CVE-2019-9787 PoC — WordPress 跨站请求伪造漏洞

Description

This is a recurrence of cve-2019-9787 on Wordpress and a hash-based defense.

介绍

# Wordpress_cve-2019-9787_defense
## Notice
This is a project by Sijia Zhang(https://github.com/sijiahi) and Bowen Zhou(https://github.com/KonjakZhou)

## **Prerequisite:

### 1 Recurrence Attack:
	- Configure and install Wordpress5.0 under http://localhost/wp-admin/;
	- Log in Wordpress as admin, post at least one article;
	- open mal.html(configured under another domain name, possibly directly open as file in browser),click submit request.
	- If this works, you would be redirected to article page with "cilick me" comment, once you move your mouse over it, a prompt window indicating success attack would appear.
### 2 Defense:
	-Replece files in /wp-includes, add js scripts in /wp-includes/js.
	-Move the mock post file in WP rigion, open the mock post page to test PINGBACK/TRACEBACK function.
	-If this worked, you will be redirected to article page with "legal anchor" comment;
	-Open mal.com from anthor domain name,test CSRF attack.
	



## **Code modified:

- comment-template:    js script   added extract, calculate and add doggyNonce script;
- functions:           PHP script  added  extract attribute script;
- pluggable:           PHP script  added verify doggyNonce script.
- comment:             PHP script  changed the request process logic.




## **This is a recurrence of cve-2019-9787 on Wordpress and a hash-based defense.

### 0 Intro:
To defend Wordpress against CVE-2019-9787, a new field called doggyNonce is introduced.
In cases where admin tries to adopt PINGBACK funxtion, and the _wp_unfiltered_html can not be provided, we asked admin to sign a signature on attributes of their uploaded Tags attributes with their cookie, this will enable us to defend CSRF attack and ensure and integrity of uploaded tag attributes.

### 1 Defense:
Wordpress automatically accept comment without correct CSRF-token as a PINFBACK and TRACEBACK request, filter that comment with a white-list filter, extract href field and reconstruct "a tag".
To defend this vulnerability, two key points are toke into account:
	1. Server cannot distinguish illegal CSRF request from legal PINGBACK/TRACEBACK request. 
	2. CSRF Attacker inject their code in href field of "a Tag", Tag attribute changed after being filtered. 
doggyNonce is a hash value depends on *cookie(wp-setting-time-$uid) and *uploaded href attrbute:
		doggyNonce=Hash(*uploaded href attrbute,*cookie)
it should be notified that doggyNonce plays the role of admin's signature on uploaded href attribute.


## **Special reminder
	1. 'mal.html' is to mock CSRF attack, and thus, is expected to be placed in a domain other than Wordpress;
	2. 'post.html' is to mock PINGBACK/TRACEBACK function, and thus, is expected to be placed in a same domain as WP;

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