backend-celestia-trace/middleware/auth.go

package middleware

import (
	"net/http"
	"strings"

	"github.com/celestia-trace/backend/config"
	"github.com/gin-gonic/gin"
	"github.com/golang-jwt/jwt/v5"
)

// Auth middleware validates JWT token
func Auth(cfg *config.Config) gin.HandlerFunc {
	return func(c *gin.Context) {
		authHeader := c.GetHeader("Authorization")
		if authHeader == "" {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "missing authorization header"})
			c.Abort()
			return
		}

		parts := strings.Split(authHeader, " ")
		if len(parts) != 2 || parts[0] != "Bearer" {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "invalid authorization header format"})
			c.Abort()
			return
		}

		tokenString := parts[1]
		token, err := jwt.Parse(tokenString, func(token *jwt.Token) (interface{}, error) {
			if token.Method.Alg() != jwt.SigningMethodHS256.Alg() {
				return nil, jwt.ErrSignatureInvalid
			}
			return []byte(cfg.JWTSecret), nil
		}, jwt.WithIssuer("celestia-trace"), jwt.WithExpirationRequired())

		if err != nil || !token.Valid {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "invalid token"})
			c.Abort()
			return
		}

		claims, ok := token.Claims.(jwt.MapClaims)
		if !ok {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "invalid token claims"})
			c.Abort()
			return
		}

		userID, ok := claims["sub"].(string)
		if !ok {
			c.JSON(http.StatusUnauthorized, gin.H{"code": 401, "message": "invalid subject in token"})
			c.Abort()
			return
		}

		// Set user ID for downstream handlers
		c.Set("userID", userID)
		if sessionID, ok := claims["sid"].(string); ok {
			c.Set("sessionID", sessionID)
		}
		c.Next()
	}
}