Re: Comments on Access Control Model - authentication levels

[Ellen Stokes <stokes@austin.ibm.com>]

There have been many notes on authentication levels.  This response 
addresses those notes.
Below is  the BNF.  In section 4.2.3 I'll incorporate the following points 
below.  In the Security
Considerations section I'll note that ipAddresses are easily forged (as 
stated in requirement
S6), but that it is an accepted though non-secure practice.  Ranges of 
ipaddress are not
supported, but wild-carded dns names are for the most-specific part of the 
name.

I've incorporated authentication definitions from LDAP and X.500 as noted 
below.
Instead of hiding domain and wild-carded domain names with ipAddress, I've 
surface
them as a subject (see below). Only the left-most (most specific) part of 
the dns
name can be wild-carded.
There are 4 authn levels:  non, anonymous, simple, and sasl, and 2 
groupings:  unauthn and
authn.  If authnLevel is omitted in the access control information, 
authnLevel defaults to 'authn'.
authnLevel only makes sense to be applied to certain subjects (see below).
I've omitted(for brevity) in this email the BNF expansion of IPv6address 
(taken from
RFC 2373) since it did not change.


  subject = ([ "authnLevel:" authnLevel ":" ]
                      ( "authzID-" authzID ) /
                      ( "role:" dn ) /
                      ( "group:" dn ) /
                      ( "subtree:" dn ) /
                      "this:" ) /
                ( "ipAddress:" ipAddress ) /
                ( "dns:" [ "*." ] domainname ) /
                "public:"

   authnLevel = "none" /            ; from X.500:  name but no password, 
same as LDAPBIS unauthenticated
                      "anonymous" /   ; from LDAP:  no name and no password
                      "simple" /          ; from LDAP:  name and password
                      sasl /                ; from LDAP
                      "unauthn" /        ; groups none + anonymous
                      "authn"              ; groups simple or sasl, this 
is the default is authnLevel is omitted

   sasl = "sasl:"
                 ("any" /
                 mechanism)

   mechanism = ' sasl mechanism from 4.2 of [LDAPv3]

   ipAddress = IPv6address

   domainname = domaincomponent *( "." domaincomponent )

   domaincomponent = ALPHA [ *61( ALPHA / DIGIT / "-" ) ( ALPHA / DIGIT )]


Ellen



At 01:56 PM 3/29/2001 -0500, Richard V Huber wrote:
> The BNF allows the authentication level to be omitted from ACI.  It
> also allows specification of "none" and "any".
>
> Section 4.2.3 explains the difference between omitting the
> specification and using "any", but it does not explain "none".  I
> suggest "none" be removed from the BNF.
>
> Section 4.2.3 also says "For permission to be granted, the subject must
> have been authenticated to at least the level specified, but that if
> the right is a deny, then everyone is denied access unless they have
> been authenticated to at least the level specified in authnLevel."
>
> I think we will have a lot of problems trying to agree on a
> well-ordering of authnLevels.  I suggest we remove the parts about "at
> least the level specified".  I also feel the part about "... then
> everyone is denied access unless ..." is unclear.
>
> Can we just say "For permission to be granted, the subject must have
> been authenticated to the level specified."
>
> Rick Huber