CVE-2023-37481 (published 2023-07-18T19:15Z)

Fides is an open-source privacy engineering platform for managing data privacy requests and privacy regulations. The Fides webserver is vulnerable to a type of Denial of Service (DoS) attack. Attackers can exploit this vulnerability to upload zip files containing malicious SVG bombs (similar to a billion laughs attack), causing resource exhaustion in Admin UI browser tabs and creating a persistent denial of service of the 'new connector' page (`datastore-connection/new`). This vulnerability affects Fides versions `2.11.0` through `2.15.1`. Exploitation is limited to users with elevated privileges with the `CONNECTOR_TEMPLATE_REGISTER` scope, which includes root users and users with the owner role. The vulnerability has been patched in Fides version `2.16.0`. Users are advised to upgrade to this version or later to secure their systems against this threat. There is no known workaround to remediate this vulnerability without upgrading.

CVSS v3 base score: 4.9, MEDIUM (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H)

Weakness information:
cwe_id: CWE-400
cwe_name: Uncontrolled Resource Consumption
description: The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources.
extended_description: 
            Limited resources include memory, file system storage, database connection pool entries, and CPU. If an attacker can trigger the allocation of these limited resources, but the number or size of the resources is not controlled, then the attacker could cause a denial of service that consumes all available resources. This would prevent valid users from accessing the product, and it could potentially have an impact on the surrounding environment. For example, a memory exhaustion attack against an application could slow down the application as well as its host operating system.
            There are at least three distinct scenarios which can commonly lead to resource exhaustion:
               
                  Lack of throttling for the number of allocated resources
                  Losing all references to a resource before reaching the shutdown stage
                  Not closing/returning a resource after processing
               
            Resource exhaustion problems are often result due to an incorrect implementation of the following situations:
               
                  Error conditions and other exceptional circumstances.
                  Confusion over which part of the program is responsible for releasing the resource.
               
         
         

Fix information:
repo_url: https://github.com/ethyca/fides
commit_details: repo_url: https://github.com/ethyca/fides
author: Adrian Galvan
author_date: 2023-07-06 10:40:19-07:00
msg: Merge pull request from GHSA-3rw2-wfc8-wmj5

* Adding checks for malicious SVGs

* Fixing merge conflicts

---------

Co-authored-by: Dave Quinlan <83430497+daveqnet@users.noreply.github.com>
repository: repo_url: https://github.com/ethyca/fides
repo_name: ethyca/fides
description: The Privacy Engineering & Compliance Framework
repo_language: Python
owner: ethyca
file_changes: filename: requirements.txt
change_type: ModificationType.MODIFY
diff: @@ -8,6 +8,7 @@ colorama>=0.4.3
 cryptography==38.0.3
 dask==2022.9.2
 deepdiff==6.3.0
+defusedxml==0.7.1
 expandvars==0.9.0
 fastapi[all]==0.89.1
 fastapi-caching[redis]==0.3.0

programming_language: Batchfile
filename: connector_registry_service.py
change_type: ModificationType.MODIFY
diff: @@ -40,7 +40,7 @@ from fides.api.util.saas_util import (
     replace_dataset_placeholders,
     replace_version,
 )
-from fides.api.util.unsafe_file_util import verify_zip
+from fides.api.util.unsafe_file_util import verify_svg, verify_zip
 from fides.config import CONFIG
 
 
@@ -214,6 +214,7 @@ class CustomConnectorTemplateLoader(ConnectorTemplateLoader):
                     )
             elif info.filename.endswith(".svg"):
                 if not icon_contents:
+                    verify_svg(file_contents)
                     icon_contents = str_to_b64_str(file_contents)
                 else:
                     raise ValidationError(

programming_language: Python
filename: unsafe_file_util.py
change_type: ModificationType.MODIFY
diff: @@ -1,10 +1,34 @@
 from typing import Optional
 from zipfile import ZipFile
 
+from defusedxml.ElementTree import fromstring
+
+from fides.api.common_exceptions import ValidationError
+
 MAX_FILE_SIZE = 16 * 1024 * 1024  # 16 MB
 CHUNK_SIZE = 1024
 
 
+def verify_svg(contents: str) -> None:
+    """
+    Verifies the provided SVG content.
+
+    This function checks the given SVG content string for potential issues and throws an exception if any are found.
+    It first attempts to parse the SVG content using 'defusedxml.fromstring'. If the parsing is unsuccessful, this
+    will raise an exception, indicating that the SVG content may contain unsafe XML.
+
+    :param contents: The SVG content as a string.
+    :raises ValidationError: If the SVG content contains unsafe XML or 'use xlink'
+    """
+    try:
+        fromstring(contents)
+    except Exception:
+        raise ValidationError("SVG file contains unsafe XML.")
+
+    if "use xlink" in contents:
+        raise ValidationError("SVG files with xlink references are not allowed.")
+
+
 def verify_zip(zip_file: ZipFile, max_file_size: Optional[int] = None) -> None:
     """
     Function to safely verify the contents of zipped files. It prevents potential

programming_language: Python
filename: test_unsafe_file_util.py
change_type: ModificationType.MODIFY
diff: @@ -3,10 +3,57 @@ from zipfile import ZipFile
 
 import pytest
 
-from fides.api.util.unsafe_file_util import verify_zip
+from fides.api.common_exceptions import ValidationError
+from fides.api.util.unsafe_file_util import verify_svg, verify_zip
 from tests.ops.test_helpers.saas_test_utils import create_zip_file
 
 
+class TestVerifySvg:
+    def test_verify_svg(self):
+        verify_svg(
+            """<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100">
+                <circle cx="50" cy="50" r="40"/>
+            </svg>
+            """
+        )
+
+    def test_verify_svg_no_laughing_allowed(self):
+        """Test "billion laughs attack" is prevented"""
+        with pytest.raises(ValidationError) as exc:
+            verify_svg(
+                """<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+                <!DOCTYPE svg [
+                <!ENTITY lol "lol">
+                <!ELEMENT lolz (#PCDATA)>
+                <!ENTITY lol1 "&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;&lol;">
+                <!ENTITY lol2 "&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;&lol1;">
+                <!ENTITY lol3 "&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;&lol2;">
+                <!ENTITY lol4 "&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;&lol3;">
+                <!ENTITY lol5 "&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;&lol4;">
+                <!ENTITY lol6 "&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;&lol5;">
+                <!ENTITY lol7 "&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;&lol6;">
+                <!ENTITY lol8 "&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;&lol7;">
+                <!ENTITY lol9 "&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;&lol8;">
+                ]>
+                <svg>
+                    <lolz>&lol9;</lolz>
+                </svg>
+                """
+            )
+        assert "SVG file contains unsafe XML." in str(exc.value)
+
+    def test_verify_svg_with_xlink(self):
+        with pytest.raises(ValidationError) as exc:
+            verify_svg(
+                """<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 100 100">
+                    <circle id="circle" cx="50" cy="50" r="40"/>
+                    <use xlink:href="#circle"/>
+                </svg>
+                """
+            )
+        assert "SVG files with xlink references are not allowed." in str(exc.value)
+
+
 class TestVerifyZip:
     @pytest.fixture
     def zip_file(self) -> BytesIO:

programming_language: Python