Ensure SRP BN_mod_exp follows the constant time path

[Viacheslav]

Hello,

I'd like to point out that there are two fixes missing from the upstream, is there any chance to get them incorporated?

https://github.com/openssl/openssl/pull/13888
https://github.com/openssl/openssl/pull/13889

There was no CVE assigned, it was fixed between 1.1.1i and 1.1.1j.

Best regards

[Viacheslav (vjacheslav)]

hi all, if I know what to change, where I can propose my diff?

[Viacheslav (vjacheslav)]

the fix is available in ubuntu/hirsute and higher, could you please answer how high is the chance to see it backported to ubuntu/focal?

https://git.launchpad.net/ubuntu/+source/openssl/diff/crypto/srp/srp_lib.c?id=49aeae384e37deee3292e3f7da1dce5e417769ea

[Adrien Nader (adrien)]

Hi. Openssl is a delicate component, used by many other packages. As a consequence, it is only patched if there is a strong need. Looking at the pull request you've linked to, this falls outside of the openssl threat model since it is local only. I'm not sure Ubuntu has a stricter threat model for openssl. I'm going to ask around but even if Ubuntu does, it is probably an exploit that is difficult to pull off on a component that is risky to touch. Overall I don't think it is likely that focal receives a corresponding update.

[Adrien Nader (adrien)]

I forgot to mention the outcome of the discussion: we're following openssl's own threat model here so there is no plan to patch and SRU that.