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-To: PostgreSQL Development
-Subject: System catalog representation of access privileges
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-
-Oldtimers might recall the last thread about enhancements of the access
-privilege system. See
-
-http://www.postgresql.org/mhonarc/pgsql-hackers/2000-05/msg01220.html
-
-to catch up.
-
-It was more or less agreed that privilege descriptors should be split out
-into a separate table for better flexibility and ease of processing. The
-dispute was that the old proposal wanted to store only one privilege per
-row. I have devised something more efficient:
-
-pg_privilege (
- priobj oid, -- oid of table, column, function, etc.
- prigrantor oid, -- user who granted the privilege
- prigrantee oid, -- user who owns the privilege
-
- priselect char, -- specific privileges follow...
- prihierarchy char,
- priinsert char,
- priupdate char,
- pridelete char,
- prireferences char,
- priunder char,
- pritrigger char,
- prirule char
- /* obvious extension mechanism... */
-)
-
-The various "char" fields would be NULL for not granted, some character
-for granted, and some other character for granted with grant option (a
-poor man's enum, if you will). Votes on the particular characters are
-being taken. ;-) Since NULLs are stored specially, sparse pg_privilege
-rows wouldn't take extra space.
-
-"Usage" privileges on types and other non-table objects could probably be
-lumped under "priselect" (purely for internal purposes).
-
-For access we define system caches on these indexes:
-
-index ( priobj, prigrantee, priselect )
-index ( priobj, prigrantee, prihierarchy )
-index ( priobj, prigrantee, priinsert )
-index ( priobj, prigrantee, priupdate )
-index ( priobj, prigrantee, pridelete )
-
-These are the privileges you usually need quickly during query processing,
-the others are only needed during table creation. These indexes are not
-unique (more than one grantor can grant the same privilege), but AFAICS
-the syscache interface should work okay with this, since in normal
-operation we don't care who granted the privilege, only whether you have
-at least one.
-
-How does that look?
-
---
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-Date: Thu, 19 Apr 2001 14:37:48 -0500
-From: "Ross J. Reedstrom"
-cc: PostgreSQL Development
-Subject: Re: [HACKERS] System catalog representation of access privileges
-Mail-Followup-To: Peter Eisentraut
,-MIME-Version: 1.0
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-
-So, this will remove the relacl field from pg_class, making pg_class
-a fixed tuple-length table: that might actually speed access: there
-are shortcircuits in place to speed pointer math when this is true.
-
-The implementation looks fine to me, as well. How are group privileges
-going to be handled with this system?
-
-Ross
-
-On Thu, Apr 19, 2001 at 05:58:12PM +0200, Peter Eisentraut wrote:
-> Oldtimers might recall the last thread about enhancements of the access
-> privilege system. See
->
-> http://www.postgresql.org/mhonarc/pgsql-hackers/2000-05/msg01220.html
->
-> to catch up.
->
-> It was more or less agreed that privilege descriptors should be split out
-> into a separate table for better flexibility and ease of processing. The
-> dispute was that the old proposal wanted to store only one privilege per
-> row. I have devised something more efficient:
->
-> pg_privilege (
-
-
-
-
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-Date: Thu, 19 Apr 2001 16:17:52 -0400
-From: Mike Mascari
-Organization: Mascari Development Inc.
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-Subject: Re: [HACKERS] System catalog representation of access privileges
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-
-Peter Eisentraut wrote:
-
-> I have devised something more efficient:
->
-> pg_privilege (
-> priobj oid, -- oid of table, column, etc.
-> prigrantor oid, -- user who granted the privilege
-> prigrantee oid, -- user who owns the privilege
->
-> priselect char, -- specific privileges follow...
-> prihierarchy char,
-> priinsert char,
-> priupdate char,
-> pridelete char,
-> prireferences char,
-> priunder char,
-> pritrigger char,
-> prirule char
-> /* obvious extension mechanism... */
-> )
->
-> "Usage" privileges on types and other non-table objects could probably be
-> lumped under "priselect" (purely for internal purposes).
->
-
-That looks quite nice. I do have 3 quick questions though. First, I
-assume that the prigrantee could also be a group id? Or would this
-system table represent the effective privileges granted to user via
-groups? Second, one nice feature of Oracle is the ability to GRANT roles
-(our groups) to other roles. So I could do:
-
-CREATE ROLE clerk;
-GRANT SELECT on mascarm.deposits TO clerk;
-GRANT UPDATE (mascarm.deposits.amount) ON mascarm.deposits TO clerk;
-
-CREATE ROLE banker;
-GRANT clerk TO banker;
-
-Would any part of your design prohibit such functionality in the future?
-
-Finally, I'm wondering if "Usage" or "System" privileges should be
-another system table. For example, one day I would like to (as in
-Oracle):
-
-GRANT SELECT ANY TABLE TO foo WITH ADMIN;
-GRANT CREATE PUBLIC SYNONYM TO foo;
-GRANT DROP ANY TABLE TO foo;
-
-Presumably, in your design, the above would be represented by 3 records
-with something like the following values:
-
-This would be a "SELECT ANY TABLE" privilege (w/Admin):
-
-NULL, grantor_oid, grantee_oid, 'S', NULL, NULL, NULL, NULL, ...
-
-This would be a "CREATE PUBLIC SYNONYM" privilege:
-
-NULL, grantor_oid, grantee_oid, 'c', NULL, NULL, NULL, NULL, ...
-
-That means that the system would need an index as:
-
-index ( prigrantee, priselect )
-
-While I'm not arguing it won't work, it just doesn't "seem" clean to
-shoe-horn the system privileges into the same table as the object
-privileges.
-
-I've been wrong before though :-)
-
-Mike Mascari
-
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-Date: Thu, 19 Apr 2001 23:24:51 +0200 (CEST)
-To: Mike Mascari
-cc: PostgreSQL Development
-Subject: Re: [HACKERS] System catalog representation of access privileges
-MIME-Version: 1.0
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-
-Mike Mascari writes:
-
-> That looks quite nice. I do have 3 quick questions though. First, I
-> assume that the prigrantee could also be a group id?
-
-Yes. It was also suggested making two different grantee columns for users
-and groups, but I'm not yet convinced of that. It's an option though.
-
-> Second, one nice feature of Oracle is the ability to GRANT roles
-> (our groups) to other roles.
-
-Roles are not part of this deal, although I agree that they would be nice
-to have eventually. I'm not sure yet whether role grants would get a
-different system table, but I'm leaning there.
-
-> Would any part of your design prohibit such functionality in the future?
-
-Not that I can see.
-
-> Finally, I'm wondering if "Usage" or "System" privileges should be
-> another system table. For example, one day I would like to (as in
-> Oracle):
->
-> GRANT SELECT ANY TABLE TO foo WITH ADMIN;
-
-ANY TABLE probably implies "any table in this schema/database", no? In
-that case the grant record would refer to the oid of the schema/database.
-Is there any use distinguishing between ANY TABLE and ANY VIEW? That
-would make it a bit trickier.
-
-> GRANT CREATE PUBLIC SYNONYM TO foo;
-
-I'm not familiar with that above command.
-
-> GRANT DROP ANY TABLE TO foo;
-
-I'm not sold on a DROP privilege, but a CREATE privilege would be another
-column. I didn't include it here because it's not in SQL.
-
-> While I'm not arguing it won't work, it just doesn't "seem" clean to
-> shoe-horn the system privileges into the same table as the object
-> privileges.
-
-It would make sense to split privileges on tables from privileges on
-schemas/databases from privileges on, say, functions, etc. E.g.,
-
-pg_privtable -- like proposed
-
-pg_privschema (
- priobj oid, prigrantor oid, prigrantee oid,
- char pritarget, -- 't' = any table, 'v' = any view, ...
- char priselect,
- char priupdate,
- /* etc */
-)
-
-But this would mean that a check like "can I select from this table"
-would possibly require lookups in two tables. Not sure how much of a
-tradeoff that is, but the "shoehorn factor" would be lower.
-
-Comments on this?
-
---
-
-
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- Thu, 19 Apr 2001 17:53:26 -0400 (EDT)
-cc: PostgreSQL Development
-Subject: Re: [HACKERS] System catalog representation of access privileges
-Comments: In-reply-to Peter Eisentraut
- message dated "Thu, 19 Apr 2001 17:58:12 +0200"
-Date: Thu, 19 Apr 2001 17:53:26 -0400
-From: Tom Lane
-Precedence: bulk
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-
-Peter Eisentraut
writes:-> pg_privilege (
-> priobj oid, -- oid of table, column, function, etc.
-> prigrantor oid, -- user who granted the privilege
-> prigrantee oid, -- user who owns the privilege
-
-What about groups? What about wildcards? We already allow
-"grant
to PUBLIC (all)", and it would be nice to be able to do-something like "grant to joeblow"
-
-> Since NULLs are stored specially, sparse pg_privilege
-> rows wouldn't take extra space.
-
-Unless there get to be a very large number of privilege bits, it'd
-probably be better to handle these columns as NOT NULL, so that a fixed
-C struct record could be mapped onto the tuples. You'll notice that
-most of the other system tables are done that way.
-
-Alternatively, since you really only need two bits per privilege,
-perhaps a pair of BIT (VARYING?) fields would be a more effective
-approach. BIT VARYING would have the nice property that adding a new
-privilege type doesn't force initdb.
-
-> For access we define system caches on these indexes:
-
-> index ( priobj, prigrantee, priselect )
-> index ( priobj, prigrantee, prihierarchy )
-> index ( priobj, prigrantee, priinsert )
-> index ( priobj, prigrantee, priupdate )
-> index ( priobj, prigrantee, pridelete )
-
-Using the privilege bits as part of the index won't work if you intend
-to allow them to be null. Another objection is that this would end up
-caching multiple copies of the same tuple. A third is that you can't
-readily tell lack of an entry (implying you should use a default ACL
-setting, which might allow the access) from presence of an entry denying
-the access. A fourth is it doesn't work for groups or wildcards.
-
-> These indexes are not
-> unique (more than one grantor can grant the same privilege), but AFAICS
-> the syscache interface should work okay with this,
-
-Unfortunately not. The syscache stuff needs unique indexes, because it
-can only return one tuple for any given request.
-
-I don't really believe this indexing scheme is workable. Need to think
-some more. Possibly the syscache mechanism will not do, and we need a
-specially indexed privilege cache instead.
-
- regards, tom lane
-
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-Date: Thu, 19 Apr 2001 18:34:11 -0400
-From: Mike Mascari
-Organization: Mascari Development Inc.
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-Subject: Re: [HACKERS] System catalog representation of access privileges
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-
-First, let me say that just because Oracle does it this way doesn't make
-it better but...
-
-Oracle divides privileges into 2 categories:
-
-Object privileges
-System privileges
-
-The Object privileges are the ones you describe. And I agree
-fundamentally with your design. Although I would have (a) used a bitmask
-for the privileges and (b) have an additional bitmask which determines
-whether or not the Grantee could turn around and grant the same
-permission to someone else:
-
-pg_objprivs {
- priobj oid,
- prigrantor oid,
- prigrantee oid,
- priprivileges int4,
- priadmin int4
-};
-
-Where priprivileges is a bitmask for:
-
-0 ALTER - tables, sequences
-1 DELETE - tables, views
-2 EXECUTE - procedures, functions
-3 INDEX - tables
-4 INSERT - tables, views
-5 REFERENCES - tables
-6 SELECT - tables, views, sequences
-7 UPDATE - tables, views
-8 HIERARCHY - tables
-9 UNDER - tables
-
-And the priadmin is a bitmask to determine whether or not the Grantee
-could grant the same privilege to another user. Since these are Object
-privileges, 32 bits should be enough (and also 640K RAM ;-)).
-
-The System privileges are privileges granted to a user or role (a.k.a
-group) which are not associated with any particular object. This is one
-area where I think PostgreSQL needs a lot of work and thought,
-particularly with schemas coming down the road. Some example Oracle
-System privileges are:
-
-Typical User Privileges:
------------------------
-
-CREATE SESSION - Allows the user to connect
-CREATE SEQUENCE - Allows the user to create sequences in his schema
-CREATE SYNONYM - Allows the user to create private synonyms
-CREATE TABLE - Allows the user to create a table in his schema
-CREATE TRIGGER - Allows the user to create triggers on tables in his
-schema
-CREATE VIEW - Allows the user to create views in his schema
-
-Typical Power-User Privileges:
------------------------------
-
-ALTER ANY INDEX - Allows user to alter an index in *any* schema
-ALTER ANY PROCEDURE - Allows user to alter a procedure in *any* schema
-ALTER ANY TABLE - Allows user to alter a table in *any* schema
-...
-CREATE ANY TABLE - Allows user to create a table in *any* schema
-COMMENT ANY TABLE - Allows user to document any table in *any* schema
-...
-
-Typical DBA-Only Privileges:
----------------------------
-
-ALTER USER - Allows user to change password, quotas, etc. for *any* user
-CREATE USER - Allows user to create a new user
-DROP USER - Allows user to drop a new user
-GRANT ANY PRIVILEGE - Allows user to grant any privilege to any user
-ANALYZE ANY - Allows user to analyze any table in *any* schema
-
-There are, in fact, many, many more System Privileges that Oracle
-defines. You may want someone to connect to a database and query one
-table and that's it. Or you may want someone to have no other abilities
-except to document the database design via the great COMMENT ON command
-;-), etc.
-
-So for System Privileges, I would have something like:
-
-pg_sysprivs {
- prigrantee oid,
- priprivilege oid,
- prigroup bool,
- priadmin bool
-};
-
-So each System privilege granted to a user (or group) would be its own
-record. The priprivilege would be the OID of one of the many System
-privileges defined in the same way types are defined, if prigroup is
-false. If prigroup is true, however, then priprivilege is not a System
-privilege, but a group id. And then PostgreSQL will have to examine the
-privileges recursively for that group. Of course, you might not want to
-allow for the GRANTing of group privileges to other groups initially,
-which simplifies the implementation tremendously. But its a neat (if not
-complicated) Oracle-ism.
-
-Unfortunately, this means that the permission might require > 2 lookups.
-But these lookups are only if the previous lookup failed:
-
-SELECT * FROM employees.foo;
-
-1. Am I a member of the employees schema? Yes -> Done
-2. Have I been GRANTed the Object Privilege of:
- SELECT on employees.foo? Yes -> Done
-3. Have I been GRANTed the System Privilege of:
- SELECT ANY TABLE? Yes -> Done
-
-So the number of lookups does potentially increase, but only for those
-users that have been granted access through greater and greater layers
-of authority.
-
-I just think that each new feature added to PostgreSQL opens up a very
-large can of worms. Schemas are such a feature and the security system
-should be prepared for it.
-
-FWIW,
-
-Mike Mascari
-
-
-Peter Eisentraut wrote:
->
->
-> It would make sense to split privileges on tables from privileges on
-> schemas/databases from privileges on, say, functions, etc. E.g.,
->
-> pg_privtable -- like proposed
->
-> pg_privschema (
-> priobj oid, prigrantor oid, prigrantee oid,
-> char pritarget, -- 't' = any table, 'v' = any view, ...
-> char priselect,
-> char priupdate,
-> /* etc */
-> )
->
-> But this would mean that a check like "can I select from this table"
-> would possibly require lookups in two tables. Not sure how much of a
-> tradeoff that is, but the "shoehorn factor" would be lower.
->
-> Comments on this?
->
-> --
-
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-Date: Fri, 20 Apr 2001 17:31:16 +0200 (CEST)
-To: Tom Lane
-cc: PostgreSQL Development
-Subject: Re: [HACKERS] System catalog representation of access privileges
-MIME-Version: 1.0
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-
-Tom Lane writes:
-
-> Peter Eisentraut
writes:-> > pg_privilege (
-> > priobj oid, -- oid of table, column, function, etc.
-> > prigrantor oid, -- user who granted the privilege
-> > prigrantee oid, -- user who owns the privilege
->
-> What about groups?
-
-Either integrated into prigrantee or another column prigroupgrantee. One
-of these would always be zero or null, that's why I'm not sure if this
-isn't a waste of space.
-
-> What about wildcards? We already allow
-> "grant
to PUBLIC (all)", and it would be nice to be able to do-> something like "grant to joeblow"
-
-Public would be prigrantee == 0. About , how is this
-defined? If it is "everything I own and will ever own" then I suppose
-priobj == 0. Although I admit I have never seen this kind of privilege
-before. It's probably better to set up a group for that.
-
-> Alternatively, since you really only need two bits per privilege,
-> perhaps a pair of BIT (VARYING?) fields would be a more effective
-> approach. BIT VARYING would have the nice property that adding a new
-> privilege type doesn't force initdb.
-
-This would be tricky to index, I think.
-
-> I don't really believe this indexing scheme is workable. Need to think
-> some more. Possibly the syscache mechanism will not do, and we need a
-> specially indexed privilege cache instead.
-
-Maybe just an index on (object, grantee) and walk through that with an
-index scan. This is done in some other places as well (triggers, I
-recall), but the performance is probably not too exciting.
-
-However, last I looked at the syscache I figured that it would be
-perfectly capable of handling non-unique indexes if there only was an API
-to retrieve those values. Storing and finding the entries didn't seem to
-be the problem. Need to look there, probably.
-
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-
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-cc: PostgreSQL Development
-Subject: Re: [HACKERS] System catalog representation of access privileges
-Comments: In-reply-to Peter Eisentraut
- message dated "Fri, 20 Apr 2001 17:31:16 +0200"
-Date: Fri, 20 Apr 2001 12:35:46 -0400
-From: Tom Lane
-Precedence: bulk
-Status: RO
-
-Peter Eisentraut
writes:->> Alternatively, since you really only need two bits per privilege,
->> perhaps a pair of BIT (VARYING?) fields would be a more effective
->> approach. BIT VARYING would have the nice property that adding a new
->> privilege type doesn't force initdb.
-
-> This would be tricky to index, I think.
-
-True, but I don't believe that making the privilege value part of the
-index is useful.
-
-> Maybe just an index on (object, grantee) and walk through that with an
-> index scan. This is done in some other places as well (triggers, I
-> recall), but the performance is probably not too exciting.
-
-I agree, that'd be slower than we'd like. It needs to be cached somehow.
-
-The major problem is that you'd need multiple index scans: after failing
-to find anything for (table, currentuser) you'd also need to try
-(table, 0) for PUBLIC and (table, G) for every group G that contains the
-current user. Not to mention the scan to find out which groups those are.
-
-It gets rapidly worse if you want to allow any wildcarding on the object
---- for example, if a privilege record attached to a schema can allow
-access to the tables therein, which I think should be possible. You'd
-have to repeat the above for each possible priobject that might relate
-to the target object.
-
-I think this might be tolerable for getting the info in the first place,
-but the final results really need to be cached. That's why I was
-wondering about a special "privilege cache".
-
-> However, last I looked at the syscache I figured that it would be
-> perfectly capable of handling non-unique indexes if there only was an API
-> to retrieve those values.
-
-Yes, it's an API problem more than anything else. Invent away, if that
-seems like a needed component.
-
- regards, tom lane
-
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