From 06ab7b27ea1c1ab357085439abacdb464f6742bf Mon Sep 17 00:00:00 2001 From: Rosa Gutierrez Date: Thu, 6 Sep 2018 16:52:52 +0200 Subject: Prevent content type and disposition bypass in storage service URLs * Force content-type to binary on service urls for relevant content types We have a list of content types that must be forcibly served as binary, but in practice this only means to serve them as attachment always. We should also set the Content-Type to the configured binary type. As a bonus: add text/cache-manifest to the list of content types to be served as binary by default. * Store content-disposition and content-type in GCS Forcing these in the service_url when serving the file works fine for S3 and Azure, since these services include params in the signature. However, GCS specifically excludes response-content-disposition and response-content-type from the signature, which means an attacker can modify these and have files that should be served as text/plain attachments served as inline HTML for example. This makes our attempt to force specific files to be served as binary and as attachment can be easily bypassed. The only way this can be forced in GCS is by storing content-disposition and content-type in the object metadata. * Update GCS object metadata after identifying blob In some cases we create the blob and upload the data before identifying the content-type, which means we can't store that in GCS right when uploading. In these, after creating the attachment, we enqueue a job to identify the blob, and set the content-type. In other cases, files are uploaded to the storage service via direct upload link. We create the blob before the direct upload, which happens independently from the blob creation itself. We then mark the blob as identified, but we have already the content-type we need without having put it in the service. In these two cases, then, we need to update the metadata in the GCS service. * Include content-type and disposition in the verified key for disk service This prevents an attacker from modifying these params in the service signed URL, which is particularly important when we want to force them to have specific values for security reasons. * Allow only a list of specific content types to be served inline This is different from the content types that must be served as binary in the sense that any content type not in this list will be always served as attachment but with its original content type. Only types in this list are allowed to be served either inline or as attachment. Apart from forcing this in the service URL, for GCS we need to store the disposition in the metadata. Fix CVE-2018-16477. --- activestorage/test/controllers/disk_controller_test.rb | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) (limited to 'activestorage/test/controllers') diff --git a/activestorage/test/controllers/disk_controller_test.rb b/activestorage/test/controllers/disk_controller_test.rb index 7b5e989699..0aa8648db3 100644 --- a/activestorage/test/controllers/disk_controller_test.rb +++ b/activestorage/test/controllers/disk_controller_test.rb @@ -5,11 +5,12 @@ require "database/setup" class ActiveStorage::DiskControllerTest < ActionDispatch::IntegrationTest test "showing blob inline" do - blob = create_blob + blob = create_blob(filename: "hello.jpg", content_type: "image/jpg") + get blob.service_url assert_response :ok - assert_equal "inline; filename=\"hello.txt\"; filename*=UTF-8''hello.txt", response.headers["Content-Disposition"] - assert_equal "text/plain", response.headers["Content-Type"] + assert_equal "inline; filename=\"hello.jpg\"; filename*=UTF-8''hello.jpg", response.headers["Content-Disposition"] + assert_equal "image/jpg", response.headers["Content-Type"] assert_equal "Hello world!", response.body end @@ -36,6 +37,10 @@ class ActiveStorage::DiskControllerTest < ActionDispatch::IntegrationTest blob.delete get blob.service_url + end + + test "showing blob with invalid key" do + get rails_disk_service_url(encoded_key: "Invalid key", filename: "hello.txt") assert_response :not_found end -- cgit v1.2.3