Re: PATCH: anti memleak part 1

[Brian Stafford <brian stafford uklinux net>]

On 2001.10.18 16:53:56 +0100 Peter Bloomfield wrote:

> > diff -ruN balsa-cvs/src/balsa-app.c balsa/src/balsa-app.c
> > --- balsa-cvs/src/balsa-app.c	Thu Oct 18 16:38:15 2001
> > +++ balsa/src/balsa-app.c	Thu Oct 18 16:51:17 2001
> ...
> > @@ -188,14 +186,14 @@
> >  static int
> >  tlsinteract (char *buf, int buflen, int rwflag, void *arg)
> >  {
> > -  char *pw;
> >    int len;
> > 
> > -  pw = balsa_app.smtp_certificate_passphrase;
> > -  len = strlen (pw);
> > +  len = strlen (balsa_app.smtp_certificate_passphrase);
> > +
> >    if (len + 1 > buflen)
> >      return 0;
> > -  strcpy (buf, pw);
> > +
> > +  buf = balsa_app.smtp_certificate_passphrase;
> >    return len;
> >  }
> >  #endif
> 
> I don't think this one works.

Quite right!

>  `tlsinteract' would have to be called 
> with `char **buf_p' instead of `char *buf', and then  you could end 
> with `*buf_p = balsa_app.smtp_certificate_passphrase;'

That won't work either.

>  In your 
> suggested code, `buf' is changed on the stack, but nothing is changed 
> in the caller's frame.

Basic C semantics.

The strcpy() is important.  It's because the pass phrase must be copied
to a buffer maintained by the OpenSSL code, hence the preceeding test
against the buffer length.

> If you *really* wanted to get rid of `char *pw', you could finish up 
> with `strcpy (buf, balsa_app.smtp_certificate_passphrase);'

Not sure why I wrote the code like this.  Either I had a good reason
that escapes me just now, or I copied and edited it from somewhere else!

Brian Stafford