view hgext/lfs/blobstore.py @ 35480:417e8e040102

lfs: verify lfs object content when transferring to and from the remote store

This avoids inserting corrupt files into the usercache, and local and remote
stores.  One down side is that the bad file won't be available locally for
forensic purposes after a remote download.  I'm thinking about adding an
'incoming' directory to the local lfs store to handle the download, and then
move it to the 'objects' directory after it passes verification.  That would
have the additional benefit of not concatenating each transfer chunk in memory
until the full file is transferred.

Verification isn't needed when the data is passed back through the revlog
interface or when the oid was just calculated, but otherwise it is on by
default.  The additional overhead should be well worth avoiding problems with
file based remote stores, or buggy lfs servers.

Having two different verify functions is a little sad, but the full data of the
blob is mostly passed around in memory, because that's what the revlog interface
wants.  The upload function, however, chunks up the data.  It would be ideal if
that was how the content is always handled, but that's probably a huge project.

I don't really like printing the long hash, but `hg debugdata` isn't a public
interface, and is the only way to get it.  The filelog and revision info is
nowhere near this area, so recommending `hg verify` is the easiest thing to do.

# 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,
    url as urlmod,
    util,
    vfs as vfsmod,
    worker,
)

from ..largefiles import lfutil

# 64 bytes for SHA256
_lfsre = re.compile(r'\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 write(self, oid, data, verify=True):
        """Write blob to local blobstore."""
        if verify:
            _verify(oid, data)

        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)
            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 = 'mercurial/%s git/2.15.1' % 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(pointers, fromstore, 'upload')

    def readbatch(self, pointers, tostore):
        """Batch download from remote to local blostore."""
        self._batch(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:
            rawjson = self.urlopener.open(batchreq).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)
        return response

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

        Returns LfsRemoteError if any objects has an error"""
        for response in responses:
            error = response.get('error')
            if error:
                ptrmap = {p.oid(): p for p in pointers}
                p = ptrmap.get(response['oid'], None)
                if error['code'] == 404 and p:
                    filename = getattr(p, 'filename', 'unknown')
                    raise LfsRemoteError(
                        _(('LFS server error. Remote object '
                          'for file %s not found: %r')) % (filename, 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)

        # 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', [])]
        # But for downloading, we want all objects. Therefore missing objects
        # should be considered an error.
        if action == 'download':
            if len(filteredobjects) < len(objects):
                missing = [o.get('oid', '?')
                           for o in objects
                           if action not in o.get('actions', [])]
                raise LfsRemoteError(
                    _('LFS server claims required objects do not exist:\n%s')
                    % '\n'.join(missing))

        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 = str(obj['oid'])

        href = str(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.vfs(oid) as fp:
                _verifyfile(oid, fp)
            request.data = filewithprogress(localstore.vfs(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)
            while True:
                data = req.read(1048576)
                if not data:
                    break
                response += data
        except util.urlerr.httperror as ex:
            raise LfsRemoteError(_('HTTP error: %s (oid=%s, action=%s)')
                                 % (ex, oid, action))

        if action == 'download':
            # If downloading blobs, store downloaded data to local blobstore
            localstore.write(oid, response, verify=True)

    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 self.ui.verbose and len(objects) > 1:
            self.ui.write(_('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.write(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:
                            if self.ui.verbose:
                                self.ui.write(
                                    _('lfs: failed: %r (remaining retry %d)\n')
                                    % (ex, retry))
                            retry -= 1
                            continue
                        raise

        oids = worker.worker(self.ui, 0.1, transfer, (),
                             sorted(objects, key=lambda o: o.get('oid')))
        processed = 0
        for _one, oid in oids:
            processed += sizes[oid]
            self.ui.progress(topic, processed, total=total)
            if self.ui.verbose:
                self.ui.write(_('lfs: processed: %s\n') % oid)
        self.ui.progress(topic, pos=None, total=total)

    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 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 pointers:
            content = self.vfs.read(p.oid())
            tostore.write(p.oid(), content, verify=True)

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 _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"""
    defaulturl = ''

    # convert deprecated configs to the new url. TODO: remove this if other
    # places are migrated to the new url config.
    # deprecated config: lfs.remotestore
    deprecatedstore = repo.ui.config('lfs', 'remotestore')
    if deprecatedstore == 'dummy':
        # deprecated config: lfs.remotepath
        defaulturl = 'file://' + repo.ui.config('lfs', 'remotepath')
    elif deprecatedstore == 'git-lfs':
        # deprecated config: lfs.remoteurl
        defaulturl = repo.ui.config('lfs', 'remoteurl')
    elif deprecatedstore == 'null':
        defaulturl = 'null://'

    url = util.url(repo.ui.config('lfs', 'url', defaulturl))
    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