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Introduction
In our recent blog, Who Do You Trust? OAuth Client Application Trends, we took a look at which OAuth applications were being trusted in a large dataset of anonymized Netskope customers, as well as raised some ideas of how to evaluate the risk involved based on the scopes requested and the number of users involved.
One of the looming questions that underlies assessing your application risk is: How does one identify applications? How do you know which application is which? Who is the owner/developer? as well as a host of other related questions such as which platform, version, or what is the release history and bugs associated with the application.
This is particularly problematic in the context of the trust these applications are granted in accessing user data or other resources in your organization.
This blog post delves deeper into the problems and outlines some approaches on how to deal with a lack of information and processes for application identity.
OAuth application trust
Let’s quickly review the OAuth application trust/approval process to explore what we know about the applications we’re trusting. Although we will look at Google OAuth applications, much of this applies to other OAuth providers as well.
An application (which could be a website/web app, native/mobile application, or device), when it needs to access a user’s data or resources, will redirect the user to an authorization service (e.g. Google Identity) to authenticate and authorize the access. Here’s a flow when logging into Google’s own gcloud CLI tool, which needs to access a user’s Google Cloud environment:
1. Application requests authorization by redirecting the user to the identity/authorization provide
$ gcloud auth login [email protected] --force
Your browser has been opened to visit:
https://accounts.google.com/o/oauth2/auth?response_type=code&client_id=32555940559.apps.googleusercontent.com&redirect_uri=http%3A%2F%2Flocalhost%3A8085%2F&scope=openid+https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fuserinfo.email+ht...
2. User authentication: Enters username
3. User authentication: Enters password
4. User authorization: The user is presented with a consent screen and approves the scopes requested by the application.
5. Confirmation message: In some cases, a successful authorization message is shown.
6. Application continues: The application has retrieved the user’s OAuth access token and can now access resources.
$ gcloud auth login [email protected] --force
Your browser has been opened to visit:
https://accounts.google.com/o/oauth2/auth?response_type=code&client_id=32555940559.apps.googleusercontent.com&redirect_uri=http%3A%2F%2Flocalhost%3A8085%2F&scope=openid+https%3A%2F%2Fwww.googleapis.com%2Fauth%2Fuserinfo.email+ht...
You are now logged in as [[email protected]].
$ gcloud projects list
From a user perspective, the application identity is given by the application name, Google Cloud SDK, which is seen in step #2 (initial login) along with a logo and steps #4 and #5 (authorization and confirmation). When the user is initiating a login process with an application they installed locally like gcloud CLI, this may not raise any concerns.
Application identity in the context of a phish
But if this were a phishing attack that starts with a fake application and steps #2 through #4, as we detail in the New Phishing Attacks Exploiting OAuth Authorization Flows series, then there are several concerns in terms of knowing whether to trust the application or not:
- The application name is arbitrary. In fact, it is set by the developer, and can be anything.
- Similarly, the logo could be nothing or any logo.
- Optionally, application developers can provide their domain, but it is not required
- The verbiage of what is trusting or accessing is confusing. Although tangential to application identity, it confuses everything for the user e.g.
- “Sign in to continue to Google Cloud SDK” in step #2 (wait, is that the name of the CLI?”
- “Google Cloud SDK wants to access your Google Account” in step #4 (my Google Account means my Google Cloud environment?)
- There is a verification process by Google, but is required only if you request sensitive or restricted scopes (e.g. admin-level privileges). In this case, gcloud CLI is verified by Google, so nothing is flagged. With an unverified application, after authenticating in steps #2 and #3, you would see a warning like this: