Bug #60116 [PATCH]: escapeshellcmd() cannot escape the chars which causes shell injection.
Edit report at https://bugs.php.net/bug.php?id=60116&edit=1
ID: 60116
Patch added by: hirokawa@php.net
Reported by: hirokawa@php.net
Summary: escapeshellcmd() cannot escape the chars which
causes shell injection.
Status: Open
Type: Bug
Package: Filter related
Operating System: Ubuntu Linux
PHP Version: trunk-SVN-2011-10-23 (SVN)
Block user comment: N
Private report: N
New Comment:
The following patch has been added/updated:
Patch Name: php-escape.patch
Revision: 1319368645
URL: https://bugs.php.net/patch-display.php?bug=60116&patch=php-escape.patch&revision=1319368645
Previous Comments:
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[2011-10-23 11:16:45] hirokawa@php.net
Description:
------------
escapeshellcmd() escapes " and ' only if it isn't paired (it is documented in
the PHP manual).
For the test script to look for some keyword in the files of the specified
directory (/var/data/), the double quotation in the user input as shown below
cannot be escaped because it is paired (it is found by Mr. Tokumaru).
$_GET['key'] = ':" "/etc/passwd';
The command line will be,
grep ":" "/etc/passwd" /var/data/*
The content of arbitrary file such as /etc/passwd will be shown.
The attached patch (made by Mr. Ohgaki, slightly modified be me) will add an
option flag for escapeshellcmd().
The recommended code to escape the quotation in this case will be,
$key = escapeshellcmd($_GET['key'], ESCAPE_CMD_ALL);
output: grep ":\" \"/etc/passwd" /var/data/*
The option flag has the three different value.
There is no backward incompatibility because the default behavior
(ESCAPE_CMD_PAIR) is unchanged.
ESCAPE_CMD_PAIR : escape if it is not paired (default)
ESCAPE_CMD_END : escape except for end/beginning of the string
ESCAPE_CMD_ALL : escape without exception (recommended)
In Windows, the quotation is always escaped, but, in other environment,
it is only escaped if it is not paired.
It is highly recommended to apply this patch to prevent the possible shell
command injection attack.
Test script:
---------------
<?php
$_GET['key'] = ':" "/etc/passwd'; // sample input
$key = escapeshellcmd($_GET['key']);
$cmd = "grep \"$key\" /var/data/*";
echo $cmd,PHP_EOL;
system($cmd);
?>
Expected result:
----------------
grep ":\" \"/etc/passwd" /var/data/*
Actual result:
--------------
grep ":" "/etc/passwd" /var/data/*
[content of /etc/passwd]
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Edit this bug report at https://bugs.php.net/bug.php?id=60116&edit=1
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