Four things a developer can do now to improve their applications #infosec posture.

Lets face it, we have deadlines to meet and millions of lines of code in production. I get it, I’ve been a working PL/SQL developer off and on for over 20 years. If we get into the habit of using some of the security features in the language along with some practices, we can improve the security of you code. So, lets get into it.

1) Use packages. Steve Feuerstein http://www.oracle.com/technetwork/issue-archive/index-087690.html has been saying for years to move those functions and procedures to packages and there is good security reasons to do that. If you have a SQL Injection bug in your application, I can get to ALL_SOURCE and read your code and if I can get to your code, I can find other exploits.

So we can read the code in Functions and Procedures.

1 SQL> select text from all_source where owner = user and name = 'PARSE_STRING'; 2 procedure parse_string(p_string varchar2) AS 3 CURSOR col_cur IS 4 select distinct (instr(p_string||',',',',1,level)) loc 5 FROM dual 6 CONNECT BY LEVEL <= LENGTH(REPLACE(p_string,','))+1 7 ORDER BY 1; 8 l_col varchar2(65); 9 BEGIN 10 for col_rec in col_cur 11 loop 12 l_col := substr(p_string, col_rec.loc, instr(p_string, col_rec.loc+1)); 13 dbms_output.put_line(l_col || 'col pos ' || col_rec.loc); 14 end loop; 15 end; 16 17 14 rows selected. 18 19 SQL> create user u2 identified by MY##56SecurePassword; 20 21 User created. 22 23 SQL> grant create session to u2; 24 25 Grant succeeded. 26 27 SQL> grant execute on parse_string to u2; 28 29 Grant succeeded. 30 31 SQL> conn u2@orcl 32 Enter password: 33 Connected. 34 SQL> select text from all_source where owner = 'RLOCKARD' 35 2 and name = 'PARSE_STRING'; 36 procedure parse_string(p_string varchar2) AS 37 CURSOR col_cur IS 38 select distinct (instr(p_string||',',',',1,level)) loc 39 FROM dual 40 CONNECT BY LEVEL <= LENGTH(REPLACE(p_string,','))+1 41 ORDER BY 1; 42 l_col varchar2(65); 43 BEGIN 44 for col_rec in col_cur 45 loop 46 l_col := substr(p_string, col_rec.loc, instr(p_string, col_rec.loc+1)); 47 dbms_output.put_line(l_col || 'col pos ' || col_rec.loc); 48 end loop; 49 end; 50 51 14 rows selected. 52 53 SQL> 54

Now when we put this into a package, the only thing I can extract from it is the package specification.

First lets put it into a package.

1 SQL> sho user 2 USER is "RLOCKARD" 3 SQL> create or replace package rlockard.utility AS 4 procedure parse_string(p_string varchar2); 5 end; 6 / 7 8 Package created. 9 10 SQL> create or replace package body rlockard.utility AS 11 12 procedure parse_string(p_string varchar2) IS 13 CURSOR col_cur IS 14 select distinct (instr(p_string||',',',',1,level)) loc 15 FROM dual 16 CONNECT BY LEVEL <= LENGTH(REPLACE(p_string,','))+1 17 ORDER BY 1; 18 l_col varchar2(65); 19 BEGIN 20 for col_rec in col_cur 21 loop 22 l_col := substr(p_string, col_rec.loc, instr(p_string, col_rec.loc+1)); 23 sys.dbms_output.put_line(l_col || 'col pos ' || col_rec.loc); 24 end loop; 25 end; 26 end; 27 / 28 29 Package body created. 30 31 SQL>

Now, lets test to see what we can see.

1 SQL> grant execute on utility to u2; 2 3 Grant succeeded. 4 5 SQL> conn u2@orcl 6 Enter password: 7 Connected. 8 SQL> select text from all_source where owner = 'RLOCKARD' 9 and name = 'UTILITY'; 10 2 11 TEXT 12 -------------------------------------------------------------------------------- 13 package utility AS 14 procedure parse_string(p_string varchar2); 15 end; 16

As we can see, now you only get the package specification. This is really more that I would like to get out, but it’s much better than getting all your source code.

2) Split up your packages into smaller packages based on function. I normally split them up by UTILITY, SENSITIVE and NON SENSITIVE. If there are functions / procedures against sensitive tables those will go into the sensitive packages. You can further break down you sensitive packages. ie: CUSTOMER_API_PKG that would be your interface into your customers table.

Here is a good post by Steve Feuerstein on breaking packages down and keeping them compatible with existing code. http://www.oracle.com/technetwork/issue-archive/2015/15-jan/o15plsql-2398996.html

3) Limit the execution rights to a package and what a user can do with a package.

3a) We have been granting execute to packages for decades now. Then Oracle 11g gave us Invoker and Definer rights. When you create a package and don’t specify invoker or definer rights, the package is created with definer rights as the default. That’s all well and good, but let’s think this through. If I execute a package with definer rights and that package updates the customers table, even thought I don’t have update on the customers table, the package will work.

1 SQL> create or replace package rlockard.cust_api AS 2 function update_customers_credit_limit(pID in number, pCredit in number) return number; 3 end; 4 / 5 Package created. 6 7 SQL> create or replace package body rlockard.cust_api AS 8 9 function update_customers_credit_limit(pID in number, pCredit in number) return number is 10 retVal number; 11 begin 12 update customers set credit = pCredit where id = pId; 13 return 1; 14 exception when no_data_found 15 then 16 retVal := helpdesk.utility.log_error(pPkg => $$PLSQL_UNIT, pLine => $$PLSQL_LINE, 17 pParm => 'pID = ' || to_char(iID) || 18 ' pAmount= ' || to_char(pCredit), 19 pErr => sqlcode); 20 return retVal * -1; -- we are flipping the sign to indacate it's an error to caller. 21 end; 22 end; 23 / 24 Package body created. 25 SQL> 26

I am going to grant execute to the user U2 that we create earlier and test this.

1 SQL> grant execute on rlockard.cust_api to u2; 2 3 Grant succeeded. 4 5 SQL> conn u2@orcl 6 Enter password: 7 Connected. 8 SQL> declare 9 2 x number; 10 3 begin 11 4 x:=rlockard.cust_api.update_customers_credit_limit(pId => 1770, pCredit => 1000000); 12 5 end; 13 6 / 14 15 PL/SQL procedure successfully completed. 16 17 SQL> select credit from rlockard.customers where id = 1770; 18 select credit from rlockard.customers where id = 1770 19 * 20 ERROR at line 1: 21 ORA-00942: table or view does not exist 22 23 24 SQL> conn rlockard@orcl 25 Enter password: 26 Connected. 27 SQL> select credit from rlockard.customers where id = 1770; 28 29 CREDIT 30 ---------- 31 1000000 32 33 SQL> 34

Did you expect that to happen?  How are we going to tighten this down. We are going to set the package to use invokers rights. By adding AUTHID CURRENT_USER to the package specification, the package executes with U2’s rights. U2 does not have any rights on the customers table, the package fails with ORA-00942: table or view does not exists.

1 SQL> create or replace package rlockard.cust_api 2 AUTHID CURRENT_USER 3 AS 4 function update_customers_credit_limit(pID in number, pCredit in number) return number; 5 end; 6 / 7 2 3 4 5 6 8 Package created. 9 10 11 SQL> conn u2@orcl 12 Enter password: 13 Connected. 14 SQL> declare 15 x number; 16 begin 17 x := rlockard.cust_api.update_customers_credit_limit(pId => 1770, pCredit => 2500000); 18 exception when others then 19 sys.dbms_output.put_line(sqlerrm); 20 end; 21 / 22 ORA-00942: table or view does not exist 23 24 SQL> conn rlockard@orcl 25 Enter password: 26 Connected. 27 SQL> select credit from customers where id = 1770; 28 29 CREDIT 30 ---------- 31 1000000 32 SQL> 33

3b) In Oracle 12c we were given the ability to grant roles to packages. (procedures and functions too, but you should be using packages) Now, when we have sensitive tables in another schema, we can create a role that a package needs and grant that role to a package.

1 CREATE ROLE update_customers; 2 3 grant update_customers to rlockard; 4 5 GRANT SELECT 6 ON customers 7 TO update_customers; 8 9 GRANT update_customers TO PACKAGE cust_api; 10 11 declare 12 x number; 13 begin 14 x := rlockard.cust_api.update_customers_credit_limit(pId => 1770, pCredit => 2500000); 15 exception when others then 16 sys.dbms_output.put_line(sqlerrm); 17 end; 18 /

3c) Oracle 12c also gave us the accessible by clause. This creates a white list of the packages that can call a package. This way you are narrowing down the ways a package can get called, creating a trusted path to your secure data. So here the public package can call the private package, but if anything else tries to call it a PLS-00904 error will be raised.

accessable_by

1 SQL> create or replace package public_package AS 2 procedure update_customers(pId in number, 3 pColumn in varchar2, 4 pValue in varchar2); 5 end; 6 / 7 8 Package created. 9 10 SQL> create or replace package body public_package as 11 procedure update_customers(pId in number, 12 pColumn in varchar2, 13 pValue in varchar2) IS 14 x number; -- we know it's a function that returs a number. 15 begin -- this is simplistic to demo accessable_by 16 if pColumn = 'CREDIT' then 17 x := rlockard.cust_api.update_customers_credit_limit(pId => pId, pCredit => pValue); 18 end if; 19 end; 20 end; 21 / 22 23 Package body created. 24 25 SQL> create or replace package rlockard.cust_api 26 accessible by (public_package) AS 27 function update_customers_credit_limit(pID in number, pCredit in number) return number; 28 end; 29 / 30 31 Package created. 32 33 SQL> 34 35 SQL> declare 36 x number; 37 begin 38 x := rlockard.cust_api.update_customers_credit_limit(pId => 1770, pCredit => 2500000); 39 exception when others then 40 sys.dbms_output.put_line(sqlerrm); 41 end; 42 / 43 x := rlockard.cust_api.update_customers_credit_limit(pId => 1770, pCredit => 2500000); 44 * 45 ERROR at line 4: 46 ORA-06550: line 4, column 8: 47 PLS-00904: insufficient privilege to access object CUST_API 48 ORA-06550: line 4, column 3: 49 PL/SQL: Statement ignored 50 51 52 SQL> begin 53 public_package.update_customers(pId => 1771, pColumn => 'CREDIT', pValue => '200'); 54 end; 55 / 56 57 PL/SQL procedure successfully completed. 58 59 SQL> 60

But when we call it from the package in the accessible by clause, then it works fine. Again, we are limiting the paths to get to the sensitive information.

4a) We are getting down to the meat of what every shop should be doing. Reviewing code. You should be looking for dynamic code that is concatenating variables together. This is a painfully bad piece of code with a major SQL Injection bug.

1 create or replace PROCEDURE UserLogin 2 (p_email logins.email%type DEFAULT NULL, 3 p_password logins.password%type DEFAULT NULL) 4 AS 5 6 STMT CONSTANT VARCHAR2(4000) := 7 'SELECT email 8 FROM logins 9 WHERE email = ''' || p_email || 10 ''' AND password = ''' || p_password || ''''; 11 12 l_result logins.email%type; 13 BEGIN 14 15 dbms_output.put_line ('SQL STMT: ' || STMT); 16 17 EXECUTE IMMEDIATE STMT INTO l_result; 18 19 dbms_output.put_line ('Logon succeeded.'); 20 21 EXCEPTION WHEN OTHERS THEN 22 null; -- OH NO HE DID NOT 23 END UserLogin;

How would I fix this. Well, lets’ change the dynamic SQL and put in some bind variables. We can still do a lot more with this code, but this fixes the SQL Injection bug and a couple other issues.

1 create or replace function UserLogin2 2 (p_email logins.email%TYPE DEFAULT NULL, 3 p_password logins.PASSWORD%TYPE DEFAULT NULL) 4 RETURN NUMBER AS 5 kount number; -- a dumb variable to hold a count 6 BEGIN 7 8 SELECT count(*) 9 INTO kount 10 FROM logins 11 WHERE email = p_email 12 and password = p_password; 13 14 IF kount = 1 THEN 15 sys.dbms_output.put_line ('Logon succeeded.'); 16 RETURN kount; 17 ELSE 18 return -1; 19 end if; 20 21 END UserLogin2;

Now you will find I love code reviews. Frequently we learn a way to do something and because it works, we continue doing it. Heck, I loved cursor for loops until I learned better in a code review. Code reviews should be approached as learning opportunities. You are going to learn a lot more tricks reading other peoples code and you may catch something that will improve the security of your system.

So in review the steps you can do now to improve the security posture of your applications are: Control the rights to executing code. Put everything in packages. Split up your packages. Do code reviews.