Re: [PATCH 1/5] selftests/sgx: Fix uninitialized pointer dereference in error path.

[Jo Van Bulck]

On 03.08.23 05:51, Huang, Kai wrote:
> Is it safe to assume EVP_MD_CTX_destroy() can always handle a NULL ctx?
>
> The manpage says:
>
> EVP_MD_CTX_destroy() cleans up digest context ctx and frees up the space
> allocated to it, it should be called only on a context created using
> EVP_MD_CTX_create().

Thank you for pointing this out. Afais the implementations I've seen can 
handle NULL, and similar error-handling paths exists where 
EVP_MD_CTX_destroy() is called with a NULL pointer exist in several 
places in the openSSL code.

That being said, this indeed not explicit in the specification (unlike 
RSA_free() which is called just after and explicitly specifies that NULL 
is okay). So you're probably right that it's generally safer to not call 
EVP_MD_CTX_destroy() with a NULL pointer.

I'll include an extra check for this in the next patch revision.