GHSA-55R9-5MX9-QQ7R
Vulnerability from github – Published: 2024-07-09 21:04 – Updated: 2024-07-10 18:34Summary
Cache driver GetBlob() allows read access to any blob without access control check
Details
If a Zot accessControl policy allows users read access to some repositories but restricts read access to other repositories and dedupe is enabled (it is enabled by default), then an attacker who knows the name of an image and the digest of a blob (that they do not have read access to), they may maliciously read it via a second repository they do have read access to. This allows an attacker to read an image that the accessControl policy denies.
This attack is possible because ImageStore.CheckBlob() calls checkCacheBlob() to find the blob a global cache by searching for the digest. If it is found, it is copied to the user requested repository with copyBlob().
This cache behavior is intentionally used in RouteHandler.CreateBlobUpload() to implement cross repository blob mount (POST /v2/<name>/blobs/uploads/?mount=<digest>&from=<repository name>) in Zot. This is still missing an access control to check read access on the source repository.
This cache behavior is unexpectedly also used in RouteHandler.CheckBlob() too for HEAD /v2/<name>/blobs/<digest>. If a blob is requested that does not exist on the requested repository, Zot will search for it in a global cache (possibly returning a result from an from an incorrect repository) and then will store it into the ImageStore for the requested repository.
RouteHandler.GetBlob() does not call ImageStore.CheckBlob() so it is not directly vulnerable. However an attacker with only limited read access may first call CheckBlob() to fetch the blob from the cache, then call GetBlob() to read the blob.
Mitigation
The attack may be mitigated by configuring "dedupe": false in the "storage" settings. This disables Zot's cache drivers. dedupe is enabled by default using the BoltDB cache driver.
Impact
An attacker can read images that the accessControl policy denies if they have read access to any other second repository.
This attack only allows accessing blobs (both config and layers) by digest. Manifests cannot be accessed.
This attack requires the attacker to know the name of a private image and its layer digests. A scenario where this might happen is if a project has public CI build logs but publishes the image to a private repository. Many image build tools log layer digests.
{
"affected": [
{
"package": {
"ecosystem": "Go",
"name": "zotregistry.io/zot"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.0"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "Go",
"name": "zotregistry.dev/zot"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "2.1.0"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2024-39897"
],
"database_specific": {
"cwe_ids": [
"CWE-639"
],
"github_reviewed": true,
"github_reviewed_at": "2024-07-09T21:04:00Z",
"nvd_published_at": "2024-07-09T19:15:12Z",
"severity": "MODERATE"
},
"details": "### Summary\n\nCache driver `GetBlob()` allows read access to any blob without access control check\n\n### Details\n\nIf a Zot `accessControl` policy allows users read access to some repositories but restricts read access to other repositories and `dedupe` is enabled (it is enabled by default), then an attacker who knows the name of an image and the digest of a blob (that they do not have read access to), they may maliciously read it via a second repository they do have read access to. This allows an attacker to read an image that the `accessControl` policy denies.\n\nThis attack is possible because [`ImageStore.CheckBlob()` calls `checkCacheBlob()`](https://github.com/project-zot/zot/blob/v2.1.0-rc2/pkg/storage/imagestore/imagestore.go#L1158-L1159) to find the blob a global cache by searching for the digest. If it is found, it is copied to the user requested repository with `copyBlob()`.\n\nThis cache behavior is intentionally used in [`RouteHandler.CreateBlobUpload()`](https://github.com/project-zot/zot/blob/v2.1.0-rc2/pkg/api/routes.go#L1194-L1197) to implement cross repository blob mount (`POST /v2/\u003cname\u003e/blobs/uploads/?mount=\u003cdigest\u003e\u0026from=\u003crepository name\u003e`) in Zot. This is still missing an access control to check read access on the source repository.\n\nThis cache behavior is unexpectedly also used in [`RouteHandler.CheckBlob()`](https://github.com/project-zot/zot/blob/v2.1.0-rc2/pkg/api/routes.go#L886) too for `HEAD /v2/\u003cname\u003e/blobs/\u003cdigest\u003e`. If a blob is requested that does not exist on the requested repository, Zot will search for it in a global cache (possibly returning a result from an from an incorrect repository) and then will store it into the `ImageStore` for the requested repository.\n\n[`RouteHandler.GetBlob()`](https://github.com/project-zot/zot/blob/v2.1.0-rc2/pkg/api/routes.go#L1000) does _not_ call `ImageStore.CheckBlob()` so it is not directly vulnerable. However an attacker with only limited read access may first call `CheckBlob()` to fetch the blob from the cache, then call `GetBlob()` to read the blob.\n\n### Mitigation\n\nThe attack may be mitigated by configuring `\"dedupe\": false` in the `\"storage\"` settings. This disables Zot\u0027s cache drivers. `dedupe` is enabled by default using the BoltDB cache driver.\n\n### Impact\n\nAn attacker can read images that the `accessControl` policy denies if they have read access to any other second repository.\n\nThis attack only allows accessing blobs (both config and layers) by digest. Manifests cannot be accessed.\n\nThis attack requires the attacker to know the name of a private image and its layer digests. A scenario where this might happen is if a project has public CI build logs but publishes the image to a private repository. Many image build tools log layer digests.\n",
"id": "GHSA-55r9-5mx9-qq7r",
"modified": "2024-07-10T18:34:34Z",
"published": "2024-07-09T21:04:00Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/project-zot/zot/security/advisories/GHSA-55r9-5mx9-qq7r"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-39897"
},
{
"type": "WEB",
"url": "https://github.com/project-zot/zot/commit/aaee0220e46bdadd12115ac67c19f9d3153eb1df"
},
{
"type": "PACKAGE",
"url": "https://github.com/project-zot/zot"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Cache driver GetBlob() allows read access to any blob without access control check"
}
Sightings
| Author | Source | Type | Date |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.