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Implement URL normalization in code snippet handler #3409

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Implement URL normalization in code snippet handler #3409

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15 changes: 15 additions & 0 deletions bot/exts/info/code_snippets.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@
from urllib.parse import quote_plus

import discord
import yarl
from aiohttp import ClientResponseError
from discord.ext.commands import Cog

Expand Down Expand Up @@ -272,6 +273,20 @@ async def _parse_snippets(self, content: str) -> str:

for pattern, handler in self.pattern_handlers:
for match in pattern.finditer(content):
# ensure that the matched URL meets url normalization rules.
# parsing with yarl resolves all parent urls such as `/../`,
# we then check the regex again to make sure our groups stay the same
unsanitized = match.group(0)
normalized = str(yarl.URL(unsanitized))
if normalized != unsanitized:
match = pattern.fullmatch(normalized)
if not match:
log.info(
"Received code snippet url %s which "
"attempted to circumvent url normalisation.",
unsanitized
)
continue
try:
result = await handler(**match.groupdict())
except ClientResponseError as error:
Expand Down