I want to create a read-only user in PostgreSQL.
The intention is to have a publicly accessible data explorer, where users can write custom SQL queries.
I do this to create the user:
CREATE USER MyReadOnlyUser WITH ENCRYPTED PASSWORD 'MY_WEAK_PASSWORD';
GRANT ALL PRIVILEGES ON DATABASE "MY_DB_NAME" to MyReadOnlyUser;
GRANT ALL ON SCHEMA public TO MyReadOnlyUser;
GRANT SELECT ON ALL TABLES IN SCHEMA public TO MyReadOnlyUser;
The intention is to give the user SELECT access to all tables, then revoke select access on the sensitive tables, and then the user can run custom queries with that db user, without any need for me to sanitize input.
Especially, he may not:
insert, delete, truncate, drop table, drop database, create table, create function/procedure, see/execute/create/drop stored procedure / functions. etc.
Sooo - now my question:
Why does this user have access to information_schema ?
It wasn't granted access to any views, and not to the schema information_schema either...
Why does this user have access to information_schema
I think select privilege is granted to PUBLIC by default on information_schema.
You should be able to do:
revoke all on all tables in schema information_schema from public;
You probably also need to revoke the select privilege on views/tables in the pg_catalog schema. But I'm not sure what this will break if e.g. psql or other client tools cannot access that information.
Related
I’m pulling data from mysql ec2 instances, to s3 buckets, then creating views in redshift. I want to create database users who can only query and see certain views created specifically for them in Redshift. I have example code below that I use to create the user, view, and grant access. The issue I have is that I also have to grant access to the underlying schema the view is created from, which means the user can see and query tables in that schema. Also the user can see other schemas in the database, even ones they can’t query. Is there a way to only grant users to specific views, and make it so they can’t see other schemas they don’t have access to?
Code:
--create schema
create schema tst_user_schema;
--create view in schema
create view tst_user_schema.inventory_report_customer as (
select * from user341.inventory_report_customer
)
with no schema binding;
--creating user
CREATE USER tstuser PASSWORD 'tstPassword';
--grant access
GRANT USAGE ON SCHEMA tst_user_schema TO tstuser;
--grant read access to all tables in schema
GRANT SELECT ON ALL TABLES IN SCHEMA tst_user_schema TO tstuser;
--grant access
GRANT USAGE ON SCHEMA user341 TO tstuser;
--grant read access to all tables in schema
GRANT SELECT ON ALL TABLES IN SCHEMA user341 TO tstuser;
--grant access
GRANT USAGE ON SCHEMA tst_user_schema TO tstuser;
--grant read access to all tables in schema
GRANT SELECT ON ALL TABLES IN SCHEMA tst_user_schema TO tstuser;
to recap:
schema user341 - contains source tables, user should not be able to select from tables in this schema. You also want to hide it form the user
tst_user_schema - contains views user is supposed to be able to select from.
Looking at your GRANT statements, you're granting user unnecessarily SELECT permission on ALL TABLES IN SCHEMA user341. For views to work you only need to GRANT USAGE on that schema.
So REVOKE those permissions, and user should not be able to select.
REVOKE SELECT ON ALL TABLES IN SCHEMA user341 FROM tstuser;
Tip: to easily test permissions, you can start a session as tstuser using SET SESSION AUTHORIZATION directive and then test which statements are allowed and which not.
SET SESSION AUTHORIZATION tstuser
Regarding schema visibility - unfortunately there's no way to hide or forbid user from seening all tables and columns in all schemas. One can only restrict access to data.
I would like to know how the privilege SELECT ANY TABLE works internally in Oracle.
Is it treated as a single privilege? Or is it equivalent to make a GRANT SELECT ON MyTable TO MyUser for each table?
As example, I would like to know if this work :
GRANT SELECT ANY TABLE TO PUBLIC;
REVOKE ALL ON MY_TABLE FROM PUBLIC;
Would I still have access to MY_TABLE from any user after those queries?
Yes, all users would still be able to query MY_TABLE.
You are looking at different privilege types:
The main types of user privileges are as follows:
System privileges—A system privilege gives a user the ability to perform a particular action, or to perform an action on any schema objects of a particular type. For example, the system privilege CREATE TABLE permits a user to create tables in the schema associated with that user, and the system privilege CREATE USER permits a user to create database users.
Object privileges—An objectprivilege gives a user the ability to perform a particular action on a specific schema object. Different object privileges are available for different types of schema objects. The privilege to select rows from the EMPLOYEES table or to delete rows from the DEPARTMENTS table are examples of object privileges.
SELECT ANY TABLE is a system privilege that allows the grantee to:
Query tables, views, or materialized views in any schema except SYS. Obtain row locks using a SELECT ... FOR UPDATE.
When you grant that it is a standalone single privilege, visible in dba_sys_privs. When Oracle decides if the user is allowed to access a table it can look first at system privleges, and only goes on to look for specific object privileges (visible in dba_tab_privs) if there isn't a system privilege that allows the action being performed.
System privileges are not translated into individual privileges on each object in the database - maintaining that would be horrible, as creating a new object would have to automatically figure out who should be granted privileges on it based on the system privilege; and it would mean that you couldn't tell the difference between that and individually granted privileges. So, for instance, if you explicitly granted select privs on a specific table, then the user was granted SELECT ANY TABLE, and then they had SELECT ANY TABLE revoked - what happens to the previous explicit grant?
Your scenario is basically the same, except you've specifed all privileges on the object to be revoked. If those are the only two commands involved then PUBLIC has no explicit privileges on MY_TABLE so revoking doesn't really do anything; but if any explicit privileges on that table had been granted then they would be revoked. That has no impact on the higher-level SELECT ANY TABLE system privileg though.
Privileges are cummulative; revoking a privilege on a specific object doesn't block access to that object, it just removes one possible access route.
Incidentally, hopefully you've used a contrived example, as such powerful system privileges should be granted sparingly and only when really needed. Letting any user query any table in your database potentially blows a big hole in the security model. Again from the docs:
Oracle recommends that you only grant the ANY privileges to trusted users
and
Oracle recommends against granting system privileges to PUBLIC.
and read more in the database security guide.
I am managing a database that has a number of schemas. I am having some difficulty with setting privileges and would like to request some help.
I have the schema called schemaA and a group_role db_writer
I use the following sql:
GRANT USAGE ON SCHEMA schemaA TO db_writer;
GRANT UPDATE, INSERT, SELECT, DELETE ON ALL TABLES IN SCHEMA schemaA TO db_writer;
However, the db_writer is unable to create views. They are returned with a permission denied error. Also, when I create views, she is then unable to select them...and I have to set the priviliges again for that view.
It was my understanding the views were treated as tables with respect to privileges...and if one is granted certain permissions to all tables in a schema this would apply to views also.
What am I missing? Any advice appreciated.
The problem is USAGE does not allow users to create objects within the database.
Try
GRANT USAGE, CREATE ON SCHEMA schemaA TO db_writer
Edit:
New objects will get default privileges, for the user to have those privileges for objects created in the future you can do it as:
ALTER DEFAULT PRIVILEGES IN SCHEMA schemaA GRANT UPDATE, INSERT, SELECT, DELETE ON TABLES TO db_writer;
ALTER DEFAULT PRIVILEGES IN SCHEMA schemaA GRANT SELECT ON TABLES TO db_reader;
Check this answer for more info
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;
How do you grant read/select access on all functions and views to an arbitrary user?
I use psql --user=postgres -d mydb -f myview.sql to create several functions and views, and then I run:
GRANT ALL PRIVILEGES ON DATABASE mydb TO myuser;
Having been granted all privileges, I would expect myuser to now have access to the functions and views created by the postgres user. However, when I try and access them with myuser, I get a "permission denied for relation..." error. Why is this?
The reason is that you need additional privileges to access a view or table. Privileges on the database do not cover access to all objects in it.
It is different with functions: EXECUTE privilege is granted to public by default. But the function is executed with the privileges of the current user. You may be interested in the SECURITY DEFINER modifier for CREATE FUNCTION. But normally it is enough to grant SELECT on involved tables.
Per documentation about default privileges:
Depending on the type of object, the initial default privileges might
include granting some privileges to PUBLIC. The default is no public
access for tables, columns, schemas, and tablespaces; CONNECT
privilege and TEMP table creation privilege for databases; EXECUTE
privilege for functions; and USAGE privilege for languages.
You may be interested in this DDL command (requires Postgres 9.0 or later):
GRANT SELECT ON ALL TABLES IN SCHEMA public TO myuser;
While connected to the database in question, of course (see #marcel's comment below), and as a user with sufficient privileges. You may also be interested in the setting DEFAULT PRIVILEGES:
Grant all on a specific schema in the db to a group role in PostgreSQL
More detailed answer how to manage privileges:
How to manage DEFAULT PRIVILEGES for USERs on a DATABASE vs SCHEMA?
pgAdmin has a feature for more sophisticated bulk operations:
Or you can query the system catalogs to create DDL statements for bulk granting / revoking ...