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forward: Fix potential unaligned access in drop_if_recursive_routing

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ASAN error:
   forward.c:1433:13: runtime error: member access within misaligned
   address 0x51e00002f52e for type 'const struct in6_addr', which
   requires 4 byte alignment

replace IN6_ARE_ADDR_EQUAL() which uses 32bit compares on Linux - alignment
sensitive - with our own OPENVPN_IN6_ARE_ADDR_EQUAL() macro, which always
does memcpy() and does not care for alignment.

v2: Use memcmp instead of memcpy

Change-Id: I74a9eec4954f3f9d208792b6b34357571f76ae4c
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20241211171349.8892-1-gert@greenie.muc.de>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg30074.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 387c2076af14a0f1ba97b6ca0175d81d1e8391a5)
This commit is contained in:
Frank Lichtenheld 2024-12-11 18:13:48 +01:00 committed by Gert Doering
parent 6d64fa4bff
commit 62d41dec8d
2 changed files with 11 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
src/openvpn/forward.c
View File

@ -1379,8 +1379,6 @@ drop_if_recursive_routing(struct context *c, struct buffer *buf)
if (proto_ver == 4) if (proto_ver == 4)
{ {
const struct openvpn_iphdr *pip;
/* make sure we got whole IP header */ /* make sure we got whole IP header */
if (BLEN(buf) < ((int) sizeof(struct openvpn_iphdr) + ip_hdr_offset)) if (BLEN(buf) < ((int) sizeof(struct openvpn_iphdr) + ip_hdr_offset))
{ {
@ -1393,18 +1391,16 @@ drop_if_recursive_routing(struct context *c, struct buffer *buf)
return; return;
} }
pip = (struct openvpn_iphdr *) (BPTR(buf) + ip_hdr_offset); struct openvpn_iphdr *pip = (struct openvpn_iphdr *) (BPTR(buf) + ip_hdr_offset);
/* drop packets with same dest addr as gateway */ /* drop packets with same dest addr as gateway */
if (tun_sa.addr.in4.sin_addr.s_addr == pip->daddr) if (memcmp(&tun_sa.addr.in4.sin_addr.s_addr, &pip->daddr, sizeof(pip->daddr)) == 0)
{ {
drop = true; drop = true;
} }
} }
else if (proto_ver == 6) else if (proto_ver == 6)
{ {
const struct openvpn_ipv6hdr *pip6;
/* make sure we got whole IPv6 header */ /* make sure we got whole IPv6 header */
if (BLEN(buf) < ((int) sizeof(struct openvpn_ipv6hdr) + ip_hdr_offset)) if (BLEN(buf) < ((int) sizeof(struct openvpn_ipv6hdr) + ip_hdr_offset))
{ {
@ -1417,9 +1413,10 @@ drop_if_recursive_routing(struct context *c, struct buffer *buf)
return; return;
} }
struct openvpn_ipv6hdr *pip6 = (struct openvpn_ipv6hdr *) (BPTR(buf) + ip_hdr_offset);
/* drop packets with same dest addr as gateway */ /* drop packets with same dest addr as gateway */
pip6 = (struct openvpn_ipv6hdr *) (BPTR(buf) + ip_hdr_offset); if (OPENVPN_IN6_ARE_ADDR_EQUAL(&tun_sa.addr.in6.sin6_addr, &pip6->daddr))
if (IN6_ARE_ADDR_EQUAL(&tun_sa.addr.in6.sin6_addr, &pip6->daddr))
{ {
drop = true; drop = true;
} }

6
src/openvpn/proto.h
View File

@ -103,6 +103,12 @@ struct openvpn_arp {
in_addr_t ip_dest; in_addr_t ip_dest;
}; };
/** Version of IN6_ARE_ADDR_EQUAL that is guaranteed to work for
* unaligned access. E.g. Linux uses 32bit compares which are
* not safe if the struct is unaligned. */
#define OPENVPN_IN6_ARE_ADDR_EQUAL(a, b) \
(memcmp(a, b, sizeof(struct in6_addr)) == 0)
struct openvpn_iphdr { struct openvpn_iphdr {
#define OPENVPN_IPH_GET_VER(v) (((v) >> 4) & 0x0F) #define OPENVPN_IPH_GET_VER(v) (((v) >> 4) & 0x0F)
#define OPENVPN_IPH_GET_LEN(v) (((v) & 0x0F) << 2) #define OPENVPN_IPH_GET_LEN(v) (((v) & 0x0F) << 2)