2018-09-05, 13:48:48 +0000, Vakul Garg wrote:
>
>
> > -----Original Message-----
> > From: [email protected] <[email protected]> On
> > Behalf Of Sabrina Dubroca
> > Sent: Wednesday, September 5, 2018 6:52 PM
> > To: [email protected]
> > Cc: Sabrina Dubroca <[email protected]>; Boris Pismenny
> > <[email protected]>; Ilya Lesokhin <[email protected]>; Aviad
> > Yehezkel <[email protected]>; Dave Watson <[email protected]>
> > Subject: [PATCH net 3/3] tls: zero the crypto information from tls_context
> > before freeing
> >
> > This contains key material in crypto_send_aes_gcm_128 and
> > crypto_recv_aes_gcm_128.
> >
> > Fixes: 3c4d7559159b ("tls: kernel TLS support")
> > Signed-off-by: Sabrina Dubroca <[email protected]>
> > ---
> > include/net/tls.h | 1 +
> > net/tls/tls_main.c | 14 ++++++++++++--
> > 2 files changed, 13 insertions(+), 2 deletions(-)
> >
> > diff --git a/include/net/tls.h b/include/net/tls.h index
> > d5c683e8bb22..2010d23112f9 100644
> > --- a/include/net/tls.h
> > +++ b/include/net/tls.h
> > @@ -180,6 +180,7 @@ struct tls_context {
> > struct tls_crypto_info crypto_recv;
> > struct tls12_crypto_info_aes_gcm_128
> > crypto_recv_aes_gcm_128;
> > };
> > + char tls_crypto_ctx_end[0];
>
> This makes the key zeroization dependent upon the position of unions
> in structure.
Yes. I could add char tls_crypto_ctx_start[0].
> Can you zeroise the crypto_send, crypto_recv separately using two
> memzero_explicit calls?
It's not crypto_send, it's crypto_send_aes_gcm_128. I don't know how
likely it is that another crypto algorithm will ever be added, but
then you'd have to switch to zeroing that thing.
I had a different version of the patch that gave a name to those
unions, but then I need to change all the references everywhere and
the patch becomes a bit ugly, especially for net.
struct tls_context {
union {
struct tls_crypto_info info;
struct tls12_crypto_info_aes_gcm_128 aes_gcm_128;
} crypto_send;
union {
struct tls_crypto_info info;
struct tls12_crypto_info_aes_gcm_128 aes_gcm_128;
} crypto_recv;
[...]
}
Or even:
union tls_crypto_context {
struct tls_crypto_info info;
struct tls12_crypto_info_aes_gcm_128 aes_gcm_128;
};
struct tls_context {
union tls_crypto_context crypto_send;
union tls_crypto_context crypto_recv;
[...]
}
--
Sabrina
