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Re: Reducing the attack surface caused by Berkeley DB...




Replying to myself...

On 1/26/18 11:48 PM, Lionel Debroux wrote:
> Hi Scott,
>
> On 1/26/18 7:05 AM, Scott Kitterman wrote:
> > On Thursday, January 25, 2018 11:59:06 PM Lionel Debroux wrote:
> > >
> > > [...]
> > > ---
> > > Do you think we should start the journey of getting rid of
> > > libdb5.3 at a wide scale ? And if so, how to optimize resource
> > > usage in general ? :)
> > > ---
> >
> > Ultimately BDB is a dead end for non-AGPL projects.  So my answer to
> > your first question is a definite yes.
> >
> > I'd like to know what the preferred replacement is.  I maintain a
> > few less heavily used packages that use libdb5.3 and I need to know
> > what to tell upstream they should port to.  I don't know enough to
> > have a real technical opinion.  Is lmdb the general solution?
> In some (most ?) cases, it would seem so, indeed.
> But there's now a wider variety of key/value databases (even those
> which don't fork and communicate through *nix or network sockets)
> than, say, a decade ago. I remember that several years ago,
> bitcoind/bitcoin-qt switched from BDB to LevelDB.
>
> > As far as postfix goes (which I also co-maintain) that is a two
> > release cycle project (it's complicated, but upgrades don't work
> > otherwise - if anyone cares see what we did for postfix-sqlite.
> > It's no problem to switch to a difference default map type, but
> > it'd be nice if we could switch it once to something that was
> > otherwise already likely to be installed.
> liblmdb* or libleveldb* are much less popular in popcon by_inst than
> libdb, yeah...
>
>
> Do we know whether LMDB, and other candidate databases for replacing
> BDB, have received suitable hardening against data corruption and
> fuzzing ?
Well, now I know: some parts of LMDB have not received the appropriate
amount of hardening against data corruption.

A direct LMDB translation of the simple BDB fuzzing run I posted in
Debian BTS #652036:

# apt install lmdb-utils
$ rm -f input*
$ echo -e "key\nvalue" | mdb_load -T -n input
$ zzuf -qcs 0:1000 -C 10 -U 3 mdb_dump -n -l input
$ zzuf -qcs 0:1000 -C 10 -U 3 mdb_dump -n -a input
$ zzuf -qcs 0:1000 -C 10 -U 3 mdb_stat -n -e -fff -r -a input

yields an interesting assortment of SIGFPE, SIGABRT and SIGSEGV...
That's under sid amd64, with lmdb-utils / liblmdb0 0.9.21-1, which
packages the latest upstream release.
I replaced the sources with the latest ones from
https://github.com/LMDB/lmdb , since the commit logs mention e.g. "fix
FIRST_DUP/LAST_DUP cursor bounds check". AFAICS, it changes the set of
symbols, but not the outcome of zzuf... and unsurprisingly, afl-fuzz
following a build with afl-clang-fast destroys both mdb_dump and
mdb_stat within 2 seconds.

Oh well... time to report the issues, after letting afl run for a little
while longer, probably until tomorrow morning.


Bye,
Lionel.