78 lines
3.0 KiB
Python
78 lines
3.0 KiB
Python
"""A secret handed over by link, encrypted before it ever reaches here.
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NOT AN ASSET, so this is a standalone table rather than an extension keyed by
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assetid: a shared credential is an event with a short life, not a thing the site
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owns and inventories.
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WHAT THIS TABLE CAN AND CANNOT SEE. The AES key lives in the URL fragment, which
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browsers never send to a server, so what is stored is ciphertext and an IV and
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nothing else. Compromising this table yields no secrets. It also means the
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server cannot inspect what it is holding - which is the right trade for a
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credential, and the reason the SIZE limit in the routes carries the whole weight
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of "this is not a document transfer".
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"""
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from datetime import datetime, timezone
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from shopdb.api import db, BaseModel
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def _utcnow():
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return datetime.now(timezone.utc).replace(tzinfo=None)
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class SecureSecret(BaseModel):
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"""One shared secret: opaque id, ciphertext, and the rules for its life."""
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__tablename__ = 'securesendsecrets'
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secretid = db.Column(db.Integer, primary_key=True)
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# The unguessable half of the link. With no login on the read side this IS
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# the credential, so it is 128 bits of randomness rendered as hex - never a
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# sequence, which would be enumerable by anyone who received one link.
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token = db.Column(db.String(64), unique=True, nullable=False, index=True)
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# Base64 of the AES-GCM ciphertext, and the IV it was sealed with. Opaque
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# here by design.
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ciphertext = db.Column(db.Text, nullable=False)
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iv = db.Column(db.String(64), nullable=False)
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# Both limits apply, whichever comes first.
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expiresat = db.Column(db.DateTime, nullable=False, index=True)
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viewsremaining = db.Column(db.Integer, nullable=False, default=1)
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# Who created it. The reader is anonymous by design, so this is the only
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# person the row can name - and the reason creation requires a login.
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createdbyuserid = db.Column(
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db.Integer,
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db.ForeignKey('users.userid', ondelete='SET NULL'),
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nullable=True,
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index=True,
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)
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# Recorded for the audit trail; the content of what was read is not
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# recoverable, but that it was read, and when, is.
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lastviewedat = db.Column(db.DateTime, nullable=True)
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viewcount = db.Column(db.Integer, nullable=False, default=0)
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def is_expired(self, now=None):
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return (now or _utcnow()) >= self.expiresat
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def is_spent(self):
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return self.viewsremaining <= 0
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def to_dict(self):
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"""NEVER includes the ciphertext.
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This is the shape the CREATOR sees back - a receipt. Handing the payload
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back on create would put the secret in a second place for no reason.
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"""
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return {
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'token': self.token,
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'expiresat': self.expiresat.isoformat() if self.expiresat else None,
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'viewsremaining': self.viewsremaining,
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'viewcount': self.viewcount,
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'createddate': self.createddate.isoformat() if self.createddate else None,
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}
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