Understanding SMB
What is SMB?
SMB - Server Message Block Protocol - is a client-server communication protocol used for sharing access to files, printers, serial ports and other resources on a network. [source] Learn about, then enumerate and exploit a variety of network services and misconfigurations.
Servers make file systems and other resources (printers, named pipes, APIs) available to clients on the network. Client computers may have their own hard disks, but they also want access to the shared file systems and printers on the servers.
The SMB protocol is known as a response-request protocol, meaning that it transmits multiple messages between the client and server to establish a connection. Clients connect to servers using TCP/IP (actually NetBIOS over TCP/IP as specified in RFC1001 and RFC1002), NetBEUI or IPX/SPX.
How does SMB work?
Once they have established a connection, clients can then send commands (SMBs) to the server that allow them to access shares, open files, read and write files, and generally do all the sort of things that you want to do with a file system. However, in the case of SMB, these things are done over the network.
What runs SMB?
Microsoft Windows operating systems since Windows 95 have included client and server SMB protocol support. Samba, an open source server that supports the SMB protocol, was released for Unix systems.
#1 What does SMB stand for?
Ans :- Server Message Block
#2 What type of protocol is SMB?
Ans :- request-response
#3 What do clients connect to servers using?
Ans :- TCP/IP
#4 What systems does Samba run on?
Ans :- Unix
Enumerating SMB
Lets Get Started
Before we begin, make sure to deploy the room and give it some time to boot. Please be aware, this can take up to five minutes so be patient!
Enumeration
Enumeration is the process of gathering information on a target in order to find potential attack vectors and aid in exploitation.
This process is essential for an attack to be successful, as wasting time with exploits that either don't work or can crash the system can be a waste of energy. Enumeration can be used to gather usernames, passwords, network information, hostnames, application data, services, or any other information that may be valuable to an attacker.
SMB
Typically, there are SMB share drives on a server that can be connected to and used to view or transfer files. SMB can often be a great starting point for an attacker looking to discover sensitive information — you'd be surprised what is sometimes included on these shares.
Port Scanning
The first step of enumeration is to conduct a port scan, to find out as much information as you can about the services, applications, structure and operating system of the target machine. You can go as in depth as you like on this, however I suggest using nmap with the -A and -p- tags.
-A : Enables OS Detection, Version Detection, Script Scanning and Traceroute all in one
-p- : Enables scanning across all ports, not just the top 1000
Enum4Linux
Enum4linux is a tool used to enumerate SMB shares on both Windows and Linux systems. It is basically a wrapper around the tools in the Samba package and makes it easy to quickly extract information from the target pertaining to SMB. It's installed by default on Parrot and Kali, however if you need to install it, you can do so from the official github.
The syntax of Enum4Linux is nice and simple: "enum4linux [options] ip"
TAG FUNCTION
-U get userlist
-M get machine list
-N get namelist dump (different from -U and-M)
-S get sharelist
-P get password policy information
-G get group and member list
-A all of the above (full basic enumeration)
Types of SMB Exploit
While there are vulnerabilities such as CVE-2017-7494 that can allow remote code execution by exploiting SMB, you're more likely to encounter a situation where the best way into a system is due to misconfigurations in the system. In this case, we're going to be exploiting anonymous SMB share access- a common misconfiguration that can allow us to gain information that will lead to a shell.
Method Breakdown
So, from our enumeration stage, we know:
- - The SMB share location
- - The name of an interesting SMB share
SMBClient
Because we're trying to access an SMB share, we need a client to access resources on servers. We will be using SMBClient because it's part of the default samba suite. While it is available by default on Kali and Parrot, if you do need to install it, you can find the documentation here.
We can remotely access the SMB share using the syntax:
"smbclient //[IP]/[SHARE]"
Followed by the tags:
-U [name] : to specify the user
-p [port] : to specify the port
Got it? Okay, let's do this!
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