diff mercurial/wireprotoserver.py @ 37047:fddcb51b5084

wireproto: define permissions-based routing of HTTPv2 wire protocol

Now that we have a scaffolding for serving version 2 of the HTTP
protocol, let's start implementing it.

A good place to start is URL routing and basic request processing
semantics. We can focus on content types, capabilities detect, etc
later.

Version 2 of the HTTP wire protocol encodes the needed permissions
of the request in the URL path. The reasons for this are documented
in the added documentation. In short, a) it makes it really easy and
fail proof for server administrators to implement path-based
authentication and b) it will enable clients to realize very early in
a server exchange that authentication will be required to complete
the operation. This latter point avoids all kinds of complexity and
problems, like dealing with Expect: 100-continue and clients finding
out later during `hg push` that they need to provide authentication.
This will avoid the current badness where clients send a full bundle,
get an HTTP 403, provide authentication, then retransmit the bundle.

In order to implement command checking, we needed to implement a
protocol handler for the new wire protocol. Our handler is just
small enough to run the code we've implemented.

Tests for the defined functionality have been added.

I very much want to refactor the permissions checking code and define
a better response format. But this can be done later. Nothing is
covered by backwards compatibility at this point.

Differential Revision: https://phab.mercurial-scm.org/D2836

--- a/mercurial/wireprotoserver.py	Tue Mar 13 16:53:21 2018 -0700
+++ b/mercurial/wireprotoserver.py	Mon Mar 19 16:43:47 2018 -0700
@@ -272,6 +272,64 @@
                                    req.dispatchparts[2:])
 
 def _handlehttpv2request(rctx, req, res, checkperm, urlparts):
+    from .hgweb import common as hgwebcommon
+
+    # URL space looks like: <permissions>/<command>, where <permission> can
+    # be ``ro`` or ``rw`` to signal read-only or read-write, respectively.
+
+    # Root URL does nothing meaningful... yet.
+    if not urlparts:
+        res.status = b'200 OK'
+        res.headers[b'Content-Type'] = b'text/plain'
+        res.setbodybytes(_('HTTP version 2 API handler'))
+        return
+
+    if len(urlparts) == 1:
+        res.status = b'404 Not Found'
+        res.headers[b'Content-Type'] = b'text/plain'
+        res.setbodybytes(_('do not know how to process %s\n') %
+                         req.dispatchpath)
+        return
+
+    permission, command = urlparts[0:2]
+
+    if permission not in (b'ro', b'rw'):
+        res.status = b'404 Not Found'
+        res.headers[b'Content-Type'] = b'text/plain'
+        res.setbodybytes(_('unknown permission: %s') % permission)
+        return
+
+    # At some point we'll want to use our own API instead of recycling the
+    # behavior of version 1 of the wire protocol...
+    # TODO return reasonable responses - not responses that overload the
+    # HTTP status line message for error reporting.
+    try:
+        checkperm(rctx, req, 'pull' if permission == b'ro' else 'push')
+    except hgwebcommon.ErrorResponse as e:
+        res.status = hgwebcommon.statusmessage(e.code, pycompat.bytestr(e))
+        for k, v in e.headers:
+            res.headers[k] = v
+        res.setbodybytes('permission denied')
+        return
+
+    if command not in wireproto.commands:
+        res.status = b'404 Not Found'
+        res.headers[b'Content-Type'] = b'text/plain'
+        res.setbodybytes(_('unknown wire protocol command: %s\n') % command)
+        return
+
+    repo = rctx.repo
+    ui = repo.ui
+
+    proto = httpv2protocolhandler(req, ui)
+
+    if not wireproto.commands.commandavailable(command, proto):
+        res.status = b'404 Not Found'
+        res.headers[b'Content-Type'] = b'text/plain'
+        res.setbodybytes(_('invalid wire protocol command: %s') % command)
+        return
+
+    # We don't do anything meaningful yet.
     res.status = b'200 OK'
     res.headers[b'Content-Type'] = b'text/plain'
     res.setbodybytes(b'/'.join(urlparts) + b'\n')
@@ -284,6 +342,34 @@
     },
 }
 
+class httpv2protocolhandler(wireprototypes.baseprotocolhandler):
+    def __init__(self, req, ui):
+        self._req = req
+        self._ui = ui
+
+    @property
+    def name(self):
+        return HTTPV2
+
+    def getargs(self, args):
+        raise NotImplementedError
+
+    def forwardpayload(self, fp):
+        raise NotImplementedError
+
+    @contextlib.contextmanager
+    def mayberedirectstdio(self):
+        raise NotImplementedError
+
+    def client(self):
+        raise NotImplementedError
+
+    def addcapabilities(self, repo, caps):
+        raise NotImplementedError
+
+    def checkperm(self, perm):
+        raise NotImplementedError
+
 def _httpresponsetype(ui, req, prefer_uncompressed):
     """Determine the appropriate response type and compression settings.