A researcher at the security company Lightspin recently explained how she obtained credentials to an internal AWS service using a PostgreSQL extension and exploiting a local file read vulnerability on RDS. AWS confirmed the issue and deprecated dozens of minor versions of Amazon Aurora and RDS for PostgreSQL.
According to Amazon, database users with sufficient permissions could use these credentials to gain elevated access to resources associated with the database cluster from which they were obtained and could not be used to access internal RDS services or move between databases or AWS accounts.
Gafnit Amiga, director of security research at Lightspin, writes how she obtained credentials to an internal service Grover using a PostgreSQL extension, bypassing the log_fdw extension validation:
The log_fdw extension enables the user to access the database engine log using a SQL interface (...) I spent some time going over system files until I found an interesting argument in the PostgreSQL config file that was not shown through using psql (...) the apg_storage_conf_file which points to another configuration file with the name grover_volume.conf (...) the file content points to another file csd-grover-credentials.json.
This file let Amiga retrieve the temporary identity and access management (IAM) credentials, including a publicKey and privateKey that she could test and confirm being connected to an internal role called csd-grover-role. Amiga concludes:
Within transiting three different files I was able to discover an internal AWS service and gain access to it. This is where my analysis and research ended. I did not attempt to enumerate any IAM permissions or move further laterally into AWS' internal environment.
Source: https://blog.lightspin.io/aws-rds-critical-security-vulnerability
According to the security company, the vulnerability was reported to AWS on December 9th, more than four months ago, when the RDS team began working on investigation and remediation. AWS deployed an initial patch on the latest Aurora and RDS versions on December 14th, excluding older versions, and started to reach out to affected customers. In a security bulletin released on April 13th, the cloud provider claims:
AWS moved immediately to address this issue when it was reported. As part of our mitigation, we have updated Amazon Aurora PostgreSQL and Amazon RDS for PostgreSQL to prevent this issue. We have also deprecated the Amazon Aurora PostgreSQL and Amazon RDS for PostgreSQL minor versions (...)
The AWS advisory did not initially mention Lightspin and the lack of attribution raised further questions in the community. The announcement does not clarify what the internal service Grover is and how it works. Amiga confirms:
As for Grover, AWS are not able to disclose details about the internal service.
Scott Piper, a cloud security consultant who maintains a repository of Cloud Service Provider security mistakes, tweets on the latest discoveries by Lightspin:
In adding Lightspin's latest RDS issue to 'Cloud Service Provider security mistakes' I realized Amiga found the RDS issue one week after they found the Sagemaker issue! How many more hits do you have lined up?
It is not anymore possible to create an Aurora PostgreSQL or RDS for PostgreSQL instance with one of the following deprecated minor versions:
Aurora PostgreSQL
- 10.11, 10.12, 10.13
- 11.6, 11.7, 11.8
RDS for PostgreSQL
- 13.2, 13.1
- 12.6, 12.5, 12.4, 12.3, 12.2
- 11.11, 11.10, 11.9, 11.8, 11.7, 11.6, 11.5, 11.5, 11.4, 11.3, 11.2, 11.1
- 10.16, 10.15, 10.14, 10.13, 10.12, 10.11, 10.10, 10.9, 10.7, 10.6, 10.5, 10.4, 10.3, 10.1
- 9.6.21, 9.6.20, 9.6.19, 9.6.18, 9.6.17, 9.6.16, 9.6.15, 9.6.14, 9.6.12, 9.6.11, 9.6.10, 9.6.9, 9.6.8, 9.6.6, 9.6.5, 9.6.3, 9.6.2, 9.6.1
- 9.5, 9.4 and 9.3
