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packet-epl.c: Make dissector oss-fuzz friendly 

oss-fuzz invokes the dissector without IP layer, so we can't assume
the IP address to be available when dissecting POWERLINK/UDP packets.
Same goes for the "Exported PDU" functionality.

Bug: 13756
Change-Id: I038f0445ada3f764dcc72f7bce1d02cfa49791fb
Reviewed-on: https://code.wireshark.org/review/21894
Reviewed-by: Peter Wu <peter@lekensteyn.nl>
Petri-Dish: Peter Wu <peter@lekensteyn.nl>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>
This commit is contained in:
Ahmad Fatoum 2017-06-02 11:34:55 +02:00 committed by Michael Mann
parent c5ef5c1f05
commit 197e48bcee
1 changed files with 29 additions and 12 deletions
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41
epan/dissectors/packet-epl.c
View File

@ -2149,20 +2149,26 @@ epl_get_convo(packet_info *pinfo, int opts)
struct epl_convo *convo;
conversation_t * epan_convo;
guint32 node_port;
address *node_addr;
address *node_dl_addr;
address *node_addr = &epl_placeholder_mac;
address *node_dl_addr = &epl_placeholder_mac;
if (opts & CONVO_FOR_REQUEST)
{
node_port = pinfo->destport;
node_addr = &pinfo->dst;
node_dl_addr = &pinfo->dl_dst;
if (pinfo->dst.type == AT_IPv4 || pinfo->dst.type == AT_ETHER)
node_addr = &pinfo->dst;
if (pinfo->dl_dst.type == AT_ETHER)
node_dl_addr = &pinfo->dl_dst;
}
else
{
node_port = pinfo->srcport;
node_addr = &pinfo->src;
node_dl_addr = &pinfo->dl_src;
if (pinfo->src.type == AT_IPv4 || pinfo->src.type == AT_ETHER)
node_addr = &pinfo->src;
if (pinfo->dl_src.type == AT_ETHER)
node_dl_addr = &pinfo->dl_src;
}
/* It'd be better to consult the Ethernet or IP address when matching conversations,
* but an ASnd request is targeted at a Multicast MAC address, so we'll use
@ -2504,15 +2510,26 @@ dissect_eplpdu(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, gboolean udp
pinfo->ptype = PT_NONE;
/* Get Destination */
pinfo->destport = !udpencap ? tvb_get_guint8(tvb, EPL_DEST_OFFSET)
: ((guint8*)pinfo->net_dst.data)[3];
/* Get Destination and Source */
if (udpencap)
{
/* The dissector may be invoked without an IP layer,
* so we need to check we can actually index into the buffer
*/
if (pinfo->net_dst.type == AT_IPv4)
pinfo->destport = ((guint8*)pinfo->net_dst.data)[3];
if (pinfo->net_src.type == AT_IPv4)
pinfo->srcport = ((guint8*)pinfo->net_src.data)[3];
}
else
{
pinfo->destport = tvb_get_guint8(tvb, EPL_DEST_OFFSET);
pinfo->srcport = tvb_get_guint8(tvb, EPL_SRC_OFFSET);
}
epl_segmentation.dest = pinfo->destport;
dest_str = decode_epl_address(pinfo->destport);
/* Get Source */
pinfo->srcport = !udpencap ? tvb_get_guint8(tvb, EPL_SRC_OFFSET)
: ((guint8*)pinfo->net_src.data)[3];
epl_segmentation.src = pinfo->srcport;
src_str = decode_epl_address(pinfo->srcport);