Net::SSH::Perl::Mac(3)User Contributed Perl DocumentatioNet::SSH::Perl::Mac(3)NAMENet::SSH::Perl::Mac - MAC support for SSH2
SYNOPSIS
use Net::SSH::Perl::Mac;
my $mac = Net::SSH::Perl::Mac->new('hmac-sha1', $key);
$mac->hmac("foo bar");
DESCRIPTIONNet::SSH::Perl::Mac (and its subclasses) provides MAC support for the
SSH2 implementation in Net::SSH::Perl. In the SSH2 protocol, each
packet sent between client and server (after the key exchange and
algorithm negotiation phase) contains a MAC to protect its integrity.
The sending party computes the MAC over the length, padding, and
(encrypted) payload fields of the packet, then appends the MAC; and the
receiving party recomputes the MAC against the data that it receives.
The MAC is computed using part of the key that is negotiated during the
key exchange phase. During negotiation, packets do not contain MAC;
after the SSH_MSG_NEWKEYS message is sent, each side turns on its
respective encryption, MAC, and compression code, for each packet that
is sent after that point.
Net::SSH::Perl supports two MAC algorithms: hmac-sha1 and hmac-md5.
These algorithms are implemented, respectively, by Digest::HMAC_SHA1
and Digest::HMAC_MD5.
USAGE
Each MAC object supports the following methods:
$mac = Net::SSH::Perl::Mac->new( $name )
Constructs a new MAC object and returns that object.
$mac->init( $key )
Initializes $mac and sets its key to $key (or rather, to a substring of
key, key_len bytes long). As this implies, the key_len method should be
called before init to set the intended length of the key.
$mac->hmac( $data )
Computes the MAC over $data, using the key set in the initialization
phase, and returns the MAC.
$mac->len
Returns the length of the MAC (eg. 20 for HMAC_SHA1).
$mac->key_len( $len )
Given $len sets the key length of $mac to $len. This should be called
before the init method, because init uses this value to take a
substring of the provided key value.
Most of the time this should just be set to the MAC length (the len
method); certain SSH implementations have a bug, however, wherein they
always use only the first 16 bytes of the provided key.
$mac->enable
Enables the MAC object. This is used by Net::SSH::Perl::Kex to "turn
on" the MAC after key negotiation.
$mac->enabled
Tests the enabled flag (set with the enable method). This is used by
Net::SSH::Perl::Packet to determine whether or not to compute a MAC on
an outgoing packet.
AUTHOR & COPYRIGHTS
Please see the Net::SSH::Perl manpage for author, copyright, and
license information.
perl v5.14.1 2001-04-20 Net::SSH::Perl::Mac(3)
