Bug#511519: libcrypt-openssl-dsa-perl: return values of openssl functions.

Damyan Ivanov dmn at deian.org
Wed Jan 28 22:43:48 UTC 2009

-=| Kurt Roeckx, Wed, Jan 28, 2009 at 11:12:20PM +0100 |=-
> On Wed, Jan 28, 2009 at 11:52:18PM +0200, Damyan Ivanov wrote:
> > > However those functions can also return -1 on failure.  This
> > > would then mean that other applications making use of this
> > > could wrongly check the return value.
> > 
> > Since $dsa->verify(...) croaks in underlying OpenSSL call returns -1, 
> > it seems to me that croaking in do_verify(...) is the right thing to 
> > do.
> > 
> > From what I understand, verify() and do_verify() only differ in what 
> > they accept as parameters, otherwise the semantic is the same -- 
> > verify a signature.
> > 
> > Does in your opinion (1) patching do_verify() to croak if underlaying 
> > library call returns -1, (2) documenting the fact that both verify() 
> > and do_verify() may croak and (3) sending the patch upstream, would 
> > fix the bug?
> I have no idea what croak does exactly, but if it's some
> mechanisme to report error conditions, like a throw in C++,
> it might be a good way of doing it.

Sufficiently similar, yes.

> But then I have to wonder why croak isn't called in case
> of a 0 return value.  Both 0 and -1 are error cases.  And
> most applications don't care if 0 or -1 was returned.

From crypto/dsa/dsa_vrf.c (openssl source):

    /* returns
     *      1: correct signature
     *      0: incorrect signature
     *     -1: error
(and this is for both verify() and do_verify()

I think the intention in the perl wrappers is to mimic underlaying 
functionality -- tell you if a signature is valid via the return value 
-- except that it throws an exception if -1 is returned in order to 
signal the error condition.

So I think my propposal above is still good for Crypt::OpenSSL::DSA. 
Whether the code that uses it checks the [do_]verify() return code (or 
is prepared to handle the exception) is a whole new research.

The only package declaring dependency on libcrypt-openssl-dsa-perl is 

dam            JabberID: dam at jabber.minus273.org
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