SET Role doesn't work from Security Definer Function...

dipti shah <shahdipti1980@gmail.com> writes:

I have just noticed that "SET ROLE" doesn't work from security definer
function. I don;t know why but it clearly gives the error that SET role
doesn;t work in security definer context.

This is intentional because allowing it creates security holes.

If I create function in postgres user with Security Definer enabled, it will
allow to create any table with any foreign references etc...So I am setting
role to current_user in my function and then creating a table to make sure
that user has the appropriate privilege.

Well, if you are trying to set the role back to current, why don't you
just not have the function be security definer in the first place?

I suppose the answer to that is that you want it to do some things as
superuser and some things not. In which case, you need to refactor so
that those two classes of things are done by different functions.

regards, tom lane

You are correct Tom that I want to perform some portion of function as
postgres user and other portion as current user.

As per you suggestion I did refactor and separated the portion that needs to
be executed as superuser to another function. But the thing is PostGreSQL
recognize when I call this separated funtion from my original SECURITY
DEFINER function and gives the same error. :(

For your reference I did something like this:

1. Create Function foo1 .... (this is without SECURITY DEFINER where I am
using SET ROLE to current user).

2. Create Function foo2 with SECURITY DEFINER ...
spi_exe_query("select foo1()"); ==> Here it throws the error.

I am helpless now. Could you tell me what could be done in this situation?

Thanks,
Dipti
On Tue, Feb 23, 2010 at 2:04 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

dipti shah escribi�:

For your reference I did something like this:

1. Create Function foo1 .... (this is without SECURITY DEFINER where I am
using SET ROLE to current user).

2. Create Function foo2 with SECURITY DEFINER ...
spi_exe_query("select foo1()"); ==> Here it throws the error.

Shouldn't it be the other way around? The normal function calls the
security-definer one.

--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

No, I tried that but that can't be done in my requirements because my
function has to be run in super user context to create the table in schema
where normal users have only USAGE permissions. If I remove SECURITY DEFINER
then my stored procedure will be failed for all users by saying "permission
denied on schema myschema".

Moreover, I want to run only create table code in normal user context and
other things in stored procedure should be done in super user context.

I tried all possible ways but couldn't find to get out of this yet.

Thanks,
Dipti

On Tue, Feb 23, 2010 at 8:36 PM, Alvaro Herrera
<alvherre@commandprompt.com>wrote:

This issue is driving me crazy. Could any one please suggest me any
workaround?

For summary of issue,

1. I don't want any users to perform any action on mydb schema without
using my stored procedure. So I revoke ALL permissions from mydb schema and
assigned only USAGE permissions.
2. As my stored procedure allows creating table in mydb schema and users
have only USAGE permissions on mydb schama, I have to defined my stored
procedure with SECURITY DEFINER so that it allows to create table in mydb
schema.
3. To prevent creating unauthenticated foreign references to other
tables, I want to make sure that current user has the required permissions
to create table before creating table. For this I have to use SET ROLE to
current user but it is not allowed in SECURITY DEFINER context.

Any help would be much appreciated.

Thanks,
Dipti
On Tue, Feb 23, 2010 at 10:51 PM, dipti shah <shahdipti1980@gmail.com>wrote: