From d8eaa8b9e9911a0d3539917fb8134e3b19205a3e Mon Sep 17 00:00:00 2001
From: Adam Langley <agl@google.com>
Date: Thu, 23 Apr 2015 17:29:56 -0700
Subject: Use SSL_MODE_SEND_FALLBACK_SCSV.

Upstream settled in this API, and it's also the one that we expect
internally and that third_party code will expect.

This is an import of upstream's
5f0efe06e199a1bd96f161eb45f3dd76924cdc2a.

Change-Id: Ib4c7054a382dccdd23919407742bd037b9653a4b
---
 src/include/openssl/ssl.h | 22 +++++++++++++---------
 src/ssl/s3_lib.c          |  5 -----
 src/ssl/ssl_lib.c         |  2 +-
 3 files changed, 14 insertions(+), 15 deletions(-)

(limited to 'src')

diff --git a/src/include/openssl/ssl.h b/src/include/openssl/ssl.h
index eb8cad0..ef73c8d 100644
--- a/src/include/openssl/ssl.h
+++ b/src/include/openssl/ssl.h
@@ -482,6 +482,16 @@ struct ssl_session_st {
  * session resumption is used for a given SSL*. */
 #define SSL_MODE_NO_SESSION_CREATION 0x00000200L
 
+/* SSL_MODE_SEND_SERVERHELLO_TIME sends TLS_FALLBACK_SCSV in the ClientHello.
+ * To be set only by applications that reconnect with a downgraded protocol
+ * version; see https://tools.ietf.org/html/draft-ietf-tls-downgrade-scsv-05
+ * for details.
+ *
+ * DO NOT ENABLE THIS if your application attempts a normal handshake. Only use
+ * this in explicit fallback retries, following the guidance in
+ * draft-ietf-tls-downgrade-scsv-05. */
+#define SSL_MODE_SEND_FALLBACK_SCSV 0x00000400L
+
 /* Note: SSL[_CTX]_set_{options,mode} use |= op on the previous value, they
  * cannot be used to clear bits. */
 
@@ -1313,10 +1323,6 @@ struct ssl_st {
                     * 2 if we are a server and are inside a handshake
                     * (i.e. not just sending a HelloRequest) */
 
-  /* fallback_scsv is non-zero iff we are sending the TLS_FALLBACK_SCSV cipher
-   * suite value. Only applies to a client. */
-  char fallback_scsv;
-
   /* fastradio_padding, if true, causes ClientHellos to be padded to 1024
    * bytes. This ensures that the cellular radio is fast forwarded to DCH (high
    * data rate) state in 3G networks. */
@@ -1597,8 +1603,9 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 #define SSL_CTRL_GET_CHANNEL_ID 118
 #define SSL_CTRL_SET_CHANNEL_ID 119
 
-#define SSL_CTRL_FALLBACK_SCSV 120
-
+/* DTLSv1_get_timeout queries the next DTLS handshake timeout. If there is a
+ * timeout in progress, it sets |*((OPENSSL_timeval*)arg)| to the time remaining
+ * and returns one. Otherwise, it returns zero. */
 #define DTLSv1_get_timeout(ssl, arg) \
   SSL_ctrl(ssl, DTLS_CTRL_GET_TIMEOUT, 0, (void *)arg)
 #define DTLSv1_handle_timeout(ssl) \
@@ -1757,9 +1764,6 @@ DECLARE_PEM_rw(SSL_SESSION, SSL_SESSION)
 #define SSL_get0_ec_point_formats(s, plst) \
   SSL_ctrl(s, SSL_CTRL_GET_EC_POINT_FORMATS, 0, (char *)plst)
 
-#define SSL_enable_fallback_scsv(s) \
-  SSL_ctrl(s, SSL_CTRL_FALLBACK_SCSV, 0, NULL)
-
 OPENSSL_EXPORT int SSL_CTX_set_cipher_list(SSL_CTX *, const char *str);
 OPENSSL_EXPORT int SSL_CTX_set_cipher_list_tls11(SSL_CTX *, const char *str);
 OPENSSL_EXPORT SSL_CTX *SSL_CTX_new(const SSL_METHOD *meth);
diff --git a/src/ssl/s3_lib.c b/src/ssl/s3_lib.c
index 9782296..d33a4c2 100644
--- a/src/ssl/s3_lib.c
+++ b/src/ssl/s3_lib.c
@@ -967,11 +967,6 @@ long ssl3_ctrl(SSL *s, int cmd, long larg, void *parg) {
       memcpy(parg, s->s3->tlsext_channel_id, larg < 64 ? larg : 64);
       return 64;
 
-    case SSL_CTRL_FALLBACK_SCSV:
-      s->fallback_scsv = 1;
-      ret = 1;
-      break;
-
     default:
       break;
   }
diff --git a/src/ssl/ssl_lib.c b/src/ssl/ssl_lib.c
index c3b95d5..35eb1ec 100644
--- a/src/ssl/ssl_lib.c
+++ b/src/ssl/ssl_lib.c
@@ -1425,7 +1425,7 @@ int ssl_cipher_list_to_bytes(SSL *s, STACK_OF(SSL_CIPHER) *sk, uint8_t *p) {
     s2n(SSL3_CK_SCSV & 0xffff, p);
   }
 
-  if (s->fallback_scsv) {
+  if (s->mode & SSL_MODE_SEND_FALLBACK_SCSV) {
     s2n(SSL3_CK_FALLBACK_SCSV & 0xffff, p);
   }
 
-- 
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