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Patching process quality

Linux patching process quality recently became noticeably worse so for example upgrade of 8.0 to 8.3 might break some functionality. Appling just security pataches and trailing the most recent minor release by two (using 8.1 in case of RHEL8) or even three minor releases is safer in current circumstances.

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[Jun 12, 2021] Seven-year-old make-me-root bug in Linux service polkit patched

Highly recommended!
Linux systems that have polkit version 0.113 or later installed – like Debian (unstable) , RHEL 8 , Fedora 21+ , and Ubuntu 20.04 – are affected.
Jun 12, 2021 |

A seven-year-old privilege escalation vulnerability that's been lurking in several Linux distributions was patched last week in a coordinated disclosure.

In a blog post on Thursday, GitHub security researcher Kevin Backhouse recounted how he found the bug ( CVE-2021-3560 ) in a service called polkit associated with systemd, a common Linux system and service manager component.

Introduced in commit bfa5036 seven years ago and initially shipped in polkit version 0.113, the bug traveled different paths in different Linux distributions. For example, it missed Debian 10 but it made it to the unstable version of Debian , upon which other distros like Ubuntu are based.

Formerly known as PolicyKit, polkit is a service that evaluates whether specific Linux activities require higher privileges than those currently available. It comes into play if, for example, you try to create a new user account.

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Backhouse says the flaw is surprisingly easy to exploit, requiring only a few commands using standard terminal tools like bash, kill, and dbus-send.

"The vulnerability is triggered by starting a dbus-send command but killing it while polkit is still in the middle of processing the request," explained Backhouse.

Killing dbus-send – an interprocess communication command – in the midst of an authentication request causes an error that arises from polkit asking for the UID of a connection that no longer exists (because the connection was killed).

"In fact, polkit mishandles the error in a particularly unfortunate way: rather than rejecting the request, it treats the request as though it came from a process with UID 0," explains Backhouse. "In other words, it immediately authorizes the request because it thinks the request has come from a root process."

This doesn't happen all the time, because polkit's UID query to the dbus-daemon occurs multiple times over different code paths. Usually, those code paths handle the error correctly, said Backhouse, but one code path is vulnerable – and if the disconnection happens when that code path is active, that's when the privilege elevation occurs. It's all a matter of timing, which varies in unpredictable ways because multiple processes are involved.

The intermittent nature of the bug, Backhouse speculates, is why it remained undetected for seven years.

Linux systems that have polkit version 0.113 or later installed – like Debian (unstable) , RHEL 8 , Fedora 21+ , and Ubuntu 20.04 – are affected.

"CVE-2021-3560 enables an unprivileged local attacker to gain root privileges," said Backhouse. "It's very simple and quick to exploit, so it's important that you update your Linux installations as soon as possible." ®

[Jun 12, 2021] Seven years old bug in Polkit gives unprivileged users root access

Highly recommended!
The polkit service is used by systemd. Linux systems that have polkit version 0.113 or later installed – like Debian (unstable), RHEL 8, Fedora 21+, and Ubuntu 20.04 – are affected. "CVE-2021-3560 enables an unprivileged local attacker to gain root privileges," said Backhouse. "It's very simple and quick to exploit, so it's important that you update your Linux installations as soon as possible."
See Red Hat Advisory ...
Jun 12, 2021 |

Ancient Linux bugs provide root access to unprivileged users

Security researchers have discovered some 7-year-old vulnerabilities Linux distribution

Can be used by unprivileged local users to bypass authentication and gain root access.

The bug patched last week exists in Polkit System Service, a toolkit used to assess whether a particular Linux activity requires higher privileges than currently available. Polkit is installed by default on some Linux distributions, allowing unprivileged processes to communicate with privileged processes.

Linux distributions that use systemd also use Polkit because the Polkit service is associated with systemd.

This vulnerability has been tracked as CVE-2021-3560 and has a CVSS score of 7.8. It was discovered by Kevin Backhouse, a security researcher on GitHub. He states that this issue occurred in 2013 with code commit bfa5036.

Initially shipped with Polkit version 0.113, it has moved to various Linux distributions over the last seven years.

"If the requesting process disconnects from dbus-daemon just before the call to polkit_system_bus_name_get_creds_sync begins, the process will not be able to get the unique uid and pid of the process and will not be able to verify the privileges of the requesting process." And Red Hat Advisory ..

"The biggest threats from this vulnerability are data confidentiality and integrity, and system availability."

so Blog post According to Backhouse, exploiting this vulnerability is very easy and requires few commands using standard terminal tools such as bash, kill and dbus-send.

This flaw affects Polkit versions between 0.113 and 0.118. Red Hat's Cedric Buissart said it will also affect Debian-based distributions based on Polkit 0.105.

Among the popular Linux distributions affected are Debian "Bullseye", Fedora 21 (or later), Ubuntu 20.04, RHEL 8.

Polkit v.0.119, released on 3rd rd We will address this issue in June. We recommend that you update your Linux installation as soon as possible to prevent threat attackers from exploiting the bug.

CVE-2021-3560 is the latest in a series of years ago vulnerabilities affecting Linux distributions.

In 2017, Positive Technologies researcher Alexander Popov discovered a flaw in the Linux kernel introduced in the code in 2009. Tracked as CVE-2017-2636, this flaw was finally patched in 2017.

Another old Linux security flaw indexed as CVE-2016-5195 was introduced in 2007 and patched in 2016. This bug, also known as the "dirty COW" zero-day, was used in many attacks before the patch was applied.

Ancient Linux bugs provide root access to unprivileged users

Source link Ancient Linux bugs provide root access to unprivileged users

[Feb 02, 2021] RedHat local repository and offline updates

Aug 03, 2018 |

My company just bought a two redhat license for two physical machines , the machines wont be accessible via internet , so we have an issue here regarding the updates , patches , ... etc .

i am thinking of configuring a local repository to be accessible via internet and have all the necessary updates but there is a problem here that i have only two licenses , is it applicable if i activate the local repository for the updates and one of my two service machines , or is there any other way like if there is some sort of offline package that i can download it separately from redhat and update my machines without internet access ?

thanks in advance


You have several options:

See How can we regularly update a disconnected system (A system without internet connection)? for details.

[Feb 02, 2021] How can we regularly update a disconnected system (A system without internet connection)

May 02, 2019 |

Solution Verified - Updated August 10 2017 at 12:12 PM -


Depending on the environment and circumstances, there are different approaches for updating an offline system.

Approach 1: Red Hat Satellite

For this approach a Red Hat Satellite server is deployed. The Satellite receives the latest packages from Red Hat repositories. Client systems connect to the Satellite and install updates. More details on Red Hat Satellite are available here: . Please also refer to the document Update a Disconnected Red Hat Network Satellite .

Approach 2: Download the updates on a connected system

If a second, similar system exists

then the second system can download applicable errata packages. After downloading the errata packages can be applied to other systems. More documentation: How to update offline RHEL server without network connection to Red Hat Network/Proxy/Satellite? .

Approach 3: Update with new minor release media

DVD media of new RHEL minor releases (i.e. RHEL6.1) are available from RHN. These media images can directly on the system be used for updating, or offered i.e. via http and be used from other systems as a yum repository for updating. For more details refer to:

Approach 4: Manually downloading and installing or updating packages

It is possible to download and install errata packages. For details refer to this document: How do I download security RPMs using the Red Hat Errata Website? .

Approach 5: Create a Local Repository

This approach is applicable to RHEL 5/6/7. With a registered server that is connected to Red Hat repositories, and is the same Major version. The connected system can use reposync to download all the rpms from a specified repository into a local directory. Then using http,nfs,ftp,or targeting a local directory (file://) this can be configured as a repository which yum can use to install packages and resolve dependencies.

How to create a local mirror of the latest update for Red Hat Enterprise Linux 5, 6, 7 without using Satellite server?

Checking the security erratas :-

To check the security erratas on the system that is not connected to the internet, download the copy the updateinfo.xml.gz file from the identical registered system. The detailed steps can be checked in How to update security Erratas on system which is not connected to internet ? knowledgebase.

Root Cause

Without a connection to the RHN/RHSM the updates have to be transferred over other paths. These are partly hard to implement and automate.

This solution is part of Red Hat's fast-track publication program, providing a huge library of solutions that Red Hat engineers have created while supporting our customers. To give you the knowledge you need the instant it becomes available, these articles may be presented in a raw and unedited form. 8 Comments Log in to comment RZ Community Member 26 points

1 February 2012 3:56 PM Randy Zagar

"Approach 3: update with new minor release media" will not work with RHEL 6. Many packages (over 1500) in the "optional" channels simply are not present on any iso images. There is an open case , but the issue will not be addressed before RHEL 6 Update 4 (and possibly never).

22 May 2014 9:27 AM Umesh Susvirkar

I agree with "Randy Zager" "optional" packages should be available offline along with other channels which are not available in ISO's.

12 July 2016 7:20 PM Adrian Kennedy

Can Approach 5 "additional server, reposync fetching" be applied with RHEL 7 servers?

4 August 2016 8:55 AM Dejan Cugalj


Yes. You need to:
- subscribe server to RH 
- synchronize repositories with reposync util
- up to 40GB per major release of RHEL.
16 August 2016 10:54 PM Michael White

However, won't I need to stand up another RHEL 7 server in additional to the RHEL 6 server?

8 August 2017 7:01 PM John Castranio

Correct. When using an external server to reposync updates, you will need one system for each Major Version of RHEL that you want to sync packages from.

RHEL 7 does not have access to RHEL 6 repositories just as RHEL 6 can't access RHEL 7 repositories

15 January 2019 10:14 PM BRIAN KEYES

what I am looking for is the instructions on the reposync install AND how to update off line clients

do I have to manually install apache?

16 January 2019 10:50 PM Randy Zagar

You will need: a RH Satellite or RH Proxy server, an internal yum server, and a RHN client for each OS variant (and architecture) you intend to support "offline". E.g. supporting 6Server, 6Client, and 6Workstation for i686 and x86_64 would normally require 6 RHN clients, but only three RHN clients would be necessary for RHEL7, as there's no support for i686 architecture

Yum clients can (according to the docs) use nfs resource paths in the baseurl statement, so apache is not strictly necessary on your yum server, but most people do it that way...

Each RHN client will need: local storage to store packages downloaded via reposync (e.g. "reposync -d -g -l -n -t -p /my/storage --repoid=rhel-i686-workstation-optional-6"). You'll need to run "createrepo" on each repository that gets updated, and you'll need to create an rsync service that provides access to each clients' /my/storage volume

Your internal yum server will need a cron script to run rsync against your RHN clients so you can collect all these software channels in one spot.

You'll also need to create custom yum repo files for your client systems (e.g. redhat-6Workstation.repo) that will point to the correct repositories on your yum server.

I'd recommend you NOT run these cron scripts during normal business hours... your sys-admins will want a stable copy so they can clone things for other offline networks.

If you're clever, you can convince one RHN client system to impersonate the different OS variants, reducing the number of systems you need to deploy.

You'll also most likely want to run "hardlink" on your yum server pretty regularly as there's lots of redundant packages across each OS variant.

[Dec 23, 2020] How do you guys handle Linux Updates-Patches

Dec 23, 2020 |

Do you use scripts? Configuration Management? Satellite/Spacewalk? Or do you do you practice immutable infrastructure, and simply replace old instances with new ones that have updates pre-baked (update during provisioning)?
I also see the likes of Katello and RH CloudForms System Engine from a Google search.
On top of that, what is your methodology of determining what gets updated and what doesn't? 0 0 0 0 Goals for 2018:
Certs: RHCSA, LFCS: Ubuntu, CNCF CKA, CNCF CKAD | AWS Certified DevOps Engineer, AWS Solutions Architect Pro, AWS Certified Security Specialist, GCP Professional Cloud Architect
Learn: Terraform, Kubernetes, Prometheus & Golang | Improve: Docker , Python Programming
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[Jun 12, 2021] Seven-year-old make-me-root bug in Linux service polkit patched Published on Jun 12, 2021 |

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