Fix missing filename sanitization on V2 JSON character import + harden getPngName as safety nee (#5538)

* fix: sanitize character filenames on V2 JSON import and harden getPngName

- Add missing sanitize() call in importFromJson V2 spec branch to match all other import paths
- Sanitize data.name before readFromV2() so the name field sync happens automatically
- Add sanitize() as defense-in-depth inside getPngName() to catch future oversights
- Refactor getPngName() to use getUniqueName() utility for consistent name generation

* fix: sanitize data.name before readFromV2 in importFromPng and importFromCharX

Same bug as importFromJson: readFromV2() overwrites the top-level name
with the unsanitized data.name, undoing any prior sanitize() call.
Fix by sanitizing data.name before readFromV2 so the sync preserves it.

* fix: sanitize top-level name field in JSON and CharX import paths

* fix: incorrect path rejection in isPathUnderParent

* fix: increase maxTries in getPngName

---------

Co-authored-by: Cohee <18619528+Cohee1207@users.noreply.github.com>

src/endpoints/characters.js

@@ -772,10 +772,13 @@ async function importFromCharX(uploadPath, { request }, preservedFileName) {
     const { card, avatar, auxiliaryAssets, extractedBuffers } = await parser.parse();
 
     // Apply standard character transformations
+    if (card.data?.name) {
+        card.data.name = sanitize(card.data.name);
+    }
+    card.name = sanitize(card.data?.name || card.name);
     let processedCard = readFromV2(card);
     unsetPrivateFields(processedCard);
     processedCard.create_date = new Date().toISOString();
-    processedCard.name = sanitize(processedCard.name);
 
     const fileName = preservedFileName || getPngName(processedCard.name, request.user.directories);
     // Use the actual character name for asset folders, not the unique filename
@@ -887,9 +890,13 @@ async function importFromJson(uploadPath, { request }, preservedFileName) {
         console.info(`Importing from ${jsonData.spec} json`);
         importRisuSprites(request.user.directories, jsonData);
         unsetPrivateFields(jsonData);
+        if (jsonData.data?.name) {
+            jsonData.data.name = sanitize(jsonData.data.name);
+        }
+        jsonData.name = sanitize(jsonData.data?.name || jsonData.name);
         jsonData = readFromV2(jsonData);
         jsonData.create_date = new Date().toISOString();
-        const pngName = preservedFileName || getPngName(jsonData.data?.name || jsonData.name, request.user.directories);
+        const pngName = preservedFileName || getPngName(jsonData.name, request.user.directories);
         const char = JSON.stringify(jsonData);
         const result = await writeCharacterData(DEFAULT_AVATAR_PATH, char, pngName, request);
         return result ? pngName : '';
@@ -964,6 +971,9 @@ async function importFromPng(uploadPath, { request }, preservedFileName) {
 
     let jsonData = JSON.parse(imgData);
 
+    if (jsonData.data?.name) {
+        jsonData.data.name = sanitize(jsonData.data.name);
+    }
     jsonData.name = sanitize(jsonData.data?.name || jsonData.name);
     const pngName = preservedFileName || getPngName(jsonData.name, request.user.directories);
 
@@ -1529,13 +1539,9 @@ router.post('/chats', validateAvatarUrlMiddleware, async function (request, resp
  * @returns {string} - The name for the uploaded PNG file
  */
 function getPngName(file, directories) {
-    let i = 1;
+    file = sanitize(file);
-    const baseName = file;
+    return getUniqueName(file, (name) => fs.existsSync(path.join(directories.characters, `${name}.png`)),
-    while (fs.existsSync(path.join(directories.characters, `${file}.png`))) {
+        { nameBuilder: (base, i) => i === 0 ? base : `${base}${i}`, startIndex: 0, maxTries: 10000 }) ?? file;
-        file = baseName + i;
-        i++;
-    }
-    return file;
 }
 
 /**

src/util.js

@@ -1387,7 +1387,7 @@ export function isPathUnderParent(parentPath, childPath) {
 
     const relativePath = path.relative(normalizedParent, normalizedChild);
 
-    return !relativePath.startsWith('..') && !path.isAbsolute(relativePath);
+    return relativePath !== '..' && !relativePath.startsWith('..' + path.sep) && !path.isAbsolute(relativePath);
 }
 
 /**