implement rfd 18

lib/client/api.go

@@ -271,9 +271,12 @@ type Config struct {
 	// (not currently implemented), or set to 'none' to suppress browser opening entirely.
 	Browser string
 
-	// UseLocalSSHAgent will write user certificates to the local ssh-agent (or
-	// similar) socket at $SSH_AUTH_SOCK.
-	UseLocalSSHAgent bool
+	// AddKeysToAgent specifies how the client handles keys.
+	//	auto - will attempt to add keys to agent if the agent supports it
+	//	only - attempt to load keys into agent but don't write them to disk
+	//	on - attempt to load keys into agent
+	//	off - do not attempt to load keys into agent
+	AddKeysToAgent string
 
 	// EnableEscapeSequences will scan Stdin for SSH escape sequences during
 	// command/shell execution. This also requires Stdin to be an interactive
@@ -298,7 +301,7 @@ func MakeDefaultConfig() *Config {
 		Stdout:                os.Stdout,
 		Stderr:                os.Stderr,
 		Stdin:                 os.Stdin,
-		UseLocalSSHAgent:      true,
+		AddKeysToAgent:        "auto",
 		EnableEscapeSequences: true,
 	}
 }
@@ -945,7 +948,7 @@ func NewClient(c *Config) (tc *TeleportClient, err error) {
 	} else {
 		// initialize the local agent (auth agent which uses local SSH keys signed by the CA):
 		webProxyHost, _ := tc.WebProxyHostPort()
-		tc.localAgent, err = NewLocalAgent(c.KeysDir, webProxyHost, c.Username, c.UseLocalSSHAgent)
+		tc.localAgent, err = NewLocalAgent(c.KeysDir, webProxyHost, c.Username, c.AddKeysToAgent)
 		if err != nil {
 			return nil, trace.Wrap(err)
 		}

lib/client/keyagent.go

@@ -64,6 +64,9 @@ type LocalKeyAgent struct {
 
 	// proxyHost is the proxy for the cluster that his key agent holds keys for.
 	proxyHost string
+
+	// saveKeys dictates whether the agent will save added keys to disk or not.
+	saveKeys bool
 }
 
 // NewKeyStoreCertChecker returns a new certificate checker
@@ -100,9 +103,14 @@ func NewKeyStoreCertChecker(keyStore LocalKeyStore) ssh.HostKeyCallback {
 	}
 }
 
+func agentSupportsSSHCertificates() bool {
+	agent := os.Getenv(teleport.SSHAuthSock)
+	return !strings.Contains(agent, "gpg-agent")
+}
+
 // NewLocalAgent reads all Teleport certificates from disk (using FSLocalKeyStore),
 // creates a LocalKeyAgent, loads all certificates into it, and returns the agent.
-func NewLocalAgent(keyDir, proxyHost, username string, useLocalSSHAgent bool) (a *LocalKeyAgent, err error) {
+func NewLocalAgent(keyDir, proxyHost, username string, addKeysToAgent string) (a *LocalKeyAgent, err error) {
 	keystore, err := NewFSLocalKeyStore(keyDir)
 	if err != nil {
 		return nil, trace.Wrap(err)
@@ -117,9 +125,10 @@ func NewLocalAgent(keyDir, proxyHost, username string, useLocalSSHAgent bool) (a
 		noHosts:   make(map[string]bool),
 		username:  username,
 		proxyHost: proxyHost,
+		saveKeys:  addKeysToAgent != "only",
 	}
 
-	if useLocalSSHAgent {
+	if (addKeysToAgent == "auto" || agentSupportsSSHCertificates()) || addKeysToAgent == "only" || addKeysToAgent == "yes" {
 		a.sshAgent = connectToSSHAgent()
 	} else {
 		log.Debug("Skipping connection to the local ssh-agent.")
@@ -403,10 +412,12 @@ func (a *LocalKeyAgent) defaultHostPromptFunc(host string, key ssh.PublicKey, wr
 // AddKey activates a new signed session key by adding it into the keystore and also
 // by loading it into the SSH agent
 func (a *LocalKeyAgent) AddKey(key *Key) (*agent.AddedKey, error) {
-	// save it to disk (usually into ~/.tsh)
-	err := a.keyStore.AddKey(a.proxyHost, a.username, key)
-	if err != nil {
-		return nil, trace.Wrap(err)
+	if a.saveKeys {
+		// save it to disk (usually into ~/.tsh)
+		err := a.keyStore.AddKey(a.proxyHost, a.username, key)
+		if err != nil {
+			return nil, trace.Wrap(err)
+		}
 	}
 
 	// load key into the teleport agent and system agent

lib/client/keyagent_test.go

@@ -96,7 +96,7 @@ func (s *KeyAgentTestSuite) SetUpTest(c *check.C) {
 //     a teleport key with the teleport username.
 func (s *KeyAgentTestSuite) TestAddKey(c *check.C) {
 	// make a new local agent
-	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, true)
+	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, "auto")
 	c.Assert(err, check.IsNil)
 
 	// add the key to the local agent, this should write the key
@@ -155,7 +155,7 @@ func (s *KeyAgentTestSuite) TestLoadKey(c *check.C) {
 	userdata := []byte("hello, world")
 
 	// make a new local agent
-	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, true)
+	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, "auto")
 	c.Assert(err, check.IsNil)
 
 	// unload any keys that might be in the agent for this user
@@ -213,7 +213,7 @@ func (s *KeyAgentTestSuite) TestLoadKey(c *check.C) {
 
 func (s *KeyAgentTestSuite) TestHostCertVerification(c *check.C) {
 	// Make a new local agent.
-	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, true)
+	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, "auto")
 	c.Assert(err, check.IsNil)
 
 	// By default user has not refused any hosts.
@@ -294,7 +294,7 @@ func (s *KeyAgentTestSuite) TestHostCertVerification(c *check.C) {
 
 func (s *KeyAgentTestSuite) TestHostKeyVerification(c *check.C) {
 	// make a new local agent
-	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, true)
+	lka, err := NewLocalAgent(s.keyDir, s.hostname, s.username, "auto")
 	c.Assert(err, check.IsNil)
 
 	// by default user has not refused any hosts:
@@ -348,7 +348,7 @@ func (s *KeyAgentTestSuite) TestHostKeyVerification(c *check.C) {
 func (s *KeyAgentTestSuite) TestDefaultHostPromptFunc(c *check.C) {
 	keygen := testauthority.New()
 
-	a, err := NewLocalAgent(s.keyDir, s.hostname, s.username, true)
+	a, err := NewLocalAgent(s.keyDir, s.hostname, s.username, "auto")
 	c.Assert(err, check.IsNil)
 
 	_, keyBytes, err := keygen.GenerateKeyPair("")

tool/tsh/tsh.go

@@ -196,6 +196,9 @@ type CLIConf struct {
 	// connect to the local ssh-agent (or similar) socket at $SSH_AUTH_SOCK.
 	UseLocalSSHAgent bool
 
+	// AddKeysToAgent specifies the behaviour of how certs are handled.
+	AddKeysToAgent string
+
 	// EnableEscapeSequences will scan stdin for SSH escape sequences during
 	// command/shell execution. This also requires stdin to be an interactive
 	// terminal.
@@ -243,6 +246,7 @@ const (
 	// cluster. All new code should use TELEPORT_CLUSTER instead.
 	siteEnvVar             = "TELEPORT_SITE"
 	userEnvVar             = "TELEPORT_USER"
+	addKeysToAgentEnvVar   = "TELEPORT_ADD_KEYS_TO_AGENT"
 	useLocalSSHAgentEnvVar = "TELEPORT_USE_LOCAL_SSH_AGENT"
 
 	clusterHelp = "Specify the cluster to connect"
@@ -279,7 +283,9 @@ func Run(args []string, opts ...cliOption) error {
 	app.Flag("gops-addr", "Specify gops addr to listen on").Hidden().StringVar(&cf.GopsAddr)
 	app.Flag("skip-version-check", "Skip version checking between server and client.").BoolVar(&cf.SkipVersionCheck)
 	app.Flag("debug", "Verbose logging to stdout").Short('d').BoolVar(&cf.Debug)
+	app.Flag("add-keys-to-agent", "Controls how keys are handled. Valid values are yes, no, auto or only").Short('k').Envar(addKeysToAgentEnvVar).Default("auto").StringVar(&cf.AddKeysToAgent)
 	app.Flag("use-local-ssh-agent", fmt.Sprintf("Load generated SSH certificates into the local ssh-agent (specified via $SSH_AUTH_SOCK). You can also set %v environment variable. Default is true.", useLocalSSHAgentEnvVar)).
+		Hidden().
 		Envar(useLocalSSHAgentEnvVar).
 		Default("true").
 		BoolVar(&cf.UseLocalSSHAgent)
@@ -460,6 +466,20 @@ func Run(args []string, opts ...cliOption) error {
 		return trace.Wrap(err)
 	}
 
+	// parameter must be yes, no, auto or only
+	switch cf.AddKeysToAgent {
+	case "yes":
+		break
+	case "no":
+		break
+	case "auto":
+		break
+	case "only":
+		break
+	default:
+		return trace.BadParameter("valid values for parameter add-keys-to-agent are yes, no, auto or only, got %s", cf.AddKeysToAgent)
+	}
+
 	// Read in cluster flag from CLI or environment.
 	readClusterFlag(&cf, os.Getenv)
 
@@ -1634,11 +1654,10 @@ func makeClient(cf *CLIConf, useProfileLogin bool) (*client.TeleportClient, erro
 	// (not currently implemented) or set to 'none' to suppress browser opening entirely.
 	c.Browser = cf.Browser
 
-	// Do not write SSH certs into the local ssh-agent if user requested it.
-	//
-	// This is specifically for gpg-agent, which doesn't support SSH
-	// certificates (https://dev.gnupg.org/T1756)
-	c.UseLocalSSHAgent = cf.UseLocalSSHAgent
+	c.AddKeysToAgent = cf.AddKeysToAgent
+	if cf.UseLocalSSHAgent == false {
+		c.AddKeysToAgent = "off"
+	}
 
 	c.EnableEscapeSequences = cf.EnableEscapeSequences