webhooks.py

import hashlib
import hmac
import logging
from base64 import b64encode
from collections import OrderedDict
from datetime import datetime
from urllib.error import HTTPError
from urllib.parse import urlencode, urlsplit, urlunsplit
from urllib.request import Request, urlopen

from django.contrib.sites.models import Site
from django.db.models import Model
from django.db.models.query import QuerySet
from django.http.request import HttpRequest
from django.utils.encoding import force_bytes, force_str
from django.utils.functional import cached_property
from django.utils.safestring import SafeText
from django.utils.text import get_text_list
from django.utils.translation import gettext as _
from django.template import Context, Template
from django.template.base import Lexer, Parser
from djblets.siteconfig.models import SiteConfiguration
from djblets.webapi.encoders import (BasicAPIEncoder, JSONEncoderAdapter,
                                     ResourceAPIEncoder, XMLEncoderAdapter)

from reviewboard import get_package_version
from reviewboard.notifications.models import WebHookTarget
from reviewboard.reviews.models import Review, ReviewRequest
from reviewboard.reviews.signals import (review_request_closed,
                                         review_request_published,
                                         review_request_reopened,
                                         review_published,
                                         reply_published)


logger = logging.getLogger(__name__)


class FakeHTTPRequest(HttpRequest):
    """A fake HttpRequest implementation.

    The WebAPI serialization methods use HttpRequest.build_absolute_uri to
    generate all the links, but none of the various signals that generate
    webhook events have the request plumbed through. Since we don't actually
    need a valid request, this impersonates it enough to get valid results from
    build_absolute_uri.
    """

    def __init__(self, user, local_site_name=None):
        """Initialize a FakeHTTPRequest.

        Args:
            user (django.contrib.auth.models.User):
                The user who initiated the request.

            local_site_name (unicode, optional):
                The local site name (if the request was carried out against a
                local site).
        """
        super(FakeHTTPRequest, self).__init__()

        self.user = user
        self._local_site_name = local_site_name
        self._host = Site.objects.get_current().domain

    @cached_property
    def scheme(self):
        """The protocol scheme used to access the web server.

        This is needed by the underlying class to build absolute URLs. It
        returns the scheme from the current site configuration.

        Version Added:
            4.0.3

        Type:
            unicode
        """
        siteconfig = SiteConfiguration.objects.get_current()

        return siteconfig.get('site_domain_method')

    def get_host(self):
        """Return the hostname for the server.

        This is needed by the underlying class to build absolute URLs. It
        returns the hostname from the configured site information.

        Returns:
            unicode:
            The hostname.
        """
        return self._host


class CustomPayloadParser(Parser):
    """A custom template parser that blocks certain tags.

    This extends Django's Parser class for template parsing, and removes
    some built-in tags, in order to prevent mailicious use.
    """
    BLACKLISTED_TAGS = ('block', 'debug', 'extends', 'include', 'load', 'ssi')

    def __init__(self, *args, **kwargs):
        super(CustomPayloadParser, self).__init__(*args, **kwargs)

        # Remove some built-in tags that we don't want to expose.
        # There are no built-in filters we have to worry about.
        for tag_name in self.BLACKLISTED_TAGS:
            try:
                del self.tags[tag_name]
            except KeyError:
                pass

    def invalid_block_tag(self, token, command, parse_until=None):
        """Raise an error when an invalid block tag is found.

        Normally Django produces a suitable error, but in modern versions of
        Django, the error is _too_ helpful, reminding the user to register or
        load the tag. This isn't useful for WebHooks, so we override to use
        the older, simpler message used in Django 1.6.

        Args:
            token (django.template.base.Token):
                The token representing the block tag.

            command (unicode):
                The name of the block tag that was found.

            parse_until (list of django.template.base.Token, optional):
                The list of tokens that were expected to be parsed instead
                of this token.
        """
        if parse_until:
            raise self.error(
                token,
                _("Invalid block tag: '%(found_tag)s', expected "
                  "%(expected_tag)s")
                % {
                    'found_tag': command,
                    'expected_tag': get_text_list([
                        "'%s'" % tag
                        for tag in parse_until
                    ]),
                })
        else:
            raise self.error(token, "Invalid block tag: '%s'" % command)


def render_custom_content(body, context_data={}):
    """Render custom content for the payload using Django templating.

    This will take the custom payload content template provided by
    the user and render it using a stripped down version of Django's
    templating system.

    In order to keep the payload safe, we use a limited Context along with a
    custom Parser that blocks certain template tags. This gives us
    tags like ``{% for %}`` and ``{% if %}``, but blacklists tags like
    ``{% load %}`` and ``{% include %}``.

    Args:
        body (unicode):
            The template content to render.

        context_data (dict, optional):
            Context data for the template.

    Returns:
        unicode:
        The rendered template.

    Raises:
        django.template.TemplateSyntaxError:
            There was a syntax error in the template.
    """
    template = Template('')
    lexer = Lexer(body)
    parser_args = (template.engine.template_libraries,
                   template.engine.template_builtins,
                   template.origin)

    parser = CustomPayloadParser(lexer.tokenize(), *parser_args)
    template.nodelist = parser.parse()

    return template.render(Context(context_data))


def normalize_webhook_payload(payload, request, use_string_keys=False):
    """Normalize a payload for a WebHook, returning a safe, primitive version.

    This will take a payload containing various data types and model references
    and turn it into a payload built out of specific, whitelisted types
    (strings, bools, ints, dicts, lists, and datetimes). This payload is
    safe to include in custom templates without worrying about access to
    dangerous functions, and is easy to serialize.

    Args:
        payload (dict):
            The payload to normalize.

        request (django.http.HttpRequest):
            The HTTP request from the client.

        use_string_keys (bool, optional):
            Whether to normalize all keys to strings.

    Returns:
        dict:
        The normalized payload.

    Raises:
        TypeError:
            An unsupported data type was found in the payload. This is an
            issue with the caller.
    """
    def _normalize_key(key):
        if key is None:
            if use_string_keys:
                return 'null'

            return None
        elif isinstance(key, str):
            return key
        elif isinstance(key, (SafeText, bool, float)):
            return str(key)
        elif isinstance(key, bytes):
            return force_str(key)
        elif isinstance(key, int):
            if use_string_keys:
                return force_str(key)

            return key
        else:
            raise TypeError(
                _('%s is not a valid data type for dictionary keys in '
                  'WebHook payloads.')
                % type(key))

    def _normalize_value(value):
        if value is None:
            return None

        if isinstance(value, SafeText):
            return str(value)
        elif isinstance(value, bytes):
            return force_str(value)
        elif isinstance(value, (bool, datetime, float, str, int)):
            return value
        elif isinstance(value, dict):
            return OrderedDict(
                (_normalize_key(dict_key), _normalize_value(dict_value))
                for dict_key, dict_value in value.items()
            )
        elif isinstance(value, (list, tuple)):
            return [
                _normalize_value(item)
                for item in value
            ]
        elif isinstance(value, (Model, QuerySet)):
            result = resource_encoder.encode(value, request=request)

            if result is not None:
                return _normalize_value(result)

        raise TypeError(
            _('%s is not a valid data type for values in WebHook payloads.')
            % type(value))

    resource_encoder = ResourceAPIEncoder()

    return _normalize_value(payload)


def dispatch_webhook_event(request, webhook_targets, event, payload):
    """Dispatch the given event and payload to the given WebHook targets.

    Args:
        request (django.http.HttpRequest):
            The HTTP request from the client.

        webhook_targets (list of
                         reviewboard.notifications.models.WebHookTarget):
            The list of WebHook targets containing endpoint URLs to dispatch
            to.

        event (unicode):
            The name of the event being dispatched.

        payload (dict):
            The payload data to encode for the WebHook payload.

    Raises:
        ValueError:
            There was an error with the payload format. Details are in the
            log and the exception message.
    """
    encoder = BasicAPIEncoder()
    bodies = {}

    raw_norm_payload = None
    json_norm_payload = None

    for webhook_target in webhook_targets:
        use_custom_content = webhook_target.use_custom_content
        encoding = webhook_target.encoding

        # See how we need to handle normalizing this payload. If we need
        # something JSON-safe, then we need to go the more aggressive route
        # and normalize keys to strings.
        if raw_norm_payload is None or json_norm_payload is None:
            try:
                if (raw_norm_payload is None and
                    (use_custom_content or
                     encoding == webhook_target.ENCODING_XML)):
                    # This payload's going to be provided for XML and custom
                    # templates. We don't want to alter the keys at all.
                    raw_norm_payload = normalize_webhook_payload(
                        payload=payload,
                        request=request)
                elif (json_norm_payload is None and
                      not use_custom_content and
                      encoding in (webhook_target.ENCODING_JSON,
                                   webhook_target.ENCODING_FORM_DATA)):
                    # This payload's going to be provided for JSON or
                    # form-data. We want to normalize all keys to strings.
                    json_norm_payload = normalize_webhook_payload(
                        payload=payload,
                        request=request,
                        use_string_keys=True)
            except TypeError as e:
                logger.exception('WebHook payload passed to '
                                 'dispatch_webhook_event containing invalid '
                                 'data types: %s',
                                 e,
                                 extra={'request': request})

                raise ValueError(str(e))

        if use_custom_content:
            try:
                assert raw_norm_payload is not None
                body = render_custom_content(webhook_target.custom_content,
                                             raw_norm_payload)
                body = force_bytes(body)
            except Exception as e:
                logger.exception('Could not render WebHook payload: %s', e,
                                 extra={'request': request})
                continue
        else:
            if encoding not in bodies:
                try:
                    if encoding == webhook_target.ENCODING_JSON:
                        assert json_norm_payload is not None
                        adapter = JSONEncoderAdapter(encoder)
                        body = adapter.encode(json_norm_payload,
                                              request=request)
                    elif encoding == webhook_target.ENCODING_XML:
                        assert raw_norm_payload is not None
                        adapter = XMLEncoderAdapter(encoder)
                        body = adapter.encode(raw_norm_payload,
                                              request=request)
                    elif encoding == webhook_target.ENCODING_FORM_DATA:
                        assert json_norm_payload is not None
                        adapter = JSONEncoderAdapter(encoder)
                        body = urlencode({
                            'payload': adapter.encode(json_norm_payload,
                                                      request=request),
                        })
                    else:
                        logger.error('Unexpected WebHookTarget encoding "%s" '
                                     'for ID %s',
                                     encoding, webhook_target.pk,
                                     extra={'request': request})
                        continue
                except Exception as e:
                    logger.exception('Could not encode WebHook payload: %s',
                                     e,
                                     extra={'request': request})
                    continue

                body = force_bytes(body)
                bodies[encoding] = body
            else:
                body = bodies[encoding]

        headers = {
            'X-ReviewBoard-Event': event,
            'Content-Type': webhook_target.encoding,
            'Content-Length': '%s' % len(body),
            'User-Agent': 'ReviewBoard-WebHook/%s' % get_package_version(),
        }

        if webhook_target.secret:
            signer = hmac.new(webhook_target.secret.encode('utf-8'), body,
                              hashlib.sha1)
            headers['X-Hub-Signature'] = 'sha1=%s' % signer.hexdigest()

        logger.info('Dispatching webhook for event %s to %s',
                    event, webhook_target.url,
                    extra={'request': request})

        try:
            url = webhook_target.url
            url_parts = urlsplit(url)

            if url_parts.username or url_parts.password:
                credentials, netloc = url_parts.netloc.split('@', 1)
                url = urlunsplit(
                    (url_parts.scheme, netloc, url_parts.path,
                     url_parts.query, url_parts.fragment))
                headers['Authorization'] = \
                    'Basic %s' % b64encode(credentials.encode('utf-8'))

            urlopen(Request(url, body, headers))
        except Exception as e:
            logger.exception('Could not dispatch WebHook to %s: %s',
                             webhook_target.url, e,
                             extra={'request': request})

            if isinstance(e, HTTPError):
                logger.info('Error response from %s: %s %s\n%s',
                            webhook_target.url, e.code, e.reason, e.read(),
                            extra={'request': request})


def _serialize_review(review, request):
    return {
        'review_request': review.review_request,
        'review': review,
        'diff_comments': review.comments.all(),
        'file_attachment_comments': review.file_attachment_comments.all(),
        'screenshot_comments': review.screenshot_comments.all(),
        'general_comments': review.general_comments.all(),
    }


def _serialize_reply(reply, request):
    return {
        'review_request': reply.review_request,
        'reply': reply,
        'diff_comments': reply.comments.all(),
        'file_attachment_comments': reply.file_attachment_comments.all(),
        'screenshot_comments': reply.screenshot_comments.all(),
        'general_comments': reply.general_comments.all(),
    }


def review_request_closed_cb(user, review_request, close_type, **kwargs):
    event = 'review_request_closed'
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        if close_type == review_request.SUBMITTED:
            close_type = 'submitted'
        elif close_type == review_request.DISCARDED:
            close_type = 'discarded'
        else:
            logger.error('Unexpected close type %s for review request %s '
                         'when dispatching webhook.',
                         type, review_request.pk)
            return

        if not user:
            user = review_request.submitter

        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = {
            'event': event,
            'closed_by': user,
            'close_type': close_type,
            'review_request': review_request,
        }

        try:
            dispatch_webhook_event(request, webhook_targets, event, payload)
        except ValueError:
            # The error has already been logged. Don't impact the caller.
            pass


def review_request_published_cb(user, review_request, changedesc,
                                **kwargs):
    event = 'review_request_published'
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = {
            'event': event,
            'is_new': changedesc is None,
            'review_request': review_request,
        }

        if changedesc:
            payload['change'] = changedesc

        try:
            dispatch_webhook_event(request, webhook_targets, event, payload)
        except ValueError:
            # The error has already been logged. Don't impact the caller.
            pass


def review_request_reopened_cb(user, review_request, **kwargs):
    event = 'review_request_reopened'
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        if not user:
            user = review_request.submitter

        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = {
            'event': event,
            'reopened_by': user,
            'review_request': review_request,
        }

        try:
            dispatch_webhook_event(request, webhook_targets, event, payload)
        except ValueError:
            # The error has already been logged. Don't impact the caller.
            pass


def review_published_cb(user, review, **kwargs):
    event = 'review_published'
    review_request = review.review_request
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = _serialize_review(review, request)
        payload['event'] = event

        try:
            dispatch_webhook_event(request, webhook_targets, event, payload)
        except ValueError:
            # The error has already been logged. Don't impact the caller.
            pass


def reply_published_cb(user, reply, **kwargs):
    event = 'reply_published'
    review_request = reply.review_request
    webhook_targets = WebHookTarget.objects.for_event(
        event, review_request.local_site_id, review_request.repository_id)

    if review_request.local_site_id:
        local_site_name = review_request.local_site.name
    else:
        local_site_name = None

    if webhook_targets:
        request = FakeHTTPRequest(user, local_site_name=local_site_name)
        payload = _serialize_reply(reply, request)
        payload['event'] = event

        try:
            dispatch_webhook_event(request, webhook_targets, event, payload)
        except ValueError:
            # The error has already been logged. Don't impact the caller.
            pass


def connect_signals():
    review_request_closed.connect(review_request_closed_cb,
                                  sender=ReviewRequest)
    review_request_published.connect(review_request_published_cb,
                                     sender=ReviewRequest)
    review_request_reopened.connect(review_request_reopened_cb,
                                    sender=ReviewRequest)

    review_published.connect(review_published_cb, sender=Review)
    reply_published.connect(reply_published_cb, sender=Review)