[CWS] reduce complexity of the approver discovery

pkg/security/secl/compiler/eval/eval_test.go

@@ -531,7 +531,7 @@ func TestPartial(t *testing.T) {
 		{Expr: `process.name =~ "/usr/sbin/*" && process.uid == 0 && process.is_root`, Field: "process.uid", IsDiscarder: true},
 	}
 
-	ctx := NewContext(unsafe.Pointer(&event))
+	ctx := NewContext(event.GetPointer())
 
 	for _, test := range tests {
 		model := &testModel{}

pkg/security/secl/compiler/eval/state.go

@@ -34,6 +34,12 @@ func (s *State) UpdateFieldValues(field Field, value FieldValue) error {
 	if !ok {
 		values = []FieldValue{}
 	}
+	for _, v := range values {
+		if v == value {
+			return nil
+		}
+	}
+
 	values = append(values, value)
 	s.fieldValues[field] = values
 	return s.model.ValidateField(field, value)

pkg/security/secl/rules/approvers.go

@@ -0,0 +1,134 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016-present Datadog, Inc.
+
+package rules
+
+import (
+	"github.com/DataDog/datadog-agent/pkg/security/secl/compiler/eval"
+)
+
+// Approvers are just filter values indexed by field
+type Approvers map[eval.Field]FilterValues
+
+// isAnApprover returns whether the given value is an approver for the given rule
+func isAnApprover(event eval.Event, ctx *eval.Context, rule *Rule, field eval.Field, value interface{}) (bool, error) {
+	if err := event.SetFieldValue(field, value); err != nil {
+		return false, err
+	}
+	origResult, err := rule.PartialEval(ctx, field)
+	if err != nil {
+		return false, err
+	}
+
+	notValue, err := eval.NotOfValue(value)
+	if err != nil {
+		return false, err
+	}
+
+	if err := event.SetFieldValue(field, notValue); err != nil {
+		return false, err
+	}
+	notResult, err := rule.PartialEval(ctx, field)
+	if err != nil {
+		return false, err
+	}
+
+	if origResult && !notResult {
+		return true, nil
+	}
+
+	return false, nil
+}
+
+func bitmaskCombinations(bitmasks []int) []int {
+	if len(bitmasks) == 0 {
+		return nil
+	}
+
+	var result []int
+	for i := 0; i < (1 << len(bitmasks)); i++ {
+		var mask int
+		for j, value := range bitmasks {
+			if (i & (1 << j)) > 0 {
+				mask |= value
+			}
+		}
+		result = append(result, mask)
+	}
+
+	return result
+}
+
+// GetApprovers returns approvers for the given rules
+func GetApprovers(rules []*Rule, event eval.Event, fieldCaps FieldCapabilities) (Approvers, error) {
+	approvers := make(Approvers)
+
+	ctx := eval.NewContext(event.GetPointer())
+
+	// for each rule we should at least find one approver otherwise we will return no approver for the field
+	for _, rule := range rules {
+		var bestFilterField eval.Field
+		var bestFilterValues FilterValues
+		var bestFilterWeight int
+
+	LOOP:
+		for _, fieldCap := range fieldCaps {
+			field := fieldCap.Field
+
+			var filterValues FilterValues
+			var bitmasks []int
+
+			for _, value := range rule.GetFieldValues(field) {
+				switch value.Type {
+				case eval.ScalarValueType, eval.PatternValueType:
+					isAnApprover, err := isAnApprover(event, ctx, rule, field, value.Value)
+					if err != nil {
+						return nil, err
+					}
+
+					if isAnApprover {
+						filterValues = filterValues.Merge(FilterValue{Field: field, Value: value.Value, Type: value.Type})
+					} else if fieldCap.Types&eval.BitmaskValueType == 0 {
+						// if not a bitmask we need to have all the value as approvers
+						// basically a list of values ex: in ["test123", "test456"]
+						continue LOOP
+					}
+				case eval.BitmaskValueType:
+					bitmasks = append(bitmasks, value.Value.(int))
+				}
+			}
+
+			for _, bitmask := range bitmaskCombinations(bitmasks) {
+				isAnApprover, err := isAnApprover(event, ctx, rule, field, bitmask)
+				if err != nil {
+					return nil, err
+				}
+
+				if isAnApprover {
+					filterValues = filterValues.Merge(FilterValue{Field: field, Value: bitmask, Type: eval.BitmaskValueType})
+				}
+			}
+
+			if len(filterValues) == 0 || !fieldCaps.Validate(filterValues) {
+				continue
+			}
+
+			if bestFilterValues == nil || fieldCap.FilterWeight > bestFilterWeight {
+				bestFilterField = field
+				bestFilterValues = filterValues
+				bestFilterWeight = fieldCap.FilterWeight
+			}
+		}
+
+		// no filter value for a rule thus no approver for the event type
+		if bestFilterValues == nil {
+			return nil, nil
+		}
+
+		approvers[bestFilterField] = append(approvers[bestFilterField], bestFilterValues...)
+	}
+
+	return approvers, nil
+}

pkg/security/secl/rules/bucket.go

@@ -13,9 +13,6 @@ import (
 	"github.com/DataDog/datadog-agent/pkg/security/secl/compiler/eval"
 )
 
-// Approvers are just filter values indexed by field
-type Approvers map[eval.Field]FilterValues
-
 // RuleBucket groups rules with the same event type
 type RuleBucket struct {
 	rules  []*Rule
@@ -48,83 +45,3 @@ func (rb *RuleBucket) AddRule(rule *Rule) error {
 func (rb *RuleBucket) GetRules() []*Rule {
 	return rb.rules
 }
-
-// FieldCombinations - array all the combinations of field
-type FieldCombinations [][]eval.Field
-
-func (a FieldCombinations) Len() int           { return len(a) }
-func (a FieldCombinations) Swap(i, j int)      { a[i], a[j] = a[j], a[i] }
-func (a FieldCombinations) Less(i, j int) bool { return len(a[i]) < len(a[j]) }
-
-func fieldCombinations(fields []eval.Field) FieldCombinations {
-	var result FieldCombinations
-
-	for i := 1; i < (1 << len(fields)); i++ {
-		var subResult []eval.Field
-		for j, field := range fields {
-			if (i & (1 << j)) > 0 {
-				subResult = append(subResult, field)
-			}
-		}
-		result = append(result, subResult)
-	}
-
-	// order the list with the single field first
-	sort.Sort(result)
-
-	return result
-}
-
-func getFilterValuesWeight(filterValues FilterValues, fieldCaps FieldCapabilities) int {
-	var maxWeight int
-	for _, filterValue := range filterValues {
-		for _, fc := range fieldCaps {
-			if filterValue.Field == fc.Field && fc.FilterWeight > maxWeight {
-				maxWeight = fc.FilterWeight
-			}
-		}
-	}
-	return maxWeight
-}
-
-// GetApprovers returns the approvers for an event
-func (rb *RuleBucket) GetApprovers(event eval.Event, fieldCaps FieldCapabilities) (Approvers, error) {
-	fcs := fieldCombinations(fieldCaps.GetFields())
-
-	approvers := make(Approvers)
-	for _, rule := range rb.rules {
-		truthTable, err := newTruthTable(rule.Rule, event)
-		if err != nil {
-			return nil, err
-		}
-
-		var filterValues FilterValues
-		var maxWeight int
-
-		for _, fields := range fcs {
-			candidates := truthTable.getApprovers(fields...)
-
-			// only one combination of the approvers is required, keep the best one meaning
-			// the one with the highest weight
-			if len(candidates) > 0 && fieldCaps.Validate(candidates) {
-				// as fieldCombinations return all the combinations in the less fields order
-				// we keep the highest weight with a minimal set of fields.
-				if weight := getFilterValuesWeight(candidates, fieldCaps); filterValues == nil || weight > maxWeight {
-					filterValues = candidates
-					maxWeight = weight
-				}
-			}
-		}
-
-		if len(filterValues) == 0 {
-			return nil, &ErrNoApprover{Fields: fieldCaps.GetFields()}
-		}
-
-		// dispatch per field
-		for _, filterValue := range filterValues {
-			approvers[filterValue.Field] = approvers[filterValue.Field].Merge(filterValue)
-		}
-	}
-
-	return approvers, nil
-}

pkg/security/secl/rules/filter_values.go

@@ -16,20 +16,14 @@ type FilterValue struct {
 	Field eval.Field
 	Value interface{}
 	Type  eval.FieldValueType
-
-	// indicate process.uid == process.gid for example
-	isScalar bool
-	// opposite value of the field Value
-	notValue interface{}
-	not      bool
 }
 
 // Merge merges to FilterValues ensuring there is no duplicate value
 func (fv FilterValues) Merge(n ...FilterValue) FilterValues {
 LOOP:
 	for _, v1 := range n {
 		for _, v2 := range fv {
-			if v1.Field == v2.Field && v1.Value == v2.Value && v1.not == v2.not {
+			if v1.Field == v2.Field && v1.Value == v2.Value {
 				continue LOOP
 			}
 		}

pkg/security/secl/rules/ruleset.go

@@ -396,7 +396,7 @@ func (rs *RuleSet) GetApprovers(fieldCaps map[eval.EventType]FieldCapabilities)
 		}
 
 		eventApprovers, err := rs.GetEventApprovers(eventType, caps)
-		if err != nil {
+		if err != nil || len(eventApprovers) == 0 {
 			continue
 		}
 		approvers[eventType] = eventApprovers
@@ -412,7 +412,7 @@ func (rs *RuleSet) GetEventApprovers(eventType eval.EventType, fieldCaps FieldCa
 		return nil, ErrNoEventTypeBucket{EventType: eventType}
 	}
 
-	return bucket.GetApprovers(rs.eventCtor(), fieldCaps)
+	return GetApprovers(bucket.rules, rs.eventCtor(), fieldCaps)
 }
 
 // GetFieldValues returns all the values of the given field