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ipv6: use siphash in rt6_exception_hash()

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A group of security researchers brought to our attention
the weakness of hash function used in rt6_exception_hash()

Lets use siphash instead of Jenkins Hash, to considerably
reduce security risks.

Following patch deals with IPv4.

Fixes: 35732d01fe ("ipv6: introduce a hash table to store dst cache")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Keyu Man <kman001@ucr.edu>
Cc: Wei Wang <weiwan@google.com>
Cc: Martin KaFai Lau <kafai@fb.com>
Acked-by: Wei Wang <weiwan@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2021-08-25 16:17:28 -07:00 committed by David S. Miller
parent 92ea47fe09
commit 4785305c05
1 changed files with 14 additions and 6 deletions
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20
net/ipv6/route.c
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@ -41,6 +41,7 @@
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/jhash.h>
#include <linux/siphash.h>
#include <net/net_namespace.h>
#include <net/snmp.h>
#include <net/ipv6.h>
@ -1484,17 +1485,24 @@ static void rt6_exception_remove_oldest(struct rt6_exception_bucket *bucket)
static u32 rt6_exception_hash(const struct in6_addr *dst,
const struct in6_addr *src)
{
static u32 seed __read_mostly;
u32 val;
static siphash_key_t rt6_exception_key __read_mostly;
struct {
struct in6_addr dst;
struct in6_addr src;
} __aligned(SIPHASH_ALIGNMENT) combined = {
.dst = *dst,
};
u64 val;
net_get_random_once(&seed, sizeof(seed));
val = jhash2((const u32 *)dst, sizeof(*dst)/sizeof(u32), seed);
net_get_random_once(&rt6_exception_key, sizeof(rt6_exception_key));
#ifdef CONFIG_IPV6_SUBTREES
if (src)
val = jhash2((const u32 *)src, sizeof(*src)/sizeof(u32), val);
combined.src = *src;
#endif
return hash_32(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT);
val = siphash(&combined, sizeof(combined), &rt6_exception_key);
return hash_64(val, FIB6_EXCEPTION_BUCKET_SIZE_SHIFT);
}
/* Helper function to find the cached rt in the hash table