gsm-a, nas-eps: enhance handling of missing mandatory i.e.

When a mandatory information element is missing, try to report an expert info,
instead of throwing a fatal malformed exception (or of reporting nothing at all).

According to TS 24.007 11.2.3, a mandatory i.e. may be part of the imperative part
of the message, so that expert info should be at PI_ERROR level

Change-Id: Id399c236f2923db36540bbda0d29d666548f7cbd
Reviewed-on: https://code.wireshark.org/review/22134
Reviewed-by: Pascal Quantin <pascal.quantin@gmail.com>
Petri-Dish: Pascal Quantin <pascal.quantin@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>

1 files changed, 17 insertions, 15 deletions

diff --git a/epan/dissectors/packet-gsm_a_rp.c b/epan/dissectors/packet-gsm_a_rp.c
index dd9071be25..96c78a8af1 100644
--- a/epan/dissectors/packet-gsm_a_rp.c
+++ b/epan/dissectors/packet-gsm_a_rp.c
@@ -93,6 +93,7 @@ static int hf_gsm_a_rp_rp_message_reference = -1;
 static gint ett_rp_msg = -1;
 
 static expert_field ei_gsm_a_rp_extraneous_data = EI_INIT;
+static expert_field ei_gsm_a_rp_missing_mandatory_element = EI_INIT;
 
 static dissector_handle_t gsm_sms_handle;	/* SMS TPDU */
 
@@ -256,13 +257,13 @@ rp_data_n_ms(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offset
 
 	pinfo->p2p_dir = P2P_DIR_SENT;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_ORIG_ADDR, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_ORIG_ADDR, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_DEST_ADDR, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_DEST_ADDR, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	EXTRANEOUS_DATA_CHECK(curr_len, 0, pinfo, &ei_gsm_a_rp_extraneous_data);
 }
@@ -282,13 +283,13 @@ rp_data_ms_n(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offset
 
 	pinfo->p2p_dir = P2P_DIR_RECV;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_ORIG_ADDR, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_ORIG_ADDR, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_DEST_ADDR, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_DEST_ADDR, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	EXTRANEOUS_DATA_CHECK(curr_len, 0, pinfo, &ei_gsm_a_rp_extraneous_data);
 }
@@ -306,7 +307,7 @@ rp_smma(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo _U_, guint32 offset,
 	curr_offset = offset;
 	curr_len = len;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	EXTRANEOUS_DATA_CHECK(curr_len, 0, pinfo, &ei_gsm_a_rp_extraneous_data);
 }
@@ -326,7 +327,7 @@ rp_ack_n_ms(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offset,
 
 	pinfo->p2p_dir = P2P_DIR_SENT;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	ELEM_OPT_TLV(0x41, GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL);
 
@@ -348,7 +349,7 @@ rp_ack_ms_n(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offset,
 
 	pinfo->p2p_dir = P2P_DIR_RECV;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	ELEM_OPT_TLV(0x41, GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL);
 
@@ -370,9 +371,9 @@ rp_error_n_ms(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offse
 
 	pinfo->p2p_dir = P2P_DIR_SENT;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_CAUSE, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_CAUSE, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	ELEM_OPT_TLV(0x41, GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL);
 
@@ -394,9 +395,9 @@ rp_error_ms_n(tvbuff_t *tvb, proto_tree *tree, packet_info *pinfo, guint32 offse
 
 	pinfo->p2p_dir = P2P_DIR_RECV;
 
-	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL);
+	ELEM_MAND_V(GSM_A_PDU_TYPE_RP, DE_RP_MESSAGE_REF, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
-	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_CAUSE, NULL);
+	ELEM_MAND_LV(GSM_A_PDU_TYPE_RP, DE_RP_CAUSE, NULL, ei_gsm_a_rp_missing_mandatory_element);
 
 	ELEM_OPT_TLV(0x41, GSM_A_PDU_TYPE_RP, DE_RP_USER_DATA, NULL);
 
@@ -525,6 +526,7 @@ proto_register_gsm_a_rp(void)
 
 	static ei_register_info ei[] = {
 		{ &ei_gsm_a_rp_extraneous_data, { "gsm_a.rp.extraneous_data", PI_PROTOCOL, PI_NOTE, "Extraneous Data, dissector bug or later version spec(report to wireshark.org)", EXPFILL }},
+		{ &ei_gsm_a_rp_missing_mandatory_element, { "gsm_a.rp.missing_mandatory_element", PI_PROTOCOL, PI_ERROR, "Missing Mandatory element, rest of dissection is suspect", EXPFILL }},
 	};
 
 	expert_module_t* expert_gsm_a_rp;