content:// protocol
Last updated
Last updated
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This is a summary of the post https://census-labs.com/news/2021/04/14/whatsapp-mitd-remote-exploitation-CVE-2021-24027/
To list files managed by the Media Store, the command below can be used:
For a more human-friendly output, displaying only the identifier and path of each indexed file:
Content providers are isolated in their own private namespace. Access to a provider requires the specific content:// URI. Information about the paths for accessing a provider can be obtained from application manifests or the Android framework's source code.
Chrome on Android can access content providers through the content:// scheme, allowing it to access resources like photos or documents exported by third-party applications. To illustrate this, a file can be inserted into the Media Store and then accessed via Chrome:
Insert a custom entry into the Media Store:
Discover the identifier of the newly inserted file:
The file can then be viewed in Chrome using a URL constructed with the file's identifier.
For instance, to list files related to a specific application:
The Same Origin Policy (SOP) is a security protocol in browsers that restricts web pages from interacting with resources from different origins unless explicitly allowed by a Cross-Origin-Resource-Sharing (CORS) policy. This policy aims to prevent information leaks and cross-site request forgery. Chrome considers content:// as a local scheme, implying stricter SOP rules, where each local scheme URL is treated as a separate origin.
However, CVE-2020-6516 was a vulnerability in Chrome that allowed a bypass of SOP rules for resources loaded via a content:// URL. In effect, JavaScript code from a content:// URL could access other resources loaded via content:// URLs, which was a significant security concern, especially on Android devices running versions earlier than Android 10, where scoped storage was not implemented.
The proof-of-concept below demonstrates this vulnerability, where an HTML document, after being uploaded under /sdcard and added to the Media Store, uses XMLHttpRequest in its JavaScript to access and display the contents of another file in the Media Store, bypassing the SOP rules.
Proof-of-Concept HTML:
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