Description:
------------
Loading a hostile phar archive can cause an extensive memory allocation, that will trigger a fatal PHP error on 32 bit computers.

1) entry.filename_len is 4 bytes
2) value of 2 ** 32 - x can trigger an integer-overflow in the sanity check ( 0 < x <= 20):
if(entry.filename_len - 20 > (size_t)(endbuffer - buffer)){
3) later the call to "pestrndup" will crash:
pestrndup(buffer, entry.filename_len, entry.is_persistent);

The fix should be in 2 separate checks:
1) update the 1st check inside the loop from 4 to 24 (full entry size):
if (buffer + 24 < endbuffer){
2) avoid integer-overflow in the sanity check (20 because buffer was advanced by 4 already):
if(entry.filename_len > (size_t)(endbuffer - buffer) - 20){

Test script:
---------------
<?php
	$p = Phar::LoadPhar('example_hostile.phar', 'alias.phar');
	echo "Loaded the phar archive\n";
?>

Expected result:
----------------
The script should print the message

Actual result:
--------------
"

mmap() failed: [22] Invalid argument

mmap() failed: [22] Invalid argument
PHP Fatal error:  Out of memory (allocated 2097152) (tried to allocate 4294967277 bytes) in XXX on line 2
"