feat(rego): parse event arguments in sig

Removing default argument parsing will break rego signatures, whose
implementation depends on parsed arguments. In order to keep the option
of readability in REGO signatures, events will be parsed by default in
the context of evaluating these kind of signatures.
This will also ensure that they will not be broken depending on the
selection of parse-arguments.

Co-authored-by: Geyslan Gregório <geyslan@gmail.com>

pkg/signatures/regosig/aio.go

@@ -11,6 +11,7 @@ import (
 	"github.com/open-policy-agent/opa/compile"
 	"github.com/open-policy-agent/opa/rego"
 
+	"github.com/aquasecurity/tracee/pkg/events"
 	"github.com/aquasecurity/tracee/types/detect"
 	"github.com/aquasecurity/tracee/types/protocol"
 	"github.com/aquasecurity/tracee/types/trace"
@@ -194,6 +195,12 @@ func (a *aio) OnEvent(event protocol.Event) error {
 	if !ok {
 		return fmt.Errorf("failed to cast event's payload")
 	}
+
+	err := events.ParseArgs(&ee)
+	if err != nil {
+		return fmt.Errorf("rego aio: failed to parse event data: %v", err)
+	}
+
 	input := rego.EvalInput(ee)
 
 	ctx := context.TODO()

pkg/signatures/regosig/traceerego.go

@@ -11,8 +11,10 @@ import (
 	"github.com/open-policy-agent/opa/ast"
 	"github.com/open-policy-agent/opa/rego"
 
+	"github.com/aquasecurity/tracee/pkg/events"
 	"github.com/aquasecurity/tracee/types/detect"
 	"github.com/aquasecurity/tracee/types/protocol"
+	"github.com/aquasecurity/tracee/types/trace"
 )
 
 // RegoSignature is an abstract signature that is implemented in rego
@@ -158,7 +160,18 @@ func (sig *RegoSignature) getSelectedEvents(pkgName string) ([]detect.SignatureE
 // if bool is "returned", a true evaluation will generate a Finding with no data
 // if document is "returned", any non-empty evaluation will generate a Finding with the document as the Finding's "Data"
 func (sig *RegoSignature) OnEvent(event protocol.Event) error {
-	input := rego.EvalInput(event.Payload)
+	ee, ok := event.Payload.(trace.Event)
+
+	if !ok {
+		return fmt.Errorf("failed to cast event's payload")
+	}
+
+	err := events.ParseArgs(&ee)
+	if err != nil {
+		return fmt.Errorf("rego aio: failed to parse event data: %v", err)
+	}
+
+	input := rego.EvalInput(ee)
 	results, err := sig.matchPQ.Eval(context.TODO(), input)
 	if err != nil {
 		return fmt.Errorf("evaluating rego: %w", err)

pkg/signatures/regosig/traceerego_test.go

@@ -349,6 +349,7 @@ func OnEventSpec(t *testing.T, target string, partial bool) {
 				Payload: "just some stuff",
 			},
 			finding: nil,
+			error:   "failed to cast event's payload",
 		},
 	}