provide a mechnism to exclude some CI+ SAC messages from being
exported in the clear by the export PDU mechanism use this mechanism to exclude SAC messages that contain CCK precursor data (Exporting this is not a security issue, but people should be aware of what they're doing. It's safer to exlude those messages and prevent people from exporting them accidentially.) svn path=/trunk/; revision=51037
This commit is contained in:
Martin Kaiser
parent
430bd9eacc
commit
2f42b3b031
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@ -1869,11 +1869,29 @@ dissect_conn_desc(tvbuff_t *tvb, gint offset, circuit_t *circuit,
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}
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/* dissect an item from cc_data_req/cc_data_cnf,
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returns its length or -1 for error */
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/* check if the given CC resource item may appear in the clear
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as part of an exported PDU */
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static inline gboolean
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is_cc_item_exportable(guint8 dat_id)
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{
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/* the CCK precursor value does not contain sensitive information as such
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nevertheless, it is safer to prevent people from exporting this value
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accidentially */
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if (dat_id == CC_ID_KP)
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return FALSE;
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/* we could add some more items here which do not appear in SAC messages
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normally: CC_ID_DHPH, CC_ID_DHPM */
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return TRUE;
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}
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/* dissect an item from cc_(sac_)data_req/cc_(sac_)data_cnf,
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returns its length or -1 for error
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if dat_id_ptr is not NULL, fill in the datatype id */
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static gint
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dissect_cc_item(tvbuff_t *tvb, gint offset,
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packet_info *pinfo, proto_tree *tree)
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packet_info *pinfo, proto_tree *tree, guint8 *dat_id_ptr)
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{
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proto_item *ti = NULL;
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proto_tree *cc_item_tree = NULL;
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@ -1889,6 +1907,8 @@ dissect_cc_item(tvbuff_t *tvb, gint offset,
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offset_start = offset;
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dat_id = tvb_get_guint8(tvb, offset);
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if (dat_id_ptr)
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*dat_id_ptr = dat_id;
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ti = proto_tree_add_text(tree, tvb, offset_start, -1, "CC data item: %s",
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val_to_str_const(dat_id, dvbci_cc_dat_id, "unknown"));
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@ -1972,14 +1992,27 @@ dissect_cc_item(tvbuff_t *tvb, gint offset,
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}
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/* dissect the payload of a cc message that contains data items
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if not NULL, set exportable_flag to TRUE if the message contains no
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sensitive data and can be passed to the export PDU mechanism */
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static gint
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dissect_cc_data_payload(guint32 tag, tvbuff_t *tvb, gint offset,
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packet_info *pinfo, proto_tree *tree)
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dissect_cc_data_payload(guint32 tag, tvbuff_t *tvb, gint offset,
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packet_info *pinfo, proto_tree *tree, gboolean *exportable_flag)
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{
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gint offset_start;
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guint8 i, snd_dat_nbr, req_dat_nbr;
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guint8 dat_id;
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gint item_len;
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/* we only export cc_sac_data_req and cc_sac_data_cnf
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the only meta info in the exported PDU is the data transfer
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direction, if we only ever export cc_sac_data_req and
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cc_sac_data_cnf, this info is enough to recover the apdu tag from the
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direction
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cc_sac_sync req and cc_sac_sync_cnf contain no interesting data */
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if (exportable_flag)
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*exportable_flag = (tag==T_CC_SAC_DATA_REQ || tag==T_CC_SAC_DATA_CNF);
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offset_start = offset;
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proto_tree_add_item(
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@ -1991,10 +2024,14 @@ dissect_cc_data_payload(guint32 tag, tvbuff_t *tvb, gint offset,
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offset++;
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for(i=0; i<snd_dat_nbr &&
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tvb_reported_length_remaining(tvb, offset)>0; i++) {
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item_len = dissect_cc_item(tvb, offset, pinfo, tree);
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item_len = dissect_cc_item(tvb, offset, pinfo, tree, &dat_id);
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if (item_len < 0)
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return -1;
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offset += item_len;
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if (!exportable_flag || *exportable_flag==FALSE)
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continue;
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if (!is_cc_item_exportable(dat_id))
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*exportable_flag = FALSE;
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}
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if (tag==T_CC_DATA_REQ || tag==T_CC_SAC_DATA_REQ) {
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req_dat_nbr = tvb_get_guint8(tvb, offset);
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@ -3027,6 +3064,7 @@ dissect_sac_msg(guint32 tag, tvbuff_t *tvb, gint offset,
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gint sac_payload_data_len = 0; /* just payload data */
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tvbuff_t *clear_sac_body_tvb;
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proto_tree *sac_tree = NULL;
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gboolean is_exportable = FALSE;
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offset_start = offset;
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@ -3082,7 +3120,7 @@ dissect_sac_msg(guint32 tag, tvbuff_t *tvb, gint offset,
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sac_tree = proto_item_add_subtree(ti, ett_dvbci_sac_msg_body);
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if (tag==T_CC_SAC_DATA_REQ || tag==T_CC_SAC_DATA_CNF) {
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sac_payload_data_len = dissect_cc_data_payload(tag,
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clear_sac_body_tvb, 0, pinfo, sac_tree);
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clear_sac_body_tvb, 0, pinfo, sac_tree, &is_exportable);
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}
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else if (tag==T_CC_SAC_SYNC_REQ) {
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sac_payload_data_len = 0;
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@ -3108,12 +3146,8 @@ dissect_sac_msg(guint32 tag, tvbuff_t *tvb, gint offset,
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sac_payload_len), ENC_NA);
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/* we call this function also to dissect exported SAC messages,
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dont' try to export them a second time
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we only export cc_sac_data_req and cc_sac_data_cnf,
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sync req and cnf contain no encrypted data */
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if (!exported &&
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(tag==T_CC_SAC_DATA_REQ || tag==T_CC_SAC_DATA_CNF) &&
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have_tap_listener(exported_pdu_tap)) {
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dont' try to export them a second time */
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if (!exported && is_exportable && have_tap_listener(exported_pdu_tap)) {
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tvbuff_t *clear_sac_msg_tvb;
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exp_pdu_data_t *exp_pdu_data;
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@ -3181,7 +3215,7 @@ dissect_dvbci_payload_cc(guint32 tag, gint len_field _U_,
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break;
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case T_CC_DATA_REQ:
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case T_CC_DATA_CNF:
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dissect_cc_data_payload(tag, tvb, offset, pinfo, tree);
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dissect_cc_data_payload(tag, tvb, offset, pinfo, tree, NULL);
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break;
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case T_CC_SYNC_CNF:
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status = tvb_get_guint8(tvb, offset);
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