1 files changed, 68 insertions, 0 deletions
diff --git a/services/auth/source/oauth2/source_callout.go b/services/auth/source/oauth2/source_callout.go
new file mode 100644
index 0000000..f95a80f
--- /dev/null
+++ b/services/auth/source/oauth2/source_callout.go
@@ -0,0 +1,68 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package oauth2
+
+import (
+	"net/http"
+	"net/url"
+
+	"github.com/markbates/goth"
+	"github.com/markbates/goth/gothic"
+)
+
+// Callout redirects request/response pair to authenticate against the provider
+func (source *Source) Callout(request *http.Request, response http.ResponseWriter, codeChallengeS256 string) error {
+	// not sure if goth is thread safe (?) when using multiple providers
+	request.Header.Set(ProviderHeaderKey, source.authSource.Name)
+
+	var querySuffix string
+	if codeChallengeS256 != "" {
+		querySuffix = "&" + url.Values{
+			"code_challenge_method": []string{"S256"},
+			"code_challenge":        []string{codeChallengeS256},
+		}.Encode()
+	}
+
+	// don't use the default gothic begin handler to prevent issues when some error occurs
+	// normally the gothic library will write some custom stuff to the response instead of our own nice error page
+	// gothic.BeginAuthHandler(response, request)
+
+	gothRWMutex.RLock()
+	defer gothRWMutex.RUnlock()
+
+	url, err := gothic.GetAuthURL(response, request)
+	if err == nil {
+		// hacky way to set the code_challenge, but no better way until
+		// https://github.com/markbates/goth/issues/516 is resolved
+		http.Redirect(response, request, url+querySuffix, http.StatusTemporaryRedirect)
+	}
+	return err
+}
+
+// Callback handles OAuth callback, resolve to a goth user and send back to original url
+// this will trigger a new authentication request, but because we save it in the session we can use that
+func (source *Source) Callback(request *http.Request, response http.ResponseWriter, codeVerifier string) (goth.User, error) {
+	// not sure if goth is thread safe (?) when using multiple providers
+	request.Header.Set(ProviderHeaderKey, source.authSource.Name)
+
+	if codeVerifier != "" {
+		// hacky way to set the code_verifier...
+		// Will be picked up inside CompleteUserAuth: params := req.URL.Query()
+		// https://github.com/markbates/goth/pull/474/files
+		request = request.Clone(request.Context())
+		q := request.URL.Query()
+		q.Add("code_verifier", codeVerifier)
+		request.URL.RawQuery = q.Encode()
+	}
+
+	gothRWMutex.RLock()
+	defer gothRWMutex.RUnlock()
+
+	user, err := gothic.CompleteUserAuth(response, request)
+	if err != nil {
+		return user, err
+	}
+
+	return user, nil
+}