Limit the size of manifests/signatures sync/upload

Adds new settings to limit the size of manifests and signatures as a safeguard
to avoid DDoS attack during sync and upload operations.
To also prevent this during image upload, this commit configures a
`client_max_body_size` for manifests and signatures Nginx endpoints.
Modify the blob upload to read the layers in chunks.

closes: pulp#532

Author: git-hyagi

CHANGES/532.feature

@@ -0,0 +1,6 @@
+Added support to the `MANIFEST_PAYLOAD_MAX_SIZE` and `SIGNATURE_PAYLOAD_MAX_SIZE` settings to define
+limits (for the size of Manifests and Signatures) to protect against OOM DoS attacks during synchronization tasks
+and image uploads.
+Additionally, the Nginx snippet has been updated to enforce the limit for these endpoints.
+Modified the internal logic of Blob uploads to read the receiving layers in chunks,
+thereby reducing the memory footprint of the process.

docs/admin/guides/limit-manifest-and-signature-sizes.md

@@ -0,0 +1,17 @@
+# Limit the size of Manifests and Signatures
+
+It is possible to configure Pulp to block the synchronization and upload of image Manifests and/or
+Signatures if they exceed a defined size. A use case for this feature is to avoid OOM DoS attacks
+when synchronizing remote repositories with malicious or compromised containter images.
+To implement this, use the following settings:
+```
+MANIFEST_MAX_PAYLOAD_SIZE=<bytes>
+SIGNATURE_MAX_PAYLOAD_SIZE=<bytes>
+```
+
+!!! info
+    By default, there is no definition for these settings, meaning that no limit will be enforced.
+
+
+!!! note
+    A common value adopted by other registries is to set these values to 4MB (4000000).

pulp_container/app/downloaders.py

@@ -1,26 +1,87 @@
 import aiohttp
 import asyncio
+import fnmatch
 import json
 import re
 
 from aiohttp.client_exceptions import ClientResponseError
 from collections import namedtuple
+from django.conf import settings
 from logging import getLogger
 from urllib import parse
 
+
 from pulpcore.plugin.download import DownloaderFactory, HttpDownloader
 
-from pulp_container.constants import V2_ACCEPT_HEADERS
+from pulp_container.constants import (
+    MANIFEST_MEDIA_TYPES,
+    MEGABYTE,
+    V2_ACCEPT_HEADERS,
+)
+from pulp_container.app.exceptions import InvalidRequest
+from pulp_container.app.utils import resource_body_size_exceeded_msg
 
 log = getLogger(__name__)
 
 HeadResult = namedtuple(
     "HeadResult",
     ["status_code", "path", "artifact_attributes", "url", "headers"],
 )
+DownloadResult = namedtuple("DownloadResult", ["url", "artifact_attributes", "path", "headers"])
+
 
+class ValidateResourceSizeMixin:
+    async def _handle_response(self, response, content_type=None, max_body_size=None):
+        """
+        Overrides the HttpDownloader method to be able to limit the request body size.
+        Handle the aiohttp response by writing it to disk and calculating digests
+        Args:
+            response (aiohttp.ClientResponse): The response to handle.
+            content_type (string): Type of the resource (manifest or signature) whose size
+                                   will be verified
+            max_body_size (int): Maximum allowed body size of the resource (manifest or signature).
+        Returns:
+             DownloadResult: Contains information about the result. See the DownloadResult docs for
+                 more information.
+        """
+        if self.headers_ready_callback:
+            await self.headers_ready_callback(response.headers)
+        total_size = 0
+        while True:
+            chunk = await response.content.read(MEGABYTE)
+            total_size += len(chunk)
+            if max_body_size and total_size > max_body_size:
+                await self.finalize()
+                raise InvalidRequest(resource_body_size_exceeded_msg(content_type, max_body_size))
+            if not chunk:
+                await self.finalize()
+                break  # the download is done
+            await self.handle_data(chunk)
+        return DownloadResult(
+            path=self.path,
+            artifact_attributes=self.artifact_attributes,
+            url=self.url,
+            headers=response.headers,
+        )
 
-class RegistryAuthHttpDownloader(HttpDownloader):
+    def get_content_type_and_max_resource_size(self, response):
+        """
+        Returns the content_type (manifest or signature) based on the HTTP request and also the
+        corresponding resource allowed maximum size.
+        """
+        max_resource_size = None
+        content_type = response.content_type
+        is_cosign_tag = fnmatch.fnmatch(response.url.name, "sha256-*.sig")
+        if isinstance(self, NoAuthSignatureDownloader) or is_cosign_tag:
+            max_resource_size = settings.get("SIGNATURE_PAYLOAD_MAX_SIZE", None)
+            content_type = "Signature"
+        elif content_type in MANIFEST_MEDIA_TYPES.IMAGE + MANIFEST_MEDIA_TYPES.LIST:
+            max_resource_size = settings.get("MANIFEST_PAYLOAD_MAX_SIZE", None)
+            content_type = "Manifest"
+        return content_type, max_resource_size
+
+
+class RegistryAuthHttpDownloader(ValidateResourceSizeMixin, HttpDownloader):
     """
     Custom Downloader that automatically handles Token Based and Basic Authentication.
 
@@ -104,7 +165,10 @@ async def _run(self, handle_401=True, extra_data=None):
             if http_method == "head":
                 to_return = await self._handle_head_response(response)
             else:
-                to_return = await self._handle_response(response)
+                content_type, max_resource_size = self.get_content_type_and_max_resource_size(
+                    response
+                )
+                to_return = await self._handle_response(response, content_type, max_resource_size)
 
             await response.release()
             self.response_headers = response.headers
@@ -193,7 +257,7 @@ async def _handle_head_response(self, response):
         )
 
 
-class NoAuthSignatureDownloader(HttpDownloader):
+class NoAuthSignatureDownloader(ValidateResourceSizeMixin, HttpDownloader):
     """A downloader class suited for signature downloads."""
 
     def raise_for_status(self, response):
@@ -208,6 +272,20 @@ def raise_for_status(self, response):
         else:
             response.raise_for_status()
 
+    async def _run(self, extra_data=None):
+        if self.download_throttler:
+            await self.download_throttler.acquire()
+        async with self.session.get(
+            self.url, proxy=self.proxy, proxy_auth=self.proxy_auth, auth=self.auth
+        ) as response:
+            self.raise_for_status(response)
+            content_type, max_resource_size = self.get_content_type_and_max_resource_size(response)
+            to_return = await self._handle_response(response, content_type, max_resource_size)
+            await response.release()
+        if self._close_session_on_finalize:
+            await self.session.close()
+        return to_return
+
 
 class NoAuthDownloaderFactory(DownloaderFactory):
     """

pulp_container/app/registry_api.py

@@ -87,18 +87,20 @@
     filter_resource,
     has_task_completed,
     validate_manifest,
+    resource_body_size_exceeded_msg,
 )
 from pulp_container.constants import (
     EMPTY_BLOB,
     SIGNATURE_API_EXTENSION_VERSION,
     SIGNATURE_HEADER,
-    SIGNATURE_PAYLOAD_MAX_SIZE,
     SIGNATURE_TYPE,
     V2_ACCEPT_HEADERS,
+    MEGABYTE,
 )
 
 log = logging.getLogger(__name__)
 
+
 IGNORED_PULL_THROUGH_REMOTE_ATTRIBUTES = [
     "remote_ptr",
     "pulp_type",
@@ -790,7 +792,9 @@ def create_single_chunk_artifact(self, chunk):
         with transaction.atomic():
             # 1 chunk, create artifact right away
             with NamedTemporaryFile("ab") as temp_file:
-                temp_file.write(chunk.read())
+                while chunk and chunk.reader.length > 0:
+                    current_chunk = chunk.reader.read(MEGABYTE)
+                    temp_file.write(current_chunk)
                 temp_file.flush()
 
                 uploaded_file = PulpTemporaryUploadedFile.from_file(
@@ -1379,8 +1383,16 @@ def receive_artifact(self, chunk):
                 subchunk = chunk.read(2000000)
                 if not subchunk:
                     break
-                temp_file.write(subchunk)
                 size += len(subchunk)
+                manifest_payload_max_size = settings.get("MANIFEST_PAYLOAD_MAX_SIZE", None)
+                if manifest_payload_max_size and size > manifest_payload_max_size:
+                    temp_file.flush()
+                    raise InvalidRequest(
+                        message=resource_body_size_exceeded_msg(
+                            "Manifest", manifest_payload_max_size
+                        )
+                    )
+                temp_file.write(subchunk)
                 for algorithm in Artifact.DIGEST_FIELDS:
                     hashers[algorithm].update(subchunk)
             temp_file.flush()
@@ -1451,7 +1463,8 @@ def put(self, request, path, pk):
         except models.Manifest.DoesNotExist:
             raise ManifestNotFound(reference=pk)
 
-        signature_payload = request.META["wsgi.input"].read(SIGNATURE_PAYLOAD_MAX_SIZE)
+        signature_max_size = settings.get("SIGNATURE_PAYLOAD_MAX_SIZE", None)
+        signature_payload = request.META["wsgi.input"].read(signature_max_size)
         try:
             signature_dict = json.loads(signature_payload)
         except json.decoder.JSONDecodeError:

pulp_container/app/tasks/sync_stages.py

@@ -27,6 +27,7 @@
     ManifestSignature,
     Tag,
 )
+from pulp_container.app.exceptions import InvalidRequest
 from pulp_container.app.utils import (
     extract_data_from_signature,
     urlpath_sanitize,
@@ -62,7 +63,14 @@ def __init__(self, remote, signed_only):
 
     async def _download_manifest_data(self, manifest_url):
         downloader = self.remote.get_downloader(url=manifest_url)
-        response = await downloader.run(extra_data={"headers": V2_ACCEPT_HEADERS})
+        try:
+            response = await downloader.run(extra_data={"headers": V2_ACCEPT_HEADERS})
+        except InvalidRequest as e:
+            # if it failed to download the manifest, log the error and
+            # there is nothing to return
+            log.warning(e.args[0])
+            return None, None, None
+
         with open(response.path, "rb") as content_file:
             raw_bytes_data = content_file.read()
         response.artifact_attributes["file"] = response.path
@@ -146,6 +154,11 @@ async def run(self):
             for artifact in asyncio.as_completed(to_download_artifact):
                 content_data, raw_text_data, response = await artifact
 
+                # skip the current object if it failed to be downloaded
+                if not content_data:
+                    await pb_parsed_tags.aincrement()
+                    continue
+
                 digest = calculate_digest(raw_text_data)
                 tag_name = response.url.split("/")[-1]
 
@@ -542,6 +555,12 @@ async def create_signatures(self, man_dc, signature_source):
                         "{} is not accessible, can't sync an image signature. "
                         "Error: {} {}".format(signature_url, exc.status, exc.message)
                     )
+                except InvalidRequest as e:
+                    log.warning(
+                        "Failed to sync signature {}. Error: {}".format(signature_url, e.args[0])
+                    )
+                    signature_counter += 1
+                    continue
 
                 with open(signature_download_result.path, "rb") as f:
                     signature_raw = f.read()

pulp_container/app/utils.py

@@ -342,3 +342,10 @@ def filter_resources(element_list, include_patterns, exclude_patterns):
     if exclude_patterns:
         element_list = filter(partial(exclude, patterns=exclude_patterns), element_list)
     return list(element_list)
+
+
+def resource_body_size_exceeded_msg(content_type, max_resource_size):
+    return (
+        f"{content_type} body size exceeded the maximum allowed size of "
+        f"{max_resource_size} bytes."
+    )

pulp_container/app/webserver_snippets/nginx.conf

@@ -38,3 +38,25 @@ location /token/ {
     proxy_redirect off;
     proxy_pass http://pulp-api;
 }
+
+location ~* /v2/.*/manifests/.*$ {
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_set_header Host $http_host;
+    # we don't want nginx trying to do something clever with
+    # redirects, we set the Host: header above already.
+    proxy_redirect off;
+    proxy_pass http://pulp-api;
+    client_max_body_size 4m;
+}
+
+location ~* /extensions/v2/.*/signatures/.*$ {
+    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+    proxy_set_header X-Forwarded-Proto $scheme;
+    proxy_set_header Host $http_host;
+    # we don't want nginx trying to do something clever with
+    # redirects, we set the Host: header above already.
+    proxy_redirect off;
+    proxy_pass http://pulp-api;
+    client_max_body_size 4m;
+}

pulp_container/constants.py

@@ -68,6 +68,5 @@
 SIGNATURE_HEADER = "X-Registry-Supports-Signatures"
 
 MEGABYTE = 1_000_000
-SIGNATURE_PAYLOAD_MAX_SIZE = 4 * MEGABYTE
 
 SIGNATURE_API_EXTENSION_VERSION = 2