irmd: Specify peer authentication contract

OAP accepted requests and responses without a certificate even when
the peer was expected to authenticate. An on-path attacker could
strip the certificate and signature from a flow allocation response
and substitute its own key exchange, silently downgrading the
handshake to unauthenticated.

Add an auth=required|optional policy to enc.conf, enforced per role: a
client config requires the server to present a valid certificate, a
server config requires the same from the client. Default is required
for client side (https), optional server side. The client side default
can be changed via OAP_CLIENT_AUTH_DEFAULT for testing.

Replace the bare 'none' keyword with encryption=none, which disables
encryption only: the digest and the authentication policy are kept, so
authenticated but unencrypted flows can be configured. Configs using
bare 'none' are now rejected.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 11 insertions, 0 deletions

diff --git a/src/irmd/oap/cli.c b/src/irmd/oap/cli.c
index 7a202da7..d38f38dd 100644
--- a/src/irmd/oap/cli.c
+++ b/src/irmd/oap/cli.c
@@ -93,6 +93,11 @@ int load_cli_kex_config(const struct name_info * info,
         assert(info != NULL);
         assert(cfg != NULL);
 
+        memset(cfg, 0, sizeof(*cfg));
+
+        /* A client authenticates the server by default, like an https client */
+        cfg->req_auth = OAP_CLIENT_AUTH_DEFAULT;
+
         return load_kex_config(info->name, info->c.enc, cfg);
 }
 
@@ -534,6 +539,12 @@ int oap_cli_complete(void *                   ctx,
                 goto fail_oap;
         }
 
+        /* Required peer auth makes sig and name binding mandatory */
+        if (s->kcfg.req_auth && peer_hdr.crt.len == 0) {
+                log_err_id(id, "Server did not provide a certificate.");
+                goto fail_oap;
+        }
+
         /* Verify request hash in authenticated response */
         if (peer_hdr.req_hash.len == 0) {
                 log_err_id(id, "Response missing req_hash.");