netdev - Re: [PATCH net 1/2] ipv6: make exception cache less predictible

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Message-ID: <CAEA6p_CEqRPd8mUmEfVRxEm75iBcR=5Lo4H9v4v+zTMdN5rhQw@mail.gmail.com>
Date:   Mon, 30 Aug 2021 08:54:15 -0700
From:   Wei Wang <weiwan@...gle.com>
To:     David Ahern <dsahern@...il.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>, Willy Tarreau <w@....eu>,
        Keyu Man <kman001@....edu>, David Ahern <dsahern@...nel.org>,
        Martin KaFai Lau <kafai@...com>
Subject: Re: [PATCH net 1/2] ipv6: make exception cache less predictible

On Sun, Aug 29, 2021 at 5:39 PM David Ahern <dsahern@...il.com> wrote:
>
> On 8/29/21 3:16 PM, Eric Dumazet wrote:
> > From: Eric Dumazet <edumazet@...gle.com>
> >
> > Even after commit 4785305c05b2 ("ipv6: use siphash in rt6_exception_hash()"),
> > an attacker can still use brute force to learn some secrets from a victim
> > linux host.
> >
> > One way to defeat these attacks is to make the max depth of the hash
> > table bucket a random value.
> >
> > Before this patch, each bucket of the hash table used to store exceptions
> > could contain 6 items under attack.
> >
> > After the patch, each bucket would contains a random number of items,
> > between 6 and 10. The attacker can no longer infer secrets.
> >
> > This is slightly increasing memory size used by the hash table,
> > we do not expect this to be a problem.
> >
> > Following patch is dealing with the same issue in IPv4.
> >
> > Fixes: 35732d01fe31 ("ipv6: introduce a hash table to store dst cache")
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > Reported-by: Keyu Man <kman001@....edu>
> > Cc: Wei Wang <weiwan@...gle.com>
> > Cc: Martin KaFai Lau <kafai@...com>
> > ---
> >  net/ipv6/route.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
>
> Reviewed-by: David Ahern <dsahern@...nel.org>
>
Reviewed-by: Wei Wang <weiwan@...gle.com>

Thanks Eric!