kopia lustrzana https://github.com/snarfed/bridgy-fed
145 wiersze
5.0 KiB
Python
145 wiersze
5.0 KiB
Python
"""Simple conneg endpoint that serves AS2 or redirects to to the original post.
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Only for :class:`web.Web` users. Other protocols (including :class:`web.Web`
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sometimes) use ``/convert/`` in convert.py instead.
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Serves ``/r/https://foo.com/bar`` URL paths, where ``https://foo.com/bar`` is a
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original post for a :class:`Web` user. Needed for Mastodon interop, they require
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that AS2 object ids and urls are on the same domain that serves them.
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Background:
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* https://github.com/snarfed/bridgy-fed/issues/16#issuecomment-424799599
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* https://github.com/tootsuite/mastodon/pull/6219#issuecomment-429142747
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The conneg makes these ``/r/`` URLs searchable in Mastodon:
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https://github.com/snarfed/bridgy-fed/issues/352
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"""
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import logging
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import re
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import urllib.parse
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from flask import g, request
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from granary import as2
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from negotiator import ContentNegotiator, AcceptParameters, ContentType
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from oauth_dropins.webutil import flask_util, util
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from oauth_dropins.webutil.flask_util import error
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from oauth_dropins.webutil.util import json_dumps, json_loads
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from activitypub import ActivityPub
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from common import CACHE_TIME, CONTENT_TYPE_HTML
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from flask_app import app, cache
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from protocol import Protocol
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from web import Web
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logger = logging.getLogger(__name__)
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_negotiator = ContentNegotiator(acceptable=[
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AcceptParameters(ContentType(CONTENT_TYPE_HTML)),
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AcceptParameters(ContentType(as2.CONTENT_TYPE)),
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AcceptParameters(ContentType(as2.CONTENT_TYPE_LD)),
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])
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DOMAIN_ALLOWLIST = frozenset((
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'bsky.app',
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))
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VARY_HEADER = {'Vary': 'Accept'}
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@app.get(r'/r/<path:to>')
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@flask_util.cached(cache, CACHE_TIME, headers=['Accept'])
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def redir(to):
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"""Either redirect to a given URL or convert it to another format.
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E.g. redirects ``/r/https://foo.com/bar?baz`` to
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``https://foo.com/bar?baz``, or if it's requested with AS2 conneg in the
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``Accept`` header, fetches and converts and serves it as AS2.
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"""
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if request.args:
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to += '?' + urllib.parse.urlencode(request.args)
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# some browsers collapse repeated /s in the path down to a single slash.
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# if that happened to this URL, expand it back to two /s.
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to = re.sub(r'^(https?:/)([^/])', r'\1/\2', to)
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if not util.is_web(to):
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error(f'Expected fully qualified URL; got {to}')
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try:
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to_domain = urllib.parse.urlparse(to).hostname
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except ValueError as e:
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error(f'Invalid URL {to} : {e}')
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# check conneg
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accept_as2 = False
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accept = request.headers.get('Accept')
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if accept:
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try:
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negotiated = _negotiator.negotiate(accept)
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except ValueError:
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# work around https://github.com/CottageLabs/negotiator/issues/6
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negotiated = None
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if negotiated:
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accept_type = str(negotiated.content_type)
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if accept_type in (as2.CONTENT_TYPE, as2.CONTENT_TYPE_LD):
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accept_as2 = True
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# check that we've seen this domain before so we're not an open redirect
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domains = set((util.domain_from_link(to, minimize=True),
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util.domain_from_link(to, minimize=False),
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to_domain))
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web_user = None
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for domain in domains:
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if domain:
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if domain in DOMAIN_ALLOWLIST:
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break
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if web_user := Web.get_by_id(domain):
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logger.info(f'Found web user for domain {domain}')
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break
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else:
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if not accept_as2:
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return f'No web user found for any of {domains}', 404, VARY_HEADER
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if not accept_as2:
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# redirect. include rel-alternate link to make posts discoverable by entering
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# https://fed.brid.gy/r/[URL] in a fediverse instance's search.
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logger.info(f'redirecting to {to}')
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return f"""\
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<!doctype html>
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<html>
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<head>
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<link href="{request.url}" rel="alternate" type="application/activity+json">
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</head>
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<title>Redirecting...</title>
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<h1>Redirecting...</h1>
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<p>You should be redirected automatically to the target URL: <a href="{to}">{to}</a>. If not, click the link.
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</html>
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""", 301, {
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'Location': to,
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**VARY_HEADER,
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}
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# AS2 requested, fetch and convert and serve
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proto = Protocol.for_id(to)
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if not proto:
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return f"Couldn't determine protocol for {to}", 404, VARY_HEADER
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obj = proto.load(to)
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if not obj or obj.deleted:
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return f'Object not found: {to}', 404, VARY_HEADER
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# TODO: do this for other protocols too?
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if proto == Web and not web_user:
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web_user = Web.get_or_create(util.domain_from_link(to), direct=False, obj=obj)
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if not web_user:
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return f'Object not found: {to}', 404, VARY_HEADER
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ret = ActivityPub.convert(obj, from_user=web_user)
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logger.info(f'Returning: {json_dumps(ret, indent=2)}')
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return ret, {
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'Content-Type': (as2.CONTENT_TYPE_LD_PROFILE
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if accept_type == as2.CONTENT_TYPE_LD
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else accept_type),
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'Access-Control-Allow-Origin': '*',
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**VARY_HEADER,
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}
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