getHostByName Function Information Disclosure

@@ -170,6 +170,7 @@ func addInstallFlags(cmd *cobra.Command, f *pflag.FlagSet, client *action.Instal
 	f.BoolVar(&client.Atomic, "atomic", false, "if set, the installation process deletes the installation on failure. The --wait flag will be set automatically if --atomic is used")
 	f.BoolVar(&client.SkipCRDs, "skip-crds", false, "if set, no CRDs will be installed. By default, CRDs are installed if not already present")
 	f.BoolVar(&client.SubNotes, "render-subchart-notes", false, "if set, render subchart notes along with the parent")
+	f.BoolVar(&client.EnableDNS, "enable-dns", false, "enable DNS lookups when rendering templates")
 	addValueOptionsFlags(f, valueOpts)
 	addChartPathOptionsFlags(f, &client.ChartPathOptions)
 

@@ -119,6 +119,7 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 					instClient.SubNotes = client.SubNotes
 					instClient.Description = client.Description
 					instClient.DependencyUpdate = client.DependencyUpdate
+					instClient.EnableDNS = client.EnableDNS
 
 					rel, err := runInstall(args, instClient, valueOpts, out)
 					if err != nil {
@@ -232,6 +233,7 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 	f.BoolVar(&client.SubNotes, "render-subchart-notes", false, "if set, render subchart notes along with the parent")
 	f.StringVar(&client.Description, "description", "", "add a custom description")
 	f.BoolVar(&client.DependencyUpdate, "dependency-update", false, "update dependencies if they are missing before installing the chart")
+	f.BoolVar(&client.EnableDNS, "enable-dns", false, "enable DNS lookups when rendering templates")
 	addChartPathOptionsFlags(f, &client.ChartPathOptions)
 	addValueOptionsFlags(f, valueOpts)
 	bindOutputFlag(cmd, &outfmt)

@@ -101,8 +101,9 @@ type Configuration struct {
 //
 // TODO: This function is badly in need of a refactor.
 // TODO: As part of the refactor the duplicate code in cmd/helm/template.go should be removed
-//       This code has to do with writing files to disk.
-func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun bool) ([]*release.Hook, *bytes.Buffer, string, error) {
+//
+//	This code has to do with writing files to disk.
+func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun, enableDNS bool) ([]*release.Hook, *bytes.Buffer, string, error) {
 	hs := []*release.Hook{}
 	b := bytes.NewBuffer(nil)
 
@@ -130,9 +131,13 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 		if err != nil {
 			return hs, b, "", err
 		}
-		files, err2 = engine.RenderWithClient(ch, values, restConfig)
+		e := engine.New(restConfig)
+		e.EnableDNS = enableDNS
+		files, err2 = e.Render(ch, values)
 	} else {
-		files, err2 = engine.Render(ch, values)
+		var e engine.Engine
+		e.EnableDNS = enableDNS
+		files, err2 = e.Render(ch, values)
 	}
 
 	if err2 != nil {

@@ -97,6 +97,8 @@ type Install struct {
 	APIVersions chartutil.VersionSet
 	// Used by helm template to render charts with .Release.IsUpgrade. Ignored if Dry-Run is false
 	IsUpgrade bool
+	// Enable DNS lookups when rendering templates
+	EnableDNS bool
 	// Used by helm template to add the release as part of OutputDir path
 	// OutputDir/<ReleaseName>
 	UseReleaseName bool
@@ -257,7 +259,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	rel := i.createRelease(chrt, vals)
 
 	var manifestDoc *bytes.Buffer
-	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun)
+	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun, i.EnableDNS)
 	// Even for errors, attach this if available
 	if manifestDoc != nil {
 		rel.Manifest = manifestDoc.String()
@@ -457,10 +459,10 @@ func (i *Install) failRelease(rel *release.Release, err error) (*release.Release
 //
 // Roughly, this will return an error if name is
 //
-//	- empty
-//	- too long
-//	- already in use, and not deleted
-//	- used by a deleted release, and i.Replace is false
+//   - empty
+//   - too long
+//   - already in use, and not deleted
+//   - used by a deleted release, and i.Replace is false
 func (i *Install) availableName() error {
 	start := i.ReleaseName
 

@@ -103,6 +103,8 @@ type Upgrade struct {
 	DependencyUpdate bool
 	// Lock to control raceconditions when the process receives a SIGTERM
 	Lock sync.Mutex
+	// Enable DNS lookups when rendering templates
+	EnableDNS bool
 }
 
 type resultMessage struct {
@@ -231,7 +233,7 @@ func (u *Upgrade) prepareUpgrade(name string, chart *chart.Chart, vals map[strin
 		return nil, nil, err
 	}
 
-	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun)
+	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun, u.EnableDNS)
 	if err != nil {
 		return nil, nil, err
 	}

@@ -42,6 +42,15 @@ type Engine struct {
 	LintMode bool
 	// the rest config to connect to the kubernetes api
 	config *rest.Config
+	// EnableDNS tells the engine to allow DNS lookups when rendering templates
+	EnableDNS bool
+}
+
+// New creates a new instance of Engine using the passed in rest config.
+func New(config *rest.Config) Engine {
+	return Engine{
+		config: config,
+	}
 }
 
 // Render takes a chart, optional values, and value overrides, and attempts to render the Go templates.
@@ -189,6 +198,14 @@ func (e Engine) initFunMap(t *template.Template, referenceTpls map[string]render
 		funcMap["lookup"] = NewLookupFunction(e.config)
 	}
 
+	// When DNS lookups are not enabled override the sprig function and return
+	// an empty string.
+	if !e.EnableDNS {
+		funcMap["getHostByName"] = func(name string) string {
+			return ""
+		}
+	}
+
 	t.Funcs(funcMap)
 }
 

@@ -18,6 +18,7 @@ package engine
 
 import (
 	"fmt"
+	"path"
 	"strings"
 	"sync"
 	"testing"
@@ -89,6 +90,7 @@ func TestRender(t *testing.T) {
 			{Name: "templates/test2", Data: []byte("{{.Values.global.callme | lower }}")},
 			{Name: "templates/test3", Data: []byte("{{.noValue}}")},
 			{Name: "templates/test4", Data: []byte("{{toJson .Values}}")},
+			{Name: "templates/test5", Data: []byte("{{getHostByName \"helm.sh\"}}")},
 		},
 		Values: map[string]interface{}{"outer": "DEFAULT", "inner": "DEFAULT"},
 	}
@@ -117,6 +119,7 @@ func TestRender(t *testing.T) {
 		"moby/templates/test2": "ishmael",
 		"moby/templates/test3": "",
 		"moby/templates/test4": `{"global":{"callme":"Ishmael"},"inner":"inn","outer":"spouter"}`,
+		"moby/templates/test5": "",
 	}
 
 	for name, data := range expect {
@@ -200,6 +203,42 @@ func TestRenderInternals(t *testing.T) {
 	}
 }
 
+func TestRenderWIthDNS(t *testing.T) {
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "moby",
+			Version: "1.2.3",
+		},
+		Templates: []*chart.File{
+			{Name: "templates/test1", Data: []byte("{{getHostByName \"helm.sh\"}}")},
+		},
+		Values: map[string]interface{}{},
+	}
+
+	vals := map[string]interface{}{
+		"Values": map[string]interface{}{},
+	}
+
+	v, err := chartutil.CoalesceValues(c, vals)
+	if err != nil {
+		t.Fatalf("Failed to coalesce values: %s", err)
+	}
+
+	var e Engine
+	e.EnableDNS = true
+	out, err := e.Render(c, v)
+	if err != nil {
+		t.Errorf("Failed to render templates: %s", err)
+	}
+
+	for _, val := range c.Templates {
+		fp := path.Join("moby", val.Name)
+		if out[fp] == "" {
+			t.Errorf("Expected IP address, got %q", out[fp])
+		}
+	}
+}
+
 func TestParallelRenderInternals(t *testing.T) {
 	// Make sure that we can use one Engine to run parallel template renders.
 	e := new(Engine)

@@ -170,6 +170,7 @@ func addInstallFlags(cmd *cobra.Command, f *pflag.FlagSet, client *action.Instal
 	f.BoolVar(&client.Atomic, "atomic", false, "if set, the installation process deletes the installation on failure. The --wait flag will be set automatically if --atomic is used")
 	f.BoolVar(&client.SkipCRDs, "skip-crds", false, "if set, no CRDs will be installed. By default, CRDs are installed if not already present")
 	f.BoolVar(&client.SubNotes, "render-subchart-notes", false, "if set, render subchart notes along with the parent")
+	f.BoolVar(&client.EnableDNS, "enable-dns", false, "enable DNS lookups when rendering templates")
 	addValueOptionsFlags(f, valueOpts)
 	addChartPathOptionsFlags(f, &client.ChartPathOptions)
 

@@ -119,6 +119,7 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 					instClient.SubNotes = client.SubNotes
 					instClient.Description = client.Description
 					instClient.DependencyUpdate = client.DependencyUpdate
+					instClient.EnableDNS = client.EnableDNS
 
 					rel, err := runInstall(args, instClient, valueOpts, out)
 					if err != nil {
@@ -232,6 +233,7 @@ func newUpgradeCmd(cfg *action.Configuration, out io.Writer) *cobra.Command {
 	f.BoolVar(&client.SubNotes, "render-subchart-notes", false, "if set, render subchart notes along with the parent")
 	f.StringVar(&client.Description, "description", "", "add a custom description")
 	f.BoolVar(&client.DependencyUpdate, "dependency-update", false, "update dependencies if they are missing before installing the chart")
+	f.BoolVar(&client.EnableDNS, "enable-dns", false, "enable DNS lookups when rendering templates")
 	addChartPathOptionsFlags(f, &client.ChartPathOptions)
 	addValueOptionsFlags(f, valueOpts)
 	bindOutputFlag(cmd, &outfmt)

@@ -101,8 +101,9 @@ type Configuration struct {
 //
 // TODO: This function is badly in need of a refactor.
 // TODO: As part of the refactor the duplicate code in cmd/helm/template.go should be removed
-//       This code has to do with writing files to disk.
-func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun bool) ([]*release.Hook, *bytes.Buffer, string, error) {
+//
+//	This code has to do with writing files to disk.
+func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Values, releaseName, outputDir string, subNotes, useReleaseName, includeCrds bool, pr postrender.PostRenderer, dryRun, enableDNS bool) ([]*release.Hook, *bytes.Buffer, string, error) {
 	hs := []*release.Hook{}
 	b := bytes.NewBuffer(nil)
 
@@ -130,9 +131,13 @@ func (cfg *Configuration) renderResources(ch *chart.Chart, values chartutil.Valu
 		if err != nil {
 			return hs, b, "", err
 		}
-		files, err2 = engine.RenderWithClient(ch, values, restConfig)
+		e := engine.New(restConfig)
+		e.EnableDNS = enableDNS
+		files, err2 = e.Render(ch, values)
 	} else {
-		files, err2 = engine.Render(ch, values)
+		var e engine.Engine
+		e.EnableDNS = enableDNS
+		files, err2 = e.Render(ch, values)
 	}
 
 	if err2 != nil {

@@ -97,6 +97,8 @@ type Install struct {
 	APIVersions chartutil.VersionSet
 	// Used by helm template to render charts with .Release.IsUpgrade. Ignored if Dry-Run is false
 	IsUpgrade bool
+	// Enable DNS lookups when rendering templates
+	EnableDNS bool
 	// Used by helm template to add the release as part of OutputDir path
 	// OutputDir/<ReleaseName>
 	UseReleaseName bool
@@ -257,7 +259,7 @@ func (i *Install) RunWithContext(ctx context.Context, chrt *chart.Chart, vals ma
 	rel := i.createRelease(chrt, vals)
 
 	var manifestDoc *bytes.Buffer
-	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun)
+	rel.Hooks, manifestDoc, rel.Info.Notes, err = i.cfg.renderResources(chrt, valuesToRender, i.ReleaseName, i.OutputDir, i.SubNotes, i.UseReleaseName, i.IncludeCRDs, i.PostRenderer, i.DryRun, i.EnableDNS)
 	// Even for errors, attach this if available
 	if manifestDoc != nil {
 		rel.Manifest = manifestDoc.String()
@@ -457,10 +459,10 @@ func (i *Install) failRelease(rel *release.Release, err error) (*release.Release
 //
 // Roughly, this will return an error if name is
 //
-//	- empty
-//	- too long
-//	- already in use, and not deleted
-//	- used by a deleted release, and i.Replace is false
+//   - empty
+//   - too long
+//   - already in use, and not deleted
+//   - used by a deleted release, and i.Replace is false
 func (i *Install) availableName() error {
 	start := i.ReleaseName
 

@@ -103,6 +103,8 @@ type Upgrade struct {
 	DependencyUpdate bool
 	// Lock to control raceconditions when the process receives a SIGTERM
 	Lock sync.Mutex
+	// Enable DNS lookups when rendering templates
+	EnableDNS bool
 }
 
 type resultMessage struct {
@@ -231,7 +233,7 @@ func (u *Upgrade) prepareUpgrade(name string, chart *chart.Chart, vals map[strin
 		return nil, nil, err
 	}
 
-	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun)
+	hooks, manifestDoc, notesTxt, err := u.cfg.renderResources(chart, valuesToRender, "", "", u.SubNotes, false, false, u.PostRenderer, u.DryRun, u.EnableDNS)
 	if err != nil {
 		return nil, nil, err
 	}

@@ -42,6 +42,15 @@ type Engine struct {
 	LintMode bool
 	// the rest config to connect to the kubernetes api
 	config *rest.Config
+	// EnableDNS tells the engine to allow DNS lookups when rendering templates
+	EnableDNS bool
+}
+
+// New creates a new instance of Engine using the passed in rest config.
+func New(config *rest.Config) Engine {
+	return Engine{
+		config: config,
+	}
 }
 
 // Render takes a chart, optional values, and value overrides, and attempts to render the Go templates.
@@ -189,6 +198,14 @@ func (e Engine) initFunMap(t *template.Template, referenceTpls map[string]render
 		funcMap["lookup"] = NewLookupFunction(e.config)
 	}
 
+	// When DNS lookups are not enabled override the sprig function and return
+	// an empty string.
+	if !e.EnableDNS {
+		funcMap["getHostByName"] = func(name string) string {
+			return ""
+		}
+	}
+
 	t.Funcs(funcMap)
 }
 

@@ -18,6 +18,7 @@ package engine
 
 import (
 	"fmt"
+	"path"
 	"strings"
 	"sync"
 	"testing"
@@ -89,6 +90,7 @@ func TestRender(t *testing.T) {
 			{Name: "templates/test2", Data: []byte("{{.Values.global.callme | lower }}")},
 			{Name: "templates/test3", Data: []byte("{{.noValue}}")},
 			{Name: "templates/test4", Data: []byte("{{toJson .Values}}")},
+			{Name: "templates/test5", Data: []byte("{{getHostByName \"helm.sh\"}}")},
 		},
 		Values: map[string]interface{}{"outer": "DEFAULT", "inner": "DEFAULT"},
 	}
@@ -117,6 +119,7 @@ func TestRender(t *testing.T) {
 		"moby/templates/test2": "ishmael",
 		"moby/templates/test3": "",
 		"moby/templates/test4": `{"global":{"callme":"Ishmael"},"inner":"inn","outer":"spouter"}`,
+		"moby/templates/test5": "",
 	}
 
 	for name, data := range expect {
@@ -200,6 +203,42 @@ func TestRenderInternals(t *testing.T) {
 	}
 }
 
+func TestRenderWIthDNS(t *testing.T) {
+	c := &chart.Chart{
+		Metadata: &chart.Metadata{
+			Name:    "moby",
+			Version: "1.2.3",
+		},
+		Templates: []*chart.File{
+			{Name: "templates/test1", Data: []byte("{{getHostByName \"helm.sh\"}}")},
+		},
+		Values: map[string]interface{}{},
+	}
+
+	vals := map[string]interface{}{
+		"Values": map[string]interface{}{},
+	}
+
+	v, err := chartutil.CoalesceValues(c, vals)
+	if err != nil {
+		t.Fatalf("Failed to coalesce values: %s", err)
+	}
+
+	var e Engine
+	e.EnableDNS = true
+	out, err := e.Render(c, v)
+	if err != nil {
+		t.Errorf("Failed to render templates: %s", err)
+	}
+
+	for _, val := range c.Templates {
+		fp := path.Join("moby", val.Name)
+		if out[fp] == "" {
+			t.Errorf("Expected IP address, got %q", out[fp])
+		}
+	}
+}
+
 func TestParallelRenderInternals(t *testing.T) {
 	// Make sure that we can use one Engine to run parallel template renders.
 	e := new(Engine)