Manual Reference Pages - NET::SSH::PERL::MAC (3)
Net::SSH::Perl::Mac - MAC support for SSH2
my $mac = Net::SSH::Perl::Mac->new(hmac-sha1, $key);
Net::SSH::Perl::Mac (and its subclasses) provides MAC support
for the SSH2 implementation in Net::SSH::Perl. In the SSH2
protocol, each packet sent between client and server (after the
key exchange and algorithm negotiation phase) contains a MAC
to protect its integrity. The sending party computes the MAC over
the length, padding, and (encrypted) payload fields of the packet,
then appends the MAC; and the receiving party recomputes the MAC
against the data that it receives.
The MAC is computed using part of the key that is negotiated
during the key exchange phase. During negotiation, packets do
not contain MAC; after the SSH_MSG_NEWKEYS message is sent,
each side turns on its respective encryption, MAC, and compression
code, for each packet that is sent after that point.
Net::SSH::Perl supports two MAC algorithms: hmac-sha1 and
hmac-md5. These algorithms are implemented, respectively,
by Digest::HMAC_SHA1 and Digest::HMAC_MD5.
Each MAC object supports the following methods:
CW$mac = Net::SSH::Perl::Mac->new( CW$name )
Constructs a new MAC object and returns that object.
CW$mac->init( CW$key )
Initializes $mac and sets its key to $key (or rather,
to a substring of key, key_len bytes long). As this implies,
the key_len method should be called before init to set
the intended length of the key.
CW$mac->hmac( CW$data )
Computes the MAC over $data, using the key set in the
initialization phase, and returns the MAC.
Returns the length of the MAC (eg. 20 for HMAC_SHA1).
CW$mac->key_len( CW$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
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.
Enables the MAC object. This is used by Net::SSH::Perl::Kex
to turn on the MAC after key negotiation.
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 v5.20.3 ||NET::SSH::PERL::MAC (3) ||2015-09-12 |
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