1804688 - TLS Client ALPN extension ProtocolName entry incorrect length field size and missing length checks

Status: RESOLVED FIXED

(NSS :: Libraries, defect, P1)

Description

[Leander Schwarz]

As specified in RFC7301, Section 3, the ALPN extensions ProtocolNameList entries are of the format:

opaque ProtocolName<1..2^8-1>;

Each entry is preceeded by a 1 byte length field, following the RFC8466, Section 3.4 vector definition.

The current implementation erroneously adds a 2 byte length field for each entry and does not check that the length requirements are met.

Comment 1

[Dennis Jackson]

Attachment: Bug 1804688 - Correct addition of GREASE value to ALPN xtn. r=mt!

A long-standing comment suggested the length field should be 1 byte, but the
code was adding a two-byte length. Inspection showed that the length field
should indeed be two-bytes. This patch corrects the comment and adjusts
the length calculation for the ALPN GREASE value. Tests are included in the
child patch of this revision.

Depends on D161806