1 files changed, 223 insertions, 0 deletions
diff --git a/services/auth/sspi.go b/services/auth/sspi.go
new file mode 100644
index 0000000..64a127e
--- /dev/null
+++ b/services/auth/sspi.go
@@ -0,0 +1,223 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import (
+	"context"
+	"errors"
+	"net/http"
+	"strings"
+	"sync"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/base"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/web/middleware"
+	"code.gitea.io/gitea/services/auth/source/sspi"
+	gitea_context "code.gitea.io/gitea/services/context"
+
+	gouuid "github.com/google/uuid"
+)
+
+const (
+	tplSignIn base.TplName = "user/auth/signin"
+)
+
+type SSPIAuth interface {
+	AppendAuthenticateHeader(w http.ResponseWriter, data string)
+	Authenticate(r *http.Request, w http.ResponseWriter) (userInfo *SSPIUserInfo, outToken string, err error)
+}
+
+var (
+	sspiAuth        SSPIAuth // a global instance of the websspi authenticator to avoid acquiring the server credential handle on every request
+	sspiAuthOnce    sync.Once
+	sspiAuthErrInit error
+
+	// Ensure the struct implements the interface.
+	_ Method = &SSPI{}
+)
+
+// SSPI implements the SingleSignOn interface and authenticates requests
+// via the built-in SSPI module in Windows for SPNEGO authentication.
+// The SSPI plugin is expected to be executed last, as it returns 401 status code if negotiation
+// fails (or if negotiation should continue), which would prevent other authentication methods
+// to execute at all.
+type SSPI struct{}
+
+// Name represents the name of auth method
+func (s *SSPI) Name() string {
+	return "sspi"
+}
+
+// Verify uses SSPI (Windows implementation of SPNEGO) to authenticate the request.
+// If authentication is successful, returns the corresponding user object.
+// If negotiation should continue or authentication fails, immediately returns a 401 HTTP
+// response code, as required by the SPNEGO protocol.
+func (s *SSPI) Verify(req *http.Request, w http.ResponseWriter, store DataStore, sess SessionStore) (*user_model.User, error) {
+	sspiAuthOnce.Do(func() { sspiAuthErrInit = sspiAuthInit() })
+	if sspiAuthErrInit != nil {
+		return nil, sspiAuthErrInit
+	}
+	if !s.shouldAuthenticate(req) {
+		return nil, nil
+	}
+
+	cfg, err := s.getConfig(req.Context())
+	if err != nil {
+		log.Error("could not get SSPI config: %v", err)
+		return nil, err
+	}
+
+	log.Trace("SSPI Authorization: Attempting to authenticate")
+	userInfo, outToken, err := sspiAuth.Authenticate(req, w)
+	if err != nil {
+		log.Warn("Authentication failed with error: %v\n", err)
+		sspiAuth.AppendAuthenticateHeader(w, outToken)
+
+		// Include the user login page in the 401 response to allow the user
+		// to login with another authentication method if SSPI authentication
+		// fails
+		store.GetData()["Flash"] = map[string]string{
+			"ErrorMsg": err.Error(),
+		}
+		store.GetData()["EnableOpenIDSignIn"] = setting.Service.EnableOpenIDSignIn
+		store.GetData()["EnableSSPI"] = true
+		// in this case, the Verify function is called in Gitea's web context
+		// FIXME: it doesn't look good to render the page here, why not redirect?
+		gitea_context.GetWebContext(req).HTML(http.StatusUnauthorized, tplSignIn)
+		return nil, err
+	}
+	if outToken != "" {
+		sspiAuth.AppendAuthenticateHeader(w, outToken)
+	}
+
+	username := sanitizeUsername(userInfo.Username, cfg)
+	if len(username) == 0 {
+		return nil, nil
+	}
+	log.Info("Authenticated as %s\n", username)
+
+	user, err := user_model.GetUserByName(req.Context(), username)
+	if err != nil {
+		if !user_model.IsErrUserNotExist(err) {
+			log.Error("GetUserByName: %v", err)
+			return nil, err
+		}
+		if !cfg.AutoCreateUsers {
+			log.Error("User '%s' not found", username)
+			return nil, nil
+		}
+		user, err = s.newUser(req.Context(), username, cfg)
+		if err != nil {
+			log.Error("CreateUser: %v", err)
+			return nil, err
+		}
+	}
+
+	// Make sure requests to API paths and PWA resources do not create a new session
+	if !middleware.IsAPIPath(req) && !isAttachmentDownload(req) {
+		handleSignIn(w, req, sess, user)
+	}
+
+	log.Trace("SSPI Authorization: Logged in user %-v", user)
+	return user, nil
+}
+
+// getConfig retrieves the SSPI configuration from login sources
+func (s *SSPI) getConfig(ctx context.Context) (*sspi.Source, error) {
+	sources, err := db.Find[auth.Source](ctx, auth.FindSourcesOptions{
+		IsActive:  optional.Some(true),
+		LoginType: auth.SSPI,
+	})
+	if err != nil {
+		return nil, err
+	}
+	if len(sources) == 0 {
+		return nil, errors.New("no active login sources of type SSPI found")
+	}
+	if len(sources) > 1 {
+		return nil, errors.New("more than one active login source of type SSPI found")
+	}
+	return sources[0].Cfg.(*sspi.Source), nil
+}
+
+func (s *SSPI) shouldAuthenticate(req *http.Request) (shouldAuth bool) {
+	shouldAuth = false
+	path := strings.TrimSuffix(req.URL.Path, "/")
+	if path == "/user/login" {
+		if req.FormValue("user_name") != "" && req.FormValue("password") != "" {
+			shouldAuth = false
+		} else if req.FormValue("auth_with_sspi") == "1" {
+			shouldAuth = true
+		}
+	} else if middleware.IsAPIPath(req) || isAttachmentDownload(req) {
+		shouldAuth = true
+	}
+	return shouldAuth
+}
+
+// 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 (s *SSPI) newUser(ctx context.Context, username string, cfg *sspi.Source) (*user_model.User, error) {
+	email := gouuid.New().String() + "@localhost.localdomain"
+	user := &user_model.User{
+		Name:     username,
+		Email:    email,
+		Language: cfg.DefaultLanguage,
+	}
+	emailNotificationPreference := user_model.EmailNotificationsDisabled
+	overwriteDefault := &user_model.CreateUserOverwriteOptions{
+		IsActive:                     optional.Some(cfg.AutoActivateUsers),
+		KeepEmailPrivate:             optional.Some(true),
+		EmailNotificationsPreference: &emailNotificationPreference,
+	}
+	if err := user_model.CreateUser(ctx, user, overwriteDefault); err != nil {
+		return nil, err
+	}
+
+	return user, nil
+}
+
+// stripDomainNames removes NETBIOS domain name and separator from down-level logon names
+// (eg. "DOMAIN\user" becomes "user"), and removes the UPN suffix (domain name) and separator
+// from UPNs (eg. "user@domain.local" becomes "user")
+func stripDomainNames(username string) string {
+	if strings.Contains(username, "\\") {
+		parts := strings.SplitN(username, "\\", 2)
+		if len(parts) > 1 {
+			username = parts[1]
+		}
+	} else if strings.Contains(username, "@") {
+		parts := strings.Split(username, "@")
+		if len(parts) > 1 {
+			username = parts[0]
+		}
+	}
+	return username
+}
+
+func replaceSeparators(username string, cfg *sspi.Source) string {
+	newSep := cfg.SeparatorReplacement
+	username = strings.ReplaceAll(username, "\\", newSep)
+	username = strings.ReplaceAll(username, "/", newSep)
+	username = strings.ReplaceAll(username, "@", newSep)
+	return username
+}
+
+func sanitizeUsername(username string, cfg *sspi.Source) string {
+	if len(username) == 0 {
+		return ""
+	}
+	if cfg.StripDomainNames {
+		username = stripDomainNames(username)
+	}
+	// Replace separators even if we have already stripped the domain name part,
+	// as the username can contain several separators: eg. "MICROSOFT\useremail@live.com"
+	username = replaceSeparators(username, cfg)
+	return username
+}