dockerimg/sshtheater.go - sketch - Gitiles

 package dockerimg

 import (
 	"bufio"
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/x509"
 	"encoding/pem"
 	"fmt"
 	"os"
 	"path/filepath"
 	"strings"

 	"github.com/kevinburke/ssh_config"
 	"golang.org/x/crypto/ssh"
 	"golang.org/x/crypto/ssh/knownhosts"
 )

 const keyBitSize = 2048

 // SSHTheater does the necessary key pair generation, known_hosts updates, ssh_config file updates etc steps
 // so that ssh can connect to a locally running sketch container to other local processes like vscode without
 // the user having to run the usual ssh obstacle course.
 //
 // SSHTheater does not modify your default .ssh/config, or known_hosts files.  However, in order for you
 // to be able to use it properly you will have to make a one-time edit to your ~/.ssh/config file.
 //
 // In your ~/.ssh/config file, add the following line:
 //
 // Include $HOME/.sketch/ssh_config
 //
 // where $HOME is your home directory.
 type SSHTheater struct {
 	cntrName string
 	sshHost  string
 	sshPort  string

 	knownHostsPath     string
 	userIdentityPath   string
 	sshConfigPath      string
 	serverIdentityPath string

 	serverPublicKey ssh.PublicKey
 	serverIdentity  []byte
 	userIdentity    []byte
 }

 // NewSSHTheather will set up everything so that you can use ssh on localhost to connect to
 // the sketch container.  Call #Clean when you are done with the container to remove the
 // various entries it created in its known_hosts and ssh_config files. Also note that
 // this will generate key pairs for both the ssh server identity and the user identity, if
 // these files do not already exist.  These key pair files are not deleted by #Cleanup,
 // so they can be re-used across invocations of sketch. This means every sketch container
 // that runs on this host will use the same ssh server identity.
 //
 // If this doesn't return an error, you should be able to run "ssh <cntrName>"
 // in a terminal on your host machine to open a shell into the container without having
 // to manually accept changes to your known_hosts file etc.
 func NewSSHTheather(cntrName, sshHost, sshPort string) (*SSHTheater, error) {
 	base := filepath.Join(os.Getenv("HOME"), ".sketch")
 	if _, err := os.Stat(base); err != nil {
 		if err := os.Mkdir(base, 0o777); err != nil {
 			return nil, fmt.Errorf("couldn't create %s: %w", base, err)
 		}
 	}

 	cst := &SSHTheater{
 		cntrName:           cntrName,
 		sshHost:            sshHost,
 		sshPort:            sshPort,
 		knownHostsPath:     filepath.Join(base, "known_hosts"),
 		userIdentityPath:   filepath.Join(base, "container_user_identity"),
 		serverIdentityPath: filepath.Join(base, "container_server_identity"),
 		sshConfigPath:      filepath.Join(base, "ssh_config"),
 	}
 	if _, err := createKeyPairIfMissing(cst.serverIdentityPath); err != nil {
 		return nil, fmt.Errorf("couldn't create server identity: %w", err)
 	}
 	if _, err := createKeyPairIfMissing(cst.userIdentityPath); err != nil {
 		return nil, fmt.Errorf("couldn't create user identity: %w", err)
 	}

 	serverIdentity, err := os.ReadFile(cst.serverIdentityPath)
 	if err != nil {
 		return nil, fmt.Errorf("couldn't read container's ssh server identity: %w", err)
 	}
 	cst.serverIdentity = serverIdentity

 	serverPubKeyBytes, err := os.ReadFile(cst.serverIdentityPath + ".pub")
 	serverPubKey, _, _, _, err := ssh.ParseAuthorizedKey(serverPubKeyBytes)
 	if err != nil {
 		return nil, fmt.Errorf("couldn't read ssh server public key: %w", err)
 	}
 	cst.serverPublicKey = serverPubKey

 	userIdentity, err := os.ReadFile(cst.userIdentityPath + ".pub")
 	if err != nil {
 		return nil, fmt.Errorf("couldn't read ssh user identity: %w", err)
 	}
 	cst.userIdentity = userIdentity

 	if err := cst.addContainerToSSHConfig(); err != nil {
 		return nil, fmt.Errorf("couldn't add container to ssh_config: %w", err)
 	}

 	if err := cst.addContainerToKnownHosts(); err != nil {
 		return nil, fmt.Errorf("couldn't update known hosts: %w", err)
 	}

 	return cst, nil
 }

 func CheckForInclude() error {
 	sketchSSHPathInclude := "Include " + filepath.Join(os.Getenv("HOME"), ".sketch", "ssh_config")
 	defaultSSHPath := filepath.Join(os.Getenv("HOME"), ".ssh", "config")
 	f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
 	cfg, _ := ssh_config.Decode(f)
 	var sketchInludePos *ssh_config.Position
 	var firstNonIncludePos *ssh_config.Position
 	for _, host := range cfg.Hosts {
 		for _, node := range host.Nodes {
 			inc, ok := node.(*ssh_config.Include)
 			if ok {
 				if strings.TrimSpace(inc.String()) == sketchSSHPathInclude {
 					pos := inc.Pos()
 					sketchInludePos = &pos
 				}
 			} else if firstNonIncludePos == nil && !strings.HasPrefix(strings.TrimSpace(node.String()), "#") {
 				pos := node.Pos()
 				firstNonIncludePos = &pos
 			}
 		}
 	}

 	if sketchInludePos == nil {
 		return fmt.Errorf("⚠️  SSH connections are disabled. To enable them, add the line %q to the top of %s before any 'Host' lines", sketchSSHPathInclude, defaultSSHPath)
 	}

 	if firstNonIncludePos != nil && firstNonIncludePos.Line < sketchInludePos.Line {
 		fmt.Printf("⚠️  SSH confg warning: The location of the Include statement for sketch's ssh config on line %d of %s may prevent ssh from working with sketch containers. Try moving it to the top of the file (before any 'Host' lines) if ssh isn't working for you.\n", sketchInludePos.Line, defaultSSHPath)
 	}
 	return nil
 }

 func removeFromHosts(cntrName string, cfgHosts []*ssh_config.Host) []*ssh_config.Host {
 	hosts := []*ssh_config.Host{}
 	for _, host := range cfgHosts {
 		if host.Matches(cntrName) || strings.Contains(host.String(), cntrName) {
 			continue
 		}
 		patMatch := false
 		for _, pat := range host.Patterns {
 			if strings.Contains(pat.String(), cntrName) {
 				patMatch = true
 			}
 		}
 		if patMatch {
 			continue
 		}

 		hosts = append(hosts, host)
 	}
 	return hosts
 }

 func generatePrivateKey(bitSize int) (*rsa.PrivateKey, error) {
 	privateKey, err := rsa.GenerateKey(rand.Reader, bitSize)
 	if err != nil {
 		return nil, err
 	}
 	return privateKey, nil
 }

 // generatePublicKey take a rsa.PublicKey and return bytes suitable for writing to .pub file
 // returns in the format "ssh-rsa ..."
 func generatePublicKey(privatekey *rsa.PublicKey) (ssh.PublicKey, error) {
 	publicRsaKey, err := ssh.NewPublicKey(privatekey)
 	if err != nil {
 		return nil, err
 	}

 	return publicRsaKey, nil
 }

 func encodePrivateKeyToPEM(privateKey *rsa.PrivateKey) []byte {
 	pemBlock := &pem.Block{
 		Type:  "RSA PRIVATE KEY",
 		Bytes: x509.MarshalPKCS1PrivateKey(privateKey),
 	}
 	pemBytes := pem.EncodeToMemory(pemBlock)
 	return pemBytes
 }

 func writeKeyToFile(keyBytes []byte, filename string) error {
 	err := os.WriteFile(filename, keyBytes, 0o600)
 	return err
 }

 func createKeyPairIfMissing(idPath string) (ssh.PublicKey, error) {
 	if _, err := os.Stat(idPath); err == nil {
 		return nil, nil
 	}

 	privateKey, err := generatePrivateKey(keyBitSize)
 	if err != nil {
 		return nil, fmt.Errorf("Error generating private key: %w", err)
 	}

 	publicRsaKey, err := generatePublicKey(&privateKey.PublicKey)
 	if err != nil {
 		return nil, fmt.Errorf("Error generating public key: %w", err)
 	}

 	privateKeyPEM := encodePrivateKeyToPEM(privateKey)

 	err = writeKeyToFile(privateKeyPEM, idPath)
 	if err != nil {
 		return nil, fmt.Errorf("Error writing private key to file %w", err)
 	}
 	pubKeyBytes := ssh.MarshalAuthorizedKey(publicRsaKey)

 	err = writeKeyToFile([]byte(pubKeyBytes), idPath+".pub")
 	if err != nil {
 		return nil, fmt.Errorf("Error writing public key to file %w", err)
 	}
 	return publicRsaKey, nil
 }

 func (c *SSHTheater) addSketchHostMatchIfMissing(cfg *ssh_config.Config) error {
 	found := false
 	for _, host := range cfg.Hosts {
 		if strings.Contains(host.String(), "host=\"sketch-*\"") {
 			found = true
 			break
 		}
 	}
 	if !found {
 		hostPattern, err := ssh_config.NewPattern("host=\"sketch-*\"")
 		if err != nil {
 			return fmt.Errorf("couldn't add pattern to ssh_config: %w", err)
 		}

 		hostCfg := &ssh_config.Host{Patterns: []*ssh_config.Pattern{hostPattern}}
 		hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "UserKnownHostsFile", Value: c.knownHostsPath})

 		hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "IdentityFile", Value: c.userIdentityPath})
 		hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.Empty{})

 		cfg.Hosts = append([]*ssh_config.Host{hostCfg}, cfg.Hosts...)
 	}
 	return nil
 }

 func (c *SSHTheater) addContainerToSSHConfig() error {
 	f, err := os.OpenFile(c.sshConfigPath, os.O_RDWR|os.O_CREATE, 0o644)
 	if err != nil {
 		return fmt.Errorf("couldn't open ssh_config: %w", err)
 	}
 	defer f.Close()

 	cfg, err := ssh_config.Decode(f)
 	if err != nil {
 		return fmt.Errorf("couldn't decode ssh_config: %w", err)
 	}
 	cntrPattern, err := ssh_config.NewPattern(c.cntrName)
 	if err != nil {
 		return fmt.Errorf("couldn't add pattern to ssh_config: %w", err)
 	}

 	// Remove any matches for this container if they already exist.
 	cfg.Hosts = removeFromHosts(c.cntrName, cfg.Hosts)

 	hostCfg := &ssh_config.Host{Patterns: []*ssh_config.Pattern{cntrPattern}}
 	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "HostName", Value: c.sshHost})
 	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "User", Value: "root"})
 	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "Port", Value: c.sshPort})
 	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "IdentityFile", Value: c.userIdentityPath})
 	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "UserKnownHostsFile", Value: c.knownHostsPath})

 	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.Empty{})
 	cfg.Hosts = append(cfg.Hosts, hostCfg)

 	if err := c.addSketchHostMatchIfMissing(cfg); err != nil {
 		return fmt.Errorf("couldn't add missing host match: %w", err)
 	}

 	cfgBytes, err := cfg.MarshalText()
 	if err != nil {
 		return fmt.Errorf("couldn't marshal ssh_config: %w", err)
 	}
 	if err := f.Truncate(0); err != nil {
 		return fmt.Errorf("couldn't truncate ssh_config: %w", err)
 	}
 	if _, err := f.Seek(0, 0); err != nil {
 		return fmt.Errorf("couldn't seek to beginning of ssh_config: %w", err)
 	}
 	if _, err := f.Write(cfgBytes); err != nil {
 		return fmt.Errorf("couldn't write ssh_config: %w", err)
 	}

 	return nil
 }

 func (c *SSHTheater) addContainerToKnownHosts() error {
 	f, err := os.OpenFile(c.knownHostsPath, os.O_RDWR|os.O_CREATE, 0o644)
 	if err != nil {
 		return fmt.Errorf("couldn't open %s: %w", c.knownHostsPath, err)
 	}
 	defer f.Close()
 	pkBytes := c.serverPublicKey.Marshal()
 	if len(pkBytes) == 0 {
 		return fmt.Errorf("empty serverPublicKey. This is a bug")
 	}
 	newHostLine := knownhosts.Line([]string{c.sshHost + ":" + c.sshPort}, c.serverPublicKey)

 	outputLines := []string{}
 	scanner := bufio.NewScanner(f)
 	for scanner.Scan() {
 		outputLines = append(outputLines, scanner.Text())
 	}
 	outputLines = append(outputLines, newHostLine)
 	if err := f.Truncate(0); err != nil {
 		return fmt.Errorf("couldn't truncate known_hosts: %w", err)
 	}
 	if _, err := f.Seek(0, 0); err != nil {
 		return fmt.Errorf("couldn't seek to beginning of known_hosts: %w", err)
 	}
 	if _, err := f.Write([]byte(strings.Join(outputLines, "\n"))); err != nil {
 		return fmt.Errorf("couldn't write updated known_hosts to to %s: %w", c.knownHostsPath, err)
 	}

 	return nil
 }

 func (c *SSHTheater) removeContainerFromKnownHosts() error {
 	f, err := os.OpenFile(c.knownHostsPath, os.O_RDWR|os.O_CREATE, 0o644)
 	if err != nil {
 		return fmt.Errorf("couldn't open ssh_config: %w", err)
 	}
 	defer f.Close()
 	scanner := bufio.NewScanner(f)
 	lineToRemove := knownhosts.Line([]string{c.sshHost + ":" + c.sshPort}, c.serverPublicKey)
 	outputLines := []string{}
 	for scanner.Scan() {
 		if scanner.Text() == lineToRemove {
 			continue
 		}
 		outputLines = append(outputLines, scanner.Text())
 	}
 	if err := f.Truncate(0); err != nil {
 		return fmt.Errorf("couldn't truncate known_hosts: %w", err)
 	}
 	if _, err := f.Seek(0, 0); err != nil {
 		return fmt.Errorf("couldn't seek to beginning of known_hosts: %w", err)
 	}
 	if _, err := f.Write([]byte(strings.Join(outputLines, "\n"))); err != nil {
 		return fmt.Errorf("couldn't write updated known_hosts to to %s: %w", c.knownHostsPath, err)
 	}

 	return nil
 }

 func (c *SSHTheater) Cleanup() error {
 	if err := c.removeContainerFromSSHConfig(); err != nil {
 		return fmt.Errorf("couldn't remove container from ssh_config: %v\n", err)
 	}
 	if err := c.removeContainerFromKnownHosts(); err != nil {
 		return fmt.Errorf("couldn't remove container from ssh_config: %v\n", err)
 	}

 	return nil
 }

 func (c *SSHTheater) removeContainerFromSSHConfig() error {
 	f, err := os.OpenFile(c.sshConfigPath, os.O_RDWR|os.O_CREATE, 0o644)
 	if err != nil {
 		return fmt.Errorf("couldn't open ssh_config: %w", err)
 	}
 	defer f.Close()

 	cfg, err := ssh_config.Decode(f)
 	if err != nil {
 		return fmt.Errorf("couldn't decode ssh_config: %w", err)
 	}
 	cfg.Hosts = removeFromHosts(c.cntrName, cfg.Hosts)

 	if err := c.addSketchHostMatchIfMissing(cfg); err != nil {
 		return fmt.Errorf("couldn't add missing host match: %w", err)
 	}

 	cfgBytes, err := cfg.MarshalText()
 	if err != nil {
 		return fmt.Errorf("couldn't marshal ssh_config: %w", err)
 	}
 	if err := f.Truncate(0); err != nil {
 		return fmt.Errorf("couldn't truncate ssh_config: %w", err)
 	}
 	if _, err := f.Seek(0, 0); err != nil {
 		return fmt.Errorf("couldn't seek to beginning of ssh_config: %w", err)
 	}
 	if _, err := f.Write(cfgBytes); err != nil {
 		return fmt.Errorf("couldn't write ssh_config: %w", err)
 	}
 	return nil
 }
	package dockerimg

	import (
	"bufio"
	"crypto/rand"
	"crypto/rsa"
	"crypto/x509"
	"encoding/pem"
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/kevinburke/ssh_config"
	"golang.org/x/crypto/ssh"
	"golang.org/x/crypto/ssh/knownhosts"
	)

	const keyBitSize = 2048

	// SSHTheater does the necessary key pair generation, known_hosts updates, ssh_config file updates etc steps
	// so that ssh can connect to a locally running sketch container to other local processes like vscode without
	// the user having to run the usual ssh obstacle course.
	//
	// SSHTheater does not modify your default .ssh/config, or known_hosts files. However, in order for you
	// to be able to use it properly you will have to make a one-time edit to your ~/.ssh/config file.
	//
	// In your ~/.ssh/config file, add the following line:
	//
	// Include $HOME/.sketch/ssh_config
	//
	// where $HOME is your home directory.
	type SSHTheater struct {
	cntrName string
	sshHost string
	sshPort string

	knownHostsPath string
	userIdentityPath string
	sshConfigPath string
	serverIdentityPath string

	serverPublicKey ssh.PublicKey
	serverIdentity []byte
	userIdentity []byte
	}

	// NewSSHTheather will set up everything so that you can use ssh on localhost to connect to
	// the sketch container. Call #Clean when you are done with the container to remove the
	// various entries it created in its known_hosts and ssh_config files. Also note that
	// this will generate key pairs for both the ssh server identity and the user identity, if
	// these files do not already exist. These key pair files are not deleted by #Cleanup,
	// so they can be re-used across invocations of sketch. This means every sketch container
	// that runs on this host will use the same ssh server identity.
	//
	// If this doesn't return an error, you should be able to run "ssh <cntrName>"
	// in a terminal on your host machine to open a shell into the container without having
	// to manually accept changes to your known_hosts file etc.
	func NewSSHTheather(cntrName, sshHost, sshPort string) (*SSHTheater, error) {
	base := filepath.Join(os.Getenv("HOME"), ".sketch")
	if _, err := os.Stat(base); err != nil {
	if err := os.Mkdir(base, 0o777); err != nil {
	return nil, fmt.Errorf("couldn't create %s: %w", base, err)
	}
	}

	cst := &SSHTheater{
	cntrName: cntrName,
	sshHost: sshHost,
	sshPort: sshPort,
	knownHostsPath: filepath.Join(base, "known_hosts"),
	userIdentityPath: filepath.Join(base, "container_user_identity"),
	serverIdentityPath: filepath.Join(base, "container_server_identity"),
	sshConfigPath: filepath.Join(base, "ssh_config"),
	}
	if _, err := createKeyPairIfMissing(cst.serverIdentityPath); err != nil {
	return nil, fmt.Errorf("couldn't create server identity: %w", err)
	}
	if _, err := createKeyPairIfMissing(cst.userIdentityPath); err != nil {
	return nil, fmt.Errorf("couldn't create user identity: %w", err)
	}

	serverIdentity, err := os.ReadFile(cst.serverIdentityPath)
	if err != nil {
	return nil, fmt.Errorf("couldn't read container's ssh server identity: %w", err)
	}
	cst.serverIdentity = serverIdentity

	serverPubKeyBytes, err := os.ReadFile(cst.serverIdentityPath + ".pub")
	serverPubKey, _, _, _, err := ssh.ParseAuthorizedKey(serverPubKeyBytes)
	if err != nil {
	return nil, fmt.Errorf("couldn't read ssh server public key: %w", err)
	}
	cst.serverPublicKey = serverPubKey

	userIdentity, err := os.ReadFile(cst.userIdentityPath + ".pub")
	if err != nil {
	return nil, fmt.Errorf("couldn't read ssh user identity: %w", err)
	}
	cst.userIdentity = userIdentity

	if err := cst.addContainerToSSHConfig(); err != nil {
	return nil, fmt.Errorf("couldn't add container to ssh_config: %w", err)
	}

	if err := cst.addContainerToKnownHosts(); err != nil {
	return nil, fmt.Errorf("couldn't update known hosts: %w", err)
	}

	return cst, nil
	}

	func CheckForInclude() error {
	sketchSSHPathInclude := "Include " + filepath.Join(os.Getenv("HOME"), ".sketch", "ssh_config")
	defaultSSHPath := filepath.Join(os.Getenv("HOME"), ".ssh", "config")
	f, _ := os.Open(filepath.Join(os.Getenv("HOME"), ".ssh", "config"))
	cfg, _ := ssh_config.Decode(f)
	var sketchInludePos *ssh_config.Position
	var firstNonIncludePos *ssh_config.Position
	for _, host := range cfg.Hosts {
	for _, node := range host.Nodes {
	inc, ok := node.(*ssh_config.Include)
	if ok {
	if strings.TrimSpace(inc.String()) == sketchSSHPathInclude {
	pos := inc.Pos()
	sketchInludePos = &pos
	}
	} else if firstNonIncludePos == nil && !strings.HasPrefix(strings.TrimSpace(node.String()), "#") {
	pos := node.Pos()
	firstNonIncludePos = &pos
	}
	}
	}

	if sketchInludePos == nil {
	return fmt.Errorf("⚠️ SSH connections are disabled. To enable them, add the line %q to the top of %s before any 'Host' lines", sketchSSHPathInclude, defaultSSHPath)
	}

	if firstNonIncludePos != nil && firstNonIncludePos.Line < sketchInludePos.Line {
	fmt.Printf("⚠️ SSH confg warning: The location of the Include statement for sketch's ssh config on line %d of %s may prevent ssh from working with sketch containers. Try moving it to the top of the file (before any 'Host' lines) if ssh isn't working for you.\n", sketchInludePos.Line, defaultSSHPath)
	}
	return nil
	}

	func removeFromHosts(cntrName string, cfgHosts []ssh_config.Host) []ssh_config.Host {
	hosts := []*ssh_config.Host{}
	for _, host := range cfgHosts {
	if host.Matches(cntrName) \|\| strings.Contains(host.String(), cntrName) {
	continue
	}
	patMatch := false
	for _, pat := range host.Patterns {
	if strings.Contains(pat.String(), cntrName) {
	patMatch = true
	}
	}
	if patMatch {
	continue
	}

	hosts = append(hosts, host)
	}
	return hosts
	}

	func generatePrivateKey(bitSize int) (*rsa.PrivateKey, error) {
	privateKey, err := rsa.GenerateKey(rand.Reader, bitSize)
	if err != nil {
	return nil, err
	}
	return privateKey, nil
	}

	// generatePublicKey take a rsa.PublicKey and return bytes suitable for writing to .pub file
	// returns in the format "ssh-rsa ..."
	func generatePublicKey(privatekey *rsa.PublicKey) (ssh.PublicKey, error) {
	publicRsaKey, err := ssh.NewPublicKey(privatekey)
	if err != nil {
	return nil, err
	}

	return publicRsaKey, nil
	}

	func encodePrivateKeyToPEM(privateKey *rsa.PrivateKey) []byte {
	pemBlock := &pem.Block{
	Type: "RSA PRIVATE KEY",
	Bytes: x509.MarshalPKCS1PrivateKey(privateKey),
	}
	pemBytes := pem.EncodeToMemory(pemBlock)
	return pemBytes
	}

	func writeKeyToFile(keyBytes []byte, filename string) error {
	err := os.WriteFile(filename, keyBytes, 0o600)
	return err
	}

	func createKeyPairIfMissing(idPath string) (ssh.PublicKey, error) {
	if _, err := os.Stat(idPath); err == nil {
	return nil, nil
	}

	privateKey, err := generatePrivateKey(keyBitSize)
	if err != nil {
	return nil, fmt.Errorf("Error generating private key: %w", err)
	}

	publicRsaKey, err := generatePublicKey(&privateKey.PublicKey)
	if err != nil {
	return nil, fmt.Errorf("Error generating public key: %w", err)
	}

	privateKeyPEM := encodePrivateKeyToPEM(privateKey)

	err = writeKeyToFile(privateKeyPEM, idPath)
	if err != nil {
	return nil, fmt.Errorf("Error writing private key to file %w", err)
	}
	pubKeyBytes := ssh.MarshalAuthorizedKey(publicRsaKey)

	err = writeKeyToFile([]byte(pubKeyBytes), idPath+".pub")
	if err != nil {
	return nil, fmt.Errorf("Error writing public key to file %w", err)
	}
	return publicRsaKey, nil
	}

	func (c SSHTheater) addSketchHostMatchIfMissing(cfg ssh_config.Config) error {
	found := false
	for _, host := range cfg.Hosts {
	if strings.Contains(host.String(), "host=\"sketch-*\"") {
	found = true
	break
	}
	}
	if !found {
	hostPattern, err := ssh_config.NewPattern("host=\"sketch-*\"")
	if err != nil {
	return fmt.Errorf("couldn't add pattern to ssh_config: %w", err)
	}

	hostCfg := &ssh_config.Host{Patterns: []*ssh_config.Pattern{hostPattern}}
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "UserKnownHostsFile", Value: c.knownHostsPath})

	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "IdentityFile", Value: c.userIdentityPath})
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.Empty{})

	cfg.Hosts = append([]*ssh_config.Host{hostCfg}, cfg.Hosts...)
	}
	return nil
	}

	func (c *SSHTheater) addContainerToSSHConfig() error {
	f, err := os.OpenFile(c.sshConfigPath, os.O_RDWR\|os.O_CREATE, 0o644)
	if err != nil {
	return fmt.Errorf("couldn't open ssh_config: %w", err)
	}
	defer f.Close()

	cfg, err := ssh_config.Decode(f)
	if err != nil {
	return fmt.Errorf("couldn't decode ssh_config: %w", err)
	}
	cntrPattern, err := ssh_config.NewPattern(c.cntrName)
	if err != nil {
	return fmt.Errorf("couldn't add pattern to ssh_config: %w", err)
	}

	// Remove any matches for this container if they already exist.
	cfg.Hosts = removeFromHosts(c.cntrName, cfg.Hosts)

	hostCfg := &ssh_config.Host{Patterns: []*ssh_config.Pattern{cntrPattern}}
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "HostName", Value: c.sshHost})
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "User", Value: "root"})
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "Port", Value: c.sshPort})
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "IdentityFile", Value: c.userIdentityPath})
	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.KV{Key: "UserKnownHostsFile", Value: c.knownHostsPath})

	hostCfg.Nodes = append(hostCfg.Nodes, &ssh_config.Empty{})
	cfg.Hosts = append(cfg.Hosts, hostCfg)

	if err := c.addSketchHostMatchIfMissing(cfg); err != nil {
	return fmt.Errorf("couldn't add missing host match: %w", err)
	}

	cfgBytes, err := cfg.MarshalText()
	if err != nil {
	return fmt.Errorf("couldn't marshal ssh_config: %w", err)
	}
	if err := f.Truncate(0); err != nil {
	return fmt.Errorf("couldn't truncate ssh_config: %w", err)
	}
	if _, err := f.Seek(0, 0); err != nil {
	return fmt.Errorf("couldn't seek to beginning of ssh_config: %w", err)
	}
	if _, err := f.Write(cfgBytes); err != nil {
	return fmt.Errorf("couldn't write ssh_config: %w", err)
	}

	return nil
	}

	func (c *SSHTheater) addContainerToKnownHosts() error {
	f, err := os.OpenFile(c.knownHostsPath, os.O_RDWR\|os.O_CREATE, 0o644)
	if err != nil {
	return fmt.Errorf("couldn't open %s: %w", c.knownHostsPath, err)
	}
	defer f.Close()
	pkBytes := c.serverPublicKey.Marshal()
	if len(pkBytes) == 0 {
	return fmt.Errorf("empty serverPublicKey. This is a bug")
	}
	newHostLine := knownhosts.Line([]string{c.sshHost + ":" + c.sshPort}, c.serverPublicKey)

	outputLines := []string{}
	scanner := bufio.NewScanner(f)
	for scanner.Scan() {
	outputLines = append(outputLines, scanner.Text())
	}
	outputLines = append(outputLines, newHostLine)
	if err := f.Truncate(0); err != nil {
	return fmt.Errorf("couldn't truncate known_hosts: %w", err)
	}
	if _, err := f.Seek(0, 0); err != nil {
	return fmt.Errorf("couldn't seek to beginning of known_hosts: %w", err)
	}
	if _, err := f.Write([]byte(strings.Join(outputLines, "\n"))); err != nil {
	return fmt.Errorf("couldn't write updated known_hosts to to %s: %w", c.knownHostsPath, err)
	}

	return nil
	}

	func (c *SSHTheater) removeContainerFromKnownHosts() error {
	f, err := os.OpenFile(c.knownHostsPath, os.O_RDWR\|os.O_CREATE, 0o644)
	if err != nil {
	return fmt.Errorf("couldn't open ssh_config: %w", err)
	}
	defer f.Close()
	scanner := bufio.NewScanner(f)
	lineToRemove := knownhosts.Line([]string{c.sshHost + ":" + c.sshPort}, c.serverPublicKey)
	outputLines := []string{}
	for scanner.Scan() {
	if scanner.Text() == lineToRemove {
	continue
	}
	outputLines = append(outputLines, scanner.Text())
	}
	if err := f.Truncate(0); err != nil {
	return fmt.Errorf("couldn't truncate known_hosts: %w", err)
	}
	if _, err := f.Seek(0, 0); err != nil {
	return fmt.Errorf("couldn't seek to beginning of known_hosts: %w", err)
	}
	if _, err := f.Write([]byte(strings.Join(outputLines, "\n"))); err != nil {
	return fmt.Errorf("couldn't write updated known_hosts to to %s: %w", c.knownHostsPath, err)
	}

	return nil
	}

	func (c *SSHTheater) Cleanup() error {
	if err := c.removeContainerFromSSHConfig(); err != nil {
	return fmt.Errorf("couldn't remove container from ssh_config: %v\n", err)
	}
	if err := c.removeContainerFromKnownHosts(); err != nil {
	return fmt.Errorf("couldn't remove container from ssh_config: %v\n", err)
	}

	return nil
	}

	func (c *SSHTheater) removeContainerFromSSHConfig() error {
	f, err := os.OpenFile(c.sshConfigPath, os.O_RDWR\|os.O_CREATE, 0o644)
	if err != nil {
	return fmt.Errorf("couldn't open ssh_config: %w", err)
	}
	defer f.Close()

	cfg, err := ssh_config.Decode(f)
	if err != nil {
	return fmt.Errorf("couldn't decode ssh_config: %w", err)
	}
	cfg.Hosts = removeFromHosts(c.cntrName, cfg.Hosts)

	if err := c.addSketchHostMatchIfMissing(cfg); err != nil {
	return fmt.Errorf("couldn't add missing host match: %w", err)
	}

	cfgBytes, err := cfg.MarshalText()
	if err != nil {
	return fmt.Errorf("couldn't marshal ssh_config: %w", err)
	}
	if err := f.Truncate(0); err != nil {
	return fmt.Errorf("couldn't truncate ssh_config: %w", err)
	}
	if _, err := f.Seek(0, 0); err != nil {
	return fmt.Errorf("couldn't seek to beginning of ssh_config: %w", err)
	}
	if _, err := f.Write(cfgBytes); err != nil {
	return fmt.Errorf("couldn't write ssh_config: %w", err)
	}
	return nil
	}