Definition: testssl is an open-source command-line tool used to test and analyze the SSL/TLS configuration of a server. It checks for various security vulnerabilities and weaknesses in SSL/TLS implementations.

Function: Performs a comprehensive analysis of a server's SSL/TLS configuration, identifying potential security issues and providing detailed reports on the findings.

Components:

 * '''Command-Line Interface''': Allows users to run tests and specify options via command-line arguments.
 * '''Test Modules''': Various modules that check for specific vulnerabilities, such as protocol support, ciphers, and certificate validity.
 * '''Report Generation''': Produces detailed reports of the SSL/TLS analysis, including identified vulnerabilities and suggested mitigations.

Features:

 * '''Protocol Support Check''': Identifies supported SSL/TLS protocols (e.g., SSL 2.0, SSL 3.0, TLS 1.0, TLS 1.2, TLS 1.3).
 * '''Cipher Suite Analysis''': Analyzes supported cipher suites and identifies weak or insecure ciphers.
 * '''Certificate Validation''': Checks the validity, expiration, and trust chain of SSL/TLS certificates.
 * '''Vulnerability Detection''': Detects known vulnerabilities such as Heartbleed, POODLE, and BEAST.
 * '''Compliance Checking''': Verifies compliance with industry standards and best practices (e.g., PCI DSS, HIPAA).

Usage: Used by security professionals to audit SSL/TLS configurations, identify vulnerabilities, and ensure compliance with security standards.

Basic usage to test a server's SSL/TLS configuration:

 ```bash
 testssl.sh https://example.com
 ```
 This command performs a default test on `https://example.com`.

Checking specific protocols and ciphers:

 ```bash
 testssl.sh --protocols --ciphers https://example.com
 ```
 This command checks the supported protocols and ciphers for `https://example.com`.

Generating a detailed report:

 ```bash
 testssl.sh --html https://example.com
 ```
 This command generates an HTML report of the SSL/TLS analysis for `https://example.com`.

Running a compliance check:

 ```bash
 testssl.sh --compliance https://example.com
 ```
 This command checks the SSL/TLS configuration of `https://example.com` for compliance with industry standards.

testssl: An open-source tool for testing and analyzing SSL/TLS configurations of servers. It provides comprehensive checks for protocol support, cipher suite analysis, certificate validation, vulnerability detection, and compliance verification, making it a valuable tool for security professionals to ensure robust SSL/TLS security.