annotate mercurial/hgweb/common.py @ 50439:4077d6222cf1

hgweb: add support to explicitly access hidden changesets

This changeset adds a "global" `access-hidden` argument to hgweb. This argument
lift the "hidden" filtering. This means the request has access to hidden (eg:
obsolete) changesets. Secret changesets remains filtered.

This feature has multiple applications. The first main use case is to allow the
hgweb interface to display more obsolescence related data, such as the Anton
Shestakov work to add `obslog` support to hgweb.

The second foreseen usecase is support for a `--remote-hidden` argument to `hg
pull` and `hg clone`. This flag will make it possible to retrieve hidden
(typically obsolete) changeset under some conditions. This is useful when
digging up obsolescence history or when doing full mirroring. More on this
feature coming in later changesets.

To avoid exposing information by mistake, access to this feature is currently
controlled with the `experimental.server.allow-hidden-access` config option. The
option works the same way as `web.allow-push`. The current default is to not
allow any hidden access. However we might change it before the feature stop
being experimental.

# hgweb/common.py - Utility functions needed by hgweb_mod and hgwebdir_mod
#
# Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
# Copyright 2005, 2006 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 base64
import errno
import mimetypes
import os
import stat

from ..i18n import _
from ..pycompat import (
    getattr,
    open,
)
from .. import (
    encoding,
    pycompat,
    templater,
    util,
)

httpserver = util.httpserver

HTTP_OK = 200
HTTP_CREATED = 201
HTTP_NOT_MODIFIED = 304
HTTP_BAD_REQUEST = 400
HTTP_UNAUTHORIZED = 401
HTTP_FORBIDDEN = 403
HTTP_NOT_FOUND = 404
HTTP_METHOD_NOT_ALLOWED = 405
HTTP_NOT_ACCEPTABLE = 406
HTTP_UNSUPPORTED_MEDIA_TYPE = 415
HTTP_SERVER_ERROR = 500


def ismember(ui, username, userlist):
    """Check if username is a member of userlist.

    If userlist has a single '*' member, all users are considered members.
    Can be overridden by extensions to provide more complex authorization
    schemes.
    """
    return userlist == [b'*'] or username in userlist


def hashiddenaccess(repo, req):
    if bool(req.qsparams.get(b'access-hidden')):
        # Disable this by default for now. Main risk is to get critical
        # information exposed through this. This is expecially risky if
        # someone decided to make a changeset secret for good reason, but
        # its predecessors are still draft.
        #
        # The feature is currently experimental, so we can still decide to
        # change the default.
        ui = repo.ui
        allow = ui.configlist(b'experimental', b'server.allow-hidden-access')
        user = req.remoteuser
        if allow and ismember(ui, user, allow):
            return True
        else:
            msg = (
                _(
                    b'ignoring request to access hidden changeset by '
                    b'unauthorized user: %r\n'
                )
                % user
            )
            ui.warn(msg)
    return False


def checkauthz(hgweb, req, op):
    """Check permission for operation based on request data (including
    authentication info). Return if op allowed, else raise an ErrorResponse
    exception."""

    user = req.remoteuser

    deny_read = hgweb.configlist(b'web', b'deny_read')
    if deny_read and (not user or ismember(hgweb.repo.ui, user, deny_read)):
        raise ErrorResponse(HTTP_UNAUTHORIZED, b'read not authorized')

    allow_read = hgweb.configlist(b'web', b'allow_read')
    if allow_read and (not ismember(hgweb.repo.ui, user, allow_read)):
        raise ErrorResponse(HTTP_UNAUTHORIZED, b'read not authorized')

    if op == b'pull' and not hgweb.allowpull:
        raise ErrorResponse(HTTP_UNAUTHORIZED, b'pull not authorized')
    elif op == b'pull' or op is None:  # op is None for interface requests
        return

    # Allow LFS uploading via PUT requests
    if op == b'upload':
        if req.method != b'PUT':
            msg = b'upload requires PUT request'
            raise ErrorResponse(HTTP_METHOD_NOT_ALLOWED, msg)
    # enforce that you can only push using POST requests
    elif req.method != b'POST':
        msg = b'push requires POST request'
        raise ErrorResponse(HTTP_METHOD_NOT_ALLOWED, msg)

    # require ssl by default for pushing, auth info cannot be sniffed
    # and replayed
    if hgweb.configbool(b'web', b'push_ssl') and req.urlscheme != b'https':
        raise ErrorResponse(HTTP_FORBIDDEN, b'ssl required')

    deny = hgweb.configlist(b'web', b'deny_push')
    if deny and (not user or ismember(hgweb.repo.ui, user, deny)):
        raise ErrorResponse(HTTP_UNAUTHORIZED, b'push not authorized')

    allow = hgweb.configlist(b'web', b'allow-push')
    if not (allow and ismember(hgweb.repo.ui, user, allow)):
        raise ErrorResponse(HTTP_UNAUTHORIZED, b'push not authorized')


# Hooks for hgweb permission checks; extensions can add hooks here.
# Each hook is invoked like this: hook(hgweb, request, operation),
# where operation is either read, pull, push or upload. Hooks should either
# raise an ErrorResponse exception, or just return.
#
# It is possible to do both authentication and authorization through
# this.
permhooks = [checkauthz]


class ErrorResponse(Exception):
    def __init__(self, code, message=None, headers=None):
        if message is None:
            message = _statusmessage(code)
        Exception.__init__(self, pycompat.sysstr(message))
        self.code = code
        if headers is None:
            headers = []
        self.headers = headers
        self.message = message


class continuereader:
    """File object wrapper to handle HTTP 100-continue.

    This is used by servers so they automatically handle Expect: 100-continue
    request headers. On first read of the request body, the 100 Continue
    response is sent. This should trigger the client into actually sending
    the request body.
    """

    def __init__(self, f, write):
        self.f = f
        self._write = write
        self.continued = False

    def read(self, amt=-1):
        if not self.continued:
            self.continued = True
            self._write(b'HTTP/1.1 100 Continue\r\n\r\n')
        return self.f.read(amt)

    def __getattr__(self, attr):
        if attr in (b'close', b'readline', b'readlines', b'__iter__'):
            return getattr(self.f, attr)
        raise AttributeError


def _statusmessage(code):
    responses = httpserver.basehttprequesthandler.responses
    return pycompat.bytesurl(responses.get(code, ('Error', 'Unknown error'))[0])


def statusmessage(code, message=None):
    return b'%d %s' % (code, message or _statusmessage(code))


def get_stat(spath, fn):
    """stat fn if it exists, spath otherwise"""
    cl_path = os.path.join(spath, fn)
    if os.path.exists(cl_path):
        return os.stat(cl_path)
    else:
        return os.stat(spath)


def get_mtime(spath):
    return get_stat(spath, b"00changelog.i")[stat.ST_MTIME]


def ispathsafe(path):
    """Determine if a path is safe to use for filesystem access."""
    parts = path.split(b'/')
    for part in parts:
        if (
            part in (b'', pycompat.oscurdir, pycompat.ospardir)
            or pycompat.ossep in part
            or pycompat.osaltsep is not None
            and pycompat.osaltsep in part
        ):
            return False

    return True


def staticfile(templatepath, directory, fname, res):
    """return a file inside directory with guessed Content-Type header

    fname always uses '/' as directory separator and isn't allowed to
    contain unusual path components.
    Content-Type is guessed using the mimetypes module.
    Return an empty string if fname is illegal or file not found.

    """
    if not ispathsafe(fname):
        return

    if not directory:
        tp = templatepath or templater.templatedir()
        if tp is not None:
            directory = os.path.join(tp, b'static')

    fpath = os.path.join(*fname.split(b'/'))
    ct = pycompat.sysbytes(
        mimetypes.guess_type(pycompat.fsdecode(fpath))[0] or r"text/plain"
    )
    path = os.path.join(directory, fpath)
    try:
        os.stat(path)
        with open(path, b'rb') as fh:
            data = fh.read()
    except TypeError:
        raise ErrorResponse(HTTP_SERVER_ERROR, b'illegal filename')
    except OSError as err:
        if err.errno == errno.ENOENT:
            raise ErrorResponse(HTTP_NOT_FOUND)
        else:
            raise ErrorResponse(
                HTTP_SERVER_ERROR, encoding.strtolocal(err.strerror)
            )

    res.headers[b'Content-Type'] = ct
    res.setbodybytes(data)
    return res


def paritygen(stripecount, offset=0):
    """count parity of horizontal stripes for easier reading"""
    if stripecount and offset:
        # account for offset, e.g. due to building the list in reverse
        count = (stripecount + offset) % stripecount
        parity = (stripecount + offset) // stripecount & 1
    else:
        count = 0
        parity = 0
    while True:
        yield parity
        count += 1
        if stripecount and count >= stripecount:
            parity = 1 - parity
            count = 0


def get_contact(config):
    """Return repo contact information or empty string.

    web.contact is the primary source, but if that is not set, try
    ui.username or $EMAIL as a fallback to display something useful.
    """
    return (
        config(b"web", b"contact")
        or config(b"ui", b"username")
        or encoding.environ.get(b"EMAIL")
        or b""
    )


def cspvalues(ui):
    """Obtain the Content-Security-Policy header and nonce value.

    Returns a 2-tuple of the CSP header value and the nonce value.

    First value is ``None`` if CSP isn't enabled. Second value is ``None``
    if CSP isn't enabled or if the CSP header doesn't need a nonce.
    """
    # Without demandimport, "import uuid" could have an immediate side-effect
    # running "ldconfig" on Linux trying to find libuuid.
    # With Python <= 2.7.12, that "ldconfig" is run via a shell and the shell
    # may pollute the terminal with:
    #
    #   shell-init: error retrieving current directory: getcwd: cannot access
    #   parent directories: No such file or directory
    #
    # Python >= 2.7.13 has fixed it by running "ldconfig" directly without a
    # shell (hg changeset a09ae70f3489).
    #
    # Moved "import uuid" from here so it's executed after we know we have
    # a sane cwd (i.e. after dispatch.py cwd check).
    #
    # We can move it back once we no longer need Python <= 2.7.12 support.
    import uuid

    # Don't allow untrusted CSP setting since it be disable protections
    # from a trusted/global source.
    csp = ui.config(b'web', b'csp', untrusted=False)
    nonce = None

    if csp and b'%nonce%' in csp:
        nonce = base64.urlsafe_b64encode(uuid.uuid4().bytes).rstrip(b'=')
        csp = csp.replace(b'%nonce%', nonce)

    return csp, nonce