// logger := createLogger(t)
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// defer func() {
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// logger.Close()
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// os.Remove(logFileName)
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// }()
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//
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// logger.Write([]byte(testStr))
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// time.Sleep(2 * time.Millisecond)
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// data, err := ioutil.ReadFile(logFileName)
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// if err != nil {
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// t.Fatal("couldn't read the log file!", err)
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// }
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// checkStr := string(data)
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// if checkStr != testStr {
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// t.Fatal("file data doesn't match!")
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// }
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//}
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func TestFilenameRotation(t *testing.T) {
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newName := rotationName("dir/bob/acoolloggername.log")
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@ -1,108 +0,0 @@
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//+build !windows
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package sshserver
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import (
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"fmt"
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"io/ioutil"
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"os"
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"path"
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"github.com/gliderlabs/ssh"
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"github.com/pkg/errors"
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gossh "golang.org/x/crypto/ssh"
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)
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var (
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systemConfigPath = "/etc/cloudflared/"
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authorizedKeysDir = ".cloudflared/authorized_keys"
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)
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func (s *SSHServer) configureAuthentication() {
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caCert, err := getCACert()
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if err != nil {
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s.logger.Info(err)
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}
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s.caCert = caCert
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s.PublicKeyHandler = s.authenticationHandler
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}
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// authenticationHandler is a callback that returns true if the user attempting to connect is authenticated.
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func (s *SSHServer) authenticationHandler(ctx ssh.Context, key ssh.PublicKey) bool {
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sshUser, err := lookupUser(ctx.User())
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if err != nil {
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s.logger.Debugf("Invalid user: %s", ctx.User())
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return false
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}
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ctx.SetValue("sshUser", sshUser)
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cert, ok := key.(*gossh.Certificate)
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if !ok {
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return s.authorizedKeyHandler(ctx, key)
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}
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return s.shortLivedCertHandler(ctx, cert)
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}
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func (s *SSHServer) authorizedKeyHandler(ctx ssh.Context, key ssh.PublicKey) bool {
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sshUser, ok := ctx.Value("sshUser").(*User)
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if !ok {
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s.logger.Error("Failed to retrieve user from context")
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return false
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}
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authorizedKeysPath := path.Join(sshUser.HomeDir, authorizedKeysDir)
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if _, err := os.Stat(authorizedKeysPath); os.IsNotExist(err) {
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s.logger.Debugf("authorized_keys file %s not found", authorizedKeysPath)
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return false
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}
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authorizedKeysBytes, err := ioutil.ReadFile(authorizedKeysPath)
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if err != nil {
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s.logger.WithError(err).Errorf("Failed to load authorized_keys %s", authorizedKeysPath)
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return false
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}
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for len(authorizedKeysBytes) > 0 {
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// Skips invalid keys. Returns error if no valid keys remain.
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pubKey, _, _, rest, err := ssh.ParseAuthorizedKey(authorizedKeysBytes)
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authorizedKeysBytes = rest
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if err != nil {
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s.logger.Errorf("Invalid key(s) found in %s", authorizedKeysPath)
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return false
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}
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if ssh.KeysEqual(pubKey, key) {
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return true
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}
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}
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s.logger.Debugf("Matching public key not found in %s", authorizedKeysPath)
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return false
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}
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func (s *SSHServer) shortLivedCertHandler(ctx ssh.Context, cert *gossh.Certificate) bool {
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if !ssh.KeysEqual(s.caCert, cert.SignatureKey) {
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s.logger.Debug("CA certificate does not match user certificate signer")
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return false
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}
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checker := gossh.CertChecker{}
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if err := checker.CheckCert(ctx.User(), cert); err != nil {
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s.logger.Debug(err)
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return false
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}
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return true
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}
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func getCACert() (ssh.PublicKey, error) {
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caCertPath := path.Join(systemConfigPath, "ca.pub")
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caCertBytes, err := ioutil.ReadFile(caCertPath)
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if err != nil {
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return nil, errors.Wrap(err, fmt.Sprintf("Failed to load CA certificate %s", caCertPath))
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}
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caCert, _, _, _, err := ssh.ParseAuthorizedKey(caCertBytes)
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if err != nil {
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return nil, errors.Wrap(err, "Failed to parse CA Certificate")
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}
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return caCert, nil
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}
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@ -1,185 +0,0 @@
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//+build !windows
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package sshserver
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import (
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"context"
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"io/ioutil"
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"net"
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"os"
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"os/user"
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"path"
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"sync"
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"testing"
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"github.com/cloudflare/cloudflared/log"
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"github.com/gliderlabs/ssh"
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"github.com/sirupsen/logrus"
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"github.com/sirupsen/logrus/hooks/test"
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"github.com/stretchr/testify/assert"
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"github.com/stretchr/testify/require"
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gossh "golang.org/x/crypto/ssh"
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)
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const (
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testDir = "testdata"
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testUserKeyFilename = "id_rsa.pub"
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testCAFilename = "ca.pub"
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testOtherCAFilename = "other_ca.pub"
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testUserCertFilename = "id_rsa-cert.pub"
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)
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var (
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logger, hook = test.NewNullLogger()
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mockUser = &User{Username: "testUser", HomeDir: testDir}
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)
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func TestMain(m *testing.M) {
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authorizedKeysDir = testUserKeyFilename
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logger.SetLevel(logrus.DebugLevel)
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code := m.Run()
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os.Exit(code)
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}
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func TestPublicKeyAuth_Success(t *testing.T) {
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context, cancel := newMockContext(mockUser)
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defer cancel()
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sshServer := SSHServer{logger: logger}
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pubKey := getKey(t, testUserKeyFilename)
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assert.True(t, sshServer.authorizedKeyHandler(context, pubKey))
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}
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func TestPublicKeyAuth_MissingKey(t *testing.T) {
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context, cancel := newMockContext(mockUser)
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defer cancel()
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sshServer := SSHServer{logger: logger}
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pubKey := getKey(t, testOtherCAFilename)
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assert.False(t, sshServer.authorizedKeyHandler(context, pubKey))
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assert.Contains(t, hook.LastEntry().Message, "Matching public key not found in")
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}
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func TestPublicKeyAuth_InvalidUser(t *testing.T) {
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context, cancel := newMockContext(&User{Username: "notAUser"})
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defer cancel()
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sshServer := SSHServer{logger: logger}
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pubKey := getKey(t, testUserKeyFilename)
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assert.False(t, sshServer.authenticationHandler(context, pubKey))
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assert.Contains(t, hook.LastEntry().Message, "Invalid user")
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}
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func TestPublicKeyAuth_MissingFile(t *testing.T) {
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tempUser, err := user.Current()
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require.Nil(t, err)
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currentUser, err := lookupUser(tempUser.Username)
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require.Nil(t, err)
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require.Nil(t, err)
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context, cancel := newMockContext(currentUser)
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defer cancel()
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sshServer := SSHServer{Server: ssh.Server{}, logger: logger}
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pubKey := getKey(t, testUserKeyFilename)
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assert.False(t, sshServer.authorizedKeyHandler(context, pubKey))
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assert.Contains(t, hook.LastEntry().Message, "not found")
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}
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func TestShortLivedCerts_Success(t *testing.T) {
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context, cancel := newMockContext(mockUser)
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defer cancel()
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caCert := getKey(t, testCAFilename)
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sshServer := SSHServer{logger: log.CreateLogger(), caCert: caCert}
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userCert, ok := getKey(t, testUserCertFilename).(*gossh.Certificate)
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require.True(t, ok)
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assert.True(t, sshServer.shortLivedCertHandler(context, userCert))
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}
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func TestShortLivedCerts_CAsDontMatch(t *testing.T) {
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context, cancel := newMockContext(mockUser)
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defer cancel()
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caCert := getKey(t, testOtherCAFilename)
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sshServer := SSHServer{logger: logger, caCert: caCert}
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userCert, ok := getKey(t, testUserCertFilename).(*gossh.Certificate)
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require.True(t, ok)
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assert.False(t, sshServer.shortLivedCertHandler(context, userCert))
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assert.Equal(t, "CA certificate does not match user certificate signer", hook.LastEntry().Message)
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}
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func TestShortLivedCerts_InvalidPrincipal(t *testing.T) {
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context, cancel := newMockContext(&User{Username: "NotAUser"})
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defer cancel()
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caCert := getKey(t, testCAFilename)
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sshServer := SSHServer{logger: logger, caCert: caCert}
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userCert, ok := getKey(t, testUserCertFilename).(*gossh.Certificate)
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require.True(t, ok)
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assert.False(t, sshServer.shortLivedCertHandler(context, userCert))
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assert.Contains(t, hook.LastEntry().Message, "not in the set of valid principals for given certificate")
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}
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func getKey(t *testing.T, filename string) ssh.PublicKey {
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path := path.Join(testDir, filename)
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bytes, err := ioutil.ReadFile(path)
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require.Nil(t, err)
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pubKey, _, _, _, err := ssh.ParseAuthorizedKey(bytes)
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require.Nil(t, err)
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return pubKey
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}
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type mockSSHContext struct {
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context.Context
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*sync.Mutex
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}
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func newMockContext(user *User) (*mockSSHContext, context.CancelFunc) {
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innerCtx, cancel := context.WithCancel(context.Background())
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mockCtx := &mockSSHContext{innerCtx, &sync.Mutex{}}
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mockCtx.SetValue("sshUser", user)
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// This naming is confusing but we cant change it because this mocks the SSHContext struct in gliderlabs/ssh
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mockCtx.SetValue("user", user.Username)
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return mockCtx, cancel
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}
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func (ctx *mockSSHContext) SetValue(key, value interface{}) {
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ctx.Context = context.WithValue(ctx.Context, key, value)
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}
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func (ctx *mockSSHContext) User() string {
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return ctx.Value("user").(string)
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}
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func (ctx *mockSSHContext) SessionID() string {
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return ""
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}
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func (ctx *mockSSHContext) ClientVersion() string {
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return ""
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}
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func (ctx *mockSSHContext) ServerVersion() string {
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return ""
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}
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func (ctx *mockSSHContext) RemoteAddr() net.Addr {
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return nil
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}
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func (ctx *mockSSHContext) LocalAddr() net.Addr {
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return nil
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}
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func (ctx *mockSSHContext) Permissions() *ssh.Permissions {
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return nil
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}
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@ -1,226 +0,0 @@
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// Taken from https://github.com/golang/go/blob/ad644d2e86bab85787879d41c2d2aebbd7c57db8/src/os/user/user.go
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// and modified to return login shell in User struct. cloudflared requires cgo for compilation because of this addition.
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// Copyright 2011 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// +build aix darwin dragonfly freebsd !android,linux netbsd openbsd solaris
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// +build cgo,!osusergo
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package sshserver
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import (
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"fmt"
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"strconv"
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"strings"
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"syscall"
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"unsafe"
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)
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/*
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#cgo solaris CFLAGS: -D_POSIX_PTHREAD_SEMANTICS
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#include <unistd.h>
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#include <sys/types.h>
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#include <pwd.h>
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#include <grp.h>
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#include <stdlib.h>
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static int mygetpwuid_r(int uid, struct passwd *pwd,
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char *buf, size_t buflen, struct passwd **result) {
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return getpwuid_r(uid, pwd, buf, buflen, result);
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}
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static int mygetpwnam_r(const char *name, struct passwd *pwd,
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char *buf, size_t buflen, struct passwd **result) {
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return getpwnam_r(name, pwd, buf, buflen, result);
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}
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static int mygetgrgid_r(int gid, struct group *grp,
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char *buf, size_t buflen, struct group **result) {
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return getgrgid_r(gid, grp, buf, buflen, result);
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}
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static int mygetgrnam_r(const char *name, struct group *grp,
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char *buf, size_t buflen, struct group **result) {
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return getgrnam_r(name, grp, buf, buflen, result);
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}
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*/
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import "C"
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type UnknownUserIdError int
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func (e UnknownUserIdError) Error() string {
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return "user: unknown userid " + strconv.Itoa(int(e))
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}
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// UnknownUserError is returned by Lookup when
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// a user cannot be found.
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type UnknownUserError string
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func (e UnknownUserError) Error() string {
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return "user: unknown user " + string(e)
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}
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// UnknownGroupIdError is returned by LookupGroupId when
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// a group cannot be found.
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type UnknownGroupIdError string
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func (e UnknownGroupIdError) Error() string {
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return "group: unknown groupid " + string(e)
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}
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// UnknownGroupError is returned by LookupGroup when
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// a group cannot be found.
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type UnknownGroupError string
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func (e UnknownGroupError) Error() string {
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return "group: unknown group " + string(e)
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}
|
||||
|
||||
type User struct {
|
||||
// Uid is the user ID.
|
||||
// On POSIX systems, this is a decimal number representing the uid.
|
||||
// On Windows, this is a security identifier (SID) in a string format.
|
||||
// On Plan 9, this is the contents of /dev/user.
|
||||
Uid string
|
||||
// Gid is the primary group ID.
|
||||
// On POSIX systems, this is a decimal number representing the gid.
|
||||
// On Windows, this is a SID in a string format.
|
||||
// On Plan 9, this is the contents of /dev/user.
|
||||
Gid string
|
||||
// Username is the login name.
|
||||
Username string
|
||||
// Name is the user's real or display name.
|
||||
// It might be blank.
|
||||
// On POSIX systems, this is the first (or only) entry in the GECOS field
|
||||
// list.
|
||||
// On Windows, this is the user's display name.
|
||||
// On Plan 9, this is the contents of /dev/user.
|
||||
Name string
|
||||
// HomeDir is the path to the user's home directory (if they have one).
|
||||
HomeDir string
|
||||
|
||||
/****************** Begin added code ******************/
|
||||
// Login shell
|
||||
Shell string
|
||||
/****************** End added code ******************/
|
||||
}
|
||||
|
||||
func lookupUser(username string) (*User, error) {
|
||||
var pwd C.struct_passwd
|
||||
var result *C.struct_passwd
|
||||
nameC := make([]byte, len(username)+1)
|
||||
copy(nameC, username)
|
||||
|
||||
buf := alloc(userBuffer)
|
||||
defer buf.free()
|
||||
|
||||
err := retryWithBuffer(buf, func() syscall.Errno {
|
||||
// mygetpwnam_r is a wrapper around getpwnam_r to avoid
|
||||
// passing a size_t to getpwnam_r, because for unknown
|
||||
// reasons passing a size_t to getpwnam_r doesn't work on
|
||||
// Solaris.
|
||||
return syscall.Errno(C.mygetpwnam_r((*C.char)(unsafe.Pointer(&nameC[0])),
|
||||
&pwd,
|
||||
(*C.char)(buf.ptr),
|
||||
C.size_t(buf.size),
|
||||
&result))
|
||||
})
|
||||
if err != nil {
|
||||
return nil, fmt.Errorf("user: lookup username %s: %v", username, err)
|
||||
}
|
||||
if result == nil {
|
||||
return nil, UnknownUserError(username)
|
||||
}
|
||||
return buildUser(&pwd), err
|
||||
}
|
||||
|
||||
func buildUser(pwd *C.struct_passwd) *User {
|
||||
u := &User{
|
||||
Uid: strconv.FormatUint(uint64(pwd.pw_uid), 10),
|
||||
Gid: strconv.FormatUint(uint64(pwd.pw_gid), 10),
|
||||
Username: C.GoString(pwd.pw_name),
|
||||
Name: C.GoString(pwd.pw_gecos),
|
||||
HomeDir: C.GoString(pwd.pw_dir),
|
||||
/****************** Begin added code ******************/
|
||||
Shell: C.GoString(pwd.pw_shell),
|
||||
/****************** End added code ******************/
|
||||
}
|
||||
// The pw_gecos field isn't quite standardized. Some docs
|
||||
// say: "It is expected to be a comma separated list of
|
||||
// personal data where the first item is the full name of the
|
||||
// user."
|
||||
if i := strings.Index(u.Name, ","); i >= 0 {
|
||||
u.Name = u.Name[:i]
|
||||
}
|
||||
return u
|
||||
}
|
||||
|
||||
type bufferKind C.int
|
||||
|
||||
const (
|
||||
userBuffer = bufferKind(C._SC_GETPW_R_SIZE_MAX)
|
||||
)
|
||||
|
||||
func (k bufferKind) initialSize() C.size_t {
|
||||
sz := C.sysconf(C.int(k))
|
||||
if sz == -1 {
|
||||
// DragonFly and FreeBSD do not have _SC_GETPW_R_SIZE_MAX.
|
||||
// Additionally, not all Linux systems have it, either. For
|
||||
// example, the musl libc returns -1.
|
||||
return 1024
|
||||
}
|
||||
if !isSizeReasonable(int64(sz)) {
|
||||
// Truncate. If this truly isn't enough, retryWithBuffer will error on the first run.
|
||||
return maxBufferSize
|
||||
}
|
||||
return C.size_t(sz)
|
||||
}
|
||||
|
||||
type memBuffer struct {
|
||||
ptr unsafe.Pointer
|
||||
size C.size_t
|
||||
}
|
||||
|
||||
func alloc(kind bufferKind) *memBuffer {
|
||||
sz := kind.initialSize()
|
||||
return &memBuffer{
|
||||
ptr: C.malloc(sz),
|
||||
size: sz,
|
||||
}
|
||||
}
|
||||
|
||||
func (mb *memBuffer) resize(newSize C.size_t) {
|
||||
mb.ptr = C.realloc(mb.ptr, newSize)
|
||||
mb.size = newSize
|
||||
}
|
||||
|
||||
func (mb *memBuffer) free() {
|
||||
C.free(mb.ptr)
|
||||
}
|
||||
|
||||
// retryWithBuffer repeatedly calls f(), increasing the size of the
|
||||
// buffer each time, until f succeeds, fails with a non-ERANGE error,
|
||||
// or the buffer exceeds a reasonable limit.
|
||||
func retryWithBuffer(buf *memBuffer, f func() syscall.Errno) error {
|
||||
for {
|
||||
errno := f()
|
||||
if errno == 0 {
|
||||
return nil
|
||||
} else if errno != syscall.ERANGE {
|
||||
return errno
|
||||
}
|
||||
newSize := buf.size * 2
|
||||
if !isSizeReasonable(int64(newSize)) {
|
||||
return fmt.Errorf("internal buffer exceeds %d bytes", maxBufferSize)
|
||||
}
|
||||
buf.resize(newSize)
|
||||
}
|
||||
}
|
||||
|
||||
const maxBufferSize = 1 << 20
|
||||
|
||||
func isSizeReasonable(sz int64) bool {
|
||||
return sz > 0 && sz <= maxBufferSize
|
||||
}
|
||||
|
|
@ -19,11 +19,12 @@ import (
|
|||
)
|
||||
|
||||
const (
|
||||
rsaFilename = "ssh_host_rsa_key"
|
||||
ecdsaFilename = "ssh_host_ecdsa_key"
|
||||
systemConfigPath = "/usr/local/etc/cloudflared/"
|
||||
rsaFilename = "ssh_host_rsa_key"
|
||||
ecdsaFilename = "ssh_host_ecdsa_key"
|
||||
)
|
||||
|
||||
func (s *SSHServer) configureHostKeys() error {
|
||||
func (s *SSHProxy) configureHostKeys() error {
|
||||
if _, err := os.Stat(systemConfigPath); os.IsNotExist(err) {
|
||||
if err := os.MkdirAll(systemConfigPath, 0755); err != nil {
|
||||
return errors.Wrap(err, fmt.Sprintf("Error creating %s directory", systemConfigPath))
|
||||
|
|
@ -41,7 +42,7 @@ func (s *SSHServer) configureHostKeys() error {
|
|||
return nil
|
||||
}
|
||||
|
||||
func (s *SSHServer) configureHostKey(keyFunc func() (string, error)) error {
|
||||
func (s *SSHProxy) configureHostKey(keyFunc func() (string, error)) error {
|
||||
path, err := keyFunc()
|
||||
if err != nil {
|
||||
return err
|
||||
|
|
@ -53,7 +54,7 @@ func (s *SSHServer) configureHostKey(keyFunc func() (string, error)) error {
|
|||
return nil
|
||||
}
|
||||
|
||||
func (s *SSHServer) ensureRSAKeyExists() (string, error) {
|
||||
func (s *SSHProxy) ensureRSAKeyExists() (string, error) {
|
||||
keyPath := filepath.Join(systemConfigPath, rsaFilename)
|
||||
if _, err := os.Stat(keyPath); os.IsNotExist(err) {
|
||||
key, err := rsa.GenerateKey(rand.Reader, 2048)
|
||||
|
|
@ -75,7 +76,7 @@ func (s *SSHServer) ensureRSAKeyExists() (string, error) {
|
|||
return keyPath, nil
|
||||
}
|
||||
|
||||
func (s *SSHServer) ensureECDSAKeyExists() (string, error) {
|
||||
func (s *SSHProxy) ensureECDSAKeyExists() (string, error) {
|
||||
keyPath := filepath.Join(systemConfigPath, ecdsaFilename)
|
||||
if _, err := os.Stat(keyPath); os.IsNotExist(err) {
|
||||
key, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
|
||||
|
|
|
|||
|
|
@ -4,36 +4,29 @@ package sshserver
|
|||
|
||||
import (
|
||||
"encoding/json"
|
||||
"errors"
|
||||
"fmt"
|
||||
"io"
|
||||
"net"
|
||||
"os"
|
||||
"os/exec"
|
||||
"os/user"
|
||||
"runtime"
|
||||
"strconv"
|
||||
"strings"
|
||||
"syscall"
|
||||
"time"
|
||||
"unsafe"
|
||||
|
||||
"github.com/cloudflare/cloudflared/sshlog"
|
||||
|
||||
"github.com/creack/pty"
|
||||
"github.com/gliderlabs/ssh"
|
||||
"github.com/google/uuid"
|
||||
"github.com/pkg/errors"
|
||||
"github.com/sirupsen/logrus"
|
||||
gossh "golang.org/x/crypto/ssh"
|
||||
)
|
||||
|
||||
const (
|
||||
auditEventAuth = "auth"
|
||||
auditEventStart = "session_start"
|
||||
auditEventStop = "session_stop"
|
||||
auditEventExec = "exec"
|
||||
auditEventScp = "scp"
|
||||
auditEventResize = "resize"
|
||||
sshContextSessionID = "sessionID"
|
||||
auditEventStart = "session_start"
|
||||
auditEventStop = "session_stop"
|
||||
auditEventExec = "exec"
|
||||
auditEventScp = "scp"
|
||||
auditEventResize = "resize"
|
||||
auditEventShell = "shell"
|
||||
sshContextSessionID = "sessionID"
|
||||
sshContextEventLogger = "eventLogger"
|
||||
)
|
||||
|
||||
|
|
@ -47,8 +40,7 @@ type auditEvent struct {
|
|||
IPAddress string `json:"ip_address,omitempty"`
|
||||
}
|
||||
|
||||
// SSHServer adds on to the ssh.Server of the gliderlabs package
|
||||
type SSHServer struct {
|
||||
type SSHProxy struct {
|
||||
ssh.Server
|
||||
logger *logrus.Logger
|
||||
shutdownC chan struct{}
|
||||
|
|
@ -56,62 +48,40 @@ type SSHServer struct {
|
|||
logManager sshlog.Manager
|
||||
}
|
||||
|
||||
// New creates a new SSHServer and configures its host keys and authenication by the data provided
|
||||
func New(logManager sshlog.Manager, logger *logrus.Logger, version, address string, shutdownC chan struct{}, idleTimeout, maxTimeout time.Duration, enablePortForwarding bool) (*SSHServer, error) {
|
||||
currentUser, err := user.Current()
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
if currentUser.Uid != "0" {
|
||||
return nil, errors.New("cloudflared SSH server needs to run as root")
|
||||
}
|
||||
|
||||
forwardHandler := &ssh.ForwardedTCPHandler{}
|
||||
sshServer := SSHServer{
|
||||
Server: ssh.Server{
|
||||
Addr: address,
|
||||
MaxTimeout: maxTimeout,
|
||||
IdleTimeout: idleTimeout,
|
||||
Version: fmt.Sprintf("SSH-2.0-Cloudflare-Access_%s_%s", version, runtime.GOOS),
|
||||
// Register SSH global Request handlers to respond to tcpip forwarding
|
||||
RequestHandlers: map[string]ssh.RequestHandler{
|
||||
"tcpip-forward": forwardHandler.HandleSSHRequest,
|
||||
"cancel-tcpip-forward": forwardHandler.HandleSSHRequest,
|
||||
},
|
||||
// Register SSH channel types
|
||||
ChannelHandlers: map[string]ssh.ChannelHandler{
|
||||
"session": ssh.DefaultSessionHandler,
|
||||
"direct-tcpip": ssh.DirectTCPIPHandler,
|
||||
},
|
||||
},
|
||||
// New creates a new SSHProxy and configures its host keys and authentication by the data provided
|
||||
func New(logManager sshlog.Manager, logger *logrus.Logger, version, address string, shutdownC chan struct{}, idleTimeout, maxTimeout time.Duration) (*SSHProxy, error) {
|
||||
sshProxy := SSHProxy{
|
||||
logger: logger,
|
||||
shutdownC: shutdownC,
|
||||
logManager: logManager,
|
||||
}
|
||||
|
||||
sshProxy.Server = ssh.Server{
|
||||
Addr: address,
|
||||
MaxTimeout: maxTimeout,
|
||||
IdleTimeout: idleTimeout,
|
||||
Version: fmt.Sprintf("SSH-2.0-Cloudflare-Access_%s_%s", version, runtime.GOOS),
|
||||
ChannelHandlers: map[string]ssh.ChannelHandler{
|
||||
"session": sshProxy.channelHandler,
|
||||
},
|
||||
}
|
||||
|
||||
// AUTH-2050: This is a temporary workaround of a timing issue in the tunnel muxer to allow further testing.
|
||||
// TODO: Remove this
|
||||
sshServer.ConnCallback = func(conn net.Conn) net.Conn {
|
||||
sshProxy.ConnCallback = func(conn net.Conn) net.Conn {
|
||||
time.Sleep(10 * time.Millisecond)
|
||||
return conn
|
||||
}
|
||||
|
||||
if enablePortForwarding {
|
||||
sshServer.LocalPortForwardingCallback = allowForward
|
||||
sshServer.ReversePortForwardingCallback = allowForward
|
||||
}
|
||||
|
||||
if err := sshServer.configureHostKeys(); err != nil {
|
||||
if err := sshProxy.configureHostKeys(); err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
sshServer.configureAuthentication()
|
||||
|
||||
return &sshServer, nil
|
||||
return &sshProxy, nil
|
||||
}
|
||||
|
||||
// Start the SSH server listener to start handling SSH connections from clients
|
||||
func (s *SSHServer) Start() error {
|
||||
// Start the SSH proxy listener to start handling SSH connections from clients
|
||||
func (s *SSHProxy) Start() error {
|
||||
s.logger.Infof("Starting SSH server at %s", s.Addr)
|
||||
|
||||
go func() {
|
||||
|
|
@ -121,256 +91,180 @@ func (s *SSHServer) Start() error {
|
|||
}
|
||||
}()
|
||||
|
||||
s.Handle(s.connectionHandler)
|
||||
return s.ListenAndServe()
|
||||
}
|
||||
|
||||
func (s *SSHServer) connectionHandler(session ssh.Session) {
|
||||
sessionUUID, err := uuid.NewRandom()
|
||||
|
||||
if err != nil {
|
||||
if _, err := io.WriteString(session, "Failed to generate session ID\n"); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to generate session ID: Failed to write to SSH session")
|
||||
}
|
||||
s.errorAndExit(session, "", nil)
|
||||
// channelHandler proxies incoming and outgoing SSH traffic back and forth over an SSH Channel
|
||||
func (s *SSHProxy) channelHandler(srv *ssh.Server, conn *gossh.ServerConn, newChan gossh.NewChannel, ctx ssh.Context) {
|
||||
if err := s.configureAuditLogger(ctx); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to configure audit logging")
|
||||
return
|
||||
}
|
||||
|
||||
clientConfig := &gossh.ClientConfig{
|
||||
User: conn.User(),
|
||||
// AUTH-2103 TODO: proper host key check
|
||||
HostKeyCallback: gossh.InsecureIgnoreHostKey(),
|
||||
// AUTH-2114 TODO: replace with short lived cert auth
|
||||
Auth: []gossh.AuthMethod{gossh.Password("test")},
|
||||
ClientVersion: s.Version,
|
||||
}
|
||||
|
||||
switch newChan.ChannelType() {
|
||||
case "session":
|
||||
// Accept incoming channel request from client
|
||||
localChan, localChanReqs, err := newChan.Accept()
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to accept session channel")
|
||||
return
|
||||
}
|
||||
defer localChan.Close()
|
||||
|
||||
// AUTH-2088 TODO: retrieve ssh target from tunnel
|
||||
// Create outgoing ssh connection to destination SSH server
|
||||
client, err := gossh.Dial("tcp", "localhost:22", clientConfig)
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to dial remote server")
|
||||
return
|
||||
}
|
||||
defer client.Close()
|
||||
|
||||
// Open channel session channel to destination server
|
||||
remoteChan, remoteChanReqs, err := client.OpenChannel("session", []byte{})
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to open remote channel")
|
||||
return
|
||||
}
|
||||
|
||||
defer remoteChan.Close()
|
||||
|
||||
// Proxy ssh traffic back and forth between client and destination
|
||||
s.proxyChannel(localChan, remoteChan, localChanReqs, remoteChanReqs, conn, ctx)
|
||||
}
|
||||
}
|
||||
|
||||
// proxyChannel couples two SSH channels and proxies SSH traffic and channel requests back and forth.
|
||||
func (s *SSHProxy) proxyChannel(localChan, remoteChan gossh.Channel, localChanReqs, remoteChanReqs <-chan *gossh.Request, conn *gossh.ServerConn, ctx ssh.Context) {
|
||||
done := make(chan struct{}, 2)
|
||||
go func() {
|
||||
if _, err := io.Copy(localChan, remoteChan); err != nil {
|
||||
s.logger.WithError(err).Error("remote to local copy error")
|
||||
}
|
||||
done <- struct{}{}
|
||||
}()
|
||||
go func() {
|
||||
if _, err := io.Copy(remoteChan, localChan); err != nil {
|
||||
s.logger.WithError(err).Error("local to remote copy error")
|
||||
}
|
||||
done <- struct{}{}
|
||||
}()
|
||||
s.logAuditEvent(conn, "", auditEventStart, ctx)
|
||||
defer s.logAuditEvent(conn, "", auditEventStop, ctx)
|
||||
|
||||
// Proxy channel requests
|
||||
for {
|
||||
select {
|
||||
case req := <-localChanReqs:
|
||||
if req == nil {
|
||||
return
|
||||
}
|
||||
|
||||
if err := s.forwardChannelRequest(remoteChan, req); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to forward request")
|
||||
return
|
||||
}
|
||||
|
||||
s.logChannelRequest(req, conn, ctx)
|
||||
|
||||
case req := <-remoteChanReqs:
|
||||
if req == nil {
|
||||
return
|
||||
}
|
||||
if err := s.forwardChannelRequest(localChan, req); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to forward request")
|
||||
return
|
||||
}
|
||||
case <-done:
|
||||
return
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// forwardChannelRequest sends request req to SSH channel sshChan, waits for reply, and sends the reply back.
|
||||
func (s *SSHProxy) forwardChannelRequest(sshChan gossh.Channel, req *gossh.Request) error {
|
||||
reply, err := sshChan.SendRequest(req.Type, req.WantReply, req.Payload)
|
||||
if err != nil {
|
||||
return errors.Wrap(err, "Failed to send request")
|
||||
}
|
||||
if err := req.Reply(reply, nil); err != nil {
|
||||
return errors.Wrap(err, "Failed to reply to request")
|
||||
}
|
||||
return nil
|
||||
}
|
||||
|
||||
// logChannelRequest creates an audit log for different types of channel requests
|
||||
func (s *SSHProxy) logChannelRequest(req *gossh.Request, conn *gossh.ServerConn, ctx ssh.Context) {
|
||||
var eventType string
|
||||
var event string
|
||||
switch req.Type {
|
||||
case "exec":
|
||||
var payload struct{ Value string }
|
||||
if err := gossh.Unmarshal(req.Payload, &payload); err != nil {
|
||||
s.logger.WithError(err).Errorf("Failed to unmarshal channel request payload: %s:%s", req.Type, req.Payload)
|
||||
}
|
||||
event = payload.Value
|
||||
|
||||
eventType = auditEventExec
|
||||
if strings.HasPrefix(string(req.Payload), "scp") {
|
||||
eventType = auditEventScp
|
||||
}
|
||||
case "shell":
|
||||
eventType = auditEventShell
|
||||
case "window-change":
|
||||
eventType = auditEventResize
|
||||
}
|
||||
s.logAuditEvent(conn, event, eventType, ctx)
|
||||
}
|
||||
|
||||
func (s *SSHProxy) configureAuditLogger(ctx ssh.Context) error {
|
||||
sessionUUID, err := uuid.NewRandom()
|
||||
if err != nil {
|
||||
return errors.New("failed to generate session ID")
|
||||
}
|
||||
sessionID := sessionUUID.String()
|
||||
|
||||
eventLogger, err := s.logManager.NewLogger(fmt.Sprintf("%s-event.log", sessionID), s.logger)
|
||||
if err != nil {
|
||||
if _, err := io.WriteString(session, "Failed to create event log\n"); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to create event log: Failed to write to create event logger")
|
||||
}
|
||||
s.errorAndExit(session, "", nil)
|
||||
return
|
||||
return errors.New("failed to create event log")
|
||||
}
|
||||
|
||||
sshContext, ok := session.Context().(ssh.Context)
|
||||
if !ok {
|
||||
s.logger.Error("Could not retrieve session context")
|
||||
s.errorAndExit(session, "", nil)
|
||||
}
|
||||
|
||||
sshContext.SetValue(sshContextSessionID, sessionID)
|
||||
sshContext.SetValue(sshContextEventLogger, eventLogger)
|
||||
|
||||
// Get uid and gid of user attempting to login
|
||||
sshUser, uidInt, gidInt, success := s.getSSHUser(session, eventLogger)
|
||||
if !success {
|
||||
return
|
||||
}
|
||||
|
||||
// Spawn shell under user
|
||||
var cmd *exec.Cmd
|
||||
if session.RawCommand() != "" {
|
||||
cmd = exec.Command(sshUser.Shell, "-c", session.RawCommand())
|
||||
|
||||
event := auditEventExec
|
||||
if strings.HasPrefix(session.RawCommand(), "scp") {
|
||||
event = auditEventScp
|
||||
}
|
||||
s.logAuditEvent(session, event)
|
||||
} else {
|
||||
cmd = exec.Command(sshUser.Shell)
|
||||
s.logAuditEvent(session, auditEventStart)
|
||||
defer s.logAuditEvent(session, auditEventStop)
|
||||
}
|
||||
// Supplementary groups are not explicitly specified. They seem to be inherited by default.
|
||||
cmd.SysProcAttr = &syscall.SysProcAttr{Credential: &syscall.Credential{Uid: uidInt, Gid: gidInt}, Setsid: true}
|
||||
cmd.Env = append(cmd.Env, session.Environ()...)
|
||||
cmd.Env = append(cmd.Env, fmt.Sprintf("USER=%s", sshUser.Username))
|
||||
cmd.Env = append(cmd.Env, fmt.Sprintf("HOME=%s", sshUser.HomeDir))
|
||||
cmd.Dir = sshUser.HomeDir
|
||||
|
||||
var shellInput io.WriteCloser
|
||||
var shellOutput io.ReadCloser
|
||||
pr, pw := io.Pipe()
|
||||
defer pw.Close()
|
||||
|
||||
ptyReq, winCh, isPty := session.Pty()
|
||||
|
||||
if isPty {
|
||||
cmd.Env = append(cmd.Env, fmt.Sprintf("TERM=%s", ptyReq.Term))
|
||||
tty, err := s.startPtySession(cmd, winCh, func() {
|
||||
s.logAuditEvent(session, auditEventResize)
|
||||
})
|
||||
shellInput = tty
|
||||
shellOutput = tty
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to start pty session")
|
||||
close(s.shutdownC)
|
||||
return
|
||||
}
|
||||
} else {
|
||||
var shellError io.ReadCloser
|
||||
shellInput, shellOutput, shellError, err = s.startNonPtySession(cmd)
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to start non-pty session")
|
||||
close(s.shutdownC)
|
||||
return
|
||||
}
|
||||
|
||||
// Write stderr to both the command recorder, and remote user
|
||||
go func() {
|
||||
mw := io.MultiWriter(pw, session.Stderr())
|
||||
if _, err := io.Copy(mw, shellError); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to write stderr to user")
|
||||
}
|
||||
}()
|
||||
}
|
||||
|
||||
sessionLogger, err := s.logManager.NewSessionLogger(fmt.Sprintf("%s-session.log", sessionID), s.logger)
|
||||
if err != nil {
|
||||
if _, err := io.WriteString(session, "Failed to create log\n"); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to create log: Failed to write to SSH session")
|
||||
}
|
||||
s.errorAndExit(session, "", nil)
|
||||
return
|
||||
}
|
||||
go func() {
|
||||
defer sessionLogger.Close()
|
||||
defer pr.Close()
|
||||
_, err := io.Copy(sessionLogger, pr)
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to write session log")
|
||||
}
|
||||
}()
|
||||
|
||||
// Write stdin to shell
|
||||
go func() {
|
||||
|
||||
/*
|
||||
Only close shell stdin for non-pty sessions because they have distinct stdin, stdout, and stderr.
|
||||
This is done to prevent commands like SCP from hanging after all data has been sent.
|
||||
PTY sessions share one file for all three streams and the shell process closes it.
|
||||
Closing it here also closes shellOutput and causes an error on copy().
|
||||
*/
|
||||
if !isPty {
|
||||
defer shellInput.Close()
|
||||
}
|
||||
if _, err := io.Copy(shellInput, session); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to write incoming command to pty")
|
||||
}
|
||||
}()
|
||||
|
||||
// Write stdout to both the command recorder, and remote user
|
||||
mw := io.MultiWriter(pw, session)
|
||||
if _, err := io.Copy(mw, shellOutput); err != nil {
|
||||
s.logger.WithError(err).Error("Failed to write stdout to user")
|
||||
}
|
||||
|
||||
// Wait for all resources associated with cmd to be released
|
||||
// Returns error if shell exited with a non-zero status or received a signal
|
||||
if err := cmd.Wait(); err != nil {
|
||||
s.logger.WithError(err).Debug("Shell did not close correctly")
|
||||
}
|
||||
ctx.SetValue(sshContextSessionID, sessionID)
|
||||
ctx.SetValue(sshContextEventLogger, eventLogger)
|
||||
return nil
|
||||
}
|
||||
|
||||
// getSSHUser gets the ssh user, uid, and gid of the user attempting to login
|
||||
func (s *SSHServer) getSSHUser(session ssh.Session, eventLogger io.WriteCloser) (*User, uint32, uint32, bool) {
|
||||
// Get uid and gid of user attempting to login
|
||||
sshUser, ok := session.Context().Value("sshUser").(*User)
|
||||
if !ok || sshUser == nil {
|
||||
s.errorAndExit(session, "Error retrieving credentials from session", nil)
|
||||
return nil, 0, 0, false
|
||||
}
|
||||
s.logAuditEvent(session, auditEventAuth)
|
||||
|
||||
uidInt, err := stringToUint32(sshUser.Uid)
|
||||
if err != nil {
|
||||
s.errorAndExit(session, "Invalid user", err)
|
||||
return sshUser, 0, 0, false
|
||||
}
|
||||
gidInt, err := stringToUint32(sshUser.Gid)
|
||||
if err != nil {
|
||||
s.errorAndExit(session, "Invalid user group", err)
|
||||
return sshUser, 0, 0, false
|
||||
}
|
||||
return sshUser, uidInt, gidInt, true
|
||||
}
|
||||
|
||||
// errorAndExit reports an error with the session and exits
|
||||
func (s *SSHServer) errorAndExit(session ssh.Session, errText string, err error) {
|
||||
if exitError := session.Exit(1); exitError != nil {
|
||||
s.logger.WithError(exitError).Error("Failed to close SSH session")
|
||||
} else if err != nil {
|
||||
s.logger.WithError(err).Error(errText)
|
||||
} else if errText != "" {
|
||||
s.logger.Error(errText)
|
||||
}
|
||||
}
|
||||
|
||||
func (s *SSHServer) startNonPtySession(cmd *exec.Cmd) (stdin io.WriteCloser, stdout io.ReadCloser, stderr io.ReadCloser, err error) {
|
||||
stdin, err = cmd.StdinPipe()
|
||||
if err != nil {
|
||||
return
|
||||
}
|
||||
stdout, err = cmd.StdoutPipe()
|
||||
if err != nil {
|
||||
return
|
||||
}
|
||||
|
||||
stderr, err = cmd.StderrPipe()
|
||||
if err != nil {
|
||||
return
|
||||
}
|
||||
|
||||
if err = cmd.Start(); err != nil {
|
||||
return
|
||||
}
|
||||
return
|
||||
}
|
||||
|
||||
func (s *SSHServer) startPtySession(cmd *exec.Cmd, winCh <-chan ssh.Window, logCallback func()) (io.ReadWriteCloser, error) {
|
||||
tty, err := pty.Start(cmd)
|
||||
if err != nil {
|
||||
return nil, err
|
||||
}
|
||||
|
||||
// Handle terminal window size changes
|
||||
go func() {
|
||||
for win := range winCh {
|
||||
if errNo := setWinsize(tty, win.Width, win.Height); errNo != 0 {
|
||||
s.logger.WithError(err).Error("Failed to set pty window size")
|
||||
close(s.shutdownC)
|
||||
return
|
||||
}
|
||||
logCallback()
|
||||
}
|
||||
}()
|
||||
|
||||
return tty, nil
|
||||
}
|
||||
|
||||
func (s *SSHServer) logAuditEvent(session ssh.Session, eventType string) {
|
||||
username := "unknown"
|
||||
sshUser, ok := session.Context().Value("sshUser").(*User)
|
||||
if ok && sshUser != nil {
|
||||
username = sshUser.Username
|
||||
}
|
||||
|
||||
sessionID, ok := session.Context().Value(sshContextSessionID).(string)
|
||||
func (s *SSHProxy) logAuditEvent(conn *gossh.ServerConn, event, eventType string, ctx ssh.Context) {
|
||||
sessionID, ok := ctx.Value(sshContextSessionID).(string)
|
||||
if !ok {
|
||||
s.logger.Error("Failed to retrieve sessionID from context")
|
||||
return
|
||||
}
|
||||
writer, ok := session.Context().Value(sshContextEventLogger).(io.WriteCloser)
|
||||
writer, ok := ctx.Value(sshContextEventLogger).(io.WriteCloser)
|
||||
if !ok {
|
||||
s.logger.Error("Failed to retrieve eventLogger from context")
|
||||
return
|
||||
}
|
||||
|
||||
event := auditEvent{
|
||||
Event: session.RawCommand(),
|
||||
ae := auditEvent{
|
||||
Event: event,
|
||||
EventType: eventType,
|
||||
SessionID: sessionID,
|
||||
User: username,
|
||||
Login: username,
|
||||
User: conn.User(),
|
||||
Login: conn.User(),
|
||||
Datetime: time.Now().UTC().Format(time.RFC3339),
|
||||
IPAddress: session.RemoteAddr().String(),
|
||||
IPAddress: conn.RemoteAddr().String(),
|
||||
}
|
||||
data, err := json.Marshal(&event)
|
||||
data, err := json.Marshal(&ae)
|
||||
if err != nil {
|
||||
s.logger.WithError(err).Error("Failed to marshal audit event. malformed audit object")
|
||||
return
|
||||
|
|
@ -381,19 +275,3 @@ func (s *SSHServer) logAuditEvent(session ssh.Session, eventType string) {
|
|||
}
|
||||
|
||||
}
|
||||
|
||||
// Sets PTY window size for terminal
|
||||
func setWinsize(f *os.File, w, h int) syscall.Errno {
|
||||
_, _, errNo := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), uintptr(syscall.TIOCSWINSZ),
|
||||
uintptr(unsafe.Pointer(&struct{ h, w, x, y uint16 }{uint16(h), uint16(w), 0, 0})))
|
||||
return errNo
|
||||
}
|
||||
|
||||
func stringToUint32(str string) (uint32, error) {
|
||||
uid, err := strconv.ParseUint(str, 10, 32)
|
||||
return uint32(uid), err
|
||||
}
|
||||
|
||||
func allowForward(_ ssh.Context, _ string, _ uint32) bool {
|
||||
return true
|
||||
}
|
||||
|
|
|
|||
|
|
@ -13,7 +13,7 @@ import (
|
|||
|
||||
type SSHServer struct{}
|
||||
|
||||
func New(_ sshlog.Manager, _ *logrus.Logger, _, _ string, _ chan struct{}, _, _ time.Duration, _ bool) (*SSHServer, error) {
|
||||
func New(_ sshlog.Manager, _ *logrus.Logger, _, _ string, _ chan struct{}, _, _ time.Duration) (*SSHServer, error) {
|
||||
return nil, errors.New("cloudflared ssh server is not supported on windows")
|
||||
}
|
||||
|
||||
|
|
|
|||
Loading…
Reference in New Issue