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TryHackMe/Common_Linux_Privesc.md
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TryHackMe/Common_Linux_Privesc.md
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# TryHackMe-Common Linux Privilege Escalation
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## NMAP
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```
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Nmap scan report for 10.10.235.8 [37/154]
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Host is up (0.20s latency).
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Not shown: 994 closed ports
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PORT STATE SERVICE VERSION
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22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
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| ssh-hostkey:
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| 2048 37:c9:2d:7e:01:c5:ea:33:a9:e2:19:ea:66:1c:95:82 (RSA)
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| 256 9f:48:65:f7:67:2e:92:cf:73:ce:0e:69:f1:32:46:40 (ECDSA)
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|_ 256 ac:5f:9a:38:23:ee:ac:14:88:9e:aa:08:df:98:f4:a7 (ED25519)
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80/tcp open http Apache httpd 2.4.29 ((Ubuntu))
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|_http-server-header: Apache/2.4.29 (Ubuntu)
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|_http-title: Apache2 Ubuntu Default Page: It works
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111/tcp open rpcbind 2-4 (RPC #100000)
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| rpcinfo:
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| program version port/proto service
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| 100000 2,3,4 111/tcp rpcbind
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| 100000 2,3,4 111/udp rpcbind
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| 100000 3,4 111/tcp6 rpcbind
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| 100000 3,4 111/udp6 rpcbind
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| 100003 3 2049/udp nfs
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| 100003 3 2049/udp6 nfs
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| 100003 3,4 2049/tcp nfs
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| 100003 3,4 2049/tcp6 nfs
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| 100005 1,2,3 39913/tcp mountd
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| 100005 1,2,3 43930/udp mountd
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| 100005 1,2,3 50462/udp6 mountd
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| 100005 1,2,3 53247/tcp6 mountd
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| 100021 1,3,4 38879/tcp nlockmgr
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| 100005 1,2,3 53247/tcp6 mountd
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| 100021 1,3,4 38879/tcp nlockmgr
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| 100021 1,3,4 40883/tcp6 nlockmgr
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| 100021 1,3,4 47812/udp nlockmgr
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| 100021 1,3,4 57217/udp6 nlockmgr
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| 100227 3 2049/tcp nfs_acl
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| 100227 3 2049/tcp6 nfs_acl
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| 100227 3 2049/udp nfs_acl
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|_ 100227 3 2049/udp6 nfs_acl
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139/tcp open netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP)
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445/tcp open netbios-ssn Samba smbd 4.7.6-Ubuntu (workgroup: WORKGROUP)
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2049/tcp open nfs_acl 3 (RPC #100227)
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Service Info: Host: LINUX; OS: Linux; CPE: cpe:/o:linux:linux_kernel
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Host script results:
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|_clock-skew: mean: 1h40m00s, deviation: 2h53m12s, median: 0s
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|_nbstat: NetBIOS name: LINUX, NetBIOS user: <unknown>, NetBIOS MAC: <unknown> (unknown)
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| smb-os-discovery:
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| OS: Windows 6.1 (Samba 4.7.6-Ubuntu)
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| Computer name: polobox
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| NetBIOS computer name: LINUX\x00
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| Domain name: \x00
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| FQDN: polobox
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|_ System time: 2020-11-21T10:27:08-05:00
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| smb-security-mode:
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| account_used: guest
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| authentication_level: user
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| challenge_response: supported
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|_ message_signing: disabled (dangerous, but default)
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| smb2-security-mode:
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| 2.02:
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|_ Message signing enabled but not required
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| smb2-time:
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| date: 2020-11-21T15:27:08
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|_ start_date: N/A
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Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
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Nmap done: 1 IP address (1 host up) scanned in 25.45 seconds
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```
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## Enumeration
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1. First, lets SSH into the target machine, using the credentials user3:password. This is to simulate getting a foothold on the system as a normal privilege user.
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`No answer needed`
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2. What is the target's hostname?
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`polobox`
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<img src="https://imgur.com/cIQZlOM.png"/>
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By reading the contents of `/etc/passwd` there are 8 users
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3. Look at the output of /etc/passwd how many "user[x]" are there on the system?
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`8`
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<img src="https://imgur.com/ps8gddG.png"/>
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4. How many available shells are there on the system?
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`4`
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<img src="https://imgur.com/1X1bWkQ.png"/>
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5. What is the name of the bash script that is set to run every 5 minutes by cron?
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`autoscript.sh`
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6. What critical file has had its permissions changed to allow some users to write to it?
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`/etc/passwd`
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## Abusing SUID/GUID Files
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<img src="https://imgur.com/b4T3log.png"/>
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1. What is the path of the file in user3's directory that stands out to you?
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`/home/user3/shell`
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## Exploiting a writable /etc/passwd
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1. Having read the information above, what direction privilege escalation is this attack?
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`Vertical`
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Now to generate a simple password hash , `openssl` can do that however it is not only used for generating md5 hash it's a cryptography toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer ,Security (TLS v1) network protocols and related cryptography standards required by them.
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`openssl passwd -1 --salt abc 123` so let's breakdown this command
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```
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openssl , is the tool that we are using
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passwd , is telling to generate a passwd
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-1 ,it's telling to use md5 hashing algorithm
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--salt ,telling to use the salt which is a random value but in this case we are using new and 123 is the actual password on which this alogrithm will be applied
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```
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<img src="https://imgur.com/o0VewRd.png"/>
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2. What is the hash created by using this command with the salt, "new" and the password "123"?
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`$1$new$p7ptkEKU1HnaHpRtzNizS1`
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<img src="https://imgur.com/R8QFh9Y.png"/>
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3. What would the /etc/passwd entry look like for a root user with the username "new" and the password hash we created before?
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`new:$1$new$p7ptkEKU1HnaHpRtzNizS1:0:0:root:/root:/bin/bash`
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## Escaping Vi Editor
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Use "su" to swap to user8, with the password "password"
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<img src="https://imgur.com/EBlBf5b.png"/>
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Run it with `sudo /usr/bin/vi`
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<img src="https://imgur.com/UkunmAC.png"/>
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<img src="https://imgur.com/UySCvQ2.png"/>
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1. `sudo -l` command, what does this user require (or not require) to run vi as root?
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`NOPASSWD`
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## Exploiting Crontab
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We can see a cronjob running as `root` user
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<img src="https://imgur.com/C6lsigg.png"/>
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So now we have to create a payload and append it to the cron script
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<img src="https://imgur.com/GOE3YSW.png"/>
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<img src="https://imgur.com/Ld6hwUh.png"/>
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<img src="https://imgur.com/1XcVEuU.png"/>
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1. What directory is the "autoscript.sh" under?
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`/home/user4/Desktop`
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## Exploiting PATH Variable
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<img src="https://imgur.com/m0y30wa.png"/>
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1. Let's go to user5's home directory, and run the file "script". What command do we think that it's executing?
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`ls`
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<img src="https://imgur.com/JdKqiXI.png"/>
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2. What would the command look like to open a bash shell, writing to a file with the name of the executable we're imitating
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`echo "/bin/bash" `
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3. Great! Now we've made our imitation, we need to make it an executable. What command do we execute to do this?
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`chmod +x ls`
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Now we must edit the $PATH variable to do this we must include the path for our `ls` binary
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`export PATH=/tmp:$PATH` , when we run it in bash it would just invoke a bash
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<img src="https://imgur.com/aJ8smTM.png"/>
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<img src="https://imgur.com/tDyqlo0.png"/>
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Now we are root !
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To revert back and use `ls` command we can just edit the enviromental variable `$PATH` and remove the `/tmp` from it
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<img src="https://imgur.com/I4iUuce.png"/>
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