$A->kexRequest();
$A->send('Hello there!');
$B->send('Hi!');
print "\nSetting up MITM:\n\n";
$state = 0;
$stolenP = null;
$evilShared = null;
$A = new ConversationEntity('A', $dh);
$B = new ConversationEntity('B', $dh);
$A->onSend = function ($data) use($B, &$state, &$stolenP, &$evilShared, $dh) {
if ($state === 0) {
print "M: Manipulating kex req\n";
$obj = json_decode($data);
$obj->A = $obj->p;
$stolenP = gmp_init($obj->p, 16);
$evilShared = gmp_strval($dh->generateShared($stolenP, $stolenP), 16);
$state = 1;
$B->receive(json_encode($obj));
} else {
$key = sha1($evilShared, true);
$iv = substr($data, 0, 16);
$message = decryptAES128CBC(substr($data, 16), $key, $iv);
print "M: sniffed: {$message}\n";
}
};
$B->onSend = function ($data) use($A, &$state, &$stolenP, &$evilShared) {
if ($state === 1) {
print "M: Manipulating kex resp\n";
$obj = json_decode($data);
$obj->B = gmp_strval($stolenP, 16);
$state = 2;
}
function generateShared($private, $public)
{
return gmp_powm($public, $private, $this->p);
}
function p()
{
return gmp_strval($this->p, 16);
}
function g($val = null)
{
if (is_string($val)) {
$this->g = gmp_init($val, 16);
}
return gmp_strval($this->g, 16);
}
}
// don't output if we're included into another script.
if (!debug_backtrace()) {
$dh = new DH();
$a = $dh->generatePrivate();
$b = $dh->generatePrivate();
$A = $dh->generatePublic($a);
$B = $dh->generatePublic($b);
$s = $dh->generateShared($a, $B);
$s2 = $dh->generateShared($b, $A);
print "A and B shared secrets match:\n";
print gmp_cmp($s, $s2) === 0 ? "Yes!\n\n" : "No :(\n\n";
print "Shared secret:\n";
print gmp_strval($s, 16) . "\n\n";
}