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AWS - Cognito Unauthenticated Enum

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Unauthenticated Cognito

Cognito is an AWS service that enable developers to grant their app users access to AWS services. Developers will grant IAM roles to authenticated users in their app (potentially people willbe able to just sign up) and they can also grant an IAM role to unauthenticated users.
For basic info about Cognito check:

Pacu modules for pentesting and enumeration

Pacu, the AWS exploitation framework, now includes the "cognito__enum" and "cognito__attack" modules that automate enumeration of all Cognito assets in an account and flag weak configurations, user attributes used for access control, etc., and also automate user creation (including MFA support) and privilege escalation based on modifiable custom attributes, usable identity pool credentials, assumable roles in id tokens, etc.
For a description of the modules' functions see part 2 of the blog post. For installation instructions see the main Pacu page.

Usage

Sample cognito__attack usage to attempt user creation and all privesc vectors against a given identity pool and user pool client:
Pacu (new:test) > run cognito__attack --username randomuser --email [email protected] --identity_pools
us-east-2:a06XXXXX-c9XX-4aXX-9a33-9ceXXXXXXXXX --user_pool_clients
59f6tuhfXXXXXXXXXXXXXXXXXX@us-east-2_0aXXXXXXX
Sample cognito__enum usage to gather all user pools, user pool clients, identity pools, users, etc. visible in the current AWS account:
Pacu (new:test) > run cognito__enum

Identity Pool ID

Identity Pools can grant IAM roles to unauthenticated users that just know the Identity Pool ID (which is fairly common to find), and attacker with this info could try to access that IAM role and exploit it. Moreoever, IAM roles could also be assigned to authenticated users that access the Identity Pool. If an attacker can register a user or already has access to the identity provider used in the identity pool you could access to the IAM role being given to authenticated users and abuse its privileges.

User Pool ID

By default Cognito allows to register new user. Being able to register a user might give you access to the underlaying application or to the authenticated IAM access role of an Identity Pool that is accepting as identity provider the Cognito User Pool. Check how to do that here.
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