Commit df453700 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

inet: switch IP ID generator to siphash 



According to Amit Klein and Benny Pinkas, IP ID generation is too weak
and might be used by attackers.

Even with recent net_hash_mix() fix (netns: provide pure entropy for net_hash_mix())
having 64bit key and Jenkins hash is risky.

It is time to switch to siphash and its 128bit keys.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reported-by: default avatarAmit Klein <aksecurity@gmail.com>
Reported-by: default avatarBenny Pinkas <benny@pinkas.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 180a8c3d

include/linux/siphash.h

+5 −0
Original line number Diff line number Diff line
@@ -21,6 +21,11 @@ typedef struct { 
	u64 key[2];

} siphash_key_t;



static inline bool siphash_key_is_zero(const siphash_key_t *key)

{

	return !(key->key[0] | key->key[1]);

}



u64 __siphash_aligned(const void *data, size_t len, const siphash_key_t *key);

#ifndef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS

u64 __siphash_unaligned(const void *data, size_t len, const siphash_key_t *key);

include/net/netns/ipv4.h

+2 −0
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#include <linux/uidgid.h>

#include <net/inet_frag.h>

#include <linux/rcupdate.h>

#include <linux/siphash.h>



struct tcpm_hash_bucket;

struct ctl_table_header;
@@ -217,5 +218,6 @@ struct netns_ipv4 { 
	unsigned int	ipmr_seq;	/* protected by rtnl_mutex */



	atomic_t	rt_genid;

	siphash_key_t	ip_id_key;

};

#endif

net/ipv4/route.c

+7 −5
Original line number Diff line number Diff line
@@ -500,15 +500,17 @@ EXPORT_SYMBOL(ip_idents_reserve); 


void __ip_select_ident(struct net *net, struct iphdr *iph, int segs)

{

	static u32 ip_idents_hashrnd __read_mostly;

	u32 hash, id;



	net_get_random_once(&ip_idents_hashrnd, sizeof(ip_idents_hashrnd));

	/* Note the following code is not safe, but this is okay. */

	if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))

		get_random_bytes(&net->ipv4.ip_id_key,

				 sizeof(net->ipv4.ip_id_key));



	hash = jhash_3words((__force u32)iph->daddr,

	hash = siphash_3u32((__force u32)iph->daddr,

			    (__force u32)iph->saddr,

			    iph->protocol ^ net_hash_mix(net),

			    ip_idents_hashrnd);

			    iph->protocol,

			    &net->ipv4.ip_id_key);

	id = ip_idents_reserve(hash, segs);

	iph->id = htons(id);

}

net/ipv6/output_core.c

+16 −14
Original line number Diff line number Diff line
@@ -10,15 +10,25 @@ 
#include <net/secure_seq.h>

#include <linux/netfilter.h>



static u32 __ipv6_select_ident(struct net *net, u32 hashrnd,

static u32 __ipv6_select_ident(struct net *net,

			       const struct in6_addr *dst,

			       const struct in6_addr *src)

{

	const struct {

		struct in6_addr dst;

		struct in6_addr src;

	} __aligned(SIPHASH_ALIGNMENT) combined = {

		.dst = *dst,

		.src = *src,

	};

	u32 hash, id;



	hash = __ipv6_addr_jhash(dst, hashrnd);

	hash = __ipv6_addr_jhash(src, hash);

	hash ^= net_hash_mix(net);

	/* Note the following code is not safe, but this is okay. */

	if (unlikely(siphash_key_is_zero(&net->ipv4.ip_id_key)))

		get_random_bytes(&net->ipv4.ip_id_key,

				 sizeof(net->ipv4.ip_id_key));



	hash = siphash(&combined, sizeof(combined), &net->ipv4.ip_id_key);



	/* Treat id of 0 as unset and if we get 0 back from ip_idents_reserve,

	 * set the hight order instead thus minimizing possible future
@@ -41,7 +51,6 @@ static u32 __ipv6_select_ident(struct net *net, u32 hashrnd, 
 */

__be32 ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb)

{

	static u32 ip6_proxy_idents_hashrnd __read_mostly;

	struct in6_addr buf[2];

	struct in6_addr *addrs;

	u32 id;
@@ -53,11 +62,7 @@ __be32 ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb) 
	if (!addrs)

		return 0;



	net_get_random_once(&ip6_proxy_idents_hashrnd,

			    sizeof(ip6_proxy_idents_hashrnd));



	id = __ipv6_select_ident(net, ip6_proxy_idents_hashrnd,

				 &addrs[1], &addrs[0]);

	id = __ipv6_select_ident(net, &addrs[1], &addrs[0]);

	return htonl(id);

}

EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);
@@ -66,12 +71,9 @@ __be32 ipv6_select_ident(struct net *net, 
			 const struct in6_addr *daddr,

			 const struct in6_addr *saddr)

{

	static u32 ip6_idents_hashrnd __read_mostly;

	u32 id;



	net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));



	id = __ipv6_select_ident(net, ip6_idents_hashrnd, daddr, saddr);

	id = __ipv6_select_ident(net, daddr, saddr);

	return htonl(id);

}

EXPORT_SYMBOL(ipv6_select_ident);

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