Comment 14 for bug 1996188

You know, I really thought we did assert the source type of the image when we fetch it. But looking through all of that, at least as it exists today, I see that we're not. Since the previous requirement for doing that was to protect against the qcow2 backing_file attack, the comments referencing fetch_to_raw() as some sort of safety measure must be referencing the backing_file check itself.

Unless we're aware of other attacks that can be made by claiming an image is one thing when probing disagrees, we're probably okay for the scope of this bug. My code checks the vmdk rules if we probe it as such, so we won't leak there, even if someone claims it is something else.

I can imagine glance having an enforcement mode that requires images to detect as what they claim to be (it has the infrastructure to make such an enforcement today). Nova could also have a flag that verifies the image's disk_format agrees with the probe in fetch_to_raw().