Jotter

Gregg Scott

Why vlang? V is a featured, productive, safe and confortable language highly compatible with c, that generates neat binaries with c-speed, the decompilation also seems quite clear as c code.
https://vlang.io/

After open the binary with radare in debug mode "-d" we proceed to do the binary recursive analysis with "aaaa" the more a's the more deep analys.

The function names are modified when the binary is crafted, if we have a function named hello in a module named main we will have the symbol main__hello, but we can locate them quicly thanks to radare's grep done with "~" token in this case applied to the "afl" command which lists all the symbols.

Being in debug mode we can use "d*" commands, for example "db" for breakpointing the function and then "dc" to start or continue execution.

Let's dissasemble the function with "pD" command, it also displays the function variables and arguments as well, note also the xref "call xref from main"

Let's take a look to the function arguments, radare detect's this three 64bits registers used on the function.

Actually the function parameter is rsi that contains a testing html to test the href extraction algorithm.

The string structure is quite simple and it's plenty of implemented methods.

With F8 we can step over the code as we were in ollydbg on linux.

Note the rip marker sliding into the code.

We can recognize the aray creations, and the s.index_after() function used to find substrings since a specific position.

If we take a look de dissasembly we sill see quite a few calls to tos3() functions.
Those functions are involved in string initialization, and implements safety checks.

tos(string, len)
tos2(byteptr)
tos3(charptr)

In this case I have a crash in my V code and I want to know what is crashing, just continue the execution with "dc" and see what poits the rip register.

In visual mode "V" we can see previous instructions to figure out the arguments and state.

We've located the crash on the substring operation which is something like "s2 := s1[a..b]" probably one of the arguments of the substring is out of bounds but luckily the V language has safety checks and is a controlled termination:

Switching the basic block view "space" we can see the execution flow, in this case we know the loops and branches because we have the code but this view also we can see the tos3 parameter "href=" which is useful to locate the position on the code.

When it reach the substr, we can see the parameters with "tab" command.

Looking the implementation the radare parameter calculation is quite exact.

Let's check the param values:

so the indexes are from 0x0e to 0x24 which are inside the buffer, lets continue to next iteration,
if we set a breakpoint and check every iteration, on latest iteration before the crash we have the values 0x2c to 0x70 with overflows the buffer and produces a controlled termination of the v compiled process.

Requirements:

A computer/laptop with WiFi capable of monitoring (monitor mode).
A Linux OS (I'm using Arch Linux with BlackArch Repos)
And the most obvious thing wifijammer (If you're having BlackArch then you already have it).

How does it work? You maybe thinking!, it's quite simple it sends the deauth packets from the client to the AP (Access Point) after spoofing its (client's) mac-address which makes AP think that it's the connected client who wants to disconnect and Voila!

Well to jam all WiFi networks in your range its quite easy just type:

sudo wifijammer

but wait a minute this may not be a good idea. You may jam all the networks around you, is it really what you want to do? I don't think so and I guess it's illegal.

We just want to play a prank on our friend isn't it? So we want to attack just his/her AP. To do that just type:

sudo wifijammer -a <<AP-MAC-ADDRESS>>

here -a flag specifies that we want to jam a particular AP and after it we must provide the MAC-ADDRESS of that particular AP that we want to jam.

Now how in the world am I going to know what is the MAC-ADDRESS of my friend's AP without disturbing the other people around me?

It's easy just use the Hackers all time favorite tool airodump-ng. Type in the following commands:

sudo airmon-ng

sudo airodump-ng

airmon-ng will put your device in monitor mode and airodump-ng will list all the wifi networks around you with their BSSID, MAC-ADDRESS, and CHANNELS. Now look for your friend's BSSID and grab his/her MAC-ADDRESS and plug that in the above mentioned command. Wooohooo! now you are jamming just your friend's wifi network.

Maybe that's not what you want, maybe you want to jam all the people on a particular channel well wifijammer can help you even with that just type:

sudo wifijammer -c <<CHANNEL-NUMBER>>

with -c we specify to wifijammer that we only want to deauth clients on a specified channel. Again you can see with airodump-ng who is on which channel.

wifijammer has got many other flags you can check out all flags using this command that you always knew:

sudo wifijammer -h

Hope you enjoyed it, good bye and have fun :)

More info

Gregg Scott

In general decompilers are not friendly with c++ let's analyse a simple program to get familiar with it.
Let's implement a simple code that loads a file into a vector and then save the vector with following functions:

err
load
save
main

Lets identify the typical way in C++ to print to stdout with the operator "<<"

The basic_ostream is initialized writing the word "error" to the cout, and then the operator<< again to add the endl.

The Main function simply calls "vec = load(filename)" but the compiler modified it and passed the vector pointer as a parámeter. Then it bulds and prints "loaded " << size << " users".
And finally saves the vector to /tmp/pwd and print "saved".
Most of the mess is basically the operator "<<" to concat and print values.
Also note that the vectors and strings are automatically deallocated when exit the function.

And here is the code:

Let's take a look to the load function, which iterates the ifs.getline() and push to the vector.
First of all there is a mess on the function definition, __return_storage_ptr is the vector.
the ifstream object ifs is initialized as a basic_ifstream and then operator! checks if it wasn't possible to open the file and in that case calls err()
We see the memset and a loop, getline read a cstr like line from the file, and then is converted to a string before pushing it to the vector. lVar1 is the stack canary value.

In this situations dont obfuscate with the vector pointer vec initialization at the begining, in this case the logic is quite clear.

The function save is a bit more tricky, but it's no more than a vector iteration and ofs writing.
Looping a simple "for (auto s : *vec)" in the decompiler is quite dense, but we can see clearly two write, the second write DAT_0010400b is a "\n"

As we see, save implememtation is quite straightforward.

Jotter

Sunday, January 28, 2024

Vlang Binary Debugging

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Hackerhubb.blogspot.com

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Saturday, January 27, 2024

WiFiJammer: Amazing Wi-Fi Tool

Requirements:

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Reversing Some C++ Io Operations

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