Re: CVE request (sort of): Quagga BGP crasher

[Florian Weimer <fw () deneb enyo de>]

* Florian Weimer:

> * Jon Oberheide:
>
> > Looks like the Quagga code in bgp_aspath.c is assuming that converting
> > each ASN of the AS path to a string will be 5 bytes plus a space
> > (#define ASN_STR_LEN (5 + 1)).  Therefore, it allocates (ASN_STR_LEN *
> > the number of ASNs in the path segment) bytes to snprintf into when
> > creating the pretty-print version of the AS path.
>
> Sure, this is the part I understand.  It's not clear why this code is
> hit when there isn't much logging going on.  People have also run
> "show ip bgp ROUTE" for paths with six-digit ASNs, with
> supposedly-broken bgpd versions, and did not observe a crash.

It seems that bgpd uses the textual representation of AS paths for
hash-consing them.  That's why the crash happens even without logging
enabled.