annotate mercurial/statichttprepo.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

# statichttprepo.py - simple http repository class for mercurial
#
# This provides read-only repo access to repositories exported via static http
#
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import errno

from .i18n import _
from . import (
    changelog,
    error,
    localrepo,
    manifest,
    namespaces,
    pathutil,
    scmutil,
    store,
    url,
    util,
    vfs as vfsmod,
)

urlerr = util.urlerr
urlreq = util.urlreq

class httprangereader(object):
    def __init__(self, url, opener):
        # we assume opener has HTTPRangeHandler
        self.url = url
        self.pos = 0
        self.opener = opener
        self.name = url

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, traceback):
        self.close()

    def seek(self, pos):
        self.pos = pos
    def read(self, bytes=None):
        req = urlreq.request(self.url)
        end = ''
        if bytes:
            end = self.pos + bytes - 1
        if self.pos or end:
            req.add_header('Range', 'bytes=%d-%s' % (self.pos, end))

        try:
            f = self.opener.open(req)
            data = f.read()
            code = f.code
        except urlerr.httperror as inst:
            num = inst.code == 404 and errno.ENOENT or None
            raise IOError(num, inst)
        except urlerr.urlerror as inst:
            raise IOError(None, inst.reason[1])

        if code == 200:
            # HTTPRangeHandler does nothing if remote does not support
            # Range headers and returns the full entity. Let's slice it.
            if bytes:
                data = data[self.pos:self.pos + bytes]
            else:
                data = data[self.pos:]
        elif bytes:
            data = data[:bytes]
        self.pos += len(data)
        return data
    def readlines(self):
        return self.read().splitlines(True)
    def __iter__(self):
        return iter(self.readlines())
    def close(self):
        pass

# _RangeError and _HTTPRangeHandler were originally in byterange.py,
# which was itself extracted from urlgrabber. See the last version of
# byterange.py from history if you need more information.
class _RangeError(IOError):
    """Error raised when an unsatisfiable range is requested."""

class _HTTPRangeHandler(urlreq.basehandler):
    """Handler that enables HTTP Range headers.

    This was extremely simple. The Range header is a HTTP feature to
    begin with so all this class does is tell urllib2 that the
    "206 Partial Content" response from the HTTP server is what we
    expected.
    """

    def http_error_206(self, req, fp, code, msg, hdrs):
        # 206 Partial Content Response
        r = urlreq.addinfourl(fp, hdrs, req.get_full_url())
        r.code = code
        r.msg = msg
        return r

    def http_error_416(self, req, fp, code, msg, hdrs):
        # HTTP's Range Not Satisfiable error
        raise _RangeError('Requested Range Not Satisfiable')

def build_opener(ui, authinfo):
    # urllib cannot handle URLs with embedded user or passwd
    urlopener = url.opener(ui, authinfo)
    urlopener.add_handler(_HTTPRangeHandler())

    class statichttpvfs(vfsmod.abstractvfs):
        def __init__(self, base):
            self.base = base

        def __call__(self, path, mode='r', *args, **kw):
            if mode not in ('r', 'rb'):
                raise IOError('Permission denied')
            f = "/".join((self.base, urlreq.quote(path)))
            return httprangereader(f, urlopener)

        def join(self, path):
            if path:
                return pathutil.join(self.base, path)
            else:
                return self.base

    return statichttpvfs

class statichttppeer(localrepo.localpeer):
    def local(self):
        return None
    def canpush(self):
        return False

class statichttprepository(localrepo.localrepository):
    supported = localrepo.localrepository._basesupported

    def __init__(self, ui, path):
        self._url = path
        self.ui = ui

        self.root = path
        u = util.url(path.rstrip('/') + "/.hg")
        self.path, authinfo = u.authinfo()

        vfsclass = build_opener(ui, authinfo)
        self.vfs = vfsclass(self.path)
        self.cachevfs = vfsclass(self.vfs.join('cache'))
        self._phasedefaults = []

        self.names = namespaces.namespaces()
        self.filtername = None

        try:
            requirements = scmutil.readrequires(self.vfs, self.supported)
        except IOError as inst:
            if inst.errno != errno.ENOENT:
                raise
            requirements = set()

            # check if it is a non-empty old-style repository
            try:
                fp = self.vfs("00changelog.i")
                fp.read(1)
                fp.close()
            except IOError as inst:
                if inst.errno != errno.ENOENT:
                    raise
                # we do not care about empty old-style repositories here
                msg = _("'%s' does not appear to be an hg repository") % path
                raise error.RepoError(msg)

        # setup store
        self.store = store.store(requirements, self.path, vfsclass)
        self.spath = self.store.path
        self.svfs = self.store.opener
        self.sjoin = self.store.join
        self._filecache = {}
        self.requirements = requirements

        self.manifestlog = manifest.manifestlog(self.svfs, self)
        self.changelog = changelog.changelog(self.svfs)
        self._tags = None
        self.nodetagscache = None
        self._branchcaches = {}
        self._revbranchcache = None
        self.encodepats = None
        self.decodepats = None
        self._transref = None

    def _restrictcapabilities(self, caps):
        caps = super(statichttprepository, self)._restrictcapabilities(caps)
        return caps.difference(["pushkey"])

    def url(self):
        return self._url

    def local(self):
        return False

    def peer(self):
        return statichttppeer(self)

    def wlock(self, wait=True):
        raise error.LockUnavailable(0, _('lock not available'), 'lock',
                                    _('cannot lock static-http repository'))

    def lock(self, wait=True):
        raise error.Abort(_('cannot lock static-http repository'))

    def _writecaches(self):
        pass # statichttprepository are read only

def instance(ui, path, create):
    if create:
        raise error.Abort(_('cannot create new static-http repository'))
    return statichttprepository(ui, path[7:])