GHSA-X9QQ-236J-GJ97

Vulnerability from github – Published: 2023-12-05 23:32 – Updated: 2025-07-22 14:57
VLAI
Summary
Canonical LXD documentation improvement to make clear restricted.devices.disk=allow without restricted.devices.disk.paths also allows shift=true
Details

Summary

If a user has restricted access to a project that is configured with restricted=true, they can gain root access on the system by creating a disk device with shift=true and creating a setuid root executable. This is possible because the shift property is not restricted unless restricted.devices.disk.paths is set.

Details

The following patch shows the offending code with a possible fix:

--- a/lxd/device/disk.go
+++ b/lxd/device/disk.go
@@ -429,17 +429,19 @@ func (d *disk) validateEnvironmentSourcePath() error {
        if instProject.Name != api.ProjectDefaultName {
                // If restricted disk paths are in force, then check the disk's source is allowed, and record the
                // allowed parent path for later user during device start up sequence.
-               if shared.IsTrue(instProject.Config["restricted"]) && instProject.Config["restricted.devices.disk.paths"] != "" {
-                       allowed, restrictedParentSourcePath := project.CheckRestrictedDevicesDiskPaths(instProject.Config, d.config["source"])
-                       if !allowed {
-                               return fmt.Errorf("Disk source path %q not allowed by project for disk %q", d.config["source"], d.name)
+               if shared.IsTrue(instProject.Config["restricted"]) {
+                       if instProject.Config["restricted.devices.disk.paths"] != "" {
+                               allowed, restrictedParentSourcePath := project.CheckRestrictedDevicesDiskPaths(instProject.Config, d.config["source"])
+                               if !allowed {
+                                       return fmt.Errorf("Disk source path %q not allowed by project for disk %q", d.config["source"], d.name)
+                               }
+
+                               d.restrictedParentSourcePath = shared.HostPath(restrictedParentSourcePath)
                        }

                        if shared.IsTrue(d.config["shift"]) {
                                return fmt.Errorf(`The "shift" property cannot be used with a restricted source path`)
                        }
-
-                       d.restrictedParentSourcePath = shared.HostPath(restrictedParentSourcePath)
                }
        }

PoC

$ lxc project create restricted -c restricted=true -c restricted.devices.disk=allow
$ lxc project switch restricted
$ lxc profile device add default root disk path=/ pool=default
$ lxc init ubuntu:22.04 c1
$ lxc config device add c1 d1 disk source=/ path=/mnt shift=true
$ lxc start c1  # no error

$ lxc project set restricted restricted.devices.disk.paths=/  # explicitly allow mounting /
$ lxc restart c1
Error: Failed to start device "d1": The "shift" property cannot be used with a restricted source path

Created https://github.com/canonical/lxd/issues/12606 to improve the documentation as per https://github.com/canonical/lxd/security/advisories/GHSA-x9qq-236j-gj97#advisory-comment-91918

Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/canonical/lxd"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.19.0"
            },
            {
              "fixed": "5.20.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "5.19.0"
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/canonical/lxd"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.0.0-20230920084527-cbe39c5d3f14"
            },
            {
              "fixed": "0.0.0-20240118092008-ce1bd0dd37bb"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": true,
    "github_reviewed_at": "2023-12-05T23:32:58Z",
    "nvd_published_at": null,
    "severity": "LOW"
  },
  "details": "### Summary\n\nIf a user has restricted access to a project that is configured with `restricted=true`, they can gain root access on the system by creating a disk device with `shift=true` and creating a setuid root executable. This is possible because the `shift` property is not restricted unless `restricted.devices.disk.paths` is set.\n\n### Details\n\nThe following patch shows the offending code with a possible fix:\n```patch\n--- a/lxd/device/disk.go\n+++ b/lxd/device/disk.go\n@@ -429,17 +429,19 @@ func (d *disk) validateEnvironmentSourcePath() error {\n        if instProject.Name != api.ProjectDefaultName {\n                // If restricted disk paths are in force, then check the disk\u0027s source is allowed, and record the\n                // allowed parent path for later user during device start up sequence.\n-               if shared.IsTrue(instProject.Config[\"restricted\"]) \u0026\u0026 instProject.Config[\"restricted.devices.disk.paths\"] != \"\" {\n-                       allowed, restrictedParentSourcePath := project.CheckRestrictedDevicesDiskPaths(instProject.Config, d.config[\"source\"])\n-                       if !allowed {\n-                               return fmt.Errorf(\"Disk source path %q not allowed by project for disk %q\", d.config[\"source\"], d.name)\n+               if shared.IsTrue(instProject.Config[\"restricted\"]) {\n+                       if instProject.Config[\"restricted.devices.disk.paths\"] != \"\" {\n+                               allowed, restrictedParentSourcePath := project.CheckRestrictedDevicesDiskPaths(instProject.Config, d.config[\"source\"])\n+                               if !allowed {\n+                                       return fmt.Errorf(\"Disk source path %q not allowed by project for disk %q\", d.config[\"source\"], d.name)\n+                               }\n+\n+                               d.restrictedParentSourcePath = shared.HostPath(restrictedParentSourcePath)\n                        }\n\n                        if shared.IsTrue(d.config[\"shift\"]) {\n                                return fmt.Errorf(`The \"shift\" property cannot be used with a restricted source path`)\n                        }\n-\n-                       d.restrictedParentSourcePath = shared.HostPath(restrictedParentSourcePath)\n                }\n        }\n```\n\n### PoC\n\n```bash\n$ lxc project create restricted -c restricted=true -c restricted.devices.disk=allow\n$ lxc project switch restricted\n$ lxc profile device add default root disk path=/ pool=default\n$ lxc init ubuntu:22.04 c1\n$ lxc config device add c1 d1 disk source=/ path=/mnt shift=true\n$ lxc start c1  # no error\n\n$ lxc project set restricted restricted.devices.disk.paths=/  # explicitly allow mounting /\n$ lxc restart c1\nError: Failed to start device \"d1\": The \"shift\" property cannot be used with a restricted source path\n```\n\nCreated https://github.com/canonical/lxd/issues/12606 to improve the documentation as per https://github.com/canonical/lxd/security/advisories/GHSA-x9qq-236j-gj97#advisory-comment-91918",
  "id": "GHSA-x9qq-236j-gj97",
  "modified": "2025-07-22T14:57:33Z",
  "published": "2023-12-05T23:32:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/canonical/lxd/security/advisories/GHSA-x9qq-236j-gj97"
    },
    {
      "type": "WEB",
      "url": "https://github.com/canonical/lxd/issues/12606"
    },
    {
      "type": "WEB",
      "url": "https://github.com/canonical/lxd/commit/ce1bd0dd37bb3810fe6f16c237a4b65257f231f1"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/canonical/lxd"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [],
  "summary": "Canonical LXD documentation improvement to make clear restricted.devices.disk=allow without restricted.devices.disk.paths also allows shift=true"
}



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