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Subject[patch 11/69] NETFILTER: {ip,nf}_nat_proto_gre: do not modify/corrupt GREv0 packets through NAT
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Jorge Boncompte <jorge@dti2.net>

While porting some changes of the 2.6.21-rc7 pptp/proto_gre conntrack
and nat modules to a 2.4.32 kernel I noticed that the gre_key function
returns a wrong pointer to the GRE key of a version 0 packet thus
corrupting the packet payload.

The intended behaviour for GREv0 packets is to act like
nf_conntrack_proto_generic/nf_nat_proto_unknown so I have ripped the
offending functions (not used anymore) and modified the
nf_nat_proto_gre modules to not touch version 0 (non PPTP) packets.

Signed-off-by: Jorge Boncompte <jorge@dti2.net>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>

---
commit 244c67aee5750eb3a79c727d09c01a500e68bbbe
tree 29bbce944bba681886a6d58c0c6b7bca3858c0e1
parent 8d8b10482fffcb72b15515231bb942e2ad6395c9
author Jorge Boncompte <jorge@dti2.net> Thu, 03 May 2007 02:50:51 +0200
committer Patrick McHardy <kaber@trash.net> Thu, 03 May 2007 02:50:51 +0200

include/linux/netfilter/nf_conntrack_proto_gre.h | 18 ----------------
include/linux/netfilter_ipv4/ip_conntrack_proto_gre.h | 19 -----------------
net/ipv4/netfilter/ip_nat_proto_gre.c | 20 +++++++-----------
net/ipv4/netfilter/nf_nat_proto_gre.c | 20 +++++++-----------
4 files changed, 16 insertions(+), 61 deletions(-)

--- linux-2.6.21.1.orig/include/linux/netfilter/nf_conntrack_proto_gre.h
+++ linux-2.6.21.1/include/linux/netfilter/nf_conntrack_proto_gre.h
@@ -87,24 +87,6 @@ int nf_ct_gre_keymap_add(struct nf_conn
/* delete keymap entries */
void nf_ct_gre_keymap_destroy(struct nf_conn *ct);

-/* get pointer to gre key, if present */
-static inline __be32 *gre_key(struct gre_hdr *greh)
-{
- if (!greh->key)
- return NULL;
- if (greh->csum || greh->routing)
- return (__be32 *)(greh+sizeof(*greh)+4);
- return (__be32 *)(greh+sizeof(*greh));
-}
-
-/* get pointer ot gre csum, if present */
-static inline __sum16 *gre_csum(struct gre_hdr *greh)
-{
- if (!greh->csum)
- return NULL;
- return (__sum16 *)(greh+sizeof(*greh));
-}
-
extern void nf_ct_gre_keymap_flush(void);
extern void nf_nat_need_gre(void);

--- linux-2.6.21.1.orig/include/linux/netfilter_ipv4/ip_conntrack_proto_gre.h
+++ linux-2.6.21.1/include/linux/netfilter_ipv4/ip_conntrack_proto_gre.h
@@ -90,25 +90,6 @@ int ip_ct_gre_keymap_add(struct ip_connt
/* delete keymap entries */
void ip_ct_gre_keymap_destroy(struct ip_conntrack *ct);

-
-/* get pointer to gre key, if present */
-static inline __be32 *gre_key(struct gre_hdr *greh)
-{
- if (!greh->key)
- return NULL;
- if (greh->csum || greh->routing)
- return (__be32 *) (greh+sizeof(*greh)+4);
- return (__be32 *) (greh+sizeof(*greh));
-}
-
-/* get pointer ot gre csum, if present */
-static inline __sum16 *gre_csum(struct gre_hdr *greh)
-{
- if (!greh->csum)
- return NULL;
- return (__sum16 *) (greh+sizeof(*greh));
-}
-
#endif /* __KERNEL__ */

#endif /* _CONNTRACK_PROTO_GRE_H */
--- linux-2.6.21.1.orig/net/ipv4/netfilter/ip_nat_proto_gre.c
+++ linux-2.6.21.1/net/ipv4/netfilter/ip_nat_proto_gre.c
@@ -70,6 +70,11 @@ gre_unique_tuple(struct ip_conntrack_tup
__be16 *keyptr;
unsigned int min, i, range_size;

+ /* If there is no master conntrack we are not PPTP,
+ do not change tuples */
+ if (!conntrack->master)
+ return 0;
+
if (maniptype == IP_NAT_MANIP_SRC)
keyptr = &tuple->src.u.gre.key;
else
@@ -122,18 +127,9 @@ gre_manip_pkt(struct sk_buff **pskb,
if (maniptype == IP_NAT_MANIP_DST) {
/* key manipulation is always dest */
switch (greh->version) {
- case 0:
- if (!greh->key) {
- DEBUGP("can't nat GRE w/o key\n");
- break;
- }
- if (greh->csum) {
- /* FIXME: Never tested this code... */
- nf_proto_csum_replace4(gre_csum(greh), *pskb,
- *(gre_key(greh)),
- tuple->dst.u.gre.key, 0);
- }
- *(gre_key(greh)) = tuple->dst.u.gre.key;
+ case GRE_VERSION_1701:
+ /* We do not currently NAT any GREv0 packets.
+ * Try to behave like "ip_nat_proto_unknown" */
break;
case GRE_VERSION_PPTP:
DEBUGP("call_id -> 0x%04x\n",
--- linux-2.6.21.1.orig/net/ipv4/netfilter/nf_nat_proto_gre.c
+++ linux-2.6.21.1/net/ipv4/netfilter/nf_nat_proto_gre.c
@@ -72,6 +72,11 @@ gre_unique_tuple(struct nf_conntrack_tup
__be16 *keyptr;
unsigned int min, i, range_size;

+ /* If there is no master conntrack we are not PPTP,
+ do not change tuples */
+ if (!conntrack->master)
+ return 0;
+
if (maniptype == IP_NAT_MANIP_SRC)
keyptr = &tuple->src.u.gre.key;
else
@@ -122,18 +127,9 @@ gre_manip_pkt(struct sk_buff **pskb, uns
if (maniptype != IP_NAT_MANIP_DST)
return 1;
switch (greh->version) {
- case 0:
- if (!greh->key) {
- DEBUGP("can't nat GRE w/o key\n");
- break;
- }
- if (greh->csum) {
- /* FIXME: Never tested this code... */
- nf_proto_csum_replace4(gre_csum(greh), *pskb,
- *(gre_key(greh)),
- tuple->dst.u.gre.key, 0);
- }
- *(gre_key(greh)) = tuple->dst.u.gre.key;
+ case GRE_VERSION_1701:
+ /* We do not currently NAT any GREv0 packets.
+ * Try to behave like "nf_nat_proto_unknown" */
break;
case GRE_VERSION_PPTP:
DEBUGP("call_id -> 0x%04x\n", ntohs(tuple->dst.u.gre.key));
--
-
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