fix(authz): keep shared policy values immutable

service/internal/access/v2/pdp.go

@@ -16,6 +16,7 @@ import (
 	attrs "github.com/opentdf/platform/protocol/go/policy/attributes"
 	"github.com/opentdf/platform/service/internal/subjectmappingbuiltin"
 	"github.com/opentdf/platform/service/logger"
+	"google.golang.org/protobuf/proto"
 )
 
 // Decision represents the overall access decision for an entity.
@@ -140,7 +141,7 @@ func NewPolicyDecisionPoint(
 		// Not every value may have a subject mapping and be entitleable, but a lookup must still be possible
 		for _, value := range attr.GetValues() {
 			mapped := &attrs.GetAttributeValuesByFqnsResponse_AttributeAndValue{
-				Value:     value,
+				Value:     proto.CloneOf(value),
 				Attribute: attr,
 			}
 			allEntitleableAttributesByValueFQN[value.GetFqn()] = mapped
@@ -181,6 +182,7 @@ func NewPolicyDecisionPoint(
 		if err != nil {
 			return nil, fmt.Errorf("failed to get attribute definition: %w", err)
 		}
+		mappedValue = proto.CloneOf(mappedValue)
 		mappedValue.SubjectMappings = []*policy.SubjectMapping{sm}
 		mapped := &attrs.GetAttributeValuesByFqnsResponse_AttributeAndValue{
 			Value:     mappedValue,

service/internal/access/v2/pdp_immutable_test.go

@@ -0,0 +1,52 @@
+package access
+
+import (
+	"log/slog"
+	"sync"
+	"testing"
+
+	"github.com/opentdf/platform/protocol/go/policy"
+	"github.com/opentdf/platform/service/logger"
+	"github.com/stretchr/testify/require"
+	"google.golang.org/protobuf/proto"
+)
+
+func TestPolicyConstructionDoesNotMutateSharedValues(t *testing.T) {
+	const definitionFQN = "https://scale.example/attr/department"
+	value := &policy.Value{Fqn: definitionFQN + "/value/engineering"}
+	attr := &policy.Attribute{Fqn: definitionFQN, Rule: policy.AttributeRuleTypeEnum_ATTRIBUTE_RULE_TYPE_ENUM_ANY_OF, Values: []*policy.Value{value}}
+	// The second mapping exercises values absent from the definition's value list.
+	mappings := []*policy.SubjectMapping{
+		{Id: "existing", AttributeValue: value, Actions: []*policy.Action{{Name: "read"}}},
+		{Id: "additional", AttributeValue: &policy.Value{Fqn: definitionFQN + "/value/sales"}, Actions: []*policy.Action{{Name: "read"}}},
+	}
+	originalAttribute := proto.CloneOf(attr)
+	originalMapping := proto.CloneOf(mappings[1])
+	log := &logger.Logger{Logger: slog.New(slog.DiscardHandler)}
+	ctx := t.Context()
+	const constructions = 16
+	results := make(chan *PolicyDecisionPoint, constructions)
+	errors := make(chan error, constructions)
+	var workers sync.WaitGroup
+	for range constructions {
+		workers.Go(func() {
+			pdp, err := NewPolicyDecisionPoint(ctx, log, []*policy.Attribute{attr}, mappings, nil, true, false)
+			results <- pdp
+			errors <- err
+		})
+	}
+	workers.Wait()
+	close(results)
+	close(errors)
+	for err := range errors {
+		require.NoError(t, err)
+	}
+	for pdp := range results {
+		for _, mapping := range mappings {
+			got := pdp.allEntitleableAttributesByValueFQN[mapping.GetAttributeValue().GetFqn()]
+			require.Len(t, got.GetValue().GetSubjectMappings(), 1)
+		}
+	}
+	require.True(t, proto.Equal(originalAttribute, attr))
+	require.True(t, proto.Equal(originalMapping, mappings[1]))
+}