d672583830
Share a download by a capability URL (/watch/{token}) that anyone can play on a login-free page —
distinct from the registered-user ACL share. Per-link controls: optional expiry, allow-download
toggle (stream-only vs downloadable), optional argon2 password. Revoke = delete.
- migration 0042 + DownloadLink model; app/downloads/links.py (token, HMAC grant sign/verify)
- owner endpoints (POST/GET/PATCH/DELETE links) + /recipients for the internal user picker
- public router (no auth): watch meta / password unlock→signed grant / range-aware file serve
(inline vs attachment); unlock is rate-limited; meta verifies the file exists on disk
Verified end-to-end: 206 range, inline vs attachment, wrong-password 403, tampered-grant 403.
81 lines
2.9 KiB
Python
81 lines
2.9 KiB
Python
"""Public "share by link" helpers for the download center.
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A DownloadLink is a capability URL: the unguessable `token` grants anyone read access to one
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download's file on the login-free `/watch/{token}` page. Password-protected links additionally
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require a short-lived signed **grant** on the file request — because a `<video src>` can't send a
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header, the password is exchanged once at `/unlock` for an HMAC grant appended to the file URL,
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so the raw password never rides in the media URL (or server logs).
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"""
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import hashlib
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import hmac
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import secrets
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from datetime import datetime, timezone
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from app.config import settings
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from app.models import DownloadLink
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_GRANT_TTL = 6 * 3600 # a watch session's grant is good for 6h, then the viewer re-unlocks
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def new_token() -> str:
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return secrets.token_urlsafe(24) # ~32 chars, 192 bits
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def is_expired(link: DownloadLink) -> bool:
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return link.expires_at is not None and link.expires_at <= datetime.now(timezone.utc)
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# --- signed grants (password-protected file access) ----------------------------------------
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def _sign(msg: str) -> str:
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return hmac.new(
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settings.secret_key.encode(), msg.encode(), hashlib.sha256
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).hexdigest()[:32]
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def make_grant(token: str, now: float | None = None) -> str:
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"""A short-lived HMAC grant proving the viewer unlocked `token`. Format: `<exp>.<sig>`."""
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exp = int((now if now is not None else datetime.now(timezone.utc).timestamp())) + _GRANT_TTL
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return f"{exp}.{_sign(f'{token}.{exp}')}"
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def check_grant(token: str, grant: str | None) -> bool:
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if not grant or "." not in grant:
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return False
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exp_s, sig = grant.split(".", 1)
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try:
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exp = int(exp_s)
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except ValueError:
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return False
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if exp < datetime.now(timezone.utc).timestamp():
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return False
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return hmac.compare_digest(sig, _sign(f"{token}.{exp}"))
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# --- serialization -------------------------------------------------------------------------
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def owner_view(link: DownloadLink, base_url: str = "") -> dict:
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"""What the file owner sees when managing their links."""
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return {
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"id": link.id,
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"token": link.token,
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"url": f"{base_url}/watch/{link.token}",
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"allow_download": link.allow_download,
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"has_password": link.password_hash is not None,
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"expires_at": link.expires_at.isoformat() if link.expires_at else None,
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"view_count": link.view_count,
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"created_at": link.created_at.isoformat() if link.created_at else None,
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}
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def public_meta(link: DownloadLink, asset, file_url: str) -> dict:
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"""Metadata for the public watch page (only ever returned once access is authorized)."""
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return {
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"title": asset.title,
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"uploader": asset.uploader,
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"duration_s": asset.duration_s,
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"width": asset.width,
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"height": asset.height,
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"allow_download": link.allow_download,
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"file_url": file_url,
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}
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