Bit

• A "bit" is atomic: the smallest unit of storage
• A bit stores just a 0 or 1
• "in the computer it's all 0's and 1's bits
• Anything with two separate states can store 1 bit
• In a chip: electric charge = 0/1
• In a hard drive: spots of North/South magnestism = 0/1
• A bit is too small to be much use
• Greoup 8 bits together to make 1 byte

NOTE :- Everything in a computer is 0's and 1's. The bit stores just a 0 or 1: It's the smallest building block of storage.

Byte

• One byte = collection of 8 bits
• eg. 0 1 0 1 0 1 0
• One byte can store one character , eg. 'A' or 'x' or '$'

How do you calculate bytes?

The calculations is based on:


In the cases when used to describe data storage bits/bytes are calculated as follows:



    1 byte = 8 bits
    1 kilobyte (K / Kb) = 2^10 bytes = 1,024 bytes
    1 megabyte (M / MB) = 2^20 bytes = 1,048,576 bytes
    1 gigabyte (G / GB) = 2^30 bytes = 1,073,741,824 bytes
    1 terabyte (T / TB) = 2^40 bytes = 1,099,511,627,776 bytes
    1 petabyte (P / PB) = 2^50 bytes = 1,125,899,906,842,624 bytes
    1 exabyte (E / EB) = 2^60 bytes = 1,152,921,504,606,846,976 bytes



The period (.) is used as decimal separator.

How many digits are in 8 bytes?

Eight bytes contain 64 bits of information, so you can store 2^64 ~ 10^20 unique items using those bits. Those items can easily be interpreted as the integers from 0 to 2^64 - 1 . So you cannot store 302 decimal digits in 8 bytes; most numbers between 0 and 10^303 - 1 cannot be so represented. How do you calculate bytes?

Disclaimer

The platform develops virtual classrooms that not only allow users to deploy training environments with the click of a button, but also reinforce learning by adding a question-answer approach. Its a comfortable experience to learn using pre-designed courses which include virtual machines (VM) hosted in the cloud.

TryHackMe Cryptography for dummies


While using a question-answer model does make learning easier, TryHackMe allows users to create their own virtual classrooms to teach particular topics enabling them to become teachers. This not only provides other users with rich and varied content, but also helps creators reinforce their understanding of fundamental concepts.



Room :- https://tryhackme.com/room/cryptographyfordummies




Cryptography is a big topic. We are going to cover the basics, to give you a basic understanding.

It is used by a wide range of applications, almost everywhere in the internet.

Why we need cryptography?

Without encryption communications over the internet will be very insecure, and it would be very easy for someone to see your data. Fortunately this isn't true, and almost all of the data you get/send over the internet is encrypted and cannot be seen in plain text by someone who got access to it. Now let's look into cryptography in more detail.


I understand why cryptography is important!

Task 2 Types of cryptography

There are two types of cryptography :

• Symmetric
• Asymmetric

What is symmetric cryptography?

Let's say Alice wants to send message to Bob, but she doesn't want to send the message in plain text because anyone can read it.

She  has a recipe how to mess up the letters in a way that no one can understand what it means(that is called encryption). Bob has the same recipe but he uses it to order them so it will become readable again(that is called decryption), and he will understand what Alice wrote. The recipe in cryptography is called a key.  In symmetric cryptography both users have the same key to encrypt and decrypt the messages.

What is asymmetric cryptography?

In asymmetric cryptography the encryption and decryption keys are different. The encryption key can be used only for encryption, not for decryption and vice versa. The encryption key is called Public key and the decryption key is called Private key.

Why is asymmetric cryptography used?

Well..because it's more secure! If you are using symmetric cryptography and someone takes your key he can encrypt and decrypt messages that you send. While in asymmetric cryptography he can't decrypt the messages you encrypted with the public key. Only the holder of the Private key can decrypt them. Let's give an example :

Alice wants to talk to Google

Google gives Alice the Public key.

Alice encrypts her message with the public key and sends it to Google.

Google decrypts the message with his private key and sends back what Alice wanted.

And that's how the conversation goes...




Note : Symmetric cryptography is faster than asymmetric, but asymmetric is more secure.

Now let's see what you've learned!



1) What type of cryptography is more secure?

Ans :- Asymmetric



2) What type of cryptography is faster?

Ans :- Symmetric



3) What type of cryptography will a Bank site use?

Ans :- Asymmetric



4) What will you use to encrypt your messages in asymmetric cryptography?

Ans :- public



5) What will you use to decrypt messages in asymmetric cryptography?

Ans :- private



6) Does symmetric cryptography use two different keys for encryption/decryption? (aye/nay)

Ans :- Nay

Task 3 What is a hash?

Hashes are a long strings of letters and numbers generated by hashing algorithms. They take plain text and make it a hash.

The important thing about hashes is that they are not reversible. There's no way to decrypt/decode a hash.

Popular hashing algorithms are : MD5 (Message Digest 5) and SHA (Secure Hash Algorithm).

That's how the word "hello" looks as MD5 hash : 5d41402abc4b2a76b9719d911017c592

What are hashes used for?

The most popular use of hashes is for file identification and storing sensitive data, like passwords. When you create an account on a website your password is converted to hash and this hash is stored in the server's database. So when you login the password that you type in will be converted to a hash, the server will take it and compare it with the hash in it's database, if it's the same that means your password is correct and the server will let you in.


MD5 hashes are also used to ensure the data integrity of files. Because the MD5 hashing algorithm always produces the same output for the same given input, it can be used to compare a hash of the source file with a newly created hash of the destination file to check that it is intact and unmodified.


There are plenty of other hashing algorithms out there, but this room is intended for beginners so we're not going to cover them here.





1) What's the MD5 hash of "hashes are cool"?

Ans :- f762d32e3c160900d94b683e927555b9


2) What does MD5 stand for?

Ans :- Message Digest 5


3) created MD5?


Ans :- Ronald Rivest

Task 4 Decoding/encoding

There's difference between encoding and encrypting. Let's say you have an encrypted file, the only way to decrypt it is using key. While encoded data can be decoded immediately, without keys. It's NOT a form of encryption, it just a way of representing data.

A very popular encoding is Base64. Here's how "hi there" looks with Base64 encoding : aGkgdGhlcmU=



1) Encode the string "cryptographyisuseful" with Base64

Ans :- Y3J5cHRvZ3JhcGh5aXN1c2VmdWw=


2) Decode the string "dGhlIHNlY3JldCB3b3JkIGlzIDogd2F0ZXJtZWxvbg==". What's the secret word?

Ans :- watermelon

Disclaimer

This was written for educational purpose and pentest only.
The author will not be responsible for any damage ..!
The author of this tool is not responsible for any misuse of the information.
You will not misuse the information to gain unauthorized access.
This information shall only be used to expand knowledge and not for causing  malicious or damaging attacks. Performing any hacks without written permission is illegal ..!


All video’s and tutorials are for informational and educational purposes only. We believe that ethical hacking, information security and cyber security should be familiar subjects to anyone using digital information and computers. We believe that it is impossible to defend yourself from hackers without knowing how hacking is done. The tutorials and videos provided on www.hackingtruth.in is only for those who are interested to learn about Ethical Hacking, Security, Penetration Testing and malware analysis. Hacking tutorials is against misuse of the information and we strongly suggest against it. Please regard the word hacking as ethical hacking or penetration testing every time this word is used.


All tutorials and videos have been made using our own routers, servers, websites and other resources, they do not contain any illegal activity. We do not promote, encourage, support or excite any illegal activity or hacking without written permission in general. We want to raise security awareness and inform our readers on how to prevent themselves from being a victim of hackers. If you plan to use the information for illegal purposes, please leave this website now. We cannot be held responsible for any misuse of the given information.



- Hacking Truth by Kumar Atul Jaiswal



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TryHackMe: Startup Write-Up

Abuse traditional vulnerabilities via untraditional means.


TryHackMe is an online platform for learning cyber security, using hands-on exercises and labs and is meant for people starting out in the infosec field. TryHackMe Startup walkthrough

This is write up for a TryHackMe room called Startup linked here.

Enumeration and Scanning

Using nmap, I found that this box had 3 ports open.

The webpage looked like it was still under development.

 

 I then ran gobuster and found a hidden folder.

Looking at the files directory, I saw the following:

Going back to the ftp service, I tried logging in via anonymous user.

The FTP and HTTP directory are the same. This means that we can upload files (read: reverse shell payloads) to the FTP directory which we can then execute on the browser.

Abusing the FTP/HTTP misconfiguration

To test this theory, we move into the /ftp directory as this is the directory where should have permissions to upload files; and upload a test file to see if we can display and execute it in the browser. To do this, I created a test.html page and uploaded it into the /ftp directory; 

Now, to get a shell, we use PentestMonkey’s Reverse-Shell-PHP payload, change the IP and Port and upload it.a

Stabilising the shell

To stabilise the shell, we execute the following steps;
 

1) python -c 'import pty;pty.spawn("/bin/bash")' 

This spawns a Bash shell

2) export TERM=xterm

This will give access to terminal commands like clear

3) Background the shell using Ctrl + Z;

In the native shell, use stty raw -echo; fg

This will turn off the terminal echo (giving access to tab autocompletes, arrow keys etc.) and foregrounds the shell
    

4) alias ll='ls -la'

This is a personal preference as it’s always better to list all current files with all the details which is always a good habit (which the following steps in this room would teach me)

As I would learn, stabilising the shell was extremely important because there was no way I’d actually get a real shell (SSH or otherwise).

Finding out the Secret Spicy Soup Recipe

Now that we have working shell with most of the features, we go to the / directory to see its contents with our ll command. As you view the contents, make sure to not rush and miss out on anything. If you do so, then you should notice some extra (Hint: Which don’t belong) folders and files here.

They are as follows:

drwxr-xr-x   2 www-data www-data  4096 Nov  9 02:12 incidents
-rw-r--r--   1 www-data www-data   136 Nov  9 02:12 recipe.txt
drwxr-xr-x   2 root     root      4096 Nov  9 02:10 vagrant

 

Opening up recipe.txt should help us with some clues on the Secret Spicy Soup Recipe

 

Thoughts: I was honestly stuck here for a little while as I didn’t know what to do and rushed over the directories. It was only after I took a step back and went through all the directories and files that I could notice the extra directories and files. Lesson/Pro-Tip: Take your time to go over each folder and file to see any sus discrepancies
 

1) What is the secret spicy soup recipe?

Ans :- love

Getting User privileges

There are more out-of-place folders here, namely, /incidents and /vagrant. Going into the /incidents directory we see a suspicious.pcapng packet capture file.

That’s pretty sus ngl.

To view it you could either cat it out onto the terminal (like a pleb lmao) Or you could copy it to the /ftp directory to download and view it onto your system (like moi). To do so, simply run;

www-data@startup:/incidents$ cp suspicious.pcapng /var/www/html/files/ftp/

 

We know that it’s an Apache Server on Ubuntu and /var/www/html is where the Apache Server files exist.

Now, download and view the file with Wireshark with

 

❯ wireshark suspicious.pcapng

 

The best way to find useful information from a packet capture is to go through each TCP/HTTP stream and try to find something which seems useful.

 

If you do so, you’ll come around a TCP Stream which seems like a packet capture of a Remote Connection session (telnet maybe?)

 We notice three things here;

•     They used the same shell stabilising techniques as us!
•     Seems like the user lennie is accessing the session and
•     He has entered his password!

Hence, we simply get user (lennie) privileges by;

www-data@startup:/incidents$ su lennie
Password: c4nt**************
lennie@startup:/incidents$ whoami
lennie

Going into /home/lennie we see the user.txt

2) What are the contents of user.txt?

Ans :- thm{03ce3d619b0ccbfb3b7fc81e46c0e79}

Getting the Root Privileges

In out home directory, we see that there are two directories, one which is owned by root. Maybe this can help us get root?

 The /scripts directory has the following files;

It’s important to take note of the permissions and last modified information here;

• Both the files here can only be modified by root
• startup_list.txt has been modified preettyyy recently (1 min ago)

The contents of planner.sh are as;


#!/bin/bash
echo $LIST > /home/lennie/scripts/startup_list.txt
/etc/print.sh


We see that it calls another script /etc/print.sh; which is owned by lennie!

The contents of /etc/print.sh are;


#!/bin/bash
echo "Done!"



To reiterate, we have a script owned by us which is run by another script owned by root.


If only there was a way for root to run that script… Surprise, surprise! Root does that for ourselves! In concise;

•     Root Cron Job runs planner.sh
•     Modifies startup_list.txt
•     Runs /etc/print.sh

Since we notice that startup_list.txt is being modified every minute by some cron job, it is safe to assume that it is planner.sh which does it.

Hence we can modify the /etc/print.sh script and wait one minute for root to run it!

So, we make a directory in the /tmp folder to store the flag;


mkdir /tmp/lol

And adding the following to /etc/print.sh;

cat /root/root.txt > /tmp/lol/flag

 

should do the job of getting the flag for us!


Thoughts: I was stuck here for over a day before I noticed that the file gets modified by some cron job. I tried finding cron jobs but since the cron running here is a user job and not a system one; something which I learnt because of this room; I couldn’t find one to confirm my suspicions about a cron job running and got sucked into unnecessary rabbit holes.

Wait for one minute for the cron job to run and;

 

3) What are the contents of root.txt?

Ans :- thm{f963aaa6a430f21022215ae15c3d76d}

Disclaimer

NIS - Linux Part I

Enhance your Linux knowledge with this beginner friendly room! 

Task 1 What is this room about?

In this task, we will be looking back at ZTH Linux and a few other topics that seem to cause some trouble around the beginners. A requirement for this room is to finish the Learn Linux room - https://tryhackme.com/room/zthlinux.

As it covers all the basic requirements and this is just a follow up to it in order to strengthen the understanding you gained throughout the room. In order to do so.
Below I will be asking a few questions related to that room, so please, make sure to complete it first :). If you didn't feel free to go through the tasks and come back to this once you finished the room.

The commands you are allowed to use in this room are:

•     cat
•     tac
•     head
•     tail
•     xxd
•     base64
•     find
•     grep
•     echo
•     xargs
•     hexeditor
•     tar
•     gzip
•     7zip
•     binwalk

Bear in mind, commands such as cd are not allowed.


*The SSH credentials are chad:Infinity121 *

1)What is shiba3's password?

Ans :-

 

2) What is shiba4's password?

Ans :- 

3)What is the root.txt flag? 

Ans :- 

Task 2 ls

This task should give you a better understanding of the command ls and a few of the switches that the command can take and what are some of the more efficient ones. Below is a screenshot of the help menu, however, feel free to use the man. TryHackMe NIS - Linux Part I

Task 3 cat

Hopefully, the above screenshot should help you go through a few of the tasks below, however further research is required. A good thing to know is that ls supports multiple ways of chaining switches. Such as:

•     ls -x -y -z
•     ls -xyz

In some cases, you would need to keep evidence of your findings. Below we will start with some basic commands you should be familiar with.

 

1) How do you run the ls command?

Ans :- ls

2) How do you run the ls command to show all the files inside the folder?

Ans :- ls -a

3) How do you run the ls command to not show the current directory and the previous directory in the output? (almost everything)

Ans :- ls -a

4) How do you show the information in a long listing format using ls?

Ans :- ls -l
 

5) How do you show the size in readable format? e.g. k, Mb, etc

Ans :- ls -h

6) How do you do a recursive ls?

Ans :- ls --recursive

7) How many files did you locate in the home folder of the user?(non-hidden and not inside other folders)

Ans :- 13



 

Task 3 cat

The cat command is one of the most common Linux commands that people use, however, in some instances, the cat command cannot be used as it's removed.

Below is a screenshot of the cat command's help menu.


 

But, as we are professionals we know about a few alternatives of going around it:
 
The first command we are going to learn about is tac. Yes, cat spelt backwards. It is similar to the command, with the downside of less functionality.

Thus being a good tool to add to your toolbelt when you are limited by your reverse shell.


Another tool that can be used is head. This is usually used to get the beginning part of a file, however, you can use it to your heart's content and grab as many lines as you want.

One more tool that can be used to grab the content of a file is tail. This is similar to the head command, however, as the name implies it will grab the last part of a file.

Another useful command is xxd. this can be used to generate a hex dump of the content of a file. Then, if you want you can either just read the text from the right-hand side or convert from hex to ASCII.

Similar to the above you can use the base64 command to convert the text to base64 and then convert it back to ASCII.

1) What is the content of cat.txt?

Ans :- THM{11adbee391acdffee901}



2) What is the content of tac.txt?

Ans :- THM{acab0111aaa687912139}



3) What is the content of head.txt?

Ans :- THM{894abac55f7962abc166}



4) What is the content of tail.txt?

Ans :- THM{1689acafdd20751acff6}



5) What is the content of the xxd.txt?

Ans :- THM{fac1aab210d6e4410acd}



6) What is the content of base64.txt?

Ans :- THM{aa462c1b2d44801c0a31}

Task 4 find

The find command is one of the most useful commands on a Linux operating system.

This command can help us find specific files that match a pattern like:

find . -name *.txt

Or we can use it to find files that have a specific extension:

find / -type f -name "*.bak"

This simple command will start browsing the machine directory, finding all the files with extension .bak (backup).

But we can also use it to find files that have the SUID or SGID bit set like so:

find / -type f \( -perm -4000 -o -perm -2000 \) -exec ls -l {} \;

This command combines permissions 4000 (SUID) and 2000 (SGID)


 

1) How many .txt files did you find in the current folder?

Ans :- 8

2) How many SUID files have you found inside the home folder?

Ans :- 0

Task 5 grep

grep is a really useful command to grab text from files.

Let's read through a few examples of grep commands and see how we can use them for our own benefit in a scenario.

grep "word" file



 

Grep not only allows us to check if a certain word exists in the file but also outputs us the context in which the word had appeared. As you can see on the screenshot above, we were able to find an exact match to the word 'if' in the file script.py.

We can also compare two files with similar names using.

 

grep "word" file*

How many times does the word "hacker" appear in the grep files? (including variations)

Task 6 sudo

sudo command allows certain users to execute a command as another user, according to settings in the /etc/sudoers file. By default, sudo requires that users authenticate themselves with a password of another user.

In the real-life scenario, sudo is mostly used to switch to root account and gain an ability to fully interact with the system.

sudo -l appears to be the most commonly used switch. It can always tell you which commands are you allowed to run as another user on the following system, and in some cases, can give you a clue to root access.

 

1) Is the user allowed to run the above command? (Yay/Nay)

Ans :- 

Task 7 chmod

The chmod command sets the permissions of files or directories.

Those permissions are divided between three main characters:

   

• User
• Group
• Other

All of them can rather read, write or execute a file. Permission to do so can be granted using chmod.

It can be done rather using letter notation or numerical values.

Let's take a look at the following command:

 

chmod u=rwx,g=rx,o=rw myfile

•     u = user is being giver read, write and execute permission
•     g = group can now read and execute
•     o = other can read and write

This long notion can be eliminated by numerical values for permission. There are exactly four of them:

• 0 stands for "no permission."
• 1 stands for "execute";
• 2 stands for "write";
• 4 stands for "read".
  

Those values can be easily combined by adding them up.

For example, permission to read, write and execute would be 7 (1 + 2 + 4).

 

chmod 777 file

 

The following command will grant full file access to everyone on the system. (Those numerical values can be easily calculated using an interactive chmod-calculator).

chmod command comes in handy with ssh key files (id_rsa). By editing their permissions to 'user read-write only' we can use other people's id_rsa files to connect via ssh.

chmod 600 id_rsa

Task 8 echo

echo is the most fundamental command found in most operating systems. It used to prints text to standard output, for example, terminal. It is mostly used in bash scripts in order to display output directly to user's console.





 

echo can also be used to interact with other system commands and pass some value to them.

echo also has a small trick which allows to print out any command output to console.

echo "$( [command] )"

 

What command would you use to echo the word "Hackerman" ?

Task 9 xargs

xargs command builds and executes command lines from standard input. It allows you to run the same command on a large number of files.





 

xargs is often used with the find command, in order to easily interact with its input.

Let's take a look at the given command:

find /tmp -name test -type f -print | xargs /bin/rm -f

On the left side, we can see a command which should technically display all files under a name 'test'. xargs command on the left allows us to execute rm (remove) on those files and easily delete all of them.
Same can be done with reading all the files under the name 'test'.

 

1) How would you read all files with extension .bak using xargs?

Ans :- find / -name *.bak -type f -print | xargs /bin/cat

Task 10 hexeditor

Hexeditor is an awesome tool designed to read and modify hex of a file, this comes in handy especially when it comes to troubleshooting magic numbers for files such as JPG, WAV and any other types of files. This tool is also helpful when it comes to CTFs and text is hidden inside a file or when the magic number of a file was altered.

Another tool that is good for this kind of scenarios is called strings but we won't be talking about it in this part of our course.







 

For this task, I will be providing you with resources to help you along your journey around challenges you might be facing in which you need the hexeditor tool.

A few resources I use for tasks that involve analysing files and fixing the magic 

number I use the following resources:

https://en.wikipedia.org/wiki/List_of_file_signatures

https://gist.github.com/leommoore/f9e57ba2aa4bf197ebc5

https://www.garykessler.net/library/file_sigs.html

Task 11 curl 

The curl command transfers data to or from a network server, using one of the supported protocols (HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP or FILE). It is designed to work without any user interaction, so could be ideally used in a shell script.

curl is a huge tool with a lot of switches and possibilities. Let's take a look at some of the most important ones.

curl http://www.ismycomputeron.com/






 

The most basic command. Fetches data from the website using the HTTP protocol, and display it using standard HTML code. This is essentially the same as "viewing the source" of the webpage.

The following command will limit the connection speed to 1,234 bytes/second:

curl --limit-rate 1234B http://www.ismycomputeron.com/

Another example is saving the output to a file using either:

-o to save the file under a different name
curl -o loginpage.html https://tryhackme.com/login

-O to save the file under the same name:

curl -O https://tryhackme.com/login

Or, you might be interested in fetching the headers silently?

curl -I -s https://tryhackme.com

 

1) How would you grab the headers silently of https://tryhackme.com but grepping only the HTTP status code?

Ans :- 

Task 12 wget

The wget command downloads files from HTTP, HTTPS, or FTP connection a network.






 

wget http://somewebsite.com/files/images.zip

Adding a -b switch will allow us to run wget in the background and return the terminal to its initial state.

wget -b http://www.example.org/files/images.zip




1) What command would you run to get the flag.txt from https://tryhackme.com/ ?

Ans :- 

2) What command would you run to download recursively up to level 5 from https://tryhackme.com ?

Ans :-

Task 13 tar

tar is a command that allows creating, maintain, modify, and extracts files that are archived in the tar format.

The most common example for tar extraction would be:

tar -xf archive.tar

-x tells tar to extract files from an archive.

-f tells tar that the next argument will be the name of the archive to operate on.
 

1) What is the flag from the tar file?

Ans :-

Task 14 gzip

gzip - a file format and a software application used for file compression and decompression. gzip-compressed files have .gz extension.

A gzip file can be decompressed using a simple gzip -d file.gz command, where -d stands for decompress.


1) What is the content of gzip.txt?

Ans :-

Task 15 7zip

7-Zip is a free and open-source file archiver, a utility used to place groups of files within compressed containers known as "archives".

7z is as simple as the gzip or tar and you can use the following command:

7z x file.zip to extract the file

This tool comes in handy as it works with a lot more file extensions than other tools. You name the archive extension and 7z should be the tool for you.

 

1) What is the flag inside the 7zip file?

Ans :-

Task 16 binwalk

binwalk allows users to analyze and extract firmware images and helps in identifying code, files, and other information embedded in those, or inside another file, taking as an example steganography.

A simple command such as binwalk file allows us to perform a simple file scan and identify code information.

binwalk -e file allows us to extract files from firmware. This method is usually used in CTFs, where some important information can be hidden within the file.

binwalk -Me file does the same as-e, but recursively.

1) What is the content of binwalk.txt?

Ans :-

Disclaimer