help about the function

[Zlatko Matić <zlatko.matic1@xxxxxxxxxxx>]

Hello!

 

I have implemented solution for enabling regular user (from group "ADMINS") to create new users in predefined groups, by your modified function:

 

CREATE OR REPLACE FUNCTION "public"."alter_group" (name, boolean, name, varchar, timestamp) RETURNS boolean AS
$body$
DECLARE
  l_group ALIAS FOR $1;
  l_create_user ALIAS FOR $2;
  l_username ALIAS FOR $3;
  l_password ALIAS FOR $4;
  l_validity ALIAS FOR $5;
  CMD VARCHAR;
  MIN_SUPER_USER INTEGER := 1;
BEGIN
IF (l_create_user NOTNULL) THEN
    IF (l_create_user) THEN
      CMD := 'CREATE USER "' || l_username || '" WITH PASSWORD ''' || l_password || ''' IN GROUP "' || l_group || '" VALID UNTIL ''' || l_validity || '''';
      EXECUTE CMD;
    ELSE
      CMD := 'DROP USER "' || l_username || '"';
      EXECUTE CMD;
    END IF;
    IF (SELECT COUNT(*) FROM "USER_GROUP_VIEW" WHERE "GroupName" ='{ADMINS}') < MIN_SUPER_USER THEN
      RAISE EXCEPTION 'At least % admin(s) in group ADMINS must be defined in order to create new user accounts.', MIN_SUPER_USER;
    END IF;
  END IF;
  RETURN TRUE;
END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY DEFINER;

 

Validity is set in the table public."VALIDITY" in the field "VALIDITY" timestamp. There is also a view called "VALIDITY_VIEW" which reads the actual validity value from the table. It returns only one row-one field:

CREATE OR REPLACE VIEW "VALIDITY_VIEW" AS
 SELECT "VALIDITY"."VALIDITY"
   FROM ( SELECT min("VALIDITY"."RV_ID") AS "RV_ID", "VALIDITY"."VALIDITY"
           FROM "VALIDITY"
          GROUP BY "VALIDITY"."RV_ID", "VALIDITY"."VALIDITY") sve;

 

ALTER TABLE "VALIDITY_VIEW" OWNER TO zmatic;

MS Access front-end calls this function through VBA code. Access creates a recordset on the base of the VALIDITY_VIEW to inspect the value of validity time, assigns it to a variable and then passes as the parameter l_validity to the server function "alter_group". It works nice, but I realized that it is not safe, because someone from the group "ADMINS" could create its own query in Access with different "validity" and execute it without restriction. Therefore I think that "l_validity" timestamp ($5) should not be input parameter for the function "alter_group", but rather declared variable that reads the value of validity from the table directly.

 

I tried to modify the function into something like this:

 

 

CREATE OR REPLACE FUNCTION "public"."alter_group" (name, boolean, name, varchar) RETURNS boolean AS
$body$
DECLARE
  l_group ALIAS FOR $1;
  l_create_user ALIAS FOR $2;
  l_username ALIAS FOR $3;
  l_password ALIAS FOR $4;
  l_validity timestamp;
  CMD VARCHAR;
  MIN_SUPER_USER INTEGER := 1;
BEGIN

 

l_validity := SELECT "VALIDITY"."VALIDITY" FROM ( SELECT min("VALIDITY"."RV_ID") AS "RV_ID", "VALIDITY"."VALIDITY" FROM "VALIDITY" GROUP BY "VALIDITY"."RV_ID", "VALIDITY"."VALIDITY") sve;

IF (l_create_user NOTNULL) THEN
    IF (l_create_user) THEN
      CMD := 'CREATE USER "' || l_username || '" WITH PASSWORD ''' || l_password || ''' IN GROUP "' || l_group || '" VALID UNTIL ''' || l_validity || '''';
      EXECUTE CMD;
    ELSE
      CMD := 'DROP USER "' || l_username || '"';
      EXECUTE CMD;
    END IF;
    IF (SELECT COUNT(*) FROM "USER_GROUP_VIEW" WHERE "GroupName" ='{ADMINS}') < MIN_SUPER_USER THEN
      RAISE EXCEPTION 'At least % admin(s) in group ADMINS must be defined in order to create new user accounts.', MIN_SUPER_USER;
    END IF;
  END IF;
  RETURN TRUE;
END;
$body$
LANGUAGE 'plpgsql' VOLATILE CALLED ON NULL INPUT SECURITY DEFINER;

 

..but it seems that I can't assign the value returned by query to l_validity directly (I could do it in Access by recordset)...How to modify the following in order to work ?

 

l_validity := SELECT "VALIDITY"."VALIDITY" FROM ( SELECT min("VALIDITY"."RV_ID") AS "RV_ID", "VALIDITY"."VALIDITY" FROM "VALIDITY" GROUP BY "VALIDITY"."RV_ID", "VALIDITY"."VALIDITY") sve;

 

Thank you in advance.

 

Zlatko