The functions SRP_Calc_client_key() and SRP_Calc_server_key() were
incorrectly returning a valid pointer in the event of error.
Issue reported by Yuan Jochen Kang
Reviewed-by: Richard Levitte <levitte@openssl.org>
(cherry picked from commit 308ff28673)
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.