Description

Argument Injection or Modification is a specific case of attack, which belongs to Injection attacks familly. Modifying or injecting data as arguments the attacker may lead to very simmilar, often the same results as in other injection attacks. It plays no difference if the attacker wants to inject the system command into argument or into any other part of the code.

Examples

Example 1

Knowing pseudo code of the application the attacker may guess, what action is required by the application to perform another one. E.g. what must be done to authorize the attacker as the administrator.

Reading the code below the attacker doesn't know the values of $pass and $login. The question is - is there possiblity of altering value of $authorized not knowing previously mentioned variables?

$authorized=0;

if($pass = "XXX" and $login = "XXX") { $authorized = 1; }
if($authorized == 1) { admin_panel(); }

If server configuration allows for that, we may try to pass argument $authorized=1 as input data to application.

E.g. /index.php?user=&pass=&authorized=1

Example 2

If security mechanism doesn't protect data as it should, e.g. doesn't check the identity of the user and private data are displayed to him despite of fact they shouldn't, then such user may try to alter arguments and get access to data owned by a different user.

E.g. By entering address http://testsite.com/index.php?invoice=12 user is able to check one of his invoices. Modifying "invoice" argument, considering above assumptions, the attacker may try to access other user's invoices. Usefull to the attacker in this example would be performing a brute-force attack.

Countermeasures

- validation of the format / expected classes of charachetrs / input/output data size