feat(storage): add CloudFront CDN file strategy

 - Add `FileSources.cloudfront` enum and `cloudfrontConfigSchema` to data-provider
- Implement `packages/api/src/cdn/cloudfront.ts` for initialization and config access
- Implement `packages/api/src/storage/cloudfront/crud.ts` for URL generation,
  signed URLs, S3-delegated uploads/deletes, and optional cache invalidation
- Refactor `S3ImageService` into a unified `ImageService` class with injected
  `saveBuffer` fn, eliminating many lines of per-strategy duplication
- Refactor `initializeFileStorage` to deduplicate and handle `fileStrategies` config
- Propagate `cloudfront` config through `AppConfig` and `AppService`
- Add CloudFront strategy to `strategies.js` and `librechat.example.yaml`
- Added unit tests across cdn/cloudfront, storage/cloudfront/crud, and ImageService

Author: AtefBellaaj

api/server/services/Files/strategies.js

@@ -2,14 +2,20 @@ const { FileSources } = require('librechat-data-provider');
 const {
   getS3URL,
   saveURLToS3,
+  ImageService,
   parseDocument,
   uploadFileToS3,
-  S3ImageService,
   saveBufferToS3,
   getS3FileStream,
   deleteFileFromS3,
+  getCloudFrontURL,
   uploadMistralOCR,
+  saveURLToCloudFront,
   uploadAzureMistralOCR,
+  uploadFileToCloudFront,
+  saveBufferToCloudFront,
+  getCloudFrontFileStream,
+  deleteFileFromCloudFront,
   uploadGoogleVertexMistralOCR,
 } = require('@librechat/api');
 const {
@@ -37,15 +43,21 @@ const {
 const { resizeImageBuffer } = require('./images/resize');
 const { updateUser, updateFile } = require('~/models');
 
-const s3ImageService = new S3ImageService({
+const imageServiceDeps = {
   resizeImageBuffer,
   updateUser,
   updateFile,
-});
+};
 
-const uploadImageToS3 = (params) => s3ImageService.uploadImageToS3(params);
+const s3ImageService = new ImageService(saveBufferToS3, imageServiceDeps);
+const uploadImageToS3 = (params) => s3ImageService.uploadImage(params);
 const prepareImageURLS3 = (_req, file) => s3ImageService.prepareImageURL(file);
 const processS3Avatar = (params) => s3ImageService.processAvatar(params);
+
+const cloudFrontImageService = new ImageService(saveBufferToCloudFront, imageServiceDeps);
+const uploadImageToCloudFront = (params) => cloudFrontImageService.uploadImage(params);
+const prepareCloudFrontImageURL = (_req, file) => cloudFrontImageService.prepareImageURL(file);
+const processCloudFrontAvatar = (params) => cloudFrontImageService.processAvatar(params);
 const {
   saveBufferToAzure,
   saveURLToAzure,
@@ -109,6 +121,22 @@ const s3Strategy = () => ({
   getDownloadStream: getS3FileStream,
 });
 
+/**
+ * CloudFront CDN Strategy Functions
+ * Uses S3 for storage, CloudFront for URL delivery
+ */
+const cloudfrontStrategy = () => ({
+  handleFileUpload: uploadFileToCloudFront,
+  saveURL: saveURLToCloudFront,
+  getFileURL: getCloudFrontURL,
+  deleteFile: deleteFileFromCloudFront,
+  saveBuffer: saveBufferToCloudFront,
+  prepareImagePayload: prepareCloudFrontImageURL,
+  processAvatar: processCloudFrontAvatar,
+  handleImageUpload: uploadImageToCloudFront,
+  getDownloadStream: getCloudFrontFileStream,
+});
+
 /**
  * Azure Blob Storage Strategy Functions
  *
@@ -291,6 +319,8 @@ const getStrategyFunctions = (fileSource) => {
     return vectorStrategy();
   } else if (fileSource === FileSources.s3) {
     return s3Strategy();
+  } else if (fileSource === FileSources.cloudfront) {
+    return cloudfrontStrategy();
   } else if (fileSource === FileSources.execute_code) {
     return codeOutputStrategy();
   } else if (fileSource === FileSources.mistral_ocr) {

librechat.example.yaml

@@ -18,12 +18,26 @@ cache: true
 #   image: "firebase"   # Storage for uploaded images in chats
 #   document: "local"   # Storage for document uploads (PDFs, text files, etc.)
 
-# Available strategies: "local", "s3", "firebase"
+# Available strategies: "local", "s3", "firebase", "cloudfront"
 # If not specified, defaults to "local" for all file types
 # You can mix and match strategies based on your needs:
 # - Use S3 for avatars for fast global access
 # - Use Firebase for images with automatic optimization
 # - Use local storage for documents for privacy/compliance
+# - Use CloudFront for CDN-accelerated delivery (requires S3 + cloudfront config below)
+
+# CloudFront CDN Configuration (optional)
+# Use when fileStrategy: "cloudfront" or fileStrategies includes cloudfront
+# Requires: AWS_REGION, AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_BUCKET_NAME
+# For signed URLs: CLOUDFRONT_KEY_PAIR_ID, CLOUDFRONT_PRIVATE_KEY
+# cloudfront:
+#   domain: "https://d1234abcd.cloudfront.net"
+#   distributionId: "E1234ABCD"       # Required if invalidateOnDelete is true
+#   invalidateOnDelete: false         # Create cache invalidation on file delete
+#   # NOTE: imageSigning is not yet implemented. All URLs are unsigned regardless of value.
+#   # Do NOT restrict your CloudFront distribution to signed requests.
+#   imageSigning: "none"              # "none" | "cookies" | "url"
+#   urlExpiry: 3600                   # Signed URL expiry in seconds
 
 # Custom interface configuration
 interface: