SiYuan: Publish Reader Can Arbitrarily Delete Attribute View Files via `/api/av/removeUnusedAttributeView`

Summary

An authenticated publish-service reader can invoke /api/av/removeUnusedAttributeView and cause persistent deletion of arbitrary attribute view (AV) definition files from the workspace.

The route is protected only by generic CheckAuth, which accepts publish RoleReader requests. The handler forwards a caller-controlled id directly into a model function that deletes data/storage/av/<id>.json without verifying either:

• that the caller is allowed to perform write/destructive actions; or
• that the target AV is actually unused.

This is a persistent integrity and availability issue reachable from the publish surface.

Root Cause

1. Publish users are issued a RoleReader JWT

• kernel/model/auth.go

ClaimsKeyRole: RoleReader,

2. The publish reverse proxy forwards that token upstream

• kernel/server/proxy/publish.go
• kernel/server/proxy/publish.go

3. CheckAuth accepts RoleReader

• kernel/model/session.go

if role := GetGinContextRole(c); IsValidRole(role, []Role{
    RoleAdministrator,
    RoleEditor,
    RoleReader,
}) {
    c.Next()
    return
}

4. The route is exposed with CheckAuth only

• kernel/api/router.go

ginServer.Handle("POST", "/api/av/removeUnusedAttributeView", model.CheckAuth, removeUnusedAttributeView)

There is no CheckAdminRole and no CheckReadonly.

5. The handler forwards attacker-controlled id directly to the delete sink

• kernel/api/av.go

avID := arg["id"].(string)
model.RemoveUnusedAttributeView(avID)

6. The model deletes the AV file unconditionally

• kernel/model/attribute_view.go

func RemoveUnusedAttributeView(id string) {
    absPath := filepath.Join(util.DataDir, "storage", "av", id+".json")
    if !filelock.IsExist(absPath) {
        return
    }
    ...
    if err = filelock.RemoveWithoutFatal(absPath); err != nil {
        ...
        return
    }
    IncSync()
}

Crucially, this function does not verify that the supplied AV is actually unused. The name of the function suggests a cleanup helper, but the implementation is really "delete AV file by id if it exists".

Attack Prerequisites

• Publish service enabled
• Attacker can access the publish service
• If publish auth is enabled, attacker has valid publish-reader credentials
• Attacker knows an avID

Obtaining avID

avID is not secret. It is exposed extensively in frontend markup as data-av-id.

Examples:

• app/src/protyle/render/av/render.ts
• app/src/protyle/render/av/layout.ts
• app/src/protyle/render/av/groups.ts

Any publish-visible database/attribute view can therefore disclose a valid avID to the attacker.

Exploit Path

1. Attacker browses published content containing an attribute view.
2. Attacker extracts the data-av-id value from the page/DOM.
3. Attacker sends a POST request to /api/av/removeUnusedAttributeView through the publish service.
4. Publish proxy injects a valid RoleReader token.
5. CheckAuth accepts the request.
6. The handler passes the attacker-controlled avID to model.RemoveUnusedAttributeView.
7. The backend deletes data/storage/av/<avID>.json.

Proof of Concept

Request:

POST /api/av/removeUnusedAttributeView HTTP/1.1
Host: <publish-host>:<publish-port>
Content-Type: application/json
Authorization: Basic <publish-account-creds-if-enabled>

{
  "id": "<exposed-data-av-id>"
}

Expected result:

• HTTP 200
• backend increments sync state
• the target attribute view file is removed from data/storage/av/
• published and local workspace behavior for that AV becomes broken until restored from history or recreated

Impact

This gives a low-privileged publish reader a destructive persistent write primitive against workspace data.

Practical consequences include:

• deletion of live attribute view definitions
• corruption/breakage of published database views
• breakage of local workspace rendering and AV-backed relationships
• operational disruption until restore or manual repair

The bug affects integrity and availability, not merely UI state.

Recommended Fix

At minimum:

1. Block publish/read-only users from this route.
2. Require admin/write authorization.
3. Re-validate that the target AV is actually unused before deletion.

Safe router fix:

ginServer.Handle("POST", "/api/av/removeUnusedAttributeView",
    model.CheckAuth,
    model.CheckAdminRole,
    model.CheckReadonly,
    removeUnusedAttributeView,
)

And inside the model or handler, reject deletion unless the target id is present in UnusedAttributeViews(...).