This change adds strong validation for the uuid variable for v2 routes. This is
a minor specification change but is okay since the uuid field is controlled by
the server. The character set is restricted to avoid path traversal, allowing
for alphanumeric values and urlsafe base64 encoding.
This change has no effect on client implementations.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
Manifests are now fetched by a field called "reference", which may be a tag or
a digest. When using digests to reference a manifest, the data is immutable.
The routes and specification have been updated to allow this.
There are a few caveats to this approach:
1. It may be problematic to rely on data format to differentiate between a tag
and a digest. Currently, they are disjoint but there may modifications on
either side that break this guarantee.
2. The caching characteristics of returned content are very different for
digest versus tag-based references. Digest urls can be cached forever while tag
urls cannot.
Both of these are minimal caveats that we can live with in the future.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
