wireproto: check permissions when executing "batch" command (BC) (SEC) For as long as the "batch" command has existed (introduced by bd88561afb4b and first released as part of Mercurial 1.9), that command (like most wire commands introduced after 2008) lacked an entry in the hgweb permissions table. And since we don't verify permissions if an entry is missing from the permissions table, this meant that executing a command via "batch" would bypass all permissions checks. The security implications are significant: a Mercurial HTTP server would allow writes via "batch" wire protocol commands as long as the HTTP request were processed by Mercurial and the process running the Mercurial HTTP server had write access to the repository. The Mercurial defaults of servers being read-only and the various web.* config options to define access control were bypassed. In addition, "batch" could be used to exfiltrate data from servers that were configured to not allow read access. Both forms of permissions bypass could be mitigated to some extent by using HTTP authentication. This would prevent HTTP requests from hitting Mercurial's server logic. However, any authenticated request would still be able to bypass permissions checks via "batch" commands. The easiest exploit was to send "pushkey" commands via "batch" and modify the state of bookmarks, phases, and obsolescence markers. However, I suspect a well-crafted HTTP request could trick the server into running the "unbundle" wire protocol command, effectively performing a full `hg push` to create new changesets on the remote. This commit plugs this gaping security hole by having the "batch" command perform permissions checking on each sub-command that is being batched. We do this by threading a permissions checking callable all the way to the protocol handler. The threading is a bit hacky from a code perspective. But it preserves API compatibility, which is the proper thing to do on the stable branch. One of the subtle things we do is assume that a command with an undefined permission is a "push" command. This is the safest thing to do from a security perspective: we don't want to take chances that a command could perform a write even though the server is configured to not allow writes. As the test changes demonstrate, it is no longer possible to bypass permissions via the "batch" wire protocol command. .. bc:: The "batch" wire protocol command now enforces permissions of each invoked sub-command. Wire protocol commands must define their operation type or the "batch" command will assume they can write data and will prevent their execution on HTTP servers unless the HTTP request method is POST, the server is configured to allow pushes, and the (possibly authenticated) HTTP user is authorized to perform a push.