[PROPOSAL] extend UNIX_INFO2 to flag extended access controls (take 2)
[PROPOSAL] extend UNIX_INFO2 to flag extended access controls take 2
Fri, 25 Jan 2008 09:18:31 -0800
This is a modified version of my earlier proposal,
I think that this version clarifies my intent and solves the backwards
compatibility /versioning problem.
1. The Problem
The fundamental problem is that a SMB client that uses UNIX_INFO2
isn't able to use the Permissions field to evaluate access(2) if the
server implements a permissions model that goes beyond the basic Unix
However, even when the server implements an extended permissions
model, most files residing on the server do not have extended
permission applied to them.
If the Unix permissions are the only access control on the file, then
the client can accurately handle access(2) calls without making
further round trips to the server (as long as it is prepared to live
with the race condition).
2. The Proposal
#define UNIX_NO_EXTENDED_PERMISSIONS (1<<63)
The server MAY set the UNIX_NO_EXTENDED_PERMISSIONS bit in the
UNIX_INFO2 Permissions field if this field completely describes the
permissions of the file.
That is, if the server sets this bit, it is indicating to the client
that the file has no access control other than the Unix permissions
bits described in the SNIA QUERY_FILE_UNIX_BASIC documentation.
Existing servers that support the Unix extensions leave the
UNIX_NO_EXTENDED_PERMISSIONS clear, indicating that there MAY be an
extended permissions model in use. In this case, clients SHOULD uses
their existing strategies for presenting permissions to the user and
for evaluating access(2).
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