Add JWT authorization functionality.

internal/auth/middleware.go

@@ -0,0 +1,41 @@
+package auth
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+const CtxUsernameKey = "username"
+
+func Middleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		h := c.GetHeader("Authorization")
+		if h == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "missing Authorization header"})
+			return
+		}
+
+		const prefix = "Bearer "
+		if !strings.HasPrefix(h, prefix) {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "expected Bearer token"})
+			return
+		}
+
+		raw := strings.TrimSpace(strings.TrimPrefix(h, prefix))
+		if raw == "" {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "empty token"})
+			return
+		}
+
+		claims, err := ParseAccessToken(raw)
+		if err != nil {
+			c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
+			return
+		}
+
+		c.Set(CtxUsernameKey, claims.Username)
+		c.Next()
+	}
+}