hacker | Hacker is a Jekyll theme for GitHub Pages | Theme library

I'm new to Hacker Rank and I'm currently solving problems in the java stack, I tried to solve this algorithm:

A string containing only parentheses is balanced if the following is true: 1. if it is an empty string 2. if A and B are correct, AB is correct, 3. if A is correct, (A) and {A} and [A] are also correct.

Examples of some correctly balanced strings are: "{}()", "[{()}]", "({()})"

Examples of some unbalanced strings are: "{}(", "({)}", "[[", "}{" etc.

Given a string, determine if it is balanced or not.

And I found the following one liner solution which I couldn't understand can someone explain it please?

I have been looking at the Wordfence scan results on my site this morning and see 17 instances which seem to imply malware has ben installed on the server. I would be surprised if this were to be the case but wanted to be sure:

One example,

Filename: wp-admin/menu-header-cron.php File Type: Not a core, theme, or plugin file from wordpress.org. Details: This file appears to be installed or modified by a hacker to perform malicious activity. If you know about this file you can choose to ignore it to exclude it from future scans. The matched text in this file is:

The issue type is: Backdoor:PHP/numeric.rce.8527 Description: Remote code execution malware

Looking at the file in question, the content of this file is:

What I mean is from attacking from hacker like DOS.

I start intern at startup company, my job is to develop a food delivery application. Right now, I'm using firebase with flutterfire package to authenticate and send data. I allow authentication by Anonymously(<-this method is where I concern, can someone DOS by create new UID rapidly?), Facebook, Gmail and AppleID.

I also need to send sensitive informations like credit card and address to store on server. Is there any security risks that I should concern?

Ubuntu 20.04: what are the security risks without firewall?

Installed Ubuntu 20.04, but forget to enable firewall using ufw.

SSH 22 port: use keys(2048 bit) for login, no password. Setting UsePAM=true, any risk?

Any other services that may have security holes without firewall, and hackers can break into the server?

I'm trying to understand the security model in Github Actions (GHA). Let's say I have the following requirements on a public repo:

1. Allow pull requests from forked repos to be opened
2. GHA should run unit tests on pull requests
3. GHA should post unit test results as a PR comment

In order for the third requirement to work, the pull request needs access to the GITHUB_TOKEN with repo write permissions. This will require the following two permissions:

• Run Workflows from fork pull requests.
• Send write tokens to Workflows from fork pull requests

Now if write tokens are sent to the Workflows in fork PRs, what's to prevent a hacker from changing the Workflow in the PR and using it for any number of malicious purposes (creating a malicious release in the original repo or exfiltrating repo secrets)? I understand you can limit the permissions of the token, but this is done within the workflow; the hacker can just as easily remove the limitations as part of the PR.

Is there any way to accomplish the three requirements without this security hole?

In this section, the codecov documentation says:

The upload token is required for all uploads, except originating from public projects using Travis-CI, Circle CI, Azure, Github Actions.

What prevents "hackers" from uploading a fake codecov file and claiming the file was uploaded from a public repository with Codecov enabled?

What makes public projects special?

I am new to the OAuth world and I am trying to understand the benefits of using PKCE over traditional Authorization code grant. (Many of my assumptions could be wrong, so I would thank for your corrections.)

I am a mobile app developer and according to OAuth documentation, client secrets can't be hardcoded in public clients' app code. The reason to avoid hardcoding the client secret is that a hacker could decompile my app and get my client secret.

The hacker with my client secret and my redirect_url, could develop a fake application. If a final user (User1) downloads the real application and the hacker's application (both), the fake application could listen to the real application callback and get the authorization code from it. With the authorization code (from the callback) and the client secret (stolen by decompiling my app), the hacker could get the authorization token and the refresh token and be able to get for example User1's data.

If other users download the real and the fake application, their data would also be in danger. Am I right? Would the hacker need both or could he/she do an attack only with the authorization code? Does the fifth step of the image requires the client secret and authorization code?

The attack is called interception attack.

To solve the the problem of hardcoding client secrets in the public client app and make it impossible for hackers to get the client secret and steal tokens, PKCE was invented. With PKCE, the client app code doesn't need to have the client secret hardcoded as PKCE doesn't need that information to get the tokens of the final users.

The PKCE flow creates a random string, transforms it to a SHA-256 hash value and to Base64. In the second point of the image, that encoded string is sent to the authentication server with the client id. Then the authorization code is sent in the callback and if any malicious app intercepts the code, it wouldn't be able to get the tokens as the fifth point of the image needs the original random string that was created by the legitimate app.

That is great, but if the client secret isn't need any more to get the tokens to access User1 data, how can I avoid a hacker developing a fake app which use PKCE flow with my client id and getting the tokens of the users who think that app is the legitimate one?

As the fifth step of the image don't need any more the client secret to get the tokens, anyone could develop fake apps using my public client id, and if any user downloads the fake app and do the OAuth flow, the hacker could get its tokens and access that users data!

Am I right?

How can I test in Solana Anchor if a hacker can call or invoke certain program functions?

Is it by changing the first element inside the signers array:

I am developing an Sports Mobile App with flutter (mobile client) that tracks it's users activity data. After tracking an activity (swimming, running, walking ...) it calls a REST API developed by me (with springboot) passing that activity data with a POST. Then, my user will be able to view the logs of his tracked activities calling the REST API with a GET.

As I know that my own tracking development isn't as good as Strava, Garmin, Huawei and so on ones, I want to let my app users to connect with their Strava, Garmin and so on accounts to get their activities data, so I need users to authorize my app to get that data using OAuth.

In a first approach, I have managed to develop all the flow of OAuth with flutter using the Authorization Code Grant. The authorization server login is launched by flutter in a user agent (chrome tab), and once the resource owner has done the login and authorize my flutter app, my flutter app takes the authorization code and the calls to the authorization server to get the tokens . So I can say, that my client is my flutter App. When the oauth flow is done, I send the tokens to my Rest API in order to store them in a database.

My first idea was to send those tokens to my backend app in order to store them in a database and develop a process that takes those tokens, consult resource servers, parses each resource server json response actifvities to my rest API activity model ones and store in my database. Then, if a resource owner consults its activities calling my Rest API, he would get a response with all the activities (the mobiles app tracked ones + Strava, Garmin, resource servers etc ones stores in my db).

I have discarded the option to do the call to the resource servers directly from my client and to my rest api when a user pushes a syncronize button and mapping those responses directly in my client because I need the data of those resource servers responses in the backend in order to implement a medal functionality. Further more, Strava, Garmin, etc have limits of usage and I don't want to let my resource owners the hability to push the button the times they want.

Here is the flow of my first idea:

Steps:

1. Client calls the authorization server launching a user agent to an oauth login. In order to make the resource owner login and authorize. The url and the params are hardcoded are hardcoded in my client.

2. Resource owner logins and authorize client.

3. Callback is sent with code.

4. Client captures code of the callback and makes a post to he authorization server to get the tokens. As some authorization servers accept PKCE, I am using PKCE when its possible, to avoid attacks and hardcoding my client secret in my client. Others like Strava's, don't allow PKCE, so I have to hardcode the client secret in my client in order to get the tokens.

5. Once the tokens are returned to my client, I send them to my rest api and store in a database identifying the tokens resource owner.

To call the resource server:

1. One periodic process takes the tokens of each resource owner and updates my database with the activities returned from each resource server.

2. The resource owner calls the rest api and obtains all the activities.

The problem to this first idea is that some of the authorization servers allow implementing PKCE (Fitbit) and others use the client secret to create the tokens (Strava). As I need the client secret to get the tokens for some of those authorization servers, I have hardcoded the secrets in the client and that is not secure.

I know that it is dangerous to insert the client secrets into the client as a hacker can decompile my client and get the client secret. I can't figure how to get the resource owner tokens of Strava without hardcoding the client secret if PKCE is not allowed in the authorization server.

As I don't want to hardcode my client secrets in my client because it is insafe and I want to store the tokens in my db, I dont see my first approach as a good option. Further more, I am creating a POST request to my REST API in order to store the access token and refresh token in my database and if i am not wrong, that process can be done directly from the backend.

I am in the situation that I have developed a public client (mobile app) that has hardcoded the client secrets because I can't figure how to avoid doing that when PKCE isn't allowed by the authorization server to get the tokens.

So after thinking on all those problems, my second idea is to take advantage of my REST API and do the call to the authorization server from there. So my client would be confidential and I would do the OAuth flow with a Server-side Application.

My idea is based on this image.

In order to avoid the client secret hardcoding in my mobile client, could the following code flow based on the image work and be safe to connect to Strava, Garmin, Polar....?

Strava connection example:

MOBILE CLIENT

• Mobile public Client Calls my Rest API to get as a result the URI of Strava Authorization server login with needed params such as: callback, redirect_uri, client_it, etc.

• Mobile client Catches the Rest API GET response URI.

• Mobile client launches a user agent (Chrome custom tab) and listen to the callback.

USER AGENT

• The login prompt to strava is shown to the resource owner.

• The resource owner inserts credentials and pushes authorize.

• Callback is launched

MOBILE CLIENT

• When my client detects the callback, return to client and stract the code from the callback uri.

• Send that code to my REST API with a post. (https://myrestapi with the code in the body)

REST API CLIENT

• Now, the client is my REST API, as it is going to be the one that calls the authorization server with the code obtained by the mobile client. The client will take that code and with the client secret hardcoded in it will call to the Authorization server. With this approach, the client secret is no more in the mobile client, so it is confidential.

• The authorization server returns the tokens and I store them in a database.

THE PROCESS

• Takes those tokens from my database and make calls to the resource servers of strava to get the activities. Then parses those activities to my model and stores them into the database.

Is this second approach a good way to handle the client secrets in order to avoid making them public? Or I am doing something wrong? Whatr flow could I follow to do it in the right way? I am really stuck with this case, and as I am new to OAuth world I am overwhelmed with all the information I have read.