view hgext/lfs/blobstore.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

# blobstore.py - local and remote (speaking Git-LFS protocol) blob storages
#
# Copyright 2017 Facebook, Inc.
#
# 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 hashlib
import json
import os
import re
import socket

from mercurial.i18n import _

from mercurial import (
    error,
    pathutil,
    pycompat,
    url as urlmod,
    util,
    vfs as vfsmod,
    worker,
)

from ..largefiles import lfutil

# 64 bytes for SHA256
_lfsre = re.compile(br'\A[a-f0-9]{64}\Z')

class lfsvfs(vfsmod.vfs):
    def join(self, path):
        """split the path at first two characters, like: XX/XXXXX..."""
        if not _lfsre.match(path):
            raise error.ProgrammingError('unexpected lfs path: %s' % path)
        return super(lfsvfs, self).join(path[0:2], path[2:])

    def walk(self, path=None, onerror=None):
        """Yield (dirpath, [], oids) tuple for blobs under path

        Oids only exist in the root of this vfs, so dirpath is always ''.
        """
        root = os.path.normpath(self.base)
        # when dirpath == root, dirpath[prefixlen:] becomes empty
        # because len(dirpath) < prefixlen.
        prefixlen = len(pathutil.normasprefix(root))
        oids = []

        for dirpath, dirs, files in os.walk(self.reljoin(self.base, path or ''),
                                            onerror=onerror):
            dirpath = dirpath[prefixlen:]

            # Silently skip unexpected files and directories
            if len(dirpath) == 2:
                oids.extend([dirpath + f for f in files
                             if _lfsre.match(dirpath + f)])

        yield ('', [], oids)

class filewithprogress(object):
    """a file-like object that supports __len__ and read.

    Useful to provide progress information for how many bytes are read.
    """

    def __init__(self, fp, callback):
        self._fp = fp
        self._callback = callback # func(readsize)
        fp.seek(0, os.SEEK_END)
        self._len = fp.tell()
        fp.seek(0)

    def __len__(self):
        return self._len

    def read(self, size):
        if self._fp is None:
            return b''
        data = self._fp.read(size)
        if data:
            if self._callback:
                self._callback(len(data))
        else:
            self._fp.close()
            self._fp = None
        return data

class local(object):
    """Local blobstore for large file contents.

    This blobstore is used both as a cache and as a staging area for large blobs
    to be uploaded to the remote blobstore.
    """

    def __init__(self, repo):
        fullpath = repo.svfs.join('lfs/objects')
        self.vfs = lfsvfs(fullpath)
        usercache = lfutil._usercachedir(repo.ui, 'lfs')
        self.cachevfs = lfsvfs(usercache)
        self.ui = repo.ui

    def open(self, oid):
        """Open a read-only file descriptor to the named blob, in either the
        usercache or the local store."""
        # The usercache is the most likely place to hold the file.  Commit will
        # write to both it and the local store, as will anything that downloads
        # the blobs.  However, things like clone without an update won't
        # populate the local store.  For an init + push of a local clone,
        # the usercache is the only place it _could_ be.  If not present, the
        # missing file msg here will indicate the local repo, not the usercache.
        if self.cachevfs.exists(oid):
            return self.cachevfs(oid, 'rb')

        return self.vfs(oid, 'rb')

    def download(self, oid, src):
        """Read the blob from the remote source in chunks, verify the content,
        and write to this local blobstore."""
        sha256 = hashlib.sha256()

        with self.vfs(oid, 'wb', atomictemp=True) as fp:
            for chunk in util.filechunkiter(src, size=1048576):
                fp.write(chunk)
                sha256.update(chunk)

            realoid = sha256.hexdigest()
            if realoid != oid:
                raise error.Abort(_('corrupt remote lfs object: %s') % oid)

        # XXX: should we verify the content of the cache, and hardlink back to
        # the local store on success, but truncate, write and link on failure?
        if not self.cachevfs.exists(oid):
            self.ui.note(_('lfs: adding %s to the usercache\n') % oid)
            lfutil.link(self.vfs.join(oid), self.cachevfs.join(oid))

    def write(self, oid, data):
        """Write blob to local blobstore.

        This should only be called from the filelog during a commit or similar.
        As such, there is no need to verify the data.  Imports from a remote
        store must use ``download()`` instead."""
        with self.vfs(oid, 'wb', atomictemp=True) as fp:
            fp.write(data)

        # XXX: should we verify the content of the cache, and hardlink back to
        # the local store on success, but truncate, write and link on failure?
        if not self.cachevfs.exists(oid):
            self.ui.note(_('lfs: adding %s to the usercache\n') % oid)
            lfutil.link(self.vfs.join(oid), self.cachevfs.join(oid))

    def read(self, oid, verify=True):
        """Read blob from local blobstore."""
        if not self.vfs.exists(oid):
            blob = self._read(self.cachevfs, oid, verify)

            # Even if revlog will verify the content, it needs to be verified
            # now before making the hardlink to avoid propagating corrupt blobs.
            # Don't abort if corruption is detected, because `hg verify` will
            # give more useful info about the corruption- simply don't add the
            # hardlink.
            if verify or hashlib.sha256(blob).hexdigest() == oid:
                self.ui.note(_('lfs: found %s in the usercache\n') % oid)
                lfutil.link(self.cachevfs.join(oid), self.vfs.join(oid))
        else:
            self.ui.note(_('lfs: found %s in the local lfs store\n') % oid)
            blob = self._read(self.vfs, oid, verify)
        return blob

    def _read(self, vfs, oid, verify):
        """Read blob (after verifying) from the given store"""
        blob = vfs.read(oid)
        if verify:
            _verify(oid, blob)
        return blob

    def has(self, oid):
        """Returns True if the local blobstore contains the requested blob,
        False otherwise."""
        return self.cachevfs.exists(oid) or self.vfs.exists(oid)

class _gitlfsremote(object):

    def __init__(self, repo, url):
        ui = repo.ui
        self.ui = ui
        baseurl, authinfo = url.authinfo()
        self.baseurl = baseurl.rstrip('/')
        useragent = repo.ui.config('experimental', 'lfs.user-agent')
        if not useragent:
            useragent = 'git-lfs/2.3.4 (Mercurial %s)' % util.version()
        self.urlopener = urlmod.opener(ui, authinfo, useragent)
        self.retry = ui.configint('lfs', 'retry')

    def writebatch(self, pointers, fromstore):
        """Batch upload from local to remote blobstore."""
        self._batch(_deduplicate(pointers), fromstore, 'upload')

    def readbatch(self, pointers, tostore):
        """Batch download from remote to local blostore."""
        self._batch(_deduplicate(pointers), tostore, 'download')

    def _batchrequest(self, pointers, action):
        """Get metadata about objects pointed by pointers for given action

        Return decoded JSON object like {'objects': [{'oid': '', 'size': 1}]}
        See https://github.com/git-lfs/git-lfs/blob/master/docs/api/batch.md
        """
        objects = [{'oid': p.oid(), 'size': p.size()} for p in pointers]
        requestdata = json.dumps({
            'objects': objects,
            'operation': action,
        })
        batchreq = util.urlreq.request('%s/objects/batch' % self.baseurl,
                                       data=requestdata)
        batchreq.add_header('Accept', 'application/vnd.git-lfs+json')
        batchreq.add_header('Content-Type', 'application/vnd.git-lfs+json')
        try:
            rsp = self.urlopener.open(batchreq)
            rawjson = rsp.read()
        except util.urlerr.httperror as ex:
            raise LfsRemoteError(_('LFS HTTP error: %s (action=%s)')
                                 % (ex, action))
        try:
            response = json.loads(rawjson)
        except ValueError:
            raise LfsRemoteError(_('LFS server returns invalid JSON: %s')
                                 % rawjson)

        if self.ui.debugflag:
            self.ui.debug('Status: %d\n' % rsp.status)
            # lfs-test-server and hg serve return headers in different order
            self.ui.debug('%s\n'
                          % '\n'.join(sorted(str(rsp.info()).splitlines())))

            if 'objects' in response:
                response['objects'] = sorted(response['objects'],
                                             key=lambda p: p['oid'])
            self.ui.debug('%s\n'
                          % json.dumps(response, indent=2, sort_keys=True))

        return response

    def _checkforservererror(self, pointers, responses, action):
        """Scans errors from objects

        Raises LfsRemoteError if any objects have an error"""
        for response in responses:
            # The server should return 404 when objects cannot be found. Some
            # server implementation (ex. lfs-test-server)  does not set "error"
            # but just removes "download" from "actions". Treat that case
            # as the same as 404 error.
            notfound = (response.get('error', {}).get('code') == 404
                        or (action == 'download'
                            and action not in response.get('actions', [])))
            if notfound:
                ptrmap = {p.oid(): p for p in pointers}
                p = ptrmap.get(response['oid'], None)
                if p:
                    filename = getattr(p, 'filename', 'unknown')
                    raise LfsRemoteError(
                        _(('LFS server error. Remote object '
                          'for "%s" not found: %r')) % (filename, response))
                else:
                    raise LfsRemoteError(
                        _('LFS server error. Unsolicited response for oid %s')
                        % response['oid'])
            if 'error' in response:
                raise LfsRemoteError(_('LFS server error: %r') % response)

    def _extractobjects(self, response, pointers, action):
        """extract objects from response of the batch API

        response: parsed JSON object returned by batch API
        return response['objects'] filtered by action
        raise if any object has an error
        """
        # Scan errors from objects - fail early
        objects = response.get('objects', [])
        self._checkforservererror(pointers, objects, action)

        # Filter objects with given action. Practically, this skips uploading
        # objects which exist in the server.
        filteredobjects = [o for o in objects if action in o.get('actions', [])]

        return filteredobjects

    def _basictransfer(self, obj, action, localstore):
        """Download or upload a single object using basic transfer protocol

        obj: dict, an object description returned by batch API
        action: string, one of ['upload', 'download']
        localstore: blobstore.local

        See https://github.com/git-lfs/git-lfs/blob/master/docs/api/\
        basic-transfers.md
        """
        oid = pycompat.bytestr(obj['oid'])

        href = pycompat.bytestr(obj['actions'][action].get('href'))
        headers = obj['actions'][action].get('header', {}).items()

        request = util.urlreq.request(href)
        if action == 'upload':
            # If uploading blobs, read data from local blobstore.
            with localstore.open(oid) as fp:
                _verifyfile(oid, fp)
            request.data = filewithprogress(localstore.open(oid), None)
            request.get_method = lambda: 'PUT'

        for k, v in headers:
            request.add_header(k, v)

        response = b''
        try:
            req = self.urlopener.open(request)

            if self.ui.debugflag:
                self.ui.debug('Status: %d\n' % req.status)
                # lfs-test-server and hg serve return headers in different order
                self.ui.debug('%s\n'
                              % '\n'.join(sorted(str(req.info()).splitlines())))

            if action == 'download':
                # If downloading blobs, store downloaded data to local blobstore
                localstore.download(oid, req)
            else:
                while True:
                    data = req.read(1048576)
                    if not data:
                        break
                    response += data
                if response:
                    self.ui.debug('lfs %s response: %s' % (action, response))
        except util.urlerr.httperror as ex:
            if self.ui.debugflag:
                self.ui.debug('%s: %s\n' % (oid, ex.read()))
            raise LfsRemoteError(_('HTTP error: %s (oid=%s, action=%s)')
                                 % (ex, oid, action))

    def _batch(self, pointers, localstore, action):
        if action not in ['upload', 'download']:
            raise error.ProgrammingError('invalid Git-LFS action: %s' % action)

        response = self._batchrequest(pointers, action)
        objects = self._extractobjects(response, pointers, action)
        total = sum(x.get('size', 0) for x in objects)
        sizes = {}
        for obj in objects:
            sizes[obj.get('oid')] = obj.get('size', 0)
        topic = {'upload': _('lfs uploading'),
                 'download': _('lfs downloading')}[action]
        if len(objects) > 1:
            self.ui.note(_('lfs: need to transfer %d objects (%s)\n')
                         % (len(objects), util.bytecount(total)))
        self.ui.progress(topic, 0, total=total)
        def transfer(chunk):
            for obj in chunk:
                objsize = obj.get('size', 0)
                if self.ui.verbose:
                    if action == 'download':
                        msg = _('lfs: downloading %s (%s)\n')
                    elif action == 'upload':
                        msg = _('lfs: uploading %s (%s)\n')
                    self.ui.note(msg % (obj.get('oid'),
                                 util.bytecount(objsize)))
                retry = self.retry
                while True:
                    try:
                        self._basictransfer(obj, action, localstore)
                        yield 1, obj.get('oid')
                        break
                    except socket.error as ex:
                        if retry > 0:
                            self.ui.note(
                                _('lfs: failed: %r (remaining retry %d)\n')
                                % (ex, retry))
                            retry -= 1
                            continue
                        raise

        # Until https multiplexing gets sorted out
        if self.ui.configbool('experimental', 'lfs.worker-enable'):
            oids = worker.worker(self.ui, 0.1, transfer, (),
                                 sorted(objects, key=lambda o: o.get('oid')))
        else:
            oids = transfer(sorted(objects, key=lambda o: o.get('oid')))

        processed = 0
        blobs = 0
        for _one, oid in oids:
            processed += sizes[oid]
            blobs += 1
            self.ui.progress(topic, processed, total=total)
            self.ui.note(_('lfs: processed: %s\n') % oid)
        self.ui.progress(topic, pos=None, total=total)

        if blobs > 0:
            if action == 'upload':
                self.ui.status(_('lfs: uploaded %d files (%s)\n')
                               % (blobs, util.bytecount(processed)))
            # TODO: coalesce the download requests, and comment this in
            #elif action == 'download':
            #    self.ui.status(_('lfs: downloaded %d files (%s)\n')
            #                   % (blobs, util.bytecount(processed)))

    def __del__(self):
        # copied from mercurial/httppeer.py
        urlopener = getattr(self, 'urlopener', None)
        if urlopener:
            for h in urlopener.handlers:
                h.close()
                getattr(h, "close_all", lambda : None)()

class _dummyremote(object):
    """Dummy store storing blobs to temp directory."""

    def __init__(self, repo, url):
        fullpath = repo.vfs.join('lfs', url.path)
        self.vfs = lfsvfs(fullpath)

    def writebatch(self, pointers, fromstore):
        for p in _deduplicate(pointers):
            content = fromstore.read(p.oid(), verify=True)
            with self.vfs(p.oid(), 'wb', atomictemp=True) as fp:
                fp.write(content)

    def readbatch(self, pointers, tostore):
        for p in _deduplicate(pointers):
            with self.vfs(p.oid(), 'rb') as fp:
                tostore.download(p.oid(), fp)

class _nullremote(object):
    """Null store storing blobs to /dev/null."""

    def __init__(self, repo, url):
        pass

    def writebatch(self, pointers, fromstore):
        pass

    def readbatch(self, pointers, tostore):
        pass

class _promptremote(object):
    """Prompt user to set lfs.url when accessed."""

    def __init__(self, repo, url):
        pass

    def writebatch(self, pointers, fromstore, ui=None):
        self._prompt()

    def readbatch(self, pointers, tostore, ui=None):
        self._prompt()

    def _prompt(self):
        raise error.Abort(_('lfs.url needs to be configured'))

_storemap = {
    'https': _gitlfsremote,
    'http': _gitlfsremote,
    'file': _dummyremote,
    'null': _nullremote,
    None: _promptremote,
}

def _deduplicate(pointers):
    """Remove any duplicate oids that exist in the list"""
    reduced = util.sortdict()
    for p in pointers:
        reduced[p.oid()] = p
    return reduced.values()

def _verify(oid, content):
    realoid = hashlib.sha256(content).hexdigest()
    if realoid != oid:
        raise error.Abort(_('detected corrupt lfs object: %s') % oid,
                          hint=_('run hg verify'))

def _verifyfile(oid, fp):
    sha256 = hashlib.sha256()
    while True:
        data = fp.read(1024 * 1024)
        if not data:
            break
        sha256.update(data)
    realoid = sha256.hexdigest()
    if realoid != oid:
        raise error.Abort(_('detected corrupt lfs object: %s') % oid,
                          hint=_('run hg verify'))

def remote(repo):
    """remotestore factory. return a store in _storemap depending on config"""
    url = util.url(repo.ui.config('lfs', 'url') or '')
    scheme = url.scheme
    if scheme not in _storemap:
        raise error.Abort(_('lfs: unknown url scheme: %s') % scheme)
    return _storemap[scheme](repo, url)

class LfsRemoteError(error.RevlogError):
    pass