[tor-dev] About the key derivation algorithm used in the Control Port password authentication

[techmetx11 via tor-dev <tor-dev@xxxxxxxxxxxxxxxxxxxx>]

Although several parts of Tor have been redesigned and upgraded over
many years, the algorithm for the HashedControlPassword still remained
the same.

It still uses SHA-1 as the basis of the OpenPGP S2K algorithm, despite
the fact that the algorithm has long-since been obsolete by newer and
better hashing algorithms (on top of it, has had some practical
collision attacks[1]).

This is made worse by the fact that the S2K algorithm is not iterative
(in the sense of recursive hashing), but rather repeats the
salt+password many times in the hash digest until it reaches a certain
amount of bytes. Theoretically, an attacker can expose this to
autheticate into a Tor Control Port without having to know the password.

Are there any plans to revamp the algorithm for newer Tor versions?

[1]: https://shattered.io/
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