ssl_verify_client_cert=yes does not require a client certificate

[Hristo Venev]

Hello,

I am trying to set up LMTP over TLS. I have set ssl_verify_client_cert:

protocol lmtp {   
        ssl_ca = </etc/cert/mail/ca.pem
        ssl_cert = </etc/cert/mail/host.pem
        ssl_key = </etc/cert/mail/host.key
        ssl_verify_client_cert = yes
}

However, clients can still connect without presenting a valid
certificate.

In openssl_iostream_set() the flags given to SSL_set_verify() are
SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE. For a certificate to be
required, the SSL_VERIFY_FAIL_IF_NO_PEER_CERT flag also needs to be
set:

diff --git a/src/lib-ssl-iostream/iostream-openssl.c b/src/lib-ssl-iostream/iostream-openssl.c
index 5d11526f1..d8df96398 100644
--- a/src/lib-ssl-iostream/iostream-openssl.c
+++ b/src/lib-ssl-iostream/iostream-openssl.c
@@ -235,7 +235,7 @@ openssl_iostream_set(struct ssl_iostream *ssl_io,
 		if (ssl_io->ctx->client_ctx)
 			verify_flags = SSL_VERIFY_NONE;
 		else
-			verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE;
+			verify_flags = SSL_VERIFY_PEER | SSL_VERIFY_CLIENT_ONCE | SSL_VERIFY_FAIL_IF_NO_PEER_CERT;
 		SSL_set_verify(ssl_io->ssl, verify_flags,
 			       openssl_iostream_verify_client_cert);
 	}

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