Policy-based security certificate filtering

Policy filtering services are built into security processing of an execution environment for resolving how to handle a digital security certificate of a communicating entity without requiring a local copy of a root certificate that is associated with the entity through a certificate authority ("CA") chain. Policy may be specified using a set of rules (or other policy format) indicating conditions for certificate filtering. This filtering is preferably invoked during handshaking, upon determining that a needed root CA certificate is not available. In one approach, the policy uses rules specifying conditions under which a certificate is permitted (i.e., treated as if it is validated) and other rules specifying conditions under which a certificate is blocked (i.e., treated as if it is invalid). Preferably, policy rules are evaluated and enforced in order of most-specific to least-specific.