63 lines
1.7 KiB
Python
63 lines
1.7 KiB
Python
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"""Password hashing and constant-time secret hashing."""
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from __future__ import annotations
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import hashlib
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import hmac
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import secrets
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from argon2 import PasswordHasher
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from argon2.exceptions import VerifyMismatchError
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# Argon2id with moderate cost. `time_cost=2`, `memory_cost=64MiB`, `parallelism=2`
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# is well above OWASP minimums while staying snappy on a Debian small VM.
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_hasher = PasswordHasher(
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time_cost=2,
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memory_cost=64 * 1024,
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parallelism=2,
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hash_len=32,
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salt_len=16,
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)
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def hash_password(plaintext: str) -> str:
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return _hasher.hash(plaintext)
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def verify_password(stored_hash: str, plaintext: str) -> bool:
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"""Constant-time verification. Returns False on mismatch, never raises."""
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try:
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return _hasher.verify(stored_hash, plaintext)
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except VerifyMismatchError:
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return False
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except Exception: # corrupted hash or unsupported parameters
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return False
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def needs_rehash(stored_hash: str) -> bool:
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"""True when Argon2 parameters have evolved since the hash was created."""
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try:
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return _hasher.check_needs_rehash(stored_hash)
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except Exception:
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return True
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# === Opaque-token helpers (refresh tokens, invitation tokens) ===
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#
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# We never store the raw token in DB — only its SHA-256. Comparison uses
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# `hmac.compare_digest` to dodge timing attacks. Tokens are URL-safe base64.
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TOKEN_BYTES = 48 # 384 bits of entropy → 64 chars b64url
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def generate_opaque_token() -> str:
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return secrets.token_urlsafe(TOKEN_BYTES)
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def hash_opaque_token(token: str) -> str:
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return hashlib.sha256(token.encode("utf-8")).hexdigest()
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def verify_opaque_token(token: str, stored_hash: str) -> bool:
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return hmac.compare_digest(hash_opaque_token(token), stored_hash)
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