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@

1 files changed, 25 insertions, 52 deletions

diff --git a/src/lib/libssl/ssl_both.c b/src/lib/libssl/ssl_both.c
index ad9b0ee257..fe04f809b0 100644
--- a/src/lib/libssl/ssl_both.c
+++ b/src/lib/libssl/ssl_both.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssl_both.c,v 1.28 2021/04/19 16:51:56 jsing Exp $ */
+/* $OpenBSD: ssl_both.c,v 1.29 2021/04/25 13:15:22 jsing Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -164,42 +164,39 @@ ssl3_do_write(SSL *s, int type)
 }
 
 int
-ssl3_send_finished(SSL *s, int a, int b, const char *sender, int slen)
+ssl3_send_finished(SSL *s, int state_a, int state_b)
 {
         CBB cbb, finished;
-        int md_len;
 
         memset(&cbb, 0, sizeof(cbb));
 
-        if (S3I(s)->hs.state == a) {
-                md_len = TLS1_FINISH_MAC_LENGTH;
-                OPENSSL_assert(md_len <= EVP_MAX_MD_SIZE);
-
-                if (tls1_final_finish_mac(s, sender, slen,
-                    S3I(s)->hs.finished) != md_len)
-                        return (0);
-                S3I(s)->hs.finished_len = md_len;
+        if (S3I(s)->hs.state == state_a) {
+                if (!tls12_derive_finished(s))
+                        goto err;
 
                 /* Copy finished so we can use it for renegotiation checks. */
                 if (!s->server) {
                         memcpy(S3I(s)->previous_client_finished,
-                            S3I(s)->hs.finished, md_len);
-                        S3I(s)->previous_client_finished_len = md_len;
+                            S3I(s)->hs.finished, S3I(s)->hs.finished_len);
+                        S3I(s)->previous_client_finished_len =
+                            S3I(s)->hs.finished_len;
                 } else {
                         memcpy(S3I(s)->previous_server_finished,
-                            S3I(s)->hs.finished, md_len);
-                        S3I(s)->previous_server_finished_len = md_len;
+                            S3I(s)->hs.finished, S3I(s)->hs.finished_len);
+                        S3I(s)->previous_server_finished_len =
+                            S3I(s)->hs.finished_len;
                 }
 
                 if (!ssl3_handshake_msg_start(s, &cbb, &finished,
                     SSL3_MT_FINISHED))
                         goto err;
-                if (!CBB_add_bytes(&finished, S3I(s)->hs.finished, md_len))
+                if (!CBB_add_bytes(&finished, S3I(s)->hs.finished,
+                    S3I(s)->hs.finished_len))
                         goto err;
                 if (!ssl3_handshake_msg_finish(s, &cbb))
                         goto err;
 
-                S3I(s)->hs.state = b;
+                S3I(s)->hs.state = state_b;
         }
 
         return (ssl3_handshake_write(s));
@@ -210,36 +207,6 @@ ssl3_send_finished(SSL *s, int a, int b, const char *sender, int slen)
         return (-1);
 }
 
-/*
- * ssl3_take_mac calculates the Finished MAC for the handshakes messages seen
- * so far.
- */
-static void
-ssl3_take_mac(SSL *s)
-{
-        const char *sender;
-        int slen;
-
-        /*
-         * If no new cipher setup return immediately: other functions will
-         * set the appropriate error.
-         */
-        if (S3I(s)->hs.cipher == NULL)
-                return;
-
-        if (S3I(s)->hs.state & SSL_ST_CONNECT) {
-                sender = TLS_MD_SERVER_FINISH_CONST;
-                slen = TLS_MD_SERVER_FINISH_CONST_SIZE;
-        } else {
-                sender = TLS_MD_CLIENT_FINISH_CONST;
-                slen = TLS_MD_CLIENT_FINISH_CONST_SIZE;
-        }
-
-        S3I(s)->hs.peer_finished_len =
-            tls1_final_finish_mac(s, sender, slen,
-                S3I(s)->hs.peer_finished);
-}
-
 int
 ssl3_get_finished(SSL *s, int a, int b)
 {
@@ -544,10 +511,16 @@ ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
                 n -= i;
         }
 
-        /* If receiving Finished, record MAC of prior handshake messages for
-         * Finished verification. */
-        if (*s->internal->init_buf->data == SSL3_MT_FINISHED)
-                ssl3_take_mac(s);
+        /*
+         * If receiving Finished, record MAC of prior handshake messages for
+         * Finished verification.
+         */
+        if (*s->internal->init_buf->data == SSL3_MT_FINISHED) {
+                if (S3I(s)->hs.cipher != NULL) {
+                        if (!tls12_derive_peer_finished(s))
+                                goto err;
+                }
+        }
 
         /* Feed this message into MAC computation. */
         if (s->internal->mac_packet) {
@@ -566,7 +539,7 @@ ssl3_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok)
 
  fatal_err:
         ssl3_send_alert(s, SSL3_AL_FATAL, al);
-err:
+ err:
         *ok = 0;
         return (-1);
 }