mercurial/wireprotoserver.py

stream-clone: add a v3 version of the protocol

This new version is less rigid regarding the extract number of files and number
of bytes to be actually transfered, it also lays the groundwork for other
improvements.

The format stays experimental, but this is an interesting base to build upon.

# Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
# Copyright 2005-2007 Olivia 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.


import contextlib
import struct
import threading

from .i18n import _
from . import (
    encoding,
    error,
    pycompat,
    util,
    wireprototypes,
    wireprotov1server,
)
from .interfaces import util as interfaceutil
from .utils import (
    compression,
    stringutil,
)

stringio = util.stringio

urlerr = util.urlerr
urlreq = util.urlreq

HTTP_OK = 200

HGTYPE = b'application/mercurial-0.1'
HGTYPE2 = b'application/mercurial-0.2'
HGERRTYPE = b'application/hg-error'

SSHV1 = wireprototypes.SSHV1


def decodevaluefromheaders(req, headerprefix):
    """Decode a long value from multiple HTTP request headers.

    Returns the value as a bytes, not a str.
    """
    chunks = []
    i = 1
    while True:
        v = req.headers.get(b'%s-%d' % (headerprefix, i))
        if v is None:
            break
        chunks.append(pycompat.bytesurl(v))
        i += 1

    return b''.join(chunks)


@interfaceutil.implementer(wireprototypes.baseprotocolhandler)
class httpv1protocolhandler:
    def __init__(self, req, ui, checkperm):
        self._req = req
        self._ui = ui
        self._checkperm = checkperm
        self._protocaps = None

    @property
    def name(self):
        return b'http-v1'

    def getargs(self, args):
        knownargs = self._args()
        data = {}
        keys = args.split()
        for k in keys:
            if k == b'*':
                star = {}
                for key in knownargs.keys():
                    if key != b'cmd' and key not in keys:
                        star[key] = knownargs[key][0]
                data[b'*'] = star
            else:
                data[k] = knownargs[k][0]
        return [data[k] for k in keys]

    def _args(self):
        args = self._req.qsparams.asdictoflists()
        postlen = int(self._req.headers.get(b'X-HgArgs-Post', 0))
        if postlen:
            args.update(
                urlreq.parseqs(
                    self._req.bodyfh.read(postlen), keep_blank_values=True
                )
            )
            return args

        argvalue = decodevaluefromheaders(self._req, b'X-HgArg')
        args.update(urlreq.parseqs(argvalue, keep_blank_values=True))
        return args

    def getprotocaps(self):
        if self._protocaps is None:
            value = decodevaluefromheaders(self._req, b'X-HgProto')
            self._protocaps = set(value.split(b' '))
        return self._protocaps

    def getpayload(self):
        # Existing clients *always* send Content-Length.
        length = int(self._req.headers[b'Content-Length'])

        # If httppostargs is used, we need to read Content-Length
        # minus the amount that was consumed by args.
        length -= int(self._req.headers.get(b'X-HgArgs-Post', 0))
        return util.filechunkiter(self._req.bodyfh, limit=length)

    @contextlib.contextmanager
    def mayberedirectstdio(self):
        oldout = self._ui.fout
        olderr = self._ui.ferr

        out = util.stringio()

        try:
            self._ui.fout = out
            self._ui.ferr = out
            yield out
        finally:
            self._ui.fout = oldout
            self._ui.ferr = olderr

    def client(self):
        return b'remote:%s:%s:%s' % (
            self._req.urlscheme,
            urlreq.quote(self._req.remotehost or b''),
            urlreq.quote(self._req.remoteuser or b''),
        )

    def addcapabilities(self, repo, caps):
        caps.append(b'batch')

        caps.append(
            b'httpheader=%d' % repo.ui.configint(b'server', b'maxhttpheaderlen')
        )
        if repo.ui.configbool(b'experimental', b'httppostargs'):
            caps.append(b'httppostargs')

        # FUTURE advertise 0.2rx once support is implemented
        # FUTURE advertise minrx and mintx after consulting config option
        caps.append(b'httpmediatype=0.1rx,0.1tx,0.2tx')

        compengines = wireprototypes.supportedcompengines(
            repo.ui, compression.SERVERROLE
        )
        if compengines:
            comptypes = b','.join(
                urlreq.quote(e.wireprotosupport().name) for e in compengines
            )
            caps.append(b'compression=%s' % comptypes)

        return caps

    def checkperm(self, perm):
        return self._checkperm(perm)


# This method exists mostly so that extensions like remotefilelog can
# disable a kludgey legacy method only over http. As of early 2018,
# there are no other known users, so with any luck we can discard this
# hook if remotefilelog becomes a first-party extension.
def iscmd(cmd):
    return cmd in wireprotov1server.commands


def handlewsgirequest(rctx, req, res, checkperm):
    """Possibly process a wire protocol request.

    If the current request is a wire protocol request, the request is
    processed by this function.

    ``req`` is a ``parsedrequest`` instance.
    ``res`` is a ``wsgiresponse`` instance.

    Returns a bool indicating if the request was serviced. If set, the caller
    should stop processing the request, as a response has already been issued.
    """
    # Avoid cycle involving hg module.
    from .hgweb import common as hgwebcommon

    repo = rctx.repo

    # HTTP version 1 wire protocol requests are denoted by a "cmd" query
    # string parameter. If it isn't present, this isn't a wire protocol
    # request.
    if b'cmd' not in req.qsparams:
        return False

    cmd = req.qsparams[b'cmd']

    # The "cmd" request parameter is used by both the wire protocol and hgweb.
    # While not all wire protocol commands are available for all transports,
    # if we see a "cmd" value that resembles a known wire protocol command, we
    # route it to a protocol handler. This is better than routing possible
    # wire protocol requests to hgweb because it prevents hgweb from using
    # known wire protocol commands and it is less confusing for machine
    # clients.
    if not iscmd(cmd):
        return False

    # The "cmd" query string argument is only valid on the root path of the
    # repo. e.g. ``/?cmd=foo``, ``/repo?cmd=foo``. URL paths within the repo
    # like ``/blah?cmd=foo`` are not allowed. So don't recognize the request
    # in this case. We send an HTTP 404 for backwards compatibility reasons.
    if req.dispatchpath:
        res.status = hgwebcommon.statusmessage(404)
        res.headers[b'Content-Type'] = HGTYPE
        # TODO This is not a good response to issue for this request. This
        # is mostly for BC for now.
        res.setbodybytes(b'0\n%s\n' % b'Not Found')
        return True

    proto = httpv1protocolhandler(
        req, repo.ui, lambda perm: checkperm(rctx, req, perm)
    )

    # The permissions checker should be the only thing that can raise an
    # ErrorResponse. It is kind of a layer violation to catch an hgweb
    # exception here. So consider refactoring into a exception type that
    # is associated with the wire protocol.
    try:
        _callhttp(repo, req, res, proto, cmd)
    except hgwebcommon.ErrorResponse as e:
        for k, v in e.headers:
            res.headers[k] = v
        res.status = hgwebcommon.statusmessage(
            e.code, stringutil.forcebytestr(e)
        )
        # TODO This response body assumes the failed command was
        # "unbundle." That assumption is not always valid.
        res.setbodybytes(b'0\n%s\n' % stringutil.forcebytestr(e))

    return True


def _httpresponsetype(ui, proto, prefer_uncompressed):
    """Determine the appropriate response type and compression settings.

    Returns a tuple of (mediatype, compengine, engineopts).
    """
    # Determine the response media type and compression engine based
    # on the request parameters.

    if b'0.2' in proto.getprotocaps():
        # All clients are expected to support uncompressed data.
        if prefer_uncompressed:
            return HGTYPE2, compression._noopengine(), {}

        # Now find an agreed upon compression format.
        compformats = wireprotov1server.clientcompressionsupport(proto)
        for engine in wireprototypes.supportedcompengines(
            ui, compression.SERVERROLE
        ):
            if engine.wireprotosupport().name in compformats:
                opts = {}
                level = ui.configint(b'server', b'%slevel' % engine.name())
                if level is not None:
                    opts[b'level'] = level

                return HGTYPE2, engine, opts

        # No mutually supported compression format. Fall back to the
        # legacy protocol.

    # Don't allow untrusted settings because disabling compression or
    # setting a very high compression level could lead to flooding
    # the server's network or CPU.
    opts = {b'level': ui.configint(b'server', b'zliblevel')}
    return HGTYPE, util.compengines[b'zlib'], opts


def _callhttp(repo, req, res, proto, cmd):
    # Avoid cycle involving hg module.
    from .hgweb import common as hgwebcommon

    def genversion2(gen, engine, engineopts):
        # application/mercurial-0.2 always sends a payload header
        # identifying the compression engine.
        name = engine.wireprotosupport().name
        assert 0 < len(name) < 256
        yield struct.pack(b'B', len(name))
        yield name

        for chunk in gen:
            yield chunk

    def setresponse(code, contenttype, bodybytes=None, bodygen=None):
        if code == HTTP_OK:
            res.status = b'200 Script output follows'
        else:
            res.status = hgwebcommon.statusmessage(code)

        res.headers[b'Content-Type'] = contenttype

        if bodybytes is not None:
            res.setbodybytes(bodybytes)
        if bodygen is not None:
            res.setbodygen(bodygen)

    if not wireprotov1server.commands.commandavailable(cmd, proto):
        setresponse(
            HTTP_OK,
            HGERRTYPE,
            _(
                b'requested wire protocol command is not available over '
                b'HTTP'
            ),
        )
        return

    proto.checkperm(wireprotov1server.commands[cmd].permission)

    accesshidden = hgwebcommon.hashiddenaccess(repo, req)
    rsp = wireprotov1server.dispatch(repo, proto, cmd, accesshidden)

    if isinstance(rsp, bytes):
        setresponse(HTTP_OK, HGTYPE, bodybytes=rsp)
    elif isinstance(rsp, wireprototypes.bytesresponse):
        setresponse(HTTP_OK, HGTYPE, bodybytes=rsp.data)
    elif isinstance(rsp, wireprototypes.streamreslegacy):
        setresponse(HTTP_OK, HGTYPE, bodygen=rsp.gen)
    elif isinstance(rsp, wireprototypes.streamres):
        gen = rsp.gen

        # This code for compression should not be streamres specific. It
        # is here because we only compress streamres at the moment.
        mediatype, engine, engineopts = _httpresponsetype(
            repo.ui, proto, rsp.prefer_uncompressed
        )
        gen = engine.compressstream(gen, engineopts)

        if mediatype == HGTYPE2:
            gen = genversion2(gen, engine, engineopts)

        setresponse(HTTP_OK, mediatype, bodygen=gen)
    elif isinstance(rsp, wireprototypes.pushres):
        rsp = b'%d\n%s' % (rsp.res, rsp.output)
        setresponse(HTTP_OK, HGTYPE, bodybytes=rsp)
    elif isinstance(rsp, wireprototypes.pusherr):
        rsp = b'0\n%s\n' % rsp.res
        res.drain = True
        setresponse(HTTP_OK, HGTYPE, bodybytes=rsp)
    elif isinstance(rsp, wireprototypes.ooberror):
        setresponse(HTTP_OK, HGERRTYPE, bodybytes=rsp.message)
    else:
        raise error.ProgrammingError(b'hgweb.protocol internal failure', rsp)


def _sshv1respondbytes(fout, value):
    """Send a bytes response for protocol version 1."""
    fout.write(b'%d\n' % len(value))
    fout.write(value)
    fout.flush()


def _sshv1respondstream(fout, source):
    write = fout.write
    for chunk in source.gen:
        write(chunk)
    fout.flush()


def _sshv1respondooberror(fout, ferr, rsp):
    ferr.write(b'%s\n-\n' % rsp)
    ferr.flush()
    fout.write(b'\n')
    fout.flush()


@interfaceutil.implementer(wireprototypes.baseprotocolhandler)
class sshv1protocolhandler:
    """Handler for requests services via version 1 of SSH protocol."""

    def __init__(self, ui, fin, fout):
        self._ui = ui
        self._fin = fin
        self._fout = fout
        self._protocaps = set()

    @property
    def name(self):
        return wireprototypes.SSHV1

    def getargs(self, args):
        data = {}
        keys = args.split()
        for n in range(len(keys)):
            argline = self._fin.readline()[:-1]
            arg, l = argline.split()
            if arg not in keys:
                raise error.Abort(_(b"unexpected parameter %r") % arg)
            if arg == b'*':
                star = {}
                for k in range(int(l)):
                    argline = self._fin.readline()[:-1]
                    arg, l = argline.split()
                    val = self._fin.read(int(l))
                    star[arg] = val
                data[b'*'] = star
            else:
                val = self._fin.read(int(l))
                data[arg] = val
        return [data[k] for k in keys]

    def getprotocaps(self):
        return self._protocaps

    def getpayload(self):
        # We initially send an empty response. This tells the client it is
        # OK to start sending data. If a client sees any other response, it
        # interprets it as an error.
        _sshv1respondbytes(self._fout, b'')

        # The file is in the form:
        #
        # <chunk size>\n<chunk>
        # ...
        # 0\n
        count = int(self._fin.readline())
        while count:
            yield self._fin.read(count)
            count = int(self._fin.readline())

    @contextlib.contextmanager
    def mayberedirectstdio(self):
        yield None

    def client(self):
        client = encoding.environ.get(b'SSH_CLIENT', b'').split(b' ', 1)[0]
        return b'remote:ssh:' + client

    def addcapabilities(self, repo, caps):
        if self.name == wireprototypes.SSHV1:
            caps.append(b'protocaps')
        caps.append(b'batch')
        return caps

    def checkperm(self, perm):
        pass


def _runsshserver(ui, repo, fin, fout, ev, accesshidden=False):
    # This function operates like a state machine of sorts. The following
    # states are defined:
    #
    # protov1-serving
    #    Server is in protocol version 1 serving mode. Commands arrive on
    #    new lines. These commands are processed in this state, one command
    #    after the other.
    #
    # shutdown
    #    The server is shutting down, possibly in reaction to a client event.
    #
    # And here are their transitions:
    #
    # protov1-serving -> shutdown
    #    When server receives an empty request or encounters another
    #    error.

    state = b'protov1-serving'
    proto = sshv1protocolhandler(ui, fin, fout)

    while not ev.is_set():
        if state == b'protov1-serving':
            # Commands are issued on new lines.
            request = fin.readline()[:-1]

            # Empty lines signal to terminate the connection.
            if not request:
                state = b'shutdown'
                continue

            available = wireprotov1server.commands.commandavailable(
                request, proto
            )

            # This command isn't available. Send an empty response and go
            # back to waiting for a new command.
            if not available:
                _sshv1respondbytes(fout, b'')
                continue

            rsp = wireprotov1server.dispatch(
                repo, proto, request, accesshidden=accesshidden
            )
            repo.ui.fout.flush()
            repo.ui.ferr.flush()

            if isinstance(rsp, bytes):
                _sshv1respondbytes(fout, rsp)
            elif isinstance(rsp, wireprototypes.bytesresponse):
                _sshv1respondbytes(fout, rsp.data)
            elif isinstance(rsp, wireprototypes.streamres):
                _sshv1respondstream(fout, rsp)
            elif isinstance(rsp, wireprototypes.streamreslegacy):
                _sshv1respondstream(fout, rsp)
            elif isinstance(rsp, wireprototypes.pushres):
                _sshv1respondbytes(fout, b'')
                _sshv1respondbytes(fout, b'%d' % rsp.res)
            elif isinstance(rsp, wireprototypes.pusherr):
                _sshv1respondbytes(fout, rsp.res)
            elif isinstance(rsp, wireprototypes.ooberror):
                _sshv1respondooberror(fout, ui.ferr, rsp.message)
            else:
                raise error.ProgrammingError(
                    b'unhandled response type from '
                    b'wire protocol command: %s' % rsp
                )

        elif state == b'shutdown':
            break

        else:
            raise error.ProgrammingError(
                b'unhandled ssh server state: %s' % state
            )


class sshserver:
    def __init__(self, ui, repo, logfh=None, accesshidden=False):
        self._ui = ui
        self._repo = repo
        self._fin, self._fout = ui.protectfinout()
        self._accesshidden = accesshidden

        # Log write I/O to stdout and stderr if configured.
        if logfh:
            self._fout = util.makeloggingfileobject(
                logfh, self._fout, b'o', logdata=True
            )
            ui.ferr = util.makeloggingfileobject(
                logfh, ui.ferr, b'e', logdata=True
            )

    def serve_forever(self):
        self.serveuntil(threading.Event())
        self._ui.restorefinout(self._fin, self._fout)

    def serveuntil(self, ev):
        """Serve until a threading.Event is set."""
        _runsshserver(
            self._ui, self._repo, self._fin, self._fout, ev, self._accesshidden
        )