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wordpress admin-ajax.php Sql Injection

Apologies for not posting anything on my blog for so long. I saw this wordpress exploit yesterday and its just awesome work by waraxe. Unlike my xmlrpc.php exploit this doesnot even need any privilidges and the exploit works fine. To me, it is yet another example of why magic_quote setting of php is not sufficient protection against SQL injections. Although, i have explained the wordpress cookie earlier as well, i am doing it once again.

If you dont wanna spend time cracking the md5, then this is what you need to do once you get the md5 hash of the admin password.

add the following 2 cookies in your browser before you visit the admin section of the website. I recommend using this firefox plugin
the name of the cookie if specific to the website and it has this pattern
wordpressuser_(unique suffix)
where (unique suffix) is md5 of the base url

Thus as pointed by waraxe for wordpress hosted at http://localhost/wordpress-2.1.3 the suffix become md5(‘http://localhost/wordpress.2.1.3′) =5a136e6377f39b00c76957953df945db
and thus the cookie will be wordpressuser_5a136e6377f39b00c76957953df945db

now add the value of this cookie which is the username for which you have obtained the hash.
add another cookie with the name wordpresspass_[same suffix as above] and the value as the md5 of the hash you obtained by the exploit and then u can login as that user.

example:
if hash obtained is 21232f297a57a5a743894a0e4a801fc3 (md5(‘admin’))
then the value will be c3284d0f94606de1fd2af172aba15bf3 (md5(’21232f297a57a5a743894a0e4a801fc3′))

the two cookies will look like this then:
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name:wordpressuser_5a136e6377f39b00c76957953df945db
value: admin

name:wordpresspass_5a136e6377f39b00c76957953df945db
value:c3284d0f94606de1fd2af172aba15bf3
—————————————————————-

Now enjoy the admin privilidges.

Ten Cents

Some information about MS-SQL server. You may find this info useful for exploiting SQL injection:

Finding Table Names
:
Donot use:- Select name from sysobjects where xtype=’U’
Use:- SELECT table_name FROM INFORMATION_SCHEMA.TABLES
[WHERE table_schema = 'db_name']
[WHERE|AND table_name LIKE 'wild']
The first query will only return the table names which belong to current databases, however, the second query will return the the table names from other databases as well to which the current user has access to.

Getting Current User
Use:-Select SYSTEM_USER
Someone pointed this out that Select user will return the owner of the current database which may differ from the current user. So, system-user is alwayas correct to use.

Brute Forcing ‘sa’ User’s Password
Use openrowset:-select null from openrowset(‘sqloledb’,”;’sa’;’[password]‘,’select 1;waitfor delay ”0:0:10” ‘)

When the password supplied is correct the query ‘select 1;waitfor delay ”0:0:10” ‘ will get executed. As i write this blog, i am just wondering if we can execute something like this:

select null from openrowset(‘sqloledb’,”;’sa’;’[password]‘,’exec master..xp_cmshell ”ping my_host”’). I will confirm this sometime later.

MySql default [insecure] installation in debian

i recently updated my MySql server and i am currently using the version.5.0.38-Debian_1-log If you ever wondered how MySql saves data on your hard disk, then this is best explained here. I will quote from the same website

“Each database is a directory, with each table stored in a separate set of files. For an individual table, the .frm file contains information about the table structure — effectively, an internal representation of the CREATE TABLE statement. The .MYD file contains the row data, and the .MYI contains any indexes belonging with this table, as well as some statistics about the table. The data file contains only row data, with minimal overhead.”

Thus if you can read these directories/files, you can get hold of the database/table names respectively.
ISSUE-1
I looked on my debian box and these files are located in /var/lib/mysql folder. This folder is owned by user mysql and belongs to group mysql. Surprisingly, by default the permissions on this folder is 755. Thus a normal user on the box can list files and directories in the folder /var/lib/mysql and get hold of all the database names,which the MySQL server stores on this host
. However, the database directories in this folder are properly locked which denies an unprivlidged user to get tables information for databases. Although, the database mysql itslef allows directory listing but the files are not word readable. Thus a normal user cant read the file /var/lib/mysql/mysql/user.MYD which represent the table mysql.user and stores mysql username and encrypted password. :(

ISSUE-2.0

If you are able to find a local privelege escalation on a box and manage to get root access, how will you get hold of the data stored in the MySql database?
You will probably try to read the file /var/lib/mysql/mysql/user.MYD to get the Mysql Username and their password hash and would then try to crack these hashes. It then comes down to the complexity of the password and if the password is complex enough there are chances that you may still not be able to crack it. However, the story is a bit different if you are on a debian box. Debian has an inbuilt account debian-sys-maint which bydefault has privilieges equivalent to what you will have for root user. To make matter worse, the file /etc/mysql/debian.cnf contains the randomly generated clear text password for this user. However, this file is again not word readable. But if you got a privilege escalation on debian box, no need to crack the hashes, just issue the command: mysql –defaults-extra-file=/etc/mysql/debian.cnf and you will have the entire MySql server to play.

Abusing Trackback utility

I was researching a bit into the wordpress trackback utility. This is how it works:
You submit a post with trackback urls, and when you publish the post, the wordpress sends out a request to the URL you mentioned in the trackback URLs. Essentially this happens in the background.

You—–> WordPress Server———->Trackback URL

The trackback request to the trackback URL is not made by your browser, but the request will be sent by your server hosting wordpress application. This was a bit surprising to me, as what if my wordpress hosting company does not allow outbound traffic? Anyways the request is nothing special , its a straight forward post request to the trackback URL with the following parameters.

title
url
blog_name
excerpt.

I wrote a simple perl script which you can use to send fake trackback request. Although the request will go from your IP address, (unless you use some anonymous proxy) You can specify the Fake Url and other parameters which will appear to the victim’s wordpress. The Only solution i can think to avoid getting fake trackbacks is by having a check on the submitted url to see if it resolves to the same ip address. However, that might create some other problems.

However, I would be more interested in knowing if we can abuse it still further. At the moment i cant think of any more attack vectors to exploit this. As the connection to the trackback URL is made by wordpress server, can we not make it connect to a malicious host. Can we not make it connect to different ports on different hosts… blah.. blah blah... I look forward to hearing comments on this. BTW this blog is not just about hacking wordpress:)

WordPress 2.1.2 xmlrpc Security Issues

WordPress 2.1.2 xmlrpc Multiple Vulnerabilities:

Affected Versions: These issues were reported in version 2.1.2,(current stable version) and its very likely that previous versions may also be vulnerable.

1. Privilidge Escalation:

Under normal circumstances (through web interface) a user in contributor role only has access to following functions:

a. read
b. edit_posts

functionality ‘publish_posts’ is restricted to users in the author, editor or administrator roles. However, this is not implemented in xmlrpc.php and this allows a user in the contributor roles to publish a previously saved post to the website.

No exploit code is required.

2. SQL Injection:

This is only exploitable by authenticated users.
The post_id parameter is not properly sanitized before passing its value to the backend database which results in a Sql injection. Exploiting this is pretty trivial. As, it is an integer based injection, it works irrespective of the setting “magic quote”. . I wrote a Simple Proof Of Concept for this.
Download Exploit
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Exploit
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Successful Exploitation of this will give you usernames and md5 hash of password of all users including admin user. Before you run mdcrack on this hash, read my previous post on wordpress cookies as this will save your time.
Once you have the admin user hash needless to say you can create a php backdoor and that essentialy is game over.

About Poc:
The poc demonstrates how critical SQL injection vulnerabilities can be. In this example,the poc goes beyond obtaining admin hashes. It also returns the username and encrypted password of the mysql user(s). If the database is running as privilidged user, this will also try to fetch the /etc/passwd file, or any other file for that matter. As this injection is in an integer field it works irrespective of the setting magic quote :-)

Workaround:
1. Disable xmlrpc if you dont use it or restrict its access to trusted users only.

Vendor’s response:
1. vendor notified on 22nd March 2007.
2. New Version released on 2nd April 2007.
3. Advisory released on 2nd April 2007

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