lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

ipv6: make fragment identifications less predictable

Browse Source 
IPv6 fragment identification generation is way beyond what we use for
IPv4 : It uses a single generator. Its not scalable and allows DOS
attacks.

Now inetpeer is IPv6 aware, we can use it to provide a more secure and
scalable frag ident generator (per destination, instead of system wide)

This patch :
1) defines a new secure_ipv6_id() helper
2) extends inet_getid() to provide 32bit results
3) extends ipv6_select_ident() with a new dest parameter

Reported-by: Fernando Gont <fernando@gont.com.ar>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2011-07-21 21:25:58 -07:00
committed by David S. Miller
parent 21efcfa0ff
commit 87c48fa3b4
7 changed files with 64 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

36
net/ipv6/ip6_output.c
View File

@@ -596,6 +596,31 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
return offset;
}
void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
{
static atomic_t ipv6_fragmentation_id;
int old, new;
if (rt) {
struct inet_peer *peer;
if (!rt->rt6i_peer)
rt6_bind_peer(rt, 1);
peer = rt->rt6i_peer;
if (peer) {
fhdr->identification = htonl(inet_getid(peer, 0));
return;
}
}
do {
old = atomic_read(&ipv6_fragmentation_id);
new = old + 1;
if (!new)
new = 1;
} while (atomic_cmpxchg(&ipv6_fragmentation_id, old, new) != old);
fhdr->identification = htonl(new);
}
int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
{
struct sk_buff *frag;
@@ -680,7 +705,7 @@ int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
skb_reset_network_header(skb);
memcpy(skb_network_header(skb), tmp_hdr, hlen);
ipv6_select_ident(fh);
ipv6_select_ident(fh, rt);
fh->nexthdr = nexthdr;
fh->reserved = 0;
fh->frag_off = htons(IP6_MF);
@@ -826,7 +851,7 @@ slow_path:
fh->nexthdr = nexthdr;
fh->reserved = 0;
if (!frag_id) {
ipv6_select_ident(fh);
ipv6_select_ident(fh, rt);
frag_id = fh->identification;
} else
fh->identification = frag_id;
@@ -1076,7 +1101,8 @@ static inline int ip6_ufo_append_data(struct sock *sk,
int getfrag(void *from, char *to, int offset, int len,
int odd, struct sk_buff *skb),
void *from, int length, int hh_len, int fragheaderlen,
int transhdrlen, int mtu,unsigned int flags)
int transhdrlen, int mtu,unsigned int flags,
struct rt6_info *rt)
{
struct sk_buff *skb;
@@ -1120,7 +1146,7 @@ static inline int ip6_ufo_append_data(struct sock *sk,
skb_shinfo(skb)->gso_size = (mtu - fragheaderlen -
sizeof(struct frag_hdr)) & ~7;
skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
ipv6_select_ident(&fhdr);
ipv6_select_ident(&fhdr, rt);
skb_shinfo(skb)->ip6_frag_id = fhdr.identification;
__skb_queue_tail(&sk->sk_write_queue, skb);
@@ -1286,7 +1312,7 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
err = ip6_ufo_append_data(sk, getfrag, from, length,
hh_len, fragheaderlen,
transhdrlen, mtu, flags);
transhdrlen, mtu, flags, rt);
if (err)
goto error;
return 0;

2
net/ipv6/udp.c
View File

@@ -1359,7 +1359,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb, u32 features)
fptr = (struct frag_hdr *)(skb_network_header(skb) + unfrag_ip6hlen);
fptr->nexthdr = nexthdr;
fptr->reserved = 0;
ipv6_select_ident(fptr);
ipv6_select_ident(fptr, (struct rt6_info *)skb_dst(skb));
/* Fragment the skb. ipv6 header and the remaining fields of the
* fragment header are updated in ipv6_gso_segment()