blob: f096553d4c2b28545f296faaec8780a1bc065db9 (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
|
commit fc61d1bda112ffc669dbde961fab19f60b3c7439
Author: Gert Doering <gert@greenie.muc.de>
Date: Tue Jun 13 22:08:32 2017 +0200
Fix remotely-triggerable ASSERT() on malformed IPv6 packet.
Correct sanity checks on IPv6 packet length in mss_fixup_ipv6(),
and change the ASSERT() check in mss_fixup_dowork() into a simple
"return" (= the TCP header will simply not be inspected further).
CVE-2017-7508 has been assigned due to the serious nature of the
bug: it can be used to remotely shutdown an openvpn server or
client, if IPv6 and --mssfix are enabled and the IPv6 networks used
inside the VPN are known.
Found by Guido Vranken <guidovranken@gmail.com>.
v2: style changes
CVE: 2017-7508
Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <20170613200832.15027-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/search?l=mid&q=20170613200832.15027-1-gert@greenie.muc.de
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit c3f47077a7756de5929094569421a95aa66f2022)
diff --git a/src/openvpn/mss.c b/src/openvpn/mss.c
index f930942a..c91751d1 100644
--- a/src/openvpn/mss.c
+++ b/src/openvpn/mss.c
@@ -110,8 +110,12 @@ mss_fixup_ipv6 (struct buffer *buf, int maxmss)
if ( pip6->nexthdr != OPENVPN_IPPROTO_TCP )
return;
+ /* skip IPv6 header (40 bytes),
+ * verify remainder is large enough to contain a full TCP header
+ */
newbuf = *buf;
- if ( buf_advance( &newbuf, 40 ) )
+ if (buf_advance( &newbuf, 40 )
+ && BLEN(&newbuf) >= (int) sizeof(struct openvpn_tcphdr))
{
struct openvpn_tcphdr *tc = (struct openvpn_tcphdr *) BPTR (&newbuf);
if (tc->flags & OPENVPN_TCPH_SYN_MASK)
@@ -133,7 +137,10 @@ mss_fixup_dowork (struct buffer *buf, uint16_t maxmss)
int accumulate;
struct openvpn_tcphdr *tc;
- ASSERT (BLEN (buf) >= (int) sizeof (struct openvpn_tcphdr));
+ if (BLEN(buf) < (int) sizeof(struct openvpn_tcphdr))
+ {
+ return;
+ }
verify_align_4 (buf);
tc = (struct openvpn_tcphdr *) BPTR (buf);
|
