Map OIDC groups to Orgs/Teams (#21441)

Fixes #19555

Test-Instructions:
https://github.com/go-gitea/gitea/pull/21441#issuecomment-1419438000

This PR implements the mapping of user groups provided by OIDC providers
to orgs teams in Gitea. The main part is a refactoring of the existing
LDAP code to make it usable from different providers.

Refactorings:
- Moved the router auth code from module to service because of import
cycles
- Changed some model methods to take a `Context` parameter
- Moved the mapping code from LDAP to a common location

I've tested it with Keycloak but other providers should work too. The
JSON mapping format is the same as for LDAP.


![grafik](https://user-images.githubusercontent.com/1666336/195634392-3fc540fc-b229-4649-99ac-91ae8e19df2d.png)

---------

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

8 files changed, 294 insertions, 246 deletions

diff --git a/services/auth/middleware.go b/services/auth/middleware.go
new file mode 100644
index 0000000000..cccaab2998
--- /dev/null
+++ b/services/auth/middleware.go
@@ -0,0 +1,60 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import (
+	"net/http"
+
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/web/middleware"
+)
+
+// Auth is a middleware to authenticate a web user
+func Auth(authMethod Method) func(*context.Context) {
+	return func(ctx *context.Context) {
+		if err := authShared(ctx, authMethod); err != nil {
+			log.Error("Failed to verify user: %v", err)
+			ctx.Error(http.StatusUnauthorized, "Verify")
+			return
+		}
+		if ctx.Doer == nil {
+			// ensure the session uid is deleted
+			_ = ctx.Session.Delete("uid")
+		}
+	}
+}
+
+// APIAuth is a middleware to authenticate an api user
+func APIAuth(authMethod Method) func(*context.APIContext) {
+	return func(ctx *context.APIContext) {
+		if err := authShared(ctx.Context, authMethod); err != nil {
+			ctx.Error(http.StatusUnauthorized, "APIAuth", err)
+		}
+	}
+}
+
+func authShared(ctx *context.Context, authMethod Method) error {
+	var err error
+	ctx.Doer, err = authMethod.Verify(ctx.Req, ctx.Resp, ctx, ctx.Session)
+	if err != nil {
+		return err
+	}
+	if ctx.Doer != nil {
+		if ctx.Locale.Language() != ctx.Doer.Language {
+			ctx.Locale = middleware.Locale(ctx.Resp, ctx.Req)
+		}
+		ctx.IsBasicAuth = ctx.Data["AuthedMethod"].(string) == BasicMethodName
+		ctx.IsSigned = true
+		ctx.Data["IsSigned"] = ctx.IsSigned
+		ctx.Data["SignedUser"] = ctx.Doer
+		ctx.Data["SignedUserID"] = ctx.Doer.ID
+		ctx.Data["SignedUserName"] = ctx.Doer.Name
+		ctx.Data["IsAdmin"] = ctx.Doer.IsAdmin
+	} else {
+		ctx.Data["SignedUserID"] = int64(0)
+		ctx.Data["SignedUserName"] = ""
+	}
+	return nil
+}
diff --git a/services/auth/source/ldap/source_authenticate.go b/services/auth/source/ldap/source_authenticate.go
index 321cf5540d..fba8da7934 100644
--- a/services/auth/source/ldap/source_authenticate.go
+++ b/services/auth/source/ldap/source_authenticate.go
@@ -10,9 +10,10 @@ import (
 	asymkey_model "code.gitea.io/gitea/models/asymkey"
 	"code.gitea.io/gitea/models/auth"
 	"code.gitea.io/gitea/models/db"
-	"code.gitea.io/gitea/models/organization"
 	user_model "code.gitea.io/gitea/models/user"
+	auth_module "code.gitea.io/gitea/modules/auth"
 	"code.gitea.io/gitea/modules/util"
+	source_service "code.gitea.io/gitea/services/auth/source"
 	"code.gitea.io/gitea/services/mailer"
 	user_service "code.gitea.io/gitea/services/user"
 )
@@ -64,61 +65,66 @@ func (source *Source) Authenticate(user *user_model.User, userName, password str
 	}
 
 	if user != nil {
-		if source.GroupsEnabled && (source.GroupTeamMap != "" || source.GroupTeamMapRemoval) {
-			orgCache := make(map[string]*organization.Organization)
-			teamCache := make(map[string]*organization.Team)
-			source.SyncLdapGroupsToTeams(user, sr.LdapTeamAdd, sr.LdapTeamRemove, orgCache, teamCache)
-		}
 		if isAttributeSSHPublicKeySet && asymkey_model.SynchronizePublicKeys(user, source.authSource, sr.SSHPublicKey) {
-			return user, asymkey_model.RewriteAllPublicKeys()
+			if err := asymkey_model.RewriteAllPublicKeys(); err != nil {
+				return user, err
+			}
+		}
+	} else {
+		// Fallback.
+		if len(sr.Username) == 0 {
+			sr.Username = userName
 		}
-		return user, nil
-	}
-
-	// Fallback.
-	if len(sr.Username) == 0 {
-		sr.Username = userName
-	}
 
-	if len(sr.Mail) == 0 {
-		sr.Mail = fmt.Sprintf("%s@localhost", sr.Username)
-	}
+		if len(sr.Mail) == 0 {
+			sr.Mail = fmt.Sprintf("%s@localhost", sr.Username)
+		}
 
-	user = &user_model.User{
-		LowerName:   strings.ToLower(sr.Username),
-		Name:        sr.Username,
-		FullName:    composeFullName(sr.Name, sr.Surname, sr.Username),
-		Email:       sr.Mail,
-		LoginType:   source.authSource.Type,
-		LoginSource: source.authSource.ID,
-		LoginName:   userName,
-		IsAdmin:     sr.IsAdmin,
-	}
-	overwriteDefault := &user_model.CreateUserOverwriteOptions{
-		IsRestricted: util.OptionalBoolOf(sr.IsRestricted),
-		IsActive:     util.OptionalBoolTrue,
-	}
+		user = &user_model.User{
+			LowerName:   strings.ToLower(sr.Username),
+			Name:        sr.Username,
+			FullName:    composeFullName(sr.Name, sr.Surname, sr.Username),
+			Email:       sr.Mail,
+			LoginType:   source.authSource.Type,
+			LoginSource: source.authSource.ID,
+			LoginName:   userName,
+			IsAdmin:     sr.IsAdmin,
+		}
+		overwriteDefault := &user_model.CreateUserOverwriteOptions{
+			IsRestricted: util.OptionalBoolOf(sr.IsRestricted),
+			IsActive:     util.OptionalBoolTrue,
+		}
 
-	err := user_model.CreateUser(user, overwriteDefault)
-	if err != nil {
-		return user, err
-	}
+		err := user_model.CreateUser(user, overwriteDefault)
+		if err != nil {
+			return user, err
+		}
 
-	mailer.SendRegisterNotifyMail(user)
+		mailer.SendRegisterNotifyMail(user)
 
-	if isAttributeSSHPublicKeySet && asymkey_model.AddPublicKeysBySource(user, source.authSource, sr.SSHPublicKey) {
-		err = asymkey_model.RewriteAllPublicKeys()
-	}
-	if err == nil && len(source.AttributeAvatar) > 0 {
-		_ = user_service.UploadAvatar(user, sr.Avatar)
+		if isAttributeSSHPublicKeySet && asymkey_model.AddPublicKeysBySource(user, source.authSource, sr.SSHPublicKey) {
+			if err := asymkey_model.RewriteAllPublicKeys(); err != nil {
+				return user, err
+			}
+		}
+		if len(source.AttributeAvatar) > 0 {
+			if err := user_service.UploadAvatar(user, sr.Avatar); err != nil {
+				return user, err
+			}
+		}
 	}
+
 	if source.GroupsEnabled && (source.GroupTeamMap != "" || source.GroupTeamMapRemoval) {
-		orgCache := make(map[string]*organization.Organization)
-		teamCache := make(map[string]*organization.Team)
-		source.SyncLdapGroupsToTeams(user, sr.LdapTeamAdd, sr.LdapTeamRemove, orgCache, teamCache)
+		groupTeamMapping, err := auth_module.UnmarshalGroupTeamMapping(source.GroupTeamMap)
+		if err != nil {
+			return user, err
+		}
+		if err := source_service.SyncGroupsToTeams(db.DefaultContext, user, sr.Groups, groupTeamMapping, source.GroupTeamMapRemoval); err != nil {
+			return user, err
+		}
 	}
 
-	return user, err
+	return user, nil
 }
 
 // IsSkipLocalTwoFA returns if this source should skip local 2fa for password authentication
diff --git a/services/auth/source/ldap/source_group_sync.go b/services/auth/source/ldap/source_group_sync.go
deleted file mode 100644
index 95a6084922..0000000000
--- a/services/auth/source/ldap/source_group_sync.go
+++ /dev/null
@@ -1,94 +0,0 @@
-// Copyright 2021 The Gitea Authors. All rights reserved.
-// SPDX-License-Identifier: MIT
-
-package ldap
-
-import (
-	"code.gitea.io/gitea/models"
-	"code.gitea.io/gitea/models/db"
-	"code.gitea.io/gitea/models/organization"
-	user_model "code.gitea.io/gitea/models/user"
-	"code.gitea.io/gitea/modules/log"
-)
-
-// SyncLdapGroupsToTeams maps LDAP groups to organization and team memberships
-func (source *Source) SyncLdapGroupsToTeams(user *user_model.User, ldapTeamAdd, ldapTeamRemove map[string][]string, orgCache map[string]*organization.Organization, teamCache map[string]*organization.Team) {
-	var err error
-	if source.GroupsEnabled && source.GroupTeamMapRemoval {
-		// when the user is not a member of configs LDAP group, remove mapped organizations/teams memberships
-		removeMappedMemberships(user, ldapTeamRemove, orgCache, teamCache)
-	}
-	for orgName, teamNames := range ldapTeamAdd {
-		org, ok := orgCache[orgName]
-		if !ok {
-			org, err = organization.GetOrgByName(orgName)
-			if err != nil {
-				// organization must be created before LDAP group sync
-				log.Warn("LDAP group sync: Could not find organisation %s: %v", orgName, err)
-				continue
-			}
-			orgCache[orgName] = org
-		}
-
-		for _, teamName := range teamNames {
-			team, ok := teamCache[orgName+teamName]
-			if !ok {
-				team, err = org.GetTeam(teamName)
-				if err != nil {
-					// team must be created before LDAP group sync
-					log.Warn("LDAP group sync: Could not find team %s: %v", teamName, err)
-					continue
-				}
-				teamCache[orgName+teamName] = team
-			}
-			if isMember, err := organization.IsTeamMember(db.DefaultContext, org.ID, team.ID, user.ID); !isMember && err == nil {
-				log.Trace("LDAP group sync: adding user [%s] to team [%s]", user.Name, org.Name)
-			} else {
-				continue
-			}
-			err := models.AddTeamMember(team, user.ID)
-			if err != nil {
-				log.Error("LDAP group sync: Could not add user to team: %v", err)
-			}
-		}
-	}
-}
-
-// remove membership to organizations/teams if user is not member of corresponding LDAP group
-// e.g. lets assume user is member of LDAP group "x", but LDAP group team map contains LDAP groups "x" and "y"
-// then users membership gets removed for all organizations/teams mapped by LDAP group "y"
-func removeMappedMemberships(user *user_model.User, ldapTeamRemove map[string][]string, orgCache map[string]*organization.Organization, teamCache map[string]*organization.Team) {
-	var err error
-	for orgName, teamNames := range ldapTeamRemove {
-		org, ok := orgCache[orgName]
-		if !ok {
-			org, err = organization.GetOrgByName(orgName)
-			if err != nil {
-				// organization must be created before LDAP group sync
-				log.Warn("LDAP group sync: Could not find organisation %s: %v", orgName, err)
-				continue
-			}
-			orgCache[orgName] = org
-		}
-		for _, teamName := range teamNames {
-			team, ok := teamCache[orgName+teamName]
-			if !ok {
-				team, err = org.GetTeam(teamName)
-				if err != nil {
-					// team must must be created before LDAP group sync
-					log.Warn("LDAP group sync: Could not find team %s: %v", teamName, err)
-					continue
-				}
-			}
-			if isMember, err := organization.IsTeamMember(db.DefaultContext, org.ID, team.ID, user.ID); isMember && err == nil {
-				log.Trace("LDAP group sync: removing user [%s] from team [%s]", user.Name, org.Name)
-			} else {
-				continue
-			}
-			err = models.RemoveTeamMember(team, user.ID)
-			if err != nil {
-				log.Error("LDAP group sync: Could not remove user from team: %v", err)
-			}
-		}
-	}
-}
diff --git a/services/auth/source/ldap/source_search.go b/services/auth/source/ldap/source_search.go
index 16f13029f9..5a2d25b0c4 100644
--- a/services/auth/source/ldap/source_search.go
+++ b/services/auth/source/ldap/source_search.go
@@ -11,26 +11,24 @@ import (
 	"strconv"
 	"strings"
 
-	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/container"
 	"code.gitea.io/gitea/modules/log"
-	"code.gitea.io/gitea/modules/util"
 
 	"github.com/go-ldap/ldap/v3"
 )
 
 // SearchResult : user data
 type SearchResult struct {
-	Username       string   // Username
-	Name           string   // Name
-	Surname        string   // Surname
-	Mail           string   // E-mail address
-	SSHPublicKey   []string // SSH Public Key
-	IsAdmin        bool     // if user is administrator
-	IsRestricted   bool     // if user is restricted
-	LowerName      string   // LowerName
-	Avatar         []byte
-	LdapTeamAdd    map[string][]string // organizations teams to add
-	LdapTeamRemove map[string][]string // organizations teams to remove
+	Username     string   // Username
+	Name         string   // Name
+	Surname      string   // Surname
+	Mail         string   // E-mail address
+	SSHPublicKey []string // SSH Public Key
+	IsAdmin      bool     // if user is administrator
+	IsRestricted bool     // if user is restricted
+	LowerName    string   // LowerName
+	Avatar       []byte
+	Groups       container.Set[string]
 }
 
 func (source *Source) sanitizedUserQuery(username string) (string, bool) {
@@ -196,9 +194,8 @@ func checkRestricted(l *ldap.Conn, ls *Source, userDN string) bool {
 }
 
 // List all group memberships of a user
-func (source *Source) listLdapGroupMemberships(l *ldap.Conn, uid string, applyGroupFilter bool) []string {
-	var ldapGroups []string
-	var searchFilter string
+func (source *Source) listLdapGroupMemberships(l *ldap.Conn, uid string, applyGroupFilter bool) container.Set[string] {
+	ldapGroups := make(container.Set[string])
 
 	groupFilter, ok := source.sanitizedGroupFilter(source.GroupFilter)
 	if !ok {
@@ -210,12 +207,12 @@ func (source *Source) listLdapGroupMemberships(l *ldap.Conn, uid string, applyGr
 		return ldapGroups
 	}
 
+	var searchFilter string
 	if applyGroupFilter {
 		searchFilter = fmt.Sprintf("(&(%s)(%s=%s))", groupFilter, source.GroupMemberUID, ldap.EscapeFilter(uid))
 	} else {
 		searchFilter = fmt.Sprintf("(%s=%s)", source.GroupMemberUID, ldap.EscapeFilter(uid))
 	}
-
 	result, err := l.Search(ldap.NewSearchRequest(
 		groupDN,
 		ldap.ScopeWholeSubtree,
@@ -237,44 +234,12 @@ func (source *Source) listLdapGroupMemberships(l *ldap.Conn, uid string, applyGr
 			log.Error("LDAP search was successful, but found no DN!")
 			continue
 		}
-		ldapGroups = append(ldapGroups, entry.DN)
+		ldapGroups.Add(entry.DN)
 	}
 
 	return ldapGroups
 }
 
-// parse LDAP groups and return map of ldap groups to organizations teams
-func (source *Source) mapLdapGroupsToTeams() map[string]map[string][]string {
-	ldapGroupsToTeams := make(map[string]map[string][]string)
-	err := json.Unmarshal([]byte(source.GroupTeamMap), &ldapGroupsToTeams)
-	if err != nil {
-		log.Error("Failed to unmarshall LDAP teams map: %v", err)
-		return ldapGroupsToTeams
-	}
-	return ldapGroupsToTeams
-}
-
-// getMappedMemberships : returns the organizations and teams to modify the users membership
-func (source *Source) getMappedMemberships(usersLdapGroups []string, uid string) (map[string][]string, map[string][]string) {
-	// unmarshall LDAP group team map from configs
-	ldapGroupsToTeams := source.mapLdapGroupsToTeams()
-	membershipsToAdd := map[string][]string{}
-	membershipsToRemove := map[string][]string{}
-	for group, memberships := range ldapGroupsToTeams {
-		isUserInGroup := util.SliceContainsString(usersLdapGroups, group)
-		if isUserInGroup {
-			for org, teams := range memberships {
-				membershipsToAdd[org] = teams
-			}
-		} else if !isUserInGroup {
-			for org, teams := range memberships {
-				membershipsToRemove[org] = teams
-			}
-		}
-	}
-	return membershipsToAdd, membershipsToRemove
-}
-
 func (source *Source) getUserAttributeListedInGroup(entry *ldap.Entry) string {
 	if strings.ToLower(source.UserUID) == "dn" {
 		return entry.DN
@@ -399,23 +364,6 @@ func (source *Source) SearchEntry(name, passwd string, directBind bool) *SearchR
 	surname := sr.Entries[0].GetAttributeValue(source.AttributeSurname)
 	mail := sr.Entries[0].GetAttributeValue(source.AttributeMail)
 
-	teamsToAdd := make(map[string][]string)
-	teamsToRemove := make(map[string][]string)
-
-	// Check group membership
-	if source.GroupsEnabled {
-		userAttributeListedInGroup := source.getUserAttributeListedInGroup(sr.Entries[0])
-		usersLdapGroups := source.listLdapGroupMemberships(l, userAttributeListedInGroup, true)
-
-		if source.GroupFilter != "" && len(usersLdapGroups) == 0 {
-			return nil
-		}
-
-		if source.GroupTeamMap != "" || source.GroupTeamMapRemoval {
-			teamsToAdd, teamsToRemove = source.getMappedMemberships(usersLdapGroups, userAttributeListedInGroup)
-		}
-	}
-
 	if isAttributeSSHPublicKeySet {
 		sshPublicKey = sr.Entries[0].GetAttributeValues(source.AttributeSSHPublicKey)
 	}
@@ -431,6 +379,17 @@ func (source *Source) SearchEntry(name, passwd string, directBind bool) *SearchR
 		Avatar = sr.Entries[0].GetRawAttributeValue(source.AttributeAvatar)
 	}
 
+	// Check group membership
+	var usersLdapGroups container.Set[string]
+	if source.GroupsEnabled {
+		userAttributeListedInGroup := source.getUserAttributeListedInGroup(sr.Entries[0])
+		usersLdapGroups = source.listLdapGroupMemberships(l, userAttributeListedInGroup, true)
+
+		if source.GroupFilter != "" && len(usersLdapGroups) == 0 {
+			return nil
+		}
+	}
+
 	if !directBind && source.AttributesInBind {
 		// binds user (checking password) after looking-up attributes in BindDN context
 		err = bindUser(l, userDN, passwd)
@@ -440,17 +399,16 @@ func (source *Source) SearchEntry(name, passwd string, directBind bool) *SearchR
 	}
 
 	return &SearchResult{
-		LowerName:      strings.ToLower(username),
-		Username:       username,
-		Name:           firstname,
-		Surname:        surname,
-		Mail:           mail,
-		SSHPublicKey:   sshPublicKey,
-		IsAdmin:        isAdmin,
-		IsRestricted:   isRestricted,
-		Avatar:         Avatar,
-		LdapTeamAdd:    teamsToAdd,
-		LdapTeamRemove: teamsToRemove,
+		LowerName:    strings.ToLower(username),
+		Username:     username,
+		Name:         firstname,
+		Surname:      surname,
+		Mail:         mail,
+		SSHPublicKey: sshPublicKey,
+		IsAdmin:      isAdmin,
+		IsRestricted: isRestricted,
+		Avatar:       Avatar,
+		Groups:       usersLdapGroups,
 	}
 }
 
@@ -512,33 +470,29 @@ func (source *Source) SearchEntries() ([]*SearchResult, error) {
 	result := make([]*SearchResult, 0, len(sr.Entries))
 
 	for _, v := range sr.Entries {
-		teamsToAdd := make(map[string][]string)
-		teamsToRemove := make(map[string][]string)
-
+		var usersLdapGroups container.Set[string]
 		if source.GroupsEnabled {
 			userAttributeListedInGroup := source.getUserAttributeListedInGroup(v)
 
 			if source.GroupFilter != "" {
-				usersLdapGroups := source.listLdapGroupMemberships(l, userAttributeListedInGroup, true)
+				usersLdapGroups = source.listLdapGroupMemberships(l, userAttributeListedInGroup, true)
 				if len(usersLdapGroups) == 0 {
 					continue
 				}
 			}
 
 			if source.GroupTeamMap != "" || source.GroupTeamMapRemoval {
-				usersLdapGroups := source.listLdapGroupMemberships(l, userAttributeListedInGroup, false)
-				teamsToAdd, teamsToRemove = source.getMappedMemberships(usersLdapGroups, userAttributeListedInGroup)
+				usersLdapGroups = source.listLdapGroupMemberships(l, userAttributeListedInGroup, false)
 			}
 		}
 
 		user := &SearchResult{
-			Username:       v.GetAttributeValue(source.AttributeUsername),
-			Name:           v.GetAttributeValue(source.AttributeName),
-			Surname:        v.GetAttributeValue(source.AttributeSurname),
-			Mail:           v.GetAttributeValue(source.AttributeMail),
-			IsAdmin:        checkAdmin(l, source, v.DN),
-			LdapTeamAdd:    teamsToAdd,
-			LdapTeamRemove: teamsToRemove,
+			Username: v.GetAttributeValue(source.AttributeUsername),
+			Name:     v.GetAttributeValue(source.AttributeName),
+			Surname:  v.GetAttributeValue(source.AttributeSurname),
+			Mail:     v.GetAttributeValue(source.AttributeMail),
+			IsAdmin:  checkAdmin(l, source, v.DN),
+			Groups:   usersLdapGroups,
 		}
 
 		if !user.IsAdmin {
diff --git a/services/auth/source/ldap/source_sync.go b/services/auth/source/ldap/source_sync.go
index 73e8309aca..4571ff6540 100644
--- a/services/auth/source/ldap/source_sync.go
+++ b/services/auth/source/ldap/source_sync.go
@@ -13,8 +13,10 @@ import (
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/models/organization"
 	user_model "code.gitea.io/gitea/models/user"
+	auth_module "code.gitea.io/gitea/modules/auth"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/util"
+	source_service "code.gitea.io/gitea/services/auth/source"
 	user_service "code.gitea.io/gitea/services/user"
 )
 
@@ -65,6 +67,11 @@ func (source *Source) Sync(ctx context.Context, updateExisting bool) error {
 	orgCache := make(map[string]*organization.Organization)
 	teamCache := make(map[string]*organization.Team)
 
+	groupTeamMapping, err := auth_module.UnmarshalGroupTeamMapping(source.GroupTeamMap)
+	if err != nil {
+		return err
+	}
+
 	for _, su := range sr {
 		select {
 		case <-ctx.Done():
@@ -173,7 +180,9 @@ func (source *Source) Sync(ctx context.Context, updateExisting bool) error {
 		}
 		// Synchronize LDAP groups with organization and team memberships
 		if source.GroupsEnabled && (source.GroupTeamMap != "" || source.GroupTeamMapRemoval) {
-			source.SyncLdapGroupsToTeams(usr, su.LdapTeamAdd, su.LdapTeamRemove, orgCache, teamCache)
+			if err := source_service.SyncGroupsToTeamsCached(ctx, usr, su.Groups, groupTeamMapping, source.GroupTeamMapRemoval, orgCache, teamCache); err != nil {
+				log.Error("SyncGroupsToTeamsCached: %v", err)
+			}
 		}
 	}
 
diff --git a/services/auth/source/oauth2/source.go b/services/auth/source/oauth2/source.go
index 0abebc04ec..675005e55a 100644
--- a/services/auth/source/oauth2/source.go
+++ b/services/auth/source/oauth2/source.go
@@ -8,13 +8,6 @@ import (
 	"code.gitea.io/gitea/modules/json"
 )
 
-// ________      _____          __  .__     ________
-// \_____  \    /  _  \  __ ___/  |_|  |__  \_____  \
-// /   |   \  /  /_\  \|  |  \   __\  |  \  /  ____/
-// /    |    \/    |    \  |  /|  | |   Y  \/       \
-// \_______  /\____|__  /____/ |__| |___|  /\_______ \
-//         \/         \/                 \/         \/
-
 // Source holds configuration for the OAuth2 login source.
 type Source struct {
 	Provider                      string
@@ -24,13 +17,15 @@ type Source struct {
 	CustomURLMapping              *CustomURLMapping
 	IconURL                       string
 
-	Scopes             []string
-	RequiredClaimName  string
-	RequiredClaimValue string
-	GroupClaimName     string
-	AdminGroup         string
-	RestrictedGroup    string
-	SkipLocalTwoFA     bool `json:",omitempty"`
+	Scopes              []string
+	RequiredClaimName   string
+	RequiredClaimValue  string
+	GroupClaimName      string
+	AdminGroup          string
+	GroupTeamMap        string
+	GroupTeamMapRemoval bool
+	RestrictedGroup     string
+	SkipLocalTwoFA      bool `json:",omitempty"`
 
 	// reference to the authSource
 	authSource *auth.Source
diff --git a/services/auth/source/source_group_sync.go b/services/auth/source/source_group_sync.go
new file mode 100644
index 0000000000..20b6095345
--- /dev/null
+++ b/services/auth/source/source_group_sync.go
@@ -0,0 +1,116 @@
+// Copyright 2022 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package source
+
+import (
+	"context"
+	"fmt"
+
+	"code.gitea.io/gitea/models"
+	"code.gitea.io/gitea/models/organization"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/container"
+	"code.gitea.io/gitea/modules/log"
+)
+
+type syncType int
+
+const (
+	syncAdd syncType = iota
+	syncRemove
+)
+
+// SyncGroupsToTeams maps authentication source groups to organization and team memberships
+func SyncGroupsToTeams(ctx context.Context, user *user_model.User, sourceUserGroups container.Set[string], sourceGroupTeamMapping map[string]map[string][]string, performRemoval bool) error {
+	orgCache := make(map[string]*organization.Organization)
+	teamCache := make(map[string]*organization.Team)
+	return SyncGroupsToTeamsCached(ctx, user, sourceUserGroups, sourceGroupTeamMapping, performRemoval, orgCache, teamCache)
+}
+
+// SyncGroupsToTeamsCached maps authentication source groups to organization and team memberships
+func SyncGroupsToTeamsCached(ctx context.Context, user *user_model.User, sourceUserGroups container.Set[string], sourceGroupTeamMapping map[string]map[string][]string, performRemoval bool, orgCache map[string]*organization.Organization, teamCache map[string]*organization.Team) error {
+	membershipsToAdd, membershipsToRemove := resolveMappedMemberships(sourceUserGroups, sourceGroupTeamMapping)
+
+	if performRemoval {
+		if err := syncGroupsToTeamsCached(ctx, user, membershipsToRemove, syncRemove, orgCache, teamCache); err != nil {
+			return fmt.Errorf("could not sync[remove] user groups: %w", err)
+		}
+	}
+
+	if err := syncGroupsToTeamsCached(ctx, user, membershipsToAdd, syncAdd, orgCache, teamCache); err != nil {
+		return fmt.Errorf("could not sync[add] user groups: %w", err)
+	}
+
+	return nil
+}
+
+func resolveMappedMemberships(sourceUserGroups container.Set[string], sourceGroupTeamMapping map[string]map[string][]string) (map[string][]string, map[string][]string) {
+	membershipsToAdd := map[string][]string{}
+	membershipsToRemove := map[string][]string{}
+	for group, memberships := range sourceGroupTeamMapping {
+		isUserInGroup := sourceUserGroups.Contains(group)
+		if isUserInGroup {
+			for org, teams := range memberships {
+				membershipsToAdd[org] = teams
+			}
+		} else {
+			for org, teams := range memberships {
+				membershipsToRemove[org] = teams
+			}
+		}
+	}
+	return membershipsToAdd, membershipsToRemove
+}
+
+func syncGroupsToTeamsCached(ctx context.Context, user *user_model.User, orgTeamMap map[string][]string, action syncType, orgCache map[string]*organization.Organization, teamCache map[string]*organization.Team) error {
+	for orgName, teamNames := range orgTeamMap {
+		var err error
+		org, ok := orgCache[orgName]
+		if !ok {
+			org, err = organization.GetOrgByName(ctx, orgName)
+			if err != nil {
+				if organization.IsErrOrgNotExist(err) {
+					// organization must be created before group sync
+					log.Warn("group sync: Could not find organisation %s: %v", orgName, err)
+					continue
+				}
+				return err
+			}
+			orgCache[orgName] = org
+		}
+		for _, teamName := range teamNames {
+			team, ok := teamCache[orgName+teamName]
+			if !ok {
+				team, err = org.GetTeam(ctx, teamName)
+				if err != nil {
+					if organization.IsErrTeamNotExist(err) {
+						// team must be created before group sync
+						log.Warn("group sync: Could not find team %s: %v", teamName, err)
+						continue
+					}
+					return err
+				}
+				teamCache[orgName+teamName] = team
+			}
+
+			isMember, err := organization.IsTeamMember(ctx, org.ID, team.ID, user.ID)
+			if err != nil {
+				return err
+			}
+
+			if action == syncAdd && !isMember {
+				if err := models.AddTeamMember(team, user.ID); err != nil {
+					log.Error("group sync: Could not add user to team: %v", err)
+					return err
+				}
+			} else if action == syncRemove && isMember {
+				if err := models.RemoveTeamMember(team, user.ID); err != nil {
+					log.Error("group sync: Could not remove user from team: %v", err)
+					return err
+				}
+			}
+		}
+	}
+	return nil
+}
diff --git a/services/forms/auth_form.go b/services/forms/auth_form.go
index 0cede07f95..5625aa1e2e 100644
--- a/services/forms/auth_form.go
+++ b/services/forms/auth_form.go
@@ -72,13 +72,15 @@ type AuthenticationForm struct {
 	Oauth2GroupClaimName          string
 	Oauth2AdminGroup              string
 	Oauth2RestrictedGroup         string
+	Oauth2GroupTeamMap            string `binding:"ValidGroupTeamMap"`
+	Oauth2GroupTeamMapRemoval     bool
 	SkipLocalTwoFA                bool
 	SSPIAutoCreateUsers           bool
 	SSPIAutoActivateUsers         bool
 	SSPIStripDomainNames          bool
 	SSPISeparatorReplacement      string `binding:"AlphaDashDot;MaxSize(5)"`
 	SSPIDefaultLanguage           string
-	GroupTeamMap                  string
+	GroupTeamMap                  string `binding:"ValidGroupTeamMap"`
 	GroupTeamMapRemoval           bool
 }