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WMBus: error correction for AES descryption (no padding if data length is multiple of block size)

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git-svn-id: https://svn.fhem.de/fhem/trunk@17777 2b470e98-0d58-463d-a4d8-8e2adae1ed80
This commit is contained in:
kaihs 2018-11-18 15:44:03 +00:00
parent 50a399e682
commit 1312835102
1 changed files with 9 additions and 1 deletions
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10
fhem/FHEM/WMBus.pm
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@ -1443,13 +1443,20 @@ sub decodePayload($$) {
sub decrypt($) { sub decrypt($) {
my $self = shift; my $self = shift;
my $encrypted = shift; my $encrypted = shift;
my $padding = 2;
# see 4.2.5.3, page 26 # see 4.2.5.3, page 26
my $initVector = substr($self->{msg},2,8); my $initVector = substr($self->{msg},2,8);
for (1..8) { for (1..8) {
$initVector .= pack('C',$self->{access_no}); $initVector .= pack('C',$self->{access_no});
} }
my $cipher = Crypt::Mode::CBC->new('AES', 2); if (length($encrypted)%16 == 0) {
# no padding if data length is multiple of blocksize
$padding = 0;
} else {
$padding = 2;
}
my $cipher = Crypt::Mode::CBC->new('AES', $padding);
return $cipher->decrypt($encrypted, $self->{aeskey}, $initVector); return $cipher->decrypt($encrypted, $self->{aeskey}, $initVector);
} }
@ -1817,6 +1824,7 @@ sub decodeApplicationLayer($) {
if ($self->{aeskey}) { if ($self->{aeskey}) {
if ($hasCBC) { if ($hasCBC) {
#printf("encrypted payload %s\n", unpack("H*", substr($applicationlayer,$offset)));
$payload = $self->decrypt(substr($applicationlayer,$offset)); $payload = $self->decrypt(substr($applicationlayer,$offset));
#printf("decrypted payload %s\n", unpack("H*", $payload)); #printf("decrypted payload %s\n", unpack("H*", $payload));
if (unpack('n', $payload) == 0x2f2f) { if (unpack('n', $payload) == 0x2f2f) {