From ebe128ca73ce7d178a186b93684c8bf8577f3b80 Mon Sep 17 00:00:00 2001
From: jsing <>
Date: Sun, 25 Apr 2021 13:15:23 +0000
Subject: Clean up derivation of finished/peer finished.

Make this process more readable by having specific client/server functions,
calling the correct one based on s->server. This allows to remove various
SSL_ST_ACCEPT/SSL_ST_CONNECT checks, along with duplicate code.

ok inoguchi@ tb@
---
 src/lib/libssl/tls12_lib.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 92 insertions(+)
 create mode 100644 src/lib/libssl/tls12_lib.c

(limited to 'src/lib/libssl/tls12_lib.c')

diff --git a/src/lib/libssl/tls12_lib.c b/src/lib/libssl/tls12_lib.c
new file mode 100644
index 0000000000..520f41678d
--- /dev/null
+++ b/src/lib/libssl/tls12_lib.c
@@ -0,0 +1,92 @@
+/*	$OpenBSD: tls12_lib.c,v 1.1 2021/04/25 13:15:23 jsing Exp $ */
+/*
+ * Copyright (c) 2021 Joel Sing <jsing@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
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include "ssl_locl.h"
+
+static int
+tls12_finished_verify_data(SSL *s, const char *finished_label,
+    size_t finished_label_len, uint8_t *verify_data, size_t verify_data_len,
+    size_t *out_len)
+{
+	uint8_t transcript_hash[EVP_MAX_MD_SIZE];
+	size_t transcript_hash_len;
+
+	*out_len = 0;
+
+	if (verify_data_len < TLS1_FINISH_MAC_LENGTH)
+		return 0;
+
+	if (!tls1_transcript_hash_value(s, transcript_hash,
+	    sizeof(transcript_hash), &transcript_hash_len))
+		return 0;
+
+	if (!tls1_PRF(s, s->session->master_key, s->session->master_key_length,
+	    finished_label, finished_label_len, transcript_hash,
+	    transcript_hash_len, NULL, 0, NULL, 0, NULL, 0, verify_data,
+	    TLS1_FINISH_MAC_LENGTH))
+		return 0;
+
+	*out_len = TLS1_FINISH_MAC_LENGTH;
+
+	return 1;
+}
+
+static int
+tls12_client_finished_verify_data(SSL *s, uint8_t *verify_data,
+    size_t verify_data_len, size_t *out_len)
+{
+	return tls12_finished_verify_data(s, TLS_MD_CLIENT_FINISH_CONST,
+	    TLS_MD_CLIENT_FINISH_CONST_SIZE, verify_data, verify_data_len,
+	    out_len);
+}
+
+static int
+tls12_server_finished_verify_data(SSL *s, uint8_t *verify_data,
+    size_t verify_data_len, size_t *out_len)
+{
+	return tls12_finished_verify_data(s, TLS_MD_SERVER_FINISH_CONST,
+	    TLS_MD_SERVER_FINISH_CONST_SIZE, verify_data, verify_data_len,
+	    out_len);
+}
+
+int
+tls12_derive_finished(SSL *s)
+{
+	if (!s->server) {
+		return tls12_client_finished_verify_data(s,
+		    S3I(s)->hs.finished, sizeof(S3I(s)->hs.finished),
+		    &S3I(s)->hs.finished_len);
+	} else {
+		return tls12_server_finished_verify_data(s,
+		    S3I(s)->hs.finished, sizeof(S3I(s)->hs.finished),
+		    &S3I(s)->hs.finished_len);
+	}
+}
+
+int
+tls12_derive_peer_finished(SSL *s)
+{
+	if (s->server) {
+		return tls12_client_finished_verify_data(s,
+		    S3I(s)->hs.peer_finished, sizeof(S3I(s)->hs.peer_finished),
+		    &S3I(s)->hs.peer_finished_len);
+	} else {
+		return tls12_server_finished_verify_data(s,
+		    S3I(s)->hs.peer_finished, sizeof(S3I(s)->hs.peer_finished),
+		    &S3I(s)->hs.peer_finished_len);
+	}
+}
-- 
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