Re: Concerns about the use of OPENSSL_cleanse()

[Jeffrey Altman]

Rich Salz wrote:

Hmm, so OpenSSL is depending on NULL being all-bytes-zero. :)

Funny about that.  :-)

Probably a safe assumption, although theoretically you shouldn't do that.

It really wouldn't matter what assumption you made. At some point there needs to be a test:

Is this structure initialized?

And assigning random values to a structure will never allow the test to properly succeed.

But this does make me think that perhaps a better approach is to have a bunch of static instances:
X509_STORE_ctx nil_x509_store_ctx;
RSA nil_RSA;
...
etc.

Then OPENSSL_cleanse is
OPENSSL_cleanse2(volatile void* dest, volatile void* in, size_t s)
{
memcpy(dest, in, s);
/* play usual "force used" tricks here */
}

Another approach to consider is implementing special XXX_cleanse() functions that are smart about which fields can be randomized and which ones (ie, pointers) must be set to zero.



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