- 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.
diff --git a/PROTOCOL.certkeys b/PROTOCOL.certkeys
index 2f97649..c985910 100644
--- a/PROTOCOL.certkeys
+++ b/PROTOCOL.certkeys
@@ -162,6 +162,13 @@
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 @@
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 @@
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 @@
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 $