bridgy-fed/redirect.py

87 wiersze
2.8 KiB
Python

"""Simple endpoint that redirects to the embedded fully qualified URL.
May also instead fetch and convert to AS2, depending on conneg.
Used to wrap ActivityPub ids with the fed.brid.gy domain so that Mastodon
accepts them. Background:
https://github.com/snarfed/bridgy-fed/issues/16#issuecomment-424799599
https://github.com/tootsuite/mastodon/pull/6219#issuecomment-429142747
"""
import datetime
import logging
import re
import urllib.parse
from flask import redirect, request
from granary import as2, microformats2
import mf2util
from oauth_dropins.webutil import util
from oauth_dropins.webutil.util import json_dumps
from werkzeug.exceptions import abort
from app import app, cache
import common
from common import error
from models import MagicKey
CACHE_TIME = datetime.timedelta(seconds=15)
@app.get(r'/r/<path:to>')
@cache.cached(timeout=CACHE_TIME.total_seconds(), query_string=True,
response_filter=common.not_5xx)
def redir(to=None):
"""301 redirect to the embedded fully qualified URL.
e.g. redirects /r/https://foo.com/bar?baz to https://foo.com/bar?baz
"""
if request.args:
to += '?' + urllib.parse.urlencode(request.args)
# some browsers collapse repeated /s in the path down to a single slash.
# if that happened to this URL, expand it back to two /s.
to = re.sub(r'^(https?:/)([^/])', r'\1/\2', to)
if not to.startswith('http://') and not to.startswith('https://'):
return error(f'Expected fully qualified URL; got {to}')
# check that we've seen this domain before so we're not an open redirect
domains = set((util.domain_from_link(to),
urllib.parse.urlparse(to).hostname))
for domain in domains:
if MagicKey.get_by_id(domain):
logging.info(f'Found MagicKey for domain {domain}')
break
else:
logging.info(f'No user found for any of {domains}; returning 404')
abort(404)
# poor man's conneg, only handle single Accept values, not multiple with
# priorities.
if request.headers.get('Accept') in (common.CONTENT_TYPE_AS2,
common.CONTENT_TYPE_AS2_LD):
return convert_to_as2(to)
# redirect
logging.info('redirecting to %s', to)
return redirect(to, code=301)
def convert_to_as2(url):
"""Fetch a URL as HTML, convert it to AS2, and return it.
Currently mainly for Pixelfed.
https://github.com/snarfed/bridgy-fed/issues/39
"""
mf2 = util.fetch_mf2(url)
entry = mf2util.find_first_entry(mf2, ['h-entry'])
logging.info('Parsed mf2 for %s: %s', mf2['url'], json_dumps(entry, indent=2))
obj = common.postprocess_as2(as2.from_as1(microformats2.json_to_object(entry)))
logging.info('Returning: %s', json_dumps(obj, indent=2))
return obj, {
'Content-Type': common.CONTENT_TYPE_AS2,
'Access-Control-Allow-Origin': '*',
}