strict decode policy first

staging/src/k8s.io/apiserver/pkg/audit/policy/reader.go

@@ -20,12 +20,13 @@ import (
 	"fmt"
 	"io/ioutil"
 
+	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apimachinery/pkg/runtime/serializer"
 	auditinternal "k8s.io/apiserver/pkg/apis/audit"
 	auditv1 "k8s.io/apiserver/pkg/apis/audit/v1"
 	"k8s.io/apiserver/pkg/apis/audit/validation"
 	"k8s.io/apiserver/pkg/audit"
-
 	"k8s.io/klog/v2"
 )
 
@@ -61,11 +62,23 @@ func LoadPolicyFromFile(filePath string) (*auditinternal.Policy, error) {
 
 func LoadPolicyFromBytes(policyDef []byte) (*auditinternal.Policy, error) {
 	policy := &auditinternal.Policy{}
-	decoder := audit.Codecs.UniversalDecoder(apiGroupVersions...)
+	strictDecoder := serializer.NewCodecFactory(audit.Scheme, serializer.EnableStrict).UniversalDecoder()
 
-	_, gvk, err := decoder.Decode(policyDef, nil, policy)
+	// Try strict decoding first.
+	_, gvk, err := strictDecoder.Decode(policyDef, nil, policy)
 	if err != nil {
-		return nil, fmt.Errorf("failed decoding: %v", err)
+		if !runtime.IsStrictDecodingError(err) {
+			return nil, fmt.Errorf("failed decoding: %w", err)
+		}
+		var (
+			lenientDecoder = audit.Codecs.UniversalDecoder(apiGroupVersions...)
+			lenientErr     error
+		)
+		_, gvk, lenientErr = lenientDecoder.Decode(policyDef, nil, policy)
+		if lenientErr != nil {
+			return nil, fmt.Errorf("failed lenient decoding: %w", lenientErr)
+		}
+		klog.Warningf("Audit policy contains errors, falling back to lenient decoding: %v", err)
 	}
 
 	// Ensure the policy file contained an apiVersion and kind.

staging/src/k8s.io/apiserver/pkg/audit/policy/reader_test.go

@@ -25,6 +25,7 @@ import (
 
 	"k8s.io/apimachinery/pkg/util/diff"
 	"k8s.io/apiserver/pkg/apis/audit"
+
 	// import to call webhook's init() function to register audit.Policy to schema
 	_ "k8s.io/apiserver/plugin/pkg/audit/webhook"
 
@@ -70,6 +71,18 @@ rules:
   - level: Metadata
 `
 
+const policyWithUnknownField = `
+apiVersion: audit.k8s.io/v1
+kind: Policy
+rules:
+- level: None
+  resources:
+  - group: coordination.k8s.io
+    resources:
+    - "leases"
+    verbs: ["watch", "get", "list"] # invalid indentation on verbs
+`
+
 var expectedPolicy = &audit.Policy{
 	Rules: []audit.PolicyRule{{
 		Level:           audit.LevelNone,
@@ -113,6 +126,15 @@ func TestParsePolicyWithNoVersionOrKind(t *testing.T) {
 	assert.Contains(t, err.Error(), "unknown group version field")
 }
 
+func TestParsePolicyWithUnknownField(t *testing.T) {
+	f, err := writePolicy(t, policyWithUnknownField)
+	require.NoError(t, err)
+	defer os.Remove(f)
+
+	_, err = LoadPolicyFromFile(f)
+	require.NoError(t, err)
+}
+
 func TestPolicyCntCheck(t *testing.T) {
 	var testCases = []struct {
 		caseName, policy string