core: recover from panics while formatting a PDR for logging

cmd/core/display_utils.go

@@ -323,6 +323,12 @@ func displayFar(sb *strings.Builder, far *ie.IE) {
 }
 
 func displayPdr(sb *strings.Builder, pdr *ie.IE) {
+	defer func() {
+		if r := recover(); r != nil {
+			log.Warn().Msgf("recovered from panic while formatting PDR for logging: %v", r)
+		}
+	}()
+
 	pdrId, _ := pdr.PDRID()
 	fmt.Fprintf(sb, "PDR ID: %d \n", pdrId)
 

cmd/core/display_utils_test.go

@@ -0,0 +1,27 @@
+package core
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/wmnsk/go-pfcp/ie"
+)
+
+// TestDisplayPdrMalformedSdfFilter pins displayPdr against a PDI whose SDF
+// Filter claims a Flow-Description length far longer than the bytes actually
+// present. go-pfcp's SDFFilterFields.UnmarshalBinary slices past the buffer
+// in that case and panics; displayPdr is a logging path and must not take
+// the UPF down with it.
+func TestDisplayPdrMalformedSdfFilter(t *testing.T) {
+	// Flags=0x01 (FD present), spare octet, FDLength=0xFFFE, one byte of
+	// actual description.
+	malformedSdfFilter := ie.New(ie.SDFFilter, []byte{0x01, 0x00, 0xFF, 0xFE, 0x41})
+	pdi := ie.NewPDI(
+		ie.NewSourceInterface(ie.SrcInterfaceAccess),
+		malformedSdfFilter,
+	)
+	pdr := ie.NewCreatePDR(ie.NewPDRID(1), pdi)
+
+	var sb strings.Builder
+	displayPdr(&sb, pdr)
+}