* p2phttp: Allow unauthenticated users to lock content by default.
* p2phttp: Added --unauth-nolocking option to prevent unauthenticated
users from locking content.
The rationalle for this is that locking is not really a write operation, so
makes sense to allow in a repository that only allows read-only access. Not
supporting locking in that situation will prevent the user from dropping
content from a special remote they control in cases where the other copy of
the content is on the p2phttp server.
Also, when p2phttp is configured to also allow authenticated access,
lockcontent was resulting in a password prompt for users who had no way to
authenticate. And there is no good way to distinguish between the two types
of users client side.
--unauth-nolocking anticipates that this might be abused, and seems better
than disabling unauthenticated access entirely if a server is being
attacked. It may be that rate limiting locking by IP address or similar
would be an effective measure in such a situation. Or just limiting the
number of locks by anonymous users that can be live at any one time. Since
the impact of such an DOS attempt is limited to preventing dropping content
from the server, it seems not a very appealing target anyway.
p2phttp: Support serving unauthenticated users while requesting
authentication for operations that need it. Eg, --unauth-readonly can be
combined with --authenv.
Drop locking currently needs authentication so it will prompt for that.
That still needs to be addressed somehow.
