Revoking right for user to DROP table - sql

I am a big fan of PostgreSQL but can't figure out one aspects of it's built in user management.
My problem is that I have set up pgAdmin and will have some non-developers manually update data in some specific tables. For this reason I have created a new user called "admin" and are looking to restrict this users rights.
I have tried to delete all rights for the user with the following query (from another user):
REVOKE ALL PRIVILEGES ON ALL TABLES IN SCHEMA public FROM admin;
REVOKE ALL PRIVILEGES ON ALL SEQUENCES IN SCHEMA public FROM admin;
REVOKE ALL PRIVILEGES ON ALL FUNCTIONS IN SCHEMA public FROM admin;
The above did lead to the following error when I wrote a simple SELECT statement from the user admin on a table called "crap": ERROR: permission denied for relation crap.
But what I was able to do with the user admin which by now shouldn't have any rights was the following: DROP TABLE crap; which worked!?
I am really surprised by this. This user is not a Postgres superuser. How can I remove this right to drop tables for a specific user?

You're one level off in hierarchy for the permissions.
REVOKE ALL PRIVILEGES FROM SCHEMA public FROM <role_name>;
You were affecting permissions within the table. You must also go one level up to the schema as well to protect create/drop access. You may also want to revoke access at the database level as well to protect the schema.
REVOKE ALL PRIVILEGES FROM DATABASE <database_name> FROM <role_name>;
You could also simply remove the user. Alternatively you could simply disable that user's ability to login.
ALTER ROLE <role_name> SET NOLOGIN;
If these don't work for you, you can go down a somewhat more complicated route and make an event trigger that watches for DROP TABLE events, compares against the role, and either allows it to continue or aborts the transaction.
CREATE OR REPLACE FUNCTION no_admin_drop()
RETURNS event_trigger LANGUAGE plpgsql AS $$
BEGIN
IF CURRENT_USER = 'admin'::regrole THEN
RAISE EXCEPTION 'command is disabled';
END IF;
END;
$$;
CREATE EVENT TRIGGER no_admin_drop ON sql_drop
EXECUTE FUNCTION no_admin_drop();

Related

Prevent all users from accessing tables/views under a schema

I am connecting to my SQL studio manager using Power BI (a report writing software). I only want tables appearing listed under a certain schema, and deny permission to access all others, instead of displaying all tables which it currently does.
Usually, when preventing individual users from accessing a schema, I would use the following code:
revoke select on schema::UnwantedSchema to User
grant select on schema::WantedSchema To User
However, now I want it so ALL users and Logins have these permission settings. Not just the individual user. Is there a way I can do this without having to set the permissions for every individual user?
If you wanted to set the privileges to multiple user logins, You need to create a role and assign the role to the ers to that role. The give required permission to the role created.
Following are the sample steps.
--Create a new role
EXEC sp_addrole 'yourRole'
GO
--Assiging role to the user
EXEC sp_addrolemember 'yourRole', 'yourUser';
GO
--Assigning permissions to the Role
GRANT ALTER, DELETE, EXECUTE, INSERT, REFERENCES, SELECT,
UPDATE, VIEW DEFINITION ON SCHEMA::YourSchema TO yourRole;
GO
GRANT CREATE TABLE, CREATE PROCEDURE, CREATE FUNCTION, CREATE VIEW TO yourRole;
GO

Restricting Delete/Update on a table for a Login

Is there a way to restrict a particular user from making any modification on particular table.
I am thinking to create a Instead of trigger and some how get the login info and restrict the user from running delete/update statements.
But is there any better way to do this, like Sql server has some login permission setting to restrict this
I'd revoke all privileges first (assuming you already have the user)
REVOKE ALL
ON {object_name}
FROM {user_name}
Then grant only SELECT to that user.
GRANT SELECT, INSERT
ON {object_name}
TO {user_name}

SAP Hana Revoke all Priviledge and roles from User

Anyone have written a stored procedure which can remove all assigned roles/privileges from given user ? I like to do this without looking up each role assigned or privilege assigned.
Similar like below statement but without listing each role and privileges one by one. Removal all roles/privilege in one single statement regardless of what role assigned. This is for user termination process.
CALL REVOKE_ACTIVATED_ROLE('RoleName','username');
Well if you really want the procedure, I'm using this one and it works.
It removes all the granted roles from the user. Run it if you know what you are doing.
create procedure myCleanupUser(in i_user varchar(20)) as
begin
declare cursor Roles for
SELECT ROLE_NAME FROM "PUBLIC"."EFFECTIVE_ROLES"
where USER_NAME=i_user AND GRANTEE_TYPE='USER' AND ROLE_NAME <> 'PUBLIC';
for role as Roles do
call REVOKE_ACTIVATED_ROLE(role.ROLE_NAME,i_user);
end for;
end;
There's no such standard functionality available and I recommend to be very careful with automatically revoking privileges. If the user himself granted privileges that he got granted with ADMIN OPTION or with GRANT OPTION to other users and these privileges get revoked, this leads to a recursive revocation of those granted privileges.
In short: this can become nasty.
For user termination, it's sufficient from a security point of view to disable the logon.
Other than that, it's pretty straight forward to query system view GRANTED_ROLES and GRANTED_PRIVILEGES to generate the REVOKE statements.

Create an user in Oracle database

I am the first user of Oracle Database.
Now, I want to create a DB schema called ERDB.
I need to create the ERDB user and granting appropriate privileges to the ERDB user on SQL script file.
CREATE USER dmuser IDENTIFIED BY password
DEFAULT TABLESPACE USERS
TEMPORARY
TABLESPACE TEMP
QUOTA UNLIMITED ON USERS;
GRANT CREATE JOB TO dmuser;
GRANT CREATE MINING MODEL TO dmuser;
GRANT CREATE PROCEDURE TO dmuser;
GRANT CREATE SEQUENCE TO dmuser;
GRANT CREATE SESSION TO dmuser;
GRANT CREATE SYNONYM TO dmuser;
GRANT CREATE TABLE TO dmuser;
GRANT CREATE TYPE TO dmuser;
GRANT CREATE VIEW TO dmuser;
GRANT EXECUTE ON ctxsys.ctx_ddl TO dmuser;
but the error happens, SQL Error: ORA 01031 insufficient privileges;
please help me.
The Oracle documentation clearly states the following:
Prerequisites
You must have the CREATE USER system privilege.
Connect as SYSTEM, no need of SYSDBA and then execute:
CREATE USER user IDENTIFIED BY password
Similarly, execute other command to create the tablespaces and required grants etc.
On a side note, regarding SYSDBA:
Never ever use SYS (or SYSDBA) but for maintenance purpose (startup, shutdown, backup, recover)
SYS/SYSDBA is special
SYS/SYSDBA is Oracle proprietary (try to open a SR/TAR starting with "i did that with SYS/SYSDBA" and you'll see the immediate answer)
SYS/SYSDBA does not act like any other user
When you use SYS/SYSDBA Oracle deactivates some code path and activates others
Whatever you do with SYS/SYSDBA will neither validate nor invalidate the same thing with any other user.
NEVER EVER use SYS/SYSDBA for anything that can be done by another
user. Use SYS/SYSDBA ONLY for something that can't be done by someone
else.

Grant privileges for a particular database in PostgreSQL

I'm moving from MySQL to PostgreSQL and have hit a wall with user privileges. I am used to assigning a user all privileges to all tables of a database with the following command:
# MySQL
grant all privileges on mydatabase.* to 'myuser'#'localhost' identified by 'mypassword';
It appears to me that the PostgreSQL 9.x solution involves assigning privileges to a "schema", but the effort required of me to figure out exactly what SQL to issue is proving excessive. I know that a few more hours of research will yield an answer, but I think everyone moving from MySQL to PostgreSQL could benefit from having at least one page on the web that provides a simple and complete recipe. This is the only command I have ever needed to issue for users. I'd rather not have to issue a command for every new table.
I don't know what scenarios have to be handled differently in PostgreSQL, so I'll list some of the scenarios that I have typically had to handle in the past. Assume that we only mean to modify privileges to a single database that has already been created.
(1a) Not all of the tables have been created yet, or (1b) the tables have already been created.
(2a) The user has not yet been created, or (2b) the user has already been created.
(3a) Privileges have not yet been assigned to the user, or (3b) privileges were previously assigned to the user.
(4a) The user only needs to insert, update, select, and delete rows, or (4b) the user also needs to be able to create and delete tables.
I have seen answers that grant all privileges to all databases, but that's not what I want here. Please, I am looking for a simple recipe, although I wouldn't mind an explanation as well.
I don't want to grant rights to all users and all databases, as seems to be the conventional shortcut, because that approach compromises all databases when any one user is compromised. I host multiple database clients and assign each client a different login.
It looks like I also need the USAGE privilege to get the increasing values of a serial column, but I have to grant it on some sort of sequence. My problem got more complex.
Basic concept in Postgres
Roles are global objects that can access all databases in a db cluster - given the required privileges.
A cluster holds many databases, which hold many schemas. Schemas (even with the same name) in different DBs are unrelated. Granting privileges for a schema only applies to this particular schema in the current DB (the current DB at the time of granting).
Every database starts with a schema public by default. That's a convention, and many settings start with it. Other than that, the schema public is just a schema like any other.
Coming from MySQL, you may want to start with a single schema public, effectively ignoring the schema layer completely. I am using dozens of schema per database regularly.
Schemas are a bit (but not completely) like directories in the file system.
Once you make use of multiple schemas, be sure to understand search_path setting:
How does the search_path influence identifier resolution and the "current schema"
Default privileges
Per documentation on GRANT:
PostgreSQL grants default privileges on some types of objects to
PUBLIC. No privileges are granted to PUBLIC by default on tables,
columns, schemas or tablespaces. For other types, the default
privileges granted to PUBLIC are as follows: CONNECT and CREATE TEMP TABLE
for databases; EXECUTE privilege for functions; and USAGE privilege for languages.
All of these defaults can be changed with ALTER DEFAULT PRIVILEGES:
Grant all on a specific schema in the db to a group role in PostgreSQL
Group role
Like #Craig commented, it's best to GRANT privileges to a group role and then make a specific user member of that role (GRANT the group role to the user role). This way it is simpler to deal out and revoke bundles of privileges needed for certain tasks.
A group role is just another role without login. Add a login to transform it into a user role. More:
Why did PostgreSQL merge users and groups into roles?
Predefined roles
Update: Postgres 14 or later adds the new predefined roles (formally "default roles") pg_read_all_data and pg_write_all_data to simplify some of the below. See:
Grant access to all tables of a database
Recipe
Say, we have a new database mydb, a group mygrp, and a user myusr ...
While connected to the database in question as superuser (postgres for instance):
REVOKE ALL ON DATABASE mydb FROM public; -- shut out the general public
GRANT CONNECT ON DATABASE mydb TO mygrp; -- since we revoked from public
GRANT USAGE ON SCHEMA public TO mygrp;
To assign "a user all privileges to all tables" like you wrote (I might be more restrictive):
GRANT ALL ON ALL TABLES IN SCHEMA public TO mygrp;
GRANT ALL ON ALL SEQUENCES IN SCHEMA public TO mygrp; -- don't forget those
To set default privileges for future objects, run for every role that creates objects in this schema:
ALTER DEFAULT PRIVILEGES FOR ROLE myusr IN SCHEMA public
GRANT ALL ON TABLES TO mygrp;
ALTER DEFAULT PRIVILEGES FOR ROLE myusr IN SCHEMA public
GRANT ALL ON SEQUENCES TO mygrp;
-- more roles?
Now, grant the group to the user:
GRANT mygrp TO myusr;
Related answer:
PostgreSQL - DB user should only be allowed to call functions
Alternative (non-standard) setting
Coming from MySQL, and since you want to keep privileges on databases separated, you might like this non-standard setting db_user_namespace. Per documentation:
This parameter enables per-database user names. It is off by default.
Read the manual carefully. I don't use this setting. It does not void the above.
Maybe you could give me an example that grants a specific user
select/insert/update/delete on all tables -- those existing and not
yet created -- of a specific database?
What you call a database in MySQL more closely resembles a PostgreSQL schema than a PostgreSQL database.
Connect to database "test" as a superuser. Here that's
$ psql -U postgres test
Change the default privileges for the existing user "tester".
ALTER DEFAULT PRIVILEGES IN SCHEMA public
GRANT INSERT, SELECT, UPDATE, DELETE ON TABLES
TO tester;
Changing default privileges has no effect on existing tables. That's by design. For existing tables, use standard GRANT and REVOKE syntax.
You can't assign privileges for a user that doesn't exist.
You can forget about the schema if you only use PUBLIC.
Then you do something like this: (see doc here)
GRANT { { SELECT | INSERT | UPDATE | DELETE | TRUNCATE | REFERENCES | TRIGGER }
[, ...] | ALL [ PRIVILEGES ] }
ON { [ TABLE ] table_name [, ...]
| ALL TABLES IN SCHEMA schema_name [, ...] }
TO { [ GROUP ] role_name | PUBLIC } [, ...] [ WITH GRANT OPTION ]
I don't want to grant rights to all users and all databases, as seems to be the conventional shortcut, because that approach compromises all databases when any one user is compromised. I host multiple database clients and assign each client a different login.
OK. When you assign tables to the correct role, the privileges granted will be role-specific and not to all users! Then you can decide who to give roles to.
Create a role for each database. A role can hold many users.
Then assign a client-username to the correct role.
Also assign your-username to each role if needed.
(1a) Not all of the tables have been created yet, or (1b) the tables have already been created.
OK. You can create tables later.
When you are ready, assign tables to the correct client role.
CREATE TABLE tablename();
CREATE ROLE rolename;
ALTER TABLE tablename OWNER TO rolename;
(2a) The user has not yet been created, or (2b) the user has already been created.
OK. Create usernames when you are ready. If your client needs more than one username simply create a second client-username.
CREATE USER username1;
CREATE USER username2;
(3a) Privileges have not yet been assigned to the user, or (3b) privileges were previously assigned to the user.
OK. When you are ready to give privileges, create the user and assign the correct role to her.
Use GRANT-TO command to assign roles to users.
GRANT rolename TO username1;
GRANT rolename TO username2;
(4a) The user only needs to insert, update, select, and delete rows, or (4b) the user also needs to be able to create and delete tables.
OK. You run these commands to add permissions to your users.
GRANT SELECT, UPDATE, INSERT, DELETE ON dbname TO role-or-user-name;
ALTER USER username1 CREATEDB;