Add a couple more check templates and built-in checks (#6)

Author: viswajithiii

.golangci.yml

@@ -55,6 +55,7 @@ linters-settings:
       - importShadow
       - emptyStringTest
       - hugeParam
+      - rangeValCopy
   nolintlint:
     allow-leading-space: false # require machine-readable nolint directives (i.e. with no leading space)
     allow-unused: false # report any unused nolint directives

docs/generated/checks.md

@@ -2,6 +2,8 @@ The following table enumerates built-in checks:
 
 | Name | Enabled by default | Description | Template | Parameters |
 | ---- | ------------------ | ----------- | -------- | ---------- |
- | env-var-secret | No | Alert on objects using a secret in an environment variable | env-var |- `name`: `.*secret.*` <br />|
+ | env-var-secret | Yes | Alert on objects using a secret in an environment variable | env-var |- `name`: `.*secret.*` <br />|
+ | no-read-only-root-fs | Yes | Alert on containers not running with a read-only root filesystem | read-only-root-fs | none |
  | privileged-container | Yes | Alert on deployments with containers running in privileged mode | privileged | none |
  | required-label-owner | No | Alert on objects without the 'owner' label | required-label |- `key`: `owner` <br />|
+ | run-as-non-root | Yes | Alert on containers not set to runAsNonRoot | run-as-non-root | none |

docs/generated/templates.md

@@ -4,4 +4,6 @@ The following table enumerates supported check templates:
 | ---- | ----------- | ----------------- | ---------- |
  | env-var | Flag environment variables that match the provided patterns | DeploymentLike |- `name` (required): A regex for the env var name <br />- `value`: A regex for the env var value <br />|
  | privileged | Flag privileged containers | DeploymentLike | none |
+ | read-only-root-fs | Flag containers without read-only root file systems | DeploymentLike | none |
  | required-label | Flag objects not carrying at least one label matching the provided patterns | Any |- `key` (required): A regex for the key of the required label <br />- `value`: A regex for the value of the required label <br />|
+ | run-as-non-root | Flag containers set to run as a root user | DeploymentLike | none |

internal/builtinchecks/yamls/read-only-root-fs.yaml

@@ -0,0 +1,6 @@
+name: "no-read-only-root-fs"
+description: "Alert on containers not running with a read-only root filesystem"
+scope:
+  objectKinds:
+    - DeploymentLike
+template: "read-only-root-fs"

internal/builtinchecks/yamls/run-as-non-root.yaml

@@ -0,0 +1,6 @@
+name: "run-as-non-root"
+description: "Alert on containers not set to runAsNonRoot"
+scope:
+  objectKinds:
+    - DeploymentLike
+template: "run-as-non-root"

internal/defaultchecks/default_checks.go

@@ -8,5 +8,8 @@ var (
 	// List is the list of built-in checks that are enabled by default.
 	List = set.NewFrozenStringSet(
 		"privileged-container",
+		"env-var-secret",
+		"no-read-only-root-fs",
+		"run-as-non-root",
 	)
 )

internal/defaultchecks/default_test.go

@@ -0,0 +1,22 @@
+package defaultchecks
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"golang.stackrox.io/kube-linter/internal/builtinchecks"
+	"golang.stackrox.io/kube-linter/internal/set"
+)
+
+func TestListReferencesOnlyValidChecks(t *testing.T) {
+	allChecks, err := builtinchecks.List()
+	require.NoError(t, err)
+	allCheckNames := set.NewStringSet()
+	for _, check := range allChecks {
+		allCheckNames.Add(check.Name)
+	}
+	for _, defaultCheck := range List.AsSlice() {
+		assert.True(t, allCheckNames.Contains(defaultCheck), "default check %s invalid", defaultCheck)
+	}
+}

internal/templates/all/all.go

@@ -4,5 +4,7 @@ import (
 	// Import all check templates.
 	_ "golang.stackrox.io/kube-linter/internal/templates/envvar"
 	_ "golang.stackrox.io/kube-linter/internal/templates/privileged"
+	_ "golang.stackrox.io/kube-linter/internal/templates/readonlyrootfs"
 	_ "golang.stackrox.io/kube-linter/internal/templates/requiredlabel"
+	_ "golang.stackrox.io/kube-linter/internal/templates/runasnonroot"
 )

internal/templates/readonlyrootfs/template.go

@@ -0,0 +1,39 @@
+package readonlyrootfs
+
+import (
+	"fmt"
+
+	"golang.stackrox.io/kube-linter/internal/check"
+	"golang.stackrox.io/kube-linter/internal/diagnostic"
+	"golang.stackrox.io/kube-linter/internal/extract"
+	"golang.stackrox.io/kube-linter/internal/lintcontext"
+	"golang.stackrox.io/kube-linter/internal/objectkinds"
+	"golang.stackrox.io/kube-linter/internal/templates"
+)
+
+func init() {
+	templates.Register(check.Template{
+		Name:        "read-only-root-fs",
+		Description: "Flag containers without read-only root file systems",
+		SupportedObjectKinds: check.ObjectKindsDesc{
+			ObjectKinds: []string{objectkinds.DeploymentLike},
+		},
+		Parameters: nil,
+		Instantiate: func(_ map[string]string) (check.Func, error) {
+			return func(_ *lintcontext.LintContext, object lintcontext.Object) []diagnostic.Diagnostic {
+				podSpec, found := extract.PodSpec(object.K8sObject)
+				if !found {
+					return nil
+				}
+				var results []diagnostic.Diagnostic
+				for _, container := range podSpec.Containers {
+					sc := container.SecurityContext
+					if sc == nil || sc.ReadOnlyRootFilesystem == nil || !*sc.ReadOnlyRootFilesystem {
+						results = append(results, diagnostic.Diagnostic{Message: fmt.Sprintf("container %q does not have a read-only root file system", container.Name)})
+					}
+				}
+				return results
+			}, nil
+		},
+	})
+}

internal/templates/runasnonroot/template.go

@@ -0,0 +1,72 @@
+package runasnonroot
+
+import (
+	"fmt"
+
+	"golang.stackrox.io/kube-linter/internal/check"
+	"golang.stackrox.io/kube-linter/internal/diagnostic"
+	"golang.stackrox.io/kube-linter/internal/extract"
+	"golang.stackrox.io/kube-linter/internal/lintcontext"
+	"golang.stackrox.io/kube-linter/internal/objectkinds"
+	"golang.stackrox.io/kube-linter/internal/templates"
+	v1 "k8s.io/api/core/v1"
+)
+
+func effectiveRunAsNonRoot(podSC *v1.PodSecurityContext, containerSC *v1.SecurityContext) bool {
+	if containerSC != nil && containerSC.RunAsNonRoot != nil {
+		return *containerSC.RunAsNonRoot
+	}
+	if podSC != nil && podSC.RunAsNonRoot != nil {
+		return *podSC.RunAsNonRoot
+	}
+	return false
+}
+
+func effectiveRunAsUser(podSC *v1.PodSecurityContext, containerSC *v1.SecurityContext) *int64 {
+	if containerSC != nil && containerSC.RunAsUser != nil {
+		return containerSC.RunAsUser
+	}
+	if podSC != nil {
+		return podSC.RunAsUser
+	}
+	return nil
+}
+
+func init() {
+	templates.Register(check.Template{
+		Name:        "run-as-non-root",
+		Description: "Flag containers set to run as a root user",
+		SupportedObjectKinds: check.ObjectKindsDesc{
+			ObjectKinds: []string{objectkinds.DeploymentLike},
+		},
+		Parameters: nil,
+		Instantiate: func(_ map[string]string) (check.Func, error) {
+			return func(_ *lintcontext.LintContext, object lintcontext.Object) []diagnostic.Diagnostic {
+				podSpec, found := extract.PodSpec(object.K8sObject)
+				if !found {
+					return nil
+				}
+				var results []diagnostic.Diagnostic
+				for _, container := range podSpec.Containers {
+					runAsUser := effectiveRunAsUser(podSpec.SecurityContext, container.SecurityContext)
+					// runAsUser explicitly set to non-root. All good.
+					if runAsUser != nil && *runAsUser > 0 {
+						continue
+					}
+					runAsNonRoot := effectiveRunAsNonRoot(podSpec.SecurityContext, container.SecurityContext)
+					if runAsNonRoot {
+						// runAsNonRoot set, but runAsUser set to 0. This will result in a runtime failure.
+						if runAsUser != nil && *runAsUser == 0 {
+							results = append(results, diagnostic.Diagnostic{
+								Message: fmt.Sprintf("container %q is set to runAsNonRoot, but runAsUser set to %d", container.Name, *runAsUser),
+							})
+						}
+						continue
+					}
+					results = append(results, diagnostic.Diagnostic{Message: fmt.Sprintf("container %q is not set to runAsNonRoot", container.Name)})
+				}
+				return results
+			}, nil
+		},
+	})
+}