func runSSHCommandViaBastion()

in clusterloader2/pkg/util/ssh_core.go [292:354]
51 lines of code
10 McCabe index (conditional complexity)

func runSSHCommandViaBastion(ctx context.Context, cmd, user, bastion, host string, signer ssh.Signer) (string, string, int, error) {
	// Setup the config, dial the server, and open a session.
	config := &ssh.ClientConfig{
		User:            user,
		Auth:            []ssh.AuthMethod{ssh.PublicKeys(signer)},
		HostKeyCallback: ssh.InsecureIgnoreHostKey(),
		Timeout:         150 * time.Second,
	}
	bastionClient, err := ssh.Dial("tcp", bastion, config)
	if err != nil {
		err = wait.PollUntilContextTimeout(ctx, 5*time.Second, 20*time.Second, false, func(_ context.Context) (bool, error) {
			fmt.Printf("error dialing %s@%s: '%v', retrying\n", user, bastion, err)
			if bastionClient, err = ssh.Dial("tcp", bastion, config); err != nil {
				return false, err
			}
			return true, nil
		})
	}
	if err != nil {
		return "", "", 0, fmt.Errorf("error getting SSH client to %s@%s: %w", user, bastion, err)
	}
	defer bastionClient.Close()

	conn, err := bastionClient.Dial("tcp", host)
	if err != nil {
		return "", "", 0, fmt.Errorf("error dialing %s from bastion: %w", host, err)
	}
	defer conn.Close()

	ncc, chans, reqs, err := ssh.NewClientConn(conn, host, config)
	if err != nil {
		return "", "", 0, fmt.Errorf("error creating forwarding connection %s from bastion: %w", host, err)
	}
	client := ssh.NewClient(ncc, chans, reqs)
	defer client.Close()

	session, err := client.NewSession()
	if err != nil {
		return "", "", 0, fmt.Errorf("error creating session to %s@%s from bastion: %w", user, host, err)
	}
	defer session.Close()

	// Run the command.
	code := 0
	var bout, berr bytes.Buffer
	session.Stdout, session.Stderr = &bout, &berr
	if err = session.Run(cmd); err != nil {
		// Check whether the command failed to run or didn't complete.
		if exiterr, ok := err.(*ssh.ExitError); ok {
			// If we got an ExitError and the exit code is nonzero, we'll
			// consider the SSH itself successful (just that the command run
			// errored on the host).
			if code = exiterr.ExitStatus(); code != 0 {
				err = nil
			}
		} else {
			// Some other kind of error happened (e.g. an IOError); consider the
			// SSH unsuccessful.
			err = fmt.Errorf("failed running `%s` on %s@%s: %w", cmd, user, host, err)
		}
	}
	return bout.String(), berr.String(), code, err
}