Add support for TLS 1.3 post handshake messages and key updating.

tested against openssl 1.1's server.

ok jsing@ tb@

1 files changed, 147 insertions, 3 deletions

diff --git a/src/lib/libssl/tls13_lib.c b/src/lib/libssl/tls13_lib.c
index 61ca3d4682..6876528f50 100644
--- a/src/lib/libssl/tls13_lib.c
+++ b/src/lib/libssl/tls13_lib.c
@@ -1,6 +1,7 @@
-/*      $OpenBSD: tls13_lib.c,v 1.12 2019/11/17 00:10:47 beck Exp $ */
+/*      $OpenBSD: tls13_lib.c,v 1.13 2019/11/26 23:46:18 beck Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
+ * Copyright (c) 2019 Bob Beck <beck@openbsd.org>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -90,6 +91,149 @@ tls13_alert_received_cb(uint8_t alert_desc, void *arg)
         SSL_CTX_remove_session(s->ctx, s->session);
 }
 
+static int
+tls13_phh_update_local_traffic_secret(struct tls13_ctx *ctx)
+{
+        struct tls13_secrets *secrets = ctx->hs->secrets;
+
+        if (ctx->mode == TLS13_HS_CLIENT)
+                return (tls13_update_client_traffic_secret(secrets) &&
+                    tls13_record_layer_set_write_traffic_key(ctx->rl,
+                        &secrets->client_application_traffic));
+        return (tls13_update_server_traffic_secret(secrets) &&
+            tls13_record_layer_set_read_traffic_key(ctx->rl,
+            &secrets->server_application_traffic));
+}
+
+static int
+tls13_phh_update_peer_traffic_secret(struct tls13_ctx *ctx)
+{
+        struct tls13_secrets *secrets = ctx->hs->secrets;
+
+        if (ctx->mode == TLS13_HS_CLIENT)
+                return (tls13_update_server_traffic_secret(secrets) &&
+                    tls13_record_layer_set_read_traffic_key(ctx->rl,
+                    &secrets->server_application_traffic));
+        return (tls13_update_client_traffic_secret(secrets) &&
+            tls13_record_layer_set_write_traffic_key(ctx->rl,
+            &secrets->client_application_traffic));
+}
+
+/*
+ * XXX arbitrarily chosen limit of 100 post handshake handshake
+ * messages in an hour - to avoid a hostile peer from constantly
+ * requesting certificates or key renegotiaitons, etc.
+ */
+static int
+tls13_phh_limit_check(struct tls13_ctx *ctx)
+{
+        time_t now = time(NULL);
+
+        if (ctx->phh_last_seen > now - TLS13_PHH_LIMIT_TIME) {
+                if (ctx->phh_count > TLS13_PHH_LIMIT)
+                        return 0;
+        } else
+                ctx->phh_count = 0;
+        ctx->phh_count++;
+        ctx->phh_last_seen = now;
+        return 1;
+}
+
+static ssize_t
+tls13_key_update_recv(struct tls13_ctx *ctx, CBS *cbs)
+{
+        ssize_t ret = TLS13_IO_FAILURE;
+
+        if (!CBS_get_u8(cbs, &ctx->key_update_request))
+                goto err;
+        if (CBS_len(cbs) != 0)
+                goto err;
+
+        if (!tls13_phh_update_peer_traffic_secret(ctx))
+                goto err;
+
+        if (ctx->key_update_request) {
+                CBB cbb;
+                CBS cbs; /* XXX */
+
+                free(ctx->hs_msg);
+                ctx->hs_msg = tls13_handshake_msg_new();
+                if (!tls13_handshake_msg_start(ctx->hs_msg, &cbb, TLS13_MT_KEY_UPDATE))
+                        goto err;
+                if (!CBB_add_u8(&cbb, 0))
+                        goto err;
+                if (!tls13_handshake_msg_finish(ctx->hs_msg))
+                        goto err;
+                tls13_handshake_msg_data(ctx->hs_msg, &cbs);
+                ret = tls13_record_layer_phh(ctx->rl, &cbs);
+
+                tls13_handshake_msg_free(ctx->hs_msg);
+                ctx->hs_msg = NULL;
+        } else
+                ret = TLS13_IO_SUCCESS;
+
+        return ret;
+ err:
+        ctx->key_update_request = 0;
+        /* XXX alert */
+        return TLS13_IO_FAILURE;
+}
+
+static void
+tls13_phh_done_cb(void *cb_arg)
+{
+        struct tls13_ctx *ctx = cb_arg;
+
+        if (ctx->key_update_request) {
+                tls13_phh_update_local_traffic_secret(ctx);
+                ctx->key_update_request = 0;
+        }
+}
+
+static ssize_t
+tls13_phh_received_cb(void *cb_arg, CBS *cbs)
+{
+        ssize_t ret = TLS13_IO_FAILURE;
+        struct tls13_ctx *ctx = cb_arg;
+        CBS phh_cbs;
+
+        if (!tls13_phh_limit_check(ctx))
+                return tls13_send_alert(ctx->rl, SSL3_AD_UNEXPECTED_MESSAGE);
+
+        if ((ctx->hs_msg == NULL) &&
+            ((ctx->hs_msg = tls13_handshake_msg_new()) == NULL))
+                return TLS13_IO_FAILURE;
+
+        if (!tls13_handshake_msg_set_buffer(ctx->hs_msg, cbs))
+                return TLS13_IO_FAILURE;
+
+        if ((ret = tls13_handshake_msg_recv(ctx->hs_msg, ctx->rl))
+            != TLS13_IO_SUCCESS)
+                return ret;
+
+        if (!tls13_handshake_msg_content(ctx->hs_msg, &phh_cbs))
+                return TLS13_IO_FAILURE;
+
+        switch(tls13_handshake_msg_type(ctx->hs_msg)) {
+        case TLS13_MT_KEY_UPDATE:
+                ret = tls13_key_update_recv(ctx, &phh_cbs);
+                break;
+        case TLS13_MT_NEW_SESSION_TICKET:
+                /* XXX do nothing for now and ignore this */
+                break;
+        case TLS13_MT_CERTIFICATE_REQUEST:
+                /* XXX add support if we choose to advertise this */
+                /* FALLTHROUGH */
+        default:
+                ret = TLS13_IO_FAILURE; /* XXX send alert */
+                break;
+        }
+
+        tls13_handshake_msg_free(ctx->hs_msg);
+        ctx->hs_msg = NULL;
+        return ret;
+}
+
 struct tls13_ctx *
 tls13_ctx_new(int mode)
 {
@@ -101,8 +245,8 @@ tls13_ctx_new(int mode)
         ctx->mode = mode;
 
         if ((ctx->rl = tls13_record_layer_new(tls13_legacy_wire_read_cb,
-            tls13_legacy_wire_write_cb, tls13_alert_received_cb, NULL, NULL,
-            ctx)) == NULL)
+            tls13_legacy_wire_write_cb, tls13_alert_received_cb,
+            tls13_phh_received_cb, tls13_phh_done_cb, ctx)) == NULL)
                 goto err;
 
         return ctx;