Web应用程序的PostgreSQL受限权限 [英] Restricted PostgreSQL permissions for web app

问题描述

目标

创建一个由三个用户组成的数据库并限制他们的特权（我只是大声思考，所以我的用户分离也需要纠正）： / p>

1. 超级用户-该用户允许对数据库进行最初始的配置。创建应用程序数据库，创建其他用户，设置他们的权限。默认的 postgres 超级用户对我有用，所以这一步完成了。


2. 管理员-该用户只能访问创建的数据库在供应期间。管理员可以 CRUD 所有表中的所有数据，还可以CRUD表等。 仅此数据库的超级用户类型的情况。在更新应用程序时，管理员是自动化工具用来处理数据库迁移的用户。


3. 应用程序用户-该用户最终是支持Web应用程序功能的用户。请注意，这与网页等上的用户无关-这是服务器利用其运行查询，插入和删除数据的用户。我明确地不希望该用户能够修改任何权限，也不希望创建/销毁表或索引或任何结构化的权限。

我尝试过的事情

首先，查看PostgreSQL文档（通常非常好），页面上几乎让我leaves目了。在花了几个小时阅读有关PostgreSQL角色和特权的信息后，我通常感到困惑。我认为通过更多的工作，我可以确定管理员用户想要的内容，但是我对应用程序用户的了解非常有限。我到此为止（命名和密码都只是占位符）：

  $ psql -U postgres 
 postgres =＃使用密码 password创建用户 app-admin； 
创建角色
 postgres =＃使用密码 password创建用户 app-user； 
创建角色
 postgres =＃使用所有者 app-admin创建数据库 test-database; 
创建数据库
 postgres =＃ c测试数据库 
现在，您以用户 postgres连接到数据库 test-database。 
 test-database =＃DROP SCHEMA public; 
 DROP SCHEMA 
 test-database =＃创建模式 app授权 app-admin; 
创建架构
  

这就是我不确定的地方。我觉得我想避免的答案是默认情况下撤消所有内容，然后枚举在所有不同对象上所有不同级别需要的所有特权。我试图避免这种情况，因为我一直不知道那里需要什么。如果最终找到答案，那么我只需要弯腰阅读更多的内容，但是通常当我开始沿着这样的道路走时，我会错过一些东西。

问题

如何限制 app-user 的特权，使他们无法修改任何结构数据（例如，不能添加或销毁表），但可以对行进行连接和执行任何操作（行级安全性甚至不在我的雷达范围内）。这种普通的特权模型与PostgreSQL期望的不是真的同步吗？我觉得如果我必须遍历该赠予页面上的每个选项来完成类似的事情，我会丢失一些东西-无论是我最初这样做的动力还是我打算采取的手段

上下文

我正在尝试构建我的第一个端到端Web应用程序。我已经完成了足够的常规软件开发和Web应用程序开发，现在我想了解我通常认为理所当然的部分。我正在尝试设置PostgreSQL服务器，同时牢记最低特权原则。 / p>

侧边任务

我没有在仅加入开发团队的Web应用程序上看到此操作，尽管它们通常很小，并且不常用。这样做实际上有什么作用吗？是否有人有令人信服的理由说明为什么要做这样的事情，或者为什么这是一个坏的或无效的主意？我的假设是，如果最终导致SQL注入漏洞，那么这将减轻损害，因为数据库用户的访问权限有限。

我在该主题上发现的整洁文章：

• http://www.ibm.com/developerworks/opensource/ library / os-postgresecurity / index.html


• PDF警告： https://wiki.postgresql.org/images/d/d1/Managing_rights_in_postgresql.pdf


• < a href = https://www.digitalocean.com/community/tutorials/how-to-use-roles-and-manage-grant-permissions-in-postgresql-on-a-vps--2 rel = noreferrer> https://www.digitalocean.com/community/tutorials/how-to-use-roles-and-manage-grant-permissions-in-postgresql-on-a-vps--2


• http：// blog。 2ndquadrant.com/auditing-users-and-roles-in-postgresql/

解决方案

我将回答您的附带要求首先要问的问题：

您的担心和担忧完全正确，设计应用程序的每个人都应该考虑同样的事情。其他一切都是草率和粗心的。

为减轻成功的SQL注入攻击可能造成的损害，您绝对应该采用最小特权原则。

>

建立符合您要求的系统应该非常简单。

我将使用您的实例，除了我将使用下划线而不是负号。最好在对象名称中使用小写字母，下划线和数字，因为这样会使您的生活更轻松。

  / *创建数据库* / 
 postc postgres postgres 
使用所有者app_admin创建数据库test_database； 
 \ c test_database postgres 
 
 / *删除公共模式；其他侵入性较小的选项是
在公共场所从公共场所撤消所有* / 
 DROP SCHEMA public; 
 / *创建应用程序架构* / 
 CREATE SCHEMA app AUTHORIZATION app_admin; 
 / *进一步的操作将不需要超级用户访问* / 
 testc test_database app_admin 
 / *允许app_user访问，但不能在架构中创建对象* / 
 GRANT在SCHEMA应用上向APP_USER使用； 
 
 / *不允许PUBLIC执行app_admin创建的功能* / 
更改角色默认权限app_admin 
从PUBLIC的函数上调用执行； 
 
 / *假定应允许app_user对该模式中所有表中的数据进行任何操作
，允许访问app_admin将在此处创建的所有
对象* / 
在SCHEMA应用程序中为角色app_admin更改默认权限
将选择，插入，更新，删除表上的内容授予APP_USER； 
 SCHEMA应用程序中角色app_admin的其他默认权限
格兰特选择，对app_user的序列使用； 
 SCHEMA应用程序中角色app_admin的其他默认权限
授权对app_user执行功能； 
  

但是如果您最不重视原则，则应该单独授予表权限，例如不允许 app_user 删除表中的 DELETE 和 UPDATE 数据用户无需这样做。

Goal

Create a database with three users and restrict their privileges (I'm just thinking out loud, so my user separation is also open to correction):

1. Superuser - this user allows for the very initial provisioning of the database. Create the application database, create the other users, set their privileges. Default postgres superuser works for me, so this one is done.
2. Administrator - this user has access only to the database that was created during provisioning. Administrator can CRUD all data in all tables, and can also CRUD tables, etc. "Superuser for only this database" type of situation. When the application is being updated, the administrator is the user used by automated tooling to handle database migrations.
3. App user - this user is ultimately the one who supports the web app's functionality. Note this has nothing to do with users on web pages etc - this is the user the server leverages to run queries, insert and remove data. I explicitly do not want this user to be able to modify permissions of anything, nor create/destroy tables or indices or anything structural.

What I've tried

First off, looking at the (generally excellent) PostgreSQL documentation, the page on Grant pretty much leaves me cross-eyed. After spending a few hours reading about PostgreSQL roles and privileges I'm generally confused. I think with a bit more work I'll be able to nail down what I want for the admin user, but I'm pretty stuck on the "app user". I've gotten about this far (naming and passwords are all just placeholders):

$ psql -U postgres
postgres=# CREATE USER "app-admin" WITH PASSWORD 'password';
CREATE ROLE
postgres=# CREATE USER "app-user" WITH PASSWORD 'password';
CREATE ROLE
postgres=# CREATE DATABASE "test-database" WITH OWNER "app-admin";
CREATE DATABASE
postgres=# \c "test-database"
You are now connected to database "test-database" as user "postgres".
test-database=# DROP SCHEMA "public";
DROP SCHEMA
test-database=# CREATE SCHEMA "app" AUTHORIZATION "app-admin";
CREATE SCHEMA

And here's where I get unsure. I feel like the answer I'm trying to avoid is "revoke everything by default then enumerate all the privileges you'll need at all the different levels on all the different objects". I'm trying to avoid that because I straight up don't know what I need there. If that ends up being the answer, then I'll just have to hunker down and read a bunch more, but generally when I start going down paths like that I've missed something.

Issues

How do I restrict privileges for app-user so they are unable to modify any structural data (e.g. cannot add or destroy tables) but are able to connect and do anything with rows (row level security is not even on my radar). Is this general model of privileges not really in sync with what PostgreSQL expects? I feel like I'm missing something if I have to walk through every option on that "grant" page to accomplish something like this - whether it be my motivation for doing it in the first place or the means by which I'm going about it.

Context

I'm trying to build my first end-to-end web application. I've done enough general software development and web app development, now I'm trying to understand the pieces that I generally take for granted day to day. I'm trying to set up a PostgreSQL server while keeping the principle of least privilege in mind.

Side-quest

I haven't seen this done on web apps where I have simply joined the development team, although they're generally small and not heavily used. Does doing this actually accomplish anything? Does anyone have compelling reasons for why to do something like this, or why it's a bad or ineffective idea? My assumption was that if I ultimately ended up with a SQL injection vulnerability, this would mitigate the damage because the database user would have limited access. Is that misguided?

Neat articles I've found on the subject:

• http://www.ibm.com/developerworks/opensource/library/os-postgresecurity/index.html
• PDF WARNING: https://wiki.postgresql.org/images/d/d1/Managing_rights_in_postgresql.pdf
• https://www.digitalocean.com/community/tutorials/how-to-use-roles-and-manage-grant-permissions-in-postgresql-on-a-vps--2
• http://blog.2ndquadrant.com/auditing-users-and-roles-in-postgresql/

解决方案

I'll answer your “side-quest” question first:

you are completely right with your worries and concerns, and everybody who designs an application should think about the same things. Everything else is sloppy and careless.

To mitigate the damage that can be caused by a successful SQL injection attack, you should definitely employ the principle of least privilege.

It should be quite simple to set up a system that matches your requirements.

I'll use the object names from your exaple, except that I'll use underscores instead of minuses. It is good practive to use only lower case letters, underscores and numbers in object names, since it will make your life easier.

/* create the database */
\c postgres postgres
CREATE DATABASE test_database WITH OWNER app_admin;
\c test_database postgres

/* drop public schema; other, less invasive option is to
   REVOKE ALL ON SCHEMA public FROM PUBLIC */
DROP SCHEMA public;
/* create an application schema */
CREATE SCHEMA app AUTHORIZATION app_admin;
/* further operations won't need superuser access */
\c test_database app_admin
/* allow app_user to access, but not create objects in the schema */
GRANT USAGE ON SCHEMA app TO app_user;

/* PUBLIC should not be allowed to execute functions created by app_admin */
ALTER DEFAULT PRIVILEGES FOR ROLE app_admin
   REVOKE EXECUTE ON FUNCTIONS FROM PUBLIC;

/* assuming that app_user should be allowed to do anything
   with data in all tables in that schema, allow access for all
   objects that app_admin will create there */
ALTER DEFAULT PRIVILEGES FOR ROLE app_admin IN SCHEMA app
   GRANT SELECT, INSERT, UPDATE, DELETE ON TABLES TO app_user;
ALTER DEFAULT PRIVILEGES FOR ROLE app_admin IN SCHEMA app
   GRANT SELECT, USAGE ON SEQUENCES TO app_user;
ALTER DEFAULT PRIVILEGES FOR ROLE app_admin IN SCHEMA app
   GRANT EXECUTE ON FUNCTIONS TO app_user;

But if you take the principle of least seriously, you should grant table permissions individually and e.g. not allow app_user to DELETE and UPDATE data in tables where there is no need for the user to do so.

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