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Date: Thu, 12 Mar 2015 14:28:48 +0100
Subject: php_stream_read(...) may return less than expected
From: salsi@icosaedro.it (Umberto Salsi)

Hi all,
I'm not a PHP internals developer, but this might be a bug spread here and
there in the source. This coding pattern:

if(php_stream_read(..., n) != n){
    php_error_docref(NULL TSRMLS_CC, E_SOMETHING, "Read error!");

seems wrong to me because there might be streams that returns less than
n bytes at once. When exactly n bytes are expected, not more not less,
a function similar to this one should be used instead:

int php_stream_read_fully(..., int n){
	continue calling php_stream_read() until exactly n bytes are
    collected, or a premature EOF, or I/O error
}

I ran into this issue passing a custom stream to getimagesize():

getimagesize("myprotocol://");

where myprotocol:// may, in some situations, return less bytes than
expected (see the http://php.net/manual/en/class.streamwrapper.php
wrapper class, stream_read() method). Looking at the implementation of
this function in ext/standard/image.c, I just found the pattern above.
If this is really a bug, many other functions might be affected.

Regards,
 ___ 
/_|_\  Umberto Salsi
\/_\/  www.icosaedro.it