Add sso.Group, context.Auth, context.APIAuth to allow auth special routes (#16086)

* Add sso.Group, context.Auth, context.APIAuth to allow auth special routes

* Remove unnecessary check

* Rename sso -> auth

* remove unused method of Auth interface

services/auth/reverseproxy.go

@@ -0,0 +1,125 @@
+// Copyright 2014 The Gogs Authors. All rights reserved.
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package auth
+
+import (
+	"net/http"
+	"strings"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/web/middleware"
+
+	gouuid "github.com/google/uuid"
+)
+
+// Ensure the struct implements the interface.
+var (
+	_ Auth = &ReverseProxy{}
+)
+
+// ReverseProxy implements the Auth interface, but actually relies on
+// a reverse proxy for authentication of users.
+// On successful authentication the proxy is expected to populate the username in the
+// "setting.ReverseProxyAuthUser" header. Optionally it can also populate the email of the
+// user in the "setting.ReverseProxyAuthEmail" header.
+type ReverseProxy struct {
+}
+
+// getUserName extracts the username from the "setting.ReverseProxyAuthUser" header
+func (r *ReverseProxy) getUserName(req *http.Request) string {
+	webAuthUser := strings.TrimSpace(req.Header.Get(setting.ReverseProxyAuthUser))
+	if len(webAuthUser) == 0 {
+		return ""
+	}
+	return webAuthUser
+}
+
+// Name represents the name of auth method
+func (r *ReverseProxy) Name() string {
+	return "reverse_proxy"
+}
+
+// Init does nothing as the ReverseProxy implementation does not need initialization
+func (r *ReverseProxy) Init() error {
+	return nil
+}
+
+// Free does nothing as the ReverseProxy implementation does not have to release resources
+func (r *ReverseProxy) Free() error {
+	return nil
+}
+
+// Verify extracts the username from the "setting.ReverseProxyAuthUser" header
+// of the request and returns the corresponding user object for that name.
+// Verification of header data is not performed as it should have already been done by
+// the revese proxy.
+// If a username is available in the "setting.ReverseProxyAuthUser" header an existing
+// user object is returned (populated with username or email found in header).
+// Returns nil if header is empty.
+func (r *ReverseProxy) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) *models.User {
+	username := r.getUserName(req)
+	if len(username) == 0 {
+		return nil
+	}
+	log.Trace("ReverseProxy Authorization: Found username: %s", username)
+
+	user, err := models.GetUserByName(username)
+	if err != nil {
+		if !models.IsErrUserNotExist(err) || !r.isAutoRegisterAllowed() {
+			log.Error("GetUserByName: %v", err)
+			return nil
+		}
+		user = r.newUser(req)
+	}
+
+	// Make sure requests to API paths, attachment downloads, git and LFS do not create a new session
+	if !middleware.IsAPIPath(req) && !isAttachmentDownload(req) && !isGitRawOrLFSPath(req) {
+		if sess != nil && (sess.Get("uid") == nil || sess.Get("uid").(int64) != user.ID) {
+			handleSignIn(w, req, sess, user)
+		}
+	}
+	store.GetData()["IsReverseProxy"] = true
+
+	log.Trace("ReverseProxy Authorization: Logged in user %-v", user)
+	return user
+}
+
+// isAutoRegisterAllowed checks if EnableReverseProxyAutoRegister setting is true
+func (r *ReverseProxy) isAutoRegisterAllowed() bool {
+	return setting.Service.EnableReverseProxyAutoRegister
+}
+
+// newUser creates a new user object for the purpose of automatic registration
+// and populates its name and email with the information present in request headers.
+func (r *ReverseProxy) newUser(req *http.Request) *models.User {
+	username := r.getUserName(req)
+	if len(username) == 0 {
+		return nil
+	}
+
+	email := gouuid.New().String() + "@localhost"
+	if setting.Service.EnableReverseProxyEmail {
+		webAuthEmail := req.Header.Get(setting.ReverseProxyAuthEmail)
+		if len(webAuthEmail) > 0 {
+			email = webAuthEmail
+		}
+	}
+
+	user := &models.User{
+		Name:     username,
+		Email:    email,
+		IsActive: true,
+	}
+	if err := models.CreateUser(user); err != nil {
+		// FIXME: should I create a system notice?
+		log.Error("CreateUser: %v", err)
+		return nil
+	}
+
+	return user
+}