fix(gimp): escape Script-Fu path literals to prevent injection

Adds _script_fu_escape() to safely escape values embedded in
Script-Fu double-quoted strings. Prevents command injection through
crafted file paths containing quotes or control characters.

- Added _script_fu_escape() function for escaping backslashes, quotes,
  and control characters
- Updated create_and_export() to use safe path variants
- Updated apply_filter_and_export() to use safe path variants

Fixes: HKUDS#60

Author: penggaolai

gimp/agent-harness/cli_anything/gimp/utils/gimp_backend.py

@@ -7,11 +7,26 @@
 """
 
 import os
+import re
 import shutil
 import subprocess
 from typing import Optional
 
 
+def _script_fu_escape(s: str) -> str:
+    """Escape a string for safe embedding in Script-Fu double-quoted strings.
+    
+    Escapes backslash, double-quote, and control characters to prevent
+    Script-Fu injection through path literals.
+    """
+    # Escape backslash first, then double quotes, then other special chars
+    s = s.replace('\\', '\\\\')
+    s = s.replace('"', '\\"')
+    # Remove or escape control characters (newline, tab, etc.)
+    s = re.sub(r'[\x00-\x1f\x7f]', lambda m: f'\\x{ord(m.group()):02x}', s)
+    return s
+
+
 def find_gimp() -> str:
     """Find the GIMP executable. Raises RuntimeError if not found."""
     for name in ("gimp", "gimp-2.10", "gimp-2.99"):
@@ -73,6 +88,7 @@ def create_and_export(
 ) -> dict:
     """Create a new image in GIMP and export it."""
     abs_output = os.path.abspath(output_path)
+    safe_abs_output = _script_fu_escape(abs_output)
     os.makedirs(os.path.dirname(abs_output), exist_ok=True)
 
     ext = os.path.splitext(output_path)[1].lower()
@@ -81,22 +97,22 @@ def create_and_export(
     if ext == ".png":
         export_cmd = (
             f'(file-png-save RUN-NONINTERACTIVE image layer '
-            f'"{abs_output}" "{abs_output}" 0 9 1 1 1 1 1)'
+            f'"{safe_abs_output}" "{safe_abs_output}" 0 9 1 1 1 1 1)'
         )
     elif ext in (".jpg", ".jpeg"):
         export_cmd = (
             f'(file-jpeg-save RUN-NONINTERACTIVE image layer '
-            f'"{abs_output}" "{abs_output}" 0.85 0.0 0 0 "" 0 1 0 2)'
+            f'"{safe_abs_output}" "{safe_abs_output}" 0.85 0.0 0 0 "" 0 1 0 2)'
         )
     elif ext == ".bmp":
         export_cmd = (
             f'(file-bmp-save RUN-NONINTERACTIVE image layer '
-            f'"{abs_output}" "{abs_output}" 0)'
+            f'"{safe_abs_output}" "{safe_abs_output}" 0)'
         )
     else:
         export_cmd = (
             f'(gimp-file-overwrite RUN-NONINTERACTIVE image layer '
-            f'"{abs_output}" "{abs_output}")'
+            f'"{safe_abs_output}" "{safe_abs_output}")'
         )
 
     # Color mapping
@@ -162,28 +178,30 @@ def apply_filter_and_export(
 
     abs_input = os.path.abspath(input_path)
     abs_output = os.path.abspath(output_path)
+    safe_abs_input = _script_fu_escape(abs_input)
+    safe_abs_output = _script_fu_escape(abs_output)
     os.makedirs(os.path.dirname(abs_output), exist_ok=True)
 
     ext = os.path.splitext(output_path)[1].lower()
     if ext == ".png":
         export_cmd = (
             f'(file-png-save RUN-NONINTERACTIVE image drawable '
-            f'"{abs_output}" "{abs_output}" 0 9 1 1 1 1 1)'
+            f'"{safe_abs_output}" "{safe_abs_output}" 0 9 1 1 1 1 1)'
         )
     elif ext in (".jpg", ".jpeg"):
         export_cmd = (
             f'(file-jpeg-save RUN-NONINTERACTIVE image drawable '
-            f'"{abs_output}" "{abs_output}" 0.85 0.0 0 0 "" 0 1 0 2)'
+            f'"{safe_abs_output}" "{safe_abs_output}" 0.85 0.0 0 0 "" 0 1 0 2)'
         )
     else:
         export_cmd = (
             f'(gimp-file-overwrite RUN-NONINTERACTIVE image drawable '
-            f'"{abs_output}" "{abs_output}")'
+            f'"{safe_abs_output}" "{safe_abs_output}")'
         )
 
     script = (
         f'(let* ('
-        f'(image (car (file-png-load RUN-NONINTERACTIVE "{abs_input}" "{abs_input}")))'
+        f'(image (car (file-png-load RUN-NONINTERACTIVE "{safe_abs_input}" "{safe_abs_input}")))'
         f'(drawable (car (gimp-image-flatten image)))'
         f')'
         f'{script_fu_filter}'