Non-Production API Endpoints for the Route 53 Service Fail to Log to CloudTrail Resulting in Silent Permission Enumeration

How it was found

Summary: Typically, when an adversary gains access to stolen AWS IAM credentials they will frequently test those credentials to see what access they have. They do this by performing API calls and seeing which succeed and which fail. There are even automated tools to make this process easier. For defenders and security professionals, this behavior serves as a golden opportunity for detection as it likely involves generating a large number of failed API call attempts. If an adversary could enumerate permissions without logging to CloudTrail, they could perform this activity invisibly.

There are many categories of CloudTrail bypass. The specific variant we will be focussed on in this report has been referred to as “non-production endpoint permission enumeration CloudTrail bypass”. If you would like to learn more about it, you can find more details here.

We have found 2 non-production endpoints for the Amazon Route 53 service which can be used with standard IAM credentials, and do not log to CloudTrail. While it is good that they don’t appear to have access to customer partition data, they can still be used for permission enumeration without logging to CloudTrail.

AWS has previously stated that this type of vulnerability should be reported. Specifically, “For isolated non-production endpoints that do not log to CloudTrail but are otherwise callable with normal credentials and exhibit normal IAM permission behavior, AWS considers the CloudTrail logging bypass of such endpoints also to be a security issue. If you find an API or APIs on an endpoint with these characteristics, please contact the AWS Security Team at [email protected]”.

Description:

Steps To Reproduce:

To see an example of what should appear in CloudTrail when using normal production endpoints, perform the following AWS CLI operation with a sufficiently privileged IAM user or role:

aws route53domains list-domains

Wait approximately 5-10 minutes and a log will appear in CloudTrail. Next, perform the following AWS CLI operation:

aws route53domains list-domains --endpoint-url ███████

After waiting 5-10 minutes (or longer), notice that it does not generate a log in CloudTrail. An adversary can perform this operation and depending on the response of the API make a determination if an Identity they have compromised does, or does not have permission to perform the operation.

Supporting Material/References:

• Indicate the Amazon service or product that this vulnerability occurs on:

route53domains

• What type of Amazon AWS account(s) is needed to verify or reproduce this vulnerability?:

Standard commercial partition account

• Estimated CVSS score and vector string:

4.3 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N/CR:X/IR:X/AR:X

• Estimated CWEs (comma separated):

CWE-778: Insufficient Logging

• Have you already publicly disclosed any information on this issue? If so, when and where?:

This specific example? No. This general technique? Yes, a lot actually. I’ve blogged about it here and spoke about it at Black Hat USA 2023 (███) and fwd:cloudsec 2023 (█████████) [I have broken these links because HackerOne appeared to complain about them?]

Additionally, we have reported similar findings for different services:

• redshift-data
• neptune-graph
• lakeformation and m2
• health
• glue
• globalaccelerator
• forecast
• events
• elasticache
• datazone part 2
• docdb-elastic
• devicefarm
• datazone
• cloudwatch
• bedrock
• bedrock-agent
• ssm

The following is the list of endpoints we found that exhibited this behavior.:

• ███
• ████████

Please note: We follow an industry standard 90-day vulnerability disclosure policy. You can read more about our policy here.

Impact

Summary:

An adversary can enumerate permissions of compromised credentials for the redshift-data service without logging to CloudTrail.