Function firstConfiguredKeyPair

pkg/cmd/codespace/ssh.go:472–521

firstConfiguredKeyPair reads the effective configuration for a localhost connection and returns the first valid key pair which would be tried for authentication

(
	ctx context.Context,
	customConfigFile string,
	customHost string,
)

// firstConfiguredKeyPair reads the effective configuration for a localhost
// connection and returns the first valid key pair which would be tried for authentication
func firstConfiguredKeyPair(
	ctx context.Context,
	customConfigFile string,
	customHost string,
) (*ssh.KeyPair, error) {
	sshExe, err := safeexec.LookPath("ssh")
	if err != nil {
		return nil, fmt.Errorf("could not find ssh executable: %w", err)
	}

	// The -G option tells ssh to output the effective config for the given host, but not connect
	sshGArgs := []string{"-G"}

	if customConfigFile != "" {
		sshGArgs = append(sshGArgs, "-F", customConfigFile)
	}

	if customHost != "" {
		sshGArgs = append(sshGArgs, customHost)
	} else {
		sshGArgs = append(sshGArgs, "localhost")
	}

	sshGCmd := exec.CommandContext(ctx, sshExe, sshGArgs...)
	configBytes, err := sshGCmd.Output()
	if err != nil {
		return nil, fmt.Errorf("could not load ssh configuration: %w", err)
	}

	configLines := strings.Split(string(configBytes), "\n")
	for _, line := range configLines {
		line = strings.TrimSpace(line)

		if strings.HasPrefix(line, "identityfile ") {
			privateKeyPath := strings.SplitN(line, " ", 2)[1]

			keypair, err := keypairForPrivateKey(privateKeyPath)
			if errors.Is(err, errKeyFileNotFound) {
				continue
			}
			if err != nil {
				return nil, fmt.Errorf("loading ssh config: %w", err)
			}

			return keypair, nil
		}
	}

	return nil, errKeyFileNotFound
}

// keypairForPrivateKey returns the KeyPair with the specified private key if it and the public key both exist
func keypairForPrivateKey(privateKeyPath string) (*ssh.KeyPair, error) {