[TLS] [Errata Verified] RFC9257 (7643)

RFC Errata System <rfc-editor@rfc-editor.org> Fri, 14 November 2025 15:45 UTC

To: hvn@radiatorsoftware.com, housley@vigilsec.com, jonathan.hoyland@gmail.com, mohit@iki.fi, caw@heapingbits.net
From: RFC Errata System <rfc-editor@rfc-editor.org>
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Date: Fri, 14 Nov 2025 07:45:42 -0800
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Subject: [TLS] [Errata Verified] RFC9257 (7643)
Archived-At: <https://mailarchive.ietf.org/arch/msg/tls/dJmCbDKzB93zE0_7dMy9_rZg6b4>

The following errata report has been verified for RFC9257,
"Guidance for External Pre-Shared Key (PSK) Usage in TLS".

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You may review the report below and at:
https://www.rfc-editor.org/errata/eid7643

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Status: Verified
Type: Technical

Reported by: Heikki Vatiainen <hvn@radiatorsoftware.com>
Date Reported: 2023-09-17
Verified by: Paul Wouters (IESG)

Section: 6.1. Stack Interface

Original Text
-------------
* OpenSSL and BoringSSL: Applications can specify support for
external PSKs via distinct ciphersuites in TLS 1.2 and below.
Also, they can then configure callbacks that are invoked for PSK
selection during the handshake. These callbacks must provide a
PSK identity and key. The exact format of the callback depends on
the negotiated TLS protocol version, with new callback functions
added specifically to OpenSSL for TLS 1.3 [RFC8446] PSK support.
The PSK length is validated to be between 1-256 bytes (inclusive).
The PSK identity may be up to 128 bytes long.

Corrected Text
--------------
* OpenSSL and BoringSSL: Applications can specify support for
external PSKs via distinct ciphersuites in TLS 1.2 and below.
Also, they can then configure callbacks that are invoked for PSK
selection during the handshake. These callbacks must provide a
PSK identity and key. The exact format of the callback depends on
the negotiated TLS protocol version, with new callback functions
added specifically to OpenSSL for TLS 1.3 [RFC8446] PSK support.
The PSK length is validated to be between 1-256 bytes (inclusive).
The PSK identity may be up to 128 bytes long. OpenSSL 3.0
increased PSK maximum length to 512 bytes and PSK identity maximum
length to 256 bytes to match existing implementations and
specifications.

Notes
-----
OpenSSL PSK length and PSK identity length were increased to 256 and 512 octets, respectively, for OpenSSL 3.0. There appear to be implementations and specifications that require these longer lengths. See here for more information:
https://github.com/openssl/openssl/pull/12777
https://github.com/openssl/openssl/pull/12771

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RFC9257 (draft-ietf-tls-external-psk-guidance-06)
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Title : Guidance for External Pre-Shared Key (PSK) Usage in TLS
Publication Date : July 2022
Author(s) : R. Housley, J. Hoyland, M. Sethi, C. A. Wood
Category : INFORMATIONAL
Source : Transport Layer Security
Stream : IETF
Verifying Party : IESG

[TLS] [Errata Verified] RFC9257 (7643) RFC Errata System