From 48348fc3b4455df8112d4e1b6de5b4f0779be875 Mon Sep 17 00:00:00 2001 From: Damien Miller Date: Sun, 22 Apr 2012 11:08:30 +1000 Subject: - djm@cvs.openbsd.org 2012/03/28 07:23:22 [PROTOCOL.certkeys] explain certificate extensions/crit split rationale. Mention requirement that each appear at most once per cert. --- PROTOCOL.certkeys | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) (limited to 'PROTOCOL.certkeys') diff --git a/PROTOCOL.certkeys b/PROTOCOL.certkeys index 2f976498..c9859109 100644 --- a/PROTOCOL.certkeys +++ b/PROTOCOL.certkeys @@ -162,6 +162,13 @@ extensions is a set of zero or more optional extensions. These extensions are not critical, and an implementation that encounters one that it does not recognise may safely ignore it. +Generally, critical options are used to control features that restrict +access where extensions are used to enable features that grant access. +This ensures that certificates containing unknown restrictions do not +inadvertently grant access while allowing new protocol features to be +enabled via extensions without breaking certificates' backwards +compatibility. + The reserved field is currently unused and is ignored in this version of the protocol. @@ -189,7 +196,7 @@ is a sequence of zero or more tuples: string data Options must be lexically ordered by "name" if they appear in the -sequence. +sequence. Each named option may only appear once in a certificate. The name field identifies the option and the data field encodes option-specific information (see below). All options are @@ -220,7 +227,9 @@ Extensions The extensions section of the certificate specifies zero or more non-critical certificate extensions. The encoding and ordering of -extensions in this field is identical to that of the critical options. +extensions in this field is identical to that of the critical options, +as is the requirement that each name appear only once. + If an implementation does not recognise an extension, then it should ignore it. @@ -253,4 +262,4 @@ permit-user-rc empty Flag indicating that execution of of this script will not be permitted if this option is not present. -$OpenBSD: PROTOCOL.certkeys,v 1.8 2010/08/31 11:54:45 djm Exp $ +$OpenBSD: PROTOCOL.certkeys,v 1.9 2012/03/28 07:23:22 djm Exp $ -- cgit v1.2.1