Improper Authorization in Handler for Custom URL Scheme
The product uses a handler for a custom URL scheme, but it does not properly restrict which actors can invoke the handler using the scheme.
Mobile platforms and other architectures allow the use of custom URL schemes to facilitate communication between applications. In the case of iOS, this is the only method to do inter-application communication. The implementation is at the developer's discretion which may open security flaws in the application. An example could be potentially dangerous functionality such as modifying files through a custom URL scheme.
The following examples help to illustrate the nature of this weakness and describe methods or techniques which can be used to mitigate the risk.
Note that the examples here are by no means exhaustive and any given weakness may have many subtle varieties, each of which may require different detection methods or runtime controls.
This iOS application uses a custom URL scheme. The replaceFileText action in the URL scheme allows an external application to interface with the file incomingMessage.txt and replace the contents with the text field of the query string.
Application URL Handler
The handler has no restriction on who can use its functionality. The handler can be invoked using any method that invokes the URL handler such as the following malicious iframe embedded on a web page opened by Safari.
The attacker can host a malicious website containing the iframe and trick users into going to the site via a crafted phishing email. Since Safari automatically executes iframes, the user is not prompted when the handler executes the iframe code which automatically invokes the URL handler replacing the bookmarks file with a list of malicious websites. Since replaceFileText is a potentially dangerous action, an action that modifies data, there should be a sanity check before the writeToFile:withText: function.
A call into native code can then be initiated by passing parameters within the URL:
Because the application does not check the source, a malicious website loaded within this WebView has the same access to the API as a trusted site.
Weaknesses in this category are related to access control.
Weaknesses in this category are related to authorization components of a system. Frequently these deal with the ability to enforce that agents have the required permis...
Weaknesses in this category are related to the design and architecture of a system's authorization components. Frequently these deal with enforcing that agents have th...
This view (slice) covers all the elements in CWE.
CWE entries in this view (slice) are often seen in mobile applications.
This view (slice) lists weaknesses that can be introduced during implementation.