RFC7250 handshakes with unauthenticated servers don't abort as expected

Issue summary: Clients using RFC7250 Raw Public Keys (RPKs) to authenticate a

server may fail to notice that the server was not authenticated, because

handshakes don't abort as expected when the SSL_VERIFY_PEER verification mode

is set.

Impact summary: TLS and DTLS connections using raw public keys may be

vulnerable to man-in-middle attacks when server authentication failure is not

detected by clients.

RPKs are disabled by default in both TLS clients and TLS servers. The issue

only arises when TLS clients explicitly enable RPK use by the server, and the

server, likewise, enables sending of an RPK instead of an X.509 certificate

chain. The affected clients are those that then rely on the handshake to

fail when the server's RPK fails to match one of the expected public keys,

by setting the verification mode to SSL_VERIFY_PEER.

Clients that enable server-side raw public keys can still find out that raw

public key verification failed by calling SSL_get_verify_result(), and those

that do, and take appropriate action, are not affected. This issue was

introduced in the initial implementation of RPK support in OpenSSL 3.2.

The FIPS modules in 3.4, 3.3, 3.2, 3.1 and 3.0 are not affected by this issue.