nomad/command/setup_vault.go

// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: BUSL-1.1

package command

import (
	_ "embed"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"os"
	"slices"
	"strings"

	"github.com/dustin/go-humanize/english"
	"github.com/hashicorp/vault/api"
	"github.com/mitchellh/cli"
	"github.com/posener/complete"
)

// Ensure SetupVaultCommand satisfies the cli.Command interface.
var _ cli.Command = &SetupVaultCommand{}

//go:embed asset/vault-wi-default-auth-method-config.json
var vaultAuthConfigBody []byte

//go:embed asset/vault-wi-default-policy.hcl
var vaultPolicyBody []byte

//go:embed asset/vault-wi-default-role.json
var vaultRoleBody []byte

const (
	vaultRole       = "nomad-workloads"
	vaultPolicyName = "nomad-workloads"
	vaultNamespace  = "nomad-workloads"
	vaultAud        = "vault.io"
	vaultPath       = "jwt-nomad"
)

type SetupVaultCommand struct {
	Meta

	vClient  *api.Client
	vLogical *api.Logical
	ns       string

	jwksURL        string
	jwksCACertPath string

	destroy bool
	autoYes bool

	// Options for -check.
	check   bool
	json    bool
	tmpl    string
	verbose bool
}

// Help satisfies the cli.Command Help function.
func (s *SetupVaultCommand) Help() string {
	helpText := `
Usage: nomad setup vault [options]

  This command sets up Vault for allowing Nomad workloads to authenticate
  themselves using Workload Identity.

  This command requires acl:write permissions for Vault and respects
  VAULT_TOKEN, VAULT_ADDR, and other Vault-related environment variables
  as documented in https://developer.hashicorp.com/vault/docs/commands#environment-variables.

  The -check option can be used to verify if the Nomad cluster is ready to
  migrate to use Workload Identities with Vault. This option requires
  operator:read permission for Nomad.

  WARNING: This command is an experimental feature and may change its behavior
  in future versions of Nomad.

Setup Vault options:

  -jwks-url <url>
    URL of Nomad's JWKS endpoint contacted by Vault to verify JWT
    signatures. Defaults to http://localhost:4646/.well-known/jwks.json.

  -jwks-ca-file <path>
    Path to a CA certificate file that will be used to validate the
    JWKS URL if it uses TLS

  -destroy
    Removes all configuration components this command created from the
    Vault cluster.

  -y
    Automatically answers "yes" to all the questions, making the setup
    non-interactive. Defaults to "false".

  -check
    Verify if the Nomad cluster is ready to migrate to Workload Identities.

Setup Vault options when using -check:

  -json
    Output migration status information in its JSON format.

  -t
    Format and display migration status information using a Go template.

  -verbose
    Display full information.

  ` + generalOptionsUsage(usageOptsDefault|usageOptsNoNamespace)

	return strings.TrimSpace(helpText)
}

func (s *SetupVaultCommand) AutocompleteFlags() complete.Flags {
	return mergeAutocompleteFlags(s.Meta.AutocompleteFlags(FlagSetClient),
		complete.Flags{
			"-jwks-url":     complete.PredictAnything,
			"-jwks-ca-file": complete.PredictAnything,
			"-destroy":      complete.PredictSet("true", "false"),
			"-y":            complete.PredictSet("true", "false"),

			// Options for -check.
			"-check":   complete.PredictSet("true", "false"),
			"-json":    complete.PredictSet("true", "false"),
			"-verbose": complete.PredictSet("true", "false"),
			"-t":       complete.PredictAnything,
		})
}

func (s *SetupVaultCommand) AutocompleteArgs() complete.Predictor {
	return complete.PredictNothing
}

// Synopsis satisfies the cli.Command Synopsis function.
func (s *SetupVaultCommand) Synopsis() string { return "Setup a Vault cluster for Nomad integration" }

// Name returns the name of this command.
func (s *SetupVaultCommand) Name() string { return "setup vault" }

// Run satisfies the cli.Command Run function.
func (s *SetupVaultCommand) Run(args []string) int {

	flags := s.Meta.FlagSet(s.Name(), FlagSetClient)
	flags.Usage = func() { s.Ui.Output(s.Help()) }
	flags.BoolVar(&s.destroy, "destroy", false, "")
	flags.BoolVar(&s.autoYes, "y", false, "")
	flags.StringVar(&s.jwksURL, "jwks-url", "http://localhost:4646/.well-known/jwks.json", "")
	flags.StringVar(&s.jwksCACertPath, "jwks-ca-file", "", "")

	// Options for -check.
	flags.BoolVar(&s.check, "check", false, "")
	flags.BoolVar(&s.json, "json", false, "")
	flags.BoolVar(&s.verbose, "verbose", false, "")
	flags.StringVar(&s.tmpl, "t", "", "")

	if err := flags.Parse(args); err != nil {
		return 1
	}

	// Check that we got no arguments.
	if len(flags.Args()) != 0 {
		s.Ui.Error("This command takes no arguments")
		s.Ui.Error(commandErrorText(s))
		return 1
	}

	if s.check {
		return s.checkUpgrade()
	} else {
		// Verify that -check flags are not set.
		var invalid []string
		if s.json {
			invalid = append(invalid, "-json")
		}
		if s.verbose {
			invalid = append(invalid, "-verbose")
		}
		if s.tmpl != "" {
			invalid = append(invalid, "-t")
		}

		if len(invalid) > 0 {
			s.Ui.Error(fmt.Sprintf(
				"The %s %s can only be used with -check",
				english.OxfordWordSeries(invalid, "and"),
				english.PluralWord(len(invalid), "option", "options"),
			))
			s.Ui.Error(commandErrorText(s))
			return 1
		}
	}

	if !isTty() && !s.autoYes {
		s.Ui.Error("This command requires -y option when running in non-interactive mode")
		return 1
	}

	if !s.destroy {
		s.Ui.Output(`
This command will walk you through configuring all the components required for
Nomad workloads to authenticate themselves against Vault ACL using their
respective workload identities.

First we need to connect to Vault.
`)
	}

	clientCfg := api.DefaultConfig()
	if !s.autoYes {
		if !s.askQuestion(fmt.Sprintf("Is %q the correct address of your Vault cluster? [Y/n]", clientCfg.Address)) {
			s.Ui.Warn(`
Please set the VAULT_ADDR environment variable to your Vault cluster address and re-run the command.`)
			return 0
		}
	}

	// Get the Vault client.
	var err error
	s.vClient, err = api.NewClient(clientCfg)
	if err != nil {
		s.Ui.Error(fmt.Sprintf("Error initializing Vault client: %s", err))
		return 1
	}
	s.vLogical = s.vClient.Logical()

	// ent check: if we're not in empty namespace or the license check returns
	// non-nil (license checks will only ever work from default namespace),
	// we're connected to ent
	var ent bool
	clientNamespace := s.vClient.Namespace()
	license, _ := s.vClient.Logical().Read("/sys/license/status")
	ent = clientNamespace != "" || license != nil

	// Setup Vault client namespace.
	if ent {
		if clientNamespace != "" {
			// Confirm VAULT_NAMESPACE will be used.
			if !s.autoYes {
				if !s.askQuestion(fmt.Sprintf("Is %q the correct Vault namespace to use? [Y/n]", clientNamespace)) {
					s.Ui.Warn(`
Please set the VAULT_NAMESPACE environment variable to the Vault namespace to use and re-run the command.`)
					return 0
				}
			}
			s.ns = clientNamespace
		} else {
			// Set default namespace if VAULT_NAMESPACE is not defined.
			s.ns = vaultNamespace
			s.vClient.SetNamespace(s.ns)
		}
	}

	if s.destroy {
		return s.removeConfiguredComponents()
	}

	/*
		Namespace creation and setup
	*/
	if ent {
		namespaceMsg := `
Since you're running Vault Enterprise, we will additionally create
a namespace %q and create all configuration within that namespace.
`
		if s.namespaceExists(s.ns, false) {
			s.Ui.Info(fmt.Sprintf("[✔] Namespace %q already exists.", s.ns))
		} else {
			s.Ui.Output(fmt.Sprintf(namespaceMsg, s.ns))

			if !s.autoYes && !s.askQuestion(
				fmt.Sprintf("Create the namespace %q in your Vault cluster? [Y/n]", s.ns)) {
				s.handleNo()
			}

			err = s.createNamespace(s.ns)
			if err != nil {
				s.Ui.Error(err.Error())
				return 1
			}
		}
	}

	/*
		Auth method creation
	*/
	s.Ui.Output(`
We will now enable the JWT credential backend and create a JWT auth method that
Nomad workloads will use.
`)

	if s.authMethodExists() {
		s.Ui.Info(fmt.Sprintf("[✔] JWT auth method %q already exists.", vaultPath))
	} else {

		s.Ui.Output("This is the method configuration:\n")
		authMethodConf, err := s.renderAuthMethod()
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}
		jsConf, _ := json.MarshalIndent(authMethodConf, "", "    ")

		s.Ui.Output(string(jsConf))

		if !s.autoYes && !s.askQuestion("Create JWT auth method in your Vault cluster? [Y/n]") {
			s.handleNo()
		}

		err = s.createAuthMethod(authMethodConf)
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}
	}

	/*
		Policy & role creation
	*/
	s.Ui.Output(`
We need to create a role that Nomad workloads will assume while authenticating,
and a policy associated with that role.
	`)

	if s.policyExists() {
		s.Ui.Info(fmt.Sprintf("[✔] Policy %q already exists.", vaultPolicyName))
	} else {
		s.Ui.Output(fmt.Sprintf(`
These are the rules for the policy %q that we will create. It uses a templated
policy to allow Nomad tasks to access secrets in the path
"secrets/data/<job namespace>/<job name>":
`, vaultPolicyName))

		policyBody, err := s.renderPolicy()
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}
		s.Ui.Output(policyBody)

		if !s.autoYes && !s.askQuestion("Create the above policy in your Vault cluster? [Y/n]") {
			s.handleNo()
		}

		err = s.createPolicy(policyBody)
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}
	}

	if s.roleExists() {
		s.Ui.Info(fmt.Sprintf("[✔] Role %q already exists.", vaultRole))
	} else {
		s.Ui.Output(fmt.Sprintf(`
We will now create an ACL role called %q associated with the policy above.
`,
			vaultRole))

		roleBody, err := s.renderRole()
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}

		roleJS, _ := json.MarshalIndent(roleBody, "", "    ")
		s.Ui.Output(string(roleJS))

		if !s.autoYes && !s.askQuestion("Create role in your Vault cluster? [Y/n]") {
			s.handleNo()
		}

		err = s.createRole(roleBody)
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}
	}

	s.Ui.Output(`
Congratulations, your Vault cluster is now setup and ready to accept Nomad
workloads with Workload Identity!

You need to adjust your Nomad client configuration in the following way:

vault {
  enabled = true
  address = "<Vault address>"

  # Vault Enterprise only.
  # namespace = "<namespace>"

  jwt_auth_backend_path = "jwt-nomad/"
}

And your Nomad server configuration in the following way:

vault {
  enabled = true

  default_identity {
    aud = ["vault.io"]
    ttl = "1h"
  }
}`)
	return 0
}

func (s *SetupVaultCommand) roleExists() bool {
	existingRoles, _ := s.vLogical.List(fmt.Sprintf("/auth/%s/role", vaultPath))
	if existingRoles != nil {
		return slices.Contains(existingRoles.Data["keys"].([]any), vaultRole)
	}
	return false
}

func (s *SetupVaultCommand) renderRole() (map[string]any, error) {
	role := map[string]any{}
	err := json.Unmarshal(vaultRoleBody, &role)
	if err != nil {
		return role, fmt.Errorf("[✘] Role data could not be deserialized: %w", err)
	}

	role["bound_audiences"] = vaultAud

	return role, nil
}

func (s *SetupVaultCommand) createRole(role map[string]any) error {
	buf, err := json.Marshal(role)
	if err != nil {
		return fmt.Errorf("[✘] Role could not be interpolated with args: %w", err)
	}

	path := fmt.Sprintf("auth/%s/role/%s", vaultPath, vaultRole)

	_, err = s.vLogical.WriteBytes(path, buf)
	if err != nil {
		return fmt.Errorf("[✘] Could not create Vault role: %w", err)
	}

	s.Ui.Info(fmt.Sprintf("[✔] Created role %q.", vaultRole))
	return nil
}

func (s *SetupVaultCommand) policyExists() bool {
	existingPolicies, _ := s.vClient.Sys().ListPolicies()
	return slices.Contains(existingPolicies, vaultPolicyName)
}

func (s *SetupVaultCommand) renderPolicy() (string, error) {
	secret, err := s.vLogical.Read("sys/auth/" + vaultPath)
	if err != nil {
		return "", fmt.Errorf("[✘] Could not retrieve JWT accessor: %w", err)
	}
	accessor := secret.Data["accessor"].(string)

	policyTextStr := string(vaultPolicyBody)
	return strings.ReplaceAll(policyTextStr, "auth_jwt_X", accessor), nil
}

func (s *SetupVaultCommand) createPolicy(policyText string) error {
	encoded := base64.StdEncoding.EncodeToString([]byte(policyText))
	policyBody := fmt.Sprintf(`{"policy": "%s"}`, encoded)
	buf := []byte(policyBody)

	path := "sys/policies/acl/" + vaultPolicyName
	_, err := s.vLogical.WriteBytes(path, buf)
	if err != nil {
		return fmt.Errorf("[✘] Could not create Vault policy: %w", err)
	}

	s.Ui.Info(fmt.Sprintf("[✔] Created policy %q.", vaultPolicyName))

	return nil
}

func (s *SetupVaultCommand) authMethodExists() bool {
	existingConf, _ := s.vLogical.Read(fmt.Sprintf("/auth/%s/config", vaultPath))
	return existingConf != nil
}

func (s *SetupVaultCommand) renderAuthMethod() (map[string]any, error) {
	authConfig := map[string]any{}
	err := json.Unmarshal(vaultAuthConfigBody, &authConfig)
	if err != nil {
		return nil, fmt.Errorf("default auth config text could not be deserialized: %v", err)
	}

	authConfig["jwks_url"] = s.jwksURL
	authConfig["default_role"] = vaultRole

	if s.jwksCACertPath != "" {
		caCert, err := os.ReadFile(s.jwksCACertPath)
		if err != nil {
			return nil, fmt.Errorf("could not read -jwks-certfile: %v", err)
		}
		authConfig["jwks_ca_pem"] = string(caCert)
	}

	return authConfig, nil
}

func (s *SetupVaultCommand) createAuthMethod(authConfig map[string]any) error {
	err := s.vClient.Sys().EnableAuthWithOptions(vaultPath, &api.MountInput{Type: "jwt"})
	if err != nil {
		return fmt.Errorf("[✘] Could not enable JWT credential backend: %w", err)
	}

	buf, err := json.Marshal(authConfig)
	if err != nil {
		return fmt.Errorf("auth method could not be interpolated with args: %w", err)
	}
	_, err = s.vLogical.WriteBytes(fmt.Sprintf("auth/%s/config", vaultPath), buf)
	if err != nil {
		if strings.Contains(err.Error(), "error checking jwks URL") {
			s.Ui.Error(fmt.Sprintf(
				"error: Nomad JWKS endpoint unreachable, verify that Nomad is running and that the JWKS URL %s is reachable by Vault", s.jwksURL,
			))
			os.Exit(1)
		}
		return fmt.Errorf("[✘] Could not create Vault auth method: %w", err)
	}

	s.Ui.Info(fmt.Sprintf("[✔] Created JWT auth method %q.", vaultPath))
	return nil
}

// namespaceExists takes checks if ns exists. if destroy is true, it will check
// for custom metadata presence to prevent deleting a namespace we didn't
// create.
func (s *SetupVaultCommand) namespaceExists(ns string, destroy bool) bool {
	s.vClient.SetNamespace("")
	defer s.vClient.SetNamespace(s.ns)

	existingNamespace, _ := s.vLogical.Read(fmt.Sprintf("/sys/namespaces/%s", ns))
	if destroy && existingNamespace != nil {
		if m, ok := existingNamespace.Data["custom_metadata"]; ok {
			if mm, ok := m.(map[string]any)["created-by"]; ok {
				return mm == "nomad-setup"
			}
		}
	} else {
		return existingNamespace != nil
	}
	return false
}

func (s *SetupVaultCommand) createNamespace(ns string) error {
	s.vClient.SetNamespace("")
	defer s.vClient.SetNamespace(s.ns)

	_, err := s.vLogical.Write(
		"/sys/namespaces/"+ns,
		map[string]any{
			"custom_metadata": map[string]string{
				"created-by": "nomad-setup",
			},
		},
	)
	if err != nil {
		return fmt.Errorf("[✘] Could not write namespace %q: %w", ns, err)
	}
	s.Ui.Info(fmt.Sprintf("[✔] Created namespace %q.", ns))
	return nil
}

// askQuestion asks question to user until they provide a valid response.
func (s *SetupVaultCommand) askQuestion(question string) bool {
	for {
		answer, err := s.Ui.Ask(s.Colorize().Color(fmt.Sprintf("[?] %s", question)))
		if err != nil {
			if err.Error() != "interrupted" {
				s.Ui.Output(err.Error())
				os.Exit(1)
			}
			os.Exit(0)
		}

		switch strings.TrimSpace(strings.ToLower(answer)) {
		case "", "y", "yes":
			return true
		case "n", "no":
			return false
		default:
			s.Ui.Output(fmt.Sprintf(`%q is not a valid response, please answer "yes" or "no".`, answer))
			continue
		}
	}
}

func (s *SetupVaultCommand) handleNo() {
	s.Ui.Warn(`
By answering "no" to any of these questions, you are risking an incorrect Vault
cluster configuration. Nomad workloads with Workload Identity will not be able
to authenticate unless you create missing configuration yourself.
 `)

	exitCode := 0
	if s.autoYes || s.askQuestion("Remove everything this command creates? [Y/n]") {
		exitCode = s.removeConfiguredComponents()
	}

	s.Ui.Output(s.Colorize().Color(`
Vault cluster has [bold][underline]not[reset] been configured for authenticating Nomad tasks and
services using workload identities.

Run the command again to finish the configuration process.`))
	os.Exit(exitCode)
}

func (s *SetupVaultCommand) removeConfiguredComponents() int {
	s.vClient.SetNamespace(s.ns)
	exitCode := 0
	componentsToRemove := map[string]string{}

	if s.policyExists() {
		componentsToRemove["Policy"] = vaultPolicyName
	}
	if s.roleExists() {
		componentsToRemove["Role"] = vaultRole
	}
	if s.authMethodExists() {
		componentsToRemove["JWT auth method"] = vaultPath
	}
	if s.namespaceExists(s.ns, true) {
		componentsToRemove["Namespace"] = s.ns
	}

	if len(componentsToRemove) == 0 {
		s.Ui.Output("Nothing to delete.")
		return 0
	}

	q := `The following items will be deleted:
%s`
	if !s.autoYes {
		s.Ui.Warn(fmt.Sprintf(q, printMapOfStrings(componentsToRemove)))
	}

	if s.autoYes || s.askQuestion("Remove all the items listed above? [Y/n]") {

		if policy, ok := componentsToRemove["Policy"]; ok {
			err := s.vClient.Sys().DeletePolicy(policy)
			if err != nil {
				s.Ui.Error(fmt.Sprintf("[✘] Failed to delete policy %q: %v", policy, err.Error()))
				exitCode = 1
			} else {
				s.Ui.Info(fmt.Sprintf("[✔] Deleted policy %q.", policy))
			}
		}

		if role, ok := componentsToRemove["Role"]; ok {
			_, err := s.vLogical.Delete(fmt.Sprintf("/auth/%s/role/%s", vaultPath, role))
			if err != nil {
				s.Ui.Error(fmt.Sprintf("[✘] Failed to delete role %q: %v", role, err.Error()))
				exitCode = 1
			} else {
				s.Ui.Info(fmt.Sprintf("[✔] Deleted role %q.", role))
			}
		}

		if _, ok := componentsToRemove["JWT auth method"]; ok {
			if err := s.vClient.Sys().DisableAuth(vaultPath); err != nil {
				s.Ui.Error(fmt.Sprintf("[✘] Failed to disable JWT auth method %q %v", vaultPath, err.Error()))
				exitCode = 1
			} else {
				s.Ui.Info(fmt.Sprintf("[✔] Disabled JWT auth method %q.", vaultPath))
			}
		}

		if ns, ok := componentsToRemove["Namespace"]; ok {
			s.vClient.SetNamespace("")
			_, err := s.vLogical.Delete(fmt.Sprintf("/sys/namespaces/%s", ns))
			if err != nil {
				s.Ui.Error(fmt.Sprintf("[✘] Failed to delete namespace %q: %v", ns, err.Error()))
				exitCode = 1
			} else {
				s.Ui.Info(fmt.Sprintf("[✔] Deleted namespace %q.", ns))
			}
		}
	}

	return exitCode
}

func (s *SetupVaultCommand) checkUpgrade() int {
	length := shortId
	if s.verbose {
		length = fullId
	}

	client, err := s.Meta.Client()
	if err != nil {
		s.Ui.Error(fmt.Sprintf("Error initializing client: %s", err))
		return 1
	}

	resp, _, err := client.Operator().UpgradeCheckVaultWorkloadIdentity(nil)
	if err != nil {
		s.Ui.Error(fmt.Sprintf("Error querying scheduler configuration: %s", err))
		return 1
	}

	// Output formatted option if requested.
	if s.json || len(s.tmpl) > 0 {
		out, err := Format(s.json, s.tmpl, resp)
		if err != nil {
			s.Ui.Error(err.Error())
			return 1
		}

		s.Ui.Output(out)
		return 0
	}

	if resp.Ready() {
		s.Ui.Output("Nomad cluster is ready to use workload identities with Vault.")
		return 0
	}

	if len(resp.JobsWithoutVaultIdentity) != 0 {
		s.Ui.Output(s.Colorize().Color(`
[bold]Jobs Without Workload Identity for Vault[reset]
The following jobs access Vault but are not configured for workload identity.

You should redeploy them before fully migrating to workload identities with
Vault to prevent unexpected errors if their tokens need to be recreated.

Refer to https://developer.hashicorp.com/nomad/s/vault-workload-identity-migration
for more information.
`))
		out := make([]string, len(resp.JobsWithoutVaultIdentity)+1)
		out[0] = "ID|Namespace|Type|Status"
		for i, job := range resp.JobsWithoutVaultIdentity {
			out[i+1] = fmt.Sprintf("%s|%s|%s|%s",
				limit(job.ID, length),
				job.Namespace,
				job.Type,
				job.Status,
			)
		}
		s.Ui.Output(formatList(out))
	}

	if len(resp.OutdatedNodes) != 0 {
		s.Ui.Output(s.Colorize().Color(`
[bold]Outdated Nodes[reset]
The following nodes are running a version of Nomad that does not support using
workload identities with Vault.

You should upgrade them to Nomad 1.7 before fully migrating to workload
identities with Vault to prevent unexpected errors if they receive allocations
for jobs that use Vault.

Refer to https://developer.hashicorp.com/nomad/s/vault-workload-identity-migration
for more information.
`))
		out := make([]string, len(resp.OutdatedNodes)+1)
		out[0] = "ID|Name|Address|Version|Drain|Eligibility|Status"
		for i, node := range resp.OutdatedNodes {
			out[i+1] = fmt.Sprintf("%s|%s|%s|%s|%v|%s|%s",
				limit(node.ID, length),
				node.Name,
				node.Address,
				node.Version,
				node.Drain,
				node.SchedulingEligibility,
				node.Status,
			)
		}
		s.Ui.Output(formatList(out))
	}

	if len(resp.VaultTokens) != 0 {
		s.Ui.Output(s.Colorize().Color(`
[bold]Vault Tokens[reset]
The following Vault ACL tokens were created by Nomad but will not be
automatically revoked after migrating to workload identities. They will expire
once their TTL reaches zero.
`))
		out := make([]string, len(resp.VaultTokens)+1)
		out[0] = "Accessor ID|Allocation ID|Node ID|Configured TTL"
		for i, token := range resp.VaultTokens {
			out[i+1] = fmt.Sprintf("%s|%s|%s|%d",
				token.Accessor,
				limit(token.AllocID, length),
				limit(token.NodeID, length),
				token.CreationTTL,
			)
		}
		s.Ui.Output(formatList(out))
	}

	return 0
}

func printMapOfStrings(m map[string]string) string {
	var output string

	for k, v := range m {
		if v != "" {
			output += fmt.Sprintf("  * %s: %q\n", k, v)
		} else {
			output += fmt.Sprintf("  * %s\n", k)
		}
	}

	return output
}