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  1.  Home
  2. RPG400-L
  3. August 2011

Re: Reduce large amount of logicals in SUBFL pgm, take in another direction

Charles,

Whilst I obviously understand the problem of SQL injection, it is
*much*less of a problem with RPG than with e.g. C-like languages, for
many of the
same reasons that buffer overflows don't really hit RPG - because we don't
use open-ended strings with variable lengths to anything like the same level
that those other languages do.

For instance, using your example, the user has to have defined
userEnteredValue as a string of a certain length. If it's e.g. 10
characters, it's *very* hard to do much damage. Obviously if it's a long
character string, it gets more likely that bad things can happen, but that's
rare, especially ina select statement.

Another reason, of course, is that if the program is an RPG interactive
program, you can be pretty sure that it's not being accessed across the web.
With a C program (not an IBM i interactive C program, obviously, but who
writes those anyway?), there is always the risk that it can be called from
lots of different places other than those where it was designed to be called
from.

The reason I use parameters is simply because it's "good practice". Plus, I
won't get hassled on this forum :)

Look, I think Gary should use parameters instead of direct concatenation,
but that doesn't mean that his application is currently *actually* unsafe -
just that it *could* be, in ways that parameters would mitigate.

Rory

On Mon, Aug 1, 2011 at 12:36 PM, Charles Wilt <charles.wilt@xxxxxxxxx>wrote:

Fine...

So tell me how this could be safe?
wSqlStmt = 'SELECT * FROM MYTABLE WHERE MYFLD = ' + userEnteredValue;

Charles

On Mon, Aug 1, 2011 at 3:27 PM, Monnier, Gary <Gary.Monnier@xxxxxxxxx>
wrote:
Charles,

With respect, I do understand the issue. I simply disagree with your
assessment.

Gary



-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx [mailto:
rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Monday, August 01, 2011 11:48 AM
To: RPG programming on the IBM i / System i
Subject: Re: Reduce large amount of logicals in SUBFL pgm,take in another
direction

Gary,

I wouldn't call this a matter of disagreement ...

With respect, you obviously don't understand the issue....but it's an
important issue. I'd be happy to clarify the problem, but I don't know any
better way to explain it. Perhaps Scott, Joe or Jon can jump in with a
better explanation.

Or perhaps you can explain why you think your code is safe because it's
in a module...

You might start by posting the actual code, along with sample usage...

Perhaps then somebody will be able to give you a concrete example of how
it could be misued.

Sincerely,
Charles

On Mon, Aug 1, 2011 at 2:25 PM, Monnier, Gary <Gary.Monnier@xxxxxxxxx>
wrote:
Charles,

So we choose to disagree.

Gary


-----Original Message-----
From: rpg400-l-bounces+gary.monnier=terex.com@xxxxxxxxxxxx
[mailto:rpg400-l-bounces+gary.monnier=terex.com@xxxxxxxxxxxx] On
Behalf Of Charles Wilt
Sent: Monday, August 01, 2011 11:19 AM
To: RPG programming on the IBM i / System i
Subject: Re: Reduce large amount of logicals in SUBFL pgm,take in
another direction

Gary,

You seem to be hung up on *MODULE...

I repeat, it doesn't matter where the statement is built. If you're
building a statement dynamically with concatenation of user supplied string.
The code is vulnerable. It doesn't have anything to do with *PGM, *MODULE,
*SRVPGM, authority or debug mode.

Charles

On Mon, Aug 1, 2011 at 1:54 PM, Monnier, Gary <Gary.Monnier@xxxxxxxxx>
wrote:
Charles,

With respect you seem to be hung up on my example being a *PGM. I
recommended *MODULE. If you feel someone can get to a *PGM build from
*MODULEs and can inject an SQL statement then again I assert security
settings to the program are set incorrectly. Either you allow *PUBLIC to
debug the program or you have had a security breach involving a profile with
enough authority to debug the program. If the executable *PGM allows
modules and or service programs to be changed then you also have a security
hole. In both cases it is not my example causing the breach and other much
larger security issues are in play.

Respectfully,

Gary Monnier


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Monday, August 01, 2011 6:06 AM
To: RPG programming on the IBM i / System i
Subject: Re: Reduce large amount of logicals in SUBFL pgm,take in
another direction

Gary,

If you think that your program doesn't open you up to SQL injection,
you are sadly mistaken...

The fact that the procedure is bound statically by reference or by copy
as opposed to a dynamic called *PGM has no bearing.

SQL injection attacks can occur anytime you dynamically build a
statement and concatenate user string input into the statement. It doesn't
matter where the statement is built.

Again, all that matters is that in some way shape or form, you are
building a statement like so:
wSqlStmt = 'SELECT * FROM MYTABLE WHERE MYFLD = ' +
userEnteredValue;

Theoretically, you could parse and sanitize the user input, making
sure it's safe before using it. However, unlike some languages RPG
doesn't have that functionality built in. Also, IMHO you're
dependent on the guy who wrote the sanitizer being smarter than the
hackers :)

The safe way to do dynamic statements is via parameter markers. You
build a statement like so:
wSqlStmt = 'SELECT * FROM MYTABLE WHERE MYFLD = ?';

then when you open/execute it, you pass in the variables to use at the
parameter markers.
open C1 using :userEnteredValue;

With respect to PCI requirements...
6.5 Develop applications based on secure coding guidelines and review
custom application code to identify coding vulnerabilities. Follow
up-to-date industry best practices to identify and manage vulnerabilities.

OWASP is one of the standards usually used for secure coding...their
top security risk for 2010...injection (SQL queries, LDAP queries, XPath
queries, OS commands, program arguments, etc. ).
https://www.owasp.org/index.php/Category:OWASP_Top_Ten_Project

Thus, dynamic SQL as used by your programs would fail an secure code
review and you'd likely fail a PCI audit.

HTH,
Charles






On Fri, Jul 29, 2011 at 2:26 PM, Monnier, Gary <Gary.Monnier@xxxxxxxxx>
wrote:
Your opinion Charles and what seems a very strong opinion. J



Yes, I've heard of SQL Injection attacks and no my suggestion does
not leave you open to this sort of attack. I've also heard of LDAP
injection attacks.



What I suggested does not impact PCI compliance or any other
security parameters. Nor does it impact FDA compliance. All the
MODULE does is build an SQL string. When bound with other modules
to make an executable object there are no compliance issues.



If you create ILE programs that allow updating modules or service
programs then you have a behavior that needs changing. My opinion
is, and it is only my opinion, you should NEVER create a program
with Allow update. You are just asking for trouble in the ILE world.



If you have ulcer causing issues with pgmToBuildSQL make it a copy
module rather than a bound module.



Regards,



Gary





-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Friday, July 29, 2011 10:35 AM
To: RPG programming on the IBM i / System i
Subject: Re: Reduce large amount of logicals in SUBFL pgm,take in
another direction



Very, very BAD IDEA!



Horrible in fact.



I hope you're not subject to PCI compliance rules, as the code you
posted pretty much guarantees an automatic failure.



Try googleing for "SQL injection"...



Charles



On Fri, Jul 29, 2011 at 1:16 PM, Monnier, Gary
<Gary.Monnier@xxxxxxxxx <mailto:Gary.Monnier@xxxxxxxxx> > wrote:

Sharon,



The process that builds your SQL statement can have parameters
passed

to it. One of these parameters can be a list of selections.

Something like this.



pgmToBuildSQL PR

nbrFieldsForWhereClause

arrayOfFieldsForWhereClause

arrayOfValuesForWhereClause





SQLStringBegin = 'Select * From yourfile ';



X = 1;

startPos = 1;



doW (X < = nbrFieldsForWhereClause);



whereValue = arrayOfFieldsForWhereClause(X) +

arrayOfValuesForWhereClause(X); //ValueFor can be = value, like

value, etc

valueLen = %len(%trimr(whereValue));

%subst(whereClause:startPos:valueLen) = whereValue;

startpos = startPos + valueLen + 1;

X = X + 1;



enddo;



Return;



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