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Bug #50979 FastCGI/CGI runtime selection error
Submitted: 2010-02-09 20:53 UTC Modified: 2013-02-18 00:34 UTC
From: php at linepoint dot com Assigned: dmitry (profile)
Status: No Feedback Package: CGI/CLI related
PHP Version: 5.3.1 OS: Freebsd
Private report: No CVE-ID: None
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 [2010-02-09 20:53 UTC] php at linepoint dot com
Description:
------------
PHP v5.3+ now forces fastcgi support to be compiled into the executable, and upon execution of php-cgi, auto selects which mode (fastcgi/cgi) is to be used.

In some circumstances, it can guess incorrectly and use fastcgi mode when cgi mode should be used.

PHP's method of checking in sapi/cgi/fastcgi.c (line ~230) uses the errno returned (ENOTCONN) as an assumption that a local/unix socket connection must be a fastcgi call.

A alternative or secondary check should be implemented to verify that it's truly a fastcgi execution.

This problem was initially found when working with the Zeus Webserver (http://www.zeus.com), but can be reproduced with other systems that work the same way.

Reproduce code:
---------------
When php-cgi is called from a webserver, it checks stdin (fd 0) with a getpeername call to see if it's reading via a socket or not.  In some circumstances/webservers, php-cgi can be called using local sockets instead of file, but not be executed with fastcgi hooks.

Code in question:
--- sapi/cgi/fastcgi.c.orig     2010-02-09 12:25:49.000000000 -0500
                }
 #else
                errno = 0;
                if (getpeername(0, (struct sockaddr *)&sa, &len) != 0 && errno == ENOTCONN) {
                        fcgi_setup_signals();
                        return is_fastcgi = 1;
                } else {

---



Expected result:
----------------
Expected result is that fastcgi mode is used for fastcgi calls, and cgi mode is used for cgi calls.

A "proof of concept" patch which fixes the issue (this is not a final patch due to the fact the environmental variable checked is optional, not mandatory)

--- sapi/cgi/fastcgi.c.orig     2010-02-09 12:25:49.000000000 -0500
+++ sapi/cgi/fastcgi.c  2010-02-09 12:26:50.000000000 -0500
@@ -228,7 +228,7 @@
                }
 #else
                errno = 0;
-               if (getpeername(0, (struct sockaddr *)&sa, &len) != 0 && errno == ENOTCONN) {
+               if (getpeername(0, (struct sockaddr *)&sa, &len) != 0 && errno == ENOTCONN && getenv ("PHP_FCGI_CHILDREN") ) {
                        fcgi_setup_signals();
                        return is_fastcgi = 1;
                } else {


Actual result:
--------------
The current code auto selects fastcgi mode, when cgi mode is the desired result.

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 [2010-04-20 16:36 UTC] dmitry@php.net
-Status: Assigned +Status: Feedback
 [2010-04-20 16:36 UTC] dmitry@php.net
The getpeername() check came from the reference libfcgi implementation.

The additional check for getenv("PHP_FCGI_CHILDREN") is not correct because PHP_FCGI_CHILDREN don't have to be set.

Really I can't find out a different check which will portable across different FastCGI managers.

Especially for Zeus (and any other web server which supports FastCGI) I would suggest to use FastCGI instead of CGI.
 [2013-02-18 00:34 UTC] php-bugs at lists dot php dot net
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