Stake handler must truncate decimal input

[rigelrozanski]

To ensure that a transaction can't pass in huge rational values (and cause slow math, generally slowing down the blockchain) we must truncate the decimal-string value which comes in with transactions to the stake handler

[ValarDragon]

Do we want this to be true for all modules, or just staking. (I.e. should we alter NewRatFromDecimal, or wherever its called in staking)

Also what precision would be reasonable, 5 values after the decimal point?

[rigelrozanski]

Yeah I mean this is only really used when parsing input from the CLI or from LCD - I think we can add a new input to the function NewRatFromDecimal which specifies the number of decimal places. this way the module/application can define what it wants - we probably will define one integer object (probably set to 8) which should be used for displaying the shares as well as parsing the input - for ethermint this will probably be greater

[ValarDragon]

Cool! I'll write a PR for this once unbonding is merged.

[ValarDragon]

Wait fixing the UI layer doesn't prevent txs with large rationals from verifying. (Since txs could be sent w/o going through the UI) Should size of the rationals also be enforced in the handler, and if so, how should that be done?

[ValarDragon]

I think this should additionally checked in validate basic for MsgBeginUnbonding and MsgBeginRedelegate. (UI layer should also be fixed, so that it always generates valid txs) I think the better way to specify this however is to ensure that the numerator and denominator both are less than a certain precision. (I'd suggest 32 bits), and for the ui layer, use the previously described truncation method. If this sounds good, I'll go ahead and implement it.