Net::SSH::Perl::Mac(3pm) - phpMan

Net::SSH::Perl::Mac(3pm)       User Contributed Perl Documentation       Net::SSH::Perl::Mac(3pm)



NAME
       Net::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");

DESCRIPTION
       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.

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 v5.10.0                                2001-04-20                   Net::SSH::Perl::Mac(3pm)

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