Patrik Carlsson wrote:
>
> You don't need p.
>
> Patrik
>
You do need p... see below.
> Dr Stephen Henson wrote:
>
> > The correct way is this...
> >
> > int len;
> > unsigned char *buf, *p;
> >
> > len = i2d_PKCS7(p7, NULL);
> > buf = malloc(len);
> > p = buf;
> > i2d_PKCS7(p7, &p);
> >
When you call any i2d_XXX routine the pointer you pass to it gets
automatically incremented to point to the end of the data it has just
written. This is because thats often what you want to do with the ASN1
routines.
This is usually handled by saving the location of the buffer in a
temporary variable, in this case p.
If just pass &buf instead then it will end up pointing past the end of
the buffer after the call and any call to free(buf) will free an invalid
pointer. This will give the impression that the data written is garbage
and may also cause segmentation violations later on
The alternative is to do:
buf -= len;
after the call in which case you don't need p.
Steve.
--
Dr Stephen N. Henson. http://www.drh-consultancy.demon.co.uk/
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Core developer of the OpenSSL project: http://www.openssl.org/
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