Missing examples for custom API Gateway Authorizers

[mattiZed]

Hey guys,
first of all, appreciate your work on the project. Building web applications for AWS Lambda with minimal cold-start times is something that I have long been waiting for.

I'm a bit of a rust noob still, and my first project is trying to port a API Gateway custom authorizer from python to rust. I'm struggling to understand how the classes from event::apigw are intended to be used.

Something like

let statement = IamPolicyStatement {
    action: vec!["execute-api:Invoke".to_string()],
    effect: IamPolicyEffect::Allow,
    resource: vec!["*".to_string()],
    condition: None
};

does not work, because IamPolicyStatement is set to 'non_exhaustive'. I also did not find a new() Ctor. Could you point me to some example where it's clear how these structs should be used?

[mattiZed]

For some more context, here's what I'm currently doing:

struct PolicyGenerator {
    policy_statements: Vec<IamPolicyStatement>,
}

impl PolicyGenerator {
    fn new() -> Self {
        let mut generator = PolicyGenerator {
            policy_statements: vec![],
        };
        generator.deny_all();
        generator
    }

    pub fn allow_path(&mut self, method_arn: &str) {
        let mut statement = IamPolicyStatement::default();
        statement.action = vec!["execute-api:Invoke".to_string()];
        statement.effect = IamPolicyEffect::Allow;
        statement.resource = vec![method_arn.to_string()];
        self.policy_statements.push(statement)
    }

    fn deny_all(&mut self) {
        let mut statement = IamPolicyStatement::default();
        statement.action = vec!["execute-api:Invoke".to_string()];
        statement.effect = IamPolicyEffect::Deny;
        statement.resource = vec!["*".to_string()];
        self.policy_statements.push(statement)
    }

    pub fn generate(&mut self) -> ApiGatewayCustomAuthorizerPolicy {
        let mut policy = ApiGatewayCustomAuthorizerPolicy::default();
        policy.statement = self.policy_statements.clone();
        policy
    }
}

pub(crate) async fn function_handler(
    event: LambdaEvent<ApiGatewayCustomAuthorizerRequest>,
) -> Result<ApiGatewayCustomAuthorizerResponse, Error> {
    let payload = event.payload;
    let mut policy_generator = PolicyGenerator::new();

    if let Some(_token) = payload.authorization_token {
        // Do something with the token to identify auth scope
        // logic()
        policy_generator.allow_path("method_arn");
    }

    let policy = policy_generator.generate();
    let mut response = ApiGatewayCustomAuthorizerResponse::default();
    response.principal_id = Some("the_principal".to_string());
    response.policy_document = policy;
    Ok(response)
}

Hi, you can use the following pattern:

let policy_statement = {
    let mut statement = IamPolicyStatement::default();
    statement.action = vec!["execute-api:Invoke".to_string()];
    statement.effect = IamPolicyEffect::Allow;
    statement.resource = vec!["*".to_string()];
    statement
}

[mattiZed]

Alright, thanks!

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