rp: allow to set custom URL parameters (#273)

* rp: allow to set prompts in AuthURLHandler

Fixes #241

* rp: configuration for handlers with URL options to call RS

Fixes #265

example/client/app/app.go

@@ -54,10 +54,12 @@ func main() {
 		return uuid.New().String()
 	}
 
-	// register the AuthURLHandler at your preferred path
+	// register the AuthURLHandler at your preferred path.
-	// the AuthURLHandler creates the auth request and redirects the user to the auth server
+	// the AuthURLHandler creates the auth request and redirects the user to the auth server.
-	// including state handling with secure cookie and the possibility to use PKCE
+	// including state handling with secure cookie and the possibility to use PKCE.
-	http.Handle("/login", rp.AuthURLHandler(state, provider))
+	// Prompts can optionally be set to inform the server of
+	// any messages that need to be prompted back to the user.
+	http.Handle("/login", rp.AuthURLHandler(state, provider, rp.WithPromptURLParam("Welcome back!")))
 
 	// for demonstration purposes the returned userinfo response is written as JSON object onto response
 	marshalUserinfo := func(w http.ResponseWriter, r *http.Request, tokens *oidc.Tokens, state string, rp rp.RelyingParty, info oidc.UserInfo) {

pkg/client/rp/integration_test.go

@@ -75,7 +75,10 @@ func TestRelyingPartySession(t *testing.T) {
 	state := "state-" + strconv.FormatInt(seed.Int63(), 25)
 	capturedW := httptest.NewRecorder()
 	get := httptest.NewRequest("GET", localURL.String(), nil)
-	rp.AuthURLHandler(func() string { return state }, provider)(capturedW, get)
+	rp.AuthURLHandler(func() string { return state }, provider,
+		rp.WithPromptURLParam("Hello, World!", "Goodbye, World!"),
+		rp.WithURLParam("custom", "param"),
+	)(capturedW, get)
 
 	defer func() {
 		if t.Failed() {
@@ -84,6 +87,8 @@ func TestRelyingPartySession(t *testing.T) {
 	}()
 	require.GreaterOrEqual(t, capturedW.Code, 200, "captured response code")
 	require.Less(t, capturedW.Code, 400, "captured response code")
+	require.Contains(t, capturedW.Body.String(), `prompt=Hello%2C+World%21+Goodbye%2C+World%21`)
+	require.Contains(t, capturedW.Body.String(), `custom=param`)
 
 	//nolint:bodyclose
 	resp := capturedW.Result()
@@ -140,7 +145,7 @@ func TestRelyingPartySession(t *testing.T) {
 		email = info.GetEmail()
 		http.Redirect(w, r, targetURL, 302)
 	}
-	rp.CodeExchangeHandler(rp.UserinfoCallback(redirect), provider)(capturedW, get)
+	rp.CodeExchangeHandler(rp.UserinfoCallback(redirect), provider, rp.WithURLParam("custom", "param"))(capturedW, get)
 
 	defer func() {
 		if t.Failed() {
@@ -150,6 +155,7 @@ func TestRelyingPartySession(t *testing.T) {
 	}()
 	require.Less(t, capturedW.Code, 400, "token exchange response code")
 	require.Less(t, capturedW.Code, 400, "token exchange response code")
+	// TODO: how to check the custom header was sent to the server?
 
 	//nolint:bodyclose
 	resp = capturedW.Result()
@@ -193,6 +199,13 @@ func TestRelyingPartySession(t *testing.T) {
 		_, err = rp.RefreshAccessToken(provider, newTokens.RefreshToken, "", "")
 		assert.Errorf(t, err, "refresh with replacement")
 	}
+
+	t.Run("WithPrompt", func(t *testing.T) {
+		opts := rp.WithPrompt("foo", "bar")()
+		url := provider.OAuthConfig().AuthCodeURL("some", opts...)
+
+		require.Contains(t, url, "prompt=foo+bar")
+	})
 }
 
 type deferredHandler struct {

pkg/client/rp/relying_party.go

@@ -333,10 +333,15 @@ func AuthURL(state string, rp RelyingParty, opts ...AuthURLOpt) string {
 }
 
 // AuthURLHandler extends the `AuthURL` method with a http redirect handler
-// including handling setting cookie for secure `state` transfer
+// including handling setting cookie for secure `state` transfer.
-func AuthURLHandler(stateFn func() string, rp RelyingParty) http.HandlerFunc {
+// Custom paramaters can optionally be set to the redirect URL.
+func AuthURLHandler(stateFn func() string, rp RelyingParty, urlParam ...URLParamOpt) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		opts := make([]AuthURLOpt, 0)
+		opts := make([]AuthURLOpt, len(urlParam))
+		for i, p := range urlParam {
+			opts[i] = AuthURLOpt(p)
+		}
+
 		state := stateFn()
 		if err := trySetStateCookie(w, state, rp); err != nil {
 			http.Error(w, "failed to create state cookie: "+err.Error(), http.StatusUnauthorized)
@@ -350,6 +355,7 @@ func AuthURLHandler(stateFn func() string, rp RelyingParty) http.HandlerFunc {
 			}
 			opts = append(opts, WithCodeChallenge(codeChallenge))
 		}
+
 		http.Redirect(w, r, AuthURL(state, rp, opts...), http.StatusFound)
 	}
 }
@@ -398,8 +404,9 @@ type CodeExchangeCallback func(w http.ResponseWriter, r *http.Request, tokens *o
 
 // CodeExchangeHandler extends the `CodeExchange` method with a http handler
 // including cookie handling for secure `state` transfer
-// and optional PKCE code verifier checking
+// and optional PKCE code verifier checking.
-func CodeExchangeHandler(callback CodeExchangeCallback, rp RelyingParty) http.HandlerFunc {
+// Custom paramaters can optionally be set to the token URL.
+func CodeExchangeHandler(callback CodeExchangeCallback, rp RelyingParty, urlParam ...URLParamOpt) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
 		state, err := tryReadStateCookie(w, r, rp)
 		if err != nil {
@@ -411,7 +418,11 @@ func CodeExchangeHandler(callback CodeExchangeCallback, rp RelyingParty) http.Ha
 			rp.ErrorHandler()(w, r, params.Get("error"), params.Get("error_description"), state)
 			return
 		}
-		codeOpts := make([]CodeExchangeOpt, 0)
+		codeOpts := make([]CodeExchangeOpt, len(urlParam))
+		for i, p := range urlParam {
+			codeOpts[i] = CodeExchangeOpt(p)
+		}
+
 		if rp.IsPKCE() {
 			codeVerifier, err := rp.CookieHandler().CheckCookie(r, pkceCode)
 			if err != nil {
@@ -517,6 +528,37 @@ func GetEndpoints(discoveryConfig *oidc.DiscoveryConfiguration) Endpoints {
 	}
 }
 
+// withURLParam sets custom url paramaters.
+// This is the generalized, unexported, function used by both
+// URLParamOpt and AuthURLOpt.
+func withURLParam(key, value string) func() []oauth2.AuthCodeOption {
+	return func() []oauth2.AuthCodeOption {
+		return []oauth2.AuthCodeOption{
+			oauth2.SetAuthURLParam(key, value),
+		}
+	}
+}
+
+// withPrompt sets the `prompt` params in the auth request
+// This is the generalized, unexported, function used by both
+// URLParamOpt and AuthURLOpt.
+func withPrompt(prompt ...string) func() []oauth2.AuthCodeOption {
+	return withURLParam("prompt", oidc.SpaceDelimitedArray(prompt).Encode())
+}
+
+type URLParamOpt func() []oauth2.AuthCodeOption
+
+// WithURLParam allows setting custom key-vale pairs
+// to an OAuth2 URL.
+func WithURLParam(key, value string) URLParamOpt {
+	return withURLParam(key, value)
+}
+
+// WithPromptURLParam sets the `prompt` parameter in a URL.
+func WithPromptURLParam(prompt ...string) URLParamOpt {
+	return withPrompt(prompt...)
+}
+
 type AuthURLOpt func() []oauth2.AuthCodeOption
 
 // WithCodeChallenge sets the `code_challenge` params in the auth request
@@ -531,11 +573,7 @@ func WithCodeChallenge(codeChallenge string) AuthURLOpt {
 
 // WithPrompt sets the `prompt` params in the auth request
 func WithPrompt(prompt ...string) AuthURLOpt {
-	return func() []oauth2.AuthCodeOption {
+	return withPrompt(prompt...)
-		return []oauth2.AuthCodeOption{
-			oauth2.SetAuthURLParam("prompt", oidc.SpaceDelimitedArray(prompt).Encode()),
-		}
-	}
 }
 
 type CodeExchangeOpt func() []oauth2.AuthCodeOption