Finished writeups till level 5

Writeup.md

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+# Level 0
+
+The command to be run is
+
+```
+ssh bandit0@bandit.labs.overthewire.org -p 2220
+```
+
+Lets understand the structure of the command first.
+
+- `ssh`, part of the OpenSSH package is the tool used to remotely connect to servers via the CLI.
+- `bandit0` is the username we wish to log in with.
+- `@bandit.labs.overthewire.org` is the domain name of the server we want to connect to.
+- `-p 2220` is a flag specifying the port we want to connect to the server with.
+
+Once we log in, we're greeted with the following page
+
+```
+                         _                     _ _ _
+                        | |__   __ _ _ __   __| (_) |_
+                        | '_ \ / _` | '_ \ / _` | | __|
+                        | |_) | (_| | | | | (_| | | |_
+                        |_.__/ \__,_|_| |_|\__,_|_|\__|
+
+
+                      This is an OverTheWire game server.
+            More information on http://www.overthewire.org/wargames
+
+bandit0@bandit.labs.overthewire.org's password:
+```
+
+We paste the password we were given (bandit0), and are dropped into a shell session.
+
+```
+bandit0@bandit:~$
+```
+
+# Level 0 -> Level 1
+
+The password for Level 1 is stored as plaintext in a file called readme in the home directory. Thus, we use the `cat` shell utility to show it.
+
+```
+bandit0@bandit:~$ cat readme
+NH2SXQwcBdpmTEzi3bvBHMM9H66vVXjL
+```
+
+The `cat` command simply outputs the contents of a file to the terminal. We run the same ssh command used for bandit0, but with the username being bandit1 instead.
+
+```
+~ $ ssh bandit1@bandit.labs.overthewire.org -p 2220
+                         _                     _ _ _
+                        | |__   __ _ _ __   __| (_) |_
+                        | '_ \ / _` | '_ \ / _` | | __|
+                        | |_) | (_| | | | | (_| | | |_
+                        |_.__/ \__,_|_| |_|\__,_|_|\__|
+
+
+                      This is an OverTheWire game server.
+            More information on http://www.overthewire.org/wargames
+
+bandit1@bandit.labs.overthewire.org's password:
+```
+
+We then input the password in (NH2SXQwcBdpmTEzi3bvBHMM9H66vVXjL), and thus get to Level 1.
+
+# Level 1 -> Level 2
+
+Here the password is stored in a file called `-`. As the name is also the indicator for reading from stdin, simply running `cat -` does nothing here.
+We have to run a modified version of it.
+
+```
+bandit1@bandit:~$ cat ./-
+rRGizSaX8Mk1RTb1CNQoXTcYZWU6lgzi
+```
+
+Here, the `./` indicates the current working directory, so `cat` knows its trying to read from a file instead of stdin. We use the password to login to bandit2, and successfully pass the first stage.
+
+# Level 2 -> Level 3
+
+Here, the password is stored in a file called `spaces in this filename`.
+
+Trying to run cat normally gives us this
+
+```
+bandit2@bandit:~$ cat spaces in this filename
+cat: spaces: No such file or directory
+cat: in: No such file or directory
+cat: this: No such file or directory
+cat: filename: No such file or directory
+```
+
+`cat` does not realize our arguments are but one. We thus wrap the filename around quotation marks to indicate that it's a single argument.
+
+```
+bandit2@bandit:~$ cat "spaces in this filename"
+aBZ0W5EmUfAf7kHTQeOwd8bauFJ2lAiG
+```
+
+We ssh into the next level, enter the password given (aBZ0W5EmUfAf7kHTQeOwd8bauFJ2lAiG) into the prompt, and finish the second stage.
+
+# Level 3 -> 4
+
+The password is said to be stored in a hidden file in the `inhere` directory. As hidden files are always prefixed with a `.` at the beginning of their filenames, we can the following command.
+
+```
+bandit3@bandit:~$ cat inhere/.*
+cat: inhere/.: Is a directory
+cat: inhere/..: Is a directory
+2EW7BBsr6aMMoJ2HjW067dm8EgX26xNe
+```
+
+- The `inhere/` indicates that the file whose contents we want to output is in the `inhere` directory.
+- The `.*` is a `glob` matcher, which translates to *cat every file that starts with the character `.` and has an indefinite number of characters after it.* We use it for brevity's sake, as it sidesteps knowing the name of the file inside the `inhere` directory entirely. The only problem is the two error messages output by `cat`, indicating it tried to output the contents of a directory instead of a file.
+
+# Level 4 -> 5
+
+The password is stored in the only human-readable file in the inhere directory. We use a new command, `file` here
+
+```
+bandit4@bandit:~$ file inhere/*
+inhere/-file00: data
+inhere/-file01: data
+inhere/-file02: data
+inhere/-file03: data
+inhere/-file04: data
+inhere/-file05: data
+inhere/-file06: data
+inhere/-file07: ASCII text
+inhere/-file08: data
+inhere/-file09: data
+```
+
+The `file` command allows us to determine the file type of a file without directly using `cat` on it. We can see that there's only one file *(-file07)* with the label *ASCII text* attached to it, meaning it only contains human-readable characters. We cat the file and get the password for the next level.
+
+```
+bandit4@bandit:~$ cat inhere/-file07
+lrIWWI6bB37kxfiCQZqUdOIYfr6eEeqR
+```
+