Security

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How to disable vulnerable ciphers and encryption modes in Rocky Linux 8 to mitigate Terrapin Attack (CVE-2023-48795)

For more information on the Terrapin Attack (CVE-2023-48795), do take a look at Terrapin Attack (CVE-2023-48795): SSH Protocol Impacted.

As mentioned, in the blog entry, Terrapin Attack (CVE-2023-48795): SSH Protocol Impacted, the attack is possible only if you use vulnerable ciphers and encryption modes: ChaCha20-Poly1305, CTR-EtM, CBC-EtM. Note that the cyphers and the encryption modes themselves are not vulnerable, but their input (sequence number) can be manipulated by the attacker.

The mitigation is similar to How to disable CBC Mode Ciphers in RHEL 8 or Rocky Linux 8 except that you have to remove the “chacha20-poly1305@openssh.com” besides the CBC Mode Ciphers.

Step 1: Edit /etc/sysconfig/sshd and uncomment CRYPTO_POLICY line:

CRYPTO_POLICY=

Edit /etc/ssh/sshd_config file. Add Ciphers, MACs and KexAlgorithms have been added

KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256

Ciphers aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr

MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com

After making changes to the configuration file, you may want to do a sanity check on the configuration file

# sshd -t

Restart sshd services

# systemctl restart sshd

To test if weak CBC Ciphers and  ChaCha20-Poly1305 are enabled

$ ssh -vv -oCiphers=chacha20-poly1305@openssh.com,3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc IP-Address-of-your-Server

You should receive a similar message

Unable to negotiate with 172.21.33.11 port 22: no matching cipher found. Their offer: aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr

To verify that the Terrapin Attack Vulnerability is mitigated, take a look at Vulnerability Scanner. Pre-built binaries for all major platforms and the source code are available on GitHub.

./Terrapin_Scanner_Linux_amd64 -connect XXX.XXX.XXX.XXX

If you are not vulnerable, you may have an output like this.

References:

  1. Terrapin Attack (CVE-2023-48795): SSH Protocol Impacted
  2. Terrapin Attack
  3. Terrapin (CVE-2023-48795): New Attack Impacts the SSH Protocol
  4. SSH protocol flaw – Terrapin Attack CVE-2023-48795: All you need to know
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Terrapin Attack (CVE-2023-48795): SSH Protocol Impacted

What is Terrapin Attack (CVE-2023-48795)?

Researchers from Ruhr University announced the discovery of new vulnerabilities impacting the SSH Protocol. Detailed Information of the Terrapin Attack can be found at Terrapin Attack.

According to FOSSA Terrapin (CVE-2023-48795): New Attack Impacts the SSH Protocol

Terrapin is a man-in-the-middle attack; the flaw allows an attacker to corrupt data being transmitted. This can result in a loss of information or bypass critical security controls such as keystroke timing protections or SHA-2 cryptographic hash requirements, allowing the threat actor to downgrade to SHA-1. Doing so opens up the possibility of other attacks on downstream applications, components, or environments that use SSH. ​​These associated vulnerabilities have been assigned CVE-2023-46445 (Rogue Extension Negotiation Attack in AsyncSSH) and CVE-2023-46446 (Rogue Session Attack in AsyncSSH).

Terrapin (CVE-2023-48795): New Attack Impacts the SSH Protocol

How do I know that I am vulnerable?

The attack is possible only if you use vulnerable ciphers and encryption modes: ChaCha20-Poly1305, CTR-EtM, CBC-EtM. Note that the cyphers and the encryption modes themselves are not vulnerable, but their input (sequence number) can be manipulated by the attacker.

How do I mitigate the attack?

To mitigate the attack, either you upgrade OpenSSH to their latest version 9.6 or disable the affected ciphers and encryption modes.

Vulnerability Impacts

According to FOSSA Terrapin (CVE-2023-48795): New Attack Impacts the SSH Protocol, their assessment of the Attack are:

  • Limited Impacts: Terrapin can delete consecutive portions of encrypted messages, which in isolation will typically result in a stuck connection. Some of the most serious impacts identified are in downstream applications implementing SSH, such as AsyncSSH. An attacker may be able to disable certain keylogging obfuscation features, enabling them to conduct a keylogging attack; or, worst case, a threat actor can sign a victim’s client into another account without the victim noticing, enabling phishing attacks.
  • Difficult to Expliot: An active man-in-the-middle attacker and specific encryption modes are prerequisites for the exploit. Intercepting SSH traffic requires a detailed understanding of a target’s environment, limiting real-world applicability.

How do I check?

You may want to explore the vulnerablilty tool published by the Ruhr University Researchers:

For more information, do take look at Vulnerability Scanner. Pre-built binaries for all major platforms and the source code are available on GitHub.

Usage is very simple, after downloading the relevant binary, just use the command

./Terrapin_Scanner_Linux_amd64 -connect XXX.XXX.XXX.XXX

If you are not vulnerable, you may have a output something like this.

If you are vulnerable, the scanner will flag as expected.

References:

  1. Terrapin Attack
  2. Terrapin (CVE-2023-48795): New Attack Impacts the SSH Protocol
  3. SSH protocol flaw – Terrapin Attack CVE-2023-48795: All you need to know
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Using the Host’s FirewallD as the Main Firewall to Secure Docker

Found a rare article How to Secure a Docker Host Using Firewalld that teaches how to address the issue when that docker bypasses the FirewallD rules.

According to the Article, the goal of the Configuration is to

  • The firewall rules should count for whole host system – so including Docker containers with port mappings
  • A Docker container should be accessible from the internet if and only if the host port used in Docker container port mapping is allowed in the firewall
  • The approach should not break container networking

Do read up and you will be glad that this article was written for Administrators like us. Another Reference you may want to consider reading is Why Docker and Firewall don’t get along with each other!

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Automating Security Patch Logs and MS-Team Notifications with Ansible on Rocky Linux 8

If you have read the blog entry Using Ansible to automate Security Patch on Rocky Linux 8, you may want to consider capturing the logs and send notification to MS-Team if you are using that as a Communication Channel. This is a follow-up to that blog.

Please look at Part 1: Using Ansible to automate Security Patch on Rocky Linux 8

Writing logs (Option 1: Ansible Command used if just checking)

Recall that in Option 1: Ansible Command used if just checking, Part 1a & Part 1b, you can consider writing to logs in /var/log/ansible_logs

- name: Create a directory if it does not exist
  file:
    path: /var/log/ansible_logs
    state: directory
    mode: '0755'
    owner: root
  when:
    - ansible_os_family == "RedHat"
    - ansible_distribution_major_version == "8"



- name: Copy Results to file
  ansible.builtin.copy:
    content: "{{ register_output_security.results | map(attribute='name') | list }}"
    dest: /var/log/ansible_logs/patch-list_{{ansible_date_time.date}}.log
  changed_when: false
  when:
    - ansible_os_family == "RedHat"
    - ansible_distribution_major_version == "8"

Notification (Option 1: Ansible Command used if just checking)

You can write to MS Team to provide a short notification to let the Engineers knows that the logs has been written to /var/log/ansible_logs

- name: Send a notification to MS-Teams that Test Run (No Patching) is completed
  run_once: true
  uri:
    url: "https://xxxxxxx.webhook.office.com/webhookb2/xxxxxxxxxxxxxxxxxxxxxxxxx"
    method: POST
    body_format: json
    body:
      title: "Test Patch Run on {{ansible_date_time.date}}"
      text: "Test Run only. System has not been Patched Yet. Logs saved at: /var/log/ansible_logs/patch-list_{{ansible_date_time.date}}.log"
  when:
    - register_update_success is defined
    - ext_permit_flag == "no"

Writing to MS-Team to capture the success Or failure of the Update (Option 2: Ansible Command used when ready for Patching)

- name: Send a notification to MS-Teams Channel if Upgrade failed
  run_once: true
  uri:
    url: "https://xxxxx.webhook.office.com/webhookb2/xxxxxx"
    method: POST
    body_format: json
    body:
      title: "Patch Run on {{ansible_date_time.date}}"
      text: "Patch Update has Failed"
  when:
    - register_update_success is not defined
    - ext_permit_flag == "yes"



- name: Send a notification to MS-Teams Channel if Upgrade failed
  run_once: true
  uri:
    url: "https://entuedu.webhook.office.com/webhookb2/xxxxxx"
    method: POST
    body_format: json
    body:
      title: "Patch Run on {{ansible_date_time.date}}"
      text: "Patch Update is Successful. Logs saved at: /var/log/ansible_logs/patch-list_{{ansible_date_time.date}}.log"
  when:
    - register_update_success is defined
    - ext_permit_flag == "yes"
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Automating Linux Patching with Ansible: A Simple Guide

If you intend to use Ansible to patch the Server, you may need to use an external variable to decide whether you wish to take a look at the list or actually patch the OS. It consists of 3 parts.

Option 1: Ansible Command used if just checking

$ ansible-playbook security.yml --extra-vars "ext_permit_flag=no"

Part 1a: Get the List of Packages from DNF to be upgraded ONLY using the External Permit Flag = “no”

- name: Get the list of Packages from DNF to be upgraded (ext_permit_flag == "no")
  dnf:
    security: yes
    bugfix: false
    state: latest
    update_cache: yes
    list: updates
    exclude: 'kernel*'
  register: register_output_security
  when:
    - ansible_os_family == "RedHat"
    - ansible_distribution_major_version == "8"
    - ext_permit_flag == "no"

Part 1b: Report the List of Packages from DNF to be upgraded ONLY using the External Permit Flag = “no”

- name: Report the List of Packages from DNF to be upgraded ( ext_permit_flag == no")
  debug:
    msg: "{{ register_output_security.results | map(attribute='name') | list }}"
  when:
    - ansible_os_family == "RedHat"
    - ansible_distribution_major_version == "8"
    - ext_permit_flag == "no"

Option 2: Ansible Command used when ready for Patching

$ ansible-playbook security.yml --extra-vars "ext_permit_flag=yes"

Part 2: Patch all the packages except Kernel

- name: Patch all the packages except Kernel

  dnf:
    name: '*'
    security: yes
    bugfix: false
    state: latest
    update_cache: yes
    update_only: no
    exclude: 'kernel*'
  register: register_update_success
  when:
    - ansible_os_family == "RedHat"
    - ansible_distribution_major_version == "8"
    - ext_permit_flag == "yes"

- name: Print Errors if upgrade failed
  debug:
    msg: "Patch Update Failed"
  when: register_update_success is not defined

Reference:

  1. ansible.builtin.dnf module – Manages packages with the dnf package manager
  2. Automating Linux patching with Ansible
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Microsoft leaks 38TB of private data via unsecured Azure storage

According to the Article “Microsoft leaks 38TB of private data via unsecured Azure storage“

The Microsoft AI research division accidentally leaked dozens of terabytes of sensitive data starting in July 2020 while contributing open-source AI learning models to a public GitHub repository.

Almost three years later, this was discovered by cloud security firm Wiz whose security researchers found that a Microsoft employee inadvertently shared the URL for a misconfigured Azure Blob storage bucket containing the leaked information.

Microsoft linked the data exposure to using an excessively permissive Shared Access Signature (SAS) token, which allowed full control over the shared files. This Azure feature enables data sharing in a manner described by Wiz researchers as challenging to monitor and revoke.

Microsoft leaks 28TB of private data via unsecure Azure storage

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Azure looks like a house of cards collapsing under the weight of exploits and vulnerabilities

Taken from Microsoft comes under blistering criticism for “grossly irresponsible” security – ars Technica

Microsoft has once again come under blistering criticism for the security practices of Azure and its other cloud offerings, with the CEO of security firm Tenable saying Microsoft is “grossly irresponsible” and mired in a “culture of toxic obfuscation.”

The comments from Amit Yoran, chairman and CEO of Tenable, come six days after Sen. Ron Wyden (D-Ore.) blasted Microsoft for what he said were “negligent cybersecurity practices” that enabled hackers backed by the Chinese government to steal hundreds of thousands of emails from cloud customers………. 

Microsoft comes under blistering criticism for “grossly irresponsible” security
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Massive Ransomware Campaign Targeting Unpatched Vmware ESXi Servers

From SINGCERT (https://www.csa.gov.sg/singcert/Alerts/AL-2023-015) dated 04 Feb 2023

There are reports of an ongoing ransomware campaign actively exploiting a vulnerability (CVE-2021-21974) in unpatched VMware ESXi servers.

Successful exploitation of the vulnerability could allow an attacker to perform remote code execution by triggering the heap-overflow issue in OpenSLP service.

The following versions of the products are affected by the aforementioned vulnerability:

•             ESXi versions 7.x earlier than ESXi70U1c-17325551

•             ESXi versions 6.7.x earlier than ESXi670-202102401-SG

•             ESXi versions 6.5.x earlier than ESXi650-202102101-SG

Users and administrators of affected product versions are advised to upgrade to the latest versions immediately. As a precaution, a full system scan should also be performed to detect any signs of compromise. Users and administrators are also advised to assess if the ransomware campaign-targeted port 427 can be disabled without disrupting operations.

Users and administrators may also wish to configure their firewall rules to block any connections to the following IP addresses purportedly carrying out the attacks:

  • 104.152.52[.]55
  • 193.163.125[.]138
  • 43.130.10[.]173
  • 104.152.52[.]0/24

More information can be found at

https://www.vmware.com/security/advisories/VMSA-2021-0002.html

https://www.bleepingcomputer.com/news/security/massive-esxiargs-ransomware-attack-targets-vmware-esxi-servers-worldwide/

https://www.cert.ssi.gouv.fr/alerte/CERTFR-2023-ALE-015/

https://www.csa.gov.sg/singcert/Advisories/ad-2021-009/

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Are Quantum Computers about to Break Online Privacy?

An interesting article from Scientific American. Accorfing to the article

A team of researchers in China has unveiled a technique that—theoretically—could crack the most common methods used to ensure digital privacy, using a rudimentary quantum computer.

The technique worked in a small-scale demonstration, the researchers report, but other specialists are sceptical that the procedure could be scaled up to beat ordinary computers at the task. Still, they warn that the paper, posted late last month on the arXiv repository, is a reminder of the vulnerability of online privacy.

Are Quantum Computers about to Break Online Privacy?
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How to disable CBC Mode Ciphers in RHEL 8 or Rocky Linux 8

This writeup is reference from The Geek Diary

Edit /etc/sysconfig/sshd and uncomment CRYPTO_POLICY line:

CRYPTO_POLICY=

Edit /etc/ssh/sshd_config file. Add Ciphers, MACs and KexAlgorithms have been added

KexAlgorithms curve25519-sha256@libssh.org,ecdh-sha2-nistp521,ecdh-sha2-nistp384,ecdh-sha2-nistp256,diffie-hellman-group-exchange-sha256
Ciphers chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr
MACs hmac-sha2-512-etm@openssh.com,hmac-sha2-256-etm@openssh.com,umac-128-etm@openssh.com,hmac-sha2-512,hmac-sha2-256,umac-128@openssh.com

After making changes to the configuration file, you may want to do a sanity check on the configuration file

# sshd -t

Restart sshd services

# systemctl restart sshd

To test if weak CBC Ciphers are enabled

$ ssh -vv -oCiphers=3des-cbc,aes128-cbc,aes192-cbc,aes256-cbc [youruserid@IP of your Server]

You should receive a aimilar message message 

Unable to negotiate with 172.21.33.13 port 22: no matching cipher found. Their offer: chacha20-poly1305@openssh.com,aes256-gcm@openssh.com,aes128-gcm@openssh.com,aes256-ctr,aes192-ctr,aes128-ctr

References: