netdev - [PATCH net 2/2] ipv4: use siphash instead of Jenkins in fnhe

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Message-Id: <20210825231729.401676-3-eric.dumazet@gmail.com>
Date:   Wed, 25 Aug 2021 16:17:29 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Willy Tarreau <w@....eu>, Keyu Man <kman001@....edu>
Subject: [PATCH net 2/2] ipv4: use siphash instead of Jenkins in fnhe_hashfun()

From: Eric Dumazet <edumazet@...gle.com>

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

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

Also remove the inline keyword, this really is distracting.

Fixes: d546c621542d ("ipv4: harden fnhe_hashfun()")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Keyu Man <kman001@....edu>
Cc: Willy Tarreau <w@....eu>
---
 net/ipv4/route.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 99c06944501ab1a8de0960acfdc9f1825b7079b1..a6f20ee3533554b210d27c4ab6637ca7a05b148b 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -600,14 +600,14 @@ static struct fib_nh_exception *fnhe_oldest(struct fnhe_hash_bucket *hash)
 	return oldest;
 }
 
-static inline u32 fnhe_hashfun(__be32 daddr)
+static u32 fnhe_hashfun(__be32 daddr)
 {
-	static u32 fnhe_hashrnd __read_mostly;
-	u32 hval;
+	static siphash_key_t fnhe_hash_key __read_mostly;
+	u64 hval;
 
-	net_get_random_once(&fnhe_hashrnd, sizeof(fnhe_hashrnd));
-	hval = jhash_1word((__force u32)daddr, fnhe_hashrnd);
-	return hash_32(hval, FNHE_HASH_SHIFT);
+	net_get_random_once(&fnhe_hash_key, sizeof(fnhe_hash_key));
+	hval = siphash_1u32((__force u32)daddr, &fnhe_hash_key);
+	return hash_64(hval, FNHE_HASH_SHIFT);
 }
 
 static void fill_route_from_fnhe(struct rtable *rt, struct fib_nh_exception *fnhe)
-- 
2.33.0.rc2.250.ged5fa647cd-goog