Early Draft

• Abstract
• Issues
• Rationale
• Specification
  • Feature identifiers and version flags
  • Configuration interfaces
  • Context interfaces
  • Client interfaces
  • Server interfaces
• Examples
• Implementation
• Acknowledgements
• References
  • IETF RFCs
  • Manuals
• Copyright

This SRFI specifies a set of interfaces to establish secure connections to and communicate with peers using the Transport Layer Security (TLS) protocol. It focuses on simplicity over flexibility and is intended to cover typical use cases.

• Complete the specification

• Rethink whether a socket API is mandatory or not

• Write sample implementations

At least, this SRFI should be able to implement with the following libraries:

• GnuTLS: widely used, used by Guile

• Mbed TLS: designed for embedded systems, used by Gauche

• OpenSSL: widely used, used by Chibi and Chicken

• A TLS implementation on Java VM (javax.net.ssl or Bouncy Castle?)

• A TLS implementation on .NET (System.Net.Security or Bouncy Castle?)

Additionally, the following libraries may be taken into account:

• Amazon s2n-tls

• Apple Secure Transport

• axTLS (no commit to the repository since 2019, safe to drop?)

• BearSSL

• Microsoft Secure Channel

• miTLS by Project Everest

• Mozilla Network Security Services

• wolfSSL

As described in RFC 7258, large-scale surveillance is recognized as a privacy threat nowadays, and the design of internet protocols has been shifting toward encrypted-by-default, using TLS or similar protocols. Thus, a portable API for TLS benefits programmers in writing networking code.

This SRFI is significantly influenced by libtls, a TLS library developed by the OpenBSD community “as a response to the unnecessary challenges other APIs present in order to use them safely.” Furthermore, this SRFI reduces the number of interfaces to provide essential functionalities while supporting various implementations. The interfaces, however, provide room for extensions by future SRFIs and implementations.

This SRFI requires a port I/O API and a socket API that may or may not conform to SRFI 106. It defines feature identifiers (see SRFI 0) and version flags (see SRFI 176).

The words and phrases “an error is signaled”, “an error that satisfies predicate is signaled”, “an error”, “may report a violation of an implementation restriction”, “unspecified”, “must”, “must not”, “shall”, “shall not”, “should”, “should not”, “may”, “required”, “recommended”, and “optional” in this specification are to be interpreted as described in R7RS, section 1.3.2.

Feature identifiers and version flags

Configuration interfaces

Context interfaces

Client interfaces

Server interfaces

??? explanation of how it meets the sample implementation requirement (see process), and the code, if possible, or a link to it.

As mentuioned in the rationale, the specification in this SRFI is significantly influenced by libtls. The author wants to acknowledge the LibreSSL developers.

IETF RFCs

Manuals

Copyright © 2022 Masanori Ogino

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

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