I am fairly new to Postgresql, and this is the situation:
I have many databases on one instance
I have many users, each map 1-1 with a database (e.g. Each user can connect to only one database)
Each user is EITHER Read/Write or Read Only
Now I have figured out how to do this one way, but seems clunky:
Create a Group Role for each User
Create a Login Role for each User
Grant default privileges to Group role on relevant database
However, I'd rather just have one login role for each user, and this role would have a "Type" of READONLY/READ WRITE. Each user would have these rights on ONLY one database.
Any suggestions how that might be achieved?
Ok, after writing this out, solved the problem!
Create Group roles "admin_ro", and "admin_rw"
Create user roles, as members of one of the above
Grant "Connect" to user role on individual databases
Grant the relevant default privileges to the "group role" on the database
Related
I'd like to ask Postgres experts about a confusing sentence which I found in the documentation. In particular, I refer to the GRANT command, where the documentation states:
If the role executing GRANT holds the required privileges indirectly via more than one role membership path, it is unspecified which containing role will be recorded as having done the grant. In such cases it is best practice to use SET ROLE to become the specific role you want to do the GRANT as.
If I understand correctly, this is related to role inheritance. In particular, you might have a role C which inherits a permission from both role A and role B. In this case, if a user has role C and grants the permission, then Postgres might non-deterministically stipulate that the permission was granted by either A or B. To avoid this ambiguity, the user can issue SET ROLE A or SET ROLE B to force a lesser role and clarify how the granting should occur.
Some questions about this and a more general one:
Is this reading correct or does the sentence mean something different?
What if, in the prior example, a user has the permission via A and C (as opposed to A and B)? In that case, the recommended practice of using "SET ROLE to become the specific role you want to do the GRANT as" does not seem to help, because setting the role to C still leaves an ambiguity due to inheritance.
More generally, is there any good reference documentation where the role system of Postgres is compared against traditional SQL grant diagrams? Some parts of the Postgres implementation are not straightforward and I'd like to learn more about it, which is complicated to do via experiments alone.
Thanks in advance.
Yes, in my opinion, you are right:
You understand it correctly.
It is no matters if the role that grants a permission has innerited the privilege or not. For each permission that you have postgress registers the role that granted the privilege.
I don't know. If you find it, please post a comment.
Is it possible in PostgreSQL to give a specific user or group on edit rights only to one schema?
I need the user to only change the objects in the schema. Similar to superuser rights, but only for one schema.
Thank for advance
The best setup in your case is probably the following.
Let's assume that the schema and the objects therein are owned by object_owner and the user that should have “superuser” privileges is called wannabe.
Then you can do:
ALTER ROLE wannabe NOINHERIT;
GRANT object_owner TO wannabe;
That allows wannabe to become object_owner by running
SET ROLE object_owner;
similar to using su in UNIX. Use RESET ROLE to step down again.
I am creating a PostgreSQL user for a in internal dashboard where I want the user's access to the db to default to read-only.
I did some research, and it seems to be a bit complex to create a read-only user who also inherits access to any new tables, materialized views, etc.
So I think the simplest thing is just to set:
ALTER USER readuser SET default_transaction_read_only = on;
How do I set this using the Ansible PostgreSQL modules?
I'm not sure if I should be using the postgresql_privs or postgresql_user module. I tried experimenting with different values for the priv attribute, but couldn't get anything to work.
I'm aware that this is not guaranteed read-only, as the user could just change the type of transaction at runtime. However, it will be just fine for my usecase since security isn't an issue, I just want to protect against ignorant users accidentally modifying data. If someone is knowledgable enough to change their transaction, I'd rather assume they know what they're doing and have a legitimate reason for it.
I'm not sure if I should be using the postgresql_privs or
postgresql_user module. I tried experimenting with different values
for the priv attribute, but couldn't get anything to work.
Did you tried to revoke privs?:
# REVOKE INSERT, UPDATE ON ALL TABLES IN SCHEMA public FROM reader
# "public" is the default schema. This also works for PostgreSQL 8.x.
- postgresql_privs: >
db=library
state=absent
privs=INSERT,UPDATE
objs=ALL_IN_SCHEMA
role=reader
Note:
To revoke only GRANT OPTION for a specific object, set state to
present and grant_option to no (see examples http://docs.ansible.com/ansible/postgresql_privs_module.html).
Note that when revoking privileges from a role R, this role may still
have access via privileges granted to any role R is a member of
including PUBLIC.
Note that when revoking privileges from a role R, you do so as the
user specified via login. If R has been granted the same privileges by
another user also, R can still access database objects via these
privileges.
I have created a role in DB2 and granted some object level access to that role and next ranted that role to some users. How Can I identify which user is having this role and due to that what access the user is having object level.
The DB2 function AUTH_LIST_AUTHORITIES_FOR_AUTHID probably is what you are looking for. In the background it queries the system catalog tables for entries of that specified user. If you are only looking for certain object types, you could directly query a single catalog table, e.g., SYSCAT.TABAUTH for who has access to tables. There is a column for GRANTEETYPE and a value to indicate "role".
You can find users and their roles by querying SYSCAT.ROLEAUTH.
you can use db2look tool to extract the information regarding all the access that particular role carrying or what access is being carrying by the user...
db2look -d database_name -x -o db2look.out
From the PostgreSQL docs:
The concept of roles subsumes the concepts of "users" and "groups". In
PostgreSQL versions before 8.1, users and groups were distinct kinds
of entities, but now there are only roles. Any role can act as a user,
a group, or both.
Why did they make this change in 8.1?
Perhaps it's easier from the C coders point of view, with a single Role class (struct)?
More details:
CREATE USER is equivalent to CREATE ROLE except that CREATE USER gives the LOGIN permission to the user/role.
(I'm about to design a permission system for my webapp, hence I'm interested in this.)
The merge has many advantages and no disadvantages. For instance, you can now seamlessly convert a "user" to a "group" and vice versa by adding / removing the LOGIN privilege.
ALTER ROLE myrole LOGIN;
ALTER ROLE myrole NOLOGIN;
Or you can GRANT membership in any other login ("user") or non-login role ("group") to a role:
GRANT joe TO sue;
You can still:
CREATE USER james;
That's just a role with login privilege now. Or:
CREATE GROUP workers;
That's effectively the same as CREATE ROLE now.
The manual has it all.
I found this thread in the PostgreSQL-Hackers list, from June 6, 2003, that in the end suggests that users and groups and roles be consolidated. (Thanks Craig Ringer for suggesting that I check the pgsql-hackers list archives.)
Here are some benefits mentioned (those that I found).
allow groups to have groups as members
the ACL code would be simplified
the GRANT/REVOKE syntax and the display format for ACL lists could be
simplified, since there'd be no need for a syntactic marker as to
whether a given name is a user or a group.
In some circumstances I could see it making sense to allow logging in
directly as a group/role/whatchacallit
This would also solve the problem that information_schema views will
show only owned objects
[makes it easier to] representing privileges granted to groups [since
you'd simply reuse the role related code?]
From the manual:
The SQL standard defines the concepts of users and roles, but it
regards them as distinct concepts and leaves all commands defining
users to be specified by each database implementation. In PostgreSQL
we have chosen to unify users and roles into a single kind of entity.
Roles therefore have many more optional attributes than they do in the
standard.
Having a distinction between users and groups doesn't gain you anything.
AFAIK the motivation for changing it was to simplify uses like:
One user masquerading as another, eg a superuser simulating a reduced permissions user. With unified roles this becomes just another change of current role, no different to changing primary group.
Groups that are members of other groups to implement granular access permissions.
If you want the details, though, you're best off checking out the archives of the pgsql-hackers list for the period, and the git history (converted from CVS).