Question on EVP_DecryptFinal_ex

[David Li]

Hi,

I am using openssl 1.0.1h and AES128 CBC mode to encrypt some arbitrary
long ASCII string.
I encountered an issue at decryption. If I use EVP_DecryptFinal_ex then the
output is unrecognizable. If I remove the following then the output is OK.

if ((rc = EVP_DecryptFinal_ex(&ctx, debuf, &tmplen)) == 0) {
    printf (" Finalization error: %d\n", rc);
    return -1;
  }

Can anyone explain why?

David