Merge branch 'main' into feat/api-key-ip-restriction

2026-01-09 21:34:28 +08:00
parent 90798f14b5 62dc0b953b
commit 6b97a8be28
70 changed files with 3765 additions and 660 deletions
--- a/backend/internal/handler/admin/account_handler.go
+++ b/backend/internal/handler/admin/account_handler.go
@@ -116,6 +116,7 @@ type BulkUpdateAccountsRequest struct {
 	Concurrency             *int           `json:"concurrency"`
 	Priority                *int           `json:"priority"`
 	Status                  string         `json:"status" binding:"omitempty,oneof=active inactive error"`
+	Schedulable             *bool          `json:"schedulable"`
 	GroupIDs                *[]int64       `json:"group_ids"`
 	Credentials             map[string]any `json:"credentials"`
 	Extra                   map[string]any `json:"extra"`
@@ -136,6 +137,11 @@ func (h *AccountHandler) List(c *gin.Context) {
 	accountType := c.Query("type")
 	status := c.Query("status")
 	search := c.Query("search")
+	// 标准化和验证 search 参数
+	search = strings.TrimSpace(search)
+	if len(search) > 100 {
+		search = search[:100]
+	}

 	accounts, total, err := h.adminService.ListAccounts(c.Request.Context(), page, pageSize, platform, accountType, status, search)
 	if err != nil {
@@ -655,6 +661,7 @@ func (h *AccountHandler) BulkUpdate(c *gin.Context) {
 		req.Concurrency != nil ||
 		req.Priority != nil ||
 		req.Status != "" ||
+		req.Schedulable != nil ||
 		req.GroupIDs != nil ||
 		len(req.Credentials) > 0 ||
 		len(req.Extra) > 0
@@ -671,6 +678,7 @@ func (h *AccountHandler) BulkUpdate(c *gin.Context) {
 		Concurrency:           req.Concurrency,
 		Priority:              req.Priority,
 		Status:                req.Status,
+		Schedulable:           req.Schedulable,
 		GroupIDs:              req.GroupIDs,
 		Credentials:           req.Credentials,
 		Extra:                 req.Extra,
--- a/backend/internal/handler/admin/group_handler.go
+++ b/backend/internal/handler/admin/group_handler.go
@@ -2,6 +2,7 @@ package admin

 import (
 	"strconv"
+	"strings"

 	"github.com/Wei-Shaw/sub2api/internal/handler/dto"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
@@ -67,6 +68,12 @@ func (h *GroupHandler) List(c *gin.Context) {
 	page, pageSize := response.ParsePagination(c)
 	platform := c.Query("platform")
 	status := c.Query("status")
+	search := c.Query("search")
+	// 标准化和验证 search 参数
+	search = strings.TrimSpace(search)
+	if len(search) > 100 {
+		search = search[:100]
+	}
 	isExclusiveStr := c.Query("is_exclusive")

 	var isExclusive *bool
@@ -75,7 +82,7 @@ func (h *GroupHandler) List(c *gin.Context) {
 		isExclusive = &val
 	}

-	groups, total, err := h.adminService.ListGroups(c.Request.Context(), page, pageSize, platform, status, isExclusive)
+	groups, total, err := h.adminService.ListGroups(c.Request.Context(), page, pageSize, platform, status, search, isExclusive)
 	if err != nil {
 		response.ErrorFrom(c, err)
 		return
--- a/backend/internal/handler/admin/proxy_handler.go
+++ b/backend/internal/handler/admin/proxy_handler.go
@@ -51,6 +51,11 @@ func (h *ProxyHandler) List(c *gin.Context) {
 	protocol := c.Query("protocol")
 	status := c.Query("status")
 	search := c.Query("search")
+	// 标准化和验证 search 参数
+	search = strings.TrimSpace(search)
+	if len(search) > 100 {
+		search = search[:100]
+	}

 	proxies, total, err := h.adminService.ListProxiesWithAccountCount(c.Request.Context(), page, pageSize, protocol, status, search)
 	if err != nil {
--- a/backend/internal/handler/admin/redeem_handler.go
+++ b/backend/internal/handler/admin/redeem_handler.go
@@ -5,6 +5,7 @@ import (
 	"encoding/csv"
 	"fmt"
 	"strconv"
+	"strings"

 	"github.com/Wei-Shaw/sub2api/internal/handler/dto"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
@@ -41,6 +42,11 @@ func (h *RedeemHandler) List(c *gin.Context) {
 	codeType := c.Query("type")
 	status := c.Query("status")
 	search := c.Query("search")
+	// 标准化和验证 search 参数
+	search = strings.TrimSpace(search)
+	if len(search) > 100 {
+		search = search[:100]
+	}

 	codes, total, err := h.adminService.ListRedeemCodes(c.Request.Context(), page, pageSize, codeType, status, search)
 	if err != nil {
--- a/backend/internal/handler/admin/setting_handler.go
+++ b/backend/internal/handler/admin/setting_handler.go
@@ -2,8 +2,10 @@ package admin

 import (
 	"log"
+	"strings"
 	"time"

+	"github.com/Wei-Shaw/sub2api/internal/config"
 	"github.com/Wei-Shaw/sub2api/internal/handler/dto"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
 	"github.com/Wei-Shaw/sub2api/internal/server/middleware"
@@ -38,33 +40,37 @@ func (h *SettingHandler) GetSettings(c *gin.Context) {
 	}

 	response.Success(c, dto.SystemSettings{
-		RegistrationEnabled:          settings.RegistrationEnabled,
-		EmailVerifyEnabled:           settings.EmailVerifyEnabled,
-		SMTPHost:                     settings.SMTPHost,
-		SMTPPort:                     settings.SMTPPort,
-		SMTPUsername:                 settings.SMTPUsername,
-		SMTPPasswordConfigured:       settings.SMTPPasswordConfigured,
-		SMTPFrom:                     settings.SMTPFrom,
-		SMTPFromName:                 settings.SMTPFromName,
-		SMTPUseTLS:                   settings.SMTPUseTLS,
-		TurnstileEnabled:             settings.TurnstileEnabled,
-		TurnstileSiteKey:             settings.TurnstileSiteKey,
-		TurnstileSecretKeyConfigured: settings.TurnstileSecretKeyConfigured,
-		SiteName:                     settings.SiteName,
-		SiteLogo:                     settings.SiteLogo,
-		SiteSubtitle:                 settings.SiteSubtitle,
-		APIBaseURL:                   settings.APIBaseURL,
-		ContactInfo:                  settings.ContactInfo,
-		DocURL:                       settings.DocURL,
-		DefaultConcurrency:           settings.DefaultConcurrency,
-		DefaultBalance:               settings.DefaultBalance,
-		EnableModelFallback:          settings.EnableModelFallback,
-		FallbackModelAnthropic:       settings.FallbackModelAnthropic,
-		FallbackModelOpenAI:          settings.FallbackModelOpenAI,
-		FallbackModelGemini:          settings.FallbackModelGemini,
-		FallbackModelAntigravity:     settings.FallbackModelAntigravity,
-		EnableIdentityPatch:          settings.EnableIdentityPatch,
-		IdentityPatchPrompt:          settings.IdentityPatchPrompt,
+		RegistrationEnabled:                  settings.RegistrationEnabled,
+		EmailVerifyEnabled:                   settings.EmailVerifyEnabled,
+		SMTPHost:                             settings.SMTPHost,
+		SMTPPort:                             settings.SMTPPort,
+		SMTPUsername:                         settings.SMTPUsername,
+		SMTPPasswordConfigured:               settings.SMTPPasswordConfigured,
+		SMTPFrom:                             settings.SMTPFrom,
+		SMTPFromName:                         settings.SMTPFromName,
+		SMTPUseTLS:                           settings.SMTPUseTLS,
+		TurnstileEnabled:                     settings.TurnstileEnabled,
+		TurnstileSiteKey:                     settings.TurnstileSiteKey,
+		TurnstileSecretKeyConfigured:         settings.TurnstileSecretKeyConfigured,
+		LinuxDoConnectEnabled:                settings.LinuxDoConnectEnabled,
+		LinuxDoConnectClientID:               settings.LinuxDoConnectClientID,
+		LinuxDoConnectClientSecretConfigured: settings.LinuxDoConnectClientSecretConfigured,
+		LinuxDoConnectRedirectURL:            settings.LinuxDoConnectRedirectURL,
+		SiteName:                             settings.SiteName,
+		SiteLogo:                             settings.SiteLogo,
+		SiteSubtitle:                         settings.SiteSubtitle,
+		APIBaseURL:                           settings.APIBaseURL,
+		ContactInfo:                          settings.ContactInfo,
+		DocURL:                               settings.DocURL,
+		DefaultConcurrency:                   settings.DefaultConcurrency,
+		DefaultBalance:                       settings.DefaultBalance,
+		EnableModelFallback:                  settings.EnableModelFallback,
+		FallbackModelAnthropic:               settings.FallbackModelAnthropic,
+		FallbackModelOpenAI:                  settings.FallbackModelOpenAI,
+		FallbackModelGemini:                  settings.FallbackModelGemini,
+		FallbackModelAntigravity:             settings.FallbackModelAntigravity,
+		EnableIdentityPatch:                  settings.EnableIdentityPatch,
+		IdentityPatchPrompt:                  settings.IdentityPatchPrompt,
 	})
 }

@@ -88,6 +94,12 @@ type UpdateSettingsRequest struct {
 	TurnstileSiteKey   string `json:"turnstile_site_key"`
 	TurnstileSecretKey string `json:"turnstile_secret_key"`

+	// LinuxDo Connect OAuth 登录（终端用户 SSO）
+	LinuxDoConnectEnabled      bool   `json:"linuxdo_connect_enabled"`
+	LinuxDoConnectClientID     string `json:"linuxdo_connect_client_id"`
+	LinuxDoConnectClientSecret string `json:"linuxdo_connect_client_secret"`
+	LinuxDoConnectRedirectURL  string `json:"linuxdo_connect_redirect_url"`
+
 	// OEM设置
 	SiteName     string `json:"site_name"`
 	SiteLogo     string `json:"site_logo"`
@@ -165,34 +177,67 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		}
 	}

+	// LinuxDo Connect 参数验证
+	if req.LinuxDoConnectEnabled {
+		req.LinuxDoConnectClientID = strings.TrimSpace(req.LinuxDoConnectClientID)
+		req.LinuxDoConnectClientSecret = strings.TrimSpace(req.LinuxDoConnectClientSecret)
+		req.LinuxDoConnectRedirectURL = strings.TrimSpace(req.LinuxDoConnectRedirectURL)
+
+		if req.LinuxDoConnectClientID == "" {
+			response.BadRequest(c, "LinuxDo Client ID is required when enabled")
+			return
+		}
+		if req.LinuxDoConnectRedirectURL == "" {
+			response.BadRequest(c, "LinuxDo Redirect URL is required when enabled")
+			return
+		}
+		if err := config.ValidateAbsoluteHTTPURL(req.LinuxDoConnectRedirectURL); err != nil {
+			response.BadRequest(c, "LinuxDo Redirect URL must be an absolute http(s) URL")
+			return
+		}
+
+		// 如果未提供 client_secret，则保留现有值（如有）。
+		if req.LinuxDoConnectClientSecret == "" {
+			if previousSettings.LinuxDoConnectClientSecret == "" {
+				response.BadRequest(c, "LinuxDo Client Secret is required when enabled")
+				return
+			}
+			req.LinuxDoConnectClientSecret = previousSettings.LinuxDoConnectClientSecret
+		}
+	}
+
 	settings := &service.SystemSettings{
-		RegistrationEnabled:      req.RegistrationEnabled,
-		EmailVerifyEnabled:       req.EmailVerifyEnabled,
-		SMTPHost:                 req.SMTPHost,
-		SMTPPort:                 req.SMTPPort,
-		SMTPUsername:             req.SMTPUsername,
-		SMTPPassword:             req.SMTPPassword,
-		SMTPFrom:                 req.SMTPFrom,
-		SMTPFromName:             req.SMTPFromName,
-		SMTPUseTLS:               req.SMTPUseTLS,
-		TurnstileEnabled:         req.TurnstileEnabled,
-		TurnstileSiteKey:         req.TurnstileSiteKey,
-		TurnstileSecretKey:       req.TurnstileSecretKey,
-		SiteName:                 req.SiteName,
-		SiteLogo:                 req.SiteLogo,
-		SiteSubtitle:             req.SiteSubtitle,
-		APIBaseURL:               req.APIBaseURL,
-		ContactInfo:              req.ContactInfo,
-		DocURL:                   req.DocURL,
-		DefaultConcurrency:       req.DefaultConcurrency,
-		DefaultBalance:           req.DefaultBalance,
-		EnableModelFallback:      req.EnableModelFallback,
-		FallbackModelAnthropic:   req.FallbackModelAnthropic,
-		FallbackModelOpenAI:      req.FallbackModelOpenAI,
-		FallbackModelGemini:      req.FallbackModelGemini,
-		FallbackModelAntigravity: req.FallbackModelAntigravity,
-		EnableIdentityPatch:      req.EnableIdentityPatch,
-		IdentityPatchPrompt:      req.IdentityPatchPrompt,
+		RegistrationEnabled:        req.RegistrationEnabled,
+		EmailVerifyEnabled:         req.EmailVerifyEnabled,
+		SMTPHost:                   req.SMTPHost,
+		SMTPPort:                   req.SMTPPort,
+		SMTPUsername:               req.SMTPUsername,
+		SMTPPassword:               req.SMTPPassword,
+		SMTPFrom:                   req.SMTPFrom,
+		SMTPFromName:               req.SMTPFromName,
+		SMTPUseTLS:                 req.SMTPUseTLS,
+		TurnstileEnabled:           req.TurnstileEnabled,
+		TurnstileSiteKey:           req.TurnstileSiteKey,
+		TurnstileSecretKey:         req.TurnstileSecretKey,
+		LinuxDoConnectEnabled:      req.LinuxDoConnectEnabled,
+		LinuxDoConnectClientID:     req.LinuxDoConnectClientID,
+		LinuxDoConnectClientSecret: req.LinuxDoConnectClientSecret,
+		LinuxDoConnectRedirectURL:  req.LinuxDoConnectRedirectURL,
+		SiteName:                   req.SiteName,
+		SiteLogo:                   req.SiteLogo,
+		SiteSubtitle:               req.SiteSubtitle,
+		APIBaseURL:                 req.APIBaseURL,
+		ContactInfo:                req.ContactInfo,
+		DocURL:                     req.DocURL,
+		DefaultConcurrency:         req.DefaultConcurrency,
+		DefaultBalance:             req.DefaultBalance,
+		EnableModelFallback:        req.EnableModelFallback,
+		FallbackModelAnthropic:     req.FallbackModelAnthropic,
+		FallbackModelOpenAI:        req.FallbackModelOpenAI,
+		FallbackModelGemini:        req.FallbackModelGemini,
+		FallbackModelAntigravity:   req.FallbackModelAntigravity,
+		EnableIdentityPatch:        req.EnableIdentityPatch,
+		IdentityPatchPrompt:        req.IdentityPatchPrompt,
 	}

 	if err := h.settingService.UpdateSettings(c.Request.Context(), settings); err != nil {
@@ -210,33 +255,37 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 	}

 	response.Success(c, dto.SystemSettings{
-		RegistrationEnabled:          updatedSettings.RegistrationEnabled,
-		EmailVerifyEnabled:           updatedSettings.EmailVerifyEnabled,
-		SMTPHost:                     updatedSettings.SMTPHost,
-		SMTPPort:                     updatedSettings.SMTPPort,
-		SMTPUsername:                 updatedSettings.SMTPUsername,
-		SMTPPasswordConfigured:       updatedSettings.SMTPPasswordConfigured,
-		SMTPFrom:                     updatedSettings.SMTPFrom,
-		SMTPFromName:                 updatedSettings.SMTPFromName,
-		SMTPUseTLS:                   updatedSettings.SMTPUseTLS,
-		TurnstileEnabled:             updatedSettings.TurnstileEnabled,
-		TurnstileSiteKey:             updatedSettings.TurnstileSiteKey,
-		TurnstileSecretKeyConfigured: updatedSettings.TurnstileSecretKeyConfigured,
-		SiteName:                     updatedSettings.SiteName,
-		SiteLogo:                     updatedSettings.SiteLogo,
-		SiteSubtitle:                 updatedSettings.SiteSubtitle,
-		APIBaseURL:                   updatedSettings.APIBaseURL,
-		ContactInfo:                  updatedSettings.ContactInfo,
-		DocURL:                       updatedSettings.DocURL,
-		DefaultConcurrency:           updatedSettings.DefaultConcurrency,
-		DefaultBalance:               updatedSettings.DefaultBalance,
-		EnableModelFallback:          updatedSettings.EnableModelFallback,
-		FallbackModelAnthropic:       updatedSettings.FallbackModelAnthropic,
-		FallbackModelOpenAI:          updatedSettings.FallbackModelOpenAI,
-		FallbackModelGemini:          updatedSettings.FallbackModelGemini,
-		FallbackModelAntigravity:     updatedSettings.FallbackModelAntigravity,
-		EnableIdentityPatch:          updatedSettings.EnableIdentityPatch,
-		IdentityPatchPrompt:          updatedSettings.IdentityPatchPrompt,
+		RegistrationEnabled:                  updatedSettings.RegistrationEnabled,
+		EmailVerifyEnabled:                   updatedSettings.EmailVerifyEnabled,
+		SMTPHost:                             updatedSettings.SMTPHost,
+		SMTPPort:                             updatedSettings.SMTPPort,
+		SMTPUsername:                         updatedSettings.SMTPUsername,
+		SMTPPasswordConfigured:               updatedSettings.SMTPPasswordConfigured,
+		SMTPFrom:                             updatedSettings.SMTPFrom,
+		SMTPFromName:                         updatedSettings.SMTPFromName,
+		SMTPUseTLS:                           updatedSettings.SMTPUseTLS,
+		TurnstileEnabled:                     updatedSettings.TurnstileEnabled,
+		TurnstileSiteKey:                     updatedSettings.TurnstileSiteKey,
+		TurnstileSecretKeyConfigured:         updatedSettings.TurnstileSecretKeyConfigured,
+		LinuxDoConnectEnabled:                updatedSettings.LinuxDoConnectEnabled,
+		LinuxDoConnectClientID:               updatedSettings.LinuxDoConnectClientID,
+		LinuxDoConnectClientSecretConfigured: updatedSettings.LinuxDoConnectClientSecretConfigured,
+		LinuxDoConnectRedirectURL:            updatedSettings.LinuxDoConnectRedirectURL,
+		SiteName:                             updatedSettings.SiteName,
+		SiteLogo:                             updatedSettings.SiteLogo,
+		SiteSubtitle:                         updatedSettings.SiteSubtitle,
+		APIBaseURL:                           updatedSettings.APIBaseURL,
+		ContactInfo:                          updatedSettings.ContactInfo,
+		DocURL:                               updatedSettings.DocURL,
+		DefaultConcurrency:                   updatedSettings.DefaultConcurrency,
+		DefaultBalance:                       updatedSettings.DefaultBalance,
+		EnableModelFallback:                  updatedSettings.EnableModelFallback,
+		FallbackModelAnthropic:               updatedSettings.FallbackModelAnthropic,
+		FallbackModelOpenAI:                  updatedSettings.FallbackModelOpenAI,
+		FallbackModelGemini:                  updatedSettings.FallbackModelGemini,
+		FallbackModelAntigravity:             updatedSettings.FallbackModelAntigravity,
+		EnableIdentityPatch:                  updatedSettings.EnableIdentityPatch,
+		IdentityPatchPrompt:                  updatedSettings.IdentityPatchPrompt,
 	})
 }

@@ -298,6 +347,18 @@ func diffSettings(before *service.SystemSettings, after *service.SystemSettings,
 	if req.TurnstileSecretKey != "" {
 		changed = append(changed, "turnstile_secret_key")
 	}
+	if before.LinuxDoConnectEnabled != after.LinuxDoConnectEnabled {
+		changed = append(changed, "linuxdo_connect_enabled")
+	}
+	if before.LinuxDoConnectClientID != after.LinuxDoConnectClientID {
+		changed = append(changed, "linuxdo_connect_client_id")
+	}
+	if req.LinuxDoConnectClientSecret != "" {
+		changed = append(changed, "linuxdo_connect_client_secret")
+	}
+	if before.LinuxDoConnectRedirectURL != after.LinuxDoConnectRedirectURL {
+		changed = append(changed, "linuxdo_connect_redirect_url")
+	}
 	if before.SiteName != after.SiteName {
 		changed = append(changed, "site_name")
 	}
@@ -337,6 +398,12 @@ func diffSettings(before *service.SystemSettings, after *service.SystemSettings,
 	if before.FallbackModelAntigravity != after.FallbackModelAntigravity {
 		changed = append(changed, "fallback_model_antigravity")
 	}
+	if before.EnableIdentityPatch != after.EnableIdentityPatch {
+		changed = append(changed, "enable_identity_patch")
+	}
+	if before.IdentityPatchPrompt != after.IdentityPatchPrompt {
+		changed = append(changed, "identity_patch_prompt")
+	}
 	return changed
 }

--- a/backend/internal/handler/admin/user_handler.go
+++ b/backend/internal/handler/admin/user_handler.go
@@ -2,6 +2,7 @@ package admin

 import (
 	"strconv"
+	"strings"

 	"github.com/Wei-Shaw/sub2api/internal/handler/dto"
 	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
@@ -63,10 +64,17 @@ type UpdateBalanceRequest struct {
 func (h *UserHandler) List(c *gin.Context) {
 	page, pageSize := response.ParsePagination(c)

+	search := c.Query("search")
+	// 标准化和验证 search 参数
+	search = strings.TrimSpace(search)
+	if len(search) > 100 {
+		search = search[:100]
+	}
+
 	filters := service.UserListFilters{
 		Status:     c.Query("status"),
 		Role:       c.Query("role"),
-		Search:     c.Query("search"),
+		Search:     search,
 		Attributes: parseAttributeFilters(c),
 	}

--- a/backend/internal/handler/auth_handler.go
+++ b/backend/internal/handler/auth_handler.go
@@ -15,14 +15,16 @@ type AuthHandler struct {
 	cfg         *config.Config
 	authService *service.AuthService
 	userService *service.UserService
+	settingSvc  *service.SettingService
 }

 // NewAuthHandler creates a new AuthHandler
-func NewAuthHandler(cfg *config.Config, authService *service.AuthService, userService *service.UserService) *AuthHandler {
+func NewAuthHandler(cfg *config.Config, authService *service.AuthService, userService *service.UserService, settingService *service.SettingService) *AuthHandler {
 	return &AuthHandler{
 		cfg:         cfg,
 		authService: authService,
 		userService: userService,
+		settingSvc:  settingService,
 	}
 }

--- a/backend/internal/handler/auth_linuxdo_oauth.go
+++ b/backend/internal/handler/auth_linuxdo_oauth.go
@@ -0,0 +1,679 @@
+package handler
+
+import (
+	"context"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"strconv"
+	"strings"
+	"time"
+	"unicode/utf8"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/oauth"
+	"github.com/Wei-Shaw/sub2api/internal/pkg/response"
+	"github.com/Wei-Shaw/sub2api/internal/service"
+
+	"github.com/gin-gonic/gin"
+	"github.com/imroc/req/v3"
+	"github.com/tidwall/gjson"
+)
+
+const (
+	linuxDoOAuthCookiePath        = "/api/v1/auth/oauth/linuxdo"
+	linuxDoOAuthStateCookieName   = "linuxdo_oauth_state"
+	linuxDoOAuthVerifierCookie    = "linuxdo_oauth_verifier"
+	linuxDoOAuthRedirectCookie    = "linuxdo_oauth_redirect"
+	linuxDoOAuthCookieMaxAgeSec   = 10 * 60 // 10 minutes
+	linuxDoOAuthDefaultRedirectTo = "/dashboard"
+	linuxDoOAuthDefaultFrontendCB = "/auth/linuxdo/callback"
+
+	linuxDoOAuthMaxRedirectLen      = 2048
+	linuxDoOAuthMaxFragmentValueLen = 512
+	linuxDoOAuthMaxSubjectLen       = 64 - len("linuxdo-")
+)
+
+type linuxDoTokenResponse struct {
+	AccessToken  string `json:"access_token"`
+	TokenType    string `json:"token_type"`
+	ExpiresIn    int64  `json:"expires_in"`
+	RefreshToken string `json:"refresh_token,omitempty"`
+	Scope        string `json:"scope,omitempty"`
+}
+
+type linuxDoTokenExchangeError struct {
+	StatusCode          int
+	ProviderError       string
+	ProviderDescription string
+	Body                string
+}
+
+func (e *linuxDoTokenExchangeError) Error() string {
+	if e == nil {
+		return ""
+	}
+	parts := []string{fmt.Sprintf("token exchange status=%d", e.StatusCode)}
+	if strings.TrimSpace(e.ProviderError) != "" {
+		parts = append(parts, "error="+strings.TrimSpace(e.ProviderError))
+	}
+	if strings.TrimSpace(e.ProviderDescription) != "" {
+		parts = append(parts, "error_description="+strings.TrimSpace(e.ProviderDescription))
+	}
+	return strings.Join(parts, " ")
+}
+
+// LinuxDoOAuthStart 启动 LinuxDo Connect OAuth 登录流程。
+// GET /api/v1/auth/oauth/linuxdo/start?redirect=/dashboard
+func (h *AuthHandler) LinuxDoOAuthStart(c *gin.Context) {
+	cfg, err := h.getLinuxDoOAuthConfig(c.Request.Context())
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	state, err := oauth.GenerateState()
+	if err != nil {
+		response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_STATE_GEN_FAILED", "failed to generate oauth state").WithCause(err))
+		return
+	}
+
+	redirectTo := sanitizeFrontendRedirectPath(c.Query("redirect"))
+	if redirectTo == "" {
+		redirectTo = linuxDoOAuthDefaultRedirectTo
+	}
+
+	secureCookie := isRequestHTTPS(c)
+	setCookie(c, linuxDoOAuthStateCookieName, encodeCookieValue(state), linuxDoOAuthCookieMaxAgeSec, secureCookie)
+	setCookie(c, linuxDoOAuthRedirectCookie, encodeCookieValue(redirectTo), linuxDoOAuthCookieMaxAgeSec, secureCookie)
+
+	codeChallenge := ""
+	if cfg.UsePKCE {
+		verifier, err := oauth.GenerateCodeVerifier()
+		if err != nil {
+			response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_PKCE_GEN_FAILED", "failed to generate pkce verifier").WithCause(err))
+			return
+		}
+		codeChallenge = oauth.GenerateCodeChallenge(verifier)
+		setCookie(c, linuxDoOAuthVerifierCookie, encodeCookieValue(verifier), linuxDoOAuthCookieMaxAgeSec, secureCookie)
+	}
+
+	redirectURI := strings.TrimSpace(cfg.RedirectURL)
+	if redirectURI == "" {
+		response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_CONFIG_INVALID", "oauth redirect url not configured"))
+		return
+	}
+
+	authURL, err := buildLinuxDoAuthorizeURL(cfg, state, codeChallenge, redirectURI)
+	if err != nil {
+		response.ErrorFrom(c, infraerrors.InternalServer("OAUTH_BUILD_URL_FAILED", "failed to build oauth authorization url").WithCause(err))
+		return
+	}
+
+	c.Redirect(http.StatusFound, authURL)
+}
+
+// LinuxDoOAuthCallback 处理 OAuth 回调：创建/登录用户，然后重定向到前端。
+// GET /api/v1/auth/oauth/linuxdo/callback?code=...&state=...
+func (h *AuthHandler) LinuxDoOAuthCallback(c *gin.Context) {
+	cfg, cfgErr := h.getLinuxDoOAuthConfig(c.Request.Context())
+	if cfgErr != nil {
+		response.ErrorFrom(c, cfgErr)
+		return
+	}
+
+	frontendCallback := strings.TrimSpace(cfg.FrontendRedirectURL)
+	if frontendCallback == "" {
+		frontendCallback = linuxDoOAuthDefaultFrontendCB
+	}
+
+	if providerErr := strings.TrimSpace(c.Query("error")); providerErr != "" {
+		redirectOAuthError(c, frontendCallback, "provider_error", providerErr, c.Query("error_description"))
+		return
+	}
+
+	code := strings.TrimSpace(c.Query("code"))
+	state := strings.TrimSpace(c.Query("state"))
+	if code == "" || state == "" {
+		redirectOAuthError(c, frontendCallback, "missing_params", "missing code/state", "")
+		return
+	}
+
+	secureCookie := isRequestHTTPS(c)
+	defer func() {
+		clearCookie(c, linuxDoOAuthStateCookieName, secureCookie)
+		clearCookie(c, linuxDoOAuthVerifierCookie, secureCookie)
+		clearCookie(c, linuxDoOAuthRedirectCookie, secureCookie)
+	}()
+
+	expectedState, err := readCookieDecoded(c, linuxDoOAuthStateCookieName)
+	if err != nil || expectedState == "" || state != expectedState {
+		redirectOAuthError(c, frontendCallback, "invalid_state", "invalid oauth state", "")
+		return
+	}
+
+	redirectTo, _ := readCookieDecoded(c, linuxDoOAuthRedirectCookie)
+	redirectTo = sanitizeFrontendRedirectPath(redirectTo)
+	if redirectTo == "" {
+		redirectTo = linuxDoOAuthDefaultRedirectTo
+	}
+
+	codeVerifier := ""
+	if cfg.UsePKCE {
+		codeVerifier, _ = readCookieDecoded(c, linuxDoOAuthVerifierCookie)
+		if codeVerifier == "" {
+			redirectOAuthError(c, frontendCallback, "missing_verifier", "missing pkce verifier", "")
+			return
+		}
+	}
+
+	redirectURI := strings.TrimSpace(cfg.RedirectURL)
+	if redirectURI == "" {
+		redirectOAuthError(c, frontendCallback, "config_error", "oauth redirect url not configured", "")
+		return
+	}
+
+	tokenResp, err := linuxDoExchangeCode(c.Request.Context(), cfg, code, redirectURI, codeVerifier)
+	if err != nil {
+		description := ""
+		var exchangeErr *linuxDoTokenExchangeError
+		if errors.As(err, &exchangeErr) && exchangeErr != nil {
+			log.Printf(
+				"[LinuxDo OAuth] token exchange failed: status=%d provider_error=%q provider_description=%q body=%s",
+				exchangeErr.StatusCode,
+				exchangeErr.ProviderError,
+				exchangeErr.ProviderDescription,
+				truncateLogValue(exchangeErr.Body, 2048),
+			)
+			description = exchangeErr.Error()
+		} else {
+			log.Printf("[LinuxDo OAuth] token exchange failed: %v", err)
+			description = err.Error()
+		}
+		redirectOAuthError(c, frontendCallback, "token_exchange_failed", "failed to exchange oauth code", singleLine(description))
+		return
+	}
+
+	email, username, subject, err := linuxDoFetchUserInfo(c.Request.Context(), cfg, tokenResp)
+	if err != nil {
+		log.Printf("[LinuxDo OAuth] userinfo fetch failed: %v", err)
+		redirectOAuthError(c, frontendCallback, "userinfo_failed", "failed to fetch user info", "")
+		return
+	}
+
+	// 安全考虑：不要把第三方返回的 email 直接映射到本地账号（可能与本地邮箱用户冲突导致账号被接管）。
+	// 统一使用基于 subject 的稳定合成邮箱来做账号绑定。
+	if subject != "" {
+		email = linuxDoSyntheticEmail(subject)
+	}
+
+	jwtToken, _, err := h.authService.LoginOrRegisterOAuth(c.Request.Context(), email, username)
+	if err != nil {
+		// 避免把内部细节泄露给客户端；给前端保留结构化原因与提示信息即可。
+		redirectOAuthError(c, frontendCallback, "login_failed", infraerrors.Reason(err), infraerrors.Message(err))
+		return
+	}
+
+	fragment := url.Values{}
+	fragment.Set("access_token", jwtToken)
+	fragment.Set("token_type", "Bearer")
+	fragment.Set("redirect", redirectTo)
+	redirectWithFragment(c, frontendCallback, fragment)
+}
+
+func (h *AuthHandler) getLinuxDoOAuthConfig(ctx context.Context) (config.LinuxDoConnectConfig, error) {
+	if h != nil && h.settingSvc != nil {
+		return h.settingSvc.GetLinuxDoConnectOAuthConfig(ctx)
+	}
+	if h == nil || h.cfg == nil {
+		return config.LinuxDoConnectConfig{}, infraerrors.ServiceUnavailable("CONFIG_NOT_READY", "config not loaded")
+	}
+	if !h.cfg.LinuxDo.Enabled {
+		return config.LinuxDoConnectConfig{}, infraerrors.NotFound("OAUTH_DISABLED", "oauth login is disabled")
+	}
+	return h.cfg.LinuxDo, nil
+}
+
+func linuxDoExchangeCode(
+	ctx context.Context,
+	cfg config.LinuxDoConnectConfig,
+	code string,
+	redirectURI string,
+	codeVerifier string,
+) (*linuxDoTokenResponse, error) {
+	client := req.C().SetTimeout(30 * time.Second)
+
+	form := url.Values{}
+	form.Set("grant_type", "authorization_code")
+	form.Set("client_id", cfg.ClientID)
+	form.Set("code", code)
+	form.Set("redirect_uri", redirectURI)
+	if cfg.UsePKCE {
+		form.Set("code_verifier", codeVerifier)
+	}
+
+	r := client.R().
+		SetContext(ctx).
+		SetHeader("Accept", "application/json")
+
+	switch strings.ToLower(strings.TrimSpace(cfg.TokenAuthMethod)) {
+	case "", "client_secret_post":
+		form.Set("client_secret", cfg.ClientSecret)
+	case "client_secret_basic":
+		r.SetBasicAuth(cfg.ClientID, cfg.ClientSecret)
+	case "none":
+	default:
+		return nil, fmt.Errorf("unsupported token_auth_method: %s", cfg.TokenAuthMethod)
+	}
+
+	resp, err := r.SetFormDataFromValues(form).Post(cfg.TokenURL)
+	if err != nil {
+		return nil, fmt.Errorf("request token: %w", err)
+	}
+	body := strings.TrimSpace(resp.String())
+	if !resp.IsSuccessState() {
+		providerErr, providerDesc := parseOAuthProviderError(body)
+		return nil, &linuxDoTokenExchangeError{
+			StatusCode:          resp.StatusCode,
+			ProviderError:       providerErr,
+			ProviderDescription: providerDesc,
+			Body:                body,
+		}
+	}
+
+	tokenResp, ok := parseLinuxDoTokenResponse(body)
+	if !ok || strings.TrimSpace(tokenResp.AccessToken) == "" {
+		return nil, &linuxDoTokenExchangeError{
+			StatusCode: resp.StatusCode,
+			Body:       body,
+		}
+	}
+	if strings.TrimSpace(tokenResp.TokenType) == "" {
+		tokenResp.TokenType = "Bearer"
+	}
+	return tokenResp, nil
+}
+
+func linuxDoFetchUserInfo(
+	ctx context.Context,
+	cfg config.LinuxDoConnectConfig,
+	token *linuxDoTokenResponse,
+) (email string, username string, subject string, err error) {
+	client := req.C().SetTimeout(30 * time.Second)
+	authorization, err := buildBearerAuthorization(token.TokenType, token.AccessToken)
+	if err != nil {
+		return "", "", "", fmt.Errorf("invalid token for userinfo request: %w", err)
+	}
+
+	resp, err := client.R().
+		SetContext(ctx).
+		SetHeader("Accept", "application/json").
+		SetHeader("Authorization", authorization).
+		Get(cfg.UserInfoURL)
+	if err != nil {
+		return "", "", "", fmt.Errorf("request userinfo: %w", err)
+	}
+	if !resp.IsSuccessState() {
+		return "", "", "", fmt.Errorf("userinfo status=%d", resp.StatusCode)
+	}
+
+	return linuxDoParseUserInfo(resp.String(), cfg)
+}
+
+func linuxDoParseUserInfo(body string, cfg config.LinuxDoConnectConfig) (email string, username string, subject string, err error) {
+	email = firstNonEmpty(
+		getGJSON(body, cfg.UserInfoEmailPath),
+		getGJSON(body, "email"),
+		getGJSON(body, "user.email"),
+		getGJSON(body, "data.email"),
+		getGJSON(body, "attributes.email"),
+	)
+	username = firstNonEmpty(
+		getGJSON(body, cfg.UserInfoUsernamePath),
+		getGJSON(body, "username"),
+		getGJSON(body, "preferred_username"),
+		getGJSON(body, "name"),
+		getGJSON(body, "user.username"),
+		getGJSON(body, "user.name"),
+	)
+	subject = firstNonEmpty(
+		getGJSON(body, cfg.UserInfoIDPath),
+		getGJSON(body, "sub"),
+		getGJSON(body, "id"),
+		getGJSON(body, "user_id"),
+		getGJSON(body, "uid"),
+		getGJSON(body, "user.id"),
+	)
+
+	subject = strings.TrimSpace(subject)
+	if subject == "" {
+		return "", "", "", errors.New("userinfo missing id field")
+	}
+	if !isSafeLinuxDoSubject(subject) {
+		return "", "", "", errors.New("userinfo returned invalid id field")
+	}
+
+	email = strings.TrimSpace(email)
+	if email == "" {
+		// LinuxDo Connect 的 userinfo 可能不提供 email。为兼容现有用户模型（email 必填且唯一），使用稳定的合成邮箱。
+		email = linuxDoSyntheticEmail(subject)
+	}
+
+	username = strings.TrimSpace(username)
+	if username == "" {
+		username = "linuxdo_" + subject
+	}
+
+	return email, username, subject, nil
+}
+
+func buildLinuxDoAuthorizeURL(cfg config.LinuxDoConnectConfig, state string, codeChallenge string, redirectURI string) (string, error) {
+	u, err := url.Parse(cfg.AuthorizeURL)
+	if err != nil {
+		return "", fmt.Errorf("parse authorize_url: %w", err)
+	}
+
+	q := u.Query()
+	q.Set("response_type", "code")
+	q.Set("client_id", cfg.ClientID)
+	q.Set("redirect_uri", redirectURI)
+	if strings.TrimSpace(cfg.Scopes) != "" {
+		q.Set("scope", cfg.Scopes)
+	}
+	q.Set("state", state)
+	if cfg.UsePKCE {
+		q.Set("code_challenge", codeChallenge)
+		q.Set("code_challenge_method", "S256")
+	}
+
+	u.RawQuery = q.Encode()
+	return u.String(), nil
+}
+
+func redirectOAuthError(c *gin.Context, frontendCallback string, code string, message string, description string) {
+	fragment := url.Values{}
+	fragment.Set("error", truncateFragmentValue(code))
+	if strings.TrimSpace(message) != "" {
+		fragment.Set("error_message", truncateFragmentValue(message))
+	}
+	if strings.TrimSpace(description) != "" {
+		fragment.Set("error_description", truncateFragmentValue(description))
+	}
+	redirectWithFragment(c, frontendCallback, fragment)
+}
+
+func redirectWithFragment(c *gin.Context, frontendCallback string, fragment url.Values) {
+	u, err := url.Parse(frontendCallback)
+	if err != nil {
+		// 兜底：尽力跳转到默认页面，避免卡死在回调页。
+		c.Redirect(http.StatusFound, linuxDoOAuthDefaultRedirectTo)
+		return
+	}
+	if u.Scheme != "" && !strings.EqualFold(u.Scheme, "http") && !strings.EqualFold(u.Scheme, "https") {
+		c.Redirect(http.StatusFound, linuxDoOAuthDefaultRedirectTo)
+		return
+	}
+	u.Fragment = fragment.Encode()
+	c.Header("Cache-Control", "no-store")
+	c.Header("Pragma", "no-cache")
+	c.Redirect(http.StatusFound, u.String())
+}
+
+func firstNonEmpty(values ...string) string {
+	for _, v := range values {
+		v = strings.TrimSpace(v)
+		if v != "" {
+			return v
+		}
+	}
+	return ""
+}
+
+func parseOAuthProviderError(body string) (providerErr string, providerDesc string) {
+	body = strings.TrimSpace(body)
+	if body == "" {
+		return "", ""
+	}
+
+	providerErr = firstNonEmpty(
+		getGJSON(body, "error"),
+		getGJSON(body, "code"),
+		getGJSON(body, "error.code"),
+	)
+	providerDesc = firstNonEmpty(
+		getGJSON(body, "error_description"),
+		getGJSON(body, "error.message"),
+		getGJSON(body, "message"),
+		getGJSON(body, "detail"),
+	)
+
+	if providerErr != "" || providerDesc != "" {
+		return providerErr, providerDesc
+	}
+
+	values, err := url.ParseQuery(body)
+	if err != nil {
+		return "", ""
+	}
+	providerErr = firstNonEmpty(values.Get("error"), values.Get("code"))
+	providerDesc = firstNonEmpty(values.Get("error_description"), values.Get("error_message"), values.Get("message"))
+	return providerErr, providerDesc
+}
+
+func parseLinuxDoTokenResponse(body string) (*linuxDoTokenResponse, bool) {
+	body = strings.TrimSpace(body)
+	if body == "" {
+		return nil, false
+	}
+
+	accessToken := strings.TrimSpace(getGJSON(body, "access_token"))
+	if accessToken != "" {
+		tokenType := strings.TrimSpace(getGJSON(body, "token_type"))
+		refreshToken := strings.TrimSpace(getGJSON(body, "refresh_token"))
+		scope := strings.TrimSpace(getGJSON(body, "scope"))
+		expiresIn := gjson.Get(body, "expires_in").Int()
+		return &linuxDoTokenResponse{
+			AccessToken:  accessToken,
+			TokenType:    tokenType,
+			ExpiresIn:    expiresIn,
+			RefreshToken: refreshToken,
+			Scope:        scope,
+		}, true
+	}
+
+	values, err := url.ParseQuery(body)
+	if err != nil {
+		return nil, false
+	}
+	accessToken = strings.TrimSpace(values.Get("access_token"))
+	if accessToken == "" {
+		return nil, false
+	}
+	expiresIn := int64(0)
+	if raw := strings.TrimSpace(values.Get("expires_in")); raw != "" {
+		if v, err := strconv.ParseInt(raw, 10, 64); err == nil {
+			expiresIn = v
+		}
+	}
+	return &linuxDoTokenResponse{
+		AccessToken:  accessToken,
+		TokenType:    strings.TrimSpace(values.Get("token_type")),
+		ExpiresIn:    expiresIn,
+		RefreshToken: strings.TrimSpace(values.Get("refresh_token")),
+		Scope:        strings.TrimSpace(values.Get("scope")),
+	}, true
+}
+
+func getGJSON(body string, path string) string {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return ""
+	}
+	res := gjson.Get(body, path)
+	if !res.Exists() {
+		return ""
+	}
+	return res.String()
+}
+
+func truncateLogValue(value string, maxLen int) string {
+	value = strings.TrimSpace(value)
+	if value == "" || maxLen <= 0 {
+		return ""
+	}
+	if len(value) <= maxLen {
+		return value
+	}
+	value = value[:maxLen]
+	for !utf8.ValidString(value) {
+		value = value[:len(value)-1]
+	}
+	return value
+}
+
+func singleLine(value string) string {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return ""
+	}
+	return strings.Join(strings.Fields(value), " ")
+}
+
+func sanitizeFrontendRedirectPath(path string) string {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return ""
+	}
+	if len(path) > linuxDoOAuthMaxRedirectLen {
+		return ""
+	}
+	// 只允许同源相对路径（避免开放重定向）。
+	if !strings.HasPrefix(path, "/") {
+		return ""
+	}
+	if strings.HasPrefix(path, "//") {
+		return ""
+	}
+	if strings.Contains(path, "://") {
+		return ""
+	}
+	if strings.ContainsAny(path, "\r\n") {
+		return ""
+	}
+	return path
+}
+
+func isRequestHTTPS(c *gin.Context) bool {
+	if c.Request.TLS != nil {
+		return true
+	}
+	proto := strings.ToLower(strings.TrimSpace(c.GetHeader("X-Forwarded-Proto")))
+	return proto == "https"
+}
+
+func encodeCookieValue(value string) string {
+	return base64.RawURLEncoding.EncodeToString([]byte(value))
+}
+
+func decodeCookieValue(value string) (string, error) {
+	raw, err := base64.RawURLEncoding.DecodeString(value)
+	if err != nil {
+		return "", err
+	}
+	return string(raw), nil
+}
+
+func readCookieDecoded(c *gin.Context, name string) (string, error) {
+	ck, err := c.Request.Cookie(name)
+	if err != nil {
+		return "", err
+	}
+	return decodeCookieValue(ck.Value)
+}
+
+func setCookie(c *gin.Context, name string, value string, maxAgeSec int, secure bool) {
+	http.SetCookie(c.Writer, &http.Cookie{
+		Name:     name,
+		Value:    value,
+		Path:     linuxDoOAuthCookiePath,
+		MaxAge:   maxAgeSec,
+		HttpOnly: true,
+		Secure:   secure,
+		SameSite: http.SameSiteLaxMode,
+	})
+}
+
+func clearCookie(c *gin.Context, name string, secure bool) {
+	http.SetCookie(c.Writer, &http.Cookie{
+		Name:     name,
+		Value:    "",
+		Path:     linuxDoOAuthCookiePath,
+		MaxAge:   -1,
+		HttpOnly: true,
+		Secure:   secure,
+		SameSite: http.SameSiteLaxMode,
+	})
+}
+
+func truncateFragmentValue(value string) string {
+	value = strings.TrimSpace(value)
+	if value == "" {
+		return ""
+	}
+	if len(value) > linuxDoOAuthMaxFragmentValueLen {
+		value = value[:linuxDoOAuthMaxFragmentValueLen]
+		for !utf8.ValidString(value) {
+			value = value[:len(value)-1]
+		}
+	}
+	return value
+}
+
+func buildBearerAuthorization(tokenType, accessToken string) (string, error) {
+	tokenType = strings.TrimSpace(tokenType)
+	if tokenType == "" {
+		tokenType = "Bearer"
+	}
+	if !strings.EqualFold(tokenType, "Bearer") {
+		return "", fmt.Errorf("unsupported token_type: %s", tokenType)
+	}
+
+	accessToken = strings.TrimSpace(accessToken)
+	if accessToken == "" {
+		return "", errors.New("missing access_token")
+	}
+	if strings.ContainsAny(accessToken, " \t\r\n") {
+		return "", errors.New("access_token contains whitespace")
+	}
+	return "Bearer " + accessToken, nil
+}
+
+func isSafeLinuxDoSubject(subject string) bool {
+	subject = strings.TrimSpace(subject)
+	if subject == "" || len(subject) > linuxDoOAuthMaxSubjectLen {
+		return false
+	}
+	for _, r := range subject {
+		switch {
+		case r >= '0' && r <= '9':
+		case r >= 'a' && r <= 'z':
+		case r >= 'A' && r <= 'Z':
+		case r == '_' || r == '-':
+		default:
+			return false
+		}
+	}
+	return true
+}
+
+func linuxDoSyntheticEmail(subject string) string {
+	subject = strings.TrimSpace(subject)
+	if subject == "" {
+		return ""
+	}
+	return "linuxdo-" + subject + service.LinuxDoConnectSyntheticEmailDomain
+}
--- a/backend/internal/handler/auth_linuxdo_oauth_test.go
+++ b/backend/internal/handler/auth_linuxdo_oauth_test.go
@@ -0,0 +1,108 @@
+package handler
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/Wei-Shaw/sub2api/internal/config"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSanitizeFrontendRedirectPath(t *testing.T) {
+	require.Equal(t, "/dashboard", sanitizeFrontendRedirectPath("/dashboard"))
+	require.Equal(t, "/dashboard", sanitizeFrontendRedirectPath(" /dashboard "))
+	require.Equal(t, "", sanitizeFrontendRedirectPath("dashboard"))
+	require.Equal(t, "", sanitizeFrontendRedirectPath("//evil.com"))
+	require.Equal(t, "", sanitizeFrontendRedirectPath("https://evil.com"))
+	require.Equal(t, "", sanitizeFrontendRedirectPath("/\nfoo"))
+
+	long := "/" + strings.Repeat("a", linuxDoOAuthMaxRedirectLen)
+	require.Equal(t, "", sanitizeFrontendRedirectPath(long))
+}
+
+func TestBuildBearerAuthorization(t *testing.T) {
+	auth, err := buildBearerAuthorization("", "token123")
+	require.NoError(t, err)
+	require.Equal(t, "Bearer token123", auth)
+
+	auth, err = buildBearerAuthorization("bearer", "token123")
+	require.NoError(t, err)
+	require.Equal(t, "Bearer token123", auth)
+
+	_, err = buildBearerAuthorization("MAC", "token123")
+	require.Error(t, err)
+
+	_, err = buildBearerAuthorization("Bearer", "token 123")
+	require.Error(t, err)
+}
+
+func TestLinuxDoParseUserInfoParsesIDAndUsername(t *testing.T) {
+	cfg := config.LinuxDoConnectConfig{
+		UserInfoURL: "https://connect.linux.do/api/user",
+	}
+
+	email, username, subject, err := linuxDoParseUserInfo(`{"id":123,"username":"alice"}`, cfg)
+	require.NoError(t, err)
+	require.Equal(t, "123", subject)
+	require.Equal(t, "alice", username)
+	require.Equal(t, "linuxdo-123@linuxdo-connect.invalid", email)
+}
+
+func TestLinuxDoParseUserInfoDefaultsUsername(t *testing.T) {
+	cfg := config.LinuxDoConnectConfig{
+		UserInfoURL: "https://connect.linux.do/api/user",
+	}
+
+	email, username, subject, err := linuxDoParseUserInfo(`{"id":"123"}`, cfg)
+	require.NoError(t, err)
+	require.Equal(t, "123", subject)
+	require.Equal(t, "linuxdo_123", username)
+	require.Equal(t, "linuxdo-123@linuxdo-connect.invalid", email)
+}
+
+func TestLinuxDoParseUserInfoRejectsUnsafeSubject(t *testing.T) {
+	cfg := config.LinuxDoConnectConfig{
+		UserInfoURL: "https://connect.linux.do/api/user",
+	}
+
+	_, _, _, err := linuxDoParseUserInfo(`{"id":"123@456"}`, cfg)
+	require.Error(t, err)
+
+	tooLong := strings.Repeat("a", linuxDoOAuthMaxSubjectLen+1)
+	_, _, _, err = linuxDoParseUserInfo(`{"id":"`+tooLong+`"}`, cfg)
+	require.Error(t, err)
+}
+
+func TestParseOAuthProviderErrorJSON(t *testing.T) {
+	code, desc := parseOAuthProviderError(`{"error":"invalid_client","error_description":"bad secret"}`)
+	require.Equal(t, "invalid_client", code)
+	require.Equal(t, "bad secret", desc)
+}
+
+func TestParseOAuthProviderErrorForm(t *testing.T) {
+	code, desc := parseOAuthProviderError("error=invalid_request&error_description=Missing+code_verifier")
+	require.Equal(t, "invalid_request", code)
+	require.Equal(t, "Missing code_verifier", desc)
+}
+
+func TestParseLinuxDoTokenResponseJSON(t *testing.T) {
+	token, ok := parseLinuxDoTokenResponse(`{"access_token":"t1","token_type":"Bearer","expires_in":3600,"scope":"user"}`)
+	require.True(t, ok)
+	require.Equal(t, "t1", token.AccessToken)
+	require.Equal(t, "Bearer", token.TokenType)
+	require.Equal(t, int64(3600), token.ExpiresIn)
+	require.Equal(t, "user", token.Scope)
+}
+
+func TestParseLinuxDoTokenResponseForm(t *testing.T) {
+	token, ok := parseLinuxDoTokenResponse("access_token=t2&token_type=bearer&expires_in=60")
+	require.True(t, ok)
+	require.Equal(t, "t2", token.AccessToken)
+	require.Equal(t, "bearer", token.TokenType)
+	require.Equal(t, int64(60), token.ExpiresIn)
+}
+
+func TestSingleLineStripsWhitespace(t *testing.T) {
+	require.Equal(t, "hello world", singleLine("hello\r\nworld"))
+	require.Equal(t, "", singleLine("\n\t\r"))
+}
--- a/backend/internal/handler/dto/settings.go
+++ b/backend/internal/handler/dto/settings.go
@@ -17,6 +17,11 @@ type SystemSettings struct {
 	TurnstileSiteKey             string `json:"turnstile_site_key"`
 	TurnstileSecretKeyConfigured bool   `json:"turnstile_secret_key_configured"`

+	LinuxDoConnectEnabled                bool   `json:"linuxdo_connect_enabled"`
+	LinuxDoConnectClientID               string `json:"linuxdo_connect_client_id"`
+	LinuxDoConnectClientSecretConfigured bool   `json:"linuxdo_connect_client_secret_configured"`
+	LinuxDoConnectRedirectURL            string `json:"linuxdo_connect_redirect_url"`
+
 	SiteName     string `json:"site_name"`
 	SiteLogo     string `json:"site_logo"`
 	SiteSubtitle string `json:"site_subtitle"`
@@ -50,5 +55,6 @@ type PublicSettings struct {
 	APIBaseURL          string `json:"api_base_url"`
 	ContactInfo         string `json:"contact_info"`
 	DocURL              string `json:"doc_url"`
+	LinuxDoOAuthEnabled bool   `json:"linuxdo_oauth_enabled"`
 	Version             string `json:"version"`
 }
--- a/backend/internal/handler/setting_handler.go
+++ b/backend/internal/handler/setting_handler.go
@@ -42,6 +42,7 @@ func (h *SettingHandler) GetPublicSettings(c *gin.Context) {
 		APIBaseURL:          settings.APIBaseURL,
 		ContactInfo:         settings.ContactInfo,
 		DocURL:              settings.DocURL,
+		LinuxDoOAuthEnabled: settings.LinuxDoOAuthEnabled,
 		Version:             h.version,
 	})
 }