Custom Authentication

To add custom authentication modules to a request, you need to create a struct that implements the Auth interface. This interface has two methods:

type Auth interface {
    Prepare() error
    Apply(addHeaderFunc func(key, value string), setTransportFunc(transport http.RoundTripper))
}

The Prepare method is called before the request is executed. For Oauth2, this part performs the authentication steps. The Apply method is called when the request is executed, and adds the required metadata to the request headers or transport.

Below are some examples of custom auth modules compatible with GREQ.

Basic Auth

type BasicAuth struct {
    Username string
    Password string
}

func (b BasicAuth) Prepare() error {
    return nil
}

func (b BasicAuth) Apply(addHeaderFunc func(key, value string), setTransportFunc func(transport http.RoundTripper)) {
    
    // Adds a request Authorization header with the basic auth credentials
    addHeaderFunc(
        "Authorization", 
        "Basic "+base64.StdEncoding.EncodeToString(
            []byte(b.Username+":"+b.Password),
        ),
    )
}

mTLS Authentication

type CertificateAuth struct {
    CertFile string
    KeyFile string
}

func (c CertificateAuth) Prepare() error {
    return nil
}

func (c CertificateAuth) Apply(addHeaderFunc func(key, value string), setTransportFunc func(transport http.RoundTripper)) {
    // Load the certificate and key files
    cert, err := tls.LoadX509KeyPair(c.CertFile, c.KeyFile)
    if err != nil {
        panic(err)
    }

    // Create a new transport with the certificate
    transport := &http.Transport{
        TLSClientConfig: &tls.Config{
            Certificates: []tls.Certificate{cert},
        },
    }

    // Set the transport
    setTransportFunc(transport)
}