GHSA-wvhv-qcqf-f3cx: goshs has a file-based ACL authorization bypass in goshs state-changing routes
Summarygoshs enforces the documented per-folder `.goshs` ACL/basic-auth mechanism for directory listings and file reads, but it does not enforce the same authorization checks for state-changing routes. An unauthenticated attacker can upload files with `PUT`, upload files with multipart `POST /upload`, create directories with `?mkdir`, and delete files with `?delete` inside a `.goshs`-protected directory. By deleting the `.goshs` file itself, the attacker can remove the folder's auth policy and then access previously protected content without credentials. This results in a critical authorization bypass affecting confidentiality, integrity, and availability.DetailsThe project README explicitly documents file-based ACLs as a security feature:`README.md:59` - "You can place a .goshs in any folder to apply custom ACLs"`README.md:61` - "You can apply custom basic auth per folder"The read/list path correctly enforces `.goshs`:`httpserver/filebased.go:10-49` loads `.goshs``httpserver/handler.go:68-91` calls `findSpecialFile()` for directories`httpserver/handler.go:94-101` calls `findSpecialFile()` for files`httpserver/handler.go:285-305` applies custom auth`httpserver/handler.go:545-565` enforces folder auth during directory rendering`httpserver/handler.go:590-630` enforces file auth and blocked entries during file servingHowever, the state-changing routes bypass this logic entirely:`httpserver/server.go:94-100` routes multipart `POST /.../upload` directly to `upload()``httpserver/server.go:105-109` routes `PUT` directly to `put()``httpserver/handler.go:119-123` dispatches `?mkdir` directly to `handleMkdir()``httpserver/handler.go:181-187` dispatches `?delete` directly to `deleteFile()``httpserver/updown.go:18-60` writes files for `PUT` without checking `.goshs``httpserver/updown.go:63-165` writes files for multipart upload without checking `.goshs``httpserver/handler.go:679-698` deletes files with `os.RemoveAll()` without checking `.goshs``httpserver/handler.go:901-937` creates directories with `os.MkdirAll()` without checking `.goshs`This is not a path traversal issue. The path remains inside the configured root after sanitization. The vulnerability is that authorization is applied inconsistently: reads are protected, but writes and deletes are not. Because `.goshs` itself can be deleted through the unauthenticated delete route, the attacker can escalate the impact from unauthorized modification to full removal of the folder's auth barrier.PoCEnvironment used for verification:Repository/module: `github.com/patrickhener/goshs`Verified vulnerable tag: `v2.0.0-beta.3`Also present in the `v1.1.4` line based on code inspectionLocal host: `127.0.0.1:18091`Build and setup:In a second terminal:Expected results:Note: if using `zsh`, the URL containing `?delete` must be quoted, or the shell will treat `?` as a wildcard and the request will not be sent.PoC Video for reference:https://github.com/user-attachments/assets/deb9106e-6dfa-47c0-95c1-993c2cbc9ee7ImpactThis is an authorization bypass affecting deployments that rely on `.goshs` for per-folder protection. A remote unauthenticated attacker can:create or overwrite files inside a folder that should require authenticationcreate directories inside the protected folderdelete arbitrary files reachable through the vulnerable route inside that protected folderdelete the `.goshs` policy file itselfread previously protected files once the policy file has been removedIn practice, this breaks the security boundary promised by the file-based ACL feature and can expose sensitive files while also allowing unauthorized modification or destruction of protected content.RemediationEnforce `.goshs` authorization checks for all state-changing operations, not just read/list flows. Before `PUT`, multipart upload, delete, and mkdir, resolve the effective folder ACL and deny the request unless the caller satisfies `acl.Auth`.Protect `.goshs` as a special file in mutation handlers. The application already prevents serving `.goshs`; it should also reject deletion, overwrite, or replacement of `.goshs` through HTTP routes unless the request is properly authorized.Add regression tests covering protected folders for every mutation path. The test suite should verify that `PUT`, `POST /upload`, `?delete`, and `?mkdir` all fail without valid credentials when a `.goshs` file is present.
CVSS v4.0: 9.3
CVSS v3.1: 9.8