Linux Stack Protection By Default

Modern gcc compiler (v9.2.0) protects the stack by default and you will notice it because instead of SIGSEGV on stack overflow you will get a SIGABRT, but it also generates coredumps.

In this case the compiler adds the variable local_10. This variable helds a canary value that is checked at the end of the function.
The memset overflows the four bytes stack variable and modifies the canary value.

The 64bits canary 0x5429851ebaf95800 can't be predicted, but in specific situations is not re-generated and can be bruteforced or in other situations can be leaked from memory for example using a format string vulnerability or an arbitrary read wihout overflowing the stack.

If the canary doesn't match, the libc function __stack_chck_fail is called and terminates the prorgam with a SIGABORT which generates a coredump, in the case of archlinux managed by systemd and are stored on "/var/lib/systemd/coredump/"


❯❯❯ ./test 
*** stack smashing detected ***: terminated
fish: './test' terminated by signal SIGABRT (Abort)

❯❯❯ sudo lz4 -d core.test.1000.c611b7caa58a4fa3bcf403e6eac95bb0.1121.1574354610000000.lz4
[sudo] password for xxxx: 
Decoding file core.test.1000.c611b7caa58a4fa3bcf403e6eac95bb0.1121.1574354610000000 
core.test.1000.c611b : decoded 249856 bytes 

 ❯❯❯ sudo gdb /home/xxxx/test core.test.1000.c611b7caa58a4fa3bcf403e6eac95bb0.1121.1574354610000000 -q 

We specify the binary and the core file as a gdb parameters. We can see only one LWP (light weight process) or linux thread, so in this case is quicker to check. First of all lets see the back trace, because in this case the execution don't terminate in the segfaulted return.

We can see on frame 5 the address were it would had returned to main if it wouldn't aborted.

Happy Idea: we can use this stack canary aborts to detect stack overflows. In Debian with prevous versions it will be exploitable depending on the compilation flags used.
And note that the canary is located as the last variable in the stack so the previous variables can be overwritten without problems.




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Files Download Information

After 7 years of Contagio existence, Google Safe Browsing services notified Mediafire (hoster of Contagio and Contagiominidump files) that "harmful" content is hosted on my Mediafire account.

It is harmful only if you harm your own pc and but not suitable for distribution or infecting unsuspecting users but I have not been able to resolve this with Google and Mediafire.

Mediafire suspended public access to Contagio account.

The file hosting will be moved.

If you need any files now, email me the posted Mediafire links (address in profile) and I will pull out the files and share via other methods.

P.S. I have not been able to resolve "yet" because it just happened today, not because they refuse to help.  I don't want to affect Mediafire safety reputation and most likely will have to move out this time.

The main challenge is not to find hosting, it is not difficult and I can pay for it, but the effort move all files and fix the existing links on the Blogpost, and there are many. I planned to move out long time ago but did not have time for it. If anyone can suggest how to change all Blogspot links in bulk, I will be happy.


P.P.S. Feb. 24 - The files will be moved to a Dropbox Business account and shared from there (Dropbox team confirmed they can host it )  

The transition will take some time, so email me links to what you need. 

Thank you all
M

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How To Start | How To Become An Ethical Hacker

Are you tired of reading endless news stories about ethical hacking and not really knowing what that means? Let's change that!

This Post is for the people that:

• Have No Experience With Cybersecurity (Ethical Hacking)
• Have Limited Experience.
• Those That Just Can't Get A Break

OK, let's dive into the post and suggest some ways that you can get ahead in Cybersecurity.

I receive many messages on how to become a hacker. "I'm a beginner in hacking, how should I start?" or "I want to be able to hack my friend's Facebook account" are some of the more frequent queries. Hacking is a skill. And you must remember that if you want to learn hacking solely for the fun of hacking into your friend's Facebook account or email, things will not work out for you. You should decide to learn hacking because of your fascination for technology and your desire to be an expert in computer systems. Its time to change the color of your hat 😀

 I've had my good share of Hats. Black, white or sometimes a blackish shade of grey. The darker it gets, the more fun you have.

If you have no experience don't worry. We ALL had to start somewhere, and we ALL needed help to get where we are today. No one is an island and no one is born with all the necessary skills. Period.OK, so you have zero experience and limited skills…my advice in this instance is that you teach yourself some absolute fundamentals.

Let's get this party started.

•  What is hacking?

Hacking is identifying weakness and vulnerabilities of some system and gaining access with it.

Hacker gets unauthorized access by targeting system while ethical hacker have an official permission in a lawful and legitimate manner to assess the security posture of a target system(s)

 There's some types of hackers, a bit of "terminology".
White hat — ethical hacker.
Black hat — classical hacker, get unauthorized access.
Grey hat — person who gets unauthorized access but reveals the weaknesses to the company.
Script kiddie — person with no technical skills just used pre-made tools.
Hacktivist — person who hacks for some idea and leaves some messages. For example strike against copyright.

•  Skills required to become ethical hacker.

1. Curosity anf exploration
2. Operating System
3. Fundamentals of Networking

*Note this sites

• hackquest.de
• hacktissite.org
• www.trythis0ne.com
• www.hackchallenge.net
• hacking-lab.com

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CEH: Gathering Host And Network Information | Scanning

Scanning

It is important that the information-gathering stage be as complete as possible to identify the best location and targets to scan. After the completion of  footprinting and information gathering methodologies, scanning is performed.
During scanning, the hacker has vision to get information about network an hosts which are connected to that network that can help hackers to determine which type of exploit to use in hacking a system precisely. Information such as an IP addresses, operating system, services, and installed applications.

Scanning is the methodology used to detect the system that are alive and respond on the network or not. Ethical hackers use these type of scanning to identify the IP address of target system. Scanning is also used to determine the availability of the system whether it is connected to the network or not.

Types Of Scanning 

Network Scanning	Identifies IP addresses on a given network or subnet
Port Scanning	Determines open, close, filtered and unfiltered ports and services
Vulnerability Scanner	Detect the vulnerability on the target system

Port Scanning ​

Port scanning is the process of identifying open and available TCP/IP ports on a system. Port-scanning tools enable a hacker to learn about the services available on a given system. Each service or application on a machine is associated with a well-known port number. Port Numbers are divided into three ranges:

• Well-Known Ports: 0-1023
• Registered Ports: 1024-49151
• Dynamic Ports: 49152-6553

Network Scanning

Network scanning is performed for the detection of active hosts on a network either you wanna attack them or as a network administrator. Network-scanning tools attempt to identify all the live or responding hosts on the network and their corresponding IP addresses. Hosts are identified by their individual IP addresses.

Vulnerability Scanning

This methodology is used to detect vulnerabilities of computer systems on a network. A vulnerability scanner typically identifies the operating system and version number, including applications that are installed. After that the scanner will try to detect vulnerabilities and weakness in the operating system. During the later attack phase, a hacker can exploit those weaknesses in order to gain access to the system. Moreover, the vulnerability scanner can be detected as well, because the scanner must interact over the network with target machine.

The CEH Scanning Methodology

As a CEH, you should understand the methodology about scanning presented in the figure below. Because this is the actual need of hackers to perform further attacks after the information about network and hosts which are connected to the network. It detects the vulnerabilities in the system bu which hackers can be accessible to that system by exploitation of that vulnerabilities.

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