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This video is a quick walkthrough of the Flask application you'll be analyzing for security issues. Especially if you're unfamiliar with Flask, this should help you get situated and lead to a more fruitful conversation with your LLM. If you're already comfortable with Flask, feel free to skip this walkthrough. Okay, for this one, the first thing we need to do is install SQLAlchemy. So that's going to take a couple of minutes to do, so while that's working, I'm just going to look at some of the code. So in our code, what we're doing is we're creating a new Flask application, and this Flask application is going to have a database. And I'm specifying the database URI is going to be sqlite//users.db. And once we have this set up now, and we have a database set up using SQLAlchemy, it's really as easy as that. So the next thing I want to do is with this database, it's going to be having a bunch of users, so I'm going to create a class user. And that class user is going to be using the DB model, and the user is just going to have an ID, a username, and a password. So when I run this, it's going to create an app context, create my database, and now that database, I'll be able to add users to that. And it's just going to give me some of the usual stuff, like welcome to security testing demo, map to the slash route, so basically the homepage, the root of it. But then for using users and for manipulating users, just take a quick look at what's going on here. So first of all, consider the HTTP methods that I'll be using. So I'm going to be routing to the user's endpoints with a get method, and in this case I've defined it that if I want to get users, by definition, that's going to return all users. So it's going to be user.query.all, as you can imagine that's going to query the database for all users, and then it's going to return them jsonified with the user's username and user password. Now, of course, in a real application you wouldn't do this because it would be a bit of a security leak, but you'd have some kind of an admin endpoint or an admin interface that would allow the admin to be able to look at all the users, and that would run code like this. Secondly, also on a get, so get slash user slash a number, that's then going to query the database to find that user, and if they exist, then return that user's username and password. Highly insecure, I know, but again, just for demo purposes. And if it doesn't exist, it can return a user not found with a 404. Now, when you want to add a user, you're generally not going to be getting that, you're going to be posting. So, of course, the route will also support slash user, but this time with the post method, and of course the post method is just going to add a new user, it's going to accept two parameters, the username and password, and then it's going to add a user with that username and password to the database. And if it works, you'll get the return message in json, the user was added successfully. Now, another method in HTTP is put, and this is perfect for editing an existing user. So, if you put slash user slash ID, and then you specify username and password, you will change the existing username and password. Notice that the signature is exactly the same, right? It's going to be slash user slash an identifier, and, you know, they're exactly the same as you have, like, for getting the particular user. But when you do the put method, you're indicating that you're putting some data up to the server, and as a result, that data is going to change the actual user. And then similarly for delete, as you can imagine, it's just going to be a case of you're going to pass up an ID, it will delete that user, and then return the appropriate messages. So, this has been run, it's already good to go, so I'm going to run this code next. So, now the code is run, the server's up and running, it should be good to go. And we can see this threading.thread allows you to use it in Colab, and we have the server actually running here, 172.28.0.12. So, now, if I curl to this server, I can simulate what it would be like calling that server. So, if I were to curl to a get, to list all users, well, we've got no users yet, so this would be empty. So, if I were now to curl a get for slash user slash one, I would be expecting to look for user one, and, of course, my message comes back that there is no user one. It hasn't been found. So, now let's think about posting to create a new user. So, I'm going to post to the slash user endpoint, and I'm going to pass up some JSON with username test user, password secure password, because it is very secure. And when I run it, we'll see the user has been added successfully. I could come over here, and I could try to list all users now, and we could see the user ID one is there. Or I could specifically try to find user one, and we see that user ID one is there. Kind of cool. So, now if I want to put, what does that do? Remember, that edits it. So, what I'm going to do is I'm going to change the user's password from secure password to new secure password. So, if I run that, again, it puts the new data. It shows that it was done successfully. And, for example, if I list user one, we can see user one is ID one, password is new secure password. So, it actually worked. And then, finally, if I want to delete the user, I can just click this one, and now the user has been deleted successfully. And, of course, if I try to get all users, there's nobody there. And if I try to get user one, they don't exist. So, we can see that this code is running for me. The test cases have been set up. And, you know, this is just a really interesting little starter for you to be able to work on to try and think about how you build applications like this. Okay, that's the end of this walkthrough. You'll find the code for this app in the following ungraded lab. I recommend that you open that lab and then move on to the next video for suggestions on specific strategies for analyzing the code.
