파일 업로드시의 체크섬 검사 구현

drizzle/0002_good_talisman.sql

@@ -0,0 +1 @@
+ALTER TABLE `file` ADD `encrypted_content_hash` text NOT NULL;

drizzle/meta/_journal.json

@@ -15,6 +15,13 @@
       "when": 1736720831242,
       "tag": "0001_blushing_alice",
       "breakpoints": true
+    },
+    {
+      "idx": 2,
+      "version": "6",
+      "when": 1737191517463,
+      "tag": "0002_good_talisman",
+      "breakpoints": true
     }
   ]
 }

src/lib/modules/file/upload.ts

@@ -8,6 +8,7 @@ import {
   wrapDataKey,
   encryptData,
   encryptString,
+  digestMessage,
   signMessageHmac,
 } from "$lib/modules/crypto";
 import type {
@@ -97,6 +98,8 @@ const encryptFile = limitFunction(
     const dataKeyWrapped = await wrapDataKey(dataKey, masterKey.key);
 
     const fileEncrypted = await encryptData(fileBuffer, dataKey);
+    const fileEncryptedHash = encodeToBase64(await digestMessage(fileEncrypted.ciphertext));
+
     const nameEncrypted = await encryptString(file.name, dataKey);
     const createdAtEncrypted =
       createdAt && (await encryptString(createdAt.getTime().toString(), dataKey));
@@ -110,8 +113,9 @@ const encryptFile = limitFunction(
     return {
       dataKeyWrapped,
       dataKeyVersion,
-      fileEncrypted,
       fileType,
+      fileEncrypted,
+      fileEncryptedHash,
       nameEncrypted,
       createdAtEncrypted,
       lastModifiedAtEncrypted,
@@ -184,8 +188,9 @@ export const uploadFile = async (
     const {
       dataKeyWrapped,
       dataKeyVersion,
-      fileEncrypted,
       fileType,
+      fileEncrypted,
+      fileEncryptedHash,
       nameEncrypted,
       createdAtEncrypted,
       lastModifiedAtEncrypted,
@@ -212,6 +217,7 @@ export const uploadFile = async (
       } as FileUploadRequest),
     );
     form.set("content", new Blob([fileEncrypted.ciphertext]));
+    form.set("checksum", fileEncryptedHash);
 
     await requestFileUpload(status, form);
     return true;

src/lib/server/db/file.ts

@@ -26,6 +26,7 @@ export interface NewFileParams {
   contentHmac: string | null;
   contentType: string;
   encContentIv: string;
+  encContentHash: string;
   encName: string;
   encNameIv: string;
   encCreatedAt: string | null;
@@ -198,11 +199,12 @@ export const registerFile = async (params: NewFileParams) => {
           userId: params.userId,
           mekVersion: params.mekVersion,
           hskVersion: params.hskVersion,
-          contentHmac: params.contentHmac,
-          contentType: params.contentType,
           encDek: params.encDek,
           dekVersion: params.dekVersion,
+          contentHmac: params.contentHmac,
+          contentType: params.contentType,
           encContentIv: params.encContentIv,
+          encContentHash: params.encContentHash,
           encName: { ciphertext: params.encName, iv: params.encNameIv },
           encCreatedAt:
             params.encCreatedAt && params.encCreatedAtIv

src/lib/server/db/schema/file.ts

@@ -60,6 +60,7 @@ export const file = sqliteTable(
     contentHmac: text("content_hmac"), // Base64
     contentType: text("content_type").notNull(),
     encContentIv: text("encrypted_content_iv").notNull(), // Base64
+    encContentHash: text("encrypted_content_hash").notNull(), // Base64
     encName: ciphertext("encrypted_name").notNull(),
     encCreatedAt: ciphertext("encrypted_created_at"),
     encLastModifiedAt: ciphertext("encrypted_last_modified_at").notNull(),

src/lib/server/services/file.ts

@@ -1,4 +1,5 @@
 import { error } from "@sveltejs/kit";
+import { createHash } from "crypto";
 import { createReadStream, createWriteStream } from "fs";
 import { mkdir, stat, unlink } from "fs/promises";
 import { dirname } from "path";
@@ -95,8 +96,9 @@ const safeUnlink = async (path: string) => {
 };
 
 export const uploadFile = async (
-  params: Omit<NewFileParams, "path">,
+  params: Omit<NewFileParams, "path" | "encContentHash">,
   encContentStream: Readable,
+  encContentHash: Promise<string>,
 ) => {
   const oneDayAgo = new Date(Date.now() - 24 * 60 * 60 * 1000);
   const oneMinuteLater = new Date(Date.now() + 60 * 1000);
@@ -108,16 +110,30 @@ export const uploadFile = async (
   await mkdir(dirname(path), { recursive: true });
 
   try {
-    await pipeline(encContentStream, createWriteStream(path, { flags: "wx", mode: 0o600 }));
+    const hashStream = createHash("sha256");
+    const [_, hash] = await Promise.all([
+      pipeline(encContentStream, hashStream, createWriteStream(path, { flags: "wx", mode: 0o600 })),
+      encContentHash,
+    ]);
+    if (hashStream.digest("base64") != hash) {
+      throw new Error("Invalid checksum");
+    }
+
     await registerFile({
       ...params,
       path,
+      encContentHash: hash,
     });
   } catch (e) {
     await safeUnlink(path);
 
     if (e instanceof IntegrityError && e.message === "Inactive MEK version") {
       error(400, "Invalid MEK version");
+    } else if (
+      e instanceof Error &&
+      (e.message === "Invalid request body" || e.message === "Invalid checksum")
+    ) {
+      error(400, "Invalid request body");
     }
     throw e;
   }

src/routes/api/file/upload/+server.ts

@@ -67,27 +67,39 @@ export const POST: RequestHandler = async ({ locals, request }) => {
 
     let metadata: FileMetadata | null = null;
     let content: Readable | null = null;
+    const checksum = new Promise<string>((resolveChecksum, rejectChecksum) => {
+      bb.on(
+        "field",
+        handler(async (fieldname, val) => {
+          if (fieldname === "metadata") {
+            if (!metadata) {
+              // Ignore subsequent metadata fields
+              metadata = parseFileMetadata(userId, val);
+            }
+          } else if (fieldname === "checksum") {
+            resolveChecksum(val); // Ignore subsequent checksum fields
+          } else {
+            error(400, "Invalid request body");
+          }
+        }),
+      );
+      bb.on(
+        "file",
+        handler(async (fieldname, file) => {
+          if (fieldname !== "content") error(400, "Invalid request body");
+          if (!metadata || content) error(400, "Invalid request body");
+          content = file;
 
-    bb.on(
-      "field",
-      handler(async (fieldname, val) => {
-        if (fieldname !== "metadata") error(400, "Invalid request body");
-        if (metadata || content) error(400, "Invalid request body");
-        metadata = parseFileMetadata(userId, val);
-      }),
-    );
-    bb.on(
-      "file",
-      handler(async (fieldname, file) => {
-        if (fieldname !== "content") error(400, "Invalid request body");
-        if (!metadata || content) error(400, "Invalid request body");
-        content = file;
-
-        await uploadFile(metadata, content);
-        resolve(text("File uploaded", { headers: { "Content-Type": "text/plain" } }));
-      }),
-    );
-    bb.on("error", (e) => content?.emit("error", e) ?? reject(e));
+          await uploadFile(metadata, content, checksum);
+          resolve(text("File uploaded", { headers: { "Content-Type": "text/plain" } }));
+        }),
+      );
+      bb.on("finish", () => rejectChecksum(new Error("Invalid request body")));
+      bb.on("error", (e) => {
+        content?.emit("error", e) ?? reject(e);
+        rejectChecksum(e);
+      });
+    });
 
     request.body!.pipeTo(Writable.toWeb(bb)).catch(() => {}); // busboy will handle the error
   });