#
# SPDX-License-Identifier: AGPL-3.0
+require '20200501150153_permission_table_constants'
+
class PermissionTable < ActiveRecord::Migration[5.0]
def up
+ # This is a major migration. We are replacing the
+ # materialized_permission_view, which is fully recomputed any time
+ # a permission changes (and becomes very expensive as the number
+ # of users/groups becomes large), with a new strategy that only
+ # recomputes permissions for the subset of objects that are
+ # potentially affected by the addition or removal of a permission
+ # relationship (i.e. ownership or a permission link).
+ #
+ # This also disentangles the concept of "trashed groups" from the
+ # permissions system. Updating trashed items follows a similar
+ # (but less complicated) strategy to updating permissions, so it
+ # may be helpful to look at that first.
+
ActiveRecord::Base.connection.execute "DROP MATERIALIZED VIEW IF EXISTS materialized_permission_view;"
drop_table :permission_refresh_lock
- create_table :materialized_permissions, :id => false do |t|
- t.string :user_uuid
- t.string :target_uuid
- t.integer :perm_level
- t.boolean :traverse_owned
+ # This table stores the set of trashed groups and their trash_at
+ # time. Used to exclude trashed projects and their contents when
+ # getting object listings.
+ create_table :trashed_groups, :id => false do |t|
+ t.string :group_uuid
+ t.datetime :trash_at
end
- add_index :materialized_permissions, [:user_uuid, :target_uuid], unique: true, name: 'permission_user_target'
- add_index :materialized_permissions, [:target_uuid], unique: false, name: 'permission_target'
+ add_index :trashed_groups, :group_uuid, :unique => true
ActiveRecord::Base.connection.execute %{
create or replace function project_subtree_with_trash_at (starting_uuid varchar(27), starting_trash_at timestamp)
STABLE
language SQL
as $$
+/* Starting from a project, recursively traverse all the projects
+ underneath it and return a set of project uuids and trash_at times
+ (may be null). The initial trash_at can be a timestamp or null.
+ The trash_at time propagates downward to groups it owns, i.e. when a
+ group is trashed, everything underneath it in the ownership
+ hierarchy is also considered trashed. However, this is fact is
+ recorded in the trashed_groups table, not by updating trash_at field
+ in the groups table.
+*/
WITH RECURSIVE
project_subtree(uuid, trash_at) as (
values (starting_uuid, starting_trash_at)
$$;
}
- create_table :trashed_groups, :id => false do |t|
- t.string :group_uuid
- t.datetime :trash_at
- end
- add_index :trashed_groups, :group_uuid, :unique => true
-
- ActiveRecord::Base.connection.execute %{
-create or replace function compute_trashed ()
-returns table (uuid varchar(27), trash_at timestamp)
-STABLE
-language SQL
-as $$
-select ps.target_uuid as group_uuid, ps.trash_at from groups,
- lateral project_subtree_with_trash_at(groups.uuid, groups.trash_at) ps
- where groups.owner_uuid like '_____-tpzed-_______________'
-$$;
-}
+ # Now populate the table. For a non-test databse this is the only
+ # time this ever happens, after this the trash table is updated
+ # incrementally. See app/models/group.rb#update_trash
+ refresh_trashed
- ActiveRecord::Base.connection.execute("INSERT INTO trashed_groups select * from compute_trashed()")
+ # The table to store the flattened permissions. This is almost
+ # exactly the same as the old materalized_permission_view except
+ # that the target_owner_uuid colunm in the view is now just a
+ # boolean traverse_owned (the column was only ever tested for null
+ # or non-null).
+ #
+ # For details on how this table is used to apply permissions to
+ # queries, see app/models/arvados_model.rb#readable_by
+ #
+ create_table :materialized_permissions, :id => false do |t|
+ t.string :user_uuid
+ t.string :target_uuid
+ t.integer :perm_level
+ t.boolean :traverse_owned
+ end
+ add_index :materialized_permissions, [:user_uuid, :target_uuid], unique: true, name: 'permission_user_target'
+ add_index :materialized_permissions, [:target_uuid], unique: false, name: 'permission_target'
ActiveRecord::Base.connection.execute %{
create or replace function should_traverse_owned (starting_uuid varchar(27),
starting_perm integer)
returns bool
-STABLE
+IMMUTABLE
language SQL
as $$
+/* Helper function. Determines if permission on an object implies
+ transitive permission to things the object owns. This is always
+ true for groups, but only true for users when the permission level
+ is can_manage.
+*/
select starting_uuid like '_____-j7d0g-_______________' or
(starting_uuid like '_____-tpzed-_______________' and starting_perm >= 3);
$$;
}
+ # Merge all permission relationships into a single view. This
+ # consists of: groups owned by users and projects, users owned
+ # by other users, users have permission on themselves,
+ # and explicit permission links.
+ #
+ # A SQL view gets inlined into the query where it is used as a
+ # subquery. This enables the query planner to inject constraints,
+ # so it only has to look up edges it plans to traverse and avoid a brute
+ # force query of all edges.
ActiveRecord::Base.connection.execute %{
create view permission_graph_edges as
- select groups.owner_uuid as tail_uuid, groups.uuid as head_uuid, (3) as val from groups
+ select groups.owner_uuid as tail_uuid, groups.uuid as head_uuid,
+ (3) as val, groups.uuid as edge_id from groups
union all
- select users.owner_uuid as tail_uuid, users.uuid as head_uuid, (3) as val from users
+ select users.owner_uuid as tail_uuid, users.uuid as head_uuid,
+ (3) as val, users.uuid as edge_id from users
+union all
+ select users.uuid as tail_uuid, users.uuid as head_uuid,
+ (3) as val, '' as edge_id from users
union all
select links.tail_uuid,
links.head_uuid,
WHEN links.name = 'can_login' THEN 1
WHEN links.name = 'can_write' THEN 2
WHEN links.name = 'can_manage' THEN 3
- END as val
+ ELSE 0
+ END as val,
+ links.uuid as edge_id
from links
where links.link_class='permission'
}
- # Get a set of permission by searching the graph and following
- # ownership and permission links.
- #
- # edges() - a subselect with the union of ownership and permission links
- #
- # traverse_graph() - recursive query, from the starting node,
- # self-join with edges to find outgoing permissions.
- # Re-runs the query on new rows until there are no more results.
- # This accomplishes a breadth-first search of the permission graph.
- #
- ActiveRecord::Base.connection.execute %{
-create or replace function search_permission_graph (starting_uuid varchar(27),
- starting_perm integer)
- returns table (target_uuid varchar(27), val integer, traverse_owned bool)
-STABLE
-language SQL
-as $$
-WITH RECURSIVE
- traverse_graph(target_uuid, val, traverse_owned) as (
- values (starting_uuid, starting_perm,
- should_traverse_owned(starting_uuid, starting_perm))
- union
- (select edges.head_uuid,
- least(edges.val, traverse_graph.val,
- case traverse_graph.traverse_owned
- when true then null
- else 0
- end),
- should_traverse_owned(edges.head_uuid, edges.val)
- from permission_graph_edges as edges, traverse_graph
- where traverse_graph.target_uuid = edges.tail_uuid))
- select target_uuid, max(val), bool_or(traverse_owned) from traverse_graph
- group by (target_uuid);
-$$;
+ # This is used to ensure that the permission edge passed into
+ # compute_permission_subgraph takes replaces the existing edge in
+ # the "edges" view that is about to be removed.
+ edge_perm = %{
+case (edges.edge_id = perm_edge_id)
+ when true then starting_perm
+ else edges.val
+ end
}
+ # The primary function to compute permissions for a subgraph.
+ # Comments on how it works are inline.
+ #
+ # Due to performance issues due to the query optimizer not
+ # working across function and "with" expression boundaries, I
+ # had to fall back on using string templates for repeated code
+ # in order to inline it.
+
ActiveRecord::Base.connection.execute %{
create or replace function compute_permission_subgraph (perm_origin_uuid varchar(27),
starting_uuid varchar(27),
- starting_perm integer)
+ starting_perm integer,
+ perm_edge_id varchar(27))
returns table (user_uuid varchar(27), target_uuid varchar(27), val integer, traverse_owned bool)
STABLE
language SQL
as $$
+
+/* The purpose of this function is to compute the permissions for a
+ subgraph of the database, starting from a given edge. The newly
+ computed permissions are used to add and remove rows from the main
+ permissions table.
+
+ perm_origin_uuid: The object that 'gets' the permission.
+
+ starting_uuid: The starting object the permission applies to.
+
+ starting_perm: The permission that perm_origin_uuid 'has' on
+ starting_uuid One of 1, 2, 3 for can_read,
+ can_write, can_manage respectively, or 0 to revoke
+ permissions.
+
+ perm_edge_id: Identifies the permission edge that is being updated.
+ Changes of ownership, this is starting_uuid.
+ For links, this is the uuid of the link object.
+ This is used to override the edge value in the database
+ with starting_perm. This is necessary when revoking
+ permissions because the update happens before edge is
+ actually removed.
+*/
with
-perm_from_start(perm_origin_uuid, target_uuid, val, traverse_owned) as (
- select perm_origin_uuid, target_uuid, val, traverse_owned
- from search_permission_graph(starting_uuid, starting_perm)),
+ /* Starting from starting_uuid, determine the set of objects that
+ could be affected by this permission change.
+
+ Note: We don't traverse users unless it is an "identity"
+ permission (permission origin is self).
+ */
+ perm_from_start(perm_origin_uuid, target_uuid, val, traverse_owned) as (
+ #{PERM_QUERY_TEMPLATE % {:base_case => %{
+ values (perm_origin_uuid, starting_uuid, starting_perm,
+ should_traverse_owned(starting_uuid, starting_perm),
+ (perm_origin_uuid = starting_uuid or starting_uuid not like '_____-tpzed-_______________'))
+},
+:edge_perm => edge_perm
+} }),
+ /* Find other inbound edges that grant permissions to 'targets' in
+ perm_from_start, and compute permissions that originate from
+ those.
+
+ This is necessary for two reasons:
+
+ 1) Other users may have access to a subset of the objects
+ through other permission links than the one we started from.
+ If we don't recompute them, their permission will get dropped.
+
+ 2) There may be more than one path through which a user gets
+ permission to an object. For example, a user owns a project
+ and also shares it can_read with a group the user belongs
+ to. adding the can_read link must not overwrite the existing
+ can_manage permission granted by ownership.
+ */
additional_perms(perm_origin_uuid, target_uuid, val, traverse_owned) as (
- select edges.tail_uuid as perm_origin_uuid, ps.target_uuid, ps.val,
- should_traverse_owned(ps.target_uuid, ps.val)
- from permission_graph_edges as edges, lateral search_permission_graph(edges.head_uuid, edges.val) as ps
- where (not (edges.tail_uuid = perm_origin_uuid and
- edges.head_uuid = starting_uuid)) and
- edges.tail_uuid not in (select target_uuid from perm_from_start) and
- edges.head_uuid in (select target_uuid from perm_from_start)),
-
- partial_perms(perm_origin_uuid, target_uuid, val, traverse_owned) as (
+ #{PERM_QUERY_TEMPLATE % {:base_case => %{
+ select edges.tail_uuid as origin_uuid, edges.head_uuid as target_uuid, edges.val,
+ should_traverse_owned(edges.head_uuid, edges.val),
+ edges.head_uuid like '_____-j7d0g-_______________'
+ from permission_graph_edges as edges
+ where edges.edge_id != perm_edge_id and
+ edges.tail_uuid not in (select target_uuid from perm_from_start where target_uuid like '_____-j7d0g-_______________') and
+ edges.head_uuid in (select target_uuid from perm_from_start)
+},
+:edge_perm => edge_perm
+} }),
+
+ /* Combine the permissions computed in the first two phases. */
+ all_perms(perm_origin_uuid, target_uuid, val, traverse_owned) as (
select * from perm_from_start
union all
select * from additional_perms
- ),
+ )
- user_identity_perms(perm_origin_uuid, target_uuid, val, traverse_owned) as (
- select users.uuid as perm_origin_uuid, ps.target_uuid, ps.val, ps.traverse_owned
- from users, lateral search_permission_graph(users.uuid, 3) as ps
- where (users.owner_uuid not in (select target_uuid from partial_perms) or
- users.owner_uuid = users.uuid) and
- users.uuid in (select target_uuid from partial_perms)
- ),
+ /* The actual query that produces rows to be added or removed
+ from the materialized_permissions table. This is the clever
+ bit.
- all_perms(perm_origin_uuid, target_uuid, val, traverse_owned) as (
- select * from partial_perms
- union
- select * from user_identity_perms
- )
+ Key insights:
+ * For every group, the materialized_permissions lists all users
+ that can access to that group.
+
+ * The all_perms subquery has computed permissions on on a set of
+ objects for all inbound "origins", which are users or groups.
+
+ * Permissions through groups are transitive.
+
+ We can infer:
+
+ 1) The materialized_permissions table declares that user X has permission N on group Y
+ 2) The all_perms result has determined group Y has permission M on object Z
+ 3) Therefore, user X has permission min(N, M) on object Z
+
+ This allows us to efficiently determine the set of users that
+ have permissions on the subset of objects, without having to
+ follow the chain of permission back up to find those users.
+
+ In addition, because users always have permission on themselves, this
+ query also makes sure those permission rows are always
+ returned.
+ */
select v.user_uuid, v.target_uuid, max(v.perm_level), bool_or(v.traverse_owned) from
(select m.user_uuid,
u.target_uuid,
u.traverse_owned
from all_perms as u, materialized_permissions as m
where u.perm_origin_uuid = m.target_uuid AND m.traverse_owned
+ AND (m.user_uuid = m.target_uuid or m.target_uuid not like '_____-tpzed-_______________')
union all
- select perm_origin_uuid as user_uuid, target_uuid, val as perm_level, traverse_owned
+ select target_uuid as user_uuid, target_uuid, 3, true
from all_perms
- where all_perms.perm_origin_uuid like '_____-tpzed-_______________') as v
+ where all_perms.target_uuid like '_____-tpzed-_______________') as v
group by v.user_uuid, v.target_uuid
$$;
}
- ActiveRecord::Base.connection.execute %{
-INSERT INTO materialized_permissions
-select users.uuid, g.target_uuid, g.val, g.traverse_owned
-from users, lateral search_permission_graph(users.uuid, 3) as g where g.val > 0
-}
+ #
+ # Populate materialized_permissions by traversing permissions
+ # starting at each user.
+ #
+ refresh_permissions
end
def down
drop_table :trashed_groups
ActiveRecord::Base.connection.execute "DROP function project_subtree_with_trash_at (varchar, timestamp);"
- ActiveRecord::Base.connection.execute "DROP function compute_trashed ();"
- ActiveRecord::Base.connection.execute "DROP function search_permission_graph(varchar, integer);"
- ActiveRecord::Base.connection.execute "DROP function compute_permission_subgraph (varchar, varchar, integer);"
+ ActiveRecord::Base.connection.execute "DROP function compute_permission_subgraph (varchar, varchar, integer, varchar);"
ActiveRecord::Base.connection.execute "DROP function should_traverse_owned(varchar, integer);"
ActiveRecord::Base.connection.execute "DROP view permission_graph_edges;"
projects / arvados.git / blobdiff