Decrypt command returns incorrect value

Assigning a string, with a length greater than 114 characters to an unused variable, above code calling the decrypt function, can cause the decrypt function to return an invalid value.

Nov 21, 2017
Knowledge

Title

URL Name

decrypt-command-returns-incorrect-value

Article Number

000131322

Environment

Product: OpenEdge Version: 11.4, 11.5, 11.6, 11.7 OS: All supported platforms

Question/Problem Description

When using the decrypt command with the key, iv and algorithm parameters, the results are incorrect if a prior line of code assigns a string of over 114 characters in length to any variable.

The following code sample demonstrates the issue:

def var rText as raw no-undo.
def var rKey as raw no-undo.
def var rIV as raw no-undo.
def var sPass as char no-undo.
def var tPass as char no-undo.
def var tKey as char no-undo.
def var myTemp as char no-undo.

myTemp = "12345678901234567890123456789012345678901234567890123456789012345678901234567890123456789012345678901234!".

tPass = "vlogw9E=".
tKey = "c24Au8Zk9V3zykqg3Onmvw==".
rText = base64-decode( tPass ).
rKey = base64-decode( tKey ).
rIV = base64-decode("11111111").

sPass = get-string( decrypt(rText, rKey, rIV, "AES_OFB_128") , 1 ).
message tPass skip tKey skip sPass view-as alert-box.

Steps to Reproduce

Run the code shown above.

Clarifying Information

Separating the call to decrypt from the call to get-string (performing above in two steps) did not correct the problem.
If the string variable contains more than 114 characters the encrypted string is not decrypted correctly.
In the code above, removing the exclamation mark (!), thus reducing the string length by one character, mitigates the problem.

Error Message

Defect Number

PSC00359637

Enhancement Number

Cause

The IV parameter of the decrypt was shorter than what was expected internally. This caused data to be written beyond the length of the field.

Resolution

The fix for this issue is expected to be in the upcoming OpenEdge release 12.0. As of 11/21/2017, release 12.0 is scheduled to be released in the second half of 2018, although dates and content of the release are subject to change.

Workaround

Using the SECURITY-POLICY handle assignments instead of the parameters, seems to work around the problem:

From the code above, change this:

sPass = get-string( decrypt(rText, rKey, rIV, "AES_OFB_128") , 1 ).
message tPass skip tKey skip sPass view-as alert-box.

To this:

SECURITY-POLICY:SYMMETRIC-ENCRYPTION-ALGORITHM = "AES_OFB_128". SECURITY-POLICY:SYMMETRIC-ENCRYPTION-KEY = rKey.
SECURITY-POLICY:SYMMETRIC-ENCRYPTION-IV = rIV.
sPass = get-string( decrypt(rText) , 1 ).
message tPass skip tKey skip sPass view-as alert-box.

Notes

References to other Documentation:

https://documentation.progress.com/output/ua/OpenEdge_latest/index.html#page/dvref%2Fsecurity-policy-system-handle.html

https://documentation.progress.com/output/ua/OpenEdge_latest/index.html#page/dvpin%2Fimplementing-symmetric-cryptography-in-abl.html%23

Progress article(s):
How to use the ENCRYPT and DECRYPT functions

Keyword Phrase

Last Modified Date

11/20/2020 7:12 AM

Decrypt command returns incorrect value

Files(0)

Was this article helpful?

Was this article helpful?

Decrypt command returns incorrect value

Information

Related Articles