Merge commit from fork

* Add safe regex matching with timeouts and validation

* Remove redundant length check

* Remove timeouterror workaround

pyproject.toml

@@ -63,6 +63,7 @@ dependencies = [
   "pyzbar~=0.1.9",
   "rapidfuzz~=3.14.0",
   "redis[hiredis]~=5.2.1",
+  "regex>=2025.9.18",
   "scikit-learn~=1.7.0",
   "setproctitle~=1.3.4",
   "tika-client~=0.10.0",

src/documents/matching.py

@@ -20,6 +20,7 @@ from documents.models import Tag
 from documents.models import Workflow
 from documents.models import WorkflowTrigger
 from documents.permissions import get_objects_for_user_owner_aware
+from documents.regex import safe_regex_search
 
 if TYPE_CHECKING:
     from django.db.models import QuerySet
@@ -152,7 +153,7 @@ def match_storage_paths(document: Document, classifier: DocumentClassifier, user
 
 
 def matches(matching_model: MatchingModel, document: Document):
-    search_kwargs = {}
+    search_flags = 0
 
     document_content = document.content
 
@@ -161,14 +162,18 @@ def matches(matching_model: MatchingModel, document: Document):
         return False
 
     if matching_model.is_insensitive:
-        search_kwargs = {"flags": re.IGNORECASE}
+        search_flags = re.IGNORECASE
 
     if matching_model.matching_algorithm == MatchingModel.MATCH_NONE:
         return False
 
     elif matching_model.matching_algorithm == MatchingModel.MATCH_ALL:
         for word in _split_match(matching_model):
-            search_result = re.search(rf"\b{word}\b", document_content, **search_kwargs)
+            search_result = re.search(
+                rf"\b{word}\b",
+                document_content,
+                flags=search_flags,
+            )
             if not search_result:
                 return False
         log_reason(
@@ -180,7 +185,7 @@ def matches(matching_model: MatchingModel, document: Document):
 
     elif matching_model.matching_algorithm == MatchingModel.MATCH_ANY:
         for word in _split_match(matching_model):
-            if re.search(rf"\b{word}\b", document_content, **search_kwargs):
+            if re.search(rf"\b{word}\b", document_content, flags=search_flags):
                 log_reason(matching_model, document, f"it contains this word: {word}")
                 return True
         return False
@@ -190,7 +195,7 @@ def matches(matching_model: MatchingModel, document: Document):
             re.search(
                 rf"\b{re.escape(matching_model.match)}\b",
                 document_content,
-                **search_kwargs,
+                flags=search_flags,
             ),
         )
         if result:
@@ -202,16 +207,11 @@ def matches(matching_model: MatchingModel, document: Document):
         return result
 
     elif matching_model.matching_algorithm == MatchingModel.MATCH_REGEX:
-        try:
-            match = re.search(
-                re.compile(matching_model.match, **search_kwargs),
-                document_content,
-            )
-        except re.error:
-            logger.error(
-                f"Error while processing regular expression {matching_model.match}",
-            )
-            return False
+        match = safe_regex_search(
+            matching_model.match,
+            document_content,
+            flags=search_flags,
+        )
         if match:
             log_reason(
                 matching_model,

src/documents/regex.py

@@ -0,0 +1,50 @@
+from __future__ import annotations
+
+import logging
+import textwrap
+
+import regex
+from django.conf import settings
+
+logger = logging.getLogger("paperless.regex")
+
+REGEX_TIMEOUT_SECONDS: float = getattr(settings, "MATCH_REGEX_TIMEOUT_SECONDS", 0.1)
+
+
+def validate_regex_pattern(pattern: str) -> None:
+    """
+    Validate user provided regex for basic compile errors.
+    Raises ValueError on validation failure.
+    """
+
+    try:
+        regex.compile(pattern)
+    except regex.error as exc:
+        raise ValueError(exc.msg) from exc
+
+
+def safe_regex_search(pattern: str, text: str, *, flags: int = 0):
+    """
+    Run a regex search with a timeout. Returns a match object or None.
+    Validation errors and timeouts are logged and treated as no match.
+    """
+
+    try:
+        validate_regex_pattern(pattern)
+        compiled = regex.compile(pattern, flags=flags)
+    except (regex.error, ValueError) as exc:
+        logger.error(
+            "Error while processing regular expression %s: %s",
+            textwrap.shorten(pattern, width=80, placeholder="…"),
+            exc,
+        )
+        return None
+
+    try:
+        return compiled.search(text, timeout=REGEX_TIMEOUT_SECONDS)
+    except TimeoutError:
+        logger.warning(
+            "Regular expression matching timed out for pattern %s",
+            textwrap.shorten(pattern, width=80, placeholder="…"),
+        )
+        return None

src/documents/serialisers.py

@@ -71,6 +71,7 @@ from documents.parsers import is_mime_type_supported
 from documents.permissions import get_document_count_filter_for_user
 from documents.permissions import get_groups_with_only_permission
 from documents.permissions import set_permissions_for_object
+from documents.regex import validate_regex_pattern
 from documents.templating.filepath import validate_filepath_template_and_render
 from documents.templating.utils import convert_format_str_to_template_format
 from documents.validators import uri_validator
@@ -141,10 +142,10 @@ class MatchingModelSerializer(serializers.ModelSerializer):
             and self.initial_data["matching_algorithm"] == MatchingModel.MATCH_REGEX
         ):
             try:
-                re.compile(match)
-            except re.error as e:
+                validate_regex_pattern(match)
+            except ValueError as e:
                 raise serializers.ValidationError(
-                    _("Invalid regular expression: %(error)s") % {"error": str(e.msg)},
+                    _("Invalid regular expression: %(error)s") % {"error": str(e)},
                 )
         return match
 

src/documents/tests/test_matchables.py

@@ -206,6 +206,22 @@ class TestMatching(_TestMatchingBase):
     def test_tach_invalid_regex(self):
         self._test_matching("[", "MATCH_REGEX", [], ["Don't match this"])
 
+    def test_match_regex_timeout_returns_false(self):
+        tag = Tag.objects.create(
+            name="slow",
+            match=r"(a+)+$",
+            matching_algorithm=Tag.MATCH_REGEX,
+        )
+        document = Document(content=("a" * 5000) + "X")
+
+        with self.assertLogs("paperless.regex", level="WARNING") as cm:
+            self.assertFalse(matching.matches(tag, document))
+
+        self.assertTrue(
+            any("timed out" in message for message in cm.output),
+            f"Expected timeout log, got {cm.output}",
+        )
+
     def test_match_fuzzy(self):
         self._test_matching(
             "Springfield, Miss.",

uv.lock

@@ -2163,6 +2163,7 @@ dependencies = [
     { name = "pyzbar", marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
     { name = "rapidfuzz", marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
     { name = "redis", extra = ["hiredis"], marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
+    { name = "regex", marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
     { name = "scikit-learn", marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
     { name = "setproctitle", marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
     { name = "tika-client", marker = "sys_platform == 'darwin' or sys_platform == 'linux'" },
@@ -2306,6 +2307,7 @@ requires-dist = [
     { name = "pyzbar", specifier = "~=0.1.9" },
     { name = "rapidfuzz", specifier = "~=3.14.0" },
     { name = "redis", extras = ["hiredis"], specifier = "~=5.2.1" },
+    { name = "regex", specifier = ">=2025.9.18" },
     { name = "scikit-learn", specifier = "~=1.7.0" },
     { name = "setproctitle", specifier = "~=1.3.4" },
     { name = "tika-client", specifier = "~=0.10.0" },