이미지 파생 파일 생성 안정화

server/utils/post-thumbnail-image.js

@@ -1,5 +1,5 @@
 import { existsSync } from 'node:fs'
-import { mkdir, stat } from 'node:fs/promises'
+import { mkdir, rename, rm, stat } from 'node:fs/promises'
 import { dirname, extname, join, posix } from 'node:path'
 import sharp from 'sharp'
 import {
@@ -41,6 +41,72 @@ const postThumbnailExtension = '.webp'
 const supportedPostThumbnailExtensions = new Set(['.jpg', '.jpeg', '.png', '.webp'])
 const supportedPostThumbnailTypes = new Set(['image/jpeg', 'image/png', 'image/webp'])
 
+/**
+ * 임시 이미지 출력 경로를 만든다.
+ * @param {string} filePath - 최종 저장 경로
+ * @returns {string} 임시 저장 경로
+ */
+const createTemporaryImagePath = (filePath) => `${filePath}.${process.pid}-${Date.now()}-${Math.random().toString(36).slice(2)}.tmp`
+
+/**
+ * 파일이 있으면 조용히 제거한다.
+ * @param {string} filePath - 제거할 파일 경로
+ * @returns {Promise<void>} 제거 결과
+ */
+const removeImageFileIfExists = async (filePath) => {
+  if (!filePath) {
+    return
+  }
+
+  await rm(filePath, { force: true }).catch(() => {})
+}
+
+/**
+ * 생성된 이미지 파일이 실제로 읽히는지 확인한다.
+ * @param {string} filePath - 검사할 이미지 파일 경로
+ * @returns {Promise<boolean>} 유효한 이미지이면 true
+ */
+const isGeneratedImageReadable = async (filePath) => {
+  const fileStat = await stat(filePath).catch(() => null)
+
+  if (!fileStat?.isFile() || fileStat.size <= 0) {
+    return false
+  }
+
+  try {
+    await sharp(filePath).metadata()
+    return true
+  } catch {
+    return false
+  }
+}
+
+/**
+ * 임시 파일로 이미지를 만든 뒤 검증이 끝나면 최종 파일로 교체한다.
+ * @param {string} targetPath - 최종 저장 경로
+ * @param {(temporaryPath: string) => Promise<void>} writeTemporaryImage - 임시 이미지 생성 함수
+ * @returns {Promise<boolean>} 생성 성공 여부
+ */
+const writeVerifiedDerivativeImage = async (targetPath, writeTemporaryImage) => {
+  const temporaryPath = createTemporaryImagePath(targetPath)
+
+  try {
+    await mkdir(dirname(targetPath), { recursive: true })
+    await writeTemporaryImage(temporaryPath)
+
+    if (!await isGeneratedImageReadable(temporaryPath)) {
+      throw new Error('INVALID_DERIVATIVE_IMAGE')
+    }
+
+    await rename(temporaryPath, targetPath)
+    return true
+  } catch {
+    await removeImageFileIfExists(temporaryPath)
+    await removeImageFileIfExists(targetPath)
+    return false
+  }
+}
+
 /**
  * URL 경로 조각을 파일 시스템 경로용 문자열로 디코딩한다.
  * @param {string} value - URL 경로 조각
@@ -302,9 +368,7 @@ export const createPostThumbnailForImageUrl = async (imageUrl) => {
     return ''
   }
 
-  await mkdir(dirname(thumbnailPath), { recursive: true })
-
-  await sharp(sourcePath)
+  const created = await writeVerifiedDerivativeImage(thumbnailPath, (temporaryPath) => sharp(sourcePath)
     .rotate()
     .resize({
       width: POST_THUMBNAIL_WIDTH,
@@ -314,9 +378,9 @@ export const createPostThumbnailForImageUrl = async (imageUrl) => {
       withoutEnlargement: true
     })
     .webp({ quality: POST_THUMBNAIL_QUALITY })
-    .toFile(thumbnailPath)
+    .toFile(temporaryPath))
 
-  return thumbnailUrl
+  return created ? thumbnailUrl : ''
 }
 
 /**
@@ -339,9 +403,7 @@ export const createPageCoverThumbnailForImageUrl = async (imageUrl) => {
     return ''
   }
 
-  await mkdir(dirname(thumbnailPath), { recursive: true })
-
-  await sharp(sourcePath)
+  const created = await writeVerifiedDerivativeImage(thumbnailPath, (temporaryPath) => sharp(sourcePath)
     .rotate()
     .resize({
       width: PAGE_COVER_THUMBNAIL_WIDTH,
@@ -351,9 +413,9 @@ export const createPageCoverThumbnailForImageUrl = async (imageUrl) => {
       withoutEnlargement: true
     })
     .webp({ quality: PAGE_COVER_THUMBNAIL_QUALITY })
-    .toFile(thumbnailPath)
+    .toFile(temporaryPath))
 
-  return thumbnailUrl
+  return created ? thumbnailUrl : ''
 }
 
 /**
@@ -378,39 +440,40 @@ export const createPostBodyThumbnailForImageUrl = async (imageUrl) => {
     return ''
   }
 
-  try {
-    await mkdir(dirname(thumbnailPath), { recursive: true })
+  const createdBody = await writeVerifiedDerivativeImage(thumbnailPath, (temporaryPath) => sharp(sourcePath)
+    .rotate()
+    .resize({
+      width: POST_BODY_IMAGE_WIDTH,
+      fit: 'inside',
+      withoutEnlargement: true
+    })
+    .webp({ quality: POST_BODY_IMAGE_QUALITY })
+    .toFile(temporaryPath))
+  const createdPreview = await writeVerifiedDerivativeImage(previewThumbnailPath, (temporaryPath) => sharp(sourcePath)
+    .rotate()
+    .resize({
+      width: POST_BODY_PREVIEW_IMAGE_WIDTH,
+      fit: 'inside',
+      withoutEnlargement: true
+    })
+    .webp({ quality: POST_BODY_IMAGE_QUALITY })
+    .toFile(temporaryPath))
+  const createdLightbox = await writeVerifiedDerivativeImage(lightboxThumbnailPath, (temporaryPath) => sharp(sourcePath)
+    .rotate()
+    .resize({
+      width: POST_LIGHTBOX_IMAGE_WIDTH,
+      fit: 'inside',
+      withoutEnlargement: true
+    })
+    .webp({ quality: POST_BODY_IMAGE_QUALITY })
+    .toFile(temporaryPath))
 
-    await sharp(sourcePath)
-      .rotate()
-      .resize({
-        width: POST_BODY_IMAGE_WIDTH,
-        fit: 'inside',
-        withoutEnlargement: true
-      })
-      .webp({ quality: POST_BODY_IMAGE_QUALITY })
-      .toFile(thumbnailPath)
-
-    await sharp(sourcePath)
-      .rotate()
-      .resize({
-        width: POST_BODY_PREVIEW_IMAGE_WIDTH,
-        fit: 'inside',
-        withoutEnlargement: true
-      })
-      .webp({ quality: POST_BODY_IMAGE_QUALITY })
-      .toFile(previewThumbnailPath)
-
-    await sharp(sourcePath)
-      .rotate()
-      .resize({
-        width: POST_LIGHTBOX_IMAGE_WIDTH,
-        fit: 'inside',
-        withoutEnlargement: true
-      })
-      .webp({ quality: POST_BODY_IMAGE_QUALITY })
-      .toFile(lightboxThumbnailPath)
-  } catch {
+  if (!createdBody || !createdPreview || !createdLightbox) {
+    await Promise.all([
+      removeImageFileIfExists(thumbnailPath),
+      removeImageFileIfExists(previewThumbnailPath),
+      removeImageFileIfExists(lightboxThumbnailPath)
+    ])
     return ''
   }