Thread: Re: Fix for buffer overflow ready [was: Fwd: Bug#247306: odbc-postgresql: SIGSEGV with long inputs (> 10000 bytes)]

Martin Pitt wrote:
> The problem is that make_string() in misc.c does not check whether
> the target buffer is big enough to hold the copied string.
>
> I added a bufsize parameter to make_string() and used it in all calls
> to it. I tried it with my php4 crash test script and now it works
> properly.

Silently truncating various pieces of information is probably not the
right thing.  What are you truncating?  If it's a query string you
might open yourself up to SQL-injection type problems.

Plus, the ODBC driver appears to have buffer overruns all over the
place.  We need to replace every instance of strcpy, strcat, sprintf,
make_string, and the various other feeble attempts with pqexpbuffer
from libpq.  That's the only way to solve this problem once and for
all.

Hi!

On 2004-05-13 19:43 +0200, Peter Eisentraut wrote:
> Silently truncating various pieces of information is probably not the
> right thing.

But IMHO still better than overwriting arbitrary other data and code.
If an user supplies bogus input, he cannot expect to get something
sane out.

> What are you truncating?

By now:

- DSN, username, password, and the whole connection string;

- table names in info.c:
  make_string(szTableName, cbTableName, pktab, sizeof(pktab));

- Two calls in info.c:
  make_string(szPkTableName, cbPkTableName, pk_table_needed, sizeof(pk_table_needed));
  make_string(szFkTableName, cbFkTableName, fk_table_needed, sizeof(fk_table_needed));

If these values should not be truncated, then psqlodbc should not use
fixed buffer sizes. Currently truncating them is way more sane than
letting them mess up the whole memory.

> If it's a query string you might open yourself up to SQL-injection
> type problems.

I don't think that the patch affects whole query strings, but of
course I may be wrong. The point of this patch was to fix the most
apparent overflows with least possible changes, and after a week of
silence on the lists I just had to do something about it. And now at
least the connection and exec methods seem to work safely.

> Plus, the ODBC driver appears to have buffer overruns all over the
> place.  We need to replace every instance of strcpy, strcat, sprintf,
> make_string, and the various other feeble attempts with pqexpbuffer
> from libpq.  That's the only way to solve this problem once and for
> all.

I would be glad if the next psqlodbc version would be written in a
sane way, without fixed string lengths and with a clear and safe
string "class" interface. But doing this is far beyond the scope of a
security patch (especially for Debian stable).

One question: which mailing list is the better place to discuss this?
-odbc or -bugs?

Thanks and have a nice day!

Martin

--
Martin Pitt                 Debian GNU/Linux Developer
martin@piware.de                      mpitt@debian.org
http://www.piware.de             http://www.debian.org