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49 lines
1.3 KiB
Python
49 lines
1.3 KiB
Python
import base64
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import time
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from app.config import BASE_URL
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from app.config import hmac_sha256
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SUPPORTED_RESIZE = [50, 740]
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EXPIRY_PERIOD = 86400
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EXPIRY_LENGTH = 7
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class InvalidProxySignatureError(Exception):
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pass
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def proxied_media_sig(expires: int, url: str) -> str:
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hm = hmac_sha256()
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hm.update(f"{expires}".encode())
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hm.update(b"|")
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hm.update(url.encode())
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return base64.urlsafe_b64encode(hm.digest()).decode()
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def verify_proxied_media_sig(expires: int, url: str, sig: str) -> None:
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now = int(time.time() / EXPIRY_PERIOD)
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expected = proxied_media_sig(expires, url)
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if now > expires or sig != expected:
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raise InvalidProxySignatureError("invalid or expired media")
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def proxied_media_url(url: str) -> str:
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if url.startswith(BASE_URL):
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return url
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expires = int(time.time() / EXPIRY_PERIOD) + EXPIRY_LENGTH
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sig = proxied_media_sig(expires, url)
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return (
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BASE_URL
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+ f"/proxy/media/{expires}/{sig}/"
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+ base64.urlsafe_b64encode(url.encode()).decode()
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)
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def resized_media_url(url: str, size: int) -> str:
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if size not in SUPPORTED_RESIZE:
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raise ValueError(f"Unsupported resize {size}")
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if url.startswith(BASE_URL):
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return url
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return proxied_media_url(url) + f"/{size}"
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