Stack overflow in RFC 8203 BGP admin. shutdown comm. handling since 7ff34ca2

[Ondrej Zajicek]

On Sun, Sep 08, 2019 at 05:54:35PM -0400, Daniel McCarney wrote:
> Hi Ondrej,
> 
> Thanks for the quick response.
> 
> > Unfortunately it has been included in released versions 1.6.7 and 2.0.5.
> 
> Bummer, apologies for missing that. Do you want to request a CVE or should I?

If you could, i would be glad.


> While I believe 7ff34ca2 introduced the ability to overflow a stack buffer it
> seems to me the original RFC 8203 support hasn't been correctly verifying
> shutdown communication `msg_len` since support was added in BIRD 2 versions >=
> 2.0.0 and BIRD 1 versions >= 1.6.4. Details to follow.

I think that the incorrect check in the original code also allows this
stack overflow, as a properly packed 255B message would trigger the first
condition but not the second, so would be accepted.

Therefore, the stack overflow could happen on BIRD 1 versions >= 1.6.4
and BIRD 2 versions >= 2.0.0.


The bugfix patches are:
1657c41c96b3c07d9265b07dd4912033ead4124b (1.6.x)
8388f5a7e14108a1458fea35bfbb5a453e2c563c (2.0.x)

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."