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Gaining Access
Nmap scan:
There's a redis server running on the machine, and also WinRM for whatever reason. SMB Shares might be accessible on this server.
SMB Shares
Using smbmap, there is one share that is readable even without credentials.
The Software_Updates one is new. We can connect to it and see what are the files present.
The PDF contained some useful information:
We can place an update within this share's client folders, and then a user would run it. This is probably the way to gain a reverse shell.
Electron
When checking the web portal, we see that it's a regular corporate website.
There was a download button on the page, presumably to download the program used for this application. This would make us download a .exe file.
We can actually open .exe files to find out what is within it.
When viewing the plugins directory, we would find an app.7z file which we can open to reveal the resources.
We can take a look at the resources file to view the source code and stuff, and there we find more hints that this is a Electron application.
We can dive further into the .asar file using asar.
Within the main.js file, we can find that electron-updater was imported within this application.
Signature Bypass
Searching for exploits for electron-updater led me to this website:
In short, it's possible to bypass the signature checks that determine if an electron update is legitimate or not. This is done through altering the latest.yaml file. So, by bypassing this signature check, the updater would execute any malicious code we use.
This is in line with the information on the PDF we found earlier, telling us to place updates within the share for it to be executed. We can follow the PoC provided.
First, we can generate a quick reverse shell binary with msfvenom.
Afterwards, we need to change the name of this binary to have an ' character within it. I named mine v'rev.exe. Then, we need to take the sha512 hash of this file and base64 encode it.
Then, we can create the latest.yaml file to have a custom HTTP path for the update with the hash value. Afterwards, we can host the binary on a Python HTTP server.
Upon creation, we would need to put this YAML file within the client directory of the share we accessed earlier.
After a while, our HTTP server would get a hit and our listener port would catch a reverse shell.
Privilege Escalation
Kanban Redis Creds
Within the user's Downloads folder, we can find a PortableKanban instance.
Within the folder, we can find an encrypted password for the redis instance on the machine.
Quick googling led me to an exploit, which allows for us to decrypt the passwords using DES.
I used CyberChef to decrypt the password using the key and IV extracted from the exploit.
After finding this password, we can use redis-cli to login to the redis instance.
Redis Creds
Logging in:
We can check all the keys present on this machine:
The user key with some kind of GUID was the first I checked. We can do so with get <name>. This revealed another encrypted password for the Administrator.
We can decrypt this using the same CyberChef configurations.
Then, we can use evil-winrm to log in as the administrator.
