2015-09-11 23:16 GMT+02:00 J. Bruce Fields [off-list ref]:
On Sat, Sep 05, 2015 at 12:27:05PM +0200, Andreas Gruenbacher wrote:
quoted
+ /*
+ * Apply the group file mask to entries other than owner@ and
+ * everyone@ or user entries matching the owner. This ensures
+ * that we grant the same permissions as the acl computed by
+ * richacl_apply_masks().
+ *
+ * Without this restriction, the following richacl would grant
+ * rw access to processes which are both the owner and in the
+ * owning group, but not to other users in the owning group,
+ * which could not be represented without masks:
+ *
+ * owner:rw::mask
+ * group@:rw::allow
+ */
+ if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace))
+ ace_mask &= acl->a_group_mask;
I'm having trouble understanding this. I think the problem is that I
don't really understand the notation in your example. Is a_group_mask
zero in that example? I think it must be, in which case, OK I think I
get it.
Yes. I'm not sure if the example becomes easier to understand when the
empty group mask and perhaps also the other mask is included.
(Though I still have to think about it a little more to convince myself
that richacl_apply_masks() always gets the same result.)
I have tried to break the algorithm into digestible pieces. Do you see
another way to make things easier to understand?
Thanks,
Andreas
On Sat, Sep 12, 2015 at 12:12:16AM +0200, Andreas Grünbacher wrote:
2015-09-11 23:16 GMT+02:00 J. Bruce Fields [off-list ref]:
quoted
On Sat, Sep 05, 2015 at 12:27:05PM +0200, Andreas Gruenbacher wrote:
quoted
+ /*
+ * Apply the group file mask to entries other than owner@ and
+ * everyone@ or user entries matching the owner. This ensures
+ * that we grant the same permissions as the acl computed by
+ * richacl_apply_masks().
+ *
+ * Without this restriction, the following richacl would grant
+ * rw access to processes which are both the owner and in the
+ * owning group, but not to other users in the owning group,
+ * which could not be represented without masks:
+ *
+ * owner:rw::mask
+ * group@:rw::allow
+ */
+ if ((acl->a_flags & RICHACL_MASKED) && richace_is_allow(ace))
+ ace_mask &= acl->a_group_mask;
I'm having trouble understanding this. I think the problem is that I
don't really understand the notation in your example. Is a_group_mask
zero in that example? I think it must be, in which case, OK I think I
get it.
Yes. I'm not sure if the example becomes easier to understand when the
empty group mask and perhaps also the other mask is included.
I think it would have been for me.
In general I find it confusing to present the mask bits as additional
ACEs--they're really pretty different.
quoted
(Though I still have to think about it a little more to convince myself
that richacl_apply_masks() always gets the same result.)
I have tried to break the algorithm into digestible pieces. Do you see
another way to make things easier to understand?
I just haven't reread those carefully enough yet, working on it....
--b.