LibWeb: Don't import raw X25519 key of incorrect length

Author: https://github.com/hopafoot 🔰
Commit: ea8538ea49
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/5582
Reviewed-by: https://github.com/ADKaster ✅
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/trflynn89

Libraries/LibWeb/Crypto/CryptoAlgorithms.cpp

@@ -7258,6 +7258,11 @@ WebIDL::ExceptionOr<GC::Ref<CryptoKey>> X25519::import_key([[maybe_unused]] Web:
         if (!usages.is_empty())
             return WebIDL::SyntaxError::create(m_realm, "Usages must be empty"_string);
 
+        // AD-HOC: if the key length is not 32 bytes, then throw a DataError.
+        // See: https://github.com/w3c/webcrypto/issues/409
+        if (32 != key_data.get<ByteBuffer>().size())
+            return WebIDL::DataError::create(m_realm, "X25519 key must be 32 bytes"_string);
+
         // 2. Let algorithm be a new KeyAlgorithm object.
         auto algorithm = KeyAlgorithm::create(m_realm);