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policy.go
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policy.go
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package policy
import (
"context"
"encoding/json"
"errors"
"fmt"
"path"
"path/filepath"
"strings"
"github.com/aquasecurity/trivy-operator/pkg/configauditreport"
"github.com/aquasecurity/defsec/pkg/scanners"
"github.com/aquasecurity/defsec/pkg/scanners/rbac"
"github.com/go-logr/logr"
"github.com/liamg/memoryfs"
"github.com/aquasecurity/defsec/pkg/scan"
"github.com/aquasecurity/defsec/pkg/scanners/kubernetes"
"github.com/aquasecurity/defsec/pkg/scanners/options"
"github.com/aquasecurity/trivy-operator/pkg/kube"
"sigs.k8s.io/controller-runtime/pkg/client"
)
const (
keyPrefixPolicy = "policy."
keyPrefixLibrary = "library."
keySuffixKinds = ".kinds"
keySuffixRego = ".rego"
PoliciesNotFoundError = "no policies found"
)
const (
kindAny = "*"
kindWorkload = "Workload"
inputFolder = "inputs"
policiesFolder = "externalPolicies"
regoExt = "rego"
yamlExt = "yaml"
)
type Policies struct {
data map[string]string
log logr.Logger
cac configauditreport.ConfigAuditConfig
}
func NewPolicies(data map[string]string, cac configauditreport.ConfigAuditConfig, log logr.Logger) *Policies {
return &Policies{
data: data,
log: log,
cac: cac,
}
}
func (p *Policies) Libraries() map[string]string {
libs := make(map[string]string)
for key, value := range p.data {
if !strings.HasPrefix(key, keyPrefixLibrary) {
continue
}
if !strings.HasSuffix(key, keySuffixRego) {
continue
}
libs[key] = value
}
return libs
}
func (p *Policies) PoliciesByKind(kind string) (map[string]string, error) {
policies := make(map[string]string)
for key, value := range p.data {
if strings.HasSuffix(key, keySuffixRego) && strings.HasPrefix(key, keyPrefixPolicy) {
// Check if kinds were defined for this policy
kindsKey := strings.TrimSuffix(key, keySuffixRego) + keySuffixKinds
if _, ok := p.data[kindsKey]; !ok {
return nil, fmt.Errorf("kinds not defined for policy: %s", key)
}
}
if !strings.HasSuffix(key, keySuffixKinds) {
continue
}
for _, k := range strings.Split(value, ",") {
if k == kindWorkload && !kube.IsWorkload(kind) {
continue
}
if k != kindAny && k != kindWorkload && k != kind {
continue
}
policyKey := strings.TrimSuffix(key, keySuffixKinds) + keySuffixRego
var ok bool
policies[policyKey], ok = p.data[policyKey]
if !ok {
return nil, fmt.Errorf("expected policy not found: %s", policyKey)
}
}
}
return policies, nil
}
func (p *Policies) Hash(kind string) (string, error) {
modules, err := p.ModulesByKind(kind)
if err != nil {
return "", err
}
return kube.ComputeHash(modules), nil
}
func (p *Policies) ModulesByKind(kind string) (map[string]string, error) {
modules, err := p.PoliciesByKind(kind)
if err != nil {
return nil, err
}
for key, value := range p.Libraries() {
modules[key] = value
}
return modules, nil
}
func (p *Policies) ModulePolicyByKind(kind string) ([]string, error) {
modByKind, err := p.ModulesByKind(kind)
if err != nil {
return nil, err
}
policy := make([]string, 0, len(modByKind))
for _, mod := range modByKind {
policy = append(policy, mod)
}
return policy, nil
}
//Applicable check if policies exist either built in or via policies configmap
func (p *Policies) Applicable(resource client.Object) (bool, string, error) {
resourceKind := resource.GetObjectKind().GroupVersionKind().Kind
if resourceKind == "" {
return false, "", errors.New("resource kind must not be blank")
}
policies, err := p.PoliciesByKind(resourceKind)
if err != nil {
return false, "", err
}
if len(policies) == 0 && !p.cac.GetUseBuiltinRegoPolicies() {
return false, fmt.Sprintf("no policies found for kind %s", resource.GetObjectKind().GroupVersionKind().Kind), nil
}
return true, "", nil
}
//SupportedKind scan policies supported for this kind
func (p *Policies) SupportedKind(resource client.Object, rbacDEnable bool) (bool, error) {
resourceKind := resource.GetObjectKind().GroupVersionKind().Kind
if resourceKind == "" {
return false, errors.New("resource kind must not be blank")
}
for _, kind := range p.cac.GetSupportedConfigAuditKinds() {
if kind == resourceKind && !p.rbacDisabled(rbacDEnable, kind) {
return true, nil
}
}
return false, nil
}
func (p *Policies) rbacDisabled(rbacEnable bool, kind string) bool {
if !rbacEnable && kube.IsRoleTypes(kube.Kind(kind)) {
return true
}
return false
}
// Eval evaluates Rego policies with Kubernetes resource client.Object as input.
func (p *Policies) Eval(ctx context.Context, resource client.Object) (scan.Results, error) {
if resource == nil {
return nil, fmt.Errorf("resource must not be nil")
}
resourceKind := resource.GetObjectKind().GroupVersionKind().Kind
if resourceKind == "" {
return nil, fmt.Errorf("resource kind must not be blank")
}
externalPolicies, err := p.ModulePolicyByKind(resourceKind)
if err != nil {
return nil, fmt.Errorf("failed listing externalPolicies by kind: %s: %w", resourceKind, err)
}
memfs := memoryfs.New()
hasExternalPolicies := len(externalPolicies) > 0
if !hasExternalPolicies && !p.cac.GetUseBuiltinRegoPolicies() {
return scan.Results{}, fmt.Errorf(PoliciesNotFoundError)
}
if hasExternalPolicies {
// add externalPolicies files
err = createPolicyInputFS(memfs, policiesFolder, externalPolicies, regoExt)
if err != nil {
return nil, err
}
}
inputResource, err := json.Marshal(resource)
if err != nil {
return nil, err
}
// add input files
err = createPolicyInputFS(memfs, inputFolder, []string{string(inputResource)}, yamlExt)
if err != nil {
return nil, err
}
scanner := scannerByType(resourceKind, getScannerOptions(hasExternalPolicies, p.cac.GetUseBuiltinRegoPolicies(), policiesFolder))
scanResult, err := scanner.ScanFS(ctx, memfs, inputFolder)
if err != nil {
return nil, err
}
//special case when lib return nil for both checks and error
if scanResult == nil && err == nil {
return nil, fmt.Errorf("failed to run policy checks on resources")
}
return scanResult, nil
}
func scannerByType(resourceKind string, scannerOptions []options.ScannerOption) scanners.Scanner {
if strings.Contains(resourceKind, "Role") {
return rbac.NewScanner(scannerOptions...)
}
return kubernetes.NewScanner(scannerOptions...)
}
func getScannerOptions(hasExternalPolicies bool, useDefaultPolicies bool, policiesFolder string) []options.ScannerOption {
optionsArray := []options.ScannerOption{options.ScannerWithEmbeddedPolicies(useDefaultPolicies)}
if hasExternalPolicies {
optionsArray = append(optionsArray, options.ScannerWithPolicyDirs(policiesFolder))
}
return optionsArray
}
func createPolicyInputFS(memfs *memoryfs.FS, folderName string, fileData []string, ext string) error {
if len(fileData) == 0 {
return nil
}
if err := memfs.MkdirAll(filepath.Base(folderName), 0o700); err != nil {
return err
}
for index, file := range fileData {
if err := memfs.WriteFile(path.Join(folderName, fmt.Sprintf("file_%d.%s", index, ext)), []byte(file), 0o644); err != nil {
return err
}
}
return nil
}