`decode` returns ExpiredSignature error when the `exp` field is missing

[gbaranski]

Hi, the decode returns ExpiredSignature error when the exp field is missing, is that the expected behaviour?

In my case the token has the exp field, which is defined as Option<DateTime<Utc>>, so that's not always there, and the code which looks like that:

#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub struct TokenClaims {
    pub sub: Uuid,
    #[serde(with = "chrono::serde::ts_seconds_option")]
    #[serde(skip_serializing_if = "Option::is_none")]
    #[serde(default)]
    pub exp: Option<DateTime<Utc>>,
}

let key = b"the-key";
let token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiI4Njg5M2MzMC00YmM3LTRhYWItYTg2NS1mYzdmZThhYmFiMDcifQ.bm2xVzyNq_ql-dLefhPV-aTqzqfsx8ld7ahzgO_brG4";
let mut validation = Validation::default();
validation.required_spec_claims.remove("exp");
let data: TokenData<TokenClaims> = decode(token, &DecodingKey::from_secret(key), &validation).unwrap();

[Keats]

required_spec_claims only checks for the presence/absence of the field. validate_exp is still set to true in your example. There's no way to say "only validate if the field is present".

[Keats]

It should work in 8.1.0