fea: 添加检测图片类型功能

backend/src/index.ts

@@ -1,3 +1,4 @@
+import { fileTypeFromBuffer } from "file-type";
 import { Hono } from "hono";
 import { validator } from "hono/validator";
 
@@ -28,7 +29,7 @@ const app = appTmp.basePath("/watermark")
  * param: outputType: 输出的文件类型，只允许 jpeg | png
  */
 app.post("/encode",
-    validator("form", (val, c) => {
+    validator("form", async (val, c) => {
         const image = val.image
         const payload = val.payload
         const strength = val.strength
@@ -62,6 +63,26 @@ app.post("/encode",
             })
         }
 
+        // 通过魔术数字判断文件真实类型
+        const imageBuffer = await (image as File).arrayBuffer()
+        const unit8Image = new Uint8Array(imageBuffer)
+        const imageType = await fileTypeFromBuffer(unit8Image)
+        if (!imageType) {
+            c.status(400)
+            return c.json({
+                code: 400,
+                msg: "Image type is invalid, must be jpeg or png"
+            })
+        }
+        if (!["image/png", "image/jpeg"].includes(imageType.mime)) {
+            c.status(400)
+            return c.json({
+                code: 400,
+                msg: "Image type is invalid, must be jpeg or png"
+            })
+        }
+        // DONE
+
         const MAX_IMAGE_SIZE = 10 * 1024 * 1024
         if ((image as File).size > MAX_IMAGE_SIZE) {
             c.status(400)