OpenSSL VS s2n

Today, April 7th, 2024, marks the 10-year anniversary since CVE-2014-0160 was published. This security vulnerability known as "Heartbleed" was a flaw in the OpenSSL cryptography software, the most popular option to implement Transport Layer Security (TLS). In more layman's terms, if you type https:// in your browser address bar, chances are high that you are interacting with OpenSSL.

At this point I pretty much understand the entire process on how the xz backdoor came to be: its execution stages, extraction from binary "test" files etc. But one thing puzzles me: how can the ifunc mechanism be used to replace something like RSA_public_decrypt? Granted this probably stems from my lack of understanding of ifunc, but I was under the impression that in order for the ifunc mechanism to work in your code, you have to explicitly mark specific function with multiple implementations with __attribute__ ((ifunc ("the_resolver_function"))). Looking at the source code of the RSA function in question, ifunc attribute isn't present:

https://github.com/openssl/openssl/blob/master/crypto/rsa/rsa_crpt.c#L51

So how does the backdoor actually replace the call? Does this means that the ifunc mechanism can be used to override pretty much anything on the system?

OpenSSL and Go crypt/tls has no support yet, so none of the webservers that depend on them support it. Apache, Nginx, and Caddy, they all need upstream ECH support first.

- https://github.com/openssl/openssl/issues/7482

- https://github.com/openssl/openssl/pull/22938

- https://github.com/golang/go/issues/63369

If I'm understanding the draft correctly, I think the webserver you're hosting your sites on would need it implemented as it requires private keys and ECH configuration. In the example of nginx since it uses openssl, openssl would need to implement it. I found an issue on their Github but it's still open: https://github.com/openssl/openssl/issues/7482

I confirmed that the systm was on 1.1.1f with openssl version command. Hmm...... I check the openssl version in the repo with apt list... LOL package names wernt helpful. finally went to the repo pages and found that its still on 1.1.1f, https://launchpad.net/ubuntu/+source/openssl. Meenwhile I looked up the version history on https://www.openssl.org/ and saw that 1.1.1v was released at the beginning of this month... ok. I can understand it it was out less then 30 days. I looked up when f came out, end of MARCH 2020. NEARLY 3-1/2 YEARS

It seems to support multiple options but requires you pick at least one of them. https://github.com/aws/s2n-tls/blob/main/docs/BUILD.md#build...

I think GnuTLS is probably the second most popular TLS library, after openssl.

I'll also mentions s2n and rustls-ffi for completeness as C libraries, though the former isn't widely used, and the latter is very experimental still. https://github.com/aws/s2n-tls and https://github.com/rustls/rustls-ffi respectively.

I've seen operating on unauthenticated plaintext enough times to list it as my own pet peeve with AES-GCM. But it's a problem for chunked messages too. A few years ago we released a SCRAM mode that makes very minimal changes to AES-GCM so that it mathematically can't operate on unauthenticated plaintext. https://github.com/aws/s2n-tls/tree/main/scram

> The documentation is kind of vague, but apparently you have to re-enable it regularly.[3]

This is correct. And in the end it means more or less that setting the socket option is more of a way of sending an explicit ACK from userspace than a real setting.

It's not great for common use-cases, because making userspace care about ACKs will obviously degrade efficiency (more syscalls).

However it can make sense for some use-cases. E.g. I saw the s2n TLS library using QUICKACK to avoid the TLS handshake being stuck [1]. Maybe also worthwhile to be set in some specific RPC scenarios where the server might not immediately send a response on receiving the request, and where the client could send additional frames (e.g. gRPC client side streaming, or in pipelined HTTP requests if the server would really process those in parallel and not just let them sit in socket buffers).

[1] https://github.com/aws/s2n-tls/blob/46c47a71e637cabc312ce843...

It looks like by default s2n-quic uses this TLS implementation, which is not based on the ring crate (though it is written in C)

https://github.com/aws/s2n-tls

I would be interested in the other SSL implementations:

- https://github.com/awslabs/s2n

- https://boringssl.googlesource.com/boringssl

- https://bearssl.org/

Are these subpar implementations or there are other reasons not to use these?