Re: Cipher MI instruction (MD5 function)

Hello Yivi,

- Try resetting HashWorkArea before each subsequent call.

Best regards,
Carsten Flensburg


----- Original Message ----- 
From: "Yivi" <nardus@xxxxxxxxx>
To: "RPG programming on the AS400 / iSeries" <rpg400-l@xxxxxxxxxxxx>
Sent: Friday, December 23, 2005 9:13 AM
Subject: Cipher MI instruction (MD5 function)


Hi there,

I am trying to to use the MD5 function to store/check passwords, but things
aren't working as expected. Or, to put it better, they work as expected but
only once.

The second time the cipher function is invoked in the same program
execution, it will generate a MCH5601 exception, and be done with it. First
time works perfectly, but the second will always fail.

I declare the procedures I am using:

Dcvthc PR EXTPROC('cvthc')
D 1
D 1
D 10i 0 VALUE

DCipher PR EXTPROC('_CIPHER')
D * VALUE
D * VALUE
D * VALUE
I declare the control ds and work variables (as seen in
http://archive.midrange.com/midrange-l/200006/msg01334.html)

DControls     DS
D Function      5i  0 inz(5)
D HashAlg       1     inz(x'00')
D Sequence      1     inz(x'00')
D DataLngth     10i 0
D Unused        8     inz(*LOVAL)
D HashCtxPtr    *     inz(%addr(HashWorkArea))
DHashWorkArea S 96    inz(*LOVAL)
DDestinoHex   S 16
DDestinoChr   S 32
DDestinoPtr   S *     inz(%addr(DestinoHex))
DFuentePtr    S *     inz(%addr(Fuente))
DFuente       S 8
I check against user provided password (CONTRA) against the one stored (
USER.CONTRA, already stored in DB)

dow CONTRA <> USER.CONTRA;
  exFmt AskForPass;
  fuente    = CONTRA;
  DataLngth = %len(%trimr(fuente));
  Cipher(%addr(DestinoPtr) : %addr(Controls) : %addr(FuentePtr));
  CVTHC(DestinoChr : DestinoHex :%size(DestinoChr));
endDo;

If the user puts his/her password correctly in the first attempt, things go
on and everything is nice. Otherwise, he gets another chance, and then the
program will fail (right or wrong password, it doesn't matter) giving error
message MCH5601, reason code X'0000'.