Waraxe IT Security Portal  
  Login or Register
::  Home  ::  Search  ::  Your Account  ::  Forums  ::   Waraxe Advisories  ::  Tools  ::
November 24, 2020
Menu
 Home
 Logout
 Discussions
 Forums
 Members List
 IRC chat
 Tools
 Base64 coder
 MD5 hash
 CRC32 checksum
 ROT13 coder
 SHA-1 hash
 URL-decoder
 Sql Char Encoder
 Affiliates
 y3dips ITsec
 Md5 Cracker
 User Manuals
 AlbumNow
 Content
 Content
 Sections
 FAQ
 Top
 Info
 Feedback
 Recommend Us
 Search
 Journal
 Your Account



User Info
Welcome, Anonymous
Nickname
Password
(Register)

Membership:
Latest: MichaelSnaRe
New Today: 0
New Yesterday: 0
Overall: 9145

People Online:
Visitors: 324
Members: 0
Total: 324
PacketStorm News
Currently there is a problem with headlines from this site
Log in Register Forum FAQ Memberlist Search
IT Security and Insecurity Portal

www.waraxe.us Forum Index -> Php -> Protect varchar(255) Goto page 1, 2  Next
Post new topic  Reply to topic View previous topic :: View next topic 
Protect varchar(255)
PostPosted: Mon Jul 26, 2004 10:30 am Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




I write a piece of code that take from MySQL database a varchar(255) [e-mails, usernames, adresses...], how can protect from SQL Injection ?

I used strip_tags($variable)... is there a better command ?
View user's profile Send private message
PostPosted: Tue Jul 27, 2004 10:11 pm Reply with quote
madman
Active user
Active user
 
Joined: May 24, 2004
Posts: 46




Example:
Code:
$sql = "INSERT INTO table (strfield) VALUES ('" . quotemeta(addslashes($strfield)) ."')";


Or create a special function like this:
Code:
function qstr($text) {
if (strlen($text) == 0) return $text;
while (preg_match('/\\\'/', $text)) $text = str_replace("\\\'", "'", $text);
return quotemeta(addslashes($text));
}


$sql = "INSERT INTO table (strfield) VALUES ('" . qstr($strfield) ."')";


But this function is union-proof:
Code:
function nounion($text) {
if (strlen($text) == 0) return $text;
return preg_replace_callback('/(\'|u|n|i|o)/i', create_function('$match', 'return "&#".strval(ord($match)).";";'), $text);
}


$sql = "SELECT * FROM table WHERE strfield = ''" . nounion($strfield) ."'";


However, to avoid parser warning during SQL injection (and reveal your physical path), keep in touch with variables types. For any of string type, use the function above. For numeric types, always evaluate through appropriate functions (intval, floatval, etc or using typecasting) then passed directly to the sql query strings. E.g:
Code:
$int = intval($int);
$float = (float)$float;
$sql = "SELECT * FROM table WHERE int_val = '$int' AND float_val = '$float'";

_________________
ch88rs,
madman
View user's profile Send private message
heh
PostPosted: Tue Jul 27, 2004 10:18 pm Reply with quote
icenix
Advanced user
Advanced user
 
Joined: May 13, 2004
Posts: 106
Location: Australia




perfectly executed madman Very Happy
lol sounds like you answered that well

_________________
=[WWW.WARAXE.US]=
-Forum Rules
View user's profile Send private message Send e-mail Visit poster's website MSN Messenger
PostPosted: Sat Jul 31, 2004 9:14 am Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




Thanks 4 the Help Very Happy

I have 2 last questions:
- I have to call "nounion($text)" for every varchar variable before INSERTing in db and after SELECTing from database, or only before INSERT ? Confused
- Why in some PHPNuke patched modules (like encyclopedia admin) using only a "stripslashes(FixQuotes($text))" instead of a full preg_replace function ? Is a hole in security ? Confused

Thx 4 Helping a Noob
View user's profile Send private message
PostPosted: Sat Jul 31, 2004 8:33 pm Reply with quote
madman
Active user
Active user
 
Joined: May 24, 2004
Posts: 46




shmk wrote:
- I have to call "nounion($text)" for every varchar variable before INSERTing in db and after SELECTing from database, or only before INSERT ? Confused

UNION only affect to SELECT, so you can filter any variables through nounion() function only at SELECT query strings.

shmk wrote:
- Why in some PHPNuke patched modules (like encyclopedia admin) using only a "stripslashes(FixQuotes($text))" instead of a full preg_replace function ? Is a hole in security ? Confused

Because of simple reason, stripslashes() is a build-in PHP function and FixQuotes() is availables with most PHP-Nuke version (defined in mainfile.php). The patch maker keep the compatibility with most possible version (and upgrades) without worrying about "function not defined" error.

shmk wrote:
Thx 4 Helping a Noob

You're welcome. Smile

_________________
ch88rs,
madman
View user's profile Send private message
PostPosted: Sun Aug 01, 2004 10:11 pm Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




Some other questions:

1. A piece of code like:
$vartot = $var1 + $var2;
need some quotes to protect it ?

2. An update like:
$sql = "UPDATE table SET var=var+1, var2=var2-1 WHERE ...";
need something for protection ?

3. To protect a variable that get only value 0/1 I can use intval() or is there a better command ?

Thx Again Very Happy
View user's profile Send private message
PostPosted: Sun Aug 01, 2004 10:58 pm Reply with quote
madman
Active user
Active user
 
Joined: May 24, 2004
Posts: 46




shmk wrote:
1. A piece of code like:
$vartot = $var1 + $var2;
need some quotes to protect it ?

You may put a variable that hold numeric computation results using enclosed single-quotes inside query string. This applies to mySQL but another SQL might has different behavior. An example of integer computation:
Code:
$vartot = intval($var1) + intval($var2);
$vartot2 = intval($var3 + $var4);
$sql = "UPDATE table SET tot='$vartot', tot2='$vartot2' WHERE ...";


shmk wrote:
2. An update like:
$sql = "UPDATE table SET var=var+1, var2=var2-1 WHERE ...";
need something for protection ?

No you don't, as long as all statements are comes from internal SQL syntax and commands. Only "external" variables from PHP required to be "sanitized" or filtered into proper variable types. This example no need to filtered at all:
Code:
$sql = "UPDATE table SET var=var+1, var2=var2-1, var3=UNIX_TIMESTAMP(var4)+86400 WHERE ...";


shmk wrote:
3. To protect a variable that get only value 0/1 I can use intval() or is there a better command ?

Better if you evaluated the value before passed to SQL query string. This is an example code that evaluating input value, restrict to either 0 or 1, or fall to 0 (default) if does not meet the condition. I give you two safe codes for similar purpose, both are faster than if..then statement.
Code:
$value = (preg_match(/^[0-1]{1}$/', "$value")) ? intval($value) : 0;
$value2 = ($value2) ? 1 : 0;
$sql = "UPDATE table SET bool='$value', bool2='$value2' WHERE ...";


The first checking code ($value assignment) always expecting $value variable must be containing either 0 or 1 (one digit), otherwise 0 (default) will be used. The second code ($value2 assignment) can evaluate any types assigned to $value2 variable; numeric, string, array, etc. If $value2 is not-0 or not-null, or not-false or not-empty or not-"" or not-emptyarray, etc then $value2 will be assigned to 1 otherwise 0. Both are safe to be passed to SQL query because the values always either 0 or 1.

_________________
ch88rs,
madman
View user's profile Send private message
PostPosted: Mon Aug 02, 2004 9:19 am Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




MANY MANY thanks Very Happy
View user's profile Send private message
PostPosted: Mon Aug 02, 2004 4:23 pm Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




Always me... I hope that this time is my last question Cool

I'm using a link like:

/modules.php?name=ModuleName&op=FunctionName&variable=username

To protect the username I used
$username = stripslashes(FixQuotes(substr($username, 0, 24)))

All this concatened code can protect my variable and module or is completly useless ? Confused
View user's profile Send private message
PostPosted: Mon Aug 02, 2004 8:39 pm Reply with quote
madman
Active user
Active user
 
Joined: May 24, 2004
Posts: 46




shmk wrote:
Always me... I hope that this time is my last question Cool

I hope not. Smile
I love to discuss about security. I don't care even this thread being get millions page views and thousands replies. Very Happy

shmk wrote:
To protect the username I used
$username = stripslashes(FixQuotes(substr($username, 0, 24)))

All this concatened code can protect my variable and module or is completly useless ? Confused


To be honest, I never be sure to use FixQuotes() to filter string vars before passed to SQL query strings. The main functionality of this function is to replace a single-quote into two single-quotes (may work or not with some database) and two backslashes followed by a single-quote characters into a single-quote. This mean, your code above isn't safe to be passed into SQL query. Instead, use this:
Code:
$username = addslashes(FixQuotes($username));


Because we talking in the context of username string, we have to know how PHP-Nuke handles this string. From various version of PHP-Nuke (at least since 6.5), I found that accepted username as evaluated from Your_Account module always expecting only these following characters: alphanumerics (a-z), numeric (0-9), dashes (-), and underscores. Username's characters other than these rules will be rejected.

The problem is, because PHP-Nuke grown to become a popular CMS, then we have many add-ons or modules that overrides this basic security principal. People demanding for "strange" characters to their nick, such as "W@r@+3", "m/dm/n", "5h|^|x", or something similar. This makes things more complicated because not all these characters can be passed safely into database queries.

To accomodate this, we have to use more complex code. This is an example:
Code:
$username = quotemeta(addslashes(FixQuotes($username)));


If we want to stick on default PHP-Nuke username behavior, we can filter username using this code:
Code:
$username = (preg_match('/^[a-z0-9_-]+$/i', $username)) ? $username : '';
if ($username == '') die('invalid username');


The last code is more secure but has disadvantages, such as your existing users that already use "strange" characters will never be accepted or loose some site's benefits. The following code still allow user to pass but their username are filtered already and may look different than original:
Code:
$username = preg_replace('[^a-z0-9_-]*/i', '', $username));


I hope this is useful. Smile

_________________
ch88rs,
madman
View user's profile Send private message
PostPosted: Mon Aug 02, 2004 9:45 pm Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




I'll use this one becuase some users have special character on his names

$username = quotemeta(addslashes(FixQuotes($username)));

So substr() with this other function became useless ?
View user's profile Send private message
PostPosted: Mon Aug 02, 2004 10:50 pm Reply with quote
madman
Active user
Active user
 
Joined: May 24, 2004
Posts: 46




No, you still need substr. Smile
My codes above was only considered as example ( oh, the truth is I'm too lazy for typing Very Happy )

Here the working code:
Code:
$username = quotemeta(addslashes(FixQuotes(substr($username,0,25))));

_________________
ch88rs,
madman
View user's profile Send private message
PostPosted: Tue Aug 03, 2004 9:27 am Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




Confused after all this I have a REALLY stupid question (come in my mind after see some PHPNuke module)... Confused

Variable taked from database but not used later for sql INSERT or SELECT (only "echo" on page), have to be sanitize ? Embarassed


Omg I'm feel like a stupid, but thx again Very Happy


PS: the quotemeta(addslashes($strfield)) is union-proof ?
Be "union-proof" is usefull only if I use WHERE statement or in every INSERT/SELECT ?
View user's profile Send private message
PostPosted: Tue Aug 03, 2004 7:59 pm Reply with quote
madman
Active user
Active user
 
Joined: May 24, 2004
Posts: 46




shmk wrote:
Variable taked from database but not used later for sql INSERT or SELECT (only "echo" on page), have to be sanitize ? Embarassed

No, unless you do care with "dangerous" html tagging on the text string. This example will sanitize scripting tags in a string retrieved from database:
Code:
$result = $db->sql_query("SELECT msg FROM table WHERE cond=true");
if ($result)
{
  list($msg) = $db->sql_fetchrow($result);
  $db->sql_freeresult($result);
}
else
{
  $msg = '';
}

if ($msg != '') $msg = preg_replace('/\<(\/?script)[^\>]*\>/si', '&lt;\\1&gt;', $msg);


Echo command will always filtering escaped characters and displayed properly.

shmk wrote:
PS: the quotemeta(addslashes($strfield)) is union-proof ?

No. You need to use nounion() function that I was given.

shmk wrote:
Be "union-proof" is usefull only if I use WHERE statement or in every INSERT/SELECT ?

Use nounion() function only on SELECT query statements and on every external variables (any PHP variables with dollar sign) considered as string types.

_________________
ch88rs,
madman
View user's profile Send private message
PostPosted: Tue Aug 03, 2004 9:32 pm Reply with quote
shmk
Active user
Active user
 
Joined: Jul 22, 2004
Posts: 25




Thx again... saturday i'll leave for a 2 weeks holiday so I don't disturbe you no more Razz

Good Holiday Very Happy
View user's profile Send private message
Protect varchar(255)
  www.waraxe.us Forum Index -> Php
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
All times are GMT  
Page 1 of 2  
Goto page 1, 2  Next
  
  
 Post new topic  Reply to topic  




Powered by phpBB 2001-2008 phpBB Group






Space Raider game for Android, free download - Space Raider gameplay video - Zone Raider mobile games
All logos and trademarks in this site are property of their respective owner. The comments and posts are property of their posters, all the rest (c) 2004-2020 Janek Vind "waraxe"
Page Generation: 0.095 Seconds