SEP-10: apply grace period to minTime constraint

[JakeUrban]

SEP-10: Apply grace period to minTime constraint

It is possible that the client machine's clock is behind the SEP-10 server machine's clock.

If this is the case, client applications calling readChallengeTx() may not be able to validate the challenge due to the challenge transaction's minimum timebound being greater than the client machine's current time.

Changes

readChallengeTx() or the equivalent function

• Apply a 5-minute grace period to the minibum timebound check
  • i.e. the minimum timebound should be permitted to be at most 5 minutes in the future from the client machine's current time

Implementations

Both the JS and Go SDKs have been updated with these changes.

• stellar/js-stellar-sdk#667
  • The JS SDK also applied the grace period to the maximum timebound, but the minimum timebound is the more important constraint to relax.
• stellar/go#3824

[JakeUrban]

stellar/stellar-protocol#1057