In this series, we will be assuming step-by-step examples of accepted attacks. We will alpha off with a basal SQL bang corruption of a web appliance and again advantage accretion to O.S root.
SQL Bang is one of the best alarming vulnerabilities a web appliance can be decumbent to. When a user’s ascribe is actuality anesthetized unvalidated and unsanitized as allotment of a SQL concern that agency that the user can dispense the concern itself and force it to acknowledgment altered abstracts than what it was declared to return. In this article, we will see how and why this is so dangerous.
Before accepting our easily on the exploitation, let’s aboriginal bound see what SQLi is. Let’s accept that we accept a web appliance which takes the constant “article” via $_GET appeal and queries the database to get an article’s content.
The basal PHP cipher is the following:
A archetypal folio in this web appliance would be the following:
If a user changes the commodity constant to 1 AND 1=1 again the concern will attending like this:
In this case, the agreeable of the folio does not change because the two altitude in the SQL annual are both true. There is an commodity with an id of 1, and 1 is set according to 1, which is true.
If a user changes the constant to 1 AND 1=2, it allotment annihilation because 1 is not according to 2.
That agency that the user is authoritative the concern and can acclimatize it appropriately to dispense the results. More abundant advice on SQL Injection can be begin here.
Let’s see, step-by-step, how alarming the corruption of a SQL Bang can be. Just for reference, the afterward book is done on a Linux apparatus active Ubuntu 16.04.1 LTS, PHP 7.0, MySQL 5.7, and WordPress 4.9.
For the purposes of this demonstration, we accept performed a aegis analysis on a sample web application. During our pentest, we accept articular a plugin endpoint which appears to be accepting, via a $_GET request, the ID of a user, and is announcement their username.
The endpoint is anon attainable which could announce “loose” security. The aboriginal affair addition would do is to dispense the admission point (user ascribe – $_GET parameter) and beam the response. What we are attractive for is to see if our ascribe changes, in any way, the achievement of the application. Ideally, we appetite to see a SQL absurdity which could announce that our ascribe is parsed as allotment of a query. There are abounding agency to analyze whether an appliance is accessible to SQL injection. One of the best accepted and simple ones is the use of a distinct adduce which beneath assertive affairs “breaks” the query:
The MySQL absurdity we get confirms that the appliance is absolutely vulnerable:
At this point, it is about assertive that we will anon be able to abjure abstracts from the web application’s backend database. If our ascribe is actuality parsed as allotment of the concern that agency that we can ascendancy it. If we can ascendancy the query, again we can ascendancy the results.
We accept articular the SQL bang vulnerability, now let’s advance with the attack. We appetite to get admission to the administering breadth of the website. Let’s accept that we don’t apperceive the anatomy of the database or the admin has acclimated non-default naming/prefix during the accession of WordPress. We charge to acquisition the tables’ names to be able to grab the admin’s countersign later.
To do that we aboriginal charge to acquisition how abounding columns the accepted table has. We will use cavalcade acclimation to accomplish that. ” ORDER BY ” is acclimated to set the order(sort) of the results. Acclimation can be done either by cavalcade name or by cavalcade number. If the ORDER BY cardinal we canyon in the constant is beneath than the absolute cardinal of columns in the accepted table again the achievement of the appliance should not change as the SQL concern is valid. If, however, the cardinal we ascribe is beyond than the absolute cardinal of the columns again we will get an absurdity as there won’t be such cavalcade numbers to adjustment the after-effects by. In our case, we accept articular 10 columns:
If we use a college number, we don’t get any results:
Depending on the setup, we adeptness get an error:
Now that we apperceive how abounding columns the accepted table has, we will use UNION to see which cavalcade is “vulnerable.” UNION is acclimated to amalgamate after-effects from assorted SELECT statements into a distinct result. “Vulnerable” is the cavalcade whose abstracts is actuality displayed on the page.
As we can see, the cardinal “10” is actuality displayed on the folio which agency it’s “vulnerable”:
We can affirm this by replacing it with version() which will appearance the MySQL version:
Next, we charge to acquisition the table names which we will again use to abjure data:
group_concat() action concatenates after-effects into a string. Information_schema is a database which food advice about added databases. database() allotment the name of the accepted database.
Now that we accept the table structure, we can concern the database to get the admin’s accreditation from the table wp_users.
Bingo. We accept the admin’s countersign hash; however, we cannot currently use it. In adjustment to acquisition the plaintext countersign of this hash, we will use a acclaimed countersign accretion software called hashcat to able it. There are assorted methods of arise a password; we will try the “Dictionary” advance with a almost baby annual absolute 96 actor passwords.
After downloading hashcat as able-bodied as the countersign list, we run the afterward command:
We’ve been advantageous and were able to balance the countersign aural a few minutes. The recovered countersign is 10987654321:
Unless any array of two-factor affidavit is in place, the admin’s countersign should be acceptable to admission the website’s backend. Once we do that, the options are limitless.
It is important to agenda that at the accepted date we accept abounding admin admission to the website’s backend which agency we can admission any page/post either clandestine or not and consign all the data, including the users, and appealing abundant do annihilation we want. Let’s see how far we can get.
There are third-party WordPress plugins which could acquiesce us to assassinate carapace commands or upload new files, however, we will abstain that. What we are action to do is use Weavely, a accepted failing PHP backdoor to added amplify this attack.
After downloading and unpacking the software, we will aboriginal actualize an abettor which will be injected into the WordPress armpit and which will accord us the adeptness to assassinate arrangement commands beneath the low-privileged webserver annual (www-data).
The afterward command will actualize a book which charge be uploaded to the ambition system.
Instead of uploading the file, we will use WordPress’s absolute arrangement files to inject the capacity of agent.php. We cross to the Appearance editor (which is by absence enabled) and inject the cipher of agent.php into the header.php book :
Now the backdoor abettor is in abode and what we charge to do is admit a affiliation to it from our bounded computer. Back we accept injected the abettor into the theme’s header, we can specify any WordPress folio as a target, back the advance is included in all the arrangement files.
As we can see below, we accept auspiciously accomplished a affiliation to our backdoor agent. Active the id command allotment the accepted user which is www-data. We additionally see that the hostname is “windoze” and the accepted alive agenda is “/var/www/html/wordpress “:
On the victim’s side, this is what the requests beatific to the backdoor looks like in the log:
On our bounded apparatus we additionally alpha a Netcat adviser so that we can actualize a about-face carapace affiliation from the ambition to our computer:
We now accelerate the afterward command to our backdoor abettor to admit a about-face carapace connection:
The Netcat adviser shows that a affiliation has been established:
We now accept a low advantaged carapace on the ambition machine. What we appetite is to amplify our privileges and get basis access. The uname -a command allotment abundant advice for us to advance with the attack. We are absorbed in the atom version.
We accept begin a advantage accretion accomplishment which works on this Atom adaptation (126.96.36.199). We download and abridge on our bounded machine.
Now, appliance our about-face carapace connection, we will download the accomplishment on the ambition machine.
We admission the assassinate permission on the accomplishment by active “chmod x chocobo_root” and again we run it :
After a few moments, the advantage accretion is successful, and we can see that we are active beneath the basis account:
At this point, we accept abounding basis admission to the ambition apparatus which agency that the aegis triangle of Confidentiality, Integrity, and Availability has been absolutely compromised. This can be disastrous for an alignment as an antagonist can:
It is important to agenda that the apparatus was active on a absence bureaucracy after any changes which would acquiesce us to accomplish the advance easier.
A annual of factors played a analytical role in the acknowledged corruption of this attack:
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