fix(oidc): use TOTP as state verification to replace the static 'stat…

…e' parameter (#4665)

server/handles/ssologin.go

@@ -1,11 +1,13 @@
 package handles
 
 import (
+	"encoding/base32"
 	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
 	"strings"
+	"time"
 
 	"github.com/alist-org/alist/v3/internal/conf"
 	"github.com/alist-org/alist/v3/internal/db"
@@ -15,9 +17,20 @@ import (
 	"github.com/coreos/go-oidc"
 	"github.com/gin-gonic/gin"
 	"github.com/go-resty/resty/v2"
+	"github.com/pquerna/otp"
+	"github.com/pquerna/otp/totp"
 	"golang.org/x/oauth2"
 )
 
+var opts = totp.ValidateOpts{
+	// state verify won't expire in 30 secs, which is quite enough for the callback
+	Period: 30,
+	Skew: 1,
+	// in some OIDC providers(such as Authelia), state parameter must be at least 8 characters
+	Digits: otp.DigitsEight,
+	Algorithm: otp.AlgorithmSHA1,
+}
+
 func SSOLoginRedirect(c *gin.Context) {
 	method := c.Query("method")
 	enabled := setting.GetBool(conf.SSOLoginEnabled)
@@ -62,7 +75,13 @@ func SSOLoginRedirect(c *gin.Context) {
 				common.ErrorStrResp(c, err.Error(), 400)
 				return
 			}
-			c.Redirect(http.StatusFound, oauth2Config.AuthCodeURL("state"))
+			// generate state parameter
+			state,err := totp.GenerateCodeCustom(base32.StdEncoding.EncodeToString([]byte(oauth2Config.ClientSecret)), time.Now(), opts)
+			if err != nil {
+				common.ErrorStrResp(c, err.Error(), 400)
+				return
+			}
+			c.Redirect(http.StatusFound, oauth2Config.AuthCodeURL(state))
 			return
 		default:
 			common.ErrorStrResp(c, "invalid platform", 400)
@@ -117,6 +136,17 @@ func OIDCLoginCallback(c *gin.Context) {
 		common.ErrorResp(c, err, 400)
 		return
 	}
+	// add state verify process
+	stateVerification, err := totp.ValidateCustom(c.Query("state"), base32.StdEncoding.EncodeToString([]byte(oauth2Config.ClientSecret)), time.Now(), opts)
+	if err != nil {
+		common.ErrorResp(c, err, 400)
+		return
+	}
+	if !stateVerification {
+		common.ErrorStrResp(c, "incorrect or expired state parameter", 400)
+		return
+	}
+
 	oauth2Token, err := oauth2Config.Exchange(c, c.Query("code"))
 	if err != nil {
 		common.ErrorResp(c, err, 400)