Option to disable padding extension.

Add TLS padding extension to SSL_OP_ALL so it is used with other
"bugs" options and can be turned off.

This replaces SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG which is an ancient
option referring to SSLv2 and SSLREF.

PR#3336

doc/ssl/SSL_CTX_set_options.pod

@@ -112,6 +112,12 @@ vulnerability affecting CBC ciphers, which cannot be handled by some
 broken SSL implementations.  This option has no effect for connections
 using other ciphers.
 
+=item SSL_OP_TLSEXT_PADDING
+
+Adds a padding extension to ensure the ClientHello size is never between
+256 and 511 bytes in length. This is needed as a workaround for some
+implementations.
+
 =item SSL_OP_ALL
 
 All of the above bug workarounds.

ssl/ssl.h

@@ -662,7 +662,7 @@ struct ssl_session_st
 /* Allow initial connection to servers that don't support RI */
 #define SSL_OP_LEGACY_SERVER_CONNECT			0x00000004L
 #define SSL_OP_NETSCAPE_REUSE_CIPHER_CHANGE_BUG		0x00000008L
-#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG		0x00000010L
+#define SSL_OP_TLSEXT_PADDING				0x00000010L
 #define SSL_OP_MICROSOFT_BIG_SSLV3_BUFFER		0x00000020L
 #define SSL_OP_SAFARI_ECDHE_ECDSA_BUG			0x00000040L
 #define SSL_OP_SSLEAY_080_CLIENT_DH_BUG			0x00000080L
@@ -671,6 +671,8 @@ struct ssl_session_st
 
 /* Hasn't done anything since OpenSSL 0.9.7h, retained for compatibility */
 #define SSL_OP_MSIE_SSLV2_RSA_PADDING			0x0
+/* Refers to ancient SSLREF and SSLv2, retained for compatibility */
+#define SSL_OP_SSLREF2_REUSE_CERT_TYPE_BUG		0x0
 
 /* Disable SSL 3.0/TLS 1.0 CBC vulnerability workaround that was added
  * in OpenSSL 0.9.6d.  Usually (depending on the application protocol)

ssl/t1_lib.c

@@ -1508,35 +1508,36 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned cha
 	s2n(TLSEXT_TYPE_encrypt_then_mac,ret);
 	s2n(0,ret);
 #endif
-#ifdef TLSEXT_TYPE_padding
+
 	/* Add padding to workaround bugs in F5 terminators.
 	 * See https://tools.ietf.org/html/draft-agl-tls-padding-03
 	 *
 	 * NB: because this code works out the length of all existing
 	 * extensions it MUST always appear last.
 	 */
-	{
-	int hlen = ret - (unsigned char *)s->init_buf->data;
-	/* The code in s23_clnt.c to build ClientHello messages includes the
-	 * 5-byte record header in the buffer, while the code in s3_clnt.c does
-	 * not. */
-	if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
-		hlen -= 5;
-	if (hlen > 0xff && hlen < 0x200)
-		{
-		hlen = 0x200 - hlen;
-		if (hlen >= 4)
-			hlen -= 4;
-		else
-			hlen = 0;
+	if (s->options & SSL_OP_TLSEXT_PADDING)
+		{
+		int hlen = ret - (unsigned char *)s->init_buf->data;
+		/* The code in s23_clnt.c to build ClientHello messages
+		 * includes the 5-byte record header in the buffer, while
+		 * the code in s3_clnt.c does not.
+		 */
+		if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
+			hlen -= 5;
+		if (hlen > 0xff && hlen < 0x200)
+			{
+			hlen = 0x200 - hlen;
+			if (hlen >= 4)
+				hlen -= 4;
+			else
+				hlen = 0;
 
-		s2n(TLSEXT_TYPE_padding, ret);
-		s2n(hlen, ret);
-		memset(ret, 0, hlen);
-		ret += hlen;
+			s2n(TLSEXT_TYPE_padding, ret);
+			s2n(hlen, ret);
+			memset(ret, 0, hlen);
+			ret += hlen;
+			}
 		}
-	}
-#endif
 
 	if ((extdatalen = ret-p-2) == 0)
 		return p;