58 lines
2.3 KiB
Python
58 lines
2.3 KiB
Python
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"""
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Copyright 2024-2026 ChatterMate
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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"""
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"""Short-lived signed URLs for private files in local (non-S3) storage.
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The local counterpart of an S3 presigned URL: an HMAC binds the storage key to
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an expiry, so a link works for whoever holds it until it expires, and for no
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other file. Bearer links rather than session auth because the widget renders
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attachments with plain <img>/<a> tags, which cannot send a token header.
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"""
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import hashlib
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import hmac
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import time
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from typing import Optional
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from urllib.parse import quote, urlencode
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from app.core.config import settings
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LOCAL_FILE_ROUTE = f"{settings.API_V1_STR}/files/local"
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# SECRET_KEY also signs JWTs; the purpose prefix keeps the two from ever
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# validating each other.
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_PURPOSE = b"chattermate:local-file-url:v1\n"
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def _signature(key: str, expires: int) -> str:
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message = _PURPOSE + f"{key}\n{expires}".encode()
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return hmac.new(settings.SECRET_KEY.encode(), message, hashlib.sha256).hexdigest()
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def sign_local_key(key: str, expires_in: Optional[int] = None) -> str:
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"""Relative URL serving ``key`` (a path under uploads/) until it expires.
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Lifetime follows S3_PRESIGN_EXPIRY_SECONDS, so both backends behave alike."""
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lifetime = settings.S3_PRESIGN_EXPIRY_SECONDS if expires_in is None else expires_in
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expires = int(time.time()) + lifetime
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query = urlencode({"exp": expires, "sig": _signature(key, expires)})
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return f"{LOCAL_FILE_ROUTE}/{quote(key)}?{query}"
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def verify_local_signature(key: str, expires: Optional[int], signature: Optional[str]) -> bool:
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"""True when ``signature`` was issued for ``key`` and has not expired."""
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if expires is None or not signature or expires < time.time():
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return False
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return hmac.compare_digest(_signature(key, expires), signature)
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