fix user group parsing for OAuth login (#317)

internal/app/auth/oauth_common.go

@@ -60,7 +60,8 @@ func getOauthFieldMapping(f config.OauthFields) config.OauthFields {
 			Phone:          "phone",
 			Department:     "department",
 		},
-		IsAdmin: "admin_flag",
+		IsAdmin:    "admin_flag",
+		UserGroups: "", // by default, do not use user groups
 	}
 	if f.UserIdentifier != "" {
 		defaultMap.UserIdentifier = f.UserIdentifier
@@ -83,6 +84,9 @@ func getOauthFieldMapping(f config.OauthFields) config.OauthFields {
 	if f.IsAdmin != "" {
 		defaultMap.IsAdmin = f.IsAdmin
 	}
+	if f.UserGroups != "" {
+		defaultMap.UserGroups = f.UserGroups
+	}
 
 	return defaultMap
 }

internal/app/auth/oauth_common_test.go

@@ -0,0 +1,57 @@
+package auth
+
+import (
+	"encoding/json"
+	"testing"
+
+	"github.com/h44z/wg-portal/internal/config"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func Test_parseOauthUserInfo(t *testing.T) {
+	userInfoStr := `
+{
+  "at_hash": "REDACTED",
+  "aud": "REDACTED",
+  "c_hash": "REDACTED",
+  "email": "test@mydomain.net",
+  "email_verified": true,
+  "exp": 1737404259,
+  "groups": [
+    "abuse@mydomain.net",
+    "postmaster@mydomain.net",
+    "wgportal-admins@mydomain.net"
+  ],
+  "iat": 1737317859,
+  "iss": "https://dex.mydomain.net",
+  "name": "Test User",
+  "nonce": "REDACTED",
+  "sub": "REDACTED"
+}
+`
+
+	userInfo := map[string]interface{}{}
+	err := json.Unmarshal([]byte(userInfoStr), &userInfo)
+	require.NoError(t, err)
+
+	fieldMapping := getOauthFieldMapping(config.OauthFields{
+		BaseFields: config.BaseFields{
+			UserIdentifier: "email",
+			Email:          "email",
+			Firstname:      "name",
+			Lastname:       "family_name",
+		},
+		UserGroups: "groups",
+	})
+	adminMapping := &config.OauthAdminMapping{
+		AdminGroupRegex: "^wgportal-admins@mydomain.net$",
+	}
+
+	info, err := parseOauthUserInfo(fieldMapping, adminMapping, userInfo)
+	assert.NoError(t, err)
+	assert.True(t, info.IsAdmin)
+	assert.Equal(t, info.Firstname, "Test User")
+	assert.Equal(t, info.Lastname, "")
+	assert.Equal(t, info.Email, "test@mydomain.net")
+}

internal/util.go

@@ -88,6 +88,17 @@ func MapDefaultStringSlice(m map[string]interface{}, key string, dflt []string)
 		return dflt
 	} else {
 		switch v := tmp.(type) {
+		case []any:
+			result := make([]string, 0, len(v))
+			for _, elem := range v {
+				switch vElem := elem.(type) {
+				case string:
+					result = append(result, vElem)
+				default:
+					result = append(result, fmt.Sprintf("%v", vElem))
+				}
+			}
+			return result
 		case []string:
 			return v
 		case string: