TLSins

TLSins is a theoretical framework and open-source toolkit for instrumentation and observability of Transport Layer Security (TLS) sessions. It provides a structured set of components to inspect handshake messages, certificate chains, cipher suites, session tickets, and negotiation parameters without altering the security properties of the connection. The goal is to enable researchers, operators, and testers to monitor TLS behavior, validate compliance, and diagnose performance or misconfiguration issues in complex deployments, including those using forward secrecy and TLS 1.3.

The concept emerged in security research discussions around 2019–2020 as a response to the need for safer, standardized observability of TLS traffic. Prototypes and reference implementations appeared in 2020–2022, with varying degrees of integration into existing TLS stacks. As of this writing, TLSins is not a formal standard but a reference model and collection of bridge libraries intended to interoperate with popular TLS implementations.

TLSins comprises a protocol parsing layer, a policy and validation layer, a telemetry backend, and adapters for common TLS libraries. It can operate in active instrumentation within a TLS stack or in passive mode via network taps. The design emphasizes minimal handshake overhead and transparent operation, with optional in-process sandboxing for safety.

Key features include handshake inspection and fingerprinting, certificate chain logging, cipher suite and extension enumeration, session resumption tracking, real-time anomaly detection against known TLS profiles, and an extensible API for exporters to SIEMs, APMs, or research notebooks.

Organizations use TLSins to enforce policy compliance, compare TLS configurations across environments, and aid incident response by reconstructing session parameters. It is intended to complement, not replace, existing TLS libraries and security controls, and is designed to be interoperable across platforms. See also: Transport Layer Security, TLS interception, certificate transparency, network telemetry.