Support SAML authentication (#25165)

Closes https://github.com/go-gitea/gitea/issues/5512 This PR adds basic SAML support - Adds SAML 2.0 as an auth source - Adds SAML configuration documentation - Adds integration test: - Use bare-bones SAML IdP to test protocol flow and test account is linked successfully (only runs on Postgres by default) - Adds documentation for configuring and running SAML integration test locally Future PRs: - Support group mapping - Support auto-registration (account linking) Co-Authored-By: @jackHay22 --------- Co-authored-by: jackHay22 <jack@allspice.io> Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com> Co-authored-by: KN4CK3R <admin@oldschoolhack.me> Co-authored-by: wxiaoguang <wxiaoguang@gmail.com> Co-authored-by: Jason Song <i@wolfogre.com> Co-authored-by: morphelinho <morphelinho@users.noreply.github.com> Co-authored-by: Zettat123 <zettat123@gmail.com> Co-authored-by: Yarden Shoham <git@yardenshoham.com> Co-authored-by: 6543 <6543@obermui.de> Co-authored-by: silverwind <me@silverwind.io>
2024-02-22 19:08:17 -05:00 · 2024-02-22 19:08:17 -05:00 · 5bb8d1924d
parent c4b0cb4d0d
commit 5bb8d1924d
37 changed files with 1440 additions and 69 deletions
--- a/.github/workflows/pull-db-tests.yml
+++ b/.github/workflows/pull-db-tests.yml
@ -37,6 +37,14 @@ jobs:
          MINIO_ROOT_PASSWORD: 12345678
        ports:
          - "9000:9000"
+      simplesaml:
+        image: allspice/simple-saml
+        ports:
+          - "8080:8080"
+        env:
+          SIMPLESAMLPHP_SP_ENTITY_ID: http://localhost:3002/user/saml/test-sp/metadata
+          SIMPLESAMLPHP_SP_ASSERTION_CONSUMER_SERVICE: http://localhost:3002/user/saml/test-sp/acs
+          SIMPLESAMLPHP_SP_SINGLE_LOGOUT_SERVICE: http://localhost:3002/user/saml/test-sp/acs
    steps:
      - uses: actions/checkout@v4
      - uses: actions/setup-go@v5
--- a/assets/go-licenses.json
+++ b/assets/go-licenses.json
--- a/docs/content/usage/authentication.en-us.md
+++ b/docs/content/usage/authentication.en-us.md
@ -349,3 +349,72 @@ If set `ENABLE_REVERSE_PROXY_FULL_NAME=true`, a user full name expected in `X-WE
 You can also limit the reverse proxy's IP address range with `REVERSE_PROXY_TRUSTED_PROXIES` which default value is `127.0.0.0/8,::1/128`. By `REVERSE_PROXY_LIMIT`, you can limit trusted proxies level.

 Notice: Reverse Proxy Auth doesn't support the API. You still need an access token or basic auth to make API requests.
+
+## SAML
+
+### Configuring Gitea as a SAML 2.0 Service Provider
+
+- Navigate to `Site Administration > Identity & Access > Authentication Sources`.
+- Click the `Add Authentication Source` button.
+- Select `SAML` as the authentication type.
+
+#### Features Not Yet Supported
+
+Currently, auto-registration is not supported for SAML. During the external account linking process the user will be prompted to set a username and email address or link to an existing account.
+
+SAML group mapping is not supported.
+
+#### Settings
+
+- `Authentication Name` **(required)**
+
+  - The name of this authentication source (appears in the Gitea ACS and metadata URLs)
+
+- `SAML NameID Format` **(required)**
+
+  - This specifies how Identity Provider (IdP) users are mapped to Gitea users. This option will be provider specific.
+
+- `Icon URL` (optional)
+
+  - URL of an icon to display on the Sign-In page for this authentication source.
+
+- `[Insecure] Skip Assertion Signature Validation` (optional)
+
+  - This option is not recommended and disables integrity verification of IdP SAML assertions.
+
+- `Identity Provider Metadata URL` (optional if XML set)
+
+  - The URL of the IdP metadata endpoint.
+  - This field must be set if `Identity Provider Metadata XML` is left blank.
+
+- `Identity Provider Metadata XML` (optional if URL set)
+
+  - The XML returned by the IdP metadata endpoint.
+  - This field must be set if `Identity Provider Metadata URL` is left blank.
+
+- `Service Provider Certificate` (optional)
+
+  - X.509-formatted certificate (with `Service Provider Private Key`) used for signing SAML requests.
+  - A certificate will be generated if this field is left blank.
+
+- `Service Provider Private Key` (optional)
+
+  - DSA/RSA private key (with `Service Provider Certificate`) used for signing SAML requests.
+  - A private key will be generated if this field is left blank.
+
+- `Email Assertion Key` (optional)
+
+  - The SAML assertion key used for the IdP user's email (depends on provider configuration).
+
+- `Name Assertion Key` (optional)
+
+  - The SAML assertion key used for the IdP user's nickname (depends on provider configuration).
+
+- `Username Assertion Key` (optional)
+
+  - The SAML assertion key used for the IdP user's username (depends on provider configuration).
+
+### Configuring a SAML 2.0 Identity Provider to use Gitea
+
+- The service provider assertion consumer service url will look like: `http(s)://[mydomain]/user/saml/[Authentication Name]/acs`.
+- The service provider metadata url will look like: `http(s)://[mydomain]/user/saml/[Authentication Name]/metadata`.
--- a/go.mod
+++ b/go.mod
@ -91,6 +91,8 @@ require (
 	github.com/quasoft/websspi v1.1.2
 	github.com/redis/go-redis/v9 v9.4.0
 	github.com/robfig/cron/v3 v3.0.1
+	github.com/russellhaering/gosaml2 v0.9.1
+	github.com/russellhaering/goxmldsig v1.3.0
 	github.com/santhosh-tekuri/jsonschema/v5 v5.3.1
 	github.com/sassoftware/go-rpmutils v0.2.1-0.20240124161140-277b154961dd
 	github.com/sergi/go-diff v1.3.1
@ -143,6 +145,7 @@ require (
 	github.com/anmitsu/go-shlex v0.0.0-20200514113438-38f4b401e2be // indirect
 	github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2 // indirect
 	github.com/aymerick/douceur v0.2.0 // indirect
+	github.com/beevik/etree v1.1.0 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
 	github.com/bits-and-blooms/bitset v1.13.0 // indirect
 	github.com/blevesearch/bleve_index_api v1.1.5 // indirect
@ -216,6 +219,7 @@ require (
 	github.com/imdario/mergo v0.3.16 // indirect
 	github.com/jbenet/go-context v0.0.0-20150711004518-d14ea06fba99 // indirect
 	github.com/jessevdk/go-flags v1.5.0 // indirect
+	github.com/jonboulle/clockwork v0.3.0 // indirect
 	github.com/josharian/intern v1.0.0 // indirect
 	github.com/kevinburke/ssh_config v1.2.0 // indirect
 	github.com/klauspost/pgzip v1.2.6 // indirect
@ -225,6 +229,7 @@ require (
 	github.com/magiconair/properties v1.8.7 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/markbates/going v1.0.3 // indirect
+	github.com/mattermost/xml-roundtrip-validator v0.1.0 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
 	github.com/mattn/go-runewidth v0.0.15 // indirect
 	github.com/mholt/acmez v1.2.0 // indirect
--- a/go.sum
+++ b/go.sum
@ -130,6 +130,8 @@ github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2 h1:DklsrG3d
 github.com/asaskevich/govalidator v0.0.0-20230301143203-a9d515a09cc2/go.mod h1:WaHUgvxTVq04UNunO+XhnAqY/wQc+bxr74GqbsZ/Jqw=
 github.com/aymerick/douceur v0.2.0 h1:Mv+mAeH1Q+n9Fr+oyamOlAkUNPWPlA8PPGR0QAaYuPk=
 github.com/aymerick/douceur v0.2.0/go.mod h1:wlT5vV2O3h55X9m7iVYN0TBM0NH/MmbLnd30/FjWUq4=
+github.com/beevik/etree v1.1.0 h1:T0xke/WvNtMoCqgzPhkX2r4rjY3GDZFi+FjpRZY2Jbs=
+github.com/beevik/etree v1.1.0/go.mod h1:r8Aw8JqVegEf0w2fDnATrX9VpkMcyFeM0FhwO62wh+A=
 github.com/beorn7/perks v1.0.1 h1:VlbKKnNfV8bJzeqoa4cOKqO6bYr3WgKZxO8Z16+hsOM=
 github.com/beorn7/perks v1.0.1/go.mod h1:G2ZrVWU2WbWT9wwq4/hrbKbnv/1ERSJQ0ibhJ6rlkpw=
 github.com/bits-and-blooms/bitset v1.1.10/go.mod h1:w0XsmFg8qg6cmpTtJ0z3pKgjTDBMMnI/+I2syrE6XBE=
@ -566,6 +568,9 @@ github.com/jhillyerd/enmime v1.1.0 h1:ubaIzg68VY7CMCe2YbHe6nkRvU9vujixTkNz3EBvZO
 github.com/jhillyerd/enmime v1.1.0/go.mod h1:FRFuUPCLh8PByQv+8xRcLO9QHqaqTqreYhopv5eyk4I=
 github.com/joho/godotenv v1.5.1 h1:7eLL/+HRGLY0ldzfGMeQkb7vMd0as4CfYvUVzLqw0N0=
 github.com/joho/godotenv v1.5.1/go.mod h1:f4LDr5Voq0i2e/R5DDNOoa2zzDfwtkZa6DnEwAbqwq4=
+github.com/jonboulle/clockwork v0.2.2/go.mod h1:Pkfl5aHPm1nk2H9h0bjmnJD/BcgbGXUBGnn1kMkgxc8=
+github.com/jonboulle/clockwork v0.3.0 h1:9BSCMi8C+0qdApAp4auwX0RkLGUjs956h0EkuQymUhg=
+github.com/jonboulle/clockwork v0.3.0/go.mod h1:Pkfl5aHPm1nk2H9h0bjmnJD/BcgbGXUBGnn1kMkgxc8=
 github.com/josharian/intern v1.0.0 h1:vlS4z54oSdjm0bgjRigI+G1HpF+tI+9rE5LLzOg8HmY=
 github.com/josharian/intern v1.0.0/go.mod h1:5DoeVV0s6jJacbCEi61lwdGj/aVlrQvzHFFd8Hwg//Y=
 github.com/json-iterator/go v1.1.12 h1:PV8peI4a0ysnczrg+LtxykD8LfKY9ML6u2jnxaEnrnM=
@ -634,6 +639,8 @@ github.com/markbates/going v1.0.3 h1:mY45T5TvW+Xz5A6jY7lf4+NLg9D8+iuStIHyR7M8qsE
 github.com/markbates/going v1.0.3/go.mod h1:fQiT6v6yQar9UD6bd/D4Z5Afbk9J6BBVBtLiyY4gp2o=
 github.com/markbates/goth v1.78.0 h1:7VEIFDycJp9deyVv3YraGBPdD0ZYQW93Y3Aw1eVP3BY=
 github.com/markbates/goth v1.78.0/go.mod h1:X6xdNgpapSENS0O35iTBBcMHoJDQDfI9bJl+APCkYMc=
+github.com/mattermost/xml-roundtrip-validator v0.1.0 h1:RXbVD2UAl7A7nOTR4u7E3ILa4IbtvKBHw64LDsmu9hU=
+github.com/mattermost/xml-roundtrip-validator v0.1.0/go.mod h1:qccnGMcpgwcNaBnxqpJpWWUiPNr5H3O8eDgGV9gT5To=
 github.com/mattn/go-colorable v0.1.13 h1:fFA4WZxdEF4tXPZVKMLwD8oUnCTTo08duU7wxecdEvA=
 github.com/mattn/go-colorable v0.1.13/go.mod h1:7S9/ev0klgBDR4GtXTXX8a3vIGJpMovkB8vQcUbaXHg=
 github.com/mattn/go-isatty v0.0.16/go.mod h1:kYGgaQfpe5nmfYZH+SKPsOc2e4SrIfOl2e/yFXSvRLM=
@ -766,12 +773,17 @@ github.com/robfig/cron/v3 v3.0.1 h1:WdRxkvbJztn8LMz/QEvLN5sBU+xKpSqwwUO1Pjr4qDs=
 github.com/robfig/cron/v3 v3.0.1/go.mod h1:eQICP3HwyT7UooqI/z+Ov+PtYAWygg1TEWWzGIFLtro=
 github.com/rogpeppe/go-internal v1.3.0/go.mod h1:M8bDsm7K2OlrFYOpmOWEs/qY81heoFRclV5y23lUDJ4=
 github.com/rogpeppe/go-internal v1.6.1/go.mod h1:xXDCJY+GAPziupqXw64V24skbSoqbTEfhy4qGm1nDQc=
+github.com/rogpeppe/go-internal v1.8.0/go.mod h1:WmiCO8CzOY8rg0OYDC4/i/2WRWAB6poM+XZ2dLUbcbE=
 github.com/rogpeppe/go-internal v1.8.1/go.mod h1:JeRgkft04UBgHMgCIwADu4Pn6Mtm5d4nPKWu0nJ5d+o=
 github.com/rogpeppe/go-internal v1.9.0/go.mod h1:WtVeX8xhTBvf0smdhujwtBcq4Qrzq/fJaraNFVN+nFs=
 github.com/rogpeppe/go-internal v1.12.0 h1:exVL4IDcn6na9z1rAb56Vxr+CgyK3nn3O+epU5NdKM8=
 github.com/rogpeppe/go-internal v1.12.0/go.mod h1:E+RYuTGaKKdloAfM02xzb0FW3Paa99yedzYV+kq4uf4=
 github.com/rs/xid v1.5.0 h1:mKX4bl4iPYJtEIxp6CYiUuLQ/8DYMoz0PUdtGgMFRVc=
 github.com/rs/xid v1.5.0/go.mod h1:trrq9SKmegXys3aeAKXMUTdJsYXVwGY3RLcfgqegfbg=
+github.com/russellhaering/gosaml2 v0.9.1 h1:H/whrl8NuSoxyW46Ww5lKPskm+5K+qYLw9afqJ/Zef0=
+github.com/russellhaering/gosaml2 v0.9.1/go.mod h1:ja+qgbayxm+0mxBRLMSUuX3COqy+sb0RRhIGun/W2kc=
+github.com/russellhaering/goxmldsig v1.3.0 h1:DllIWUgMy0cRUMfGiASiYEa35nsieyD3cigIwLonTPM=
+github.com/russellhaering/goxmldsig v1.3.0/go.mod h1:gM4MDENBQf7M+V824SGfyIUVFWydB7n0KkEubVJl+Tw=
 github.com/russross/blackfriday v1.5.2/go.mod h1:JO/DiYxRf+HjHt06OyowR9PTA263kcR/rfWxYHBV53g=
 github.com/russross/blackfriday/v2 v2.1.0 h1:JIOH55/0cWyOuilr9/qlrm0BSXldqnqwMsf35Ld67mk=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
--- a/models/auth/oauth2.go
+++ b/models/auth/oauth2.go
@ -8,6 +8,7 @@ import (
 	"crypto/sha256"
 	"encoding/base32"
 	"encoding/base64"
+	"encoding/gob"
 	"fmt"
 	"net"
 	"net/url"
@ -81,6 +82,10 @@ func Init(ctx context.Context) error {
 		builtinAllClientIDs = append(builtinAllClientIDs, clientID)
 	}

+	// This is needed in order to encode and store the struct in the goth/gothic session
+	// during the process of linking the external user.
+	gob.Register(LinkAccountUser{})
+
 	var registeredApps []*OAuth2Application
 	if err := db.GetEngine(ctx).In("client_id", builtinAllClientIDs).Find(&registeredApps); err != nil {
 		return err
@ -605,21 +610,6 @@ func (err ErrOAuthApplicationNotFound) Unwrap() error {
 	return util.ErrNotExist
 }

-// GetActiveOAuth2SourceByName returns a OAuth2 AuthSource based on the given name
-func GetActiveOAuth2SourceByName(ctx context.Context, name string) (*Source, error) {
-	authSource := new(Source)
-	has, err := db.GetEngine(ctx).Where("name = ? and type = ? and is_active = ?", name, OAuth2, true).Get(authSource)
-	if err != nil {
-		return nil, err
-	}
-
-	if !has {
-		return nil, fmt.Errorf("oauth2 source not found, name: %q", name)
-	}
-
-	return authSource, nil
-}
-
 func DeleteOAuth2RelictsByUserID(ctx context.Context, userID int64) error {
 	deleteCond := builder.Select("id").From("oauth2_grant").Where(builder.Eq{"oauth2_grant.user_id": userID})

--- a/models/auth/source.go
+++ b/models/auth/source.go
@ -14,6 +14,7 @@ import (
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"

+	"github.com/markbates/goth"
 	"xorm.io/builder"
 	"xorm.io/xorm"
 	"xorm.io/xorm/convert"
@ -32,6 +33,7 @@ const (
 	DLDAP       // 5
 	OAuth2      // 6
 	SSPI        // 7
+	SAML        // 8
 )

 // String returns the string name of the LoginType
@ -52,6 +54,7 @@ var Names = map[Type]string{
 	PAM:    "PAM",
 	OAuth2: "OAuth2",
 	SSPI:   "SPNEGO with SSPI",
+	SAML:   "SAML",
 }

 // Config represents login config as far as the db is concerned
@ -121,6 +124,12 @@ type Source struct {
 	UpdatedUnix timeutil.TimeStamp `xorm:"INDEX updated"`
 }

+// LinkAccountUser is used to link an external user with a local user
+type LinkAccountUser struct {
+	Type     Type
+	GothUser goth.User
+}
+
 // TableName xorm will read the table name from this method
 func (Source) TableName() string {
 	return "login_source"
@ -180,6 +189,11 @@ func (source *Source) IsSSPI() bool {
 	return source.Type == SSPI
 }

+// IsSAML returns true of this source is of the SAML type.
+func (source *Source) IsSAML() bool {
+	return source.Type == SAML
+}
+
 // HasTLS returns true of this source supports TLS.
 func (source *Source) HasTLS() bool {
 	hasTLSer, ok := source.Cfg.(HasTLSer)
@ -392,3 +406,27 @@ func IsErrSourceInUse(err error) bool {
 func (err ErrSourceInUse) Error() string {
 	return fmt.Sprintf("login source is still used by some users [id: %d]", err.ID)
 }
+
+// GetActiveAuthProviderSources returns all activated sources
+func GetActiveAuthProviderSources(ctx context.Context, authType Type) ([]*Source, error) {
+	sources := make([]*Source, 0, 1)
+	if err := db.GetEngine(ctx).Where("is_active = ? and type = ?", true, authType).Find(&sources); err != nil {
+		return nil, err
+	}
+	return sources, nil
+}
+
+// GetActiveAuthSourceByName returns an AuthSource based on the given name and type
+func GetActiveAuthSourceByName(ctx context.Context, name string, authType Type) (*Source, error) {
+	authSource := new(Source)
+	has, err := db.GetEngine(ctx).Where("name = ? and type = ? and is_active = ?", name, authType, true).Get(authSource)
+	if err != nil {
+		return nil, err
+	}
+
+	if !has {
+		return nil, fmt.Errorf("auth source not found, name: %q", name)
+	}
+
+	return authSource, nil
+}
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@ -522,6 +522,9 @@ Content = Content
 SSPISeparatorReplacement = Separator
 SSPIDefaultLanguage = Default Language

+SAMLMetadata = Either SAML Identity Provider metadata URL or XML
+SAMLMetadataURL = SAML Identity Provider metadata URL is invalid
+
 require_error = ` cannot be empty.`
 alpha_dash_error = ` should contain only alphanumeric, dash ('-') and underscore ('_') characters.`
 alpha_dash_dot_error = ` should contain only alphanumeric, dash ('-'), underscore ('_') and dot ('.') characters.`
@ -3026,7 +3029,18 @@ auths.sspi_separator_replacement = Separator to use instead of \, / and @
 auths.sspi_separator_replacement_helper = The character to use to replace the separators of down-level logon names (eg. the \ in "DOMAIN\user") and user principal names (eg. the @ in "user@example.org").
 auths.sspi_default_language = Default user language
 auths.sspi_default_language_helper = Default language for users automatically created by SSPI auth method. Leave empty if you prefer language to be automatically detected.
+auths.saml_nameidformat = SAML NameID Format
+auths.saml_identity_provider_metadata_url = Identity Provider Metadata URL
+auths.saml_identity_provider_metadata = Identity Provider Metadata XML
+auths.saml_insecure_skip_assertion_signature_validation = [Insecure] Skip Assertion Signature Validation
+auths.saml_service_provider_certificate = Service Provider Certificate
+auths.saml_service_provider_private_key = Service Provider Private Key
+auths.saml_identity_provider_email_assertion_key = Email Assertion Key
+auths.saml_identity_provider_name_assertion_key = Name Assertion Key
+auths.saml_identity_provider_username_assertion_key = Username Assertion Key
+auths.saml_icon_url = Icon URL
 auths.tips = Tips
+auths.tips.saml = Documentation can be found at https://docs.gitea.com/usage/authentication#saml
 auths.tips.oauth2.general = OAuth2 Authentication
 auths.tips.oauth2.general.tip = When registering a new OAuth2 authentication, the callback/redirect URL should be:
 auths.tip.oauth2_provider = OAuth2 Provider
--- a/routers/init.go
+++ b/routers/init.go
@ -35,6 +35,7 @@ import (
 	actions_service "code.gitea.io/gitea/services/actions"
 	"code.gitea.io/gitea/services/auth"
 	"code.gitea.io/gitea/services/auth/source/oauth2"
+	"code.gitea.io/gitea/services/auth/source/saml"
 	"code.gitea.io/gitea/services/automerge"
 	"code.gitea.io/gitea/services/cron"
 	feed_service "code.gitea.io/gitea/services/feed"
@ -138,6 +139,7 @@ func InitWebInstalled(ctx context.Context) {
 	log.Info("ORM engine initialization successful!")
 	mustInit(system.Init)
 	mustInitCtx(ctx, oauth2.Init)
+	mustInitCtx(ctx, saml.Init)

 	mustInit(release_service.Init)

--- a/routers/web/admin/auths.go
+++ b/routers/web/admin/auths.go
@ -1,9 +1,12 @@
 // Copyright 2014 The Gogs Authors. All rights reserved.
+// Copyright 2024 The Gitea Authors. All rights reserved.
 // SPDX-License-Identifier: MIT

 package admin

 import (
+	"crypto/tls"
+	"crypto/x509"
 	"errors"
 	"fmt"
 	"net/http"
@ -25,6 +28,7 @@ import (
 	"code.gitea.io/gitea/services/auth/source/ldap"
 	"code.gitea.io/gitea/services/auth/source/oauth2"
 	pam_service "code.gitea.io/gitea/services/auth/source/pam"
+	"code.gitea.io/gitea/services/auth/source/saml"
 	"code.gitea.io/gitea/services/auth/source/smtp"
 	"code.gitea.io/gitea/services/auth/source/sspi"
 	"code.gitea.io/gitea/services/forms"
@ -71,6 +75,7 @@ var (
 			{auth.SMTP.String(), auth.SMTP},
 			{auth.OAuth2.String(), auth.OAuth2},
 			{auth.SSPI.String(), auth.SSPI},
+			{auth.SAML.String(), auth.SAML},
 		}
 		if pam.Supported {
 			items = append(items, dropdownItem{auth.Names[auth.PAM], auth.PAM})
@ -83,6 +88,16 @@ var (
 		{ldap.SecurityProtocolNames[ldap.SecurityProtocolLDAPS], ldap.SecurityProtocolLDAPS},
 		{ldap.SecurityProtocolNames[ldap.SecurityProtocolStartTLS], ldap.SecurityProtocolStartTLS},
 	}
+
+	nameIDFormats = []dropdownItem{
+		{saml.NameIDFormatNames[saml.SAML20Persistent], saml.SAML20Persistent}, // use this as default value
+		{saml.NameIDFormatNames[saml.SAML11Email], saml.SAML11Email},
+		{saml.NameIDFormatNames[saml.SAML11Persistent], saml.SAML11Persistent},
+		{saml.NameIDFormatNames[saml.SAML11Unspecified], saml.SAML11Unspecified},
+		{saml.NameIDFormatNames[saml.SAML20Email], saml.SAML20Email},
+		{saml.NameIDFormatNames[saml.SAML20Transient], saml.SAML20Transient},
+		{saml.NameIDFormatNames[saml.SAML20Unspecified], saml.SAML20Unspecified},
+	}
 )

 // NewAuthSource render adding a new auth source page
@ -98,6 +113,8 @@ func NewAuthSource(ctx *context.Context) {
 	ctx.Data["is_sync_enabled"] = true
 	ctx.Data["AuthSources"] = authSources
 	ctx.Data["SecurityProtocols"] = securityProtocols
+	ctx.Data["CurrentNameIDFormat"] = saml.NameIDFormatNames[saml.SAML20Persistent]
+	ctx.Data["NameIDFormats"] = nameIDFormats
 	ctx.Data["SMTPAuths"] = smtp.Authenticators
 	oauth2providers := oauth2.GetSupportedOAuth2Providers()
 	ctx.Data["OAuth2Providers"] = oauth2providers
@ -231,6 +248,52 @@ func parseSSPIConfig(ctx *context.Context, form forms.AuthenticationForm) (*sspi
 	}, nil
 }

+func parseSAMLConfig(ctx *context.Context, form forms.AuthenticationForm) (*saml.Source, error) {
+	if util.IsEmptyString(form.IdentityProviderMetadata) && util.IsEmptyString(form.IdentityProviderMetadataURL) {
+		return nil, fmt.Errorf("%s %s", ctx.Tr("form.SAMLMetadata"), ctx.Tr("form.require_error"))
+	}
+
+	if !util.IsEmptyString(form.IdentityProviderMetadataURL) {
+		_, err := url.Parse(form.IdentityProviderMetadataURL)
+		if err != nil {
+			return nil, fmt.Errorf("%s", ctx.Tr("form.SAMLMetadataURL"))
+		}
+	}
+
+	// check the integrity of the certificate and private key (autogenerated if these form fields are blank)
+	if !util.IsEmptyString(form.ServiceProviderCertificate) && !util.IsEmptyString(form.ServiceProviderPrivateKey) {
+		keyPair, err := tls.X509KeyPair([]byte(form.ServiceProviderCertificate), []byte(form.ServiceProviderPrivateKey))
+		if err != nil {
+			return nil, err
+		}
+		keyPair.Leaf, err = x509.ParseCertificate(keyPair.Certificate[0])
+		if err != nil {
+			return nil, err
+		}
+	} else {
+		privateKey, cert, err := saml.GenerateSAMLSPKeypair()
+		if err != nil {
+			return nil, err
+		}
+
+		form.ServiceProviderPrivateKey = privateKey
+		form.ServiceProviderCertificate = cert
+	}
+
+	return &saml.Source{
+		IdentityProviderMetadata:                 form.IdentityProviderMetadata,
+		IdentityProviderMetadataURL:              form.IdentityProviderMetadataURL,
+		InsecureSkipAssertionSignatureValidation: form.InsecureSkipAssertionSignatureValidation,
+		NameIDFormat:                             saml.NameIDFormat(form.NameIDFormat),
+		ServiceProviderCertificate:               form.ServiceProviderCertificate,
+		ServiceProviderPrivateKey:                form.ServiceProviderPrivateKey,
+		EmailAssertionKey:                        form.EmailAssertionKey,
+		NameAssertionKey:                         form.NameAssertionKey,
+		UsernameAssertionKey:                     form.UsernameAssertionKey,
+		IconURL:                                  form.SAMLIconURL,
+	}, nil
+}
+
 // NewAuthSourcePost response for adding an auth source
 func NewAuthSourcePost(ctx *context.Context) {
 	form := *web.GetForm(ctx).(*forms.AuthenticationForm)
@ -244,6 +307,8 @@ func NewAuthSourcePost(ctx *context.Context) {
 	ctx.Data["SMTPAuths"] = smtp.Authenticators
 	oauth2providers := oauth2.GetSupportedOAuth2Providers()
 	ctx.Data["OAuth2Providers"] = oauth2providers
+	ctx.Data["CurrentNameIDFormat"] = saml.NameIDFormatNames[saml.NameIDFormat(form.NameIDFormat)]
+	ctx.Data["NameIDFormats"] = nameIDFormats

 	ctx.Data["SSPIAutoCreateUsers"] = true
 	ctx.Data["SSPIAutoActivateUsers"] = true
@ -290,6 +355,13 @@ func NewAuthSourcePost(ctx *context.Context) {
 			ctx.RenderWithErr(ctx.Tr("admin.auths.login_source_of_type_exist"), tplAuthNew, form)
 			return
 		}
+	case auth.SAML:
+		var err error
+		config, err = parseSAMLConfig(ctx, form)
+		if err != nil {
+			ctx.RenderWithErr(err.Error(), tplAuthNew, form)
+			return
+		}
 	default:
 		ctx.Error(http.StatusBadRequest)
 		return
@ -336,6 +408,7 @@ func EditAuthSource(ctx *context.Context) {
 	ctx.Data["SMTPAuths"] = smtp.Authenticators
 	oauth2providers := oauth2.GetSupportedOAuth2Providers()
 	ctx.Data["OAuth2Providers"] = oauth2providers
+	ctx.Data["NameIDFormats"] = nameIDFormats

 	source, err := auth.GetSourceByID(ctx, ctx.ParamsInt64(":authid"))
 	if err != nil {
@ -344,6 +417,9 @@ func EditAuthSource(ctx *context.Context) {
 	}
 	ctx.Data["Source"] = source
 	ctx.Data["HasTLS"] = source.HasTLS()
+	if source.IsSAML() {
+		ctx.Data["CurrentNameIDFormat"] = saml.NameIDFormatNames[source.Cfg.(*saml.Source).NameIDFormat]
+	}

 	if source.IsOAuth2() {
 		type Named interface {
@ -378,6 +454,8 @@ func EditAuthSourcePost(ctx *context.Context) {
 	}
 	ctx.Data["Source"] = source
 	ctx.Data["HasTLS"] = source.HasTLS()
+	ctx.Data["CurrentNameIDFormat"] = saml.NameIDFormatNames[saml.SAML20Persistent]
+	ctx.Data["NameIDFormats"] = nameIDFormats

 	if ctx.HasError() {
 		ctx.HTML(http.StatusOK, tplAuthEdit)
@ -412,6 +490,12 @@ func EditAuthSourcePost(ctx *context.Context) {
 			ctx.RenderWithErr(err.Error(), tplAuthEdit, form)
 			return
 		}
+	case auth.SAML:
+		config, err = parseSAMLConfig(ctx, form)
+		if err != nil {
+			ctx.RenderWithErr(err.Error(), tplAuthEdit, form)
+			return
+		}
 	default:
 		ctx.Error(http.StatusBadRequest)
 		return
--- a/routers/web/auth/auth.go
+++ b/routers/web/auth/auth.go
@ -28,6 +28,7 @@ import (
 	"code.gitea.io/gitea/routers/utils"
 	auth_service "code.gitea.io/gitea/services/auth"
 	"code.gitea.io/gitea/services/auth/source/oauth2"
+	"code.gitea.io/gitea/services/auth/source/saml"
 	"code.gitea.io/gitea/services/externalaccount"
 	"code.gitea.io/gitea/services/forms"
 	"code.gitea.io/gitea/services/mailer"
@ -170,6 +171,14 @@ func SignIn(ctx *context.Context) {
 		return
 	}
 	ctx.Data["OAuth2Providers"] = oauth2Providers
+
+	samlProviders, err := saml.GetSAMLProviders(ctx, util.OptionalBoolTrue)
+	if err != nil {
+		ctx.ServerError("UserSignIn", err)
+		return
+	}
+	ctx.Data["SAMLProviders"] = samlProviders
+
 	ctx.Data["Title"] = ctx.Tr("sign_in")
 	ctx.Data["SignInLink"] = setting.AppSubURL + "/user/login"
 	ctx.Data["PageIsSignIn"] = true
@ -193,6 +202,14 @@ func SignInPost(ctx *context.Context) {
 		return
 	}
 	ctx.Data["OAuth2Providers"] = oauth2Providers
+
+	samlProviders, err := saml.GetSAMLProviders(ctx, util.OptionalBoolTrue)
+	if err != nil {
+		ctx.ServerError("UserSignIn", err)
+		return
+	}
+	ctx.Data["SAMLProviders"] = samlProviders
+
 	ctx.Data["Title"] = ctx.Tr("sign_in")
 	ctx.Data["SignInLink"] = setting.AppSubURL + "/user/login"
 	ctx.Data["PageIsSignIn"] = true
@ -504,7 +521,7 @@ func SignUpPost(ctx *context.Context) {
 		Passwd: form.Password,
 	}

-	if !createAndHandleCreatedUser(ctx, tplSignUp, form, u, nil, nil, false) {
+	if !createAndHandleCreatedUser(ctx, tplSignUp, form, u, nil, nil, false, auth.NoType) {
 		// error already handled
 		return
 	}
@ -515,16 +532,16 @@ func SignUpPost(ctx *context.Context) {

 // createAndHandleCreatedUser calls createUserInContext and
 // then handleUserCreated.
-func createAndHandleCreatedUser(ctx *context.Context, tpl base.TplName, form any, u *user_model.User, overwrites *user_model.CreateUserOverwriteOptions, gothUser *goth.User, allowLink bool) bool {
-	if !createUserInContext(ctx, tpl, form, u, overwrites, gothUser, allowLink) {
+func createAndHandleCreatedUser(ctx *context.Context, tpl base.TplName, form any, u *user_model.User, overwrites *user_model.CreateUserOverwriteOptions, gothUser *goth.User, allowLink bool, authType auth.Type) bool {
+	if !createUserInContext(ctx, tpl, form, u, overwrites, gothUser, allowLink, authType) {
 		return false
 	}
-	return handleUserCreated(ctx, u, gothUser)
+	return handleUserCreated(ctx, u, gothUser, authType)
 }

 // createUserInContext creates a user and handles errors within a given context.
 // Optionally a template can be specified.
-func createUserInContext(ctx *context.Context, tpl base.TplName, form any, u *user_model.User, overwrites *user_model.CreateUserOverwriteOptions, gothUser *goth.User, allowLink bool) (ok bool) {
+func createUserInContext(ctx *context.Context, tpl base.TplName, form any, u *user_model.User, overwrites *user_model.CreateUserOverwriteOptions, gothUser *goth.User, allowLink bool, authType auth.Type) (ok bool) {
 	if err := user_model.CreateUser(ctx, u, overwrites); err != nil {
 		if allowLink && (user_model.IsErrUserAlreadyExist(err) || user_model.IsErrEmailAlreadyUsed(err)) {
 			if setting.OAuth2Client.AccountLinking == setting.OAuth2AccountLinkingAuto {
@ -541,10 +558,10 @@ func createUserInContext(ctx *context.Context, tpl base.TplName, form any, u *us
 				}

 				// TODO: probably we should respect 'remember' user's choice...
-				linkAccount(ctx, user, *gothUser, true)
+				linkAccount(ctx, user, *gothUser, true, authType)
 				return false // user is already created here, all redirects are handled
 			} else if setting.OAuth2Client.AccountLinking == setting.OAuth2AccountLinkingLogin {
-				showLinkingLogin(ctx, *gothUser)
+				showLinkingLogin(ctx, *gothUser, authType)
 				return false // user will be created only after linking login
 			}
 		}
@ -590,7 +607,7 @@ func createUserInContext(ctx *context.Context, tpl base.TplName, form any, u *us
 // handleUserCreated does additional steps after a new user is created.
 // It auto-sets admin for the only user, updates the optional external user and
 // sends a confirmation email if required.
-func handleUserCreated(ctx *context.Context, u *user_model.User, gothUser *goth.User) (ok bool) {
+func handleUserCreated(ctx *context.Context, u *user_model.User, gothUser *goth.User, authType auth.Type) (ok bool) {
 	// Auto-set admin for the only user.
 	if user_model.CountUsers(ctx, nil) == 1 {
 		opts := &user_service.UpdateOptions{
@ -606,7 +623,7 @@ func handleUserCreated(ctx *context.Context, u *user_model.User, gothUser *goth.

 	// update external user information
 	if gothUser != nil {
-		if err := externalaccount.UpdateExternalUser(ctx, u, *gothUser); err != nil {
+		if err := externalaccount.UpdateExternalUser(ctx, u, *gothUser, authType); err != nil {
 			if !errors.Is(err, util.ErrNotExist) {
 				log.Error("UpdateExternalUser failed: %v", err)
 			}
--- a/routers/web/auth/linkaccount.go
+++ b/routers/web/auth/linkaccount.go
@ -48,13 +48,13 @@ func LinkAccount(ctx *context.Context) {
 	ctx.Data["SignInLink"] = setting.AppSubURL + "/user/link_account_signin"
 	ctx.Data["SignUpLink"] = setting.AppSubURL + "/user/link_account_signup"

-	gothUser := ctx.Session.Get("linkAccountGothUser")
-	if gothUser == nil {
+	externalLinkUser := ctx.Session.Get("linkAccountUser")
+	if externalLinkUser == nil {
 		ctx.ServerError("UserSignIn", errors.New("not in LinkAccount session"))
 		return
 	}

-	gu, _ := gothUser.(goth.User)
+	gu := externalLinkUser.(auth.LinkAccountUser).GothUser
 	uname, err := getUserName(&gu)
 	if err != nil {
 		ctx.ServerError("UserSignIn", err)
@ -135,12 +135,14 @@ func LinkAccountPostSignIn(ctx *context.Context) {
 	ctx.Data["SignInLink"] = setting.AppSubURL + "/user/link_account_signin"
 	ctx.Data["SignUpLink"] = setting.AppSubURL + "/user/link_account_signup"

-	gothUser := ctx.Session.Get("linkAccountGothUser")
-	if gothUser == nil {
+	externalLinkUserInterface := ctx.Session.Get("linkAccountUser")
+	if externalLinkUserInterface == nil {
 		ctx.ServerError("UserSignIn", errors.New("not in LinkAccount session"))
 		return
 	}

+	externalLinkUser := externalLinkUserInterface.(auth.LinkAccountUser)
+
 	if ctx.HasError() {
 		ctx.HTML(http.StatusOK, tplLinkAccount)
 		return
@ -152,10 +154,10 @@ func LinkAccountPostSignIn(ctx *context.Context) {
 		return
 	}

-	linkAccount(ctx, u, gothUser.(goth.User), signInForm.Remember)
+	linkAccount(ctx, u, externalLinkUser.GothUser, signInForm.Remember, externalLinkUser.Type)
 }

-func linkAccount(ctx *context.Context, u *user_model.User, gothUser goth.User, remember bool) {
+func linkAccount(ctx *context.Context, u *user_model.User, gothUser goth.User, remember bool, authType auth.Type) {
 	updateAvatarIfNeed(ctx, gothUser.AvatarURL, u)

 	// If this user is enrolled in 2FA, we can't sign the user in just yet.
@ -168,7 +170,7 @@ func linkAccount(ctx *context.Context, u *user_model.User, gothUser goth.User, r
 			return
 		}

-		err = externalaccount.LinkAccountToUser(ctx, u, gothUser)
+		err = externalaccount.LinkAccountToUser(ctx, u, gothUser, authType)
 		if err != nil {
 			ctx.ServerError("UserLinkAccount", err)
 			return
@ -222,14 +224,14 @@ func LinkAccountPostRegister(ctx *context.Context) {
 	ctx.Data["SignInLink"] = setting.AppSubURL + "/user/link_account_signin"
 	ctx.Data["SignUpLink"] = setting.AppSubURL + "/user/link_account_signup"

-	gothUserInterface := ctx.Session.Get("linkAccountGothUser")
-	if gothUserInterface == nil {
+	externalLinkUser := ctx.Session.Get("linkAccountUser")
+	if externalLinkUser == nil {
 		ctx.ServerError("UserSignUp", errors.New("not in LinkAccount session"))
 		return
 	}
-	gothUser, ok := gothUserInterface.(goth.User)
+	linkUser, ok := externalLinkUser.(auth.LinkAccountUser)
 	if !ok {
-		ctx.ServerError("UserSignUp", fmt.Errorf("session linkAccountGothUser type is %t but not goth.User", gothUserInterface))
+		ctx.ServerError("UserSignUp", fmt.Errorf("session linkAccountUser type is %t but not goth.User", externalLinkUser))
 		return
 	}

@ -275,7 +277,7 @@ func LinkAccountPostRegister(ctx *context.Context) {
 		}
 	}

-	authSource, err := auth.GetActiveOAuth2SourceByName(ctx, gothUser.Provider)
+	authSource, err := auth.GetActiveAuthSourceByName(ctx, linkUser.GothUser.Provider, linkUser.Type)
 	if err != nil {
 		ctx.ServerError("CreateUser", err)
 		return
@ -285,21 +287,24 @@ func LinkAccountPostRegister(ctx *context.Context) {
 		Name:        form.UserName,
 		Email:       form.Email,
 		Passwd:      form.Password,
-		LoginType:   auth.OAuth2,
+		LoginType:   authSource.Type,
 		LoginSource: authSource.ID,
-		LoginName:   gothUser.UserID,
+		LoginName:   linkUser.GothUser.UserID,
 	}

-	if !createAndHandleCreatedUser(ctx, tplLinkAccount, form, u, nil, &gothUser, false) {
+	if !createAndHandleCreatedUser(ctx, tplLinkAccount, form, u, nil, &linkUser.GothUser, false, linkUser.Type) {
 		// error already handled
 		return
 	}

+	if linkUser.Type == auth.OAuth2 {
 		source := authSource.Cfg.(*oauth2.Source)
-	if err := syncGroupsToTeams(ctx, source, &gothUser, u); err != nil {
+		if err := syncGroupsToTeams(ctx, source, &linkUser.GothUser, u); err != nil {
 			ctx.ServerError("SyncGroupsToTeams", err)
 			return
 		}
+	}
+	// TODO we will support some form of group mapping for SAML

 	handleSignIn(ctx, u, false)
 }
--- a/routers/web/auth/oauth.go
+++ b/routers/web/auth/oauth.go
@ -841,7 +841,7 @@ func handleAuthorizeError(ctx *context.Context, authErr AuthorizeError, redirect
 func SignInOAuth(ctx *context.Context) {
 	provider := ctx.Params(":provider")

-	authSource, err := auth.GetActiveOAuth2SourceByName(ctx, provider)
+	authSource, err := auth.GetActiveAuthSourceByName(ctx, provider, auth.OAuth2)
 	if err != nil {
 		ctx.ServerError("SignIn", err)
 		return
@ -892,7 +892,7 @@ func SignInOAuthCallback(ctx *context.Context) {
 	}

 	// first look if the provider is still active
-	authSource, err := auth.GetActiveOAuth2SourceByName(ctx, provider)
+	authSource, err := auth.GetActiveAuthSourceByName(ctx, provider, auth.OAuth2)
 	if err != nil {
 		ctx.ServerError("SignIn", err)
 		return
@ -935,7 +935,7 @@ func SignInOAuthCallback(ctx *context.Context) {
 	if u == nil {
 		if ctx.Doer != nil {
 			// attach user to already logged in user
-			err = externalaccount.LinkAccountToUser(ctx, ctx.Doer, gothUser)
+			err = externalaccount.LinkAccountToUser(ctx, ctx.Doer, gothUser, auth.OAuth2)
 			if err != nil {
 				ctx.ServerError("UserLinkAccount", err)
 				return
@ -988,7 +988,7 @@ func SignInOAuthCallback(ctx *context.Context) {
 			u.IsAdmin = isAdmin.ValueOrDefault(false)
 			u.IsRestricted = isRestricted.ValueOrDefault(false)

-			if !createAndHandleCreatedUser(ctx, base.TplName(""), nil, u, overwriteDefault, &gothUser, setting.OAuth2Client.AccountLinking != setting.OAuth2AccountLinkingDisabled) {
+			if !createAndHandleCreatedUser(ctx, base.TplName(""), nil, u, overwriteDefault, &gothUser, setting.OAuth2Client.AccountLinking != setting.OAuth2AccountLinkingDisabled, auth.OAuth2) {
 				// error already handled
 				return
 			}
@ -999,7 +999,7 @@ func SignInOAuthCallback(ctx *context.Context) {
 			}
 		} else {
 			// no existing user is found, request attach or new account
-			showLinkingLogin(ctx, gothUser)
+			showLinkingLogin(ctx, gothUser, auth.OAuth2)
 			return
 		}
 	}
@ -1063,9 +1063,12 @@ func getUserAdminAndRestrictedFromGroupClaims(source *oauth2.Source, gothUser *g
 	return isAdmin, isRestricted
 }

-func showLinkingLogin(ctx *context.Context, gothUser goth.User) {
+func showLinkingLogin(ctx *context.Context, gothUser goth.User, authType auth.Type) {
 	if err := updateSession(ctx, nil, map[string]any{
-		"linkAccountGothUser": gothUser,
+		"linkAccountUser": auth.LinkAccountUser{
+			Type:     authType,
+			GothUser: gothUser,
+		},
 	}); err != nil {
 		ctx.ServerError("updateSession", err)
 		return
@ -1144,7 +1147,7 @@ func handleOAuth2SignIn(ctx *context.Context, source *auth.Source, u *user_model
 		}

 		// update external user information
-		if err := externalaccount.UpdateExternalUser(ctx, u, gothUser); err != nil {
+		if err := externalaccount.UpdateExternalUser(ctx, u, gothUser, auth.OAuth2); err != nil {
 			if !errors.Is(err, util.ErrNotExist) {
 				log.Error("UpdateExternalUser failed: %v", err)
 			}
--- a/routers/web/auth/openid.go
+++ b/routers/web/auth/openid.go
@ -8,6 +8,7 @@ import (
 	"net/http"
 	"net/url"

+	auth_model "code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
 	"code.gitea.io/gitea/modules/auth/openid"
 	"code.gitea.io/gitea/modules/base"
@ -363,7 +364,7 @@ func RegisterOpenIDPost(ctx *context.Context) {
 		Email:  form.Email,
 		Passwd: password,
 	}
-	if !createUserInContext(ctx, tplSignUpOID, form, u, nil, nil, false) {
+	if !createUserInContext(ctx, tplSignUpOID, form, u, nil, nil, false, auth_model.NoType) {
 		// error already handled
 		return
 	}
@ -379,7 +380,7 @@ func RegisterOpenIDPost(ctx *context.Context) {
 		return
 	}

-	if !handleUserCreated(ctx, u, nil) {
+	if !handleUserCreated(ctx, u, nil, auth_model.NoType) {
 		// error already handled
 		return
 	}
--- a/routers/web/auth/saml.go
+++ b/routers/web/auth/saml.go
@ -0,0 +1,172 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package auth
+
+import (
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+
+	"code.gitea.io/gitea/models/auth"
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+	"code.gitea.io/gitea/modules/web/middleware"
+	"code.gitea.io/gitea/services/auth/source/saml"
+	"code.gitea.io/gitea/services/externalaccount"
+
+	"github.com/markbates/goth"
+)
+
+func SignInSAML(ctx *context.Context) {
+	provider := ctx.Params(":provider")
+
+	loginSource, err := auth.GetActiveAuthSourceByName(ctx, provider, auth.SAML)
+	if err != nil || loginSource == nil {
+		ctx.NotFound("SAMLMetadata", err)
+		return
+	}
+
+	if err = loginSource.Cfg.(*saml.Source).Callout(ctx.Req, ctx.Resp); err != nil {
+		if strings.Contains(err.Error(), "no provider for ") {
+			ctx.Error(http.StatusNotFound)
+			return
+		}
+		ctx.ServerError("SignIn", err)
+	}
+}
+
+func SignInSAMLCallback(ctx *context.Context) {
+	provider := ctx.Params(":provider")
+	loginSource, err := auth.GetActiveAuthSourceByName(ctx, provider, auth.SAML)
+	if err != nil || loginSource == nil {
+		ctx.NotFound("SignInSAMLCallback", err)
+		return
+	}
+
+	if loginSource == nil {
+		ctx.ServerError("SignIn", fmt.Errorf("no valid provider found, check configured callback url in provider"))
+		return
+	}
+
+	u, gothUser, err := samlUserLoginCallback(*ctx, loginSource, ctx.Req, ctx.Resp)
+	if err != nil {
+		ctx.ServerError("SignInSAMLCallback", err)
+		return
+	}
+
+	if u == nil {
+		if ctx.Doer != nil {
+			// attach user to already logged in user
+			err = externalaccount.LinkAccountToUser(ctx, ctx.Doer, gothUser, auth.SAML)
+			if err != nil {
+				ctx.ServerError("LinkAccountToUser", err)
+				return
+			}
+
+			ctx.Redirect(setting.AppSubURL + "/user/settings/security")
+			return
+		} else if !setting.Service.AllowOnlyInternalRegistration && false {
+			// TODO: allow auto registration from saml users (OAuth2 uses the following setting.OAuth2Client.EnableAutoRegistration)
+		} else {
+			// no existing user is found, request attach or new account
+			showLinkingLogin(ctx, gothUser, auth.SAML)
+			return
+		}
+	}
+
+	handleSamlSignIn(ctx, loginSource, u, gothUser)
+}
+
+func handleSamlSignIn(ctx *context.Context, source *auth.Source, u *user_model.User, gothUser goth.User) {
+	if err := updateSession(ctx, nil, map[string]any{
+		"uid":   u.ID,
+		"uname": u.Name,
+	}); err != nil {
+		ctx.ServerError("updateSession", err)
+		return
+	}
+
+	// Clear whatever CSRF cookie has right now, force to generate a new one
+	ctx.Csrf.DeleteCookie(ctx)
+
+	// Register last login
+	u.SetLastLogin()
+
+	// update external user information
+	if err := externalaccount.UpdateExternalUser(ctx, u, gothUser, auth.SAML); err != nil {
+		if !errors.Is(err, util.ErrNotExist) {
+			log.Error("UpdateExternalUser failed: %v", err)
+		}
+	}
+
+	if err := resetLocale(ctx, u); err != nil {
+		ctx.ServerError("resetLocale", err)
+		return
+	}
+
+	if redirectTo := ctx.GetSiteCookie("redirect_to"); len(redirectTo) > 0 {
+		middleware.DeleteRedirectToCookie(ctx.Resp)
+		ctx.RedirectToFirst(redirectTo)
+		return
+	}
+
+	ctx.Redirect(setting.AppSubURL + "/")
+}
+
+func samlUserLoginCallback(ctx context.Context, authSource *auth.Source, request *http.Request, response http.ResponseWriter) (*user_model.User, goth.User, error) {
+	samlSource := authSource.Cfg.(*saml.Source)
+
+	gothUser, err := samlSource.Callback(request, response)
+	if err != nil {
+		return nil, gothUser, err
+	}
+
+	user := &user_model.User{
+		LoginName:   gothUser.UserID,
+		LoginType:   auth.SAML,
+		LoginSource: authSource.ID,
+	}
+
+	hasUser, err := user_model.GetUser(ctx, user)
+	if err != nil {
+		return nil, goth.User{}, err
+	}
+
+	if hasUser {
+		return user, gothUser, nil
+	}
+
+	// search in external linked users
+	externalLoginUser := &user_model.ExternalLoginUser{
+		ExternalID:    gothUser.UserID,
+		LoginSourceID: authSource.ID,
+	}
+	hasUser, err = user_model.GetExternalLogin(ctx, externalLoginUser)
+	if err != nil {
+		return nil, goth.User{}, err
+	}
+	if hasUser {
+		user, err = user_model.GetUserByID(request.Context(), externalLoginUser.UserID)
+		return user, gothUser, err
+	}
+
+	// no user found to login
+	return nil, gothUser, nil
+}
+
+func SAMLMetadata(ctx *context.Context) {
+	provider := ctx.Params(":provider")
+	loginSource, err := auth.GetActiveAuthSourceByName(ctx, provider, auth.SAML)
+	if err != nil || loginSource == nil {
+		ctx.NotFound("SAMLMetadata", err)
+		return
+	}
+	if err = loginSource.Cfg.(*saml.Source).Metadata(ctx.Req, ctx.Resp); err != nil {
+		ctx.ServerError("SAMLMetadata", err)
+	}
+}
--- a/routers/web/web.go
+++ b/routers/web/web.go
@ -667,6 +667,11 @@ func registerRoutes(m *web.Route) {
 			m.Get("/{provider}", auth.SignInOAuth)
 			m.Get("/{provider}/callback", auth.SignInOAuthCallback)
 		})
+		m.Group("/saml", func() {
+			m.Get("/{provider}", auth.SignInSAML) // redir to SAML IDP
+			m.Post("/{provider}/acs", auth.SignInSAMLCallback)
+			m.Get("/{provider}/metadata", auth.SAMLMetadata)
+		})
 	})
 	// ***** END: User *****

--- a/services/auth/source/saml/assert_interface_test.go
+++ b/services/auth/source/saml/assert_interface_test.go
@ -0,0 +1,22 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml_test
+
+import (
+	auth_model "code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/services/auth"
+	"code.gitea.io/gitea/services/auth/source/saml"
+)
+
+// This test file exists to assert that our Source exposes the interfaces that we expect
+// It tightly binds the interfaces and implementation without breaking go import cycles
+
+type sourceInterface interface {
+	auth_model.Config
+	auth_model.SourceSettable
+	auth_model.RegisterableSource
+	auth.PasswordAuthenticator
+}
+
+var _ (sourceInterface) = &saml.Source{}
--- a/services/auth/source/saml/init.go
+++ b/services/auth/source/saml/init.go
@ -0,0 +1,29 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+import (
+	"context"
+	"sync"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/modules/log"
+)
+
+var samlRWMutex = sync.RWMutex{}
+
+func Init(ctx context.Context) error {
+	loginSources, _ := auth.GetActiveAuthProviderSources(ctx, auth.SAML)
+	for _, source := range loginSources {
+		samlSource, ok := source.Cfg.(*Source)
+		if !ok {
+			continue
+		}
+		err := samlSource.RegisterSource()
+		if err != nil {
+			log.Error("Unable to register source: %s due to Error: %v.", source.Name, err)
+		}
+	}
+	return nil
+}
--- a/services/auth/source/saml/name_id_format.go
+++ b/services/auth/source/saml/name_id_format.go
@ -0,0 +1,38 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+type NameIDFormat int
+
+const (
+	SAML11Email NameIDFormat = iota + 1
+	SAML11Persistent
+	SAML11Unspecified
+	SAML20Email
+	SAML20Persistent
+	SAML20Transient
+	SAML20Unspecified
+)
+
+const DefaultNameIDFormat NameIDFormat = SAML20Persistent
+
+var NameIDFormatNames = map[NameIDFormat]string{
+	SAML11Email:       "urn:oasis:names:tc:SAML:1.1:nameid-format:emailAddress",
+	SAML11Persistent:  "urn:oasis:names:tc:SAML:1.1:nameid-format:persistent",
+	SAML11Unspecified: "urn:oasis:names:tc:SAML:1.1:nameid-format:unspecified",
+	SAML20Email:       "urn:oasis:names:tc:SAML:2.0:nameid-format:emailAddress",
+	SAML20Persistent:  "urn:oasis:names:tc:SAML:2.0:nameid-format:persistent",
+	SAML20Transient:   "urn:oasis:names:tc:SAML:2.0:nameid-format:transient",
+	SAML20Unspecified: "urn:oasis:names:tc:SAML:2.0:nameid-format:unspecified",
+}
+
+// String returns the name of the NameIDFormat
+func (n NameIDFormat) String() string {
+	return NameIDFormatNames[n]
+}
+
+// Int returns the int value of the NameIDFormat
+func (n NameIDFormat) Int() int {
+	return int(n)
+}
--- a/services/auth/source/saml/providers.go
+++ b/services/auth/source/saml/providers.go
@ -0,0 +1,109 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+import (
+	"context"
+	"fmt"
+	"html"
+	"html/template"
+	"io"
+	"net/http"
+	"sort"
+	"time"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/httplib"
+	"code.gitea.io/gitea/modules/svg"
+	"code.gitea.io/gitea/modules/util"
+)
+
+// Providers is list of known/available providers.
+type Providers map[string]Source
+
+var providers = Providers{}
+
+// Provider is an interface for describing a single SAML provider
+type Provider interface {
+	Name() string
+	IconHTML(size int) template.HTML
+}
+
+// AuthSourceProvider is a SAML provider
+type AuthSourceProvider struct {
+	sourceName, iconURL string
+}
+
+func (p *AuthSourceProvider) Name() string {
+	return p.sourceName
+}
+
+func (p *AuthSourceProvider) IconHTML(size int) template.HTML {
+	if p.iconURL != "" {
+		return template.HTML(fmt.Sprintf(`<img class="gt-object-contain gt-mr-3" width="%d" height="%d" src="%s" alt="%s">`,
+			size,
+			size,
+			html.EscapeString(p.iconURL), html.EscapeString(p.Name()),
+		))
+	}
+	return svg.RenderHTML("gitea-lock-cog", size, "gt-mr-3")
+}
+
+func readIdentityProviderMetadata(ctx context.Context, source *Source) ([]byte, error) {
+	if source.IdentityProviderMetadata != "" {
+		return []byte(source.IdentityProviderMetadata), nil
+	}
+
+	req := httplib.NewRequest(source.IdentityProviderMetadataURL, "GET")
+	req.SetTimeout(20*time.Second, time.Minute)
+	resp, err := req.Response()
+	if err != nil {
+		return nil, fmt.Errorf("Unable to contact gitea: %v", err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return nil, err
+	}
+
+	data, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return nil, err
+	}
+	return data, nil
+}
+
+func createProviderFromSource(source *auth.Source) (Provider, error) {
+	samlCfg, ok := source.Cfg.(*Source)
+	if !ok {
+		return nil, fmt.Errorf("invalid SAML source config: %v", samlCfg)
+	}
+	return &AuthSourceProvider{sourceName: source.Name, iconURL: samlCfg.IconURL}, nil
+}
+
+// GetSAMLProviders returns the list of configured SAML providers
+func GetSAMLProviders(ctx context.Context, isActive util.OptionalBool) ([]Provider, error) {
+	authSources, err := db.Find[auth.Source](ctx, auth.FindSourcesOptions{
+		IsActive:  isActive,
+		LoginType: auth.SAML,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	samlProviders := make([]Provider, 0, len(authSources))
+	for _, source := range authSources {
+		p, err := createProviderFromSource(source)
+		if err != nil {
+			return nil, err
+		}
+		samlProviders = append(samlProviders, p)
+	}
+
+	sort.Slice(samlProviders, func(i, j int) bool {
+		return samlProviders[i].Name() < samlProviders[j].Name()
+	})
+
+	return samlProviders, nil
+}
--- a/services/auth/source/saml/source.go
+++ b/services/auth/source/saml/source.go
@ -0,0 +1,202 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/tls"
+	"crypto/x509"
+	"encoding/base64"
+	"encoding/pem"
+	"encoding/xml"
+	"errors"
+	"fmt"
+	"math/big"
+	"net/url"
+	"time"
+
+	"code.gitea.io/gitea/models/auth"
+	"code.gitea.io/gitea/modules/json"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+
+	saml2 "github.com/russellhaering/gosaml2"
+	"github.com/russellhaering/gosaml2/types"
+	dsig "github.com/russellhaering/goxmldsig"
+)
+
+// Source holds configuration for the SAML login source.
+type Source struct {
+	// IdentityProviderMetadata description: The SAML Identity Provider metadata XML contents (for static configuration of the SAML Service Provider). The value of this field should be an XML document whose root element is `<EntityDescriptor>` or `<EntityDescriptors>`. To escape the value into a JSON string, you may want to use a tool like https://json-escape-text.now.sh.
+	IdentityProviderMetadata string
+	// IdentityProviderMetadataURL description: The SAML Identity Provider metadata URL (for dynamic configuration of the SAML Service Provider).
+	IdentityProviderMetadataURL string
+	// InsecureSkipAssertionSignatureValidation description: Whether the Service Provider should (insecurely) accept assertions from the Identity Provider without a valid signature.
+	InsecureSkipAssertionSignatureValidation bool
+	// NameIDFormat description: The SAML NameID format to use when performing user authentication.
+	NameIDFormat NameIDFormat
+	// ServiceProviderCertificate description: The SAML Service Provider certificate in X.509 encoding (begins with "-----BEGIN CERTIFICATE-----"). This certificate is used by the Identity Provider to validate the Service Provider's AuthnRequests and LogoutRequests. It corresponds to the Service Provider's private key (`serviceProviderPrivateKey`). To escape the value into a JSON string, you may want to use a tool like https://json-escape-text.now.sh.
+	ServiceProviderCertificate string
+	// ServiceProviderIssuer description: The SAML Service Provider name, used to identify this Service Provider. This is required if the "externalURL" field is not set (as the SAML metadata endpoint is computed as "<externalURL>.auth/saml/metadata"), or when using multiple SAML authentication providers.
+	ServiceProviderIssuer string
+	// ServiceProviderPrivateKey description: The SAML Service Provider private key in PKCS#8 encoding (begins with "-----BEGIN PRIVATE KEY-----"). This private key is used to sign AuthnRequests and LogoutRequests. It corresponds to the Service Provider's certificate (`serviceProviderCertificate`). To escape the value into a JSON string, you may want to use a tool like https://json-escape-text.now.sh.
+	ServiceProviderPrivateKey string
+
+	CallbackURL string
+	IconURL     string
+
+	// EmailAssertionKey description: Assertion key for user.Email
+	EmailAssertionKey string
+	// NameAssertionKey description: Assertion key for user.NickName
+	NameAssertionKey string
+	// UsernameAssertionKey description: Assertion key for user.Name
+	UsernameAssertionKey string
+
+	// reference to the authSource
+	authSource *auth.Source
+
+	samlSP *saml2.SAMLServiceProvider
+}
+
+func GenerateSAMLSPKeypair() (string, string, error) {
+	key, err := rsa.GenerateKey(rand.Reader, 4096)
+	if err != nil {
+		return "", "", err
+	}
+
+	keyBytes := x509.MarshalPKCS1PrivateKey(key)
+	keyPem := pem.EncodeToMemory(
+		&pem.Block{
+			Type:  "RSA PRIVATE KEY",
+			Bytes: keyBytes,
+		},
+	)
+
+	now := time.Now()
+
+	template := &x509.Certificate{
+		SerialNumber: big.NewInt(0),
+		NotBefore:    now.Add(-5 * time.Minute),
+		NotAfter:     now.Add(365 * 24 * time.Hour),
+
+		KeyUsage:              x509.KeyUsageDigitalSignature,
+		ExtKeyUsage:           []x509.ExtKeyUsage{},
+		BasicConstraintsValid: true,
+	}
+
+	certificate, err := x509.CreateCertificate(rand.Reader, template, template, &key.PublicKey, key)
+	if err != nil {
+		return "", "", err
+	}
+
+	certPem := pem.EncodeToMemory(
+		&pem.Block{
+			Type:  "CERTIFICATE",
+			Bytes: certificate,
+		},
+	)
+
+	return string(keyPem), string(certPem), nil
+}
+
+func (source *Source) initSAMLSp() error {
+	source.CallbackURL = setting.AppURL + "user/saml/" + url.PathEscape(source.authSource.Name) + "/acs"
+
+	idpMetadata, err := readIdentityProviderMetadata(context.Background(), source)
+	if err != nil {
+		return err
+	}
+	{
+		if source.IdentityProviderMetadataURL != "" {
+			log.Trace(fmt.Sprintf("Identity Provider metadata: %s", source.IdentityProviderMetadataURL), string(idpMetadata))
+		}
+	}
+
+	metadata := &types.EntityDescriptor{}
+	err = xml.Unmarshal(idpMetadata, metadata)
+	if err != nil {
+		return err
+	}
+
+	certStore := dsig.MemoryX509CertificateStore{
+		Roots: []*x509.Certificate{},
+	}
+
+	if metadata.IDPSSODescriptor == nil {
+		return errors.New("saml idp metadata missing IDPSSODescriptor")
+	}
+
+	for _, kd := range metadata.IDPSSODescriptor.KeyDescriptors {
+		for idx, xcert := range kd.KeyInfo.X509Data.X509Certificates {
+			if xcert.Data == "" {
+				return fmt.Errorf("metadata certificate(%d) must not be empty", idx)
+			}
+			certData, err := base64.StdEncoding.DecodeString(xcert.Data)
+			if err != nil {
+				return err
+			}
+
+			idpCert, err := x509.ParseCertificate(certData)
+			if err != nil {
+				return err
+			}
+
+			certStore.Roots = append(certStore.Roots, idpCert)
+		}
+	}
+
+	var keyStore dsig.X509KeyStore
+
+	if source.ServiceProviderCertificate != "" && source.ServiceProviderPrivateKey != "" {
+		keyPair, err := tls.X509KeyPair([]byte(source.ServiceProviderCertificate), []byte(source.ServiceProviderPrivateKey))
+		if err != nil {
+			return err
+		}
+		keyPair.Leaf, err = x509.ParseCertificate(keyPair.Certificate[0])
+		if err != nil {
+			return err
+		}
+		keyStore = dsig.TLSCertKeyStore(keyPair)
+	}
+
+	source.samlSP = &saml2.SAMLServiceProvider{
+		IdentityProviderSSOURL:      metadata.IDPSSODescriptor.SingleSignOnServices[0].Location,
+		IdentityProviderIssuer:      metadata.EntityID,
+		AudienceURI:                 setting.AppURL + "user/saml/" + url.PathEscape(source.authSource.Name) + "/metadata",
+		AssertionConsumerServiceURL: source.CallbackURL,
+		SkipSignatureValidation:     source.InsecureSkipAssertionSignatureValidation,
+		NameIdFormat:                source.NameIDFormat.String(),
+		IDPCertificateStore:         &certStore,
+		SignAuthnRequests:           source.ServiceProviderCertificate != "" && source.ServiceProviderPrivateKey != "",
+		SPKeyStore:                  keyStore,
+		ServiceProviderIssuer:       setting.AppURL + "user/saml/" + url.PathEscape(source.authSource.Name) + "/metadata",
+	}
+
+	return nil
+}
+
+// FromDB fills up a SAML from serialized format.
+func (source *Source) FromDB(bs []byte) error {
+	if err := json.UnmarshalHandleDoubleEncode(bs, &source); err != nil {
+		return err
+	}
+
+	return source.initSAMLSp()
+}
+
+// ToDB exports a SAML to a serialized format.
+func (source *Source) ToDB() ([]byte, error) {
+	return json.Marshal(source)
+}
+
+// SetAuthSource sets the related AuthSource
+func (source *Source) SetAuthSource(authSource *auth.Source) {
+	source.authSource = authSource
+}
+
+func init() {
+	auth.RegisterTypeConfig(auth.SAML, &Source{})
+}
--- a/services/auth/source/saml/source_authenticate.go
+++ b/services/auth/source/saml/source_authenticate.go
@ -0,0 +1,16 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+import (
+	"context"
+
+	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/services/auth/source/db"
+)
+
+// Authenticate falls back to the db authenticator
+func (source *Source) Authenticate(ctx context.Context, user *user_model.User, login, password string) (*user_model.User, error) {
+	return db.Authenticate(ctx, user, login, password)
+}
--- a/services/auth/source/saml/source_callout.go
+++ b/services/auth/source/saml/source_callout.go
@ -0,0 +1,89 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/markbates/goth"
+)
+
+// Callout redirects request/response pair to authenticate against the provider
+func (source *Source) Callout(request *http.Request, response http.ResponseWriter) error {
+	samlRWMutex.RLock()
+	defer samlRWMutex.RUnlock()
+	if _, ok := providers[source.authSource.Name]; !ok {
+		return fmt.Errorf("no provider for this saml")
+	}
+
+	authURL, err := providers[source.authSource.Name].samlSP.BuildAuthURL("")
+	if err == nil {
+		http.Redirect(response, request, authURL, http.StatusTemporaryRedirect)
+	}
+	return err
+}
+
+// Callback handles SAML 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) (goth.User, error) {
+	samlRWMutex.RLock()
+	defer samlRWMutex.RUnlock()
+
+	user := goth.User{
+		Provider: source.authSource.Name,
+	}
+	samlResponse := request.FormValue("SAMLResponse")
+	assertions, err := source.samlSP.RetrieveAssertionInfo(samlResponse)
+	if err != nil {
+		return user, err
+	}
+
+	if assertions.WarningInfo.OneTimeUse {
+		return user, fmt.Errorf("SAML response contains one time use warning")
+	}
+
+	if assertions.WarningInfo.ProxyRestriction != nil {
+		return user, fmt.Errorf("SAML response contains proxy restriction warning: %v", assertions.WarningInfo.ProxyRestriction)
+	}
+
+	if assertions.WarningInfo.NotInAudience {
+		return user, fmt.Errorf("SAML response contains audience warning")
+	}
+
+	if assertions.WarningInfo.InvalidTime {
+		return user, fmt.Errorf("SAML response contains invalid time warning")
+	}
+
+	samlMap := make(map[string]string)
+	for key, value := range assertions.Values {
+		keyParsed := strings.ToLower(key[strings.LastIndex(key, "/")+1:]) // Uses the trailing slug as the key name.
+		valueParsed := value.Values[0].Value
+		samlMap[keyParsed] = valueParsed
+
+	}
+
+	user.UserID = assertions.NameID
+	if user.UserID == "" {
+		return user, fmt.Errorf("no nameID found in SAML response")
+	}
+
+	// email
+	if _, ok := samlMap[source.EmailAssertionKey]; !ok {
+		user.Email = samlMap[source.EmailAssertionKey]
+	}
+	// name
+	if _, ok := samlMap[source.NameAssertionKey]; !ok {
+		user.NickName = samlMap[source.NameAssertionKey]
+	}
+	// username
+	if _, ok := samlMap[source.UsernameAssertionKey]; !ok {
+		user.Name = samlMap[source.UsernameAssertionKey]
+	}
+
+	// TODO: utilize groups once mapping is supported
+
+	return user, nil
+}
--- a/services/auth/source/saml/source_metadata.go
+++ b/services/auth/source/saml/source_metadata.go
@ -0,0 +1,32 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+import (
+	"encoding/xml"
+	"fmt"
+	"net/http"
+)
+
+// Metadata redirects request/response pair to authenticate against the provider
+func (source *Source) Metadata(request *http.Request, response http.ResponseWriter) error {
+	samlRWMutex.RLock()
+	defer samlRWMutex.RUnlock()
+	if _, ok := providers[source.authSource.Name]; !ok {
+		return fmt.Errorf("provider does not exist")
+	}
+
+	metadata, err := providers[source.authSource.Name].samlSP.Metadata()
+	if err != nil {
+		return err
+	}
+	buf, err := xml.Marshal(metadata)
+	if err != nil {
+		return err
+	}
+
+	response.Header().Set("Content-Type", "application/samlmetadata+xml; charset=utf-8")
+	_, _ = response.Write(buf)
+	return nil
+}
--- a/services/auth/source/saml/source_register.go
+++ b/services/auth/source/saml/source_register.go
@ -0,0 +1,23 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package saml
+
+// RegisterSource causes an OAuth2 configuration to be registered
+func (source *Source) RegisterSource() error {
+	samlRWMutex.Lock()
+	defer samlRWMutex.Unlock()
+	if err := source.initSAMLSp(); err != nil {
+		return err
+	}
+	providers[source.authSource.Name] = *source
+	return nil
+}
+
+// UnregisterSource causes an SAML configuration to be unregistered
+func (source *Source) UnregisterSource() error {
+	samlRWMutex.Lock()
+	defer samlRWMutex.Unlock()
+	delete(providers, source.authSource.Name)
+	return nil
+}
--- a/services/externalaccount/link.go
+++ b/services/externalaccount/link.go
@ -7,9 +7,8 @@ import (
 	"context"
 	"fmt"

+	"code.gitea.io/gitea/models/auth"
 	user_model "code.gitea.io/gitea/models/user"
-
-	"github.com/markbates/goth"
 )

 // Store represents a thing that stores things
@ -21,10 +20,12 @@ type Store interface {

 // LinkAccountFromStore links the provided user with a stored external user
 func LinkAccountFromStore(ctx context.Context, store Store, user *user_model.User) error {
-	gothUser := store.Get("linkAccountGothUser")
-	if gothUser == nil {
+	externalLinkUserInterface := store.Get("linkAccountUser")
+	if externalLinkUserInterface == nil {
 		return fmt.Errorf("not in LinkAccount session")
 	}

-	return LinkAccountToUser(ctx, user, gothUser.(goth.User))
+	externalLinkUser := externalLinkUserInterface.(auth.LinkAccountUser)
+
+	return LinkAccountToUser(ctx, user, externalLinkUser.GothUser, externalLinkUser.Type)
 }
--- a/services/externalaccount/user.go
+++ b/services/externalaccount/user.go
@ -16,8 +16,8 @@ import (
 	"github.com/markbates/goth"
 )

-func toExternalLoginUser(ctx context.Context, user *user_model.User, gothUser goth.User) (*user_model.ExternalLoginUser, error) {
-	authSource, err := auth.GetActiveOAuth2SourceByName(ctx, gothUser.Provider)
+func toExternalLoginUser(ctx context.Context, user *user_model.User, gothUser goth.User, authType auth.Type) (*user_model.ExternalLoginUser, error) {
+	authSource, err := auth.GetActiveAuthSourceByName(ctx, gothUser.Provider, authType)
 	if err != nil {
 		return nil, err
 	}
@ -43,8 +43,8 @@ func toExternalLoginUser(ctx context.Context, user *user_model.User, gothUser go
 }

 // LinkAccountToUser link the gothUser to the user
-func LinkAccountToUser(ctx context.Context, user *user_model.User, gothUser goth.User) error {
-	externalLoginUser, err := toExternalLoginUser(ctx, user, gothUser)
+func LinkAccountToUser(ctx context.Context, user *user_model.User, gothUser goth.User, authType auth.Type) error {
+	externalLoginUser, err := toExternalLoginUser(ctx, user, gothUser, authType)
 	if err != nil {
 		return err
 	}
@ -71,8 +71,8 @@ func LinkAccountToUser(ctx context.Context, user *user_model.User, gothUser goth
 }

 // UpdateExternalUser updates external user's information
-func UpdateExternalUser(ctx context.Context, user *user_model.User, gothUser goth.User) error {
-	externalLoginUser, err := toExternalLoginUser(ctx, user, gothUser)
+func UpdateExternalUser(ctx context.Context, user *user_model.User, gothUser goth.User, authType auth.Type) error {
+	externalLoginUser, err := toExternalLoginUser(ctx, user, gothUser, authType)
 	if err != nil {
 		return err
 	}
--- a/services/forms/auth_form.go
+++ b/services/forms/auth_form.go
@ -1,3 +1,4 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
 // Copyright 2014 The Gogs Authors. All rights reserved.
 // SPDX-License-Identifier: MIT

@ -15,7 +16,7 @@ import (
 // AuthenticationForm form for authentication
 type AuthenticationForm struct {
 	ID                            int64
-	Type                          int    `binding:"Range(2,7)"`
+	Type                          int    `binding:"Range(2,9)"`
 	Name                          string `binding:"Required;MaxSize(30)"`
 	Host                          string
 	Port                          int
@ -82,6 +83,18 @@ type AuthenticationForm struct {
 	SSPIDefaultLanguage           string
 	GroupTeamMap                  string `binding:"ValidGroupTeamMap"`
 	GroupTeamMapRemoval           bool
+
+	// SAML Settings
+	NameIDFormat                             int
+	IdentityProviderMetadata                 string
+	IdentityProviderMetadataURL              string
+	InsecureSkipAssertionSignatureValidation bool
+	ServiceProviderCertificate               string
+	ServiceProviderPrivateKey                string
+	EmailAssertionKey                        string
+	NameAssertionKey                         string
+	UsernameAssertionKey                     string
+	SAMLIconURL                              string
 }

 // Validate validates fields
--- a/templates/admin/auth/edit.tmpl
+++ b/templates/admin/auth/edit.tmpl
@ -367,6 +367,69 @@
 					</div>
 				{{end}}

+				<!-- SAML -->
+				{{if .Source.IsSAML}}
+					{{$cfg:=.Source.Cfg}}
+					<div class="inline required field">
+						<label>{{ctx.Locale.Tr "admin.auths.saml_nameidformat"}}</label>
+						<div class="ui selection type dropdown">
+							<input type="hidden" id="name_id_format" name="name_id_format" value="{{$cfg.NameIDFormat}}">
+							<div class="text">{{.CurrentNameIDFormat}}</div>
+							{{svg "octicon-triangle-down" 14 "dropdown icon"}}
+							<div class="menu">
+								{{range .NameIDFormats}}
+									<div class="item" data-value="{{.Type.Int}}">{{.Name}}</div>
+								{{end}}
+							</div>
+						</div>
+					</div>
+
+					<div class="optional field">
+						<label for="saml_icon_url">{{ctx.Locale.Tr "admin.auths.saml_icon_url"}}</label>
+						<input id="saml_icon_url" name="saml_icon_url" value="{{$cfg.IconURL}}">
+					</div>
+
+					<div class="field">
+						<label for="identity_provider_metadata_url">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_metadata_url"}}</label>
+						<input id="identity_provider_metadata_url" name="identity_provider_metadata_url" value="{{$cfg.IdentityProviderMetadataURL}}">
+					</div>
+					<div class="field">
+						<label for="identity_provider_metadata">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_metadata"}}</label>
+						<textarea rows=2 id="identity_provider_metadata" name="identity_provider_metadata">{{$cfg.IdentityProviderMetadata}}</textarea>
+					</div>
+
+					<div class="inline field">
+						<div class="ui checkbox">
+							<label><strong>{{ctx.Locale.Tr "admin.auths.saml_insecure_skip_assertion_signature_validation"}}</strong></label>
+							<input name="insecure_skip_assertion_signature_validation" type="checkbox" {{if $cfg.InsecureSkipAssertionSignatureValidation}}checked{{end}}>
+						</div>
+					</div>
+
+					<div class=" field">
+						<label for="service_provider_certificate">{{ctx.Locale.Tr "admin.auths.saml_service_provider_certificate"}}</label>
+						<textarea rows=2 id="service_provider_certificate" name="service_provider_certificate">{{$cfg.ServiceProviderCertificate}}</textarea>
+					</div>
+					<div class=" field">
+						<label for="service_provider_private_key">{{ctx.Locale.Tr "admin.auths.saml_service_provider_private_key"}}</label>
+						<textarea rows=2 id="service_provider_private_key" name="service_provider_private_key">{{$cfg.ServiceProviderPrivateKey}}</textarea>
+					</div>
+
+					<div class="field">
+						<label for="email_assertion_key">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_email_assertion_key"}}</label>
+						<input id="email_assertion_key" name="email_assertion_key" value="{{if not $cfg.EmailAssertionKey}}http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress{{else}}{{$cfg.EmailAssertionKey}}{{end}}">
+					</div>
+
+					<div class="field">
+						<label for="name_assertion_key">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_name_assertion_key"}}</label>
+						<input id="name_assertion_key" name="name_assertion_key" value="{{if not $cfg.NameAssertionKey}}http://schemas.xmlsoap.org/claims/CommonName{{else}}{{$cfg.NameAssertionKey}}{{end}}">
+					</div>
+
+					<div class="field">
+						<label for="username_assertion_key">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_username_assertion_key"}}</label>
+						<input id="username_assertion_key" name="username_assertion_key" value="{{if not $cfg.UsernameAssertionKey}}http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name{{else}}{{$cfg.UsernameAssertionKey}}{{end}}">
+					</div>
+				{{end}}
+
 				<!-- SSPI -->
 				{{if .Source.IsSSPI}}
 					{{$cfg:=.Source.Cfg}}
@ -441,6 +504,9 @@
 			<h5>GMail Settings:</h5>
 			<p>Host: smtp.gmail.com, Port: 587, Enable TLS Encryption: true</p>

+			<h5>SAML Settings:</h5>
+			<p>{{ctx.Locale.Tr "admin.auths.tips.saml"}}</p>
+
 			<h5 class="oauth2">{{ctx.Locale.Tr "admin.auths.tips.oauth2.general"}}:</h5>
 			<p class="oauth2">{{ctx.Locale.Tr "admin.auths.tips.oauth2.general.tip"}} <b id="oauth2-callback-url"></b></p>
 		</div>
--- a/templates/admin/auth/new.tmpl
+++ b/templates/admin/auth/new.tmpl
@ -53,6 +53,9 @@
 				<!-- SSPI -->
 				{{template "admin/auth/source/sspi" .}}

+				<!-- SAML -->
+				{{template "admin/auth/source/saml" .}}
+
 				<div class="ldap field">
 					<div class="ui checkbox">
 						<label><strong>{{ctx.Locale.Tr "admin.auths.attributes_in_bind"}}</strong></label>
@ -85,6 +88,9 @@
 			<h5>GMail Settings:</h5>
 			<p>Host: smtp.gmail.com, Port: 587, Enable TLS Encryption: true</p>

+			<h5>SAML Settings:</h5>
+			<p>{{ctx.Locale.Tr "admin.auths.tips.saml"}}</p>
+
 			<h5 class="oauth2">{{ctx.Locale.Tr "admin.auths.tips.oauth2.general"}}:</h5>
 			<p class="oauth2">{{ctx.Locale.Tr "admin.auths.tips.oauth2.general.tip"}} <b id="oauth2-callback-url"></b></p>

--- a/templates/admin/auth/source/saml.tmpl
+++ b/templates/admin/auth/source/saml.tmpl
@ -0,0 +1,62 @@
+<div class="saml field {{if not (eq .type 8)}}gt-hidden{{end}}">
+
+	<div class="inline required field">
+		<label>{{ctx.Locale.Tr "admin.auths.saml_nameidformat"}}</label>
+		<div class="ui selection type dropdown">
+			<input type="hidden" id="name_id_format" name="name_id_format" value="{{.name_id_format}}">
+			<div class="text">{{.CurrentNameIDFormat}}</div>
+			{{svg "octicon-triangle-down" 14 "dropdown icon"}}
+			<div class="menu">
+				{{range .NameIDFormats}}
+					<div class="item" data-value="{{.Type.Int}}">{{.Name}}</div>
+				{{end}}
+			</div>
+		</div>
+	</div>
+
+	<div class="optional field">
+		<label for="saml_icon_url">{{ctx.Locale.Tr "admin.auths.saml_icon_url"}}</label>
+		<input id="saml_icon_url" name="saml_icon_url" value="{{.SAMLIconURL}}">
+	</div>
+
+	<div class="field">
+		<label for="identity_provider_metadata_url">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_metadata_url"}}</label>
+		<input id="identity_provider_metadata_url" name="identity_provider_metadata_url" value="{{.IdentityProviderMetadataURL}}">
+	</div>
+	<div class="field">
+		<label for="identity_provider_metadata">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_metadata"}}</label>
+		<textarea rows=2 id="identity_provider_metadata" name="identity_provider_metadata" value="{{.IdentityProviderMetadata}}"></textarea>
+	</div>
+
+	<div class="inline field">
+		<div class="ui checkbox">
+			<label><strong>{{ctx.Locale.Tr "admin.auths.saml_insecure_skip_assertion_signature_validation"}}</strong></label>
+			<input name="insecure_skip_assertion_signature_validation" type="checkbox" {{if .InsecureSkipAssertionSignatureValidation}}checked{{end}}>
+		</div>
+	</div>
+
+	<div class="field">
+		<label for="service_provider_certificate">{{ctx.Locale.Tr "admin.auths.saml_service_provider_certificate"}}</label>
+		<textarea rows=2 id="service_provider_certificate" name="service_provider_certificate" value="{{.ServiceProviderCertificate}}"></textarea>
+	</div>
+	<div class="field">
+		<label for="service_provider_private_key">{{ctx.Locale.Tr "admin.auths.saml_service_provider_private_key"}}</label>
+		<textarea rows=2 id="service_provider_private_key" name="service_provider_private_key" value="{{.ServiceProviderPrivateKey}}"></textarea>
+	</div>
+
+	<div class="field">
+		<label for="email_assertion_key">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_email_assertion_key"}}</label>
+		<input id="email_assertion_key" name="email_assertion_key" value="{{if not .EmailAssertionKey}}http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress{{else}}{{.EmailAssertionKey}}{{end}}">
+	</div>
+
+	<div class="field">
+		<label for="name_assertion_key">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_name_assertion_key"}}</label>
+		<input id="name_assertion_key" name="name_assertion_key" value="{{if not .NameAssertionKey}}http://schemas.xmlsoap.org/claims/CommonName{{else}}{{.NameAssertionKey}}{{end}}">
+	</div>
+
+	<div class="field">
+		<label for="username_assertion_key">{{ctx.Locale.Tr "admin.auths.saml_identity_provider_username_assertion_key"}}</label>
+		<input id="username_assertion_key" name="username_assertion_key" value="{{if not .UsernameAssertionKey}}http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name{{else}}{{.UsernameAssertionKey}}{{end}}">
+	</div>
+
+</div>
--- a/templates/user/auth/signin_inner.tmpl
+++ b/templates/user/auth/signin_inner.tmpl
@ -69,5 +69,22 @@
 		</div>
 	</div>
 	{{end}}
+	{{if .SAMLProviders}}
+	<div class="divider divider-text">
+		{{.locale.Tr "sign_in_or"}}
+	</div>
+	<div id="saml-login-navigator" class="gt-py-2">
+		<div class="gt-df gt-fc gt-jc">
+			<div id="saml-login-navigator-inner" class="gt-df gt-fc gt-fw gt-ac gt-gap-3">
+				{{range $provider := .SAMLProviders}}
+					<a class="{{$provider.Name}} ui button gt-df gt-ac gt-jc gt-py-3 saml-login-link" href="{{AppSubUrl}}/user/saml/{{$provider.Name}}">
+						{{.IconHTML 28}}
+						{{ctx.Locale.Tr "sign_in_with_provider" $provider.Name}}
+					</a>
+				{{end}}
+			</div>
+		</div>
+	</div>
+	{{end}}
 	</form>
 </div>
--- a/tests/integration/README.md
+++ b/tests/integration/README.md
@ -110,3 +110,20 @@ SLOW_FLUSH = 5S ; 5s is the default value
 ```bash
 GITEA_SLOW_TEST_TIME="10s" GITEA_SLOW_FLUSH_TIME="5s" make test-sqlite
 ```
+
+## Running SimpleSAML for testing SAML locally
+
+```shell
+docker run \
+-p 8080:8080 \
+-p 8443:8443 \
+-e SIMPLESAMLPHP_SP_ENTITY_ID=http://localhost:3003/user/saml/test-sp/metadata \
+-e SIMPLESAMLPHP_SP_ASSERTION_CONSUMER_SERVICE=http://localhost:3003/user/saml/test-sp/acs \
+-e SIMPLESAMLPHP_SP_SINGLE_LOGOUT_SERVICE=http://localhost:3003/user/saml/test-sp/acs \
+--add-host=localhost:192.168.65.2 \
+-d allspice/simple-saml
+```
+
+```shell
+TEST_SIMPLESAML_URL=localhost:8080 make test-sqlite#TestSAMLRegistration
+```
--- a/tests/integration/saml_test.go
+++ b/tests/integration/saml_test.go
@ -0,0 +1,150 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package integration
+
+import (
+	"crypto/tls"
+	"crypto/x509"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/cookiejar"
+	"net/url"
+	"os"
+	"regexp"
+	"strings"
+	"testing"
+	"time"
+
+	"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/setting"
+	"code.gitea.io/gitea/modules/test"
+	"code.gitea.io/gitea/services/auth/source/saml"
+	"code.gitea.io/gitea/tests"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSAMLRegistration(t *testing.T) {
+	defer tests.PrepareTestEnv(t)()
+
+	samlURL := "localhost:8080"
+
+	if os.Getenv("CI") == "" || !setting.Database.Type.IsPostgreSQL() {
+		// Make it possible to run tests against a local simplesaml instance
+		samlURL = os.Getenv("TEST_SIMPLESAML_URL")
+		if samlURL == "" {
+			t.Skip("TEST_SIMPLESAML_URL not set and not running in CI")
+			return
+		}
+	}
+
+	privateKey, cert, err := saml.GenerateSAMLSPKeypair()
+	assert.NoError(t, err)
+
+	// verify that the keypair can be parsed
+	keyPair, err := tls.X509KeyPair([]byte(cert), []byte(privateKey))
+	assert.NoError(t, err)
+	keyPair.Leaf, err = x509.ParseCertificate(keyPair.Certificate[0])
+	assert.NoError(t, err)
+
+	assert.NoError(t, auth.CreateSource(db.DefaultContext, &auth.Source{
+		Type:          auth.SAML,
+		Name:          "test-sp",
+		IsActive:      true,
+		IsSyncEnabled: false,
+		Cfg: &saml.Source{
+			IdentityProviderMetadata:                 "",
+			IdentityProviderMetadataURL:              fmt.Sprintf("http://%s/simplesaml/saml2/idp/metadata.php", samlURL),
+			InsecureSkipAssertionSignatureValidation: false,
+			NameIDFormat:                             4,
+			ServiceProviderCertificate:               "", // SimpleSAMLPhp requires that the SP certificate be specified in the server configuration rather than SP metadata
+			ServiceProviderPrivateKey:                "",
+			EmailAssertionKey:                        "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress",
+			NameAssertionKey:                         "http://schemas.xmlsoap.org/claims/CommonName",
+			UsernameAssertionKey:                     "http://schemas.xmlsoap.org/ws/2005/05/identity/claims/name",
+			IconURL:                                  "",
+		},
+	}))
+
+	// check the saml metadata url
+	req := NewRequest(t, "GET", "/user/saml/test-sp/metadata")
+	MakeRequest(t, req, http.StatusOK)
+
+	req = NewRequest(t, "GET", "/user/saml/test-sp")
+	resp := MakeRequest(t, req, http.StatusTemporaryRedirect)
+
+	jar, err := cookiejar.New(nil)
+	assert.NoError(t, err)
+
+	client := http.Client{
+		Timeout: 30 * time.Second,
+		Jar:     jar,
+	}
+
+	httpReq, err := http.NewRequest("GET", test.RedirectURL(resp), nil)
+	assert.NoError(t, err)
+
+	var formRedirectURL *url.URL
+	client.CheckRedirect = func(req *http.Request, via []*http.Request) error {
+		// capture the redirected destination to use in POST request
+		formRedirectURL = req.URL
+		return nil
+	}
+
+	res, err := client.Do(httpReq)
+	client.CheckRedirect = nil
+	assert.NoError(t, err)
+	assert.Equal(t, http.StatusOK, res.StatusCode)
+	assert.NotNil(t, formRedirectURL)
+
+	form := url.Values{
+		"username": {"user1"},
+		"password": {"user1pass"},
+	}
+
+	httpReq, err = http.NewRequest("POST", formRedirectURL.String(), strings.NewReader(form.Encode()))
+	assert.NoError(t, err)
+	httpReq.Header.Add("Content-Type", "application/x-www-form-urlencoded")
+
+	res, err = client.Do(httpReq)
+	assert.NoError(t, err)
+	assert.Equal(t, http.StatusOK, res.StatusCode)
+
+	body, err := io.ReadAll(res.Body)
+	assert.NoError(t, err)
+
+	samlResMatcher := regexp.MustCompile(`<input.*?name="SAMLResponse".*?value="([^"]+)".*?>`)
+	matches := samlResMatcher.FindStringSubmatch(string(body))
+	assert.Len(t, matches, 2)
+	assert.NoError(t, res.Body.Close())
+
+	session := emptyTestSession(t)
+
+	req = NewRequestWithValues(t, "POST", "/user/saml/test-sp/acs", map[string]string{
+		"SAMLResponse": matches[1],
+	})
+	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	assert.Equal(t, test.RedirectURL(resp), "/user/link_account")
+
+	csrf := GetCSRF(t, session, test.RedirectURL(resp))
+
+	// link the account
+	req = NewRequestWithValues(t, "POST", "/user/link_account_signup", map[string]string{
+		"_csrf":     csrf,
+		"user_name": "samluser",
+		"email":     "saml@example.com",
+	})
+
+	resp = session.MakeRequest(t, req, http.StatusSeeOther)
+	assert.Equal(t, test.RedirectURL(resp), "/")
+
+	// verify that the user was created
+	u, err := user_model.GetUserByEmail(db.DefaultContext, "saml@example.com")
+	assert.NoError(t, err)
+	assert.NotNil(t, u)
+	assert.Equal(t, "samluser", u.Name)
+}
--- a/web_src/js/features/admin/common.js
+++ b/web_src/js/features/admin/common.js
@ -103,9 +103,9 @@ export function initAdminCommon() {
  // New authentication
  if ($('.admin.new.authentication').length > 0) {
    $('#auth_type').on('change', function () {
-      hideElem($('.ldap, .dldap, .smtp, .pam, .oauth2, .has-tls, .search-page-size, .sspi'));
+      hideElem($('.ldap, .dldap, .smtp, .pam, .oauth2, .has-tls, .search-page-size, .sspi, .saml'));

-      $('.ldap input[required], .binddnrequired input[required], .dldap input[required], .smtp input[required], .pam input[required], .oauth2 input[required], .has-tls input[required], .sspi input[required]').removeAttr('required');
+      $('.ldap input[required], .binddnrequired input[required], .dldap input[required], .smtp input[required], .pam input[required], .oauth2 input[required], .has-tls input[required], .sspi input[required], .saml input[required]').removeAttr('required');
      $('.binddnrequired').removeClass('required');

      const authType = $(this).val();
@ -137,6 +137,10 @@ export function initAdminCommon() {
          showElem($('.sspi'));
          $('.sspi div.required input').attr('required', 'required');
          break;
+        case '8': // SAML
+          showElem($('.saml'));
+          $('.saml div.required input').attr('required', 'required');
+          break;
      }
      if (authType === '2' || authType === '5') {
        onSecurityProtocolChange();
--- a/web_src/js/features/user-auth.js
+++ b/web_src/js/features/user-auth.js
@ -20,3 +20,24 @@ export function initUserAuthOauth2() {
    });
  }
 }
+
+export function initUserAuthSAML() {
+  const outer = document.getElementById('saml-login-navigator');
+  if (!outer) return;
+  const inner = document.getElementById('saml-login-navigator-inner');
+
+  checkAppUrl();
+
+  for (const link of outer.querySelectorAll('.saml-login-link')) {
+    link.addEventListener('click', () => {
+      inner.classList.add('gt-invisible');
+      outer.classList.add('is-loading');
+      setTimeout(() => {
+        // recover previous content to let user try again
+        // usually redirection will be performed before this action
+        outer.classList.remove('is-loading');
+        inner.classList.remove('gt-invisible');
+      }, 5000);
+    });
+  }
+}
--- a/web_src/js/index.js
+++ b/web_src/js/index.js
@ -23,7 +23,10 @@ import {initFindFileInRepo} from './features/repo-findfile.js';
 import {initCommentContent, initMarkupContent} from './markup/content.js';
 import {initPdfViewer} from './render/pdf.js';

-import {initUserAuthOauth2} from './features/user-auth.js';
+import {
+  initUserAuthOauth2,
+  initUserAuthSAML
+} from './features/user-auth.js';
 import {
  initRepoIssueDue,
  initRepoIssueReferenceRepositorySearch,
@ -179,6 +182,7 @@ onDomReady(() => {
  initCaptcha();

  initUserAuthOauth2();
+  initUserAuthSAML();
  initUserAuthWebAuthn();
  initUserAuthWebAuthnRegister();
  initUserSettings();