Information exposure through Link header by guessing an allocated URI

NSS responds to unauthenticated and unauthorized GET requests to /foo/bar (that exists) by including the HTTP header:

Link: <bar.acl>; rel="acl", <bar.meta> rel="describedBy", <http://www.w3.org/ns/ldp#Resource>; rel="type"

For GET requests to non-existing resources eg. /foo/baz, the response doesn't include the HTTP Link header.

Thus, the security consideration: existence of a resource can potentially be known by guessing or anticipating an allocated URI.

There are use cases where the server may want to reveal the information in the Link header in the response. If the server doesn't make the distinction between intentionally revealing and unintentionally exposing, the server is encouraged to minimize information leaking. So, in the case here, it should be consistent by omitting the Link header for unauthenticated and unauthorized requests.

追蹤現有路徑與缺少路徑的 GET 請求處理及 Link header 產生。比較針對 /foo/bar 與 /foo/baz 的未驗證請求和未授權請求；完成的標準是，對於這些遭拒的請求，Link header 始終不存在，且測試涵蓋預期的資訊揭露行為。