Oidc (#109)

* add oidc config

* inching forward with oidc idp

* lil webfingy fix

* bit more progress

* further oidc

* oidc now working

* document dex config

* replace broken images

* add additional credits

* tiny doc update

* update

* add oidc config

* inching forward with oidc idp

* bit more progress

* further oidc

* oidc now working

* document dex config

* replace broken images

* add additional credits

* tiny doc update

* update

* document

* docs + comments

internal/oidc/handlecallback.go

@@ -0,0 +1,65 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package oidc
+
+import (
+	"context"
+	"errors"
+	"fmt"
+)
+
+func (i *idp) HandleCallback(ctx context.Context, code string) (*Claims, error) {
+	l := i.log.WithField("func", "HandleCallback")
+	if code == "" {
+		return nil, errors.New("code was empty string")
+	}
+
+	l.Debug("exchanging code for oauth2token")
+	oauth2Token, err := i.oauth2Config.Exchange(ctx, code)
+	if err != nil {
+		return nil, fmt.Errorf("error exchanging code for oauth2token: %s", err)
+	}
+
+	l.Debug("extracting id_token")
+	rawIDToken, ok := oauth2Token.Extra("id_token").(string)
+	if !ok {
+		return nil, errors.New("no id_token in oauth2token")
+	}
+	l.Debugf("raw id token: %s", rawIDToken)
+
+	// Parse and verify ID Token payload.
+	l.Debug("verifying id_token")
+	idTokenVerifier := i.provider.Verifier(i.oidcConf)
+	idToken, err := idTokenVerifier.Verify(ctx, rawIDToken)
+	if err != nil {
+		return nil, fmt.Errorf("could not verify id token: %s", err)
+	}
+
+	l.Debug("extracting claims from id_token")
+	claims := &Claims{}
+	if err := idToken.Claims(claims); err != nil {
+		return nil, fmt.Errorf("could not parse claims from idToken: %s", err)
+	}
+
+	return claims, nil
+}
+
+func (i *idp) AuthCodeURL(state string) string {
+	return i.oauth2Config.AuthCodeURL(state)
+}