fix panic in addControlDescriptions()

* apply similar patch like in go-ldap#83, closes go-ldap#86
* add tests for adding ControlDescriptions

control_test.go

@@ -56,3 +56,42 @@ func runControlTest(t *testing.T, originalControl Control) {
 		t.Errorf("%sgot different type decoding from encoded bytes: %T vs %T", header, fromBytes, originalControl)
 	}
 }
+
+func TestDescribeControlManageDsaIT(t *testing.T) {
+	runAddControlDescriptions(t, NewControlManageDsaIT(false), "Control Type (Manage DSA IT)")
+	runAddControlDescriptions(t, NewControlManageDsaIT(true), "Control Type (Manage DSA IT)", "Criticality")
+}
+
+func TestDescribeControlPaging(t *testing.T) {
+	runAddControlDescriptions(t, NewControlPaging(100), "Control Type (Paging)", "Control Value (Paging)")
+	runAddControlDescriptions(t, NewControlPaging(0), "Control Type (Paging)", "Control Value (Paging)")
+}
+
+func TestDescribeControlString(t *testing.T) {
+	runAddControlDescriptions(t, NewControlString("x", true, "y"), "Control Type ()", "Criticality", "Control Value")
+	runAddControlDescriptions(t, NewControlString("x", true, ""), "Control Type ()", "Criticality", "Control Value")
+	runAddControlDescriptions(t, NewControlString("x", false, "y"), "Control Type ()", "Control Value")
+	runAddControlDescriptions(t, NewControlString("x", false, ""), "Control Type ()", "Control Value")
+}
+
+func runAddControlDescriptions(t *testing.T, originalControl Control, childDescriptions ...string) {
+	header := ""
+	if callerpc, _, line, ok := runtime.Caller(1); ok {
+		if caller := runtime.FuncForPC(callerpc); caller != nil {
+			header = fmt.Sprintf("%s:%d: ", caller.Name(), line)
+		}
+	}
+
+	encodedControls := encodeControls([]Control{originalControl})
+	addControlDescriptions(encodedControls)
+	encodedPacket := encodedControls.Children[0]
+	if len(encodedPacket.Children) != len(childDescriptions) {
+		t.Errorf("%sinvalid number of children: %d != %d", header, len(encodedPacket.Children), len(childDescriptions))
+	}
+	for i, desc := range childDescriptions {
+		if encodedPacket.Children[i].Description != desc {
+			t.Errorf("%sdescription not as expected: %s != %s", header, encodedPacket.Children[i].Description, desc)
+		}
+	}
+
+}

ldap.go

@@ -153,16 +153,47 @@ func addLDAPDescriptions(packet *ber.Packet) (err error) {
 func addControlDescriptions(packet *ber.Packet) {
 	packet.Description = "Controls"
 	for _, child := range packet.Children {
+		var value *ber.Packet
+		controlType := ""
 		child.Description = "Control"
-		child.Children[0].Description = "Control Type (" + ControlTypeMap[child.Children[0].Value.(string)] + ")"
-		value := child.Children[1]
-		if len(child.Children) == 3 {
+		switch len(child.Children) {
+		case 0:
+			// at least one child is required for control type
+			continue
+
+		case 1:
+			// just type, no criticality or value
+			controlType = child.Children[0].Value.(string)
+			child.Children[0].Description = "Control Type (" + ControlTypeMap[controlType] + ")"
+
+		case 2:
+			controlType = child.Children[0].Value.(string)
+			child.Children[0].Description = "Control Type (" + ControlTypeMap[controlType] + ")"
+			// Children[1] could be criticality or value (both are optional)
+			// duck-type on whether this is a boolean
+			if _, ok := child.Children[1].Value.(bool); ok {
+				child.Children[1].Description = "Criticality"
+			} else {
+				child.Children[1].Description = "Control Value"
+				value = child.Children[1]
+			}
+
+		case 3:
+			// criticality and value present
+			controlType = child.Children[0].Value.(string)
+			child.Children[0].Description = "Control Type (" + ControlTypeMap[controlType] + ")"
 			child.Children[1].Description = "Criticality"
+			child.Children[2].Description = "Control Value"
 			value = child.Children[2]
-		}
-		value.Description = "Control Value"
 
-		switch child.Children[0].Value.(string) {
+		default:
+			// more than 3 children is invalid
+			continue
+		}
+		if value == nil {
+			continue
+		}
+		switch controlType {
 		case ControlTypePaging:
 			value.Description += " (Paging)"
 			if value.Value != nil {