bug: invalid type: string \"FROST-secp256k1-SHA256-v1\", expected a borrowed string

[mimoo]

I'm getting the following error:

error while reading file: Error("invalid type: string \"FROST-secp256k1-SHA256-v1\", expected a borrowed string", line: 4, column: 46)

after serializing and deserializing a frost::keys::KeyPackage with json_serde.

[mimoo]

I think the bug is in src/serialization.rs of frost-core:

/// Deserialize a placeholder ciphersuite field, checking if it's the ciphersuite ID string.
#[cfg(feature = "serde")]
pub(crate) fn ciphersuite_deserialize<'de, D, C>(deserializer: D) -> Result<(), D::Error>
where
    D: serde::Deserializer<'de>,
    C: Ciphersuite,
{
    if deserializer.is_human_readable() {
-        let s: &str = serde::de::Deserialize::deserialize(deserializer)?;
+        let s: String = serde::de::Deserialize::deserialize(deserializer)?;
        if s != C::ID {
            Err(serde::de::Error::custom("wrong ciphersuite"))
        } else {
            Ok(())
        }
    } else {
        let buffer: [u8; 4] = serde::de::Deserialize::deserialize(deserializer)?;
        if buffer != short_id::<C>() {
            Err(serde::de::Error::custom("wrong ciphersuite"))
        } else {
            Ok(())
        }
    }
}

[conradoplg]

Interesting. The fix seems correct but I can't come up with a test case that shows the issue. I'd like to add a test to exercise it. Can you share how are you serializing/deserializing it?

[mimoo]

are you using serde_json in your test? I just use serde_json::{to_string, from_str}()

[conradoplg]

are you using serde_json in your test? I just use serde_json::{to_string, from_str}()

Yes. This test passes:

#[test]
fn check_key_package_serialization2() {
    let json = r#"{
        "header": {
          "version": 0,
          "ciphersuite": "FROST-secp256k1-SHA256-v1"
        },
        "identifier": "000000000000000000000000000000000000000000000000000000000000002a",
        "signing_share": "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa9d1c9e899ca306ad27fe1945de0242b81",
        "verifying_share": "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798",
        "verifying_key": "0279be667ef9dcbbac55a06295ce870b07029bfcdb2dce28d959f2815b16f81798",
        "min_signers": 2
      }"#;
    let key_package: KeyPackage = serde_json::from_str(json).unwrap();
    let json: String = serde_json::to_string(&key_package).unwrap();
    println!("{}", json);
    let _key_package: KeyPackage = serde_json::from_str(&json).unwrap();
}

I think it fails when it can't get a reference to the ciphersuite substring inside the JSON string, which usually happens if the string has some escape code, which isn't the case.

[mimoo]

I was doing something similar to this but reading from a file instead. Not sure why your test pass when I couldn't do that on my end :D