Module subject_token 

Subject Token Credential Type.

A subject token is a credential that asserts the identity of a workload, application, or a user. In the case of the Workload Identity Federation flow, this allows applications to authenticate to Google Cloud, instead of using long-lived service account keys. The process involves exchanging this subject token for a short-lived Google Cloud access token via the Security Token Service (STS).

This module provides the SubjectTokenProvider trait, which is used to fetch subject tokens. The Google Cloud client libraries for Rust will typically use the SubjectTokenProvider automatically for external account credentials. You might need to implement this trait for advanced authentication scenarios where you want to integrate a custom subject token fetching mechanism.

Example

#[derive(Debug)]
struct CustomProviderError {
    message: String,
    is_transient: bool,
}

impl fmt::Display for CustomProviderError {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "CustomProviderError: {}", self.message)
    }
}

impl Error for CustomProviderError {}

impl SubjectTokenProviderError for CustomProviderError {
    fn is_transient(&self) -> bool {
        self.is_transient
    }
}

#[derive(Debug)]
struct MyCustomProvider {
    api_key: String,
}

impl SubjectTokenProvider for MyCustomProvider {
    type Error = CustomProviderError;

    async fn subject_token(&self) -> Result<SubjectToken, Self::Error> {
            let token_from_idp = "a-very-secret-token-from-your-idp";
            Ok(SubjectTokenBuilder::new(token_from_idp.to_string()).build())
    }
}

Structs

Builder

A builder for SubjectToken instances.

SubjectToken

Represents a third-party subject token used for authentication.

Traits

SubjectTokenProvider

Trait for providing a third-party subject token.