连接到数据库后切换角色 [英] Switch role after connecting to database

问题描述

在初始连接后与postgres进行交互时，是否可以更改用户正在使用的postgresql角色?

Is it possible to change the postgresql role a user is using when interacting with postgres after the initial connection?

该数据库将在Web应用程序中使用，我想在具有连接池的表和模式上采用数据库级规则.通过阅读postgresql文档，如果我最初以超级用户角色作为用户连接，则似乎可以切换角色，但是我希望最初以最小的权限作为用户连接并根据需要进行切换.切换时不必指定用户密码就可以了(事实上，我更喜欢这样).

The database(s) will be used in a web application and I'd like to employ database level rules on tables and schemas with connection pooling. From reading the postgresql documentation it appears I can switch roles if I originally connect as a user with the superuser role, but I would prefer to initially connect as a user with minimal permissions and switch as necessary. Having to specify the user's password when switching would be fine (in fact I'd prefer it).

我想念什么?

更新:我已经按照@Milen的建议尝试了SET ROLE和SET SESSION AUTHORIZATION，但是如果用户不是超级用户，这两个命令似乎都不起作用:

Update: I've tried both SET ROLE and SET SESSION AUTHORIZATION as suggested by @Milen however neither command seems to work if the user is not a superuser:

$ psql -U test
psql (8.4.4)
Type "help" for help.

test=> \du test
          List of roles
 Role name | Attributes |   Member of    
-----------+------------+----------------
 test      |            | {connect_only}

test=> \du test2
          List of roles
 Role name | Attributes |   Member of    
-----------+------------+----------------
 test2     |            | {connect_only}

test=> set role test2;
ERROR:  permission denied to set role "test2"
test=> \q

推荐答案

--create a user that you want to use the database as:

create role neil;

--create the user for the web server to connect as:

create role webgui noinherit login password 's3cr3t';

--let webgui set role to neil:

grant neil to webgui; --this looks backwards but is correct.

webgui现在位于neil组中，因此webgui可以调用set role neil.但是，webgui不会继承neil的权限.

webgui is now in the neil group, so webgui can call set role neil . However, webgui did not inherit neil's permissions.

稍后，以webgui登录:

Later, login as webgui:

psql -d some_database -U webgui
(enter s3cr3t as password)

set role neil;

webgui不需要superuser权限.

您要在数据库会话开始时set role并在会话结束时将其重置.在Web应用程序中，这相当于分别从数据库连接池中获取连接并释放它.这是一个使用Tomcat的连接池和Spring Security的示例:

You want to set role at the beginning of a database session and reset it at the end of the session. In a web app, this corresponds to getting a connection from your database connection pool and releasing it, respectively. Here's an example using Tomcat's connection pool and Spring Security:

public class SetRoleJdbcInterceptor extends JdbcInterceptor {

    @Override
    public void reset(ConnectionPool connectionPool, PooledConnection pooledConnection) {

        Authentication authentication = SecurityContextHolder.getContext().getAuthentication();

        if(authentication != null) {
            try {

                /* 
                  use OWASP's ESAPI to encode the username to avoid SQL Injection. Can't use parameters with SET ROLE. Need to write PG codec.

                  Or use a whitelist-map approach
                */
                String username = ESAPI.encoder().encodeForSQL(MY_CODEC, authentication.getName());

                Statement statement = pooledConnection.getConnection().createStatement();
                statement.execute("set role \"" + username + "\"");
                statement.close();
            } catch(SQLException exp){
                throw new RuntimeException(exp);
            }
        }
    }

    @Override
    public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {

        if("close".equals(method.getName())){
            Statement statement = ((Connection)proxy).createStatement();
            statement.execute("reset role");
            statement.close();
        }

        return super.invoke(proxy, method, args);
    }
}

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