It mostly seems to cause an inconsistency in that sometimes
core_obj_create returns 1 if the OID already exists and sometimes it
returns 0.
Really core_obj_create should be a thin wrapper around OBJ_create. It
probably shouldn't do the initial check at all and just call OBJ_create
- which would make it always consistent, i.e. return 0 if it already exists.
oqsprovider probably needs to be tolerant of this failure condition,
i.e. it doesn't care if it already exists - so ignore a 0 return.
Matt
On 05/10/2023 08:39, Thomas Bailleux wrote:
Hello OpenSSL,
I'm currently writing a multi-threaded application using OpenSSL 3.1.
For some reason, I've decided to instantiate a `OSSL_LIB_CTX` per thread.
I'm also trying the provider API with oqs-provider, and I ran into an
issue that is caused
by the fact that `core_obj_create` is called by `OSSL_PROVIDER_load`
which itself is called by multiple threads running at the same time.
I described the bug in the following thread:
https://github.com/open-quantum-safe/oqs-provider/issues/272
<https://github.com/open-quantum-safe/oqs-provider/issues/272>
Basically, the oqs-provider init function registers some custom OIDs
using the `core_obj_create` which makes a call to `OBJ_create`.
As described in the BUGS section of the `OBJ_create` man page[1] of
*OpenSSL 3.0*, `OBJ_create` used to be non thread-safe.
However, in *OpenSSL 3.1*[2], it is thread safe:
These functions were not thread safe in OpenSSL 3.0 and before.
So I think there is a race condition in `core_obj_create`[3] function:
the function checks if the OID already exists, if so it returns OK (1),
otherwise it makes a call to `OBJ_create`. The TOCTOU is happening
between these two statements basically.
What do you suggest to mitigate this issue?
Regards,
- thomas
[1]: https://www.openssl.org/docs/man3.0/man3/OBJ_create.html
<https://www.openssl.org/docs/man3.0/man3/OBJ_create.html>
[2]: https://www.openssl.org/docs/man3.1/man3/OBJ_create.html
<https://www.openssl.org/docs/man3.1/man3/OBJ_create.html>
[3]:
https://github.com/openssl/openssl/blob/9c20f5db0feaddc4c9ea4c4b2b07e6d87d6701f1/crypto/provider_core.c#L2127-L2133 <https://github.com/openssl/openssl/blob/9c20f5db0feaddc4c9ea4c4b2b07e6d87d6701f1/crypto/provider_core.c#L2127-L2133>
--
Thomas Bailleux
Cryptography software engineer
thomas@xxxxxxxxxxxxx <mailto:thomas@xxxxxxxxxxxxx>
+33 6 47 04 61 58 | Paris, FRANCE
