Re: [PATCH] sctp: integer overflow in sctp_auth_create_key()

I agree that this is not a security issue if key_len can never get large.

So how about just removing the overflow check at all?

- xi

On Nov 28, 2011, at 10:45 AM, Vladislav Yasevich wrote:

Hmm.  Yes, this is a more correct check.

Acked-by: Vlad Yasevich <redacted>


However, I don't think this is a security issue.  As I've written before, this function is
called from 2 places:

 1) setsockopt() code path

 2) sctp_auth_asoc_set_secret() code path

In case (1), sca_keylength is never going to exceed 65535 since it's
bounded by a u16 from the user api.  As such, The integer promotion will
not impact anything and the malloc() will never overflow.

In case (2), sca_keylength is computed based on the key the user provided
(MAX_USHORT) and the combination of protocol negotiated data where that
combination has a max size of 3 * MAX_USHORT (see sctp_auth_make_key_vector()).
So, even this case, our maximum key length can be 4* MAX_USHORT which still
will always be below MAX_INT and will not overflow.

So, I don't think there is big security consideration here, just a bad
check that just happens to always work.

-vlad