Wire up alert handling for TLSv1.3.

In TLSv1.3 there are two types of alerts "closure alerts" and
"error alerts". This makes the record layer more strict and handles closure
of the read and write channels. The callback then handles the record layer to
SSL mapping/behaviour.

ok tb@

1 files changed, 32 insertions, 2 deletions

diff --git a/src/lib/libssl/tls13_lib.c b/src/lib/libssl/tls13_lib.c
index 3860ddefef..f9505fa438 100644
--- a/src/lib/libssl/tls13_lib.c
+++ b/src/lib/libssl/tls13_lib.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: tls13_lib.c,v 1.3 2019/01/21 13:45:57 jsing Exp $ */
+/*      $OpenBSD: tls13_lib.c,v 1.4 2019/02/21 17:15:00 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  *
@@ -61,6 +61,35 @@ tls13_cipher_hash(const SSL_CIPHER *cipher)
         return NULL;
 }
 
+static void
+tls13_alert_received_cb(uint8_t alert_level, uint8_t alert_desc, void *arg)
+{
+        struct tls13_ctx *ctx = arg;
+        SSL *s = ctx->ssl;
+
+        if (alert_desc == SSL_AD_CLOSE_NOTIFY) {
+                ctx->ssl->internal->shutdown |= SSL_RECEIVED_SHUTDOWN;
+                S3I(ctx->ssl)->warn_alert = alert_desc;
+                return;
+        }
+
+        if (alert_desc == SSL_AD_USER_CANCELLED) {
+                /*
+                 * We treat this as advisory, since a close_notify alert
+                 * SHOULD follow this alert (RFC 8446 section 6.1).
+                 */
+                return;
+        }
+
+        /* All other alerts are treated as fatal in TLSv1.3. */
+        S3I(ctx->ssl)->fatal_alert = alert_desc;
+
+        SSLerror(ctx->ssl, SSL_AD_REASON_OFFSET + alert_desc);
+        ERR_asprintf_error_data("SSL alert number %d", alert_desc);
+
+        SSL_CTX_remove_session(s->ctx, s->session);
+}
+
 struct tls13_ctx *
 tls13_ctx_new(int mode)
 {
@@ -72,7 +101,8 @@ 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, NULL, NULL, ctx)) == NULL)
+            tls13_legacy_wire_write_cb, tls13_alert_received_cb, NULL,
+            ctx)) == NULL)
                 goto err;
 
         return ctx;