ssh/tailssh: add ssh session recording failed event type

This change introduces a SSHSessionRecordingFailed event type
that is used when a session recording fails to start or fails during a
session, and the on failure indicates that it should fail open.

Updates tailscale/corp#9967

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>

ssh/tailssh/tailssh.go

@@ -1607,7 +1607,11 @@ func (ss *sshSession) startNewRecording() (_ *recording, err error) {
 		rec.out, attempts, errChan, err = ss.connectToRecorder(ctx, recorders)
 		if err != nil {
 			if onFailure != nil && onFailure.NotifyURL != "" && len(attempts) > 0 {
-				ss.notifyControl(ctx, nodeKey, tailcfg.SSHSessionRecordingRejected, attempts, onFailure.NotifyURL)
+				eventType := tailcfg.SSHSessionRecordingFailed
+				if onFailure.RejectSessionWithMessage != "" {
+					eventType = tailcfg.SSHSessionRecordingRejected
+				}
+				ss.notifyControl(ctx, nodeKey, eventType, attempts, onFailure.NotifyURL)
 			}
 
 			if onFailure != nil && onFailure.RejectSessionWithMessage != "" {
@@ -1630,7 +1634,12 @@ func (ss *sshSession) startNewRecording() (_ *recording, err error) {
 				lastAttempt := attempts[len(attempts)-1]
 				lastAttempt.FailureMessage = err.Error()
 
-				ss.notifyControl(ctx, nodeKey, tailcfg.SSHSessionRecordingTerminated, attempts, onFailure.NotifyURL)
+				eventType := tailcfg.SSHSessionRecordingFailed
+				if onFailure.TerminateSessionWithMessage != "" {
+					eventType = tailcfg.SSHSessionRecordingTerminated
+				}
+
+				ss.notifyControl(ctx, nodeKey, eventType, attempts, onFailure.NotifyURL)
 			}
 			if onFailure != nil && onFailure.TerminateSessionWithMessage != "" {
 				ss.logf("recording: error uploading recording (closing session): %v", err)

tailcfg/tailcfg.go

@@ -2111,8 +2111,22 @@ type SSHEventType int
 
 const (
 	UnspecifiedSSHEventType SSHEventType = 0
+	// SSHSessionRecordingRejected is the event that
+	// defines when a SSH session cannot be started
+	// because no recorder is available for session
+	// recording, and the SSHRecorderFailureAction
+	// RejectSessionWithMessage is not empty.
 	SSHSessionRecordingRejected SSHEventType = 1
+	// SSHSessionRecordingTerminated is the event that
+	// defines when session recording has failed
+	// during the session and the SSHRecorderFailureAction
+	// TerminateSessionWithMessage is not empty.
 	SSHSessionRecordingTerminated SSHEventType = 2
+	// SSHSessionRecordingFailed is the event that
+	// defines when session recording is unavailable and
+	// the SSHRecorderFailureAction RejectSessionWithMessage
+	// or TerminateSessionWithMessage is empty.
+	SSHSessionRecordingFailed SSHEventType = 3
 )
 
 // SSHRecordingAttempt is a single attempt to start a recording.