Bug #71572 [NEW]: String offset assignment from an empty string inserts null byte

From: Date: Thu, 11 Feb 2016 22:12:49 +0000
Subject: Bug #71572 [NEW]: String offset assignment from an empty string inserts null byte
Groups: php.bugs 
Request: Send a blank email to php-bugs+get-199169@lists.php.net to get a copy of this message 
From:             francois
Operating system: Any
PHP version:      7.0.3
Package:          Strings related
Bug Type:         Bug
Bug description:String offset assignment from an empty string inserts null byte

Description:
------------
When assigning to a string offset from an empty string, the
corresponding byte is set to a null value.

In zend_assign_to_string_offset(), the length of the input string should
be checked. If 0, a warning should be raised and the string shouldn't be
modified.


Test script:
---------------
$str = "abc";
$str{0} = "";
var_dump($str);


Expected result:
----------------
PHP Fatal error:  Uncaught Error: Cannot assign an empty string to a
string offset in ...


Actual result:
--------------
string(3) "bc" (read as "\0bc")


-- 
Edit bug report at https://bugs.php.net/bug.php?id=71572&edit=1
-- 
Try a snapshot (PHP 5.4):   https://bugs.php.net/fix.php?id=71572&r=trysnapshot54
Try a snapshot (PHP 5.5):   https://bugs.php.net/fix.php?id=71572&r=trysnapshot55
Try a snapshot (trunk):     https://bugs.php.net/fix.php?id=71572&r=trysnapshottrunk
Fixed in SVN:               https://bugs.php.net/fix.php?id=71572&r=fixed
Fixed in release:           https://bugs.php.net/fix.php?id=71572&r=alreadyfixed
Need backtrace:             https://bugs.php.net/fix.php?id=71572&r=needtrace
Need Reproduce Script:      https://bugs.php.net/fix.php?id=71572&r=needscript
Try newer version:          https://bugs.php.net/fix.php?id=71572&r=oldversion
Not developer issue:        https://bugs.php.net/fix.php?id=71572&r=support
Expected behavior:          https://bugs.php.net/fix.php?id=71572&r=notwrong
Not enough info:            https://bugs.php.net/fix.php?id=71572&r=notenoughinfo
Submitted twice:            https://bugs.php.net/fix.php?id=71572&r=submittedtwice
register_globals:           https://bugs.php.net/fix.php?id=71572&r=globals
PHP 4 support discontinued: https://bugs.php.net/fix.php?id=71572&r=php4
Daylight Savings:           https://bugs.php.net/fix.php?id=71572&r=dst
IIS Stability:              https://bugs.php.net/fix.php?id=71572&r=isapi
Install GNU Sed:            https://bugs.php.net/fix.php?id=71572&r=gnused
Floating point limitations: https://bugs.php.net/fix.php?id=71572&r=float
No Zend Extensions:         https://bugs.php.net/fix.php?id=71572&r=nozend
MySQL Configuration Error:  https://bugs.php.net/fix.php?id=71572&r=mysqlcfg

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