mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 08:19:28 +00:00
![Herbert Xu](/assets/img/avatar_default.png)
This is an old bugbear of mine:
https://www.mail-archive.com/netdev@vger.kernel.org/msg03894.html
By crafting special packets, it is possible to cause recursion
in our kernel when processing transport-mode packets at levels
that are only limited by packet size.
The easiest one is with DNAT, but an even worse one is where
UDP encapsulation is used in which case you just have to insert
an UDP encapsulation header in between each level of recursion.
This patch avoids this problem by reinjecting tranport-mode packets
through a tasklet.
Fixes: b05e106698
("[IPV4/6]: Netfilter IPsec input hooks")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
176 lines
4.3 KiB
C
176 lines
4.3 KiB
C
// SPDX-License-Identifier: GPL-2.0
|
|
/*
|
|
* xfrm4_input.c
|
|
*
|
|
* Changes:
|
|
* YOSHIFUJI Hideaki @USAGI
|
|
* Split up af-specific portion
|
|
* Derek Atkins <derek@ihtfp.com>
|
|
* Add Encapsulation support
|
|
*
|
|
*/
|
|
|
|
#include <linux/slab.h>
|
|
#include <linux/module.h>
|
|
#include <linux/string.h>
|
|
#include <linux/netfilter.h>
|
|
#include <linux/netfilter_ipv4.h>
|
|
#include <net/ip.h>
|
|
#include <net/xfrm.h>
|
|
|
|
int xfrm4_extract_input(struct xfrm_state *x, struct sk_buff *skb)
|
|
{
|
|
return xfrm4_extract_header(skb);
|
|
}
|
|
|
|
static int xfrm4_rcv_encap_finish2(struct net *net, struct sock *sk,
|
|
struct sk_buff *skb)
|
|
{
|
|
return dst_input(skb);
|
|
}
|
|
|
|
static inline int xfrm4_rcv_encap_finish(struct net *net, struct sock *sk,
|
|
struct sk_buff *skb)
|
|
{
|
|
if (!skb_dst(skb)) {
|
|
const struct iphdr *iph = ip_hdr(skb);
|
|
|
|
if (ip_route_input_noref(skb, iph->daddr, iph->saddr,
|
|
iph->tos, skb->dev))
|
|
goto drop;
|
|
}
|
|
|
|
if (xfrm_trans_queue(skb, xfrm4_rcv_encap_finish2))
|
|
goto drop;
|
|
|
|
return 0;
|
|
drop:
|
|
kfree_skb(skb);
|
|
return NET_RX_DROP;
|
|
}
|
|
|
|
int xfrm4_transport_finish(struct sk_buff *skb, int async)
|
|
{
|
|
struct xfrm_offload *xo = xfrm_offload(skb);
|
|
struct iphdr *iph = ip_hdr(skb);
|
|
|
|
iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
|
|
|
|
#ifndef CONFIG_NETFILTER
|
|
if (!async)
|
|
return -iph->protocol;
|
|
#endif
|
|
|
|
__skb_push(skb, skb->data - skb_network_header(skb));
|
|
iph->tot_len = htons(skb->len);
|
|
ip_send_check(iph);
|
|
|
|
if (xo && (xo->flags & XFRM_GRO)) {
|
|
skb_mac_header_rebuild(skb);
|
|
return 0;
|
|
}
|
|
|
|
NF_HOOK(NFPROTO_IPV4, NF_INET_PRE_ROUTING,
|
|
dev_net(skb->dev), NULL, skb, skb->dev, NULL,
|
|
xfrm4_rcv_encap_finish);
|
|
return 0;
|
|
}
|
|
|
|
/* If it's a keepalive packet, then just eat it.
|
|
* If it's an encapsulated packet, then pass it to the
|
|
* IPsec xfrm input.
|
|
* Returns 0 if skb passed to xfrm or was dropped.
|
|
* Returns >0 if skb should be passed to UDP.
|
|
* Returns <0 if skb should be resubmitted (-ret is protocol)
|
|
*/
|
|
int xfrm4_udp_encap_rcv(struct sock *sk, struct sk_buff *skb)
|
|
{
|
|
struct udp_sock *up = udp_sk(sk);
|
|
struct udphdr *uh;
|
|
struct iphdr *iph;
|
|
int iphlen, len;
|
|
|
|
__u8 *udpdata;
|
|
__be32 *udpdata32;
|
|
__u16 encap_type = up->encap_type;
|
|
|
|
/* if this is not encapsulated socket, then just return now */
|
|
if (!encap_type)
|
|
return 1;
|
|
|
|
/* If this is a paged skb, make sure we pull up
|
|
* whatever data we need to look at. */
|
|
len = skb->len - sizeof(struct udphdr);
|
|
if (!pskb_may_pull(skb, sizeof(struct udphdr) + min(len, 8)))
|
|
return 1;
|
|
|
|
/* Now we can get the pointers */
|
|
uh = udp_hdr(skb);
|
|
udpdata = (__u8 *)uh + sizeof(struct udphdr);
|
|
udpdata32 = (__be32 *)udpdata;
|
|
|
|
switch (encap_type) {
|
|
default:
|
|
case UDP_ENCAP_ESPINUDP:
|
|
/* Check if this is a keepalive packet. If so, eat it. */
|
|
if (len == 1 && udpdata[0] == 0xff) {
|
|
goto drop;
|
|
} else if (len > sizeof(struct ip_esp_hdr) && udpdata32[0] != 0) {
|
|
/* ESP Packet without Non-ESP header */
|
|
len = sizeof(struct udphdr);
|
|
} else
|
|
/* Must be an IKE packet.. pass it through */
|
|
return 1;
|
|
break;
|
|
case UDP_ENCAP_ESPINUDP_NON_IKE:
|
|
/* Check if this is a keepalive packet. If so, eat it. */
|
|
if (len == 1 && udpdata[0] == 0xff) {
|
|
goto drop;
|
|
} else if (len > 2 * sizeof(u32) + sizeof(struct ip_esp_hdr) &&
|
|
udpdata32[0] == 0 && udpdata32[1] == 0) {
|
|
|
|
/* ESP Packet with Non-IKE marker */
|
|
len = sizeof(struct udphdr) + 2 * sizeof(u32);
|
|
} else
|
|
/* Must be an IKE packet.. pass it through */
|
|
return 1;
|
|
break;
|
|
}
|
|
|
|
/* At this point we are sure that this is an ESPinUDP packet,
|
|
* so we need to remove 'len' bytes from the packet (the UDP
|
|
* header and optional ESP marker bytes) and then modify the
|
|
* protocol to ESP, and then call into the transform receiver.
|
|
*/
|
|
if (skb_unclone(skb, GFP_ATOMIC))
|
|
goto drop;
|
|
|
|
/* Now we can update and verify the packet length... */
|
|
iph = ip_hdr(skb);
|
|
iphlen = iph->ihl << 2;
|
|
iph->tot_len = htons(ntohs(iph->tot_len) - len);
|
|
if (skb->len < iphlen + len) {
|
|
/* packet is too small!?! */
|
|
goto drop;
|
|
}
|
|
|
|
/* pull the data buffer up to the ESP header and set the
|
|
* transport header to point to ESP. Keep UDP on the stack
|
|
* for later.
|
|
*/
|
|
__skb_pull(skb, len);
|
|
skb_reset_transport_header(skb);
|
|
|
|
/* process ESP */
|
|
return xfrm4_rcv_encap(skb, IPPROTO_ESP, 0, encap_type);
|
|
|
|
drop:
|
|
kfree_skb(skb);
|
|
return 0;
|
|
}
|
|
|
|
int xfrm4_rcv(struct sk_buff *skb)
|
|
{
|
|
return xfrm4_rcv_spi(skb, ip_hdr(skb)->protocol, 0);
|
|
}
|
|
EXPORT_SYMBOL(xfrm4_rcv);
|