mirror of
https://github.com/swisskyrepo/PayloadsAllTheThings.git
synced 2024-11-14 00:47:20 +00:00
145 lines
No EOL
7.2 KiB
Markdown
145 lines
No EOL
7.2 KiB
Markdown
# Web Cache Deception
|
|
|
|
> Web Cache Deception (WCD) is a security vulnerability that occurs when a web server or caching proxy misinterprets a client's request for a web resource and subsequently serves a different resource, which may often be more sensitive or private, after caching it.
|
|
|
|
|
|
## Summary
|
|
|
|
* [Tools](#tools)
|
|
* [Methodology](#methodology)
|
|
* [Caching Sensitive Data](#caching-sensitive-data)
|
|
* [Caching Custom JavaScript](#caching-custom-javascript)
|
|
* [CloudFlare Caching](#cloudflare-caching)
|
|
* [Labs](#labs)
|
|
* [References](#references)
|
|
|
|
|
|
## Tools
|
|
|
|
* [PortSwigger/param-miner](https://github.com/PortSwigger/param-miner) - Web Cache Poisoning Burp Extension
|
|
|
|
|
|
## Methodology
|
|
|
|
Example of Web Cache Deception:
|
|
|
|
Imagine an attacker lures a logged-in victim into accessing `http://www.example.com/home.php/non-existent.css`
|
|
|
|
1. The victim's browser requests the resource `http://www.example.com/home.php/non-existent.css`
|
|
2. The requested resource is searched for in the cache server, but it's not found (resource not in cache).
|
|
3. The request is then forwarded to the main server.
|
|
4. The main server returns the content of `http://www.example.com/home.php`, most probably with HTTP caching headers that instruct not to cache this page.
|
|
5. The response passes through the cache server.
|
|
6. The cache server identifies that the file has a CSS extension.
|
|
7. Under the cache directory, the cache server creates a directory named home.php and caches the imposter "CSS" file (non-existent.css) inside it.
|
|
8. When the attacker requests `http://www.example.com/home.php/non-existent.css`, the request is sent to the cache server, and the cache server returns the cached file with the victim's sensitive `home.php` data.
|
|
|
|
|
|
|
|
### Caching Sensitive Data
|
|
|
|
**Example 1** - Web Cache Deception on PayPal Home Page
|
|
|
|
1. Normal browsing, visit home : `https://www.example.com/myaccount/home/`
|
|
2. Open the malicious link : `https://www.example.com/myaccount/home/malicious.css`
|
|
3. The page is displayed as /home and the cache is saving the page
|
|
4. Open a private tab with the previous URL : `https://www.example.com/myaccount/home/malicious.css`
|
|
5. The content of the cache is displayed
|
|
|
|
Video of the attack by Omer Gil - Web Cache Deception Attack in PayPal Home Page
|
|
[](https://vimeo.com/249130093)
|
|
|
|
**Example 2** - Web Cache Deception on OpenAI
|
|
|
|
1. Attacker crafts a dedicated .css path of the `/api/auth/session` endpoint.
|
|
2. Attacker distributes the link
|
|
3. Victims visit the legitimate link.
|
|
4. Response is cached.
|
|
5. Attacker harvests JWT Credentials.
|
|
|
|
|
|
### Caching Custom JavaScript
|
|
|
|
1. Find an un-keyed input for a Cache Poisoning
|
|
```js
|
|
Values: User-Agent
|
|
Values: Cookie
|
|
Header: X-Forwarded-Host
|
|
Header: X-Host
|
|
Header: X-Forwarded-Server
|
|
Header: X-Forwarded-Scheme (header; also in combination with X-Forwarded-Host)
|
|
Header: X-Original-URL (Symfony)
|
|
Header: X-Rewrite-URL (Symfony)
|
|
```
|
|
2. Cache poisoning attack - Example for `X-Forwarded-Host` un-keyed input (remember to use a buster to only cache this webpage instead of the main page of the website)
|
|
```js
|
|
GET /test?buster=123 HTTP/1.1
|
|
Host: target.com
|
|
X-Forwarded-Host: test"><script>alert(1)</script>
|
|
|
|
HTTP/1.1 200 OK
|
|
Cache-Control: public, no-cache
|
|
[..]
|
|
<meta property="og:image" content="https://test"><script>alert(1)</script>">
|
|
```
|
|
|
|
|
|
## Tricks
|
|
|
|
The following URL format are a good starting point to check for "cache" feature.
|
|
|
|
* https://example.com/app/conversation/.js?test
|
|
* https://example.com/app/conversation/;.js
|
|
* https://example.com/home.php/non-existent.css
|
|
|
|
|
|
## CloudFlare Caching
|
|
|
|
CloudFlare caches the resource when the `Cache-Control` header is set to `public` and `max-age` is greater than 0.
|
|
|
|
- The Cloudflare CDN does not cache HTML by default
|
|
- Cloudflare only caches based on file extension and not by MIME type: [cloudflare/default-cache-behavior](https://developers.cloudflare.com/cache/about/default-cache-behavior/)
|
|
|
|
|
|
In Cloudflare CDN, one can implement a `Cache Deception Armor`, it is not enabled by default.
|
|
When the `Cache Deception Armor` is enabled, the rule will verify a URL's extension matches the returned `Content-Type`.
|
|
|
|
CloudFlare has a list of default extensions that gets cached behind their Load Balancers.
|
|
|
|
| | | | | | | |
|
|
|-------|------|------|------|------|-------|------|
|
|
| 7Z | CSV | GIF | MIDI | PNG | TIF | ZIP |
|
|
| AVI | DOC | GZ | MKV | PPT | TIFF | ZST |
|
|
| AVIF | DOCX | ICO | MP3 | PPTX | TTF | CSS |
|
|
| APK | DMG | ISO | MP4 | PS | WEBM | FLAC |
|
|
| BIN | EJS | JAR | OGG | RAR | WEBP | MID |
|
|
| BMP | EOT | JPG | OTF | SVG | WOFF | PLS |
|
|
| BZ2 | EPS | JPEG | PDF | SVGZ | WOFF2 | TAR |
|
|
| CLASS | EXE | JS | PICT | SWF | XLS | XLSX |
|
|
|
|
|
|
Exceptions and bypasses:
|
|
|
|
* If the returned Content-Type is application/octet-stream, the extension does not matter because that is typically a signal to instruct the browser to save the asset instead of to display it.
|
|
* Cloudflare allows .jpg to be served as image/webp or .gif as video/webm and other cases that we think are unlikely to be attacks.
|
|
* [Bypassing Cache Deception Armor using .avif extension file - fixed](https://hackerone.com/reports/1391635)
|
|
|
|
|
|
## Labs
|
|
|
|
* [PortSwigger Labs for Web Cache Deception](https://portswigger.net/web-security/all-labs#web-cache-poisoning)
|
|
|
|
|
|
## References
|
|
|
|
- [Cache Deception Armor - Cloudflare - May 20, 2023](https://developers.cloudflare.com/cache/cache-security/cache-deception-armor/)
|
|
- [Exploiting cache design flaws - PortSwigger - May 4, 2020](https://portswigger.net/web-security/web-cache-poisoning/exploiting-design-flaws)
|
|
- [Exploiting cache implementation flaws - PortSwigger - May 4, 2020](https://portswigger.net/web-security/web-cache-poisoning/exploiting-implementation-flaws)
|
|
- [How I Test For Web Cache Vulnerabilities + Tips And Tricks - bombon (0xbxmbn) - July 21, 2022](https://bxmbn.medium.com/how-i-test-for-web-cache-vulnerabilities-tips-and-tricks-9b138da08ff9)
|
|
- [OpenAI Account Takeover - Nagli (@naglinagli) - March 24, 2023](https://twitter.com/naglinagli/status/1639343866313601024)
|
|
- [Practical Web Cache Poisoning - James Kettle (@albinowax) - August 9, 2018](https://portswigger.net/blog/practical-web-cache-poisoning)
|
|
- [Shockwave Identifies Web Cache Deception and Account Takeover Vulnerability affecting OpenAI's ChatGPT - Nagli (@naglinagli) - July 15, 2024](https://www.shockwave.cloud/blog/shockwave-works-with-openai-to-fix-critical-chatgpt-vulnerability)
|
|
- [Web Cache Deception Attack - Omer Gil - February 27, 2017](http://omergil.blogspot.fr/2017/02/web-cache-deception-attack.html)
|
|
- [Web Cache Deception Attack leads to user info disclosure - Kunal Pandey (@kunal94) - February 25, 2019](https://medium.com/@kunal94/web-cache-deception-attack-leads-to-user-info-disclosure-805318f7bb29)
|
|
- [Web Cache Entanglement: Novel Pathways to Poisoning - James Kettle (@albinowax) - August 5, 2020](https://portswigger.net/research/web-cache-entanglement)
|
|
- [Web cache poisoning - PortSwigger - May 4, 2020](https://portswigger.net/web-security/web-cache-poisoning) |