Add freezegun to runtime dependencies, generate cachable s3 urls (#2264)

* Add freezegun to application dependencies
* Generate cachable S3 URLs by rounding time down to the previous hour to generate a consistent URL

CTFd/utils/uploads/uploaders.py

@@ -1,6 +1,8 @@
+import datetime
 import os
 import posixpath
 import string
+import time
 from pathlib import PurePath
 from shutil import copyfileobj, rmtree
 
@@ -8,6 +10,7 @@ import boto3
 from botocore.client import Config
 from flask import current_app, redirect, send_file
 from flask.helpers import safe_join
+from freezegun import freeze_time
 from werkzeug.utils import secure_filename
 
 from CTFd.utils import get_app_config
@@ -119,18 +122,25 @@ class S3Uploader(BaseUploader):
         return dst
 
     def download(self, filename):
+        # S3 URLs by default are valid for one hour.
+        # We round the timestamp down to the previous hour and generate the link at that time
+        current_timestamp = int(time.time())
+        truncated_timestamp = current_timestamp - (current_timestamp % 3600)
         key = filename
         filename = filename.split("/").pop()
-        url = self.s3.generate_presigned_url(
-            "get_object",
-            Params={
-                "Bucket": self.bucket,
-                "Key": key,
-                "ResponseContentDisposition": "attachment; filename={}".format(
-                    filename
-                ),
-            },
-        )
+        with freeze_time(datetime.datetime.fromtimestamp(truncated_timestamp)):
+            url = self.s3.generate_presigned_url(
+                "get_object",
+                Params={
+                    "Bucket": self.bucket,
+                    "Key": key,
+                    "ResponseContentDisposition": "attachment; filename={}".format(
+                        filename
+                    ),
+                    "ResponseCacheControl": "max-age=3600",
+                },
+                ExpiresIn=3600,
+            )
         return redirect(url)
 
     def delete(self, filename):

development.txt

@@ -4,7 +4,6 @@ pytest==5.4.2
 pytest-randomly==3.4.0
 coverage==5.1
 flake8==3.8.2
-freezegun==0.3.15
 psycopg2-binary==2.8.6
 codecov==2.1.7
 moto==1.3.16

requirements.in

@@ -29,3 +29,4 @@ python-geoacumen-city==2023.1.15
 maxminddb==1.5.4
 tenacity==6.2.0
 pybluemonday==0.0.9
+freezegun==1.2.2

requirements.txt

@@ -59,6 +59,8 @@ flask-sqlalchemy==2.4.3
     # via
     #   -r requirements.in
     #   flask-migrate
+freezegun==1.2.2
+    # via -r requirements.in
 gevent==22.10.2
     # via -r requirements.in
 greenlet==2.0.1
@@ -115,6 +117,7 @@ python-dateutil==2.8.1
     # via
     #   alembic
     #   botocore
+    #   freezegun
 python-dotenv==0.13.0
     # via -r requirements.in
 python-editor==1.0.4