Missing key validations

[Jean-Philippe Aumasson]

Here the answer is yes :)

sphinx/src/crypto/keys.rs

Line 114 in b168f70

 // TODO: do we have to clamp it here? 

And here too:

sphinx/src/crypto/keys.rs

Lines 104 to 110 in b168f70

 impl From<Scalar> for EphemeralSecret { 
     fn from(scalar: Scalar) -> EphemeralSecret { 
         // TODO: should we ensure it's a valid scalar by performing 
         // montgomery reduction and/or clamping? 
         PrivateKey(scalar) 
     } 
 } 

This is because there is no guarantee that the received bytes or scalar are valid ones wrt Curve25519.

Also, public keys must be validated when instantiated, that is, From<[u8; PUBLIC_KEY_SIZE]> should verify that the point is not the point at infinity