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from __future__ import annotations
from collections.abc import Callable
from contextlib import suppress
import re
from urllib.parse import quote, unquote, urlparse, urlunparse # noqa: F401
import mdurl
from .. import _punycode
RECODE_HOSTNAME_FOR = ("http:", "https:", "mailto:")
def normalizeLink(url: str) -> str:
"""Normalize destination URLs in links
::
[label]: destination 'title'
^^^^^^^^^^^
"""
parsed = mdurl.parse(url, slashes_denote_host=True)
# Encode hostnames in urls like:
#
# We don't encode unknown schemas, because it's likely that we encode
# something we shouldn't (e.g. `skype:name` treated as `skype:host`)
#
if parsed.hostname and (
not parsed.protocol or parsed.protocol in RECODE_HOSTNAME_FOR
):
with suppress(Exception):
parsed = parsed._replace(hostname=_punycode.to_ascii(parsed.hostname))
return mdurl.encode(mdurl.format(parsed))
def normalizeLinkText(url: str) -> str:
"""Normalize autolink content
::
<destination>
~~~~~~~~~~~
"""
parsed = mdurl.parse(url, slashes_denote_host=True)
# Encode hostnames in urls like:
#
# We don't encode unknown schemas, because it's likely that we encode
# something we shouldn't (e.g. `skype:name` treated as `skype:host`)
#
if parsed.hostname and (
not parsed.protocol or parsed.protocol in RECODE_HOSTNAME_FOR
):
with suppress(Exception):
parsed = parsed._replace(hostname=_punycode.to_unicode(parsed.hostname))
return mdurl.decode(mdurl.format(parsed), mdurl.DECODE_DEFAULT_CHARS + "%")
BAD_PROTO_RE = re.compile(r"^(vbscript|javascript|file|data):")
GOOD_DATA_RE = re.compile(r"^data:image\/(gif|png|jpeg|webp);")
def validateLink(url: str, validator: Callable[[str], bool] | None = None) -> bool:
"""Validate URL link is allowed in output.
This validator can prohibit more than really needed to prevent XSS.
It's a tradeoff to keep code simple and to be secure by default.
Note: url should be normalized at this point, and existing entities decoded.
"""
if validator is not None:
return validator(url)
url = url.strip().lower()
return bool(GOOD_DATA_RE.search(url)) if BAD_PROTO_RE.search(url) else True