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Golang binaries are a bit hard to analyze but there are some tricks to locate the things and view what is doing the code.

Is possible to list all the go files compiled in the binary even in an striped binaries, in this case we have only one file gohello.go this is a good clue to guess what is doing the program.

On stripped binaries the runtime functions are not resolved so is more difficult to locate the user algorithms:

If we start from the entry point, we will found this mess:

The golang string initialization are encoded and is not displayed on the strings window.

How to locate main? if its not stripped just bp on [package name].main for example bp main.main, (you can locate the package-name searching strings with ".main")

And here is our main.main:

The code is:

So in a stripped binary we cant find the string "hello world" neither the initialization 0x1337 nor the comparator 0x1337, all this is obfuscated.

The initialization sequence is:

The procedure for locating main.main in stripped binaries is:

1. Click on the entry point and locate the runtime.mainPC pointer:

2. click on runtime.main function (LAB_0042B030):

3. locate the main.main call after the zero ifs:

4. click on it and here is the main:

The runtime is not obvious for example the fmt.Scanf() call perform several internal calls until reach the syscall, and in a stripped binary there are no function names.

In order to identify the functions one option is compile another binary with symbols and make function fingerprinting.

In Ghidra we have the script golang_renamer.py which is very useful:

After applying this plugin the main looks like more clear:

This script is an example of function fingerprinting, in this case all the opcodes are included on the crc hashing:

# This script fingerprints the functions
#@author: sha0coder
#@category fingerprinting

print "Fingerprinting..."

import zlib


# loop through program functions
function = getFirstFunction()
while function is not None:
    name = str(function.getName())
    entry = function.getEntryPoint()
    body = function.getBody()
    addresses = body.getAddresses(True)

    if not addresses.hasNext():
        # empty function
        continue 

    ins = getInstructionAt(body.getMinAddress())
    opcodes = ''
    while ins and ins.getMinAddress() <= body.getMaxAddress():
        for b in ins.bytes:
            opcodes += chr(b & 0xff)
        ins = getInstructionAfter(ins)
    
    
    crchash = zlib.crc32(opcodes) & 0xffffffff

    print name, hex(crchash)


    function = getFunctionAfter(function)

Boasting of information harvesting and backdoor capabilities, the .NET-based malware has been linked to at least three different attack waves in 2021. The first set, reported in April, took advantage of search engine poisoning techniques to trick business professionals into visiting sketchy Google sites that installed SolarMarker on the victim's machines.

Then in August, the malware was observed targeting healthcare and education sectors with the goal of gathering credentials and sensitive information. Subsequent infection chains documented by Morphisec in September 2021 highlighted the use of MSI installers to ensure the delivery of the malware.

The SolarMarker modus operandi commences with redirecting victims to decoy sites that drop the MSI installer payloads, which, while executing seemingly legitimate install programs such as Adobe Acrobat Pro DC, Wondershare PDFelement, or Nitro Pro, also launches a PowerShell script to deploy the malware.

"These SEO efforts, which leveraged a combination of Google Groups discussions and deceptive web pages and PDF documents hosted on compromised (usually WordPress) websites, were so effective that the SolarMarker lures were usually at or near the top of search results for phrases the SolarMarker actors targeted," Sophos researchers Gabor Szappanos and Sean Gallagher said in a report shared with The Hacker News.

The PowerShell installer is designed to alter the Windows Registry and drop a .LNK file into Windows' startup directory to establish persistence. This unauthorized change results in the malware getting loaded from an encrypted payload hidden amongst what the researchers called a "smokescreen" of 100 to 300 junk files created specifically for this purpose.

"Normally, one would expect this linked file to be an executable or script file," the researchers detailed. "But for these SolarMarker campaigns the linked file is one of the random junk files, and cannot be executed itself."

What's more, the unique and random file extension used for the linked junk file is utilized to create a custom file type key, which is ultimately employed to execute the malware during system startup by running a PowerShell command from the Registry.

The backdoor, for its part, is ever-evolving, featuring an array of functionalities that allow it to steal information from web browsers, facilitate cryptocurrency theft, and execute arbitrary commands and binaries, the results of which are exfiltrated back to a remote server.

"Another important takeaway […], which was also seen in the ProxyLogon vulnerabilities targeting Exchange servers, is that defenders should always check whether attackers have left something behind in the network that they can return to later," Gallagher said. "For ProxyLogon this was web shells, for SolarMarker this is a stealthy and persistent backdoor that according to Sophos telematics is still active months after the campaign ended."

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sábado, 3 de junio de 2023

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