STARTTLSlike

STARTTLSlike is a term used in computer networking to describe a generic class of protocol features that upgrade an initially plaintext connection to a TLS-encrypted channel using a mechanism modeled after the STARTTLS command. In a STARTTLSlike flow, the client and server negotiate whether encryption is supported and, if agreed, perform a TLS handshake over the same TCP connection. Once the handshake completes, subsequent protocol messages are transmitted encrypted, while the earlier plaintext period is not used for data.

Operation typically begins with a capability advertisement or a specific upgrade command. If the endpoint on the other side agrees, the TLS handshake is executed, including certificate verification, support for Server Name Indication (SNI) if applicable, and the selection of session parameters such as TLS version and cipher suites. Some implementations distinguish between opportunistic TLS (encryption is attempted when possible) and mandatory TLS after upgrade (encryption is required for all further communication).

Security considerations for STARTTLSlike mechanisms include the need for proper authentication and validation of certificates, protection against downgrade attacks, and careful error handling to avoid exposing plaintext data after an upgrade attempt. It is important to enforce strict certificate validation and to address potential renegotiation or fallback vulnerabilities.

Variants and usage: The concept is applied or proposed in various protocols that started with plaintext connections, such as email, directory services, or messaging protocols. However, the specific syntax, negotiation, and semantics vary by protocol, and there is no single universal standard universally labeled STARTTLSlike.

See also: STARTTLS, TLS, opportunistic TLS, secure channel negotiation.