annotate mercurial/wireprotoserver.py @ 36102:5767664d39a5

wireprotoserver: extract SSH response handling functions

The lookup/dispatch table was cute. But it isn't needed. Future
refactors will benefit from the handlers for individual response
types living outside the class.

As part of this, I snuck in a change that changes a type compare
from str to bytes. This has no effect on Python 2. But it might
make Python 3 a bit happier.

Differential Revision: https://phab.mercurial-scm.org/D2091

# Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
# 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 abc
import cgi
import struct
import sys

from .i18n import _
from . import (
    encoding,
    error,
    hook,
    pycompat,
    util,
    wireproto,
)

stringio = util.stringio

urlerr = util.urlerr
urlreq = util.urlreq

HTTP_OK = 200

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

# Names of the SSH protocol implementations.
SSHV1 = 'ssh-v1'
# This is advertised over the wire. Incremental the counter at the end
# to reflect BC breakages.
SSHV2 = 'exp-ssh-v2-0001'

class baseprotocolhandler(object):
    """Abstract base class for wire protocol handlers.

    A wire protocol handler serves as an interface between protocol command
    handlers and the wire protocol transport layer. Protocol handlers provide
    methods to read command arguments, redirect stdio for the duration of
    the request, handle response types, etc.
    """

    __metaclass__ = abc.ABCMeta

    @abc.abstractproperty
    def name(self):
        """The name of the protocol implementation.

        Used for uniquely identifying the transport type.
        """

    @abc.abstractmethod
    def getargs(self, args):
        """return the value for arguments in <args>

        returns a list of values (same order as <args>)"""

    @abc.abstractmethod
    def getfile(self, fp):
        """write the whole content of a file into a file like object

        The file is in the form::

            (<chunk-size>\n<chunk>)+0\n

        chunk size is the ascii version of the int.
        """

    @abc.abstractmethod
    def redirect(self):
        """may setup interception for stdout and stderr

        See also the `restore` method."""

    # If the `redirect` function does install interception, the `restore`
    # function MUST be defined. If interception is not used, this function
    # MUST NOT be defined.
    #
    # left commented here on purpose
    #
    #def restore(self):
    #    """reinstall previous stdout and stderr and return intercepted stdout
    #    """
    #    raise NotImplementedError()

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
    prefix = headerprefix.upper().replace(r'-', r'_')
    while True:
        v = req.env.get(r'HTTP_%s_%d' % (prefix, i))
        if v is None:
            break
        chunks.append(pycompat.bytesurl(v))
        i += 1

    return ''.join(chunks)

class webproto(baseprotocolhandler):
    def __init__(self, req, ui):
        self._req = req
        self._ui = ui

    @property
    def name(self):
        return 'http'

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

    def _args(self):
        args = util.rapply(pycompat.bytesurl, self._req.form.copy())
        postlen = int(self._req.env.get(r'HTTP_X_HGARGS_POST', 0))
        if postlen:
            args.update(cgi.parse_qs(
                self._req.read(postlen), keep_blank_values=True))
            return args

        argvalue = decodevaluefromheaders(self._req, r'X-HgArg')
        args.update(cgi.parse_qs(argvalue, keep_blank_values=True))
        return args

    def getfile(self, fp):
        length = int(self._req.env[r'CONTENT_LENGTH'])
        # If httppostargs is used, we need to read Content-Length
        # minus the amount that was consumed by args.
        length -= int(self._req.env.get(r'HTTP_X_HGARGS_POST', 0))
        for s in util.filechunkiter(self._req, limit=length):
            fp.write(s)

    def redirect(self):
        self._oldio = self._ui.fout, self._ui.ferr
        self._ui.ferr = self._ui.fout = stringio()

    def restore(self):
        val = self._ui.fout.getvalue()
        self._ui.ferr, self._ui.fout = self._oldio
        return val

    def _client(self):
        return 'remote:%s:%s:%s' % (
            self._req.env.get('wsgi.url_scheme') or 'http',
            urlreq.quote(self._req.env.get('REMOTE_HOST', '')),
            urlreq.quote(self._req.env.get('REMOTE_USER', '')))

    def responsetype(self, 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.
        protocaps = decodevaluefromheaders(self._req, r'X-HgProto').split(' ')

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

            # Default as defined by wire protocol spec.
            compformats = ['zlib', 'none']
            for cap in protocaps:
                if cap.startswith('comp='):
                    compformats = cap[5:].split(',')
                    break

            # Now find an agreed upon compression format.
            for engine in wireproto.supportedcompengines(self._ui, self,
                                                         util.SERVERROLE):
                if engine.wireprotosupport().name in compformats:
                    opts = {}
                    level = self._ui.configint('server',
                                              '%slevel' % engine.name())
                    if level is not None:
                        opts['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 = {'level': self._ui.configint('server', 'zliblevel')}
        return HGTYPE, util.compengines['zlib'], opts

def iscmd(cmd):
    return cmd in wireproto.commands

def parsehttprequest(repo, req, query):
    """Parse the HTTP request for a wire protocol request.

    If the current request appears to be a wire protocol request, this
    function returns a dict with details about that request, including
    an ``abstractprotocolserver`` instance suitable for handling the
    request. Otherwise, ``None`` is returned.

    ``req`` is a ``wsgirequest`` instance.
    """
    # 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 r'cmd' not in req.form:
        return None

    cmd = pycompat.sysbytes(req.form[r'cmd'][0])

    # 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 cmd not in wireproto.commands:
        return None

    proto = webproto(req, repo.ui)

    return {
        'cmd': cmd,
        'proto': proto,
        'dispatch': lambda: _callhttp(repo, req, proto, cmd),
        'handleerror': lambda ex: _handlehttperror(ex, req, cmd),
    }

def _callhttp(repo, req, proto, cmd):
    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', len(name))
        yield name

        for chunk in gen:
            yield chunk

    rsp = wireproto.dispatch(repo, proto, cmd)

    if not wireproto.commands.commandavailable(cmd, proto):
        req.respond(HTTP_OK, HGERRTYPE,
                    body=_('requested wire protocol command is not available '
                           'over HTTP'))
        return []

    if isinstance(rsp, bytes):
        req.respond(HTTP_OK, HGTYPE, body=rsp)
        return []
    elif isinstance(rsp, wireproto.streamres_legacy):
        gen = rsp.gen
        req.respond(HTTP_OK, HGTYPE)
        return gen
    elif isinstance(rsp, wireproto.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 = proto.responsetype(
            rsp.prefer_uncompressed)
        gen = engine.compressstream(gen, engineopts)

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

        req.respond(HTTP_OK, mediatype)
        return gen
    elif isinstance(rsp, wireproto.pushres):
        val = proto.restore()
        rsp = '%d\n%s' % (rsp.res, val)
        req.respond(HTTP_OK, HGTYPE, body=rsp)
        return []
    elif isinstance(rsp, wireproto.pusherr):
        # This is the httplib workaround documented in _handlehttperror().
        req.drain()

        proto.restore()
        rsp = '0\n%s\n' % rsp.res
        req.respond(HTTP_OK, HGTYPE, body=rsp)
        return []
    elif isinstance(rsp, wireproto.ooberror):
        rsp = rsp.message
        req.respond(HTTP_OK, HGERRTYPE, body=rsp)
        return []
    raise error.ProgrammingError('hgweb.protocol internal failure', rsp)

def _handlehttperror(e, req, cmd):
    """Called when an ErrorResponse is raised during HTTP request processing."""

    # Clients using Python's httplib are stateful: the HTTP client
    # won't process an HTTP response until all request data is
    # sent to the server. The intent of this code is to ensure
    # we always read HTTP request data from the client, thus
    # ensuring httplib transitions to a state that allows it to read
    # the HTTP response. In other words, it helps prevent deadlocks
    # on clients using httplib.

    if (req.env[r'REQUEST_METHOD'] == r'POST' and
        # But not if Expect: 100-continue is being used.
        (req.env.get('HTTP_EXPECT',
                     '').lower() != '100-continue') or
        # Or the non-httplib HTTP library is being advertised by
        # the client.
        req.env.get('X-HgHttp2', '')):
        req.drain()
    else:
        req.headers.append((r'Connection', r'Close'))

    # TODO This response body assumes the failed command was
    # "unbundle." That assumption is not always valid.
    req.respond(e, HGTYPE, body='0\n%s\n' % e)

    return ''

def _sshv1respondbytes(fout, value):
    """Send a bytes response for protocol version 1."""
    fout.write('%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()

class sshserver(baseprotocolhandler):
    def __init__(self, ui, repo):
        self._ui = ui
        self._repo = repo
        self._fin = ui.fin
        self._fout = ui.fout

        hook.redirect(True)
        ui.fout = repo.ui.fout = ui.ferr

        # Prevent insertion/deletion of CRs
        util.setbinary(self._fin)
        util.setbinary(self._fout)

    @property
    def name(self):
        return 'ssh'

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

    def getfile(self, fpout):
        _sshv1respondbytes(self._fout, b'')
        count = int(self._fin.readline())
        while count:
            fpout.write(self._fin.read(count))
            count = int(self._fin.readline())

    def redirect(self):
        pass

    def serve_forever(self):
        while self.serve_one():
            pass
        sys.exit(0)

    def serve_one(self):
        cmd = self._fin.readline()[:-1]
        if cmd and wireproto.commands.commandavailable(cmd, self):
            rsp = wireproto.dispatch(self._repo, self, cmd)

            if isinstance(rsp, bytes):
                _sshv1respondbytes(self._fout, rsp)
            elif isinstance(rsp, wireproto.streamres):
                _sshv1respondstream(self._fout, rsp)
            elif isinstance(rsp, wireproto.streamres_legacy):
                _sshv1respondstream(self._fout, rsp)
            elif isinstance(rsp, wireproto.pushres):
                _sshv1respondbytes(self._fout, b'')
                _sshv1respondbytes(self._fout, bytes(rsp.res))
            elif isinstance(rsp, wireproto.pusherr):
                _sshv1respondbytes(self._fout, rsp.res)
            elif isinstance(rsp, wireproto.ooberror):
                _sshv1respondooberror(self._fout, self._ui.ferr, rsp.message)
            else:
                raise error.ProgrammingError('unhandled response type from '
                                             'wire protocol command: %s' % rsp)
        elif cmd:
            _sshv1respondbytes(self._fout, b'')
        return cmd != ''

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