refactor: Implement file access filtering based on agent permissions

- Introduced `filterFilesByAgentAccess` function to filter files based on user access through agents.
- Updated `getFiles` and `primeFiles` functions to utilize the new filtering logic.
- Moved `hasAccessToFilesViaAgent` function from the File model to permission services, adjusting imports accordingly
- Enhanced tests to ensure proper access control and filtering behavior for files associated with agents.

api/server/services/Files/permissions.js

@@ -0,0 +1,123 @@
+const { logger } = require('@librechat/data-schemas');
+const { PERMISSION_BITS } = require('librechat-data-provider');
+const { checkPermission } = require('~/server/services/PermissionService');
+const { getAgent } = require('~/models/Agent');
+
+/**
+ * Checks if a user has access to multiple files through a shared agent (batch operation)
+ * @param {string} userId - The user ID to check access for
+ * @param {string[]} fileIds - Array of file IDs to check
+ * @param {string} agentId - The agent ID that might grant access
+ * @returns {Promise<Map<string, boolean>>} Map of fileId to access status
+ */
+const hasAccessToFilesViaAgent = async (userId, fileIds, agentId) => {
+  const accessMap = new Map();
+
+  // Initialize all files as no access
+  fileIds.forEach((fileId) => accessMap.set(fileId, false));
+
+  try {
+    const agent = await getAgent({ id: agentId });
+
+    if (!agent) {
+      return accessMap;
+    }
+
+    // Check if user is the author - if so, grant access to all files
+    if (agent.author.toString() === userId) {
+      fileIds.forEach((fileId) => accessMap.set(fileId, true));
+      return accessMap;
+    }
+
+    // Check if user has at least VIEW permission on the agent
+    const hasViewPermission = await checkPermission({
+      userId,
+      resourceType: 'agent',
+      resourceId: agent._id,
+      requiredPermission: PERMISSION_BITS.VIEW,
+    });
+
+    if (!hasViewPermission) {
+      return accessMap;
+    }
+
+    // Check if user has EDIT permission (which would indicate collaborative access)
+    const hasEditPermission = await checkPermission({
+      userId,
+      resourceType: 'agent',
+      resourceId: agent._id,
+      requiredPermission: PERMISSION_BITS.EDIT,
+    });
+
+    // If user only has VIEW permission, they can't access files
+    // Only users with EDIT permission or higher can access agent files
+    if (!hasEditPermission) {
+      return accessMap;
+    }
+
+    // User has edit permissions - check which files are actually attached
+    const attachedFileIds = new Set();
+    if (agent.tool_resources) {
+      for (const [_resourceType, resource] of Object.entries(agent.tool_resources)) {
+        if (resource?.file_ids && Array.isArray(resource.file_ids)) {
+          resource.file_ids.forEach((fileId) => attachedFileIds.add(fileId));
+        }
+      }
+    }
+
+    // Grant access only to files that are attached to this agent
+    fileIds.forEach((fileId) => {
+      if (attachedFileIds.has(fileId)) {
+        accessMap.set(fileId, true);
+      }
+    });
+
+    return accessMap;
+  } catch (error) {
+    logger.error('[hasAccessToFilesViaAgent] Error checking file access:', error);
+    return accessMap;
+  }
+};
+
+/**
+ * Filter files based on user access through agents
+ * @param {Array<MongoFile>} files - Array of file documents
+ * @param {string} userId - User ID for access control
+ * @param {string} agentId - Agent ID that might grant access to files
+ * @returns {Promise<Array<MongoFile>>} Filtered array of accessible files
+ */
+const filterFilesByAgentAccess = async (files, userId, agentId) => {
+  if (!userId || !agentId || !files || files.length === 0) {
+    return files;
+  }
+
+  // Separate owned files from files that need access check
+  const filesToCheck = [];
+  const ownedFiles = [];
+
+  for (const file of files) {
+    if (file.user && file.user.toString() === userId) {
+      ownedFiles.push(file);
+    } else {
+      filesToCheck.push(file);
+    }
+  }
+
+  if (filesToCheck.length === 0) {
+    return ownedFiles;
+  }
+
+  // Batch check access for all non-owned files
+  const fileIds = filesToCheck.map((f) => f.file_id);
+  const accessMap = await hasAccessToFilesViaAgent(userId, fileIds, agentId);
+
+  // Filter files based on access
+  const accessibleFiles = filesToCheck.filter((file) => accessMap.get(file.file_id));
+
+  return [...ownedFiles, ...accessibleFiles];
+};
+
+module.exports = {
+  hasAccessToFilesViaAgent,
+  filterFilesByAgentAccess,
+};