Handle finished messages in TLSv1.3 client.

This adds support for processing of the server finished message and
generation of the client finished message.

ok tb@

2 files changed, 131 insertions, 14 deletions

diff --git a/src/lib/libssl/tls13_client.c b/src/lib/libssl/tls13_client.c
index d15ab65105..b3209c063c 100644
--- a/src/lib/libssl/tls13_client.c
+++ b/src/lib/libssl/tls13_client.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: tls13_client.c,v 1.6 2019/02/11 17:48:15 jsing Exp $ */
+/* $OpenBSD: tls13_client.c,v 1.7 2019/02/13 16:28:28 jsing Exp $ */
 /*
  * Copyright (c) 2018, 2019 Joel Sing <jsing@openbsd.org>
  *
@@ -555,3 +555,132 @@ tls13_server_certificate_verify_recv(struct tls13_ctx *ctx)
 
         return ret;
 }
+
+int
+tls13_server_finished_recv(struct tls13_ctx *ctx)
+{
+        struct tls13_secrets *secrets = ctx->hs->secrets;
+        struct tls13_secret context = { .data = "", .len = 0 };
+        struct tls13_secret finished_key;
+        uint8_t transcript_hash[EVP_MAX_MD_SIZE];
+        size_t transcript_hash_len;
+        uint8_t *verify_data = NULL;
+        size_t verify_data_len;
+        uint8_t key[EVP_MAX_MD_SIZE];
+        HMAC_CTX *hmac_ctx = NULL;
+        unsigned int hlen;
+        int ret = 0;
+        CBS cbs;
+
+        if (!tls13_handshake_msg_content(ctx->hs_msg, &cbs))
+                goto err;
+
+        /*
+         * Verify server finished.
+         */
+        finished_key.data = key;
+        finished_key.len = EVP_MD_size(ctx->hash);
+
+        if (!tls13_hkdf_expand_label(&finished_key, ctx->hash,
+            &secrets->server_handshake_traffic, "finished",
+            &context))
+                goto err;
+
+        if ((hmac_ctx = HMAC_CTX_new()) == NULL)
+                goto err;
+        if (!HMAC_Init_ex(hmac_ctx, finished_key.data, finished_key.len,
+            ctx->hash, NULL))
+                goto err;
+        if (!HMAC_Update(hmac_ctx, ctx->hs->transcript_hash,
+            ctx->hs->transcript_hash_len))
+                goto err;
+        verify_data_len = HMAC_size(hmac_ctx);
+        if ((verify_data = calloc(1, verify_data_len)) == NULL)
+                goto err;
+        if (!HMAC_Final(hmac_ctx, verify_data, &hlen))
+                goto err;
+        if (hlen != verify_data_len)
+                goto err;
+
+        if (!CBS_mem_equal(&cbs, verify_data, verify_data_len)) {
+                /* XXX - send alert. */
+                goto err;
+        }
+
+        /*
+         * Derive application traffic keys.
+         */
+        if (!tls1_transcript_hash_value(ctx->ssl, transcript_hash,
+            sizeof(transcript_hash), &transcript_hash_len))
+                goto err;
+
+        context.data = transcript_hash;
+        context.len = transcript_hash_len;
+
+        if (!tls13_derive_application_secrets(secrets, &context))
+                return TLS13_IO_FAILURE;
+
+        ret = 1;
+
+ err:
+        HMAC_CTX_free(hmac_ctx);
+        free(verify_data);
+
+        return ret;
+}
+
+int
+tls13_client_finished_send(struct tls13_ctx *ctx)
+{
+        struct tls13_secrets *secrets = ctx->hs->secrets;
+        struct tls13_secret context = { .data = "", .len = 0 };
+        struct tls13_secret finished_key;
+        uint8_t transcript_hash[EVP_MAX_MD_SIZE];
+        size_t transcript_hash_len;
+        uint8_t key[EVP_MAX_MD_SIZE];
+        uint8_t *verify_data;
+        size_t hmac_len;
+        unsigned int hlen;
+        HMAC_CTX *hmac_ctx = NULL;
+        int ret = 0;
+        CBB body;
+
+        finished_key.data = key;
+        finished_key.len = EVP_MD_size(ctx->hash);
+
+        if (!tls13_hkdf_expand_label(&finished_key, ctx->hash,
+            &secrets->client_handshake_traffic, "finished",
+            &context))
+                goto err;
+
+        if (!tls1_transcript_hash_value(ctx->ssl, transcript_hash,
+            sizeof(transcript_hash), &transcript_hash_len))
+                goto err;
+
+        if ((hmac_ctx = HMAC_CTX_new()) == NULL)
+                goto err;
+        if (!HMAC_Init_ex(hmac_ctx, finished_key.data, finished_key.len,
+            ctx->hash, NULL))
+                goto err;
+        if (!HMAC_Update(hmac_ctx, transcript_hash, transcript_hash_len))
+                goto err;
+
+        if (!tls13_handshake_msg_start(ctx->hs_msg, &body, TLS13_MT_FINISHED))
+                goto err;
+        hmac_len = HMAC_size(hmac_ctx);
+        if (!CBB_add_space(&body, &verify_data, hmac_len))
+                goto err;
+        if (!HMAC_Final(hmac_ctx, verify_data, &hlen))
+                goto err;
+        if (hlen != hmac_len)
+                goto err;
+        if (!tls13_handshake_msg_finish(ctx->hs_msg))
+                goto err;
+
+        ret = 1;
+
+ err:
+        HMAC_CTX_free(hmac_ctx);
+
+        return ret;
+}
diff --git a/src/lib/libssl/tls13_handshake.c b/src/lib/libssl/tls13_handshake.c
index 3ebf1e9d73..630f81a8a8 100644
--- a/src/lib/libssl/tls13_handshake.c
+++ b/src/lib/libssl/tls13_handshake.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: tls13_handshake.c,v 1.26 2019/02/11 17:48:15 jsing Exp $      */
+/*      $OpenBSD: tls13_handshake.c,v 1.27 2019/02/13 16:28:28 jsing Exp $      */
 /*
  * Copyright (c) 2018-2019 Theo Buehler <tb@openbsd.org>
  * Copyright (c) 2019 Joel Sing <jsing@openbsd.org>
@@ -459,12 +459,6 @@ tls13_client_finished_recv(struct tls13_ctx *ctx)
 }
 
 int
-tls13_client_finished_send(struct tls13_ctx *ctx)
-{
-        return 0;
-}
-
-int
 tls13_client_key_update_send(struct tls13_ctx *ctx)
 {
         return 0;
@@ -509,12 +503,6 @@ tls13_server_certificate_verify_send(struct tls13_ctx *ctx)
 }
 
 int
-tls13_server_finished_recv(struct tls13_ctx *ctx)
-{
-        return 0;
-}
-
-int
 tls13_server_finished_send(struct tls13_ctx *ctx)
 {
         return 0;