Beginner Linux for Ethical Hackers - Users and Privileges

Key Takeaways

ok so now we're going to cover users and privileges so in the last video we touched a little bit on privileges with our LS l a and we touched a little bit on users by changing the password of our root account so now we'll cover a few more commands regarding those so if we look again at LS la you could see all this crazy jumbled wordage over here right so it actually means something so we look at the first line here if we see a dash like this a hyphen that means it's a file if we see a D that means it's actually a directory and then you see our W and X so our W and X actually means read/write/execute it's the permission settings that this particular group has now there are three groups here there's the first second and then your third right here right so your first group right here is the owner of the file so it looks like the owner of the file has full read/write execution right and then the next set of three here is actually the permissions for the members of the group that owned the file so this is a group ownership as opposed to actual ownership here so for the people that are in the group that has access to this file they can only read and execute they can't write to it now for the last one this is just all their users so any common user here can actually just read and execute they can't write the document so that comes into play especially when we get into penetration testing because with penetration testing we're looking to have full access right so we're always going to be looking for that folder that has full read/write typically if we look at temp that's our temp folder a lot of times you see the temp folder has full read/write execute so when we're doing penetration testing we're trying to upload some sort of exploit we might actually upload it into the temp folder because that's where we can exit get those those files however we could also be looking for other full read/write/execute files where we need to modify them and give us root access to a system so it's all about insecure configurations and we're going to cover that more once we get into the actual penetration testing part of the course so for the linux essentials part of the course all we need to worry about is these file permissions another important feature of that is if we were to create a script our scripts not going to be able to run until it has full access so how do we change access here so let's make a file I'm just going to make we'll just echo another text document right so we'll just say hello and actually I type that in backwards so hello and we'll call it hello text so if we LS here by default we only have read write and then read access for everybody else meaning if we wanted to read it we could say cat which we're going to get into later cat hello Tex it just says hello so what can we do here well we can use something called change mode in changing mode is ch mo d and we have a couple options here so we can do a plus right and we could say well we want read write execute or we just want execute but another way I like doing it is you have a number feature so the one you really need to know is all sevens sevens gives you full read/write access across the board so if we say chmod 777 hello dot txt now we LS la and you notice that hello dot Tex turns green that means it is full rewrite and here you go we've got the dash here saying it's a file and we got read write execute across the board so this is how we change file permissions you don't need to necessarily know about the other numbers in terms of penetration testing it becomes more in terms of configuration and security management of files if you were to get down that path so to stay on the easiest path just remember seven seven seven or plus X will work as well so changing the mode is is critical and we're going to cover it time and time again throughout the course once we get a little bit deeper so a couple more things we need to talk about say we wanted to add a new user well there's a feature called add user so we say add user and one or two names is allowed so we need to add user say John ok so it made something for John let's give him a password give them a password again and we'll just hit enter for the defaults it's all correct okay so we now have a user named John and we can confirm that we can actually cat the Etsy password file here and you see down at the very bottom we have this user John so this Etsy password file you're going to become very familiar with because it shows you all the users now this will there's a lot of times where you're doing penetration testing you're gonna have access to this Etsy passer file because it doesn't provide the password anymore it used to a long time ago passwords are now in the shadow file so you actually have a little bit of access and information disclosure here at the hands of poor configuration so you see that I've created a user John well that gives us a little bit infor information say there's SSH on a machine or something else we can use that username of John to try to break into the machine so we'll cover that again later but if we wanted to see what the Etsy shadow file looks like now we come in here and you've got these these jumbled stuff here right so it's just a hashing format so what we're doing is we can actually use a tool like hash cat to break this down and crack these passwords now a password a password will be very easy but just know that if you have access to the etsy shadow file you have a good chance of cracking a password depending on your capabilities and depending on the strength of the password that'll allow you access to a machine so something to think about there okay so now we have our user John let's go ahead and switch to him so we can use something called su which stands for switch user and we'll say switch user John okay so it automatically gave us John here let's see if we could switch back to root okay we can't just switch back to root because we need roots password right so we can type in password and that works but if we didn't know the password then we'd be stuck on John we are able to access John because we were already root so this comes into play in terms of users let's go back to John here now if your user you have to be able to do certain things you need permission to do certain things I should say right so root has full access and permission to do everything but John we just created John John doesn't have any sort of access so if we wanted to if we wanted to change the password say we want to change the password for for rude I can't modify the password information because I don't have that kind of access now there is something called a pseudo which would provide John that access if we gave it to him so it's called a pseudo verse file and basically anybody in that sudoers file can change permissions given if they are a pseudo user right so we would type in sudo password root and it's going to ask for the password for John but you're gonna notice hey John's not in the pseudo or is file John can't do this so John has base permissions right and we're gonna counter that a lot of times in penetration testing where if we get in we'll get something called lower privilege and we'll get an account like John and we're gonna try to escalate in the root but we just can't do it you know the chances of doing a doing that and having a John in a su doors file is just not high it's possible but it's not likely so for now just know that if you want a user other than root to have access to file permissions you need to have them in the su doors file that becomes useful too and penetration testing because you can look at the sewers file if you have access to see what users have sudo privileges okay so that is it for this lesson in the next lesson we're going to be covering Network commands and moving on gradually towards scripting so let's go ahead and get there and I will see when we get over there [Music] [Music] you