From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: Eric Dumazet <edumazet@google.com>
Cc: netdev <netdev@vger.kernel.org>,
Eric Biggers <ebiggers@kernel.org>,
"open list:HARDWARE RANDOM NUMBER GENERATOR CORE"
<linux-crypto@vger.kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
David Miller <davem@davemloft.net>,
Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>,
Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
Jason Baron <jbaron@akamai.com>,
Christoph Paasch <cpaasch@apple.com>,
David Laight <David.Laight@aculab.com>,
Yuchung Cheng <ycheng@google.com>
Subject: Re: [PATCH 1/2] net: fastopen: make key handling more robust against future changes
Date: Tue, 18 Jun 2019 11:41:35 +0200 [thread overview]
Message-ID: <CAKv+Gu894bEEzpKNDTaNiiNJTFoUTYQuFjBBm-ezdkrzW5fyNQ@mail.gmail.com> (raw)
In-Reply-To: <CANn89iJuTq36KMf1madQH08g6K0a-Uj-PDH80ao9zuEw+WNcZg@mail.gmail.com>
On Tue, 18 Jun 2019 at 11:39, Eric Dumazet <edumazet@google.com> wrote:
>
> On Tue, Jun 18, 2019 at 2:32 AM Ard Biesheuvel
> <ard.biesheuvel@linaro.org> wrote:
> >
> > Some changes to the TCP fastopen code to make it more robust
> > against future changes in the choice of key/cookie size, etc.
> >
> > - Instead of keeping the SipHash key in an untyped u8[] buffer
> > and casting it to the right type upon use, use the correct
> > siphash_key_t type directly. This ensures that the key will
> > appear at the correct alignment if we ever change the way
> > these data structures are allocated. (Currently, they are
> > only allocated via kmalloc so they always appear at the
> > correct alignment)
> >
> > - Use DIV_ROUND_UP when sizing the u64[] array to hold the
> > cookie, so it is always of sufficient size, even when
> > TCP_FASTOPEN_COOKIE_MAX is no longer a multiple of 8.
> >
> > - Add a key length check to tcp_fastopen_reset_cipher(). No
> > callers exist currently that fail this check (they all pass
> > compile constant values that equal TCP_FASTOPEN_KEY_LENGTH),
> > but future changes might create problems, e.g., by leaving part
> > of the key uninitialized, or overflowing the key buffers.
> >
> > Note that none of these are functional changes wrt the current
> > state of the code.
> >
> ...
>
> > - memcpy(ctx->key[0], primary_key, len);
> > + if (unlikely(len != TCP_FASTOPEN_KEY_LENGTH)) {
> > + pr_err("TCP: TFO key length %u invalid\n", len);
> > + err = -EINVAL;
> > + goto out;
> > + }
>
>
> Why a pr_err() is there ?
>
> Can unpriv users flood the syslog ?
They can if they could do so before: there was a call to
crypto_cipher_setkey() in the original pre-SipHash code which would
also result in a pr_err() on an invalid key length. That call got
removed along with the AES cipher handling, and this basically
reinstates it, as suggested by EricB.
next prev parent reply other threads:[~2019-06-18 9:41 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-18 9:32 [PATCH 0/2] net: fastopen: follow-up tweaks for SipHash switch Ard Biesheuvel
2019-06-18 9:32 ` [PATCH 1/2] net: fastopen: make key handling more robust against future changes Ard Biesheuvel
2019-06-18 9:39 ` Eric Dumazet
2019-06-18 9:41 ` Ard Biesheuvel [this message]
2019-06-18 9:53 ` Eric Dumazet
2019-06-18 10:02 ` Ard Biesheuvel
2019-06-18 18:18 ` Eric Biggers
2019-06-18 18:19 ` Eric Dumazet
2019-06-18 9:32 ` [PATCH 2/2] net: fastopen: use endianness agnostic representation of the cookie Ard Biesheuvel
2019-06-18 18:22 ` Eric Biggers
2019-06-18 18:40 ` Ard Biesheuvel
2019-06-18 22:40 ` David Miller
2019-06-18 9:37 ` [PATCH 0/2] net: fastopen: follow-up tweaks for SipHash switch Eric Dumazet
2019-06-18 9:38 ` Ard Biesheuvel
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