Re: CVS commit: src/crypto/external/bsd/netpgp/dist

[Alistair Crooks <agc%pkgsrc.org@localhost>]

On Fri, May 08, 2009 at 01:18:38PM -0400, Perry E. Metzger wrote:
> 
> "Alistair G. Crooks" <agc%netbsd.org@localhost> writes:
> 
> > Module Name:        src
> > Committed By:       agc
> > Date:               Fri May  8 06:06:39 UTC 2009
> >
> > Modified Files:
> >     src/crypto/external/bsd/netpgp/dist: TODO configure configure.ac
> >     src/crypto/external/bsd/netpgp/dist/src/bin: netpgp.c
> >     src/crypto/external/bsd/netpgp/dist/src/lib: config.h config.h.in
> >         crypto.c misc.c netpgp.c openssl_crypto.c reader.c signature.c
> >         signature.h version.h
> >
> > Log Message:
> [...]
> > + if setrlimit exists, set the core dump size to be 0
> >   (with thanks to mrg for the reference implementation)
> [...]
> 
> What's the threat model this is protecting against? Presumably, if a
> user can execute the program, and the program can read his keys, the
> uesr can already read his own keys, so having a core dump doesn't give
> the user information he didn't already have.

Heh, yeah, it's not really to do with keys, much more the passphrase,
which is dynamically allocated in a number of places in the library,
and I haven't finished auditing all of the places just yet.  I've
added code to zero out that memory after use when I can - some more
are still needed.

The threat that I'm protecting against here is that of information
disclosure coming from committing the passphrase to disk in a core
dump.  Having to remember to rm -P the core dump file is a pain, you
don't get a second chance at it, and after that there is still the
problem of any spared sectors.  I suspect you don't want a re-run of
the tls vs.  agc wars from a month ago.  Whilst most people will use
an encrypted block device of some description, others are prevented
from doing that for various reasons.  I'm especially sensitive about
passphrases here, since there's no way of changing a PGP passphrase
short of generating a new key.

I'd really recommend source-changes-full for reviewing the changes
that are made - the setrlimit(2) call is only made in the driver
program, not the library.

Regards,
Alistair