SMB3.0 alternate channel

[Arnab Bakshi]

Thanks Stefan..got it..sorry for bothering I figured it out after sending
out my question..my bad :(

Much thanks for the answer...


On Thu, Feb 14, 2013 at 7:22 PM, Stefan (metze) Metzmacher
<metze at samba.org>wrote:

> Hi Arnab,
>
> >   Was going through the smb2_key_derivation() function which generates
> the
> > session->signingKey from the session->sessionKey. As per the MS_SMB2 spec
> > section-3.1.4.2 page 130 the algorithm should be as specified
> > in [SP800-108] section 5.1 i.e KDF in counter mode with PRF as HMAC-256.
> > Also the [MS-SMB2] spec specifies a *'r'* value of 32 and 'L' value of
> 128.
> >
> > In the Samba-4.0.3  implementation that I downloaded I could see the
> > *'L'*value being defined but did not find the
> > *'r*' value anywhere which is supposed to be the size of binary string
> > representing the counter *'i'*.
>
>         uint8_t buf[4];
> ...
>
>         RSIVAL(buf, 0, i);
>         hmac_sha256_update(buf, sizeof(buf), &ctx);
> ...
>
> =>
> sizeof(buf)*8 = 32
>
> RSIVAL() fills buf with the 32-bit big endian representation of 'i'.
>
> >     Can anybody please throw some light on this?..Also do you have any
> > example values of session->sessionKey and session->signingKey using which
> > this function was validated..
>
> Ping me if you still need them.
>
> metze
>
>