Clarify negative return from X509_verify_cert()

OpenSSL internally for certificate validation, in both the S/MIME and

OpenSSL internally for certificate validation, in both the S/MIME and

SSL/TLS code.

SSL/TLS code.

The negative return value from X509_verify_cert() can only occur if no

A negative return value from X509_verify_cert() can occur if it is invoked

certificate is set in B<ctx> (due to a programming error); if X509_verify_cert()

incurrectly, such as with no certificate set in B<ctx>, or when it is called

twice without reinitialising B<ctx> in between; or if a retry

twice in succession without reinitialising B<ctx> for the second call.

operation is requested during internal lookups (which never happens with

A negative return value can also happen due to internal resource problems or if

standard lookup methods). It is however recommended that application check

a retry operation is requested during internal lookups (which never happens

for <= 0 return value on error.

with standard lookup methods).

Applications must check for <= 0 return value on error.

=head1 BUGS

=head1 BUGS