[openssl-dev] Is X509_free(NULL) ok?

[Mischa Salle]

Hi,

I think it should be documented, but currently the two supported
branches are ok with NULL:
- following from IMPLEMENT_ASN1_FUNCTIONS(X509), for both
openssl-1.0.2n and 1.1.0g:
- 1.0.2n ends up in asn1_item_combine_free()
- 1.1.0g ends up in asn1_item_embed_free()
- in both cases an explicit check is done for NULL.

See
https://github.com/openssl/openssl/blob/OpenSSL_1_1_0g/crypto/asn1/tasn_fre.c#L36
and
https://github.com/openssl/openssl/blob/OpenSSL_1_0_2n/crypto/asn1/tasn_fre.c#L86

Mischa

On Thu, Dec 21, 2017 at 12:58 AM, Viktor Dukhovni
<openssl-users at dukhovni.org> wrote:
>
>
>> On Dec 20, 2017, at 5:50 PM, Ray Satiro via openssl-dev <openssl-dev at openssl.org> wrote:
>>
>> 'm trying to figure out whether it's supported to call X509_free(NULL)
>> in 1.0.2 and beyond. It's not documented what action occurs when the
>> pointer is null. Also generally speaking is it supported to call openssl
>> free functions with null pointers?
>
>
> All ASN.1 objects (such as X509 *) that are implemented via
> IMPLEMENT_ASN1_FUNCTIONS(typename) are freed by ASN1_item_free(),
> which I believe handles NULL inputs.
>
> If you don't see immediate crashes on trying it, you can use it
> on NULL inputs with confidence that this is intentional and not
> going to change.
>
> --
> --
>         Viktor.
>
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