Message.pm

# Written by Matt Caswell for the OpenSSL project.
# ====================================================================
# Copyright (c) 1998-2015 The OpenSSL Project.  All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in
#    the documentation and/or other materials provided with the
#    distribution.
#
# 3. All advertising materials mentioning features or use of this
#    software must display the following acknowledgment:
#    "This product includes software developed by the OpenSSL Project
#    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
#
# 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
#    endorse or promote products derived from this software without
#    prior written permission. For written permission, please contact
#    openssl-core@openssl.org.
#
# 5. Products derived from this software may not be called "OpenSSL"
#    nor may "OpenSSL" appear in their names without prior written
#    permission of the OpenSSL Project.
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# 6. Redistributions of any form whatsoever must retain the following
#    acknowledgment:
#    "This product includes software developed by the OpenSSL Project
#    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
#
# THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
# EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
# PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
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# STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
# OF THE POSSIBILITY OF SUCH DAMAGE.
# ====================================================================
#
# This product includes cryptographic software written by Eric Young
# (eay@cryptsoft.com).  This product includes software written by Tim
# Hudson (tjh@cryptsoft.com).

use strict;

package TLSProxy::Message;

use constant TLS_MESSAGE_HEADER_LENGTH => 4;

#Message types
use constant {
    MT_HELLO_REQUEST => 0,
    MT_CLIENT_HELLO => 1,
    MT_SERVER_HELLO => 2,
    MT_NEW_SESSION_TICKET => 4,
    MT_CERTIFICATE => 11,
    MT_SERVER_KEY_EXCHANGE => 12,
    MT_CERTIFICATE_REQUEST => 13,
    MT_SERVER_HELLO_DONE => 14,
    MT_CERTIFICATE_VERIFY => 15,
    MT_CLIENT_KEY_EXCHANGE => 16,
    MT_FINISHED => 20,
    MT_CERTIFICATE_STATUS => 22,
    MT_NEXT_PROTO => 67
};
my %message_type = (
    MT_HELLO_REQUEST, "HelloRequest",
    MT_CLIENT_HELLO, "ClientHello",
    MT_SERVER_HELLO, "ServerHello",
    MT_NEW_SESSION_TICKET, "NewSessionTicket",
    MT_CERTIFICATE, "Certificate",
    MT_SERVER_KEY_EXCHANGE, "ServerKeyExchange",
    MT_CERTIFICATE_REQUEST, "CertificateRequest",
    MT_SERVER_HELLO_DONE, "ServerHelloDone",
    MT_CERTIFICATE_VERIFY, "CertificateVerify",
    MT_CLIENT_KEY_EXCHANGE, "ClientKeyExchange",
    MT_FINISHED, "Finished",
    MT_CERTIFICATE_STATUS, "CertificateStatus",
    MT_NEXT_PROTO, "NextProto"
);

my $payload = "";
my $messlen = -1;
my $mt;
my $startoffset = -1;
my $server = 0;
my $success = 0;
my $end = 0;
my @message_rec_list = ();
my @message_frag_lens = ();

sub clear
{
    $payload = "";
    $messlen = -1;
    $startoffset = -1;
    $server = 0;
    $success = 0;
    $end = 0;
    @message_rec_list = ();
    @message_frag_lens = ();
}

#Class method to extract messages from a record
sub get_messages
{
    my $class = shift;
    my $serverin = shift;
    my $record = shift;
    my @messages = ();
    my $message;

    if ($serverin != $server && length($payload) != 0) {
        die "Changed peer, but we still have fragment data\n";
    }
    $server = $serverin;

    if ($record->content_type == TLSProxy::Record::RT_CCS) {
        if ($payload ne "") {
            #We can't handle this yet
            die "CCS received before message data complete\n";
        }
        if ($server) {
            TLSProxy::Record->server_ccs_seen(1);
        } else {
            TLSProxy::Record->client_ccs_seen(1);
        }
    } elsif ($record->content_type == TLSProxy::Record::RT_HANDSHAKE) {
        if ($record->len == 0 || $record->len_real == 0) {
            print "  Message truncated\n";
        } else {
            my $recoffset = 0;

            if (length $payload > 0) {
                #We are continuing processing a message started in a previous
                #record. Add this record to the list associated with this
                #message
                push @message_rec_list, $record;

                if ($messlen <= length($payload)) {
                    #Shouldn't happen
                    die "Internal error: invalid messlen: ".$messlen
                        ." payload length:".length($payload)."\n";
                }
                if (length($payload) + $record->decrypt_len >= $messlen) {
                    #We can complete the message with this record
                    $recoffset = $messlen - length($payload);
                    $payload .= substr($record->decrypt_data, 0, $recoffset);
                    push @message_frag_lens, $recoffset;
                    $message = create_message($server, $mt, $payload,
                                              $startoffset);
                    push @messages, $message;

                    #Check if we have finished the handshake
                    if ($mt == MT_FINISHED && $server) {
                        $success = 1;
                        $end = 1;
                    }
                    $payload = "";
                } else {
                    #This is just part of the total message
                    $payload .= $record->decrypt_data;
                    $recoffset = $record->decrypt_len;
                    push @message_frag_lens, $record->decrypt_len;
                }
                print "  Partial message data read: ".$recoffset." bytes\n";
            }

            while ($record->decrypt_len > $recoffset) {
                #We are at the start of a new message
                if ($record->decrypt_len - $recoffset < 4) {
                    #Whilst technically probably valid we can't cope with this
                    die "End of record in the middle of a message header\n";
                }
                @message_rec_list = ($record);
                my $lenhi;
                my $lenlo;
                ($mt, $lenhi, $lenlo) = unpack('CnC',
                                               substr($record->decrypt_data,
                                                      $recoffset));
                $messlen = ($lenhi << 8) | $lenlo;
                print "  Message type: $message_type{$mt}\n";
                print "  Message Length: $messlen\n";
                $startoffset = $recoffset;
                $recoffset += 4;
                $payload = "";
                
                if ($recoffset < $record->decrypt_len) {
                    #Some payload data is present in this record
                    if ($record->decrypt_len - $recoffset >= $messlen) {
                        #We can complete the message with this record
                        $payload .= substr($record->decrypt_data, $recoffset,
                                           $messlen);
                        $recoffset += $messlen;
                        push @message_frag_lens, $messlen;
                        $message = create_message($server, $mt, $payload,
                                                  $startoffset);
                        push @messages, $message;

                        #Check if we have finished the handshake
                        if ($mt == MT_FINISHED && $server) {
                            $success = 1;
                            $end = 1;
                        }
                        $payload = "";
                    } else {
                        #This is just part of the total message
                        $payload .= substr($record->decrypt_data, $recoffset,
                                           $record->decrypt_len - $recoffset);
                        $recoffset = $record->decrypt_len;
                        push @message_frag_lens, $recoffset;
                    }
                }
            }
        }
    } elsif ($record->content_type == TLSProxy::Record::RT_APPLICATION_DATA) {
        print "  [ENCRYPTED APPLICATION DATA]\n";
        print "  [".$record->decrypt_data."]\n";
    } elsif ($record->content_type == TLSProxy::Record::RT_ALERT) {
        #For now assume all alerts are fatal
        $end = 1;
    }

    return @messages;
}

#Function to work out which sub-class we need to create and then
#construct it
sub create_message
{
    my ($server, $mt, $data, $startoffset) = @_;
    my $message;

    #We only support ClientHello in this version...needs to be extended for
    #others
    if ($mt == MT_CLIENT_HELLO) {
        $message = TLSProxy::ClientHello->new(
            $server,
            $data,
            [@message_rec_list],
            $startoffset,
            [@message_frag_lens]
        );
        $message->parse();
    } else {
        #Unknown message type
        $message = TLSProxy::Message->new(
            $server,
            $mt,
            $data,
            [@message_rec_list],
            $startoffset,
            [@message_frag_lens]
        );
    }

    return $message;
}

sub end
{
    my $class = shift;
    return $end;
}
sub success
{
    my $class = shift;
    return $success;
}

sub new
{
    my $class = shift;
    my ($server,
        $mt,
        $data,
        $records,
        $startoffset,
        $message_frag_lens) = @_;
    
    my $self = {
        server => $server,
        data => $data,
        records => $records,
        mt => $mt,
        startoffset => $startoffset,
        message_frag_lens => $message_frag_lens
    };

    return bless $self, $class;
}

#Update all the underlying records with the modified data from this message
#Note: Does not currently support re-encrypting
sub repack
{
    my $self = shift;
    my $msgdata;

    my $numrecs = $#{$self->records};

    $self->set_message_contents();

    my $lenhi;
    my $lenlo;

    $lenlo = length($self->data) & 0xff;
    $lenhi = length($self->data) >> 8;
    my $msgdata = pack('CnC', $self->mt, $lenhi, $lenlo).$self->data;


    if ($numrecs == 0) {
        #The message is fully contained within one record
        my ($rec) = @{$self->records};
        my $recdata = $rec->decrypt_data;

        if (length($msgdata) != ${$self->message_frag_lens}[0]
                                + TLS_MESSAGE_HEADER_LENGTH) {
            #Message length has changed! Better adjust the record length
            my $diff = length($msgdata) - ${$self->message_frag_lens}[0]
                                        - TLS_MESSAGE_HEADER_LENGTH;
            $rec->len($rec->len + $diff);
        }

        $rec->data(substr($recdata, 0, $self->startoffset)
                   .($msgdata)
                   .substr($recdata, ${$self->message_frag_lens}[0]
                                     + TLS_MESSAGE_HEADER_LENGTH));

        #Update the fragment len in case we changed it above
        ${$self->message_frag_lens}[0] = length($msgdata)
                                         - TLS_MESSAGE_HEADER_LENGTH;
        return;
    }

    #Note we don't currently support changing a fragmented message length
    my $recctr = 0;
    my $datadone = 0;
    foreach my $rec (@{$self->records}) {
        my $recdata = $rec->decrypt_data;
        if ($recctr == 0) {
            #This is the first record
            my $remainlen = length($recdata) - $self->startoffset;
            $rec->data(substr($recdata, 0, $self->startoffset)
                       .substr(($msgdata), 0, $remainlen));
            $datadone += $remainlen;
        } elsif ($recctr + 1 == $numrecs) {
            #This is the last record
            $rec->data(substr($msgdata, $datadone));
        } else {
            #This is a middle record
            $rec->data(substr($msgdata, $datadone, length($rec->data)));
            $datadone += length($rec->data);
        }
        $recctr++;
    }
}

#To be overridden by sub-classes
sub set_message_contents
{
}

#Read only accessors
sub server
{
    my $self = shift;
    return $self->{server};
}

#Read/write accessors
sub mt
{
    my $self = shift;
    if (@_) {
      $self->{mt} = shift;
    }
    return $self->{mt};
}
sub data
{
    my $self = shift;
    if (@_) {
      $self->{data} = shift;
    }
    return $self->{data};
}
sub records
{
    my $self = shift;
    if (@_) {
      $self->{records} = shift;
    }
    return $self->{records};
}
sub startoffset
{
    my $self = shift;
    if (@_) {
      $self->{startoffset} = shift;
    }
    return $self->{startoffset};
}
sub message_frag_lens
{
    my $self = shift;
    if (@_) {
      $self->{message_frag_lens} = shift;
    }
    return $self->{message_frag_lens};
}

1;