implement HKDF and HKDFExpand derive_into #13643
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alex
reviewed
Oct 11, 2025
alex
reviewed
Oct 11, 2025
| :raises ValueError: This exception is raised if the buffer is too small | ||
| for the derived key. | ||
| :raises cryptography.exceptions.AlreadyFinalized: This is raised when | ||
| :meth:`derive_into` |
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Hmm, its really when any combination of the two methods is called more than once.
| :raises ValueError: This exception is raised if the buffer is too small | ||
| for the derived key. | ||
| :raises cryptography.exceptions.AlreadyFinalized: This is raised when | ||
| :meth:`derive_into` |
| )); | ||
| } | ||
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| let prk = self._extract(py, key_material)?; |
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Does it undermind the point at all that we still end up with the prk in some buffer that the caller doesn't control?
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Sort of? It's not ideal. We could require that the buffer provided be >= underlying HMAC output size, but wow that sounds confusing.
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If we decide we like this we can implement it for every KDF. refs #13245