[XS] Change in openvpn[master]: proto: correct 802.1Q length check in is_ipv_X

Attention is currently required from: plaisthos.

Hello plaisthos,

I'd like you to do a code review.
Please visit

    http://gerrit.openvpn.net/c/openvpn/+/1789?usp=email

to review the following change.


Change subject: proto: correct 802.1Q length check in is_ipv_X
......................................................................

proto: correct 802.1Q length check in is_ipv_X

Github: OpenVPN/openvpn#1044
Signed-off-by: rootvector2 <[email protected]>

This has also been reported twice as a security relevant bug, but
only later than the original finding - and it isn't.

While --client-nat would modify a 32bit integer "after the packet"
(the place where an IPv4 address would be, in a well-formed packet),
the underlying buffer is always max-frame sized, and we never look
at the "modified integer" afterwards, so there are no consequences
warranting allocation of a CVE ID.

Reported-By: 章鱼哥 (www.aipyaipy.com)
Reported-By: Yu Zhang Wong <[email protected]>
Change-Id: I8219c6295acf28ff10ddb2fcc285f813c42fa8fe
---
M src/openvpn/proto.c
1 file changed, 1 insertion(+), 1 deletion(-)



  git pull ssh://gerrit.openvpn.net:29418/openvpn refs/changes/89/1789/1

diff --git a/src/openvpn/proto.c b/src/openvpn/proto.c
index 13fe0a5..785c021 100644
--- a/src/openvpn/proto.c
+++ b/src/openvpn/proto.c
@@ -70,7 +70,7 @@
         if (proto == htons(OPENVPN_ETH_P_8021Q))
         {
             const struct openvpn_8021qhdr *evh;
-            if (BLENZ(buf) < sizeof(struct openvpn_ethhdr) + sizeof(struct openvpn_iphdr))
+            if (BLENZ(buf) < sizeof(struct openvpn_8021qhdr) + sizeof(struct openvpn_iphdr))
             {
                 return false;
             }

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Gerrit-MessageType: newchange
Gerrit-Project: openvpn
Gerrit-Branch: master
Gerrit-Change-Id: I8219c6295acf28ff10ddb2fcc285f813c42fa8fe
Gerrit-Change-Number: 1789
Gerrit-PatchSet: 1
Gerrit-Owner: cron2 <[email protected]>
Gerrit-Reviewer: plaisthos <[email protected]>
Gerrit-CC: openvpn-devel <[email protected]>
Gerrit-Attention: plaisthos <[email protected]>

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