Invalid parameters passed to the SRP code can be overrun an internal
buffer. Add sanity check that g, A, B < N to SRP code.
Thanks to Sean Devlin and Watson Ladd of Cryptography Services, NCC
Group for reporting this issue.
Reviewed-by: Kurt Roeckx <kurt@openssl.org>
PR: 3165
Submitted by: Daniel Richard G.
(cherry picked from commit 2df9ec01d563f9cc2deab07e8c3391059d476592)
(cherry picked from commit 0de70011adf6952e3b975d1a8a383879b64f3b77)