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authorEric Dumazet <eric.dumazet@gmail.com>2011-08-09 10:44:00 +0400
committerGreg Kroah-Hartman <gregkh@suse.de>2011-08-16 05:31:37 +0400
commitef81bb40bf15f350fe865f31fa42f1082772a576 (patch)
treef89c3e9616127d234207a84e108bf147cc393215 /net
parenteb473dd5ad8785d35142966cdcd6896d8dff5a22 (diff)
downloadlinux-ef81bb40bf15f350fe865f31fa42f1082772a576.tar.xz
ipv6: make fragment identifications less predictable
[ Backport of upstream commit 87c48fa3b4630905f98268dde838ee43626a060c ] Fernando Gont reported current IPv6 fragment identification generation was not secure, because using a very predictable system-wide generator, allowing various attacks. IPv4 uses inetpeer cache to address this problem and to get good performance. We'll use this mechanism when IPv6 inetpeer is stable enough in linux-3.1 For the time being, we use jhash on destination address to provide less predictable identifications. Also remove a spinlock and use cmpxchg() to get better SMP performance. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'net')
-rw-r--r--net/ipv6/af_inet6.c2
-rw-r--r--net/ipv6/ip6_output.c40
-rw-r--r--net/ipv6/udp.c2
3 files changed, 38 insertions, 6 deletions
diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index 3b5669a2582d..559123644e5d 100644
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -1078,6 +1078,8 @@ static int __init inet6_init(void)
goto out;
}
+ initialize_hashidentrnd();
+
err = proto_register(&tcpv6_prot, 1);
if (err)
goto out;
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 9d4b165837d6..16612968aaaf 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -596,6 +596,35 @@ int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
return offset;
}
+static u32 hashidentrnd __read_mostly;
+#define FID_HASH_SZ 16
+static u32 ipv6_fragmentation_id[FID_HASH_SZ];
+
+void __init initialize_hashidentrnd(void)
+{
+ get_random_bytes(&hashidentrnd, sizeof(hashidentrnd));
+}
+
+static u32 __ipv6_select_ident(const struct in6_addr *addr)
+{
+ u32 newid, oldid, hash = jhash2((u32 *)addr, 4, hashidentrnd);
+ u32 *pid = &ipv6_fragmentation_id[hash % FID_HASH_SZ];
+
+ do {
+ oldid = *pid;
+ newid = oldid + 1;
+ if (!(hash + newid))
+ newid++;
+ } while (cmpxchg(pid, oldid, newid) != oldid);
+
+ return hash + newid;
+}
+
+void ipv6_select_ident(struct frag_hdr *fhdr, struct rt6_info *rt)
+{
+ fhdr->identification = htonl(__ipv6_select_ident(&rt->rt6i_dst.addr));
+}
+
int ip6_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *))
{
struct sk_buff *frag;
@@ -680,7 +709,7 @@ 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 +855,7 @@ 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;
@@ -1072,7 +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;
@@ -1116,7 +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);
@@ -1282,7 +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;
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 328985c40883..29213b51c499 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -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()