Clean up

app/core/src/main/java/stirling/software/SPDF/controller/web/SignatureController.java

@@ -53,8 +53,6 @@ public class SignatureController {
         String lowerFileName = fileName.toLowerCase();
         if (lowerFileName.endsWith(".jpg") || lowerFileName.endsWith(".jpeg")) {
             contentType = MediaType.IMAGE_JPEG;
-        } else if (lowerFileName.endsWith(".gif")) {
-            contentType = MediaType.IMAGE_GIF;
         }
 
         return ResponseEntity.ok().contentType(contentType).body(imageBytes);

app/core/src/main/java/stirling/software/SPDF/service/SignatureService.java

@@ -101,16 +101,35 @@ public class SignatureService {
 
     private boolean isImageFile(Path path) {
         String fileName = path.getFileName().toString().toLowerCase();
-        return fileName.endsWith(".jpg")
-                || fileName.endsWith(".jpeg")
-                || fileName.endsWith(".png")
-                || fileName.endsWith(".gif");
+        return fileName.endsWith(".jpg") || fileName.endsWith(".jpeg") || fileName.endsWith(".png");
     }
 
     private void validateFileName(String fileName) {
         if (fileName.contains("..") || fileName.contains("/") || fileName.contains("\\")) {
             throw new IllegalArgumentException("Invalid filename");
         }
+        // Only allow alphanumeric, hyphen, and underscore
+        if (!fileName.matches("^[a-zA-Z0-9_-]+$")) {
+            throw new IllegalArgumentException("Filename contains invalid characters");
+        }
+    }
+
+    private String validateAndNormalizeExtension(String extension) {
+        String normalized = extension.toLowerCase().trim();
+        // Whitelist only safe image extensions
+        if (normalized.equals("png") || normalized.equals("jpg") || normalized.equals("jpeg")) {
+            return normalized;
+        }
+        throw new IllegalArgumentException("Unsupported image extension: " + extension);
+    }
+
+    private void verifyPathWithinDirectory(Path resolvedPath, Path targetDirectory)
+            throws IOException {
+        Path canonicalTarget = targetDirectory.toAbsolutePath().normalize();
+        Path canonicalResolved = resolvedPath.toAbsolutePath().normalize();
+        if (!canonicalResolved.startsWith(canonicalTarget)) {
+            throw new IOException("Resolved path is outside the target directory");
+        }
     }
 
     /** Save a signature as image file */
@@ -145,13 +164,18 @@ public class SignatureService {
             String base64Data = dataUrl.substring(dataUrl.indexOf(",") + 1);
             byte[] imageBytes = Base64.getDecoder().decode(base64Data);
 
-            // Determine file extension from data URL
+            // Determine and validate file extension from data URL
             String mimeType = dataUrl.substring(dataUrl.indexOf(":") + 1, dataUrl.indexOf(";"));
-            String extension = mimeType.substring(mimeType.indexOf("/") + 1);
+            String rawExtension = mimeType.substring(mimeType.indexOf("/") + 1);
+            String extension = validateAndNormalizeExtension(rawExtension);
 
             // Save image file only
             String imageFileName = request.getId() + "." + extension;
             Path imagePath = targetFolder.resolve(imageFileName);
+
+            // Verify path is within target directory
+            verifyPathWithinDirectory(imagePath, targetFolder);
+
             Files.write(
                     imagePath,
                     imageBytes,

frontend/src/core/components/tools/sign/SavedSignaturesSection.tsx

@@ -26,7 +26,7 @@ export const SavedSignaturesSection = ({
   signatures,
   disabled = false,
   isAtCapacity,
-  storageType,
+  storageType: _storageType,
   onUseSignature,
   onDeleteSignature,
   onRenameSignature,

frontend/src/core/hooks/tools/sign/useSavedSignatures.ts

@@ -1,7 +1,6 @@
 import { useCallback, useEffect, useMemo, useState } from 'react';
 import { signatureStorageService, type StorageType } from '@app/services/signatureStorageService';
 
-const STORAGE_KEY = 'stirling:saved-signatures:v1';
 export const MAX_SAVED_SIGNATURES = 10;
 
 export type SavedSignatureType = 'canvas' | 'image' | 'text';

frontend/src/core/services/signatureStorageService.ts

@@ -1,5 +1,5 @@
 import apiClient from '@app/services/apiClient';
-import type { SavedSignature, SavedSignaturePayload } from '@app/hooks/tools/sign/useSavedSignatures';
+import type { SavedSignature } from '@app/hooks/tools/sign/useSavedSignatures';
 
 export type StorageType = 'backend' | 'localStorage';
 
@@ -41,7 +41,7 @@ class SignatureStorageService {
   private async _performDetection(): Promise<SignatureStorageCapabilities> {
     try {
       // Probe the signatures endpoint
-      const response = await apiClient.get('/api/v1/general/signatures', {
+      await apiClient.get('/api/v1/general/signatures', {
         timeout: 3000,
       });