question about database injection

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sudhakararaog
Forum Newbie
Posts: 13
Joined: Thu Jan 31, 2008 1:08 am

question about database injection

Post by sudhakararaog »

i am helping a friend to build a forum website which uses php and mysql database.

i am working on the registeration page for the forum website and its validation. i am using php 5.2.5 i am able to validate and do other tasks, however i really need help as i am stuck with regards to database injection.

please answer the following questions. any help will be greatly appreciated.

1. USER NAME VALIDATION

username = eregi("^[a-zA-Z0-9_ ]+$", $username)

with the above validation, a user can enter letters uppercase, lowercase and numbers and underscore with spaces ONLY ex=

9abc_def OR _abc123 = this IS INCORRECT

however i would like the username to be Letters First(upper or lowercase), followed by numbers and underscore and spaces in the username.

ex= abcd1234 OR ABcd1234 OR Ab_12 OR ab 12_cd OR 123456 OR 123abc = this IS CORRECT

i have used with preg_match as => if( $username == "" || !preg_match('/^[a-zA-Z0-9_]+$/x', $username) ) however its the same as eregi

QUESTION = how can i rewrite username = eregi("^[a-zA-Z0-9_ ]+$", $username) to match the following requirement.
username = abcd1234 OR ABcd1234 OR Ab_12 OR ab 12_cd OR 123456 OR 123abc
also with eregi("^[a-zA-Z0-9_ ]+$", $username) as there is a space if a user has more than 1 space ex= "ab cd 12" it is still accepting is there a way to restrict to ONE space only
ex = "ab cd12"

2. USING mysql_real_escape_string() METHOD

i am able to validate username, first name, phone numbers based on preg_match for these individual ones, however the form consists of some optional fields which i am not validating so if a user enters invalid characters in these optional fields i need to protect from sql injection, presently my code for mysql_real_escape_string() is as follows and the special characters
are still appearing in the database. i have not used mysql_real_escape_string() before so i guess i am missing something

$conn = mysql_connect($hostname, $user, $dbpassword);

$insertquery = sprintf("INSERT INTO tablename (`username`, `password`, `firstname`) VALUES ('%s', '%s', '%s')",

mysql_real_escape_string($username, $conn), mysql_real_escape_string($password, $conn), mysql_real_escape_string($firstname, $conn));

should i be checking for if(get_magic_quotes_gpc()) { } first.

NOTE = by using this mysql_real_escape_string() method php should NOT add slashes or other characters if this happens then the username will be stored in the table differently ex= john`smith instead it should be johnsmith the slashes can be done for other fields like firstname etc as this username and password will be used by a user to login to the forum

please advice about the procedure for mysql_real_escape_string() method

3. QUESTION ABOUT SQL INJECTION

presently if i enter special characters in the form these values are being inserted to the database as it is which is not good. out of the following methods
htmlentities(), addslashes(), trim(), mysql-real-escape-string() which is the best method to use to avoid sql injection
i think mysql-real-escape-string() is the best method.
NOTE = in my php settings magic_quotes_gpc is ON, magic_quotes_runtime is OFF, magic_quotes_sybase is OFF

4. STORING PASSWORDS

as part of the registration for the forum the username and password that the user enters in the registration page will be used as their username and password to login to the forum. presently when i execute the sql insert statement along with other fields for the registration page the value of the password stored in the mysql table is the actual characters that a user entered in the form. in the form the element is defined as <input type="password" name="password"> however in the table the password is stored as the actual characters the user entered in the form. is this a right way of storing the password field from the form.

NOTE = i believe with websites that are forum based using php and mysql, there is a way to pass information to the php file which will automatically pick up the username and password from the table that i have created where i am storing the username and password.

Please comment on storing the password in mysql table and how i can find the php file to which i can pass the value of username and password as a variable by using a function to that php and by including that php file in which i am processing the registration form.

Thanks a lot for reading my post. Any help will be greatly appreciated.
scriptah
Forum Commoner
Posts: 27
Joined: Sat Mar 15, 2008 8:58 pm
Location: Long Island, NY

Re: question about database injection

Post by scriptah »

Hello,

Lots of questions, I'll try to answer all of them.
1. Username validation.
First of all, you preg_match is usually faster than ereg, so I'll be using preg_match, and so should you.

Now you want the username to be first letters then numbers.
But you gave some examples of valid usernames which doesn't comply with this requirement: "123456 OR 123abc".

I'll stick to what you wrote before, "First letters then (the rest)"
You could try a pattern like this:

Code: Select all

 
$pattern = "/^[a-zA-Z]+[a-zA-Z0-9_]*[\s]?[a-zA-Z0-9_]*$/";
 
For example:

Code: Select all

 
<?php
 
$pattern = "/^[a-zA-Z]+[a-zA-Z0-9_]*[\s]?[a-zA-Z0-9_]*$/";
$usernames = array( "scriptah", "test1", "test  test", "d_t 1234", "1234", "____xxx" );
foreach( $usernames as $t )
{
    if( preg_match( $pattern, $t ) )
    {
        echo $t . " is a valid username <br />";
    }
    else
    {
        echo $t . " is an invalid username <br />";
    }
}
 
Output:

Code: Select all

 
scriptah is a valid username
test1 is a valid username
test  test is an invalid username
d_t 1234 is a valid username
1234 is an invalid username
____xxx is an invalid username
 
2. MySQL Escaping / SQL Injection.
Your question is should you check for magic_quotes_gpc prior to using mysql_real_escape_string.
The answer is yes, you should, if it is enabled, you should use stripslashes( ) prior calling mysql_real_escape_string, or you will end up escaping the data twice.

3. The best method agains SQL Injection.
The best approach is combining different strategies and not relying on one only.
You should always:
a. Filter your data.
b. Quote your data.
c. Escape your data.

addslashes() is your last resource for escaping data.
In case you're using MySQL, stick to mysql_real_escape_string.

And of course, GET RID OF magic_quotes_gpc already, its deprecated.

4. Storing the users password without any kind of encryption or one way hashing is not secure at all.
You suppose to use for example: sha1( ) or md5( ) to calculate the hash of the password, and store the hash not the password itself.
sudhakararaog
Forum Newbie
Posts: 13
Joined: Thu Jan 31, 2008 1:08 am

Re: question about database injection

Post by sudhakararaog »

thanks for letting me know about the password. i have presently defined the password field in the mysql table as varchar and specified 250 as the length.

1. is it ok to define the password field as varchar or should it be a specific datatype
2. is there any specific restriction on the character length for password field irrespective of the datatype.

please advice.

thanks.
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