Frequently Asked Question about TLS and Cipher Suite configuration

[SecPmCj]

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What versions of Windows support TLS 1.3?

Starting with Windows Server 2022, TLS 1.3 is supported by default in all versions.  The protocol is not available in down level OS versions.

What Linux distros will not support TLS 1.3?

Most modern Linux distributions have support for TLS 1.3. TLS 1.3 is a significant improvement in security and performance over earlier versions of TLS, and it's widely adopted in modern web servers and clients. However, the specific versions of Linux and software components that support TLS 1.3 can vary, and it's essential to keep your software up-to-date to benefit from the latest security features.

To ensure TLS 1.3 support, consider the following factors:

1. **Linux Kernel:** Most modern Linux kernels have support for TLS 1.3. Kernel support is essential for low-level network encryption. Ensure that your Linux distribution is running a reasonably recent kernel.
2. **OpenSSL or OpenSSL-Compatible Libraries:** TLS 1.3 support is primarily dependent on the version of OpenSSL or other TLS libraries in use. OpenSSL 1.1.1 and later versions generally provide support for TLS 1.3. However, the specific version available may depend on your Linux distribution and the software you're using.
3. **Web Servers and Applications:** The web servers and applications you run on your Linux system need to be configured to enable TLS 1.3. Popular web servers like Apache, Nginx, and others have been updated to support TLS 1.3 in newer versions. Ensure that you are using an updated version of your web server software and have TLS 1.3 enabled in its configuration.
4. **Client Software:** If you are using Linux as a client to connect to servers over TLS, your client software (e.g., web browsers, email clients) should support TLS 1.3. Most modern web browsers and email clients on Linux have added support for TLS 1.3.
5. **Distribution Updates:** Regularly update your Linux distribution to receive security updates and new software versions, including those with TLS 1.3 support. Each Linux distribution may have different release schedules and package versions.

Since the state of software support can change over time, it's crucial to check the specific versions and configurations of the software components you are using on your Linux system to determine their TLS 1.3 compatibility. Generally, using up-to-date software and keeping your Linux system patched with the latest security updates will ensure that you have the best support for TLS 1.3 and other security features.

How do remove my dependency on Legacy TLS encryption?

At high level, resolving legacy TLS encryption issues requires understanding your TLS 1.0 and TLS 1.1 dependencies, upgrading to TLS 1.2+ compliant OS versions, updating applications and testing.

1. Given the length of time TLS 1.0 has been supported by the software industry, it is highly recommended that any TLS 1.0 deprecation plan include the following:
2. Code analysis to find/fix hardcoded instances of TLS 1.0 or older security protocols.
3. Network endpoint scanning and traffic analysis to identify operating systems using TLS 1.0 or older protocols.
4. Full regression testing through your entire application stack with TLS 1.0 disabled.
5. Migration of legacy operating systems and development libraries/frameworks to versions capable of negotiating TLS 1.2 by default.
6. Compatibility testing across operating systems used by your business to identify any TLS 1.2 support issues.
7. Coordination with your own business partners and customers to notify them of your move to deprecate TLS 1.0.
8. Understanding which clients may no longer be able to connect to your servers once TLS 1.0 is disabled.

How do I configure protocols and cipher suites for Apache?

Configuring cipher suites and protocols for the Apache web server involves modifying the server's SSL/TLS settings in its configuration file. This process can help you enhance the security and compatibility of your web server. Here are the steps to configure cipher suites and protocols for Apache:

1. **Backup Configuration Files:**

 Before making any changes, it's essential to create backups of your Apache configuration files to ensure you can revert if something goes wrong. Common configuration files include `httpd.conf` or `apache2.conf`, and the SSL/TLS configuration file, often named something like `ssl.conf`.

2. **Edit SSL/TLS Configuration:**

Open the SSL/TLS configuration file for your Apache server using a text editor. The location of this file can vary depending on your Linux distribution and Apache version. Common locations include `/etc/httpd/conf.d/ssl.conf`, `/etc/apache2/sites-available/default-ssl.conf`, or similar. You may need root or superuser privileges to edit this file.

Example command to open the file in a text editor:

```

sudo nano /etc/httpd/conf.d/ssl.conf

```

3. **Specify Protocol Versions:**

To configure the allowed SSL/TLS protocols, you can use the `SSLProtocol` directive. For example, to allow only TLS 1.2 and TLS 1.3, you can add the following line to your configuration:

```

SSLProtocol -all +TLSv1.2 +TLSv1.3

```

This configuration disables SSL (SSLv2 and SSLv3) and enables TLS 1.2 and TLS 1.3.

4. **Specify Cipher Suites:**

To configure the allowed cipher suites, use the `SSLCipherSuite` directive. You can specify a list of cipher suites that you want to enable. Ensure that you use secure and modern cipher suites. For example:

```

SSLCipherSuite TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256

```

This example includes cipher suites that offer strong security and forward secrecy.

5. **Save and Close the Configuration File**

Save your changes and exit the text editor.

6. **Test Configuration**

Before you restart Apache, it's a good practice to test your configuration for syntax errors. You can use the following command:

```

apachectl configtest

```

If you receive a "Syntax OK" message, your configuration is valid.

7. **Restart Apache:**

Finally, restart the Apache web server to apply the changes:

```

sudo systemctl restart apache2   # On systemd-based systems

```

```

sudo service apache2 restart     # On non-systemd systems

```

Your Apache web server should now be configured to use the specified SSL/TLS protocols and cipher suites. Remember that keeping your SSL/TLS configuration up to date and secure is crucial for the overall security of your web server. Be sure to monitor security advisories and best practices for SSL/TLS configuration regularly.

How do I configure protocols and cipher suites for nginx?

To configure cipher suites and protocols for the Nginx web server, you'll need to modify its SSL/TLS settings in the server block configuration. This process allows you to enhance the security and compatibility of your web server. Here are the steps to configure cipher suites and protocols for Nginx:

1. **Backup Configuration Files:**

Before making any changes, create backups of your Nginx configuration files to ensure you can revert if needed. Common configuration files include `nginx.conf`, `sites-available/default`, or a custom server block file.

2. **Edit the Nginx Configuration File:**

Open the Nginx configuration file in a text editor. The location of the main configuration file varies depending on your Linux distribution and Nginx version. Common locations include `/etc/nginx/nginx.conf`, `/etc/nginx/sites-available/default`, or a custom configuration file within `/etc/nginx/conf.d/`.

Example command to open the file in a text editor:

```bash

sudo nano /etc/nginx/nginx.conf

```

3. **Specify Protocol Versions:**

To configure the allowed SSL/TLS protocols, you can use the `ssl_protocols` directive in your `server` block or `http` block. For example, to allow only TLS 1.2 and TLS 1.3, add the following line:

```nginx

ssl_protocols TLSv1.2 TLSv1.3;

```

This configuration disables SSL (SSLv2 and SSLv3) and enables TLS 1.2 and TLS 1.3.

4. **Specify Cipher Suites:**

To configure the allowed cipher suites, use the `ssl_ciphers` directive. Specify a list of cipher suites that you want to enable. Ensure that you use secure and modern cipher suites. For example:

```nginx

ssl_ciphers 'TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA256';

```

This example includes cipher suites that offer strong security and forward secrecy.

5. **Save and Close the Configuration File:**

Save your changes and exit the text editor.

6. **Test Configuration:**

Before you reload Nginx to apply the changes, test your configuration for syntax errors:

```bash

sudo nginx -t

```

If you receive a "syntax is okay" message, your configuration is valid.

7. **Reload Nginx:**

Finally, reload Nginx to apply the new SSL/TLS settings:

```bash

sudo systemctl reload nginx   # On systemd-based systems

```

```bash

sudo service nginx reload     # On non-systemd systems

```

Your Nginx web server should now be configured to use the specified SSL/TLS protocols and cipher suites. Ensure that you stay updated with best practices and security advisories for SSL/TLS configurations to maintain the security of your web server.

 

What open-source tools can be used to test client connections?

There are several open-source tools available to test client connections for TLS (Transport Layer Security) connections, either for troubleshooting or security auditing purposes. Here are some popular ones:

Nmap

Nmap, a powerful network scanning tool, can be used to test TLS/SSL configurations and identify supported cipher suites on a server. Here are a couple of ways you can utilize Nmap for testing TLS client connections:

• Using the ssl-enum-ciphers Script:
• Nmap includes a script called ssl-enum-ciphers, which assesses the cipher suites supported by a server and rates them based on cryptographic strength.
• It performs multiple connections using SSLv3, TLS 1.1, and TLS 1.2.
• To check the supported ciphers on a specific server (e.g., Bing), run the following command:
  nmap --script ssl-enum-ciphers -p 443 www.bing.com
• The output will provide information about the supported ciphers and their strengths123.

Checking for Weak Ciphers:

• If you specifically want to identify weak ciphers, you can use the following command:
  nmap --script ssl-enum-ciphers -p 443 yoursite.com | grep weak
• This command will highlight any weak ciphers detected during the scan4

Remember that Nmap is a versatile tool, and its ssl-enum-ciphers script can help you assess the security of your TLS connections. 

SSLyze

SSLyze is a powerful Python tool designed to analyze the SSL configuration of a server by connecting to it. It helps organizations and testers identify misconfigurations affecting their SSL servers. Here’s how you can use SSLyze to assess TLS connections:

Basic Scan with sslyze:

• To perform a basic scan of a website’s HTTPS configuration, run the following command, replacing example.com with the domain you want to scan:

sslyze --regular example.com

This command will display information about the protocol version, cipher suites, certificate chain, and more.

Specific Scan Commands:

• You can use various scan commands to test specific aspects of TLS connections:
  • --sslv3: Test for SSL 3.0 support.
  • --tlsv1: Test for TLS 1.0 support.
  • --early_data: Test for TLS 1.3 early data support.
  • --sslv2: Test for SSL 2.0 support.

Online SSL Scan:

If you prefer an online approach, you can use SSLyze to test any SSL/TLS-enabled service on any port. It checks for weak ciphers and known cryptographic vulnerabilities (such as Heartbleed). 

Remember to adjust the scan parameters based on your specific requirements.

testssl.sh

testssl.sh is a powerful open-source command-line tool that allows you to check TLS/SSL encryption on various services. Here are some features and instructions for using it:

1. Installation:
   • You can install testssl.sh by cloning its Git repository:
     • git clone --depth 1 https://github.com/drwetter/testssl.sh.git
       cd testssl.sh
   • Make sure you have bash (usually preinstalled on most Linux distributions) and a newer version of OpenSSL (1.1.1 recommended) for effective usage.
2. Basic Usage:
   • To test a website’s HTTPS configuration, simply run:
     • ./testssl.sh https://www.bing.com/
   • To test STARTTLS-enabled protocols (e.g., SMTP, FTP, IMAP, etc.), use the -t option:
     • ./testssl.sh -t smtp https://bing.com:25
3. Additional Options:
   • Parallel Testing:
     • By default, mass tests are done in serial mode. To enable parallel testing, use the --parallel flag: 
       • ./testssl.sh --parallel
   • Custom OpenSSL Path:
     • If you want to use an alternative OpenSSL program, specify its path using the --openssl flag:
       • ./testssl.sh --parallel --sneaky --openssl /path/to/your/openssl
   • Logging:
     • To keep logs for later analysis, use the --log (store log file in the current directory) or --logfile (specify log file location) options:
       • ./testssl.sh --parallel --sneaky --logging
   • Disable DNS Lookup:
     • To speed up tests, disable DNS lookup using the -n flag:
       • ./testssl.sh -n --parallel --sneaky --logging
4. Single Checks:
   • You can run specific checks for protocols, server defaults, headers, vulnerabilities, and more. For example:
     • To check each local cipher remotely, use the -e flag.
     • To omit some checks and make the test faster, include the --fast flag.
     • To test TLS/SSL protocols (including SPDY/HTTP2), use the -p option.
     • To view the server’s default picks and certificate, use the -S option.
     • To see the server’s preferred protocol and cipher, use the -P flag.

Remember that testssl.sh provides comprehensive testing capabilities, including support for mass testing and logging.

TLS-Attacker

TLS-Attacker is a powerful Java-based framework designed for analyzing TLS libraries. It serves as both a manual testing tool for TLS clients and servers and a software library for more advanced tools. Here’s how you can use it:

1. Compilation and Installation:
   • To get started, ensure you have Java and Maven installed. On Ubuntu, you can install Maven using:
     • sudo apt-get install maven
   • TLS-Attacker currently requires Java JDK 11 to run. Once you have the correct Java version, clone the TLS-Attacker repository:
     • git clone https://github.com/tls-attacker/TLS-Attacker.git
     • cd TLS-Attacker
     • mvn clean install
   • The resulting JAR files will be placed in the “apps” folder. If you want to use TLS-Attacker as a dependency, include it in your pom.xml like this:
     • <dependency><groupId>de.rub.nds.tls.attacker</groupId><artifactId>tls-attacker</artifactId><version>5.2.1</version><type>pom</type></dependency>
2. Running TLS-Attacker:
   • You can run TLS-Attacker as a client or server:
     • As a client:
       • cd apps
       • java -jar TLS-Client.jar -connect [host:port]
     • As a server:
       • java -jar TLS-Server.jar -port [port]
   • TLS-Attacker also ships with example attacks on TLS, demonstrating how easy it is to implement attacks using the framework:
     • java -jar Attacks.jar [Attack] -connect [host:port]
   • Although the example applications are powerful, TLS-Attacker truly shines when used as a programming library.
3. Customization and Testing:
   • You can define custom TLS protocol flows and test them against your TLS library.
   • TLS-Attacker allows you to send arbitrary protocol messages in any order to the TLS peer and modify them using a provided interface.

Remember that TLS-Attacker is primarily a research tool intended for TLS developers and pentesters. It doesn’t have a GUI or green/red lights—just raw power for analyzing TLS connections!

ssldump

ssldump is a versatile SSL/TLS network protocol analyzer that can help you examine, decrypt, and decode SSL-encrypted packet streams. Here’s how you can use it for testing TLS connections:

1. Capture the Target Traffic:
   • First, capture a packet trace containing the SSL traffic you want to examine. You can use the tcpdump utility to capture the traffic.
   • To write the captured packets to a file for examination with ssldump, use the -w option followed by the name of the file where the data should be stored.
   • Specify the interface or VLAN from which traffic is to be captured using the -i option.
   • Use appropriate tcpdump filters to include only the traffic you want to examine.
2. Examine the SSL Handshake and Record Messages:
   • When you run ssldump on the captured data, it identifies TCP connections and interprets them as SSL/TLS traffic.
   • It decodes SSL/TLS records and displays them in text format.
   • You’ll see details about the SSL handshake, including the key exchange.
   • Example command:
     • ssldump -i en0 -w captured_traffic.pcap
3. Decrypt Application Data (If Possible):
   • If you have the private key used to encrypt the connections, ssldump may also decrypt the connections and display the application data traffic.
   • Keep in mind that ssldump cannot decrypt traffic for which the handshake (including the key exchange) was not seen during the capture.

Remember to follow best practices when capturing SSL conversations for examination. For more information, refer to the official documentation.

sslscan

sslscan is a handy open-source tool that tests SSL/TLS-enabled services to discover supported cipher suites. It’s particularly useful for determining whether your configuration has enabled or disabled specific ciphers or TLS versions. Here’s how you can use it:

1. Installation:
   • If you’re using Ubuntu, you can install sslscan using the following command:
     sudo apt-get install sslscan
2. Basic Usage:
   • To scan a server and list the supported algorithms and protocols, simply point sslscan at the server you want to test. For example:
     • sslscan example.com
   • The output will highlight various aspects, including SSLv2 and SSLv3 ciphers, CBC ciphers on SSLv3 (to detect POODLE vulnerability), 3DES and RC4 ciphers, and more.
3. Additional Options:
   • You can customize the scan by using various options:
     • --targets=<file>: Specify a file containing a list of hosts to check.
     • --show-certificate: Display certificate information.
     • --failed: Show rejected ciphers.

Remember that sslscan provides valuable insights into your SSL/TLS configuration.

curl

You can use curl to test TLS connections. Here are some useful commands and tips:

1. Testing Different TLS Versions:
   • To test different TLS versions, you can use the following options with curl:
     • --tlsv1.0: Test TLS 1.0
     • --tlsv1.1: Test TLS 1.1
     • --tlsv1.2: Test TLS 1.2
     • --tlsv1.3: Test TLS 1.3
   • For example, to test TLS 1.2, use:
     • curl --tlsv1.2 https://example.com
   • Replace example.com with the URL you want to test1.
2. Debugging SSL Handshake:
   • While curl can provide some information, openssl is a better tool for checking and debugging SSL.
   • To troubleshoot client certificate negotiation, use:
     • openssl s_client -connect www.example.com:443 -prexit
   • This command will show acceptable client certificate CA names and a list of CA certificates from the server2.
3. Checking Certificate Information:
   • To see certificate information, use:
     • curl -iv https://example.com
   • However, for detailed TLS handshake troubleshooting, prefer openssl s_client instead of curl. Use options like -msg, -debug, and -status for more insights3.

Remember that curl can be handy for quick checks, but for in-depth analysis, openssl provides more comprehensive details about SSL/TLS connections.

OpenSSL

OpenSSL is a versatile tool that allows you to test and verify TLS/SSL connections. Here are some useful commands and examples:

1. Testing TLS Versions:
   • To specify the TLS version for testing, use the appropriate flag with openssl s_client. For instance:
     • To test TLS 1.3, run:
       • openssl s_client -connect example.com:443 -tls1_3
     • Other supported SSL and TLS version flags include -tls1_2, -tls1_1, -tls1, -ssl2, and -ssl31.
2. Checking Certificate Information:
   • To see detailed certificate information, use:
     • openssl s_client -connect your.domain.io:443
   • For more in-depth analysis, consider using openssl instead of curl. Options like -msg, -debug, and -status provide additional insights2.
3. Upgrading Plain Text Connections:
   • You can upgrade a plain text connection to an encrypted (TLS or SSL) connection using the -starttls option. For example:
     • openssl s_client -connect mail.example.com:25 -starttls smtp
   • This command checks and verifies secure connections, making it a valuable diagnostic tool for SSL servers3.
   • Remember, openssl s_client is your go-to for testing and diagnosing SSL/TLS connections. 

Can you use WireShark to inspect the TLS connections? 

Most modern Linux distributions have support for TLS 1.3. TLS 1.3 is a significant improvement in security and performance over earlier versions of TLS, and it's widely adopted in modern web servers and clients. However, the specific versions of Linux and software

1. Capture the Traffic:
   • Start Wireshark and select the network interface you want to capture traffic from.
   • Click the Start button (usually a green shark fin icon) to begin capturing packets.
   • Browse to a website or perform any action that involves TLS communication (e.g., visiting an HTTPS website).
2. Filter for TLS Traffic:
   • In the packet list, you’ll see various packets. To focus on TLS traffic, apply a display filter:
     • Click on the Display Filter field (located at the top of the Wireshark window).
     • Type tls or ssl and press Enter.
     • Wireshark will now display only packets related to TLS/SSL.
3. Inspect TLS Handshake and Records:
   • Look for packets with the TLS Handshake Protocol (such as Client Hello, Server Hello, Certificate Exchange, Key Exchange, and Finished messages).
   • Expand these packets to view details about the handshake process, including supported cipher suites, certificate information, and key exchange.
   • You can also examine the Application Data packets to see encrypted data being exchanged after the handshake.
4. Decryption (Optional):
   • If you have access to the pre-master secret or an RSA private key, you can decrypt the TLS traffic:
     • Go to Edit → Preferences.
     • Open the Protocols tree and select TLS.
     • Configure the (Pre)-Master-Secret log filename or provide the RSA private key.

Wireshark will use this information to decrypt the TLS packets.

Tool references

• gnutls-cli(1) - Linux manual page (man7.org)
• Testing TLS/SSL configuration using Nmap - Web Penetration Testing with Kali Linux - Third Edition [...
• Testing SSL ports using nmap and check for weak ciphers | Global Security and Marketing Solutions (g...
• How to use sslyze to assess your web server HTTPS TLS? – Full Security Engineer
• Overview of packet tracing with the ssldump utility (f5.com)
• Curl – Test TLS and HTTP versions – Kerry Cordero
• openssl s_client commands and examples - Mister PKI
• TLS - Wireshark Wiki
• GitHub - drwetter/testssl.sh: Testing TLS/SSL encryption anywhere on any port
• GitHub - tls-attacker/TLS-Attacker: TLS-Attacker is a Java-based framework for analyzing TLS librari...
• GitHub - rbsec/sslscan: sslscan tests SSL/TLS enabled services to discover supported cipher suites

Other references

• Restricting TLS 1.2 Ciphersuites in Windows using PowerShell
• Solving the TLS 1.0 Problem, 2nd Edition
• Support for legacy TLS protocols and cipher suites in Azure Offerings