| Subject: | possible bug with padding |
| Date: | Sat, 22 Nov 2008 15:53:18 -0800 |
| To: | bug-Crypt-CBC [...] rt.cpan.org |
| From: | Scott Best <sbest [...] echogent.com> |
Heya. Am trying to decrypt an AES-128-CBC message received
from another platform which uses no padding. The script I'm using is
attached below. Problem is: I cannot seem to turn off padding, even
with the "rijndael_compat" option. The input is 16B, the key is 16B, the
IV is 16B, but the result is 32B. Script output is:
IV used: 00000000000000000000000000000000
Padding used: CODE(0x81d912c)
Encrypted hex is:
0a234d17985d5bc8818ff6965d894072a389b2719ddc045eaf808b571e3072a7
Expected: 0a234D17985D5BC8818FF6965D894072
Thanks in advance for any help!
-Scott
Show quoted text
----------start------------------
#!/usr/bin/perl
use Crypt::CBC;
use MIME::Base64;
use bytes;
### set key in hex; pack a 32-character hex string into 16B
#
#my $hexkey = "7a697070657236373839616263646566";
my $hexkey = "E5E6E7E9EA292A2B2D256789012345E5";
my $key = pack 'H*',$hexkey;
print "Key size is: ", bytes::length($key), " bytes\n";
### set IV to all-zeroes; pack a 32-character hex string into 16B
#
my $hexiv = "00000000000000000000000000000000";
my $iv = pack 'H*',$hexiv;
print "IV size is: ", bytes::length($iv), " bytes\n";
### Plaintext is 16-characters of ASCII, 16-bytes
#
my $plaintext = "Hello world!!!!!";
print "Plaintext size is: ", bytes::length($plaintext), " bytes\n\n";
### Options are critical: literal key, keysize, specify IV
#
my $cipher = Crypt::CBC->new( -key => $key,
-header => 'none',
-literal_key => 'true',
-iv => $iv,
-cipher => 'Rijndael',
-keysize => '16',
-blocksize => '16'
-padding => 'rijndael_compat' );
### Perform encryption here
#
my $ciphertext = $cipher->encrypt($plaintext);
### Printout IV and padding, just to be sure...
#
my $usediv = $cipher->get_initialization_vector();
my $divhex = unpack 'H*',$usediv;
print "IV used: ", $divhex, "\n";
print "Padding used: ", $cipher->padding(), "\n\n";
### Printout 16B result, converted into 32 Hex digits
#
my $cipherhex = unpack 'H*',$ciphertext;
print "Encrypted hex is: ", $cipherhex, "\n";
print "Expected: 0a234D17985D5BC8818FF6965D894072","\n";
### Encode binary result using base64:
#
my $b64_enc = encode_base64($ciphertext);
print "B64 encoded hex is: ", $b64_enc, "\n" ;
### Finally, decode base64 string, then decrypt it:
#
my $b64_dec = decode_base64($b64_enc);
my $decrypted = $cipher->decrypt($b64_dec);
print "Decrypted result is: ", $decrypted, "\n";
----------end-------------------------------------