I need to implement an Identity provider service (using node.js) that should be able to.

* Get, validate and parse (using private key and cretificate) the authentication request from SP [example](https://www.samltool.com/generic_sso_req.php)
* If everything is valid, respond with a signed XML response [example](https://www.samltool.com/generic_sso_res.php)

Is there a tool in node.js that can handle the IdP side of SAML protocol. i'm familiar with [samlify](https://samlify.js.org/#/), [saml2](https://www.npmjs.com/package/saml2-js), [passport-saml](http://www.passportjs.org/packages/passport-saml/), and all of them seem to handle the Service provider side of the protocol.

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If the packages mentioned here can serve to my needs, could you specify how exactly they handle this.
Any other directions and/or hints may be helpful. 

Thanks