Allow use of the preferred_username OIDC claim

Previously, Headscale would only use the `email` OIDC
claim to set the Headscale user. In certain cases
(self-hosted SSO), it may be useful to instead use the
`preferred_username` to set the Headscale username.
This also closes juanfont#938.

This adds a config setting to use this claim instead.
The OIDC docs have been updated to include this entry as well.
In addition, this adds an Authelia OIDC example to the docs.

Added OIDC claim integration tests.

Updated the MockOIDC wrapper to take an environment variable that
lets you set the username/email claims to return.

Added two integration tests, TestOIDCEmailGrant and
TestOIDCUsernameGrant, which check the username by checking the FQDN of
clients.

Updated the HTML template shown after OIDC login to show whatever
username is used, based on the Headscale settings.

.github/workflows/test-integration-v2-TestOIDCEmailGrant.yaml

@@ -0,0 +1,57 @@
+# DO NOT EDIT, generated with cmd/gh-action-integration-generator/main.go
+# To regenerate, run "go generate" in cmd/gh-action-integration-generator/
+
+name: Integration Test v2 - TestOIDCEmailGrant
+
+on: [pull_request]
+
+concurrency:
+  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 2
+
+      - name: Get changed files
+        id: changed-files
+        uses: tj-actions/changed-files@v34
+        with:
+          files: |
+            *.nix
+            go.*
+            **/*.go
+            integration_test/
+            config-example.yaml
+
+      - uses: cachix/install-nix-action@v18
+        if: ${{ env.ACT }} || steps.changed-files.outputs.any_changed == 'true'
+
+      - name: Run general integration tests
+        if: steps.changed-files.outputs.any_changed == 'true'
+        run: |
+            nix develop --command -- docker run \
+              --tty --rm \
+              --volume ~/.cache/hs-integration-go:/go \
+              --name headscale-test-suite \
+              --volume $PWD:$PWD -w $PWD/integration \
+              --volume /var/run/docker.sock:/var/run/docker.sock \
+              --volume $PWD/control_logs:/tmp/control \
+              golang:1 \
+                go test ./... \
+                  -tags ts2019 \
+                  -failfast \
+                  -timeout 120m \
+                  -parallel 1 \
+                  -run "^TestOIDCEmailGrant$"
+
+      - uses: actions/upload-artifact@v3
+        if: always() && steps.changed-files.outputs.any_changed == 'true'
+        with:
+          name: logs
+          path: "control_logs/*.log"

.github/workflows/test-integration-v2-TestOIDCUsernameGrant.yaml

@@ -0,0 +1,57 @@
+# DO NOT EDIT, generated with cmd/gh-action-integration-generator/main.go
+# To regenerate, run "go generate" in cmd/gh-action-integration-generator/
+
+name: Integration Test v2 - TestOIDCUsernameGrant
+
+on: [pull_request]
+
+concurrency:
+  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 2
+
+      - name: Get changed files
+        id: changed-files
+        uses: tj-actions/changed-files@v34
+        with:
+          files: |
+            *.nix
+            go.*
+            **/*.go
+            integration_test/
+            config-example.yaml
+
+      - uses: cachix/install-nix-action@v18
+        if: ${{ env.ACT }} || steps.changed-files.outputs.any_changed == 'true'
+
+      - name: Run general integration tests
+        if: steps.changed-files.outputs.any_changed == 'true'
+        run: |
+            nix develop --command -- docker run \
+              --tty --rm \
+              --volume ~/.cache/hs-integration-go:/go \
+              --name headscale-test-suite \
+              --volume $PWD:$PWD -w $PWD/integration \
+              --volume /var/run/docker.sock:/var/run/docker.sock \
+              --volume $PWD/control_logs:/tmp/control \
+              golang:1 \
+                go test ./... \
+                  -tags ts2019 \
+                  -failfast \
+                  -timeout 120m \
+                  -parallel 1 \
+                  -run "^TestOIDCUsernameGrant$"
+
+      - uses: actions/upload-artifact@v3
+        if: always() && steps.changed-files.outputs.any_changed == 'true'
+        with:
+          name: logs
+          path: "control_logs/*.log"

cmd/headscale/cli/mockoidc.go

@@ -4,7 +4,9 @@ import (
 	"fmt"
 	"net"
 	"os"
+	"regexp"
 	"strconv"
+	"strings"
 	"time"
 
 	"github.com/oauth2-proxy/mockoidc"
@@ -64,14 +66,36 @@ func mockOIDC() error {
 		accessTTL = newTTL
 	}
 
+	mockUsers := os.Getenv("MOCKOIDC_USERS")
+	users := []mockoidc.User{}
+	if mockUsers != "" {
+		userStrings := strings.Split(mockUsers, ",")
+		userRe := regexp.MustCompile(`^\s*(?P<username>\S+)\s*<(?P<email>\S+@\S+)>\s*$`)
+		for _, v := range userStrings {
+			match := userRe.FindStringSubmatch(v)
+			if match != nil {
+				// Use the default mockoidc claims for other entries
+				users = append(users, &mockoidc.MockUser{
+					Subject:           "1234567890",
+					Email:             match[2],
+					PreferredUsername: match[1],
+					Phone:             "555-987-6543",
+					Address:           "123 Main Street",
+					Groups:            []string{"engineering", "design"},
+					EmailVerified:     true,
+				})
+			}
+		}
+	}
+
 	log.Info().Msgf("Access token TTL: %s", accessTTL)
 
 	port, err := strconv.Atoi(portStr)
 	if err != nil {
 		return err
 	}
 
-	mock, err := getMockOIDC(clientID, clientSecret)
+	mock, err := getMockOIDC(clientID, clientSecret, users)
 	if err != nil {
 		return err
 	}
@@ -93,7 +117,7 @@ func mockOIDC() error {
 	return nil
 }
 
-func getMockOIDC(clientID string, clientSecret string) (*mockoidc.MockOIDC, error) {
+func getMockOIDC(clientID string, clientSecret string, users []mockoidc.User) (*mockoidc.MockOIDC, error) {
 	keypair, err := mockoidc.NewKeypair(nil)
 	if err != nil {
 		return nil, err
@@ -111,5 +135,9 @@ func getMockOIDC(clientID string, clientSecret string) (*mockoidc.MockOIDC, erro
 		ErrorQueue:                    &mockoidc.ErrorQueue{},
 	}
 
+	for _, v := range users {
+		mock.QueueUser(v)
+	}
+
 	return &mock, nil
 }

config-example.yaml

@@ -304,6 +304,16 @@ unix_socket_permission: "0770"
 #   allowed_users:
 #     - alice@example.com
 #
+#   # By default, Headscale will use the OIDC email address claim to determine the username.
+#   # OIDC also returns a `preferred_username` claim.
+#   #
+#   # If `use_username_claim` is set to `true`, then the `preferred_username` claim will
+#   # be used instead to set the Headscale username.
+#   # If `use_username_claim` is set to `false`, then the `email` claim will be used
+#   # to derive the Headscale username (as modified by the `strip_email_domain` entry).
+#
+#   use_username_claim: false
+#
 #   # If `strip_email_domain` is set to `true`, the domain part of the username email address will be removed.
 #   # This will transform `first-name.last-name@example.com` to the user `first-name.last-name`
 #   # If `strip_email_domain` is set to `false` the domain part will NOT be removed resulting to the following

docs/oidc.md

@@ -43,6 +43,16 @@ oidc:
   allowed_users:
     - alice@example.com
 
+  # By default, Headscale will use the OIDC email address claim to determine the username.
+  # OIDC also returns a `preferred_username` claim.
+  #
+  # If `use_username_claim` is set to `true`, then the `preferred_username` claim will
+  # be used instead to set the Headscale username.
+  # If `use_username_claim` is set to `false`, then the `email` claim will be used
+  # to derive the Headscale username (as modified by the `strip_email_domain` entry).
+
+  use_username_claim: false
+
   # If `strip_email_domain` is set to `true`, the domain part of the username email address will be removed.
   # This will transform `first-name.last-name@example.com` to the user `first-name.last-name`
   # If `strip_email_domain` is set to `false` the domain part will NOT be removed resulting to the following
@@ -170,3 +180,48 @@ oidc:
 ```
 
 You can also use `allowed_domains` and `allowed_users` to restrict the users who can authenticate.
+
+## Authelia Example
+
+In order to integrate Headscale with your Authelia instance, you need to generate a client secret add your Headscale instance as a client.
+
+First, generate a client secret. If you are running Authelia inside docker, prepend `docker-compose exec <authelia_container_name>` before these commands:
+
+```shell
+authelia crypto hash generate pbkdf2 --variant sha512 --random --random.length 72
+```
+
+This will return two strings, a "Random Password" which you will fill into Headscale, and a "Digest" you will fill into Authelia.
+
+In your Authelia configuration, add Headscale under the client section:
+
+```yaml
+clients:
+  - id: headscale
+    description: Headscale
+    secret: "DIGEST_STRING_FROM_ABOVE"
+    public: false
+    authorization_policy: two_factor
+    redirect_uris:
+      - https://your.headscale.domain/oidc/callback
+    scopes:
+      - openid
+      - profile
+      - email
+      - groups
+```
+
+In your Headscale `config.yaml`, edit the config under `oidc`, filling in the `client_id` to match the `id` line in the Authelia config and filling in `client_secret` from the "Random Password" output.
+You may want to tune the `expiry`, `only_start_if_oidc_available`, and other entries. The following are only the required entries.
+
+```yaml
+oidc:
+  issuer: "https://your.authelia.domain"
+  client_id: "headscale"
+  client_secret: "RANDOM_PASSWORD_STRING_FROM_ABOVE"
+  scope: ["openid", "profile", "email", "groups"]
+  allowed_groups:
+    - authelia_groups_you_want_to_limit
+```
+
+In particular, you may want to set `use_username_claim: true` to use Authelia's `preferred_username` grant to set Headscale usernames.

hscontrol/oidc.go

@@ -242,7 +242,7 @@ func (h *Headscale) OIDCCallback(
 		return
 	}
 
-	userName, err := getUserName(writer, claims, h.cfg.OIDC.StripEmaildomain)
+	userName, err := getUserName(writer, claims, h.cfg.OIDC.UseUsernameClaim, h.cfg.OIDC.StripEmaildomain)
 	if err != nil {
 		return
 	}
@@ -259,7 +259,7 @@ func (h *Headscale) OIDCCallback(
 		return
 	}
 
-	content, err := renderOIDCCallbackTemplate(writer, claims)
+	content, err := renderOIDCCallbackTemplate(writer, userName)
 	if err != nil {
 		return
 	}
@@ -539,9 +539,14 @@ func (h *Headscale) validateNodeForOIDCCallback(
 			Str("expiresAt", fmt.Sprintf("%v", expiry)).
 			Msg("successfully refreshed node")
 
+		userName, err := getUserName(writer, claims, h.cfg.OIDC.UseUsernameClaim, h.cfg.OIDC.StripEmaildomain)
+		if err != nil {
+			userName = "unknown"
+		}
+
 		var content bytes.Buffer
 		if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{
-			User: claims.Email,
+			User: userName,
 			Verb: "Reauthenticated",
 		}); err != nil {
 			log.Error().
@@ -576,18 +581,30 @@ func (h *Headscale) validateNodeForOIDCCallback(
 func getUserName(
 	writer http.ResponseWriter,
 	claims *IDTokenClaims,
+	useUsernameClaim bool,
 	stripEmaildomain bool,
 ) (string, error) {
-	userName, err := util.NormalizeToFQDNRules(
-		claims.Email,
+	var claim string
+	if useUsernameClaim {
+		claim = claims.Username
+	} else {
+		claim = claims.Email
+	}
+	userName, err := NormalizeToFQDNRules(
+		claim,
 		stripEmaildomain,
 	)
 	if err != nil {
-		util.LogErr(err, "couldn't normalize email")
-
+		var friendlyErrMsg string
+		if useUsernameClaim {
+			friendlyErrMsg = "couldn't normalize username (preferred_username OIDC claim)"
+		} else {
+			friendlyErrMsg = "couldn't normalize username (email OIDC claim)"
+		}
+		log.Error().Err(err).Caller().Msgf(friendlyErrMsg)
 		writer.Header().Set("Content-Type", "text/plain; charset=utf-8")
 		writer.WriteHeader(http.StatusInternalServerError)
-		_, werr := writer.Write([]byte("couldn't normalize email"))
+		_, werr := writer.Write([]byte(friendlyErrMsg))
 		if werr != nil {
 			util.LogErr(err, "Failed to write response")
 		}
@@ -668,11 +685,11 @@ func (h *Headscale) registerNodeForOIDCCallback(
 
 func renderOIDCCallbackTemplate(
 	writer http.ResponseWriter,
-	claims *IDTokenClaims,
+	user string,
 ) (*bytes.Buffer, error) {
 	var content bytes.Buffer
 	if err := oidcCallbackTemplate.Execute(&content, oidcCallbackTemplateConfig{
-		User: claims.Email,
+		User: user,
 		Verb: "Authenticated",
 	}); err != nil {
 		log.Error().

hscontrol/types/config.go

@@ -103,6 +103,7 @@ type OIDCConfig struct {
 	AllowedUsers               []string
 	AllowedGroups              []string
 	StripEmaildomain           bool
+	UseUsernameClaim           bool
 	Expiry                     time.Duration
 	UseExpiryFromToken         bool
 }
@@ -183,6 +184,7 @@ func LoadConfig(path string, isFile bool) error {
 
 	viper.SetDefault("oidc.scope", []string{oidc.ScopeOpenID, "profile", "email"})
 	viper.SetDefault("oidc.strip_email_domain", true)
+	viper.SetDefault("oidc.use_username_claim", false)
 	viper.SetDefault("oidc.only_start_if_oidc_is_available", true)
 	viper.SetDefault("oidc.expiry", "180d")
 	viper.SetDefault("oidc.use_expiry_from_token", false)
@@ -631,6 +633,7 @@ func GetHeadscaleConfig() (*Config, error) {
 			AllowedDomains:   viper.GetStringSlice("oidc.allowed_domains"),
 			AllowedUsers:     viper.GetStringSlice("oidc.allowed_users"),
 			AllowedGroups:    viper.GetStringSlice("oidc.allowed_groups"),
+			UseUsernameClaim: viper.GetBool("oidc.use_username_claim"),
 			StripEmaildomain: viper.GetBool("oidc.strip_email_domain"),
 			Expiry: func() time.Duration {
 				// if set to 0, we assume no expiry