Input Validation / iOS URL Scheme Injection

Description

iOS URL Scheme Injection is a type of input validation vulnerability that occurs on mobile devices running iOS and in mobile applications. This vulnerability can allow attackers to inject malicious URLs into applications, allowing them to gain access to various data or functions within the application. The Common Weakness Enumeration (CWE) directory categorizes this vulnerability under CWE-79: Improper Neutralization of Input During Web Page Generation (Cross-site Scripting). The OWASP Testing Guide provides a detailed guide to testing for this vulnerability.

Risk

This vulnerability carries a high risk of allowing attackers to gain access to sensitive data or functions within the application. The risk assessment for this vulnerability is 10 out of 10, as defined by the OWASP Risk Rating Methodology.

Solution

The best way to mitigate this vulnerability is to perform proper input validation on all user-provided data. This can be achieved by validating user input against a list of accepted characters and rejecting all other input. Additionally, all URLs should be properly encoded to ensure that the URL does not contain malicious code.

Example

The following example code contains a vulnerability that could lead to an iOS URL Scheme Injection attack.

let urlString = "myapp://user?name=" + userInput
UIApplication.shared.openURL(URL(string: urlString)!)

In this example, the application is using user input as part of a URL without properly validating it. An attacker could inject malicious code into the URL and cause the application to execute it.