Error entries appear in the log when we request ActiveStorage
controllers (`ActiveStorage::Representations::ProxyController#show`,
`ActiveStorage::Blobs::ProxyController#show`).
These entries look like: "Couldn't find template for digesting:
active_storage/representations/proxy/show".
These controllers use the method
`ActionController::ConditionalGet#http_cache_forever`,
and therefore `ActionController::ConditionalGet#combine_etags` method,
and therefore `ActionController::EtagWithTemplateDigest` module via
`etaggers` array.
`ActionController::EtagWithTemplateDigest` module requires a template
(view).
We have no views in ActiveStorage, so `EtagWithTemplateDigest` is
now turned off in ActiveStorage controllers by
`etag_with_template_digest` class attribute.
Services can be configured in `config/storage.yml` with a new key
`public: true | false` to indicate whether a service holds public
blobs or private blobs. Public services will always return a
permanent URL.
Deprecates `Blob#service_url` in favor of `Blob#url`.
* 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.
Fix an issue in ActiveStorage where a direct upload to disk storage
would fail due to a content type mismatch if the file was uploaded using
a mime-type synonym.
`ActiveStorage::DiskController#show` generates a 404 Not Found response when
the requested file is missing from the disk service. It previously raised
`Errno::ENOENT`.
Trying to pass the current request down to the service so that it can
create full urls instead of paths makes the API messy so use a model
based on ActiveSupport::CurrentAttributes to provide the current host
to services that need it (primarily the disk service).
Since ActiveStorage::Blob::Representable unifies the idea of previews and
variants under one roof as representation, we may as well have the
controllers follow suit.
Thus ActiveStorage::RepresenationsController enters the fray. I've copied
the old tests for both previews and variants and unified those as well.
Disable CSRF protection for ActiveStorage::DiskController#update. The local disk service is intended to imitate a third-party service like S3 or GCS, so we don't care where direct uploads originate: they’re authorized by signed tokens.
Closes#30290.
[Shinichi Maeshima & George Claghorn]
Tahsin Hasan