CVE-2020-15237 — Possible timing attack in shrine — CVE Details

### Impact When using the `derivation_endpoint` plugin, it's possible for the attacker to use a timing attack to guess the signature of the derivation URL. ### Patches The problem has been fixed by comparing sent and calculated signature in constant time, using `Rack::Utils.secure_compare`. Users using the `derivation_endpoint` plugin are urged to upgrade to Shrine 3.3.0 or greater. ### Workarounds Users of older Shrine versions can apply the following monkey-patch after loading the `derivation_endpoint` plugin: ```rb class Shrine class UrlSigner def verify_signature(string, signature) if signature.nil? fail InvalidSignature, "missing \"signature\" param" elsif !Rack::Utils.secure_compare(signature, generate_signature(string)) fail InvalidSignature, "provided signature does not match the calculated signature" end end end end ``` ### References You can read more about timing attacks [here](https://en.wikipedia.org/wiki/Timing_attack).