AnyEvent-MP/MP/Transport.pm

=head1 NAME

AnyEvent::MP::Transport - actual transport protocol handler

=head1 SYNOPSIS

   use AnyEvent::MP::Transport;

=head1 DESCRIPTION

This implements the actual transport protocol for MP (it represents a
single link), most of which is considered an implementation detail.

See the "PROTOCOL" section below if you want to write another client for
this protocol.

=head1 FUNCTIONS/METHODS

=over 4

=cut

package AnyEvent::MP::Transport;

use common::sense;

use Scalar::Util;
use MIME::Base64 ();
use Storable ();
use JSON::XS ();

use AE ();
use AnyEvent::Socket ();
use AnyEvent::Handle ();

use base Exporter::;

our $VERSION = '0.0';
our $PROTOCOL_VERSION = 0;

=item $listener = mp_listener $host, $port, <constructor-args>, $cb->($transport)

Creates a listener on the given host/port using
C<AnyEvent::Socket::tcp_server>.

See C<new>, below, for constructor arguments.

Defaults for peerhost, peerport and fh are provided.

=cut

sub mp_server($$@) {
   my $cb = pop;
   my ($host, $port, @args) = @_;

   AnyEvent::Socket::tcp_server $host, $port, sub {
      my ($fh, $host, $port) = @_;

      $cb->(new AnyEvent::MP::Transport
         fh       => $fh,
         peerhost => $host,
         peerport => $port,
         @args,
      );
   }
}

=item $guard = mp_connect $host, $port, <constructor-args>, $cb->($transport)

=cut

sub mp_connect {
   my $cb = pop;
   my ($host, $port, @args) = @_;

   AnyEvent::Socket::tcp_connect $host, $port, sub {
      my ($fh, $nhost, $nport) = @_;

      return $cb->() unless $fh;

      $cb->(new AnyEvent::MP::Transport
         fh       => $fh,
         peername => $host,
         peerhost => $nhost,
         peerport => $nport,
         @args,
      );
   }
}

=item new AnyEvent::MP::Transport

   # immediately starts negotiation
   my $transport = new AnyEvent::MP::Transport
      # mandatory
      fh       => $filehandle,
      local_id => $identifier,
      on_recv  => sub { receive-callback },
      on_error => sub { error-callback },

      # optional
      secret   => "shared secret",
      on_eof   => sub { clean-close-callback },
      on_connect => sub { successful-connect-callback },
      greeting => { key => value },

      # tls support
      tls_ctx  => AnyEvent::TLS,
      peername => $peername, # for verification
   ;

=cut

our @FRAMINGS = qw(json storable); # the framing types we accept and send, in order of preference
our @AUTH_SND = qw(hmac_md6_64_256); # auth types we send
our @AUTH_RCV = (@AUTH_SND, qw(cleartext)); # auth types we accept

#AnyEvent::Handle::register_write_type mp_record => sub {
#};

sub new {
   my ($class, %arg) = @_;

   my $self = bless \%arg, $class;

   $self->{queue} = [];

   {
      Scalar::Util::weaken (my $self = $self);

      $arg{tls_ctx_disabled} ||= {
         sslv2  => 0,
         sslv3  => 0,
         tlsv1  => 1,
         verify => 1,
         cert_file => "secret.pem",
         ca_file   => "secret.pem",
         verify_require_client_cert => 1,
      };

      $arg{secret} = AnyEvent::MP::Base::default_secret ()
         unless exists $arg{secret};

      $self->{hdl} = new AnyEvent::Handle
         fh       => delete $arg{fh},
         autocork => 1,
         no_delay => 1,
         on_error => sub {
            $self->error ($_[2]);
         },
         peername => delete $arg{peername},
      ;

      my $secret = $arg{secret};
      my $greeting_kv = $self->{greeting} ||= {};
      $greeting_kv->{"tls"} = "1.0"
         if $arg{tls_ctx};
      $greeting_kv->{provider} = "AE-$VERSION";
      $greeting_kv->{peeraddr} = AnyEvent::Socket::format_hostport $self->{peerhost}, $self->{peerport};

      # send greeting
      my $lgreeting1 = "aemp;$PROTOCOL_VERSION"
                     . ";$AnyEvent::MP::Base::UNIQ"
                     . ";$AnyEvent::MP::Base::NODE"
                     . ";" . (join ",", @AUTH_RCV)
                     . ";" . (join ",", @FRAMINGS)
                     . (join "", map ";$_=$greeting_kv->{$_}", keys %$greeting_kv);

      my $lgreeting2 = MIME::Base64::encode_base64 AnyEvent::MP::Base::nonce (33), "";

      $self->{hdl}->push_write ("$lgreeting1\012$lgreeting2\012");

      # expect greeting
      $self->{hdl}->rbuf_max (4 * 1024);
      $self->{hdl}->push_read (line => sub {
         my $rgreeting1 = $_[1];

         my ($aemp, $version, $uniq, $rnode, $auths, $framings, @kv) = split /;/, $rgreeting1;

         if ($aemp ne "aemp") {
            return $self->error ("unparsable greeting");
         } elsif ($version != $PROTOCOL_VERSION) {
            return $self->error ("version mismatch (we: $PROTOCOL_VERSION, they: $version)");
         }

         my $s_auth;
         for my $auth_ (split /,/, $auths) {
            if (grep $auth_ eq $_, @AUTH_SND) {
               $s_auth = $auth_;
               last;
            }
         }

         defined $s_auth
            or return $self->error ("$auths: no common auth type supported");

         die unless $s_auth eq "hmac_md6_64_256"; # hardcoded atm.

         my $s_framing;
         for my $framing_ (split /,/, $framings) {
            if (grep $framing_ eq $_, @FRAMINGS) {
               $s_framing = $framing_;
               last;
            }
         }

         defined $s_framing
            or return $self->error ("$framings: no common framing method supported");

         $self->{remote_uniq} = $uniq;
         $self->{remote_node} = $rnode;

         $self->{remote_greeting} = {
            map /^([^=]+)(?:=(.*))?/ ? ($1 => $2) : (),
               @kv
         };

         # read nonce
         $self->{hdl}->push_read (line => sub {
            my $rgreeting2 = $_[1];

            if ($self->{tls_ctx} and 1 == int $self->{remote_greeting}{tls}) {
               $self->{tls} = $lgreeting2 lt $rgreeting2 ? "connect" : "accept";
               $self->{hdl}->starttls ($self->{tls}, $self->{tls_ctx});
            }
         
            # auth
            require Digest::MD6;
            require Digest::HMAC_MD6;

            my $key   = Digest::MD6::md6 ($secret);
            my $lauth = Digest::HMAC_MD6::hmac_md6_hex ($key, "$lgreeting1\012$lgreeting2\012$rgreeting1\012$rgreeting2\012", 64, 256);

            my $rauth =
               $s_auth eq "hmac_md6_64_256" ? Digest::HMAC_MD6::hmac_md6_hex ($key, "$rgreeting1\012$rgreeting2\012$lgreeting1\012$lgreeting2\012", 64, 256)
             : $s_auth eq "cleartext"       ? unpack "H*", $secret
             : die;

            $lauth ne $rauth # echo attack?
               or return $self->error ("authentication error");

            $self->{hdl}->push_write ("$s_auth;$lauth;$s_framing\012");

            # reasd the authentication response
            $self->{hdl}->push_read (line => sub {
               my ($hdl, $rline) = @_;

               my ($auth_method, $rauth2, $r_framing) = split /;/, $rline;

               if ($rauth2 ne $rauth) {
                  return $self->error ("authentication failure/shared secret mismatch");
               }

               $self->{s_framing} = $s_framing;

               $hdl->rbuf_max (undef);
               my $queue = delete $self->{queue}; # we are connected

               $self->connected;

               my $src_node = $self->{node};

               $hdl->push_write ($self->{s_framing} => $_)
                  for @$queue;

               my $rmsg; $rmsg = sub  {
                  $_[0]->push_read ($r_framing => $rmsg);

                  local $AnyEvent::MP::Base::SRCNODE = $src_node;
                  AnyEvent::MP::Base::_inject (@{ $_[1] });
               };
               $hdl->push_read ($r_framing => $rmsg);
            });
         });
      });
   }

   $self
}

sub error {
   my ($self, $msg) = @_;

   if ($self->{node} && $self->{node}{transport} == $self) {
      $self->{node}->clr_transport;
   }
   $AnyEvent::MP::Base::WARN->("$self->{peerhost}:$self->{peerport}: $msg");
   $self->destroy;
}

sub connected {
   my ($self) = @_;

   my $node = AnyEvent::MP::Base::add_node ($self->{remote_node});
   Scalar::Util::weaken ($self->{node} = $node);
   $node->set_transport ($self);
}

sub send {
   $_[0]{hdl}->push_write ($_[0]{s_framing} => $_[1]);
}

sub destroy {
   my ($self) = @_;

   $self->{hdl}->destroy
      if $self->{hdl};
}

sub DESTROY {
   my ($self) = @_;

   $self->destroy;
}

=back

=head1 PROTOCOL

The protocol is relatively simple, and consists of three phases which are
symmetrical for both sides: greeting (followed by optionally switching to
TLS mode), authentication and packet exchange.

the protocol is designed to allow both full-text and binary streams.

The greeting consists of two text lines that are ended by either an ASCII
CR LF pair, or a single ASCII LF (recommended).

=head2 GREETING

The first line contains strings separated (not ended) by C<;>
characters. The first even ixtrings are fixed by the protocol, the
remaining strings are C<KEY=VALUE> pairs. None of them may contain C<;>
characters themselves.

All the lines until after authentication must not exceed 4kb in length,
including delimiter. Afterwards there is no limit on the packet size that
can be received.

=head3 First Greeting Line

The fixed strings are:

=over 4

=item C<aemp>

The constant C<aemp> to identify the protocol.

=item protocol version

The protocol version supported by this end, currently C<0>. If the
versions don't match then no communication is possible. Minor extensions
are supposed to be handled by addign additional key-value pairs.

=item a token uniquely identifying the current node instance

This is a string that must change between restarts. It usually contains
things like the current time, the (OS) process id or similar values, but
no meaning of the contents are assumed.

=item the node endpoint descriptors

for public nodes, this is a comma-separated list of protocol endpoints,
i.e., the noderef. For slave nodes, this is a unique identifier.

=item the acceptable authentication methods

A comma-separated list of authentication methods supported by the
node. Note that AnyEvent::MP supports a C<hex_secret> authentication
method that accepts a cleartext password (hex-encoded), but will not use
this auth method itself.

The receiving side should choose the first auth method it supports.

=item the acceptable framing formats

A comma-separated list of packet encoding/framign formats understood. The
receiving side should choose the first framing format it supports for
sending packets (which might be different from the format it has to accept).

=back

The remaining arguments are C<KEY=VALUE> pairs. The following key-value
pairs are known at this time:

=over 4

=item provider=<module-version>

The software provider for this implementation. For AnyEvent::MP, this is
C<AE-0.0> or whatever version it currently is at.

=item peeraddr=<host>:<port>

The peer address (socket address of the other side) as seen locally, in the same format
as noderef endpoints.

=item tls=<major>.<minor>

Indicates that the other side supports TLS (version should be 1.0) and
wishes to do a TLS handshake.

=back

=head3 Second Greeting Line

After this greeting line there will be a second line containing a
cryptographic nonce, i.e. random data of high quality. To keep the
protocol text-only, these are usually 32 base64-encoded octets, but
it could be anything that doesn't contain any ASCII CR or ASCII LF
characters.

I<< The two nonces B<must> be different, and an aemp implementation
B<must> check and fail when they are identical >>.

Example of the two lines of greeting:

   aemp;0;fec.4a7720fc;127.0.0.1:1235,[::1]:1235;hmac_md6_64_256;json,storable;provider=AE-0.0
   p/I122ql7kJR8lumW3lXlXCeBnyDAvz8NQo3x5IFowE4

=head2 TLS handshake

I<< If, after the handshake, both sides indicate interest in TLS, then the
connection B<must> use TLS, or fail.>>

Both sides compare their nonces, and the side who sent the lower nonce
value ("string" comparison on the raw octet values) becomes the client,
and the one with the higher nonce the server.

=head2 AUTHENTICATION PHASE

After the greeting is received (and the optional TLS handshake),
the authentication phase begins, which consists of sending a single
C<;>-separated line with three fixed strings and any number of
C<KEY=VALUE> pairs.

The three fixed strings are:

=over 4

=item the authentication method chosen

This must be one of the methods offered by the other side in the greeting.

The currently supported authentication methods are:

=over 4

=item cleartext

This is simply the shared secret, lowercase-hex-encoded. This method is of
course very insecure, unless TLS is used, which is why this module will
accept, but not generate, cleartext auth replies.

=item hmac_md6_64_256

This method uses an MD6 HMAC with 64 bit blocksize and 256 bit hash. First, the shared secret
is hashed with MD6:

   key = MD6 (secret)

This secret is then used to generate the "local auth reply", by taking
the two local greeting lines and the two remote greeting lines (without
line endings), appending \012 to all of them, concatenating them and
calculating the MD6 HMAC with the key.

   lauth = HMAC_MD6 key, "lgreeting1\012lgreeting2\012rgreeting1\012rgreeting2\012"

This authentication token is then lowercase-hex-encoded and sent to the
other side.

Then the remote auth reply is generated using the same method, but local
and remote greeting lines swapped:

   rauth = HMAC_MD6 key, "rgreeting1\012rgreeting2\012lgreeting1\012lgreeting2\012"

This is the token that is expected from the other side.

=back

=item the authentication data

The authentication data itself, usually base64 or hex-encoded data, see
above.

=item the framing protocol chosen

This must be one of the framing protocols offered by the other side in the
greeting. Each side must accept the choice of the other side.

=back

Example:

   hmac_md6_64_256;363d5175df38bd9eaddd3f6ca18aa1c0c4aa22f0da245ac638d048398c26b8d3;json

=head2 DATA PHASE

After this, packets get exchanged using the chosen framing protocol. It is
quite possible that both sides use a different framing protocol.

=head1 SEE ALSO

L<AnyEvent>.

=head1 AUTHOR

 Marc Lehmann <schmorp@schmorp.de>
 http://home.schmorp.de/

=cut

1

Revision:	1.15
Committed:	Tue Aug 4 07:47:29 2009 UTC (14 years, 10 months ago) by root
Branch:	MAIN
Changes since 1.14:	+7 -1 lines
Log Message:	* empty log message *
#	User	Rev	Content
1	root	1.1	=head1 NAME
2
3	root	1.13	AnyEvent::MP::Transport - actual transport protocol handler
4	root	1.1
5			=head1 SYNOPSIS
6
7			use AnyEvent::MP::Transport;
8
9			=head1 DESCRIPTION
10
11	root	1.13	This implements the actual transport protocol for MP (it represents a
12			single link), most of which is considered an implementation detail.
13	root	1.1
14	root	1.7	See the "PROTOCOL" section below if you want to write another client for
15			this protocol.
16	root	1.1
17			=head1 FUNCTIONS/METHODS
18
19			=over 4
20
21			=cut
22
23			package AnyEvent::MP::Transport;
24
25			use common::sense;
26
27			use Scalar::Util;
28			use MIME::Base64 ();
29			use Storable ();
30	root	1.2	use JSON::XS ();
31	root	1.1
32			use AE ();
33			use AnyEvent::Socket ();
34			use AnyEvent::Handle ();
35	root	1.2
36	root	1.1	use base Exporter::;
37
38			our $VERSION = '0.0';
39	root	1.2	our $PROTOCOL_VERSION = 0;
40	root	1.1
41			=item $listener = mp_listener $host, $port, <constructor-args>, $cb->($transport)
42
43			Creates a listener on the given host/port using
44			C<AnyEvent::Socket::tcp_server>.
45
46			See C<new>, below, for constructor arguments.
47
48	root	1.10	Defaults for peerhost, peerport and fh are provided.
49	root	1.1
50			=cut
51
52			sub mp_server($$@) {
53			my $cb = pop;
54			my ($host, $port, @args) = @_;
55
56			AnyEvent::Socket::tcp_server $host, $port, sub {
57			my ($fh, $host, $port) = @_;
58
59			$cb->(new AnyEvent::MP::Transport
60			fh => $fh,
61			peerhost => $host,
62			peerport => $port,
63			@args,
64			);
65			}
66			}
67
68	root	1.2	=item $guard = mp_connect $host, $port, <constructor-args>, $cb->($transport)
69
70			=cut
71
72			sub mp_connect {
73			my $cb = pop;
74			my ($host, $port, @args) = @_;
75
76			AnyEvent::Socket::tcp_connect $host, $port, sub {
77			my ($fh, $nhost, $nport) = @_;
78
79			return $cb->() unless $fh;
80
81			$cb->(new AnyEvent::MP::Transport
82			fh => $fh,
83			peername => $host,
84			peerhost => $nhost,
85			peerport => $nport,
86			@args,
87			);
88			}
89			}
90
91	root	1.1	=item new AnyEvent::MP::Transport
92
93			# immediately starts negotiation
94			my $transport = new AnyEvent::MP::Transport
95	root	1.2	# mandatory
96	root	1.1	fh => $filehandle,
97	root	1.2	local_id => $identifier,
98	root	1.1	on_recv => sub { receive-callback },
99			on_error => sub { error-callback },
100
101			# optional
102			secret => "shared secret",
103			on_eof => sub { clean-close-callback },
104			on_connect => sub { successful-connect-callback },
105	root	1.2	greeting => { key => value },
106	root	1.1
107			# tls support
108			tls_ctx => AnyEvent::TLS,
109			peername => $peername, # for verification
110			;
111
112			=cut
113
114	root	1.7	our @FRAMINGS = qw(json storable); # the framing types we accept and send, in order of preference
115			our @AUTH_SND = qw(hmac_md6_64_256); # auth types we send
116	root	1.13	our @AUTH_RCV = (@AUTH_SND, qw(cleartext)); # auth types we accept
117	root	1.7
118			#AnyEvent::Handle::register_write_type mp_record => sub {
119			#};
120	root	1.4
121	root	1.1	sub new {
122			my ($class, %arg) = @_;
123
124			my $self = bless \%arg, $class;
125
126			$self->{queue} = [];
127
128			{
129			Scalar::Util::weaken (my $self = $self);
130
131	root	1.11	$arg{tls_ctx_disabled} \|\|= {
132			sslv2 => 0,
133			sslv3 => 0,
134			tlsv1 => 1,
135			verify => 1,
136			cert_file => "secret.pem",
137			ca_file => "secret.pem",
138			verify_require_client_cert => 1,
139			};
140	root	1.1
141	root	1.5	$arg{secret} = AnyEvent::MP::Base::default_secret ()
142	root	1.2	unless exists $arg{secret};
143
144	root	1.1	$self->{hdl} = new AnyEvent::Handle
145	root	1.2	fh => delete $arg{fh},
146	root	1.4	autocork => 1,
147			no_delay => 1,
148	root	1.1	on_error => sub {
149			$self->error ($_[2]);
150			},
151			peername => delete $arg{peername},
152			;
153
154	root	1.2	my $secret = $arg{secret};
155			my $greeting_kv = $self->{greeting} \|\|= {};
156	root	1.8	$greeting_kv->{"tls"} = "1.0"
157			if $arg{tls_ctx};
158	root	1.2	$greeting_kv->{provider} = "AE-$VERSION";
159	root	1.7	$greeting_kv->{peeraddr} = AnyEvent::Socket::format_hostport $self->{peerhost}, $self->{peerport};
160	root	1.1
161			# send greeting
162	root	1.12	my $lgreeting1 = "aemp;$PROTOCOL_VERSION"
163	root	1.7	. ";$AnyEvent::MP::Base::UNIQ"
164			. ";$AnyEvent::MP::Base::NODE"
165			. ";" . (join ",", @AUTH_RCV)
166			. ";" . (join ",", @FRAMINGS)
167			. (join "", map ";$_=$greeting_kv->{$_}", keys %$greeting_kv);
168	root	1.12
169	root	1.7	my $lgreeting2 = MIME::Base64::encode_base64 AnyEvent::MP::Base::nonce (33), "";
170	root	1.1
171	root	1.7	$self->{hdl}->push_write ("$lgreeting1\012$lgreeting2\012");
172	root	1.1
173			# expect greeting
174	root	1.12	$self->{hdl}->rbuf_max (4 * 1024);
175	root	1.1	$self->{hdl}->push_read (line => sub {
176	root	1.7	my $rgreeting1 = $_[1];
177	root	1.1
178	root	1.12	my ($aemp, $version, $uniq, $rnode, $auths, $framings, @kv) = split /;/, $rgreeting1;
179	root	1.1
180			if ($aemp ne "aemp") {
181			return $self->error ("unparsable greeting");
182	root	1.12	} elsif ($version != $PROTOCOL_VERSION) {
183			return $self->error ("version mismatch (we: $PROTOCOL_VERSION, they: $version)");
184	root	1.1	}
185
186	root	1.7	my $s_auth;
187			for my $auth_ (split /,/, $auths) {
188			if (grep $auth_ eq $_, @AUTH_SND) {
189			$s_auth = $auth_;
190			last;
191			}
192			}
193
194			defined $s_auth
195			or return $self->error ("$auths: no common auth type supported");
196
197			die unless $s_auth eq "hmac_md6_64_256"; # hardcoded atm.
198
199			my $s_framing;
200			for my $framing_ (split /,/, $framings) {
201			if (grep $framing_ eq $_, @FRAMINGS) {
202			$s_framing = $framing_;
203			last;
204			}
205			}
206
207			defined $s_framing
208			or return $self->error ("$framings: no common framing method supported");
209
210	root	1.2	$self->{remote_uniq} = $uniq;
211			$self->{remote_node} = $rnode;
212	root	1.1
213	root	1.2	$self->{remote_greeting} = {
214			map /^([^=]+)(?:=(.*))?/ ? ($1 => $2) : (),
215			@kv
216	root	1.1	};
217
218	root	1.7	# read nonce
219			$self->{hdl}->push_read (line => sub {
220			my $rgreeting2 = $_[1];
221
222	root	1.10	if ($self->{tls_ctx} and 1 == int $self->{remote_greeting}{tls}) {
223	root	1.8	$self->{tls} = $lgreeting2 lt $rgreeting2 ? "connect" : "accept";
224			$self->{hdl}->starttls ($self->{tls}, $self->{tls_ctx});
225			}
226
227	root	1.7	# auth
228			require Digest::MD6;
229			require Digest::HMAC_MD6;
230	root	1.1
231	root	1.11	my $key = Digest::MD6::md6 ($secret);
232	root	1.13	my $lauth = Digest::HMAC_MD6::hmac_md6_hex ($key, "$lgreeting1\012$lgreeting2\012$rgreeting1\012$rgreeting2\012", 64, 256);
233	root	1.1
234	root	1.7	my $rauth =
235	root	1.13	$s_auth eq "hmac_md6_64_256" ? Digest::HMAC_MD6::hmac_md6_hex ($key, "$rgreeting1\012$rgreeting2\012$lgreeting1\012$lgreeting2\012", 64, 256)
236			: $s_auth eq "cleartext" ? unpack "H*", $secret
237	root	1.7	: die;
238	root	1.1
239	root	1.7	$lauth ne $rauth # echo attack?
240			or return $self->error ("authentication error");
241	root	1.2
242	root	1.7	$self->{hdl}->push_write ("$s_auth;$lauth;$s_framing\012");
243	root	1.2
244	root	1.12	# reasd the authentication response
245	root	1.7	$self->{hdl}->push_read (line => sub {
246			my ($hdl, $rline) = @_;
247	root	1.2
248	root	1.7	my ($auth_method, $rauth2, $r_framing) = split /;/, $rline;
249	root	1.1
250	root	1.7	if ($rauth2 ne $rauth) {
251			return $self->error ("authentication failure/shared secret mismatch");
252			}
253	root	1.1
254	root	1.7	$self->{s_framing} = $s_framing;
255	root	1.2
256	root	1.7	$hdl->rbuf_max (undef);
257			my $queue = delete $self->{queue}; # we are connected
258	root	1.1
259	root	1.7	$self->connected;
260	root	1.1
261	root	1.12	my $src_node = $self->{node};
262
263	root	1.7	$hdl->push_write ($self->{s_framing} => $_)
264			for @$queue;
265	root	1.1
266	root	1.7	my $rmsg; $rmsg = sub {
267			$_[0]->push_read ($r_framing => $rmsg);
268	root	1.1
269	root	1.12	local $AnyEvent::MP::Base::SRCNODE = $src_node;
270			AnyEvent::MP::Base::_inject (@{ $_[1] });
271	root	1.7	};
272			$hdl->push_read ($r_framing => $rmsg);
273			});
274	root	1.1	});
275			});
276			}
277
278			$self
279			}
280
281			sub error {
282			my ($self, $msg) = @_;
283
284	root	1.4	if ($self->{node} && $self->{node}{transport} == $self) {
285			$self->{node}->clr_transport;
286			}
287	root	1.7	$AnyEvent::MP::Base::WARN->("$self->{peerhost}:$self->{peerport}: $msg");
288	root	1.4	$self->destroy;
289	root	1.1	}
290
291	root	1.2	sub connected {
292			my ($self) = @_;
293
294	root	1.5	my $node = AnyEvent::MP::Base::add_node ($self->{remote_node});
295	root	1.4	Scalar::Util::weaken ($self->{node} = $node);
296			$node->set_transport ($self);
297	root	1.2	}
298
299	root	1.1	sub send {
300	root	1.2	$_[0]{hdl}->push_write ($_[0]{s_framing} => $_[1]);
301	root	1.1	}
302
303			sub destroy {
304			my ($self) = @_;
305
306	root	1.2	$self->{hdl}->destroy
307			if $self->{hdl};
308	root	1.1	}
309
310			sub DESTROY {
311			my ($self) = @_;
312
313			$self->destroy;
314			}
315
316			=back
317
318	root	1.7	=head1 PROTOCOL
319
320			The protocol is relatively simple, and consists of three phases which are
321			symmetrical for both sides: greeting (followed by optionally switching to
322			TLS mode), authentication and packet exchange.
323
324			the protocol is designed to allow both full-text and binary streams.
325
326			The greeting consists of two text lines that are ended by either an ASCII
327			CR LF pair, or a single ASCII LF (recommended).
328
329			=head2 GREETING
330
331	root	1.8	The first line contains strings separated (not ended) by C<;>
332	root	1.12	characters. The first even ixtrings are fixed by the protocol, the
333	root	1.7	remaining strings are C<KEY=VALUE> pairs. None of them may contain C<;>
334			characters themselves.
335
336	root	1.15	All the lines until after authentication must not exceed 4kb in length,
337			including delimiter. Afterwards there is no limit on the packet size that
338			can be received.
339
340			=head3 First Greeting Line
341	root	1.12
342			The fixed strings are:
343	root	1.7
344			=over 4
345
346			=item C<aemp>
347
348			The constant C<aemp> to identify the protocol.
349
350			=item protocol version
351
352	root	1.12	The protocol version supported by this end, currently C<0>. If the
353			versions don't match then no communication is possible. Minor extensions
354			are supposed to be handled by addign additional key-value pairs.
355	root	1.7
356			=item a token uniquely identifying the current node instance
357
358			This is a string that must change between restarts. It usually contains
359			things like the current time, the (OS) process id or similar values, but
360			no meaning of the contents are assumed.
361
362			=item the node endpoint descriptors
363
364			for public nodes, this is a comma-separated list of protocol endpoints,
365			i.e., the noderef. For slave nodes, this is a unique identifier.
366
367			=item the acceptable authentication methods
368
369			A comma-separated list of authentication methods supported by the
370			node. Note that AnyEvent::MP supports a C<hex_secret> authentication
371			method that accepts a cleartext password (hex-encoded), but will not use
372			this auth method itself.
373
374			The receiving side should choose the first auth method it supports.
375
376			=item the acceptable framing formats
377
378			A comma-separated list of packet encoding/framign formats understood. The
379			receiving side should choose the first framing format it supports for
380			sending packets (which might be different from the format it has to accept).
381
382	root	1.10	=back
383	root	1.8
384			The remaining arguments are C<KEY=VALUE> pairs. The following key-value
385			pairs are known at this time:
386
387			=over 4
388
389			=item provider=<module-version>
390
391			The software provider for this implementation. For AnyEvent::MP, this is
392			C<AE-0.0> or whatever version it currently is at.
393
394			=item peeraddr=<host>:<port>
395
396			The peer address (socket address of the other side) as seen locally, in the same format
397			as noderef endpoints.
398
399			=item tls=<major>.<minor>
400
401			Indicates that the other side supports TLS (version should be 1.0) and
402			wishes to do a TLS handshake.
403
404			=back
405
406	root	1.15	=head3 Second Greeting Line
407
408	root	1.8	After this greeting line there will be a second line containing a
409			cryptographic nonce, i.e. random data of high quality. To keep the
410			protocol text-only, these are usually 32 base64-encoded octets, but
411			it could be anything that doesn't contain any ASCII CR or ASCII LF
412			characters.
413
414	root	1.14	I<< The two nonces B<must> be different, and an aemp implementation
415			B<must> check and fail when they are identical >>.
416
417	root	1.8	Example of the two lines of greeting:
418
419	root	1.12	aemp;0;fec.4a7720fc;127.0.0.1:1235,[::1]:1235;hmac_md6_64_256;json,storable;provider=AE-0.0
420			p/I122ql7kJR8lumW3lXlXCeBnyDAvz8NQo3x5IFowE4
421	root	1.8
422			=head2 TLS handshake
423
424	root	1.14	I<< If, after the handshake, both sides indicate interest in TLS, then the
425			connection B<must> use TLS, or fail.>>
426	root	1.8
427			Both sides compare their nonces, and the side who sent the lower nonce
428			value ("string" comparison on the raw octet values) becomes the client,
429			and the one with the higher nonce the server.
430
431			=head2 AUTHENTICATION PHASE
432
433			After the greeting is received (and the optional TLS handshake),
434			the authentication phase begins, which consists of sending a single
435			C<;>-separated line with three fixed strings and any number of
436			C<KEY=VALUE> pairs.
437
438			The three fixed strings are:
439
440			=over 4
441
442			=item the authentication method chosen
443
444			This must be one of the methods offered by the other side in the greeting.
445
446	root	1.13	The currently supported authentication methods are:
447
448			=over 4
449
450			=item cleartext
451
452			This is simply the shared secret, lowercase-hex-encoded. This method is of
453			course very insecure, unless TLS is used, which is why this module will
454			accept, but not generate, cleartext auth replies.
455
456			=item hmac_md6_64_256
457
458			This method uses an MD6 HMAC with 64 bit blocksize and 256 bit hash. First, the shared secret
459			is hashed with MD6:
460
461			key = MD6 (secret)
462
463			This secret is then used to generate the "local auth reply", by taking
464			the two local greeting lines and the two remote greeting lines (without
465			line endings), appending \012 to all of them, concatenating them and
466			calculating the MD6 HMAC with the key.
467
468			lauth = HMAC_MD6 key, "lgreeting1\012lgreeting2\012rgreeting1\012rgreeting2\012"
469
470			This authentication token is then lowercase-hex-encoded and sent to the
471			other side.
472
473			Then the remote auth reply is generated using the same method, but local
474			and remote greeting lines swapped:
475
476			rauth = HMAC_MD6 key, "rgreeting1\012rgreeting2\012lgreeting1\012lgreeting2\012"
477
478			This is the token that is expected from the other side.
479
480			=back
481
482	root	1.8	=item the authentication data
483
484	root	1.13	The authentication data itself, usually base64 or hex-encoded data, see
485			above.
486	root	1.8
487			=item the framing protocol chosen
488
489			This must be one of the framing protocols offered by the other side in the
490			greeting. Each side must accept the choice of the other side.
491
492			=back
493
494	root	1.12	Example:
495	root	1.9
496	root	1.13	hmac_md6_64_256;363d5175df38bd9eaddd3f6ca18aa1c0c4aa22f0da245ac638d048398c26b8d3;json
497	root	1.9
498	root	1.8	=head2 DATA PHASE
499
500			After this, packets get exchanged using the chosen framing protocol. It is
501			quite possible that both sides use a different framing protocol.
502
503	root	1.1	=head1 SEE ALSO
504
505			L<AnyEvent>.
506
507			=head1 AUTHOR
508
509			Marc Lehmann <schmorp@schmorp.de>
510			http://home.schmorp.de/
511
512			=cut
513
514			1
515